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Adaptational responses in dynamic stability during disturbed walking in the elderly
2010-01-01
The purpose of this study was to examine the age-related predictive and feedback adaptive locomotor improvements in the components of dynamic stability control during disturbed walking. Thirteen old (62–74yrs) and ten young (23–30yrs) male subjects performed a gait protocol on a gangway, which included one covered element. By exchanging this element, the subjects walked either solely over hard surface or experienced a perturbation of the gait on the soft surface element. The gait protocol consisted of a baseline on hard surface and an adaptation phase with 19 trials on soft or hard (2nd, 8th and 19th) surface. The investigation of dynamic stability was made by using the margin of stability (MS), which was calculated as the difference between the base of support and the extr...
2010-01-01
Increased boot shaft stiffness may have a noticeable impact on the range of motion of the ankle joint. Therefore, the ability of the ankle joint to generate power for propulsion might be impaired. This might result in compensatory changes at the knee and hip joint. Besides, adaptability of the subtalar joint to uneven surface might be reduced, which could in turn affect stability. The aim of the study was therefore to investigate the influence of boot shaft stiffness on biomechanical gait parameters. Fifteen healthy young adults walked over coarse gravel wearing two different hiking boots that differed by 50% in passive shaft stiffness. Leg kinematics, kinetics and electromyography were measured. Gait velocity and indicators for stability were not different when walking with the hard and s...
2010-01-01
The purpose of this study is to develop an abnormal gait detection algorithm and a vibratory stimulation system on a lower limb to improve gait stability and prevent falls. The system consists of a gait measurement module, an abnormal gait detection module, and a vibratory stimulation module. The gait measurement module measures the vertical acceleration of the ankle during walking using an accelerometer. The measured acceleration values are sent to a portable microcontroller, which controls vibratory stimulations to the ankles based on an algorithm that detects the peak acceleration values. If the acceleration peaks are found to occur irregularly, the abnormal gait detection algorithm activates the vibratory stimulation module. To determine the effect of vibratory stimulations under dynam...
Independent influence of gait speed and step length on stability and fall risk
2010-01-01
With aging, individuals' gaits become slower and their steps shorter; both are thought to improve stability against balance threats. Recent studies have shown that shorter step lengths, which bring the center of mass (COM) closer to the leading foot, improve stability against slip-related falls. However, a slower gait, hence lower COM velocity, does the opposite. Due to the inherent coupling of step length and speed in spontaneous gait, the extent to which the benefit of shorter steps can offset the slower speed is unknown. The purpose of this study was to investigate, through decoupling, the independent effects of gait speed and step length on gait stability and the likelihood of slip-induced falls. Fifty-seven young adults walked at one of three target gait patterns, two of equal speed a...
2009-01-01
The ankle-foot orthosis (AFO) with oil damper, GaitSolution (GS), was previously developed to make heel rocker function possible during the gait of hemiplegic patients. To clarify the characteristics of patients who show adaptation to GS use, a questionnaire was completed by the clinicians responsible for 99 patients with hemiplegia who participated in this study. Clinicians completed items concerning gait data of patients without AFO use and with GS use, adaptation to the use of GS, and patient opinion of GS use. Approximately 60% of patients achieved heel rocker function during the loading response of the paretic limb and improved gait when using GS. A comparison of the patients whose gaits were improved by GS more than by other AFOs revealed the use of GS was well suited to the gait of ...
2010-01-01
Many 4-DOF exoskeleton type robot devices have been widely developed for the gait rehabilitation of post-stroke patients. However, most systems run with purely position control not allowing voluntary active movements of the subject. The lack of intelligent control strategies for variable gait patterns has been a clinical concern of such kind exoskeleton man-machine systems. In this work, we establish a 5-link model for the usual 4-DOF gait rehabilitation exoskeleton type man-machine system and propose a gait trajectory adaption control strategy. A 4-DOF gait rehabilitation exoskeleton prototype is developed as a platform for the evaluation of design concepts and control strategies in the view of improved physical human-robot interaction. The experimental results with eight healthy voluntee...
2009-01-01
Postural instability is a sign of progression of Parkinsons disease (PD) and often resistant to levodopa treatment. To explore the effect of bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) on postural stability and gait, full body gait analyses were performed without medication, OFF and ON DBS in eight PD patients and 12 healthy age-matched controls. DBS setting was changed at least 3 hours before gait analysis. To describe asymmetry most and least affected sides (MAS and LAS) were rated with the Unified Parkinsons Disease Rating Scale, motor part and quantitative gait analysis with the Vicon 612 gait analysis system. Stride length and gait velocity but not cadence improved ON DBS. The distances between the heel markers and center of mass (COM) were asymmetric and r...
A study of the passive gait of a compass-like biped robot: Symmetry and chaos
1998-01-01
The focus of this work is a systematic study of the passive gait of a compass-like planar, biped robot on inclined slopes. The robot is kinematically equivalent to a double pendulum, possessing two kneeless legs with point masses and a third point mass at the hip joint. Three parameters, namely, the ground-slope angle and the normalized mass and length of the robot describe its gait. The authors show that in response to a continuous change in any one of its parameters, the symmetric and steady stable gait of the unpowered robot gradually evolves through a regime of bifurcations characterized by progressively complicated asymmetric gaits, eventually arriving at an apparently chaotic gait where not two steps are identical. The robot can maintain this gait indefinitely. A necessary (but not sufficient) condition for the stability of such gaits is the contraction of the phase-fluid ...
Adaptational responses in dynamic stability during disturbed walking in the elderly.
The purpose of this study was to examine the age-related predictive and feedback adaptive locomotor improvements in the components of dynamic stability control during disturbed walking. Thirteen old (62-74 yrs) and ten young (23-30 yrs) male subjects performed a gait protocol on a gangway, which included one covered element. By exchanging this element, the subjects walked either solely over hard surface or experienced a perturbation of the gait on the soft surface element. The gait protocol consisted of a baseline on hard surface and an adaptation phase with 19 trials on soft or hard (2nd, 8th and 19th) surface. The investigation of dynamic stability was made by using the margin of stability (MS), which was calculated as the difference between the base of support and the extrapolated center of mass (CM). Horizontal velocity of CM and its vertical projection in anterior-posterior direction as well as the eigenfrequency of an inverted pendulum generate the extrapolated CM. As a result of the first unexpected disturbance, MS was decreased in the step following the perturbation compared to baselines in both age-groups. This decrease was higher for the old participants compared to the young ones, indicating a more unstable position in the step after the perturbation for the elderly. In the following adaptation phase, MS returned to baseline values in both age-groups. In the hard trial after the first unexpected perturbation, both age-groups increased MS at touchdown of the disturbed leg compared to baseline, reflecting fast predictive adjustments. Our findings show that the well-known age-related biological impairments did not inhibit the adaptive improvements in the components of dynamic stability in the elderly. However, the feedback corrections after the first unexpected perturbation were less effective for the elderly. This may increase the risk of falling.
Center of percussion and gait design of biped robots
2010-01-01
In this paper a novel gait generation technique is proposed, whose objective is to optimize the mechanical design of actuated bipeds in order to reduce energy consumption. The novelty is the use of the center of percussion of the robot to calculate the equivalent simple pendulum of the system. With the equivalent pendulum, the gait is parameterized using its natural frequency. The advantage of this technique is the possibility to assess the influence of the mass and inertia properties of a biped robot on the gait. Therefore, an intelligent design of the kinematic chain can be made using the equivalence developed here. In addition, the method is a new option to linearize biped systems. Control is achieved by designing an adaptive PD controller for gait generation. This algorithm is applied ...
A novel gait analysis system based on adaptive neuro-fuzzy inference system
2010-01-01
In this paper, a novel analysis system based on adaptive neuro-fuzzy inference system (ANFIS), which combined the neural network capabilities and fuzzy logic qualitative approaches, was proposed for gait analysis. A practical clinical problem of pes cavus and pes planus classification was used as an example to explain the principal and process of the system. The system was evaluated in terms of training performance and classification accuracies, and the results showed it is high-efficient and is reliable in gait analysis.
2010-01-01
Can the center of mass (COM) motion state, i.e., its position and velocity relative to the base of support (BOS), which dictate gait stability, be predictably controlled by the global gait parameters of step length and gait speed, or by extension, cadence? The precise relationships among step length and gait speed, and the COM motion state are unknown, partially due to the interdependence between step length and gait speed and the difficulty in independent control of both parameters during spontaneous level walking. The purposes of this study were to utilize simultaneous audio-visual cuing to independently manipulate step length and gait speed, and to determine the extent to which the COM position and velocity can be subsequently controlled. Fifty-six young adults were trained at one of th...
Effects of Initial Stance of Quadruped Trotting on Walking Stability
2005-11-18
It is very important for quadruped walking machine to keep its stability in high speed walking. It has been indicated that moment around the supporting diagonal line of quadruped in trotting gait largely influences walking stability. In this paper, moment around the supporting diagonal line of quadruped in trotting gait is modeled and its effects on body attitude are analyzed. The degree of influence varies with different initial stances of quadruped and we get the optimal initial stance of quadruped in trotting gait with maximal walking stability. Simulation results are presented. Keywords: quadruped, trotting, attitude, walking stability.
Development of a Countermeasure to Mitigate Postflight Locomotor Dysfunction
Astronauts returning from space flight experience locomotor dysfunction following their return to Earth. Our laboratory is currently developing a gait adaptability training program that is designed to facilitate ...
The cost of walking downhill: Is the preferred gait energetically optimal?
2010-01-01
Humans tend to prefer walking patterns that minimize energetic cost, but must also maintain stability to avoid falling over. The relative importance of these two goals in determining the preferred gait pattern is not currently clear. We investigated the relationship between energetic cost and stability during downhill walking, a context in which gravitational energy will assist propulsion but may also reduce stability. We hypothesized that humans will not minimize energetic cost when walking downhill, but will instead prefer a gait pattern that increases stability. Simulations of a dynamic walking model were used to determine whether stable downhill gaits could be achieved using a simple control strategy. Experimentally, twelve healthy subjects walked downhill at 1.25m/s (0, 0.05, 0.10, an...
Gait and force analysis of provoked pig gait on clean and fouled rubber mat surfaces
2010-01-01
Materials that increase floor friction forces in absorption of foot pressure could reduce the risk of slipping, i.e. promote walking safety. The effects of fouled rubber mat floor condition on the gait of 10 pigs walking in a curve, using kinematics and kinetics to record gait parameters and slip frequency, are described and compared with clean conditions. Pigs adapted to fouled floor conditions through reduced walking speed (10%), prolonged swing and stance time, and a higher number of 3-limb support phases, but kept stride length and diagonality constant. This adaption produced a threefold reduction in lateral horizontal forces and kept braking and propulsion forces constant, resulting in a constant peak utilised coefficient of friction (UCOF) level in fore limbs but a 31% reduction in U...
BackgroundTo improve design of robotic lower limb exoskeletons for gait rehabilitation, it is critical to identify neural mechanisms that govern locomotor adaptation to robotic assistance....Full Text Available
2007-10-01
Full Text Available.SUMMARYPurposeThe purpose of this study was to identify gait asymmetries during the mid-stance phase of gait among subjects with knee instability (non-copers) after acute anterior cruciate ligament (ACL) rupture.MethodsTwenty-one non-copers with acute, isolated, unilateral ACL injury ambulated at their intentional walking speed as kinetic, kinematic, and EMG data were collected bilaterally. Lower extremity movement patterns and muscle activity were analyzed during the mid-stance and weight acceptance phases of stance.ResultsDuring mid-stance subjects exhibited lower sagittal plane knee excursions and peak knee extension angles, and higher muscle co-contraction on the injured limb compared to the uninjured limb. There was also a lower knee flexion moment at peak knee extension, a trend for the knee contribution to the total support moment to be lower, and a higher ankle contribution to the total support moment on the injured limb in comparison to the uninjured limb. Differences in the magnitude of muscle activity included higher hamstring activity and lower soleus activity on the injured limb compared to the uninjured limb. Changes in quadriceps, soleus, and hamstring muscle activity on the injured limb were identified during weight acceptance that had not previously been reported.ConclusionsSubjects with knee stability after ACL rupture consistently stabilize their knee with a stiffening strategy involving less knee motion and higher muscle contraction. The variable combination of muscle adaptations that produce joint stiffness, and the ability of both the ankle and hip to compensation for lower knee control, indicate the non-coper neuromuscular system may be more malleable than previously believed.
Adaptations of gait and muscle activation in chronic ACL deficiency
2010-01-01
The purpose was to investigate whether deviations in gait parameters or muscular activity patterns can be detected in the injured and healthy leg of chronic ACL-deficient subjects. Sixteen medium-level active chronic ACL-deficient patients classified as copers? (injury duration: 12240months, age 1752years) and 15 healthy subjects (age 2033years) walked at self-selected speed along a 10-m runway with a level force-plate. Gait specific data, ground reaction forces, knee and ankle angles, and EMG were documented. Knee laxity was increased and the functional scores (Lysholm, KOOS) decreased in the ACL- deficient subjects, whereas the Tegner activity level score was normal. Gait speed, stride length and stance time did not differ between ACL-deficient subjects and controls. ...
The authors trained 21 participants by using blocked-and-mixed exposure to right-side slips and then caused them to slip unexpectedly on the untrained left side. Authors retested participants with a right slip and a left slip at 1 week, 2 weeks, 1 month, and 4 months. The authors found that preslip stability on the first untrained left slip improved and was significantly greater than that on the first right slip, which probably contributed to the reduction in incidence of falls from approximately 30% to approximately 10%. Postslip stability and base of support (BOS) slip velocity were similar to those on the first right slip and much lower than those on the last right slip. Increases in pre- and postslip stabilities and BOS slip velocity during the left slip led to reductions in backward balance loss (BLOB) from approximately 95% on initial left slip to approximately 60% and to approximately 25% on the 1st and 3rd retest sessions, respectively. In contrast, BLOB remained at a constant approximately 40% level on the right slip of the same retest sessions. The results indicate a partial immediate transfer and a possible latent transfer.
2009-05-01
Background and Objective: Evidence for specific physical interventions that improve walking symmetry in individuals with hemiparesis poststroke is limited. The aim of this study was to...Full Text Available
Effects of Aging on the Biomechanics of Slips and Falls
2005-01-01
Although much has been learned in recent decades about the deterioration of muscular strength, gait adaptations, and sensory degradation among older adults, little is known about how these intrinsic...Full Text Available
We designed a gait training study that presented combinations of visual flow and support surface manipulations to investigate the response of healthy adults to novel discordant sensorimotor conditions. We aimed to determine ...
We designed a gait training study that presented combinations of visual flow and support surface manipulations to investigate the response of healthy adults to novel discordant sensorimotor conditions. We aimed to determine ...
Full Text Available.BackgroundDuring locomotion, vision is used to perceive environmental obstacles that could potentially threaten stability; locomotor action is then modified to avoid these obstacles. Various factors such as lighting and texture can make these environmental obstacles appear larger or smaller than their actual size. It is unclear if gait is adapted based on the actual or perceived height of these environmental obstacles. The purposes of this study were to determine if visually guided action is scaled to visual perception, and to determine if task experience influenced how action is scaled to perception.Methodology/Principal FindingsParticipants judged the height of two obstacles before and after stepping over each of them 50 times. An illusion made obstacle one appear larger than obstacle two, even though they were identical in size. The influence of task experience was examined by comparing the perception-action relationship during the first five obstacle crossings (1–5) with the last five obstacle crossings (46–50). In the first set of trials, obstacle one was perceived to be 2.0 cm larger than obstacle two and subjects stepped 2.7 cm higher over obstacle one. After walking over the obstacle 50 times, the toe elevation was not different between obstacles, but obstacle one was still perceived as 2.4 cm larger.Conclusions/SignificanceThere was evidence of locomotor adaptation, but no evidence of perceptual adaptation with experience. These findings add to research that demonstrates that while the motor system can be influenced by perception, it can also operate independent of perception.
Jogging Kinematics After Lumbar Paraspinal Muscle Fatigue
2009-01-01
Full Text Available.AbstractContext:Isolated lumbar paraspinal muscle fatigue causes lower extremity and postural control deficits.Objective:To describe the change in body position during gait after fatiguing lumbar extension exercises in persons with recurrent episodes of low back pain compared with healthy controls.Design:Case-control study.Setting:Motion analysis laboratory.Patients or Other Participants:Twenty-five recreationally active participants with a history of recurrent episodes of low back pain, matched by sex, height, and mass with 25 healthy controls.Intervention(s):We measured 3-dimensional lower extremity and trunk kinematics before and after fatiguing isometric lumbar paraspinal exercise.Main Outcome Measure(s):Measurements were taken while participants jogged on a custom-built treadmill surrounded by a 10-camera motion analysis system.Results:Group-by-time interactions were observed for lumbar lordosis and trunk angles (P < .05). A reduced lumbar spine extension angle was noted, reflecting a loss of lordosis and an increase in trunk flexion angle, indicating increased forward trunk lean, in healthy controls after fatiguing lumbar extension exercise. In contrast, persons with a history of recurrent low back pain exhibited a slight increase in spine extension, indicating a slightly more lordotic position of the lumbar spine, and a decrease in trunk flexion angles after fatiguing exercise. Regardless of group, participants experienced, on average, greater peak hip extension after lumbar paraspinal fatigue.Conclusions:Small differences in response may represent a necessary adaptation used by persons with recurrent low back pain to preserve gait function by stabilizing the spine and preventing inappropriate trunk and lumbar spine positioning.
Full Text Available.BackgroundAdapting to external forces during walking has been proposed as a tool to improve locomotion after central nervous system injury. However, sensorimotor integration during walking varies according to the timing in the gait cycle, suggesting that adaptation may also depend on gait phases. In this study, an ElectroHydraulic AFO (EHO) was used to apply forces specifically during mid-stance and push-off to evaluate if feedforward movement control can be adapted in these 2 gait phases.MethodsEleven healthy subjects walked on a treadmill before (3 min), during (5 min) and after (5 min) exposure to 2 force fields applied by the EHO (mid-stance/push-off; ~10 Nm, towards dorsiflexion). To evaluate modifications in feedforward control, strides with no force field ('catch strides') were unexpectedly inserted during the force field walking period.ResultsWhen initially exposed to a mid-stance force field (FF
Postural Control in Multiple Sclerosis: Implications for Fall Prevention
2010-01-01
People with multiple sclerosis (MS) often have poor postural control, which likely underlies their increased risk of falls. Based on several studies of balance and gait in MS, it appears that the primary mechanisms underlying the observed changes are slowed somatosensory conduction and impaired central integration. This review of the published research on balance, gait, and falls in people with MS demonstrates that people with MS have balance impairments characterized by increased sway in quiet stance, delayed responses to postural perturbations, and a reduced ability to move toward their limits of stability. These impairments are likely causes of falls in people with MS and are consistent with the reduced gait speed, as well as decreased stride length, cadence, and joint movement, observe...
2010-01-01
Background Patients with hip osteoarthritis (OA) have muscular weakness, impaired balance, and limp. Deficits in the different limb muscles and their recovery courses are largely unknown, however. We hypothesized that there is persisting muscular weakness in lower limb muscles and an impaired balance and gait 2 years after THA. Patients and methods 20 elderly patients with unilateral OA were assessed before, and 6 and 24 months after surgery for maximal voluntary isometric strength of hip and knee muscles and by gait analysis, postural stability, and clinical scores (HHS, SF-36, EuroQoL). Results Hip muscles showed a remaining 6% weakness compared to the contralateral healthy limb 2 years after THA. Preoperatively and 6 months postoperatively, that deficit was 18% and 12%, respectively. Kn...
Internal forces and moments in the femur of the rat during gait
2010-01-01
The rat is of increasing importance for experimental studies on fracture healing. The healing outcome of long bone fractures is strongly influenced by mechanical factors, such as the interfragmentary movement. This movement depends on the stability of the fracture fixation and the musculoskeletal loads. However, little is known about these loads in rats. The musculoskeletal loads during gait were estimated using an inverse-dynamic musculoskeletal model of the right hindlimb of the rat. This model was based on a micro-CT scan of the lower extremities and an anatomical study using 15 rat cadavers. Kinematics were reconstructed from X-ray movies, taken simultaneously from two perpendicular directions during a gait cycle. The ground reaction forces were taken from the literature. The muscle fo...
Analysis of muscle activity during gait cycle using fuzzy rule-based reasoning
2010-01-01
The purpose of this study was to determine the patterns of muscle activation as outcome measures of the ground reaction forces during normal walking tasks using optical motion analysis capture system, instrumented treadmill and electromyography (EMG), respectively. The recognition of the muscle patterns during gait dynamics offers insight into the control of skeletal position, joint stiffness, vibrations of the soft tissue packages, stability during ground contact, and propulsion for the movement task. Sixteen able-bodied participants were recruited to walk on a dual-belt instrumented treadmill with embedded force plates. A fuzzy rule-based reasoning algorithm for recognizing the activation patterns of the lower extremity muscles during normal walking maneuvers within the seven gait phases...
Kinematic adaptations to ischemic pain in claudicants during continuous walking
2010-01-01
Intermittent claudication has been associated with impaired gait and balance. The study aim was to compare gait adaptations over time between claudicants classified with good versus poor balance. Kinematic data were collected from 24 claudicants during continuous walking. Balance was assessed using; Timed Up and Go test (TUG), and Sensory Organisation (SOT) and Motor Control (MCT) Tests using NeuroCom Equitest. 'Good balance' (GB) was operationally defined as those claudicants achieving normal scores on at least 2 of 3 tests whereas 'poor balance' (PB) claudicants achieved normal scores on 0 or 1 test. Temporal-spatial and sagittal plane joint kinematics were analysed at three time intervals; 'no pain' (prior to onset), 'initial pain' and 'maximal pain' (unable to continue walking). A two-...
Walking in simulated Martian gravity: Influence of added weight on sagittal dynamic stability
2010-01-01
With human exploration of the Moon and Mars on the horizon, research considerations for space suit redesign have surfaced. Review of Apollo mission videos revealed repeated instance of falling during extravehicular activities. A better understanding of how suit weight influences the sagittal dynamic stability of the gait pattern may provide insight for new suit design such that space missions may have more productive extravehicular activities and smaller risk of falls that may cause injuries and damage equipment. Participants walked for 4min in simulated Martian gravity with additional loads of 0%, 15%, 30% and 45% of their body weight. Floquet and Lyapunov analysis techniques were used to quantify the dynamic stability of the sagittal plane gait pattern. Additionally, sagittal plane joint...
2009-08-25
The purpose of this study was to determine whether stability and limb support play a similar role in governing slip outcome in gait-slip as in sit-to-stand-slip, and whether such prediction...Full Text Available
2010-01-01
Williams SB, Brand CA, Hill KD, Hunt SB, Moran H. Feasibility and outcomes of a home-based exercise program on improving balance and gait stability in women with lower-limb osteoarthritis or rheumatoid arthritis: a pilot study. Objective To evaluate the feasibility and gait stability and balance outcomes of a 4-month individualized home exercise program for women with arthritis. Design Pre-post interventional study. Setting General community. Participants Women (N=49) (volunteers) with lower-limb osteoarthritis or lower-limb rheumatoid arthritis were enrolled. Only 39 subjects were eligible and completed the study. Intervention After completion of the initial assessment, all participants received home balance exercises from an experienced physiotherapist based on assessment findings and ex...
Asymptotically Stable Walking of a Five-Link Underactuated 3D Bipedal Robot
2010-02-18
This paper presents three feedback controllers that achieve an asymptotically stable, periodic, and fast walking gait for a 3D (spatial) bipedal robot consisting of a torso, two legs, and passive (unactuated) point feet. The contact between the robot and the walking surface is assumed to inhibit yaw rotation. The studied robot has 8 DOF in the single support phase and 6 actuators. The interest of studying robots with point feet is that the robot's natural dynamics must be explicitly taken into account to achieve balance while walking. We use an extension of the method of virtual constraints and hybrid zero dynamics, in order to simultaneously compute a periodic orbit and an autonomous feedback controller that realizes the orbit. This method allows the computations to be carried out on a 2-DOF subsystem of the 8-DOF robot model. The stability of the walking gait under closed-loop control is evaluated with the linearization of the restricted Poincar\\'e map of the hybrid zero dynamics. Three strategies are explored. The first strategy consists of imposing a stability condition during the search of a periodic gait by optimization. The second strategy uses an event-based controller. In the third approach, the effect of output selection is discussed and a pertinent choice of outputs is proposed, leading to stabilization without the use of a supplemental event-based controller.
2010-01-01
Background: The dynamics behavior of patients with idiopathic scoliosis obviously requires some biomechanical compensatory strategies. Our objective is to analyze the ground reaction forces (GRF) exerted during gait initiation in order to determine the dynamic consequences of idiopathic scoliosis. Methods: Ten adolescent girls suffering from idiopathic scoliosis with a right thoracic curvature (Cobb
2009-01-01
Purpose. Angelman syndrome (AS) accounts for upto 6% of all cases with severe mental retardation and epilepsy. Clinical findings include developmental delay, severely impaired expressive language, ataxic gait, tremulousness of limbs and a typical behavioral profile including a happy demeanour, hyperactive behavior and low attention span. Seizures, abnormal electroencephalogram, microcephaly and scoliosis are observed in
Peripheral arterial disease (PAD) is a chronic arterial occlusive disease of the lower extremities caused by atherosclerosis. The most common presenting symptom of PAD is intermittent claudication (IC) with exercise induced pain experienced in the calves, thighs or buttocks that is relieved with rest. Research investigating the effects of PAD-IC on lower limb mobility is limited to five studies on the temporal-spatial gait parameters (e.g. stride length, cadence, support times, speed) in PAD-IC populations that produced conflicting results. Gardner et al. (2001) speculated that the temporal-spatial gait parameters of individuals with PAD-IC could be improved by participation in exercise programs. To date there has been no attempt to determine the validity of this proposition. There has also been no research on the underlying mechanism of these temporal-spatial gait parameters namely gait kinematics (angular joint displacement, velocity and acceleration). Observed limitations in temporal-spatial gait parameters may be explained by the effects of musculoskeletal abnormalities on lower limb joint kinematics during the gait cycle. Understanding of the relationships between temporal-spatial gait parameters and gait kinematics in PAD-IC allows more precise identification of gait abnormality and its effects on lower limb mobility in this population. Analysis of variability in gait kinematics is becoming more commonly used as a clinical tool for evaluation of lower limb mobility in the elderly, lower limb disease populations and individual responses to exercise programs. Increased movement variability in lower limb kinematics has been traditionally associated with decreased movement performance due to disease and aging. However, more recent research from a dynamical systems perspective has indicated that movement variability may be of functional importance in motor control and may provide flexibility when adjusting to movement constraints imposed by disease. Therefore, for the purposes of this thesis, a series of studies were undertaken to investigate 1) the temporal-spatial gait parameters, gait kinematics, lower limb movement variability, walking performance, physiological responses to exercise and physical activity levels of individuals with and without PAD-IC and 2) the effects of a long term exercise program on these same variables in individuals with PAD-IC compared to individuals with and without PAD-IC. Study 1 (Chapter 3) examined the lower limb mobility characteristics (temporal-spatial gait parameters and gait kinematics) of individuals with PAD-IC and the relationships between lower limb mobility, walking performance, physiological responses to exercise and physical activity levels in this population. Study 2 (Chapters 4 & 5) assessed intralimb joint coordination and single joint movement variability in patients with PAD-IC and without PAD-IC (CON). Lower limb mobility characteristics were determined via 2D motion analysis. A graded treadmill test was used to assess walking performance (pain free walking distance/time (PFWD/T) and maximal walking distance/time (MWD/T) and peak physiological responses to exercise (VO2peak, HRpeak, RERpeak and VEpeak). Physical activity levels were measured via a 7 d pedometer recording following motion analysis. Intralimb coordination variability was measured using parameterization, vector coding and normalized root mean square techniques applied to relative motion plots of various joint couplings. Single joint movement variability was measured using spanning set and coefficient of variation. Study 3 (Chapter 6) examined the effects of a 12 mth exercise program on the lower limb mobility of individuals with PAD-IC. A further aim was to examine the extent to which lower limb mobility contributes to long term exercise induced changes in walking performance, peak physiological responses to exercise and physical activity levels in PAD-IC patients. Finally study 4 (Chapter 7) investigated the effects of a 12 mth exercise program on walking performance and lower limb movement variability using intralimb joint coordination and single joint assessment techniques in individuals with and without PAD-IC. Compared to CON, PAD-IC temporal-spatial gait parameters were significantly lower (P < .05), except for single support ipsilateral limb time. PAD-IC participants spent a greater percentage of time in gait support phases, took longer to complete a stride and had reduced stride length and walking speeds during the gait cycle. Participants with PAD-IC joint angular kinematics showed significantly reduced displacement of ankle plantar flexion (P = .017), knee ROM (P = .021) and hip extension (P = .016) compared to the CON participants during the gait cycle. All joint minimum and maximum angular velocities and accelerations, physiological responses to exercise (walking) and physical activity levels were significantly lower for PAD-IC compared to the CON participants. The PAD-IC participants displayed significantly higher levels of lower limb movement variability in all joints when assessed using the intralimb joint coordination and single joint movement variability techniques. The 12 mth exercise program had no significant effect on lower limb mobility, peak physiological responses to exercise or physical activity levels in PAD-IC patients who received normal medical therapy treatment and a 12 mth exercise program (TPAD-IC) compared to PAD-IC patients who received normal medical therapy (CPAD-IC) . However, the TPAD-IC participants demonstrated significantly greater walking performance (171% improvement in PFWT and 120% improvement in MWT) compared with baseline. The 12 mth supervised exercise program made no significant impact on the lower limb movement variability of the TPAD-IC group as determined by either intralimb joint coordination or single joint analysis techniques. The results of these studies show that patients with PAD-IC have reduced lower limb mobility (temporal-spatial gait parameters and gait kinematics) and increased lower limb movement variability. The derived gait kinematics highlighted that the push-off (or toe-off) of the gait cycle in PAD-IC patients is significantly reduced compared to healthy age matched controls. The increased level of lower limb movement variability may be an adaptation to the gradual onset of claudication pain in this population. Patients with PAD-IC also demonstrated reduced walking performance, peak physiological responses to exercise and physical activity levels compared to healthy age matched controls. PAD-IC patients involved in a 12 mth supervised exercise program exhibited no change in lower limb mobility characteristics, physiological responses to exercise or physical activity levels. Gardner et al.’s (2001) speculation that the reduced temporal-spatial gait parameters of PAD-IC patients could be modified to resemble that of age matched controls through the use of an exercise program was not supported by the data. However, a 12 mth supervised exercise program did cause a significant improvement in walking performance in this population sample. It is suggested that the improvement in walking performance may be due at least in part, to adaptation of peripheral physiological mechanisms.
2009-01-01
We present a method for the segmentation of human leg bones and extraction of functional parameters of the femur using MRT images. The novelty consists in the use of dynamic models which will be adapted to the images of individual patients both globally to a whole leg bone and locally to individual parts of a bone. Thresholding and region growing procedures are applied for pre-processing the images. For some parts of bones, for example the femur ball, we use a three dimensional VRML-based (Virtual Reality Modelling Language) femur model as a reference in order to make the segmentation method more robust. Based on the segmentation and the 3D VRML model, we can extract functional (biomechanical) femur parameters which are needed for gait analysis.
Stability and Performance Metrics for Adaptive Flight Control
This paper addresses the problem of verifying adaptive control techniques for enabling safe flight in the presence of adverse conditions. Since the adaptive systems are non-linear by design, the existing ...
Direction-Dependent Control of Balance During Walking and Standing
2009-09-01
Human walking has previously been described as “controlled falling.” Some computational models, however, suggest that gait may also have self-stabilizing aspects requiring little CNS...Full Text Available
2009-01-01
Analysis of the COM or COP movement has been a simplified method to illustrate the balance disorders in static stance and gait, but has its limitation when examined alone. Dynamic stability of 32 children with cerebral palsy (CP) was examined and compared with 10 typically developing (TD) children by measuring the displacement of center of mass (COM) and center of pressure (COP) and their spatial relationship. The children with CP were further divided into two groups based on topographical involvement, hemiplegia (Hemi) and diplegia (Di). The participants walked with their preferred speed at least 5 successful trials on a walkway with two force plates mounted in the middle. An eight-camera motion analysis was used to capture 26 reflective markers secured at the bony landmarks of the partic...
Minimalistic control of biped walking in rough terrain
2010-01-01
Toward our comprehensive understanding of legged locomotion in animals and machines, the compass gait model has been intensively studied for a systematic investigation of complex biped locomotion dynamics. While most of the previous studies focused only on the locomotion on flat surfaces, in this article, we tackle with the problem of bipedal locomotion in rough terrains by using a minimalistic control architecture for the compass gait walking model. This controller utilizes an open-loop sinusoidal oscillation of hip motor, which induces basic walking stability without sensory feedback. A set of simulation analyses show that the underlying mechanism lies in the phase locking? mechanism that compensates phase delays between mechanical dynamics and the open-loop motor oscillation resulting...
Gait and its assessment in psychiatry
Gait reflects all levels of nervous system function. In psychiatry, gait disturbances reflecting cortical and subcortical dysfunction are often seen. Observing spontaneous gait, sometimes augmented...Full Text Available
Kinematic adaptations to ischemic pain in claudicants during continuous walking.
Intermittent claudication has been associated with impaired gait and balance. The study aim was to compare gait adaptations over time between claudicants classified with good versus poor balance. Kinematic data were collected from 24 claudicants during continuous walking. Balance was assessed using; Timed Up and Go test (TUG), and Sensory Organisation (SOT) and Motor Control (MCT) Tests using NeuroCom Equitest. 'Good balance' (GB) was operationally defined as those claudicants achieving normal scores on at least 2 of 3 tests whereas 'poor balance' (PB) claudicants achieved normal scores on 0 or 1 test. Temporal-spatial and sagittal plane joint kinematics were analysed at three time intervals; 'no pain' (prior to onset), 'initial pain' and 'maximal pain' (unable to continue walking). A two-way mixed design ANOVA was performed. Claudicants demonstrated a significant decrease in walking speed, step frequency and increased time in double support (p0.05). There was no significant time and group interaction for any temporal-spatial or kinematic variable except hip flexion. GB claudicants demonstrated increased hip flexion as pain progressed but this adaptive strategy was not seen in PB claudicants. Claudicants make adaptations to walking by slowing (down) when in pain. Differences between GB and PB were not seen in temporal-spatial or ankle, knee and pelvic kinematic gait parameters. However adaptation to pain in GB claudicants involved a hip strategy, not seen in PB claudicants.
1 Introduction 2 Theory and Design Methods Adaptive Flight Control ...
and Navigation Conference later this summer in a pair of sessions entitled Adaptive .... adaptation weights increased the stabilator loop gain and resulted in a stability margin of ... Dynamic Flight Envelope Assessment and Prediction ...
2010-01-01
3D analysis of the gait of children with Duchenne muscular dystrophy (DMD) was the topic of only a few studies and none of these considered the effect of gait velocity on the gait parameters of children with DMD. Gait parameters of 11 children with DMD were compared to those of 14 control children while considering the effect of gait velocity using 3D biomechanical analysis. Kinematic and kinetic gait parameters were measured using an Optotrak motion analysis system and AMTI force plates embedded in the floor. The data profiles of children with DMD walking at natural gait velocity were compared to those of the control children who walked at both natural and slow gait velocities. When both groups walked at similar velocity, children with DMD had higher cadence and shorter step length. They ...
This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on primates (chimpanzees, gorillas, etc.) in the African savannas or grasslands and how they were the first animals in evolutionary history to exhibit bipedalism. Students observe, evaluate, and compare the gaits of humans and primates. They then discuss the possible reasons for such an adaptation. Included are objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.
Least Action Principle in Gait
2009-05-22
We apply the laws of human gait vertical ground reaction force and discover the existence of the phenomenon of least action principle in gait. Using a capacitive mat transducer system, we obtain the variations of human gait vertical ground reaction force and establish a structure equation for the resultant of such a force. Defining the deviation of vertical force as an action function, we observe from our gait optimization analysis the least action principle at half of the stride time. We develop an evaluation index of mechanical energy consumption based upon the least action principle in gait. We conclude that these observations can be employed to enhance the accountability of gait evaluation.
Walking stability in young, old and neuropathic subjects
2002-01-01
This thesis investigates walking patterns in healthy young people and in people with an increased risk of falling, and determines the physiological contributions to walking stability. First, a review of the relevant literature on techniques for assessing walking stability, age-related changes in balance and gait, and the contributions of vision, vestibular function, peripheral sensation and strength was undertaken. In response to a critical analysis of these findings, a new technique and protocol for the assessment of walking stability was developed. This involved measuring and analysing head and pelvis accelerations while subjects walked on a level surface and an irregular surface. Gait patterns were studied in 30 young healthy subjects and two groups known to be at increased risk of falling - 100 subjects over the age of 75, and 30 subjects with diabetic peripheral neuropathy. A series of vision, sensation, strength, reaction time and balance tests were also undertaken to identify subjects??? physiological abilities and risk of falls. Acceleration patterns of the head and pelvis differed according to physiological risk of falling, particularly when walking on the irregular surface. Those with a high risk of falling walked with a reduced velocity, cadence and step length, and exhibited less rhythmic acceleration patterns at the head and pelvis. Gait patterns were significantly associated with leg strength, peripheral sensation and reaction time. It is concluded that subjects with a high physiological risk of falling exhibit characteristic patterns of walking that indicate an impaired ability to control the movement of the pelvis and head, which may predispose to loss of balance. Publisher: Awarded by:University of New South Wales. Physiology Language: EN Rights: Copyright Hylton Menz; http://unsworks.unsw.edu.au/copyright
Microdynamics and Criticality of Adaptive Regulatory Networks
2010-04-23
We present a model of adaptive regulatory networks consisting of a simple biologically motivated rewiring procedure coupled to an elementary stability criterion. The resulting networks exhibit...Full Text Available
Acquisition of gliding skills by Weddell seal (Leptonychotes weddellii) pups during lactation
2010-01-01
Pinnipeds give birth to their pups ashore or on ice and forage in water. Therefore, neonates initially lack the adaptations to sustain prolonged underwater diving activity. Although the physiological development for breath-holding during diving has been investigated in seal pups, little is known about the concurrent development of behavioral adaptations during lactation. In this study, multisensor data loggers were used to record diving behavior and swimming gaits of pre-weaned Weddell seal (Leptonychotes weddellii) pups. Experiments were conducted in 16 pups at the Syowa Station, Antarctica, from November to December 1999 and 2004. Swimming speeds, dive depths and flipper stroking rates were recorded for each individual for about 24h. We found that the glide index during ascending was i...
Effects of footwear on balance and gait in older people
2008-01-01
Although footwear has been recognised as a risk factor for falls in older people, it remains unclear as to which features of shoes are beneficial or detrimental to balance. This project aimed to systematically investigate the effects of common shoe features, namely: an elevated heel, a soft sole, a hard sole, a flared sole, a bevelled heel, a high-collar and a tread sole, on balance and gait in older community-dwelling people. The experimental shoes were compared to standard shoes in three studies examining: (i) standing balance, leaning balance and stepping in 29 older people, (ii) centre of mass (COM)-base of support (BOS) margins, vertical and braking loading rates, and perceived shoe comfort and stability in 11 young and 15 older people walking on even and uneven surfaces, and (iii) temporal-spatial gait variables, pelvis acceleration, and gait termination in 10 young and 26 older people, on level, irregular and wet surfaces. Elevated heel shoes impaired overall performance in functional tests of balance and stepping. They were also perceived as lacking comfort and stability and led to a conservative walking pattern characterised by increased step width and double-support time, reduced braking and vertical loading rates and medio-lateral (ML) pelvis accelerations on various surfaces. Soft sole shoes increased lateral COM-BOS margin and step width, indicating reduced ML walking stability. When wearing these shoes, subjects had longer total stopping times and on the wet surface, smaller step lengths and shoe/floor angles at heel strike, suggesting a potential risk of slipping. When wearing high-collar shoes, subjects had better balance as demonstrated by small but significant increases in lateral COM-BOS margin, double-support time and step width, and decreases in ML pelvis accelerations on varying surfaces and in total stopping time on the wet surface. Shoes with hard, flared or tread soles or a bevelled heel did not affect balance. In conclusion, providing that they are fitted, have adequate fastening and perhaps a slip-resistant sole, shoes with a low square heel, a sole of medium hardness (shore A-40) and a high-collar provide the greatest stability for older people when walking on dry, wet and irregular surfaces. Publisher: Publisher:University of New South Wales. Public Health & Community Medicine Language: EN Rights: http://unsworks.unsw.edu.au/copyright
Falls and gait disorders in geriatric neurology
2010-01-01
Gait disturbances are frequent in older patients and lead to immobility, falls, and increased mortality. In gerontoneurologic patients a higher prevalence of risk factors for gait disturbances and falls has to be attributed due to neurodegenerative diseases, dementia, delirium, or psychotropic medication. The potential of neurological expertise to contribute to the evaluation and treatment of falls and gait disorders in geriatric patients is still not fully exploited. Sometimes a fall can be an index event to the diagnosis of the underlying disorder. This review, therefore, focuses on the relationship between falls, gait, and neurological diagnosis. It helps to find the correct diagnosis of the underlying disease as one major step in the management of gait disorders and fall prevention. Fr...
ADAPTATION AS A FACTOR MODIFYING THE STABILITY OF ENZYMES
MATERIALS PUBLISHED CHIEFLY IN RECENT YEARS ON THE FEATURES OF THE STABILITY OF THERMOPHILIC, HALOPHILIC, AND OTHER ENZYMES ARE SURVEYED. IT HAS RECENTLY BECOME POSSIBLE TO ANALYZE THE QUESTION OF GENETIC CONTROL OF ...
ADAPTATION AS A FACTOR MODIFYING THE STABILITY OF ENZYMES
MATERIALS PUBLISHED CHIEFLY IN RECENT YEARS ON THE FEATURES OF THE STABILITY OF THERMOPHILIC, HALOPHILIC, AND OTHER ENZYMES ARE SURVEYED. IT HAS RECENTLY BECOME POSSIBLE TO ANALYZE THE QUESTION OF GENETIC CONTROL OF ...
Outdoor recognition at a distance by fusing gait and face
2007-01-01
We explore the possibility of using both face and gait in enhancing human recognition at a distance performance in outdoor conditions. Although the individual performance of gait and face based biometrics at a distance under outdoor illumination conditions, walking surface changes, and time variations are poor, we show that recognition performance is significantly enhanced by combination of face and gait. For gait, we present a new recognition scheme that relies on computing distances based on selected, discriminatory, gait stances. Given a gait sequence, covering multiple gait cycles, it identifies the salient stances using a population hidden Markov model (HMM). An averaged representation of the detected silhouettes for these stances are then built using eigenstance shape models. Similar...
Dynamic markers of altered gait rhythm in amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis (ALS) is a disorder marked by loss of motoneurons. We hypothesized that subjects with ALS would have an altered gait rhythm, with an increase in both the magnitude of the ...
Decreased knee adduction moment does not guarantee decreased medial contact force during gait
2010-01-01
Excessive contact force is believed to contribute to the development of medial compartment knee osteoarthritis. The external knee adduction moment (KAM) has been identified as a surrogate measure for medial contact force during gait, with an abnormally large peak value being linked to increased pain and rate of disease progression. This study used in vivo gait data collected from a subject with a force-measuring knee implant to assess whether KAM decreases accurately predict corresponding decreases in medial contact force. Changes in both quantities generated via gait modification were analyzed statistically relative to the subjects normal gait. The two gait modifications were a "medial thrust" gait involving knee medialization during stance phase and a "walking pole" gait involving use of...
A nonlinear dynamical model of human gait
2002-12-09
We present a nonlinear stochastic model of the human gait control system in a variety of gait regimes. The stride interval time series in normal human gait is characterized by slightly multifractal fluctuations. The fractal nature of the fluctuations become more pronounced under both an increase and decrease in the average gait. Moreover, the long-range memory in these fluctuations is lost when the gait is keyed on a metronome. The human locomotion is controlled by a network of neurons capable of producing a correlated syncopated output. The central nervous system is coupled to the motocontrol system, and together they control the locomotion of the gait cycle itself. The metronomic gait is simulated by a forced nonlinear oscillator with a periodic external force associated with the conscious act of walking in a particular way.
Adaptive-impulsive synchronization of uncertain complex dynamical networks
2008-01-01
This Letter studies adaptive-impulsive synchronization of uncertain complex dynamical networks. Based on the stability analysis of impulsive system, several network synchronization criteria for local and global adaptive-impulsive synchronization are established. Numerical example is also given to illustrate the results
Feasible Stability Region in the Frontal Plane During Human Gait
2009-12-01
Full Text Available.The inability to adequately control the motion of the center of mass (COM) in the frontal plane may result in a loss of balance causing a sideways fall during human gait. The primary purposes of this study were (1) to derive the feasible stability region (FSR) in the mediolateral direction, and (2) to compare the FSR with the COM motion state taken from 193 trials among 39 young subjects at liftoff during walking at different speeds. The lower boundary of the FSR was derived, at a given initial COM location, as the minimum rightward COM velocity, at liftoff of the left foot, required to bring the COM into the base of support (BOS), i.e. the right (stance) foot, as the COM velocity diminishes. The upper boundary was derived as the maximum rightward COM velocity, beyond which the left foot must land to the right of the right foot (BOS) in order to prevent a fall. We established a 2-link human model and employed dynamic optimization to estimate these threshold values for velocity. For a range of initial COM positions, simulated annealing algorithm was used to search for the threshold velocity values. Our study quantified the extent to which mediolateral balance can still be maintained without resorting to a crossover step (the left foot lands to the right of the BOS) for balance recovery The derived FSR is in good agreement with our gait experimental results.
2008-01-08
With the aim of producing a stable human-like bipedal gait, a five-link planar walking mechanism was coupled with a central pattern generator (CPG) network, consisting of units based on Matsuoka's half-center oscillator model. As a minimalistic approach to bipedal walking, this type of walking mechanism contains only four actuators (two in the hip joints and two in the knee joints), and is lacking feet and ankles. Firstly, the mechanism was designed and built as a physical simulation programmed from scratch, providing a platform for hand-tuned tests and the creation of a CPG controller by genetic algorithms (GA). The oscillatory characteristics of the CPG network together with its internal connection structure and the feedback pathways from the environment were subject to GA optimization. The approach proved successful and the results were then transferred to a hardware realization of the five-link walking mechanism, to test how well these perform under real-world dynamics. Results suggest that the biologically inspired CPG model is very well suited for controlling legged locomotion, since a diverse manifestation of CPG networks (both with and without external feedback) have been observed to succeed during the course of GA evaluations. Observations also imply that while the CPG mechanism is inherently able to sustain a stable gait, the utilization of feedback pathways makes the gait more human-like and is needed to provide a me ans to adapt to irregularities in the environment.
2010-01-01
The purpose of this study is to describe the effects of trunk stabilization training and locomotor training (LT) using body-weight support on a treadmill (BWST) and overground walking on balance, gait, self-reported function, and trunk muscle performance in an adult with severe ataxia secondary to brain injury. There are no studies on the effectiveness of these combined interventions in persons with ataxia. The subject was a 23-year-old male who had a traumatic brain injury 13 months prior. An A-B-A withdrawal single-system design was used. Outcome measures were Berg Balance Test (BBT), timed unsupported stance, Functional Ambulation Category (FAC), 10-meter walk test (10-MWT), Outpatient Physical Therapy Improvement in Movement Assessment Log (OPTIMAL), transverse abdominis (TrA) thicknes...
Tendon disorders of the foot and ankle, part 3: the posterior tibial tendon.
This article provides a review of posterior tibial tendon pathology and the authors' preferred management. The tibialis posterior musculotendinous unit is the most powerful inverter of the foot and an important dynamic stabilizer of the arch. In the stance phase of the gait cycle, it serves as an initiator of both ankle plantar flexion and subtalar inversion. This creates a rigid midfoot by stabilizing the transverse tarsal joint, and allows for increased power generation by the gastrocsoleus complex through toe-off. Injuries to the posterior tibialis tendon include traumatic laceration and dislocation, as well as tenosynovitis and tendinopathy, which can lead to attenuation and rupture. If these injuries are not addressed, significant clinical deformity and disability can result.
Does betahistine treatment have additional benefits to vestibular rehabilitation?
2010-01-01
The aim of this study was to investigate the effect of high-dose betahistine treatment added to vestibular rehabilitation (VR) on the disability, balance and postural stability in patients with unilateral vestibular disorder. The VR group (group 1, n=24) and the VR+betahistine group (group 2, n=23) were analyzed retrospectively. All patients were evaluated before and after an 8-week customized VR in terms of disability (Dizziness Handicap Inventory, DHI), dynamic balance [Dynamic Gait Index (DGI)] and postural stability (static posturography). In group 1 and group 2, differences between DHI, DGI and falling index score on static posturography before and after the exercise program were significant (pp
A Phase-Dependent Hypothesis for Locomotor Functions of Human Foot Complex
2008-01-01
The human foot is a very complex structure comprising numerous bones, muscles, ligaments and synovial joints. As the only component in contact with the ground, the foot complex delivers a variety of biomechanical functions during human locomotion, e.g. body support and propulsion, stability maintenance and impact absorption. These need the human foot to be rigid and damped to transmit ground reaction forces to the upper body and maintain body stability, and also to be compliant and resilient to moderate risky impacts and save energy. How does the human foot achieve these apparent conflicting functions? In this study, we propose a phase-dependent hypothesis for the overall locomotor functions of the human foot complex based on in-vivo measurements of human natural gait and simulation result...
Design and Construction of a Humanoid Robot Platform for Walking Gait Research
The desire to one day see a robot assistant cleaning our houses or walking our dogs has led to an increased interest into humanoid robotics research, and more specifically humanoid locomotion. At present, due to the high cost of robot platforms, there are only a small number of labs in the world conducting meaningful research on full sized humanoid robots. The existence of a low-cost humanoid platform would pave the way for greater involvement and development in the field of humanoid locomotion. This thesis describes the complete design and construction of an affordable humanoid robot platform for walking gait research, from the mechanical structure and actuator selection, right through to the required electronics and power storage implementation. The software required to operate the robot is discussed, from low-level feedback control through to high-level motion planning. The distributed nature of computational resources employed on this robot is outlined, along with the interaction with the robot’s sensors and actuators. A position based control methodology is proposed and implemented using traditional feedback loops on the robot. Control parameters were initially hand-tuned but subsequently improved via the implementation of an off-line evolutionary algorithm. Shortcomings in the mechanical design limited the success of this control scheme, with significant positional error observed in all joints whilst executing a walking gait. Actuator non-linearities as well as significant flexion in the underlying structure contributed to this positional error. To compensate, a series of adaptive control techniques were in turn amalgamated with the initial control loop in an attempt to ‘learn’ the system dynamics of the robot and provide adequate compensatory signals. These additional control schemes realised a slightly improved level of accuracy in simulation in the joint control space but not enough to compensate for the robot’s significant mechanical flexion. Extensive hand tuning of algorithm parameters and excessive memory requirements prevented their implementation on the real robot. This robot competed at two international robot competitions with acceptable results. In 2002, the robot competed in the Humanoid League of RoboCup02, in Fukuoka, Japan. The robot was the largest competing humanoid by a considerable margin and it achieved a ranking of 7th in both the freestyle and walking distance category, out of the ten humanoids competing. In 2005 the robot competed in the RoboCup competition, this time in Osaka, reaching the semi-finals of the penalty shootout for robots over 650 mm in height. The final robot was capable of rudimentary walking and other simple movements such as penalty shootout soccer skills, validating the structure’s ability to withstand the forces required to execute a walking gait.
The Brain in its Body: Motor Control and Sensing in a Biomechanical Context
2009-10-14
Full Text Available.Although it is widely recognized that adaptive behavior emerges from the ongoing interactions among the nervous system, the body, and the environment, it has only become possible in recent years to experimentally study and to simulate these interacting systems. We briefly review work on molluscan feeding, maintenance of postural control in cats and humans, simulations of locomotion in lamprey, insect, cat and salamander, and active vibrissal sensing in rats to illustrate the insights that can be derived from studies of neural control and sensing within a biomechanical context. These studies illustrate that control may be shared between the nervous system and the periphery, that neural activity organizes degrees of freedom into biomechanically meaningful subsets, that mechanics alone may play crucial roles in enforcing gait patterns, and that mechanics of sensors is crucial for their function.
Obstacle crossing in people with Parkinson's disease: Foot clearance and spatiotemporal deficits
2010-01-01
This study investigates the effects of Parkinson's disease (PD) on foot trajectories and spatiotemporal gait adaptations when approaching and stepping over a ground-based obstacle. Twenty people with mild-moderate PD and 20 age and sex matched controls walked 10 steps at their preferred speed along a walkway and stepped over an obstacle (height 10% of leg lengthx600mmx10mm). Control participants also performed trials at the same speed and step length as their matched PD participant. People with PD approached and stepped over the obstacle slower and with smaller steps, but had a similar foot clearance. Those with PD were also more likely to step on the obstacle because they did not place their foot close enough to the front of the obstacle before crossing it to accommodate for their reduced...
Comparative Biomechanical Analysis of Current Microprocessor-Controlled Prosthetic Knee Joints
2010-01-01
Bellmann M, Schmalz T, Blumentritt S. Comparative biomechanical analysis of current microprocessor-controlled prosthetic knee joints. Objective To investigate and identify functional differences of 4 microprocessor-controlled prosthetic knee joints (C-Leg, Hybrid Knee [also called Energy Knee], Rheo Knee, Adaptive 2). Design Tested situations were walking on level ground, on stairs and ramps; additionally, the fall prevention potentials for each design were examined. The measuring technology used included an optoelectronic camera system combined with 2 forceplates as well as a mobile spiroergometric system. Setting The study was conducted in a gait laboratory. Participants Subjects with unilateral transfemoral amputations (N=9; mobility grade, 3–4; age, 22–49y) were tested. I...
Spatial-temporal parameters of gait in women with fibromyalgia
2009-01-01
The aim of the present study was to determine if there are differences in such parameters among patients affected by fibromyalgia (FM) and healthy subjects and whether the degree of affectation by FM can decrease the gait parameters. We studied 55 women with FM and 44 controls. Gait analysis was performed using an instrumented walkway for measurement of the kinematic parameters of gait (GAITRite system), and patients completed a Spanish version of Fibromyalgia Impact Questionnaire (FIQ). Significant differences (p
Locomotion of bipedal humanoid robots: planning and learning to walk
2007-01-01
Pure reinforcement learning does not scale well to domains with many degrees of freedom and particularly to continuous domains. In this thesis, we introduce a hybrid method in which a symbolic planner constructs all approximate solution to a control problem.. Subsequently, a numerical optimisation algorithm is used to refine the qualitative plan into an operational policy. The method is demonstrated on the problem of learning a stable walking gait for a bipedal robot. The contributions of this thesis are as follows. Firstly, the thesis proposes a novel way to generate gait patterns by using a genetic algorithm to generate walking gaits for a humanoid robot using zero moment point as the stability criterion. This is validated on physical robot. Second, we propose an innovative generic learning method that utilises the trainer's domain knowledge about the task to accelerate learning and extend the capabilities of the learning algorithm. The proposed method, which takes advantage of domain knowledge and combines symbolic planning and learning to accelerate and reduce the search space of the learning problem, is tested on a bipedal humanoid robot learning to walk. Finally, it is shown that the extended capability of the learning algorithm handles high complexity learning tasks in the physical world with experimental verification on a physical robot. Publisher: Awarded by:University of New South Wales. Computer Science & Engineering Language: EN Rights: Copyright Yik Tak Fai.; http://unsworks.unsw.edu.au/copyright
Muscle contributions to support and progression during single-limb stance in crouch gait
2010-01-01
Pathological movement patterns like crouch gait are characterized by abnormal kinematics and muscle activations that alter how muscles support the body weight during walking. Individual muscles are often the target of interventions to improve crouch gait, yet the roles of individual muscles during crouch gait remain unknown. The goal of this study was to examine how muscles contribute to mass center accelerations and joint angular accelerations during single-limb stance in crouch gait, and compare these contributions to unimpaired gait. Subject-specific dynamic simulations were created for ten children who walked in a mild crouch gait and had no previous surgeries. The simulations were analyzed to determine the acceleration of the mass center and angular accelerations of the hip, knee, and...
Meaningful change in measures of gait variability in older adults
2010-01-01
Objectives: Gait variability is an important indicator of impaired mobility in older adults; however, little is known about the meaning of change in gait variability over time. This study estimated clinically meaningful change in measures of gait variability using both distribution- and anchor-based approaches. Design: Community-based observational cohort study. Setting: Bronx County and the research center at Albert Einstein College of Medicine. Participants: Of 1148 participants in the Einstein Aging Study, 241 had quantitative gait assessments in two consecutive years between 2001 and 2005. Measurements: Gait variables were collected using a 12-foot instrumented walkway as participants walked at their normal walking speed. Gait variability was defined as the within-person standard devia...
Gait recognition without subject cooperation
2010-01-01
The strength of gait, compared to other biometrics, is that it does not require cooperative subjects. In previous work gait recognition approaches were evaluated using a gallery set consisting of gait sequences of people under similar covariate conditions (e.g. clothing, surface, carrying, and view conditions). This evaluation procedure, however, implies that the gait data are collected in a cooperative manner so that the covariate conditions are known a priori. In this work, gait recognition approaches are evaluated without the assumption on cooperative subjects, i.e. both the gallery and the probe sets consist of a mixture of gait sequences under different and unknown covariate conditions. The results indicate that the performance of the existing approaches would drop drastically under t...
Gait disturbance associated with white matter changes: A gait analysis and blood flow study
2010-01-01
To clarify the mechanisms underlying gait disturbance secondary to age-related white matter changes (ARWMC), cerebral perfusion was investigated during treadmill walking. Twenty subjects with extensive hyperintensities in the periventricular and deep white matter on T2-weighted magnetic resonance images (MRI) were recruited. The ARWMC subjects were classified into gait-disturbed (GD) and non-GD groups according to clinical criteria. All the subjects underwent gait analyses and cerebral perfusion measurements during both gait and rest by using single photon emission computed tomography. The GD group showed greater double support time/phase and stride width, and slower walking velocity, than the non-GD group. In an analysis of pooled data from all the subjects, gait-induced increases in cere...
Assessing gait impairment following experimental traumatic brain injury in mice
2009-01-01
Although gait disturbance is frequently documented among patients with traumatic brain injury (TBI), gait data from animal models of TBI are lacking. To determine the effect of TBI on gait function in adult mice, we assessed gait changes following unilateral controlled cortical impact (CCI) using a computer-assisted automated gait analysis system. Three days after CCI, intensity, area or width of paw contact were significantly decreased in forepaw(s) while the relative paw placement between the fore and hindpaws altered, suggesting that TBI affected sensorimotor status and reduced interlimb coordination. Similar to TBI patients, CCI decreased gait velocity and stride length, and prolonged stance and swing phase in mice. Following CCI, step pattern was also changed with increasing use in th...
What does autonomic arousal tell us about locomotor learning?
2010-01-01
Walking onto a stationary sled previously experienced as moving induces locomotor aftereffects (LAE, or “broken escalator phenomenon”). This particular form of aftereffect can develop after a single adaptation trial and occurs despite subjects being fully aware that the sled will not move. Here, we investigate whether such strong LAE expression may relate to arousal or fear related to instability during the gait adaptation process. Forty healthy subjects were allocated to three sled velocity groups; SLOW (0.6 m/s), MEDIUM (1.3 m/s), or FAST (2.0 m/s). Subjects walked onto the stationary sled for five trials (BEFORE), then onto the moving sled for 15 trials (adaptation or MOVING trials) and, finally, again onto the stationary sled for five trials (AFTER). Explicit warning rega...
Basic theory of adaptive control. Tekio seigyo no kiso riron
1990-08-10
History of the theory of adaptive control has exceeded 30 years. It is one of the most systematically advanced field among the non-linear control systems. This report introductorily describes the conformity of the identification and the design in the adaptive control putting emphasis on MRAC (Model Conference Adaptive Control). The author expects that this explanation connects to the theoretical development of various control systems having a self adjusting function not only to the adaptive control in a narrow sense. Items described are as follows: Identification. Model reference control. MRAC and stability analysis. Although stability is out of the range of the basis of the modern control, it greatly contributes to the conformity of identification and design. Very important factors in the verification and the procedure of verification of the stability are determination of an estimation model, determination of a control rule and determination of adaptive gain. 15 refs.
Adaptive sliding mode control of chaotic dynamical systems with application to synchronization
2010-01-01
We address the problem of control and synchronization of a class of uncertain chaotic systems. Our approach follows techniques of sliding mode control and adaptive estimation law. The adaptive algorithm is constructed based on the sliding mode control to ensure perfect tracking and synchronization in presence of system uncertainty and external disturbance. Stability of the closed-loop system is proved using Lyapunov stability theory. Our theoretical findings are supported by simulation results.
Multivariable and distributed control of nonlinear chemical processes using adaptive methods
In this work we studied the application of adaptive learning and optimization to chemical process control. The work covered theory as well as practical applications of adaptive and nonlinear control, including multivariable periodic control The main findings were: 1. Linear adaptive control systems may display chaotic behavior. The chaos has small amplitude if the algorithm is properly implemented. 2. Stability theory for nonlinear adaptive control has been developed. 3. Experimental evaluation of predictive control was performed. 4. A theory for periodic control and adaptive periodic control of chemical processes was developed.
Multivariable and distributed control of nonlinear chemical processes using adaptive methods
1988-01-01
In this work we studied the application of adaptive learning and optimization to chemical process control. The work covered theory as well as practical applications of adaptive and nonlinear control, including multivariable periodic control The main findings were: 1. Linear adaptive control systems may display chaotic behavior. The chaos has small amplitude if the algorithm is properly implemented. 2. Stability theory for nonlinear adaptive control has been developed. 3. Experimental evaluation of predictive control was performed. 4. A theory for periodic control and adaptive periodic control of chemical processes was developed.
2008-07-10
This work is devoted to the almost sure stabilization of adaptive control systems that involve an unknown Markov chain. The control system displays continuous dynamics represented by differential equations and discrete events given by a hidden Markov chain. Different from previous work on stabilization of adaptive controlled systems with a hidden Markov chain, where average criteria were considered, this work focuses on the almost sure stabilization or sample path stabilization of the underlying processes. Under simple conditions, it is shown that as long as the feedback controls have linear growth in the continuous component, the resulting process is regular. Moreover, by appropriate choice of the Lyapunov functions, it is shown that the adaptive system is stabilizable almost surely. As a by-product, it is also established that the controlled process is positive recurrent.
The many roles of vision during walking
2010-01-01
Vision can improve bipedal upright stability during standing and locomotion. However, during locomotion, vision supports additional behaviors such as gait cycle modulation, navigation, and obstacle avoidance. Here, we investigate how the multiple roles of vision are reflected in the dynamics of trunk control as the neural control problem changes from a fixed to a moving base of support. Subjects were presented with either low- or high-amplitude broadband visual stimuli during standing posture or while walking on a treadmill at 1km/h and 5km/h. Frequency response functions between visual scene motion (input) and trunk kinematics (output) revealed little or no change in the gain of trunk orientation in the standing posture and walking conditions. However, a dramatic increase in gain was ...
Regions of Attraction for Hybrid Limit Cycles of Walking Robots
2010-10-13
This paper illustrates the application of recent research in region-of-attraction analysis for nonlinear hybrid limit cycles. Three example systems are analyzed in detail: the van der Pol oscillator, the "rimless wheel", and the "compass gait", the latter two being simplified models of underactuated walking robots. The method used involves decomposition of the dynamics about the target cycle into tangential and transverse components, and a search for a Lyapunov function in the transverse dynamics using sum-of-squares analysis (semidefinite programming). Each example illuminates different aspects of the procedure, including optimization of transversal surfaces, the handling of impact maps, optimization of the Lyapunov function, and orbitally-stabilizing control design.
Motor Coordination in Autism Spectrum Disorders: A Synthesis and Meta-Analysis
2010-01-01
Are motor coordination deficits an underlying cardinal feature of Autism Spectrum Disorders (ASD)? Database searches identified 83 ASD studies focused on motor coordination, arm movements, gait, or postural stability deficits. Data extraction involved between-group comparisons for ASD and typically developing controls (N=51). Rigorous meta-analysis techniques including random effects models, forest and funnel plots, I 2, publication bias, fail-safe analysis, and moderator variable analyses determined a significant standardized mean difference effect equal to 1.20 (SE=0.144; pZ=10.49). This large effect indicated substantial motor coordination deficits in the ASD groups across a wide range of behaviors. The current overall findings portray motor coordination deficits as pervas...
Modeling posture-dependent leg actuation in sagittal plane locomotion
2009-01-01
The spring loaded inverted pendulum template has been shown to accurately model the steady locomotion dynamics of a variety of running animals, and has served as the inspiration for an entire class of dynamic running robots. While the template models the leg dynamics by an energy-conserving spring, insects and animals have structures that dissipate, store and produce energy during a stance phase. Recent investigations into the spring-like properties of limbs, as well as animal response to drop-step perturbations, suggest that animals use their legs to manage energy storage and dissipation, and that this management is important for gait stability. In this paper, we extend our previous analysis of control of the spring loaded inverted pendulum template via changes in the leg touch-down angle to include energy variations during the stance phase. Energy variations are ...
Locomotor skills and balance strategies in children with internal rotations of the lower limbs
2008-01-01
The purpose of this study was to investigate the functional effects of a structural deformation, internal rotations (IR) of the lower limbs, on upper body balance strategies used during locomotion in 5-6 year-old and 7-10 year-old children. Balance control was examined in terms of rotation around the longitudinal axis in horizontal plane (yaw) and around the sagittal axis in a frontal plane (roll). Kinematics of foot, pelvis, shoulder, and head rotations were measured with an automatic optical TV image processor and used to calculate angular dispersions and segmental stabilizations. Older children with IR showed a lower gait velocity, particularly in difficult balance conditions than typically developing (TD) children. In younger children, the effect of the local biomechanical deficit rema...
Multiple sclerosis and psychological well-being the role of physical and psychosocial factors
2005-01-01
Multiple sclerosis, (MS), presents affected individuals with an uncertain future, and has broad physical and psychosocial implications for their daily functioning. This study aimed to investigate the psychological well-being of people with MS with an emphasis on positive psychological functioning. It also aimed to extend previous research that suggested reporting perceived benefits during adversity may be indicative of cognitive adaptation. Disease-related variables (mobility, fatigue) and psychosocial factors (optimism, coping) were examined to ascertain the effects of living with MS upon well-being. Well-being was determined using two general measures (The Profile of Mood States (POMS), Shacham, 1983; and the Ryff Psychological Well-being Scale (PWB), Ryff & Keyes, 1995), and Mohr et al.�s (1999) MS psychosocial factors (Demoralization, Deteriorated Relationships, Benefit Finding). Participants were 154 people with MS who were recruited through the MS Societies of Victoria and Tasmania. Results showed participants reported both negative and positive consequences from their MS experiences. Higher levels of Demoralization and Deteriorated Relationships were related to decreased well-being. However, no association was found between Benefit Finding and psychological well-being. Benefit Finding was also unrelated to optimism, and the disease-related variables (mobility, fatigue). Only positive reappraisal coping was predictive of reporting of benefits which lends support to the notion that it is a coping strategy. To examine the effects of mobility the sample was divided into three groups: normal gait, mild gait problems but not using aids and those who require aids for mobility. Significant differences between the mobility groups were found on Demoralization and fatigue levels. As participants� difficulties with mobilisation increased so too did their levels of demoralisation. However, those with mild gait problems reported fatigue levels comparable with those experiencing more complex gait difficulties. No differences were found between the groups on the general psychological measures, which may indicate some form of resilience or psychological adaptation occurring. More generally, results showed that participants who were more optimistic, less fatigued, and used less of particular coping strategies (either less avoidant coping or less blaming self or others) to deal with their MS problems reported higher well-being (less demoralisation, less psychological distress and higher positive functioning). In conclusion, the use of multi-dimensional outcomes enabled a comprehensive examination of well-being and highlighted the effects of specific illness-related factors and coping strategies. As demonstrated in this study, despite the adversity of living with MS, people are able to maintain a healthy sense of self and their relationships, and report benefits from their experiences. Publisher: Swinburne University of Technology. Language: en Rights: http://www.swin.edu.au/); Copyright Christine Healy
Due to a need for improved reliability and performance in aerospace systems, there is increased interest in the use of adaptive control or other nonlinear, time-varying control designs in aerospace ...
Due to a need for improved reliability and performance in aerospace systems, there is increased interest in the use of adaptive control or other nonlinear, time-varying control designs in aerospace vehicles. While such ...
Adaptive optics scanning laser ophthalmoscope for stabilized retinal imaging
2006-04-17
A retinal imaging instrument that integrates adaptive optics (AO), scanning laser ophthalmoscopy (SLO), and retinal tracking components was built and tested. The system uses a Hartmann-Shack...Full Text Available
Upper extremity dynamics during Lofstrand crutch-assisted gait in children with myelomeningocele
2009-01-01
The use of quantitative models for evaluating upper extremity (UE) dynamics in children with myelomeningocele (MM) is limited. A biomechanical model for assessment of UE dynamics during Lofstrand crutch-assisted gait in children with MM is presented. This pediatric model may be a valuable tool for clinicians to characterize crutch-assisted gait, which may advance treatment monitoring, crutch prescription, and rehabilitation planning for children with MM. Nine subjects with L3 or L4 level myelodysplasia (mean+/-S.D. age: 11.1+/-3.8 years) were analyzed during forearm crutch-assisted gait: (1) reciprocal gait and (2) swing-through gait. Three-dimensional (3D) dynamics of the UE were acquired and the Pediatric Outcomes Data Collection Instrument (PODCI) was administered. The goal of this stud...
Strength asymmetry and osteoarthritis risk factors in unilateral trans-tibial, amputee gait
2010-01-01
Persons with a unilateral, trans-tibial amputation have an increased risk of developing osteoarthritis (OA) in the knee of their intact limb. Between-side strength discrepancies observed in individuals with an amputation may indicate overuse of the intact limb and increased osteoarthritis risk; however, the relationship between lower extremity strength and gait mechanics has not been addressed in previous literature. It was hypothesized that amputee subjects' strength and gait would be more asymmetrical than controls, and that strength asymmetry would positively correlate with gait variable asymmetry and intact side gait variables associated with osteoarthritis risk. Eight persons with unilateral, trans-tibial amputation and eight able-bodied control subjects participated. Three gait varia...
2007-09-01
Gait or an individual's manner of walking, is one approach for recognizing people at a distance. Studies in psychophysics and medicine indicate that humans can recognize people by their gait and have found twenty-four different components to gait that taken together make it a unique signature. Besides not requiring close sensor contact, gait also does not necessarily require a cooperative subject. Using video data of people walking in different scenarios and environmental conditions we develop and test an algorithm that uses shape and motion to identify people from their gait. The algorithm uses dynamic time warping to match stored templates against an unknown sequence of silhouettes extracted from a person walking. While results under similar constraints and conditions are very good, the algorithm quickly degrades with varying conditions such as surface and clothing.
Quantity versus quality of gait and quality of life in patients with osteoarthritis
2008-01-01
PurposeThis study investigated the relationship between the quality of life, quality of gait and the quantity of gait in patients with impairments in the lower extremities.MethodsTwenty-six subjects (age 58.6+-13.4 years) suffering from knee or hip osteoarthritis were investigated before implantation of an endoprosthesis. Quality of life was assessed using the SF-36 survey. The quality of gait was assessed with a six camera motion analysis system in combination with two force plates. For evaluation of the quantity of gait, two monitors were applied: (a) the accelerometer-based DynaPort activity monitor measured locomotion and posture for 1 day and (b) The Step-Activity-Monitor, a small microprocessor-operated acceleration sensor, measured the number of gait cycles in 1-min intervals for 1 ...
In vivo tibiofemoral cartilage deformation during the stance phase of gait
2010-01-01
The knowledge of articular cartilage contact biomechanics in the knee joint is important for understanding the joint function and cartilage pathology. However, the in vivo tibiofemoral articular cartilage contact biomechanics during gait remains unknown. The objective of this study was to determine the in vivo tibiofemoral cartilage contact biomechanics during the stance phase of treadmill gait. Eight healthy knees were magnetic resonance (MR) scanned and imaged with a dual fluoroscopic system during gait on a treadmill. The tibia, femur and associated cartilage were constructed from the MR images and combined with the dual fluoroscopic images to determine in vivo cartilage contact deformation during the stance phase of gait. Throughout the stance phase of gait, the magnitude of peak compa...
Effect of walking speed and severity of hip osteoarthritis on gait variability
2010-01-01
Gait analysis in orthopaedic and neurological examinations is important; however, few studies assess gait variability at different walking speeds in patients with varying degrees of hip osteoarthritis. We aimed to clarify (1) how different controlled speeds and (2) various severities of hip osteoarthritis influence gait variability. Gait variability was described by the standard deviation (SD) of the spatial-temporal and mean standard deviation (MeanSD) of angular parameters. The spatial positions of the anatomical points for calculating gait parameters were determined in 20 healthy elderly controls and 20 patients with moderate and 20 patients with severe hip osteoarthritis with a zebris CMS-HS ultrasound-based motion analysis system at three walking speeds. The SD of the spatial-temporal...
2010-01-01
Aging is associated with a reduction in several functions including gait. The preservation of gait is important in order to prevent falls and consequent injury as one gets older. Poorer gait may also be an important marker for health status and a determinant of quality of life in later life. It is now recognized that specific regions of the brain such as the frontal motor, prefrontal and parietal cortices, the basal ganglia and cerebellum play an important role in the initiation, planning, execution and maintenance of gait, in tandem with other neuromuscular factors. Aging and age-related disease may affect areas of the brain that are involved in the regulation of gait. Recent technological advances in brain imaging have enabled the identification of age-related changes occurring in the br...
2010-01-01
Monitoring the activity of broilers is a potential way for determining gait score level at commercial farms. In this study, a fully automatic monitoring technique was developed to measure the activity of broiler chickens with different gait score levels. We carried out two experiments in order to assess the relationship between gait scores obtained by human experts and activity levels quantified by an automatic image monitoring system. The chickens were scored for their degree of lameness by experts according to the method of Kestin et al. (1992). For each experiment, a total of 30 birds, on day 32 were selected from a local commercial farm. Five birds were selected in each of six gait score groups (GS0-GS5). The activity levels were obtained for all gait scores by using an automatic image...
2009-01-01
Strategies to design reduced-order adaptive controllers using only part of the system states for the stabilization of one chaotic system and the synchronization of two chaotic systems are proposed for a general class of chaotic systems. Compared with those existed results, the adaptive controllers presented in this paper can globally exponentially stabilize the chaotic systems and can globally exponentially synchronize the two chaotic systems under certain conditions, and therefore can improve the convergence rate of the control processes. Simulation results also verify the effectiveness of the proposed control schemes
Dynamic Stability of the Upper Body During Walking
2006-01-01
The general purpose of this study was to examine factors that may influence acceleration characteristics of the upper body during walking, thereby clarifying the means by which the postural system facilitates dynamic stability of the upper body during walking. Upper body accelerations were measured during a range of straight-line walking tasks. Time domain, frequency domain, signal regularity and coupling analyses were used to 1) provide new insight into gait-related upper body accelerations during walking in normal healthy adults, and 2) determine how the postural system accommodates to perturbations that challenge upper body stability during walking. The specific perturbations to the postural system that were examined in the present study were the normal ageing process, changes in walking speed, and fatigue of the cervical and lumbar erector spinae. In general, the patterns of accelerations measured at the level of the head were an attenuated version of those at the lower trunk during normal walking. Power spectral analysis revealed that both the head and lower trunk in the anterior-posterior (AP) and vertical directions (VT) directions were characterised by a single peak frequency corresponding the step frequency during normal walking. However, the most notable of all attenuation profiles was the difference between accelerations of the head and lower trunk in the mediolateral (ML) direction. ML trunk accelerations were characterised by multiple low amplitude frequency peaks, which were attenuated to a single peak at the head corresponding to stride frequency. The coupling between acceleration directions was greater for the head than the lower trunk, suggesting that the postural system promotes a coordination strategy which enhances global stability of the head. Subdividing the upper body into neck and trunk segments facilitated a more comprehensive description how the gait-related oscillations are prevented from impacting on the motion of the head. Overall, acceleration amplitude, power content, and regularity were predominantly regulated by the trunk segment, especially for the AP and ML directions. This suggests that the trunk segment plays a critical role in modulating the amplitude and structure of gait-related oscillations prior to reaching the neck segment and thus the head. It was envisaged that examining factors that may challenge the individual (the normal ageing process), and the walking task (changes in walking speed, and induced fatigue of the upper body), would provide new insight into the extent to which the postural system prioritises head stability during walking. Regardless of the challenges imposed on the postural system due to the ageing process, upper body movement was organised in a manner which assisted in maintaining a degree of head stability comparable to those observed under normal walking conditions. Similarly, the importance that the postural system places on maintaining head stability was evident in the attenuation characteristics of the trunk and neck segments when walking speed was manipulated, and neuromuscular fatigue induced. Manipulating walking speed highlighted the critical role that the trunk segment has in regulating upper body accelerations arising from gait-related events. Aside from a minor contribution from the neck segment in the direction of travel at preferred and fast walking speeds, regulation of accelerations occurred due to the dynamics of the trunk segment. Inducing neuromuscular fatigue of the cervical and lumbar erector spinae groups (CES and LES) revealed compensatory movement strategies of the upper body, with a view of enhancing head stability. For several variables quantifying attenuation, fatiguing one muscle group, such as the CES, resulted in changes in the dynamics of another level of the upper body, such as the trunk segment. The trunk segment was particularly dominant in regulating upper body accelerations under fatigued conditions, further reinforcing the importance to control accelerations prior to reaching the neck and head. Overall, the results of this study suggest that optimal head stability is reliant on the trunk segment providing a stable base of support for the neck and head. By regulating accelerations via the trunk segment, the postural system is effectively regulating the orientation of the neck and head, and the inclusive sensory organs. It was evident that the postural system prioritises, and in general, maintains head stability during walking despite challenges imposed on upper body stability. Publisher: Griffith University. School of Physiotherapy and Exercise Science Language: en Rights: http://www.gu.edu.au/disclaimer.html); Copyright Justin Kavanagh
Postural stability of biped robots and the foot-rotation indicator (FRI) point
1999-06-01
The focus of this paper is the problem of foot rotation in biped robots during the single-support phase. Foot rotation is an indication of postural instability, which should be carefully treated in a dynamically stable walk and avoided altogether in a statically stable walk. The author introduces the foot-rotation indicator (FRI) point, which is a point on the foot/ground-contact surface where the net ground-reaction force would have to act to keep the foot stationary. To ensure no foot rotation, the FRI point must remain within the convex hull of the foot-support area. In contrast with the ground projection of the center of mass (GCoM), which is a static criterion, the FRI point incorporates robot dynamics. As opposed to the center of pressure (CoP) -- better known as the zero-moment point (ZMP) in the robotics literature -- which may not leave the support area, the FRI point may leave the area. In fact, the position of the FRI point outside the footprint indicates the direction of the impending rotation and the magnitude of rotational moment acting on the foot. Owing to these important properties, the FRI point helps not only to monitor the state of postural stability of a biped robot during the entire gait cycle, but indicates the severity of instability of the gait as well. In response to a recent need, the paper also resolves the misconceptions surrounding the CoP/ZMP equivalence.
Anti-synchronization of chaotic systems with uncertain parameters via adaptive control
2009-01-01
In this Letter, an adaptive control scheme is developed to study the anti-synchronization behavior between two identical and different chaotic systems with unknown parameters. This adaptive anti-synchronization controller is designed based on Lyapunov stability theory and an analytic expression of the controller with its adaptive laws of parameters is shown. The adaptive anti-synchronization between two identical systems (Chen system) and different systems (Genesio and Lue systems) are taken as two illustrative examples to show the effectiveness of the proposed method. Theoretical analysis and numerical simulations are shown to verify the results
Adaptive fuzzy decentralized control for interconnected MIMO nonlinear subsystems
2009-01-01
This paper describes an adaptive fuzzy control strategy for decentralized control for a class of interconnected nonlinear systems with MIMO subsystems. An adaptive robust tracking control schemes based on fuzzy basis function approach is developed such that all the states and signals are bounded. In addition, each subsystem is able to adaptively compensate for disturbances and interconnections with unknown bounds. The resultant adaptive fuzzy decentralized control with multi-controller architecture guarantees stability and convergence of the output errors to zero asymptotically by local output-feedback. An extensive application example of a three-machine power system is discussed in detail to verify the effectiveness of the proposed algorithm.
Adaptive fuzzy bilinear observer based synchronization design for generalized Lorenz system
2009-01-01
This Letter proposes an adaptive fuzzy bilinear observer (FBO) based synchronization design for generalized Lorenz system (GLS). The GLS can be described to TS fuzzy bilinear generalized Lorenz model (FBGLM) with their states immeasurable and their parameters unknown. We design an adaptive FBO based on TS FBGLM for synchronization. Lyapunov theory is employed to guarantee the stability of error dynamic system via linear matrix equalities (LMIs) and to derive the adaptive laws to estimate unknown parameters. Numerical example is given to demonstrate the validity of our proposed adaptive FBO approach for synchronization
Adaptive control: Stability, convergence, and robustness
... the global stability of indirect AC schemes, multivariable AC, linearizing AC for a class of nonlinear systems, AC of linearizable minimum-phase systems, and MIMO systems decouplable by static state feedback.
Tipsheet: Focus on gait training, pain relief, pressure ulcers and hearing aid training
2006-10-11
The current issue of the Journal of Rehabilitation Research and Development focuses on articles involving gait training, caregiver distress, pain relief, total hip arthroplasty, pressure ulcers, integrated prosthetics, ...
Regular Gaits and Optimal Velocities for Motor Proteins
2008-09-15
It has been observed in numerical experiments that adding a cargo to a motor protein can regularize its gait. Here we explain these results via asymptotic analysis on a general stochastic motor protein...Full Text Available
Increased gait unsteadiness in community-dwelling elderly fallers
OBJECTIVE: To test the hypothesis that quantitative measures of gait unsteadiness are increased in community-dwelling elderly fallers. STUDY DESIGN: Retrospective, case-control study. SETTING: General community. ...
Gait analysis to classify external load conditions using linear discriminant analysis
2009-04-01
There are many instances where it is desirable to determine, at a distance, whether a subject is carrying a hidden load. Automated detection systems based on gait analysis have been proposed...Full Text Available
Effects of Spaceflight and Hindlimb Suspension on the Posture and Gait of Rats
Instability of posture and gait in astronauts following spaceflight (SF) is thought to result from muscle atrophy and from changes in sensory-motor integration in the CNS (central nervous system) that occur during ...
Effects of Spaceflight and Hindlimb Suspension on the Posture and Gait of Rats
Instability of posture and gait in astronauts following spaceflight (SF) is thought to result from muscle atrophy and from changes in sensory-motor integration in the CNS (central nervous system) that occur during ...
Cholinergic mesencephalic neurons are involved in gait and postural disorders in Parkinson disease
2010-08-02
Gait disorders and postural instability, which are commonly observed in elderly patients with Parkinson disease (PD), respond poorly to dopaminergic agents used to treat other parkinsonian symptoms....Full Text Available
Damping inter-area modes of oscillation using an adaptive fuzzy power system stabilizer
2010-01-01
This paper introduces an indirect adaptive fuzzy controller as a power system stabilizer used to damp inter-area modes of oscillation following disturbances in power systems. Compared to the IEEE standard multi-band power system stabilizer (MB-PSS), indirect adaptive fuzzy-based stabilizers are more efficient because they can cope with oscillations at different operating points. A nominal model of the power system is identified on-line using a variable structure identifier. A feedback linearization-based control law is implemented using the identified model. The gains of the controller are tuned via a particle swarm optimization routine to ensure system stability and minimum sum of the squares of the speed deviations. A bench-mark problem of a 4-machine 2-area power system is used to demon...
An adaptive stabilizer for thyristor controlled static VAR compensators for power systems
A static VAR systems play an important role as a stability aid for small signal and transient disturbances in an interconnected power system. Further the introduction of an adaptive stabilizer loop to its controller can significantly improve power system performance under a variety of abnormal situations such as 3-phase short-circuits, voltage collapse, load shedding, reactance switching, etc. This paper presents the analytical development of a new controller scheme for a static VAR system and presents detailed simulation results to highlight its effectiveness in comparison with a discrete PI stabilizer under a variety of operating conditions for power transmission systems. The adaptive stabilizer is suitable for microprocessor digital implementation as the numerical steps involved are minimal.
An adaptive stabilizer for thyristor controlled static VAR compensators for power systems
1989-05-01
A static VAR systems play an important role as a stability aid for small signal and transient disturbances in an interconnected power system. Further the introduction of an adaptive stabilizer loop to its controller can significantly improve power system performance under a variety of abnormal situations such as 3-phase short-circuits, voltage collapse, load shedding, reactance switching, etc. This paper presents the analytical development of a new controller scheme for a static VAR system and presents detailed simulation results to highlight its effectiveness in comparison with a discrete PI stabilizer under a variety of operating conditions for power transmission systems. The adaptive stabilizer is suitable for microprocessor digital implementation as the numerical steps involved are minimal.
Power system stabilizers based on modern control techniques
1994-12-31
Developments in digital technology have made it feasible to develop and implement improved controllers based on sophisticated control techniques. Power system stabilizers based on adaptive control, fuzzy logic and artificial networks are being developed. Each of these control techniques possesses unique features and strengths. In this paper, the relative performance of power systems stabilizers based on adaptive control, fuzzy logic and neural network, both in simulation studies and real time tests on a physical model of a power system, is presented and compared to that of a fixed parameter conventional power system stabilizer. (author) 16 refs., 45 figs., 3 tabs.
Energetics of terrestrial locomotion of the platypus Ornithorhynchus anatinus
2001-01-01
© Company of BiologistsThe platypus Ornithorhynchus anatinus Shaw displays specializations in its limb structure for swimming that could negatively affect its terrestrial locomotion. Platypuses walked on a treadmill at speeds of 0.19-1.08 m x s(-1). Video recordings were used for gait analysis, and the metabolic rate of terrestrial locomotion was studied by measuring oxygen consumption. Platypuses used walking gaits (duty factor >0.50) with a sprawled stance. To limit any potential interference from the extensive webbing on the forefeet, platypuses walk on their knuckles. Metabolic rate increased linearly over a 2.4-fold range with increasing walking speed in a manner similar to that of terrestrial mammals, but was low as a result of the relatively low standard metabolic rate of this monotreme. The dimensionless cost of transport decreased with increasing speed to a minimum of 0.79. Compared with the cost of transport for swimming, the metabolic cost for terrestrial locomotion was 2.1 times greater. This difference suggests that the platypus may pay a price in terrestrial locomotion by being more aquatically adapted than other semi-aquatic or terrestrial mammals.F.E. Fish, P.B. Frappell, R.V. Baudinette and P.M. MacFarlane Publisher: The Company of Biologists Ltd Other identifier: Journal of Experimental Biology, 2001; 204(4):797-803; 0022-0949; 0020010578 Language: en_US Source: http://jeb.biologists.org/cgi/content/abstract/204/4/797
2005-07-01
Scientific documentation of neurologic improvement following carotid endarterectomy (CEA) has not been established. The purpose of this prospective study is to investigate whether CEA performed for the internal carotid artery flow lesion improves gait and cerebrovascular hemodynamic status in patients with gait disturbance. We prospectively performed pre- and postCEA gait analysis and acetazolamide stress brain perfusion SPECT (Acz-SPECT) with Tc-99m ECD in 91 patients (M/F: 81/10, mean age: 64.1 y) who had gait disturbance before receiving CEA. Gait performance was assessed using a Vicon 370 motion analyzer. The gait improvement after CEA was correlated to cerebrovascular hemodynamic change as well as symptom duration. 12 hemiparetic stroke patients (M/F=9/3, mean age: 51 y) who did not receive CEA as a control underwent gait analysis twice in a week interval to evaluate whether repeat testing of gait performance shows learning effect. Of 91 patients, 73 (80%) patients showed gait improvement (change of gait speed > 10%) and 42 (46%) showed marked improvement (change of gait speed > 20%), but no improvement was observed in control group at repeat test. Post-operative cerebrovascular hemodynamic improvement was noted in 49 (54%) of 91 patients. There was marked gait improvement in patients group with cerebrovascular hemodynamic improvement compared to no change group (p<0.05). Marked gait improvement and cerebrovascular hemodynamic improvement were noted in 53% and 61% of the patient who had less than 3 month history of symptom compared to 31% and 24% of the patients who had longer than 3 months, respectively (p<0.05). Marked gait improvement was obtained in patients who had improvement of cerebrovascular hemodynamic status on Acz-SPECT after CEA. These results suggest functional improvement such as gait can result from the improved perfusion of misery perfusion area, which is viable for a longer period compared to literatures previously reported.
Composite adaptive control for EulerLagrange systems with additive disturbances
2010-01-01
In a typical adaptive update law, the rate of adaptation is generally a function of the state feedback error. Ideally, the adaptive update law would also include some feedback of the parameter estimation error. The desire to include some measurable form of the parameter estimation error in the adaptation law resulted in the development of composite adaptive update laws that are functions of a prediction error and the state feedback. In all previous composite adaptive controllers, the formulation of the prediction error is predicated on the critical assumption that the system uncertainty is linear in the uncertain parameters (LP uncertainty). The presence of additive disturbances that are not LP would destroy the prediction error formulation and stability analysis arguments in previous resu...
Vestibular rehabilitation and 6-month follow-up using objective and subjective measures.
CONCLUSIONS: Vestibular rehabilitation improves quality of life by reducing the degree of handicap, improving the ability to perform everyday tasks and providing long-term rehabilitation stability (at 6 months). Recovery of the vestibulo-ocular reflex and the vestibulo-spinal reflex efficiency was proven by the objective results obtained in this study. Vestibular rehabilitation improves both subjective and objective parameters, although no significant correlation between these two indices was found. OBJECTIVE: To determine the outcome of subjective and objective parameters and long-term rehabilitation stability after vestibular rehabilitation in 43 patients with vestibular disorders. MATERIAL AND METHODS: The subjective tests used were the Medical Outcomes Study 36-item Short Form, the Dizziness Handicap Inventory and the Activity-specific Balance Confidence scale. The objective tests used were video-oculoscopy, dynamic visual acuity, the Equitest and the Dynamic Gait Index. All indices were evaluated before and after rehabilitation and at follow-up. RESULTS: All patients showed an improvement in quality of life and a reduction in handicap due to dizziness. Improvement in objective test results was also seen. These results were stable at follow-up. A correlation was found between different subjective measures, but there was no correlation between subjective and objective measures.
Stabilizing periodic orbits of chaotic systems using fuzzy adaptive sliding mode control
2008-01-01
In this paper by using a combination of fuzzy identification and the sliding mode control a fuzzy adaptive sliding mode scheme is designed to stabilize the unstable periodic orbits of chaotic systems. The chaotic system is assumed to have an affine form x(n) = f(X) + g(X)u where f and g are unknown functions. Using only the input-output data obtained from the underlying dynamical system, two fuzzy systems are constructed for identification of f and g. Two distinct methods are utilized for fuzzy modeling, the least squares and the gradient descent techniques. Based on the estimated fuzzy models, an adaptive controller, which works through the sliding mode control, is designed to make the system track the desired unstable periodic orbits. The stability analysis of the overall closed loop system is presented in the paper and the effectiveness of the proposed adaptive ...
Adaptive backstepping control for hybrid excitation synchronous machine with uncertain parameters
2010-01-01
This paper proposes an adaptive backstepping speed controller for a novel hybrid excitation synchronous machine (HESM) with nonlinear coupling and parametric uncertainty. With the proposed adaptive backstepping controller, the speed tracking of the HESM possesses the advantages of good transient control performance and robustness to the parametric uncertainty and load torque disturbance. Stability analysis for the control system is presented theoretically. Simulation results validate the effectiveness of the proposed control scheme.
A stable adaptive synchronization scheme for uncertain chaotic systems via observer
2009-01-01
A novel observer-based adaptive synchronization scheme is presented which is used in a chaos communication system. Also, a new nonlinear stochastic adaptive sliding mode observer is extended to reconstruct the states of the stochastic chaotic transmitter at the receiver. The observer is able to overcome the effect of model and parameters uncertainties as well as transmitter, channel and measurement noises. Moreover, a theorem is presented to prove the stability in probability of the proposed observer using stochastic Lyapunov stability criterion. The time-varying adaptation gains of the observer resulted from the proposed theorem ensure fast convergence of the estimated states. Adaptation gains are bounded and do not have any singularity problem especially when the mean value of the observer states' error. In this paper, the parameters of the transmitter are unknown ...
2010-01-01
Patients with multiple sclerosis (MS) frequently experience poor gait and/or cognitive impairment, even in the early stages of the disease. As gait is often executed simultaneously with different cognitive tasks, it is essential to test gait during a cognitive load. Therefore, the main objective of this study was to assess gait and gait variations while simultaneously performing a cognitive task in patients with a clinically isolated syndrome (CIS) suggestive of MS. Fifty-two CIS patients, aged 33.8+/-0.2 years with an Expanded Disability Status Scale (EDSS) score of 1.7+/-0.2 were included in the study. The control group consisted of 28 age- and gender-matched healthy subjects. Major spatio-temporal parameters were collected via an electronic walkway (GAITRite electronic walkway system). ...
2010-01-01
Measurements of femoral and tibial torsion obtained from radiographs or computed tomographic scans have been used to describe rotational malalignment of the lower extremities and to clarify indications for surgery. A weak relationship between anatomic torsion deformity and the resulting transverse plane gait pattern in patients with cerebral palsy has been described, but the observations have not yet been tested in an able-bodied patient population. We conducted a prospective study to investigate the correlation of femoral torsion and tibial torsion as measured by using computed tomography with transverse plane gait data for patients with rotational malalignment. Twenty-six lower limbs from 26 patients selected for surgery based on gait analysis were evaluated. Calculation of Pearson corre...
2010-01-01
Auditory cueing enhances gait in parkinsonian patients. Our aim was to evaluate its effects on spatiotemporal (stride length, stride time, cadence, gait speed, single and double support duration) kinematic (range of amplitude of the hip, knee and ankle joint angles registered in the sagittal plane) and kinetic (maximal values of the hip and ankle joint power) gait parameters using three-dimensional motion analysis. Eight parkinsonian patients performed 12 walking tests: 3 repetitions of 4 conditions (normal walking, 90, 100, and 110% of the mean cadence at preferred pace cued walking). Subjects were asked to uniform their cadence to the cueing rhythm. In the presence of auditory cues stride length, cadence, gait speed and ratio single/double support duration increased. Range of motion of t...
The location of white matter lesions and gait-A voxel-based study
2010-01-01
Little is known about the influence of cerebral white matter lesion (WML) location on gait. We applied partial least squares regression in brain magnetic resonance imaging scans (n = 385) to evaluate which WML voxel systems were independently associated with a composite gait score and identified affected tracts using a diffusion tensor imaging template. Bilateral frontal and periventricular WML-affected voxels corresponding to major anterior projection fibers (thalamic radiations, corticofugal motor tracts) and adjacent association fibers (corpus callosum, superior fronto-occipital fasciculus, short association fibers) showed the greatest covariance with poorer gait. WMLs probably contribute to age-related gait decline by disconnecting motor networks served by these tracts. ANN NEUROL 2010...
2010-01-01
This paper reviews and summarizes the evidence for important observations of normal and pathological gait and presents an approach to rehabilitation and orthotic management, which is based on the significance of shank and thigh kinematics for standing and gait. It discusses normal gait biomechanics, challenging some traditional beliefs, the interrelationship between segment kinematics, joint kinematics and kinetics and their relationship to orthotic design, alignment and tuning. It proposes a description of four rather than three rockers in gait; a simple categorization of pathological gait based on shank kinematics abnormality; an algorithm for the designing, aligning and tuning of AFO-Footwear Combinations; and an algorithm for determining the sagittal angle of the ankle in an AFO. It re...
Striding Out With Parkinson Disease: Evidence-Based Physical Therapy for Gait Disorders
2010-02-01
Full Text Available.Although Parkinson disease (PD) is common throughout the world, the evidence for physical therapy interventions that enable long-term improvement in walking is still emerging. This article critiques the major physical therapy approaches related to gait rehabilitation in people with PD: compensatory strategies, motor skill learning, management of secondary sequelae, and education to optimize physical activity and reduce falls. The emphasis of this review is on gait specifically, although balance and falls are of direct importance to gait and are addressed in that context. Although the researchers who have provided the evidence for these approaches grounded their studies on different theoretical paradigms, each approach is argued to have a valid place in the comprehensive management of PD generally and of gait in particular. The optimal mix of interventions for each individual varies according to the stage of disease progression and the patient's preferred form of exercise, capacity for learning, and age.
Portable Activity Monitoring System for Temporal Parameters of Gait Cycles
2010-01-01
A portable and wireless activity monitoring system was developed for the estimation of temporal gait parameters. The new system was built using three-axis accelerometers to automatically detect walking steps with various walking speeds. The accuracy of walking step-peak detection algorithm was assessed by using a running machine with variable speeds. To assess the consistency of gait parameter analysis system, estimated parameters, such as heel-contact and toe-off time based on accelerometers and footswitches were compared for consecutive 20 steps from 19 individual healthy subjects. Accelerometers and footswitches had high consistency in the temporal gait parameters. The stance, swing, single-limb support, and double-limb support time of gait cycle revealed ICCs values of 0.95, 0.93, 0.86...
Objective detection of subtle freezing of gait episodes in Parkinsons disease
2010-01-01
Freezing of gait (FOG) is a clinically defined phenomenon of Parkinsons disease (PD). Recent evidence suggests that subtle FOG episodes can be elicited in a gait laboratory using suddenly appearing obstacles during treadmill walking. We evaluated which quantitative gait parameters identify such subtle FOG episodes. We included 10 PD patients with FOG, 10 PD patients without FOG, and 10 controls. Subjects walked on a motorized treadmill while avoiding unexpectedly appearing obstacles. Treadmill walking was videotaped, and FOG episodes were identified by two independent experts. Gait was also analyzed using detailed kinematics. Knee joint signals were processed using time-frequency analysis with combinations of sliding fast Fourier transform and wavelets transform. Twenty FOG episodes occurr...
2010-01-01
In order to gain insight into the function of the extant sloth locomotion and its evolution, we conducted a detailed videoradiographic analysis of two-toed sloth locomotion (Xenarthra: Choloepus didactylus). Both unrestrained as well as steady-state locomotion was analyzed. Spatio-temporal gait parameters, data on interlimb coordination, and limb kinematics are reported. Two-toed sloths displayed great variability in spatio-temporal gait parameters over the observed range of speeds. They increase speed by decreasing the durations of contact and swing phases, as well as by increasing step length. Gait utilization also varies with no strict gait sequence or interlimb timing evident in slow movements, but a tendency to employ diagonal sequence, diagonal couplet gaits in fast movements. In con...
Improvement of gait in a stroke patient. A 7-year longitudinal study
2010-01-01
Purpose. To report on the gait improvement obtained in a stroke patient after applying three treatments for spastic equinus varus foot: botulinum toxin injection (BTI), tibial nerve neurotomy (TNN), and orthopaedic surgery (triple arthrodesis), during a 7-year longitudinal follow-up period. Method. A quantified analysis of a stroke patient's gait was performed on a Gaitrite walking mat before and after applying BTI 3 years, TNN 4 years and orthopaedic surgery 7 years after the stroke. Results. After the three treatments, the spasticity disappeared, the range of ankle motion improved and voluntary command of the tibialis anterior became possible. Upon comparing the gait parameters before treatment and after the three treatments, it was observed that the comfortable gait velocity had increas...
H\\"older exponent spectra for human gait
2002-08-01
The stride interval time series in normal human gait is not strictly constant, but fluctuates from step to step in a complex manner. More precisely, it has been shown that the control process for human gait is a fractal random phenomenon, that is, one with a long-term memory. Herein we study the H\\"older exponent spectra for the slow, normal and fast gaits of 10 young healthy men in both free and metronomically triggered conditions and establish that the stride interval time series is more complex than a monofractal phenomenon. A slightly multifractal and non-stationary time series under the three different gait conditions emerges.
Gait pathology assessed with Gillette Gait Index in patients after CNS tumour treatment
2010-01-01
Brain tumour is the third leading cause of death in children and adolescents younger than 16 years of age. The increasing survival rate of these patients makes their follow-up and quality of life assessment an important task. This study evaluated the gait pathology of the patients after the combined treatment for central nervous system (CNS) tumours. It assessed if the severity of gait deviation depended on the tumour site or age of illness onset. Gait analysis was performed on patients who completed the treatment (neurosurgery, chemo- and radiotherapy) and were disease-free at the time of the study. One hundred and five patients, 42 girls and 63 boys, aged 5-24 years of age, participated in the study. Depending on the location of the tumour, patients were divided into six groups. The Gill...
2009-01-01
Background There is emerging interest in hip abductor function during gait and its potential relationship to knee joint pathology. During gait, the hip abductor muscles are primarily responsible for generating moments of force to control frontal plane movement. The current study investigated the relationship between hip abductor muscle function and frontal plane hip moments of force during gait. Methods Frontal plane hip moments of force and electromyographic features of gluteus medius were measured during walking in 22 healthy individuals. Hip abductor strength, subject anthropometrics and gait velocity were recorded. Multiple regression models were used to evaluate the relationship between the anthropometric, velocity, strength and electromyographic variables and the initial and mid-stan...
Estimation of gait parameters by measuring upper limb-walker interaction forces
2010-01-01
Walkers are designed to assist pathological gait by providing weight support, assisting balance and enhancing rehabilitation, as they rely on user's ability to walk. Nevertheless, it is important to continuously obtain certain gait parameters (i) to characterize gait patterns, (ii) to perform follow up and improve rehabilitation strategies and (iii) to efficiently and safely control the device. Due to usability issues and for a broad analysis of gait, it is essential to design sensor architectures that avoid user preparation or environmental instrumentation. In this paper, we present a measurement system for the precise detection of Heel-Strike (HS) and Toe-Off (TO) and for continuous cadence estimation and tracking based on force interaction between user's upper-body and walker handles. H...
Convergence and Optimality of Adaptive Mixed Finite Element Methods
2010-01-12
The convergence and optimality of adaptive mixed finite element methods for the Poisson equation are established in this paper. The main difficulty for mixed finite element methods is the lack of minimization principle and thus the failure of orthogonality. A quasi-orthogonality property is proved using the fact that the error is orthogonal to the divergence free subspace, while the part of the error that is not divergence free can be bounded by the data oscillation using a discrete stability result. This discrete stability result is also used to get a localized discrete upper bound which is crucial for the proof of the optimality of the adaptive approximation.
Adaptive conventional power system stabilizer based on artificial neural network
1995-12-31
This paper deals with an artificial neural network (ANN) based adaptive conventional power system stabilizer (PSS). The ANN comprises an input layer, a hidden layer and an output layer. The input vector to the ANN comprises real power (P) and reactive power (Q), while the output vector comprises optimum PSS parameters. A systematic approach for generating training set covering wide range of operating conditions, is presented. The ANN has been trained using back-propagation training algorithm. Investigations reveal that the dynamic performance of ANN based adaptive conventional PSS is quite insensitive to wide variations in loading conditions.
Neuropsychophysiological findings in a case of long-standing overt ventriculomegaly (LOVA).
Long-standing overt ventriculomegaly in adults (LOVA) is a clinical entity characterized by chronic hydrocephalus with infant onset, slow evolution and clinical disturbances during adulthood. Few cases are reported in literature describing the evident contrast between the severity of hydrocephalus and the relatively spared neurological functioning and cognitive aspects. The authors describe a 59-year-old man with congenital hydrocephalus complaining of persistent gait impairment. Neurological examination showed a mild paraparesis, severe higher cortical function impairment but relatively sparing of daily living activity. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a very remarkable ventriculomegaly compressing the brain cortex but sparing the cerebellum and the brainstem. Brain Single Photon Emission Computer Tomography (SPECT) showed a prevalent cerebellar perfusion as well. Neuropsychological testing was consistent with severe cognitive deterioration and attention disorders. Language and praxis functions seemed to be preserved. Auditory oddball ERPs (P300) showed morphological abnormalities especially of late components. This case report demonstrates in vivo the level of adaptation to which human brain can reach under chronic mechanic stress conditions. The striking poor cerebral parenchyma representation and the relatively spared language and praxic abilities account for a functional reorganization of residual structures due to the neural plasticity.
2010-01-01
This paper presents the design of a power system stabilizer using decentralized adaptive model following tracking control (DAMFTC) approach to damp oscillations of generators in transient response subjected to uncertainties and generating fault actuators. The power system is represented as a collection of interconnected dynamical subsystems each described by a set of differential/algebraic equations using a clear representation of load voltage magnitude with matched and unmatched time-varying uncertainties. All adaptive learning algorithms in this control system are derived in the sense of Lyapunov stability analysis subject to state errors due to uncertainties and fault section, so that stability and robustness of the closed-loop system are ensured and asymptotic-state tracking can be ach...
A study on the power system stabilizer using discrete-time adaptive sliding mode control
1996-02-01
In this paper the newly developed discrete-time adaptive sliding mode control method is proposed and applied to the power system stabilization problem. In contrast to the conventional continuous-time sliding mode controller, the proposed method is developed in the discrete-time domain and based on the input/output measurements instead of the continuous-time and the full-states feedback, respectively. Because the proposed control method has the adaptivity property in addition to the natural robustness property of the sliding mode control, it is possible to design the power system stabilizer which can overcome both the minor variations of the parameters of the power system and the diverse operating conditions and faults of the power system. Mathematical proof and the various computer simulations are done to verify the performance and stability of the proposed method. (author). 14 refs., 12 figs., 1 tab.
Age-related differences in Tai Chi gait kinematics and leg muscle electromyography: a pilot study.
OBJECTIVE: To compare the biomechanic features of Tai Chi gait by elders with those by young adults, and with those of normative gait. DESIGN: Cross-sectional study. SETTING: Laboratory-based testing. PARTICIPANTS: Young (n=6; 3 women) and old (n=6; 5 women) Tai Chi practitioners. INTERVENTION: All subjects had practiced Tai Chi for at least 4 months. MAIN OUTCOME MEASURES: Spatial, temporal, and leg muscle electromyography during Tai Chi gait and normative gait. RESULTS: The primary age-related differences in Tai Chi gait were during single stance, with elders having significantly shorter single-stance time (-50%), less lateral displacement (-30%), knee flexion (-42%), hip flexion (-39%), activation time in the tibialis anterior (-13%), soleus (-39%), and tensor fascia lata (TFL) (-21%), activation magnitude in the tibialis anterior (-39%), and coactivation time of the tibialis anterior and soleus (-47%). Compared with normative gait, elders during Tai Chi gait had significantly larger knee (139%) and hip (66%) flexions, longer duration (90%-170%) and higher magnitude (200%-400%) of the tibialis anterior, rectus femoris, and TFL muscle activities, and longer duration of coactivation of most leg muscle pairs (130%-380%). CONCLUSIONS: The elders practice Tai Chi gait in higher posture than younger subjects. The Tai Chi gait poses significantly higher challenges to elder's balance and muscular system than does their normative gait.
Dual task interference during gait in patients with unilateral vestibular disorders
Full Text Available.BackgroundVestibular patients show slower and unsteady gait; they have also been shown to need greater cognitive resources when carrying out balance and cognitive dual tasks (DT). This study investigated DT interference during gait in a middle-aged group of subjects with dizziness and unsteadiness after unilateral vestibular neuronitis and in a healthy control group.MethodsFourteen individuals with subacute unilateral vestibular impairment after neuronitis and seventeen healthy subjects performed gait and cognitive tasks in single and DT conditions. A statistical gait analysis system was used and spatio-temporal parameters were considered. The cognitive task, consisting of backward counting by three, was tape recorded and the number of right figures was then calculated.ResultsBoth patients and controls showed a more conservative gait during DT and between groups significant differences were not found. A significant decrease in cognitive performance during DT was found only in the vestibular group.ConclusionsResults suggest that less attentional resources are available during gait in vestibular patients compared to controls, and that a priority is given in keeping up the motor task to the detriment of a decrease of the cognitive performance during DT.
Local Dynamic Stability Assessment of Motion Impaired Elderly Using Electronic Textile Pants
2008-10-01
Full Text Available.A clear association has been demonstrated between gait stability and falls in the elderly. Integration of wearable computing and human dynamic stability measures into home automation systems may help differentiate fall-prone individuals in a residential environment. The objective of the current study was to evaluate the capability of a pair of electronic textile (e-textile) pants system to assess local dynamic stability and to differentiate motion-impaired elderly from their healthy counterparts. A pair of e-textile pants comprised of numerous e-TAGs at locations corresponding to lower extremity joints was developed to collect acceleration, angular velocity and piezoelectric data. Four motion-impaired elderly together with nine healthy individuals (both young and old) participated in treadmill walking with a motion capture system simultaneously collecting kinematic data. Local dynamic stability, characterized by maximum Lyapunov exponent, was computed based on vertical acceleration and angular velocity at lower extremity joints for the measurements from both e-textile and motion capture systems. Results indicated that the motion-impaired elderly had significantly higher maximum Lyapunov exponents (computed from vertical acceleration data) than healthy individuals at the right ankle and hip joints. In addition, maximum Lyapunov exponents assessed by the motion capture system were found to be significantly higher than those assessed by the e-textile system. Despite the difference between these measurement techniques, attaching accelerometers at the ankle and hip joints was shown to be an effective sensor configuration. It was concluded that the e-textile pants system, via dynamic stability assessment, has the potential to identify motion-impaired elderly.
2010-01-01
In this Letter, we investigate function projective synchronization of two-cell quantum-CNN chaotic oscillators using nonlinear adaptive controller. Based on Lyapunov stability theory, the nonlinear adaptive control law is derived to make the state of two chaotic systems function projective synchronized. Two numerical simulations are presented to illustrate the effectiveness of the proposed nonlinear adaptive control scheme, which is more effective than that in previous literature
An adaptive model-free fuzzy controller
2005-01-01
In this paper, we present an adaptive, stable fuzzy controller whose parameters are optimized via a genetic algorithm. The controller model is capable of building itself on the basis of measured plant data and then of adapting to new dynamics. The stability of the overall system, made up of the plant and the controller, is guaranteed by Lyapunov's theory. As a case study, the stable adaptive fuzzy controller is employed to drive the narrow water level of a simulated Steam Generator (SG) to a desired reference trajectory. The numerical results confirm that the controller bears good performances in terms of small oscillations and fast settling time even in presence of external disturbances. (authors)
2009-01-01
This work investigates function projective synchronization of two-cell Quantum-CNN chaotic oscillators using adaptive method. Quantum-CNN oscillators produce nano scale chaotic oscillations under certain conditions. By Lyapunove stability theory, the adaptive control law and the parameter update law are derived to make the state of two chaotic systems function projective synchronized. Numerical simulations are presented to demonstrate the effectiveness of the proposed adaptive controllers
Robust synchronization of drive-response chaotic systems via adaptive sliding mode control
2009-03-15
A robust adaptive sliding control scheme is developed in this study to achieve synchronization for two identical chaotic systems in the presence of uncertain system parameters, external disturbances and nonlinear control inputs. An adaptation algorithm is given based on the Lyapunov stability theory. Using this adaptation technique to estimate the upper-bounds of parameter variation and external disturbance uncertainties, an adaptive sliding mode controller is then constructed without requiring the bounds of parameter and disturbance uncertainties to be known in advance. It is proven that the proposed adaptive sliding mode controller can maintain the existence of sliding mode in finite time in uncertain chaotic systems. Finally, numerical simulations are presented to show the effectiveness of the proposed control scheme.
Robust synchronization of drive-response chaotic systems via adaptive sliding mode control
2009-01-01
A robust adaptive sliding control scheme is developed in this study to achieve synchronization for two identical chaotic systems in the presence of uncertain system parameters, external disturbances and nonlinear control inputs. An adaptation algorithm is given based on the Lyapunov stability theory. Using this adaptation technique to estimate the upper-bounds of parameter variation and external disturbance uncertainties, an adaptive sliding mode controller is then constructed without requiring the bounds of parameter and disturbance uncertainties to be known in advance. It is proven that the proposed adaptive sliding mode controller can maintain the existence of sliding mode in finite time in uncertain chaotic systems. Finally, numerical simulations are presented to show the effectiveness of the proposed control scheme
On the convergence of iterative shrinkage algorithms with adaptive discrepancy terms
2008-01-01
In this paper, the inversion of a linear operator is tackled by a procedure called iterative shrinkage. Iterative shrinkage is a procedure that minimizes a functional balancing quadratic discrepancy terms with lp regularization terms. In this work, we propose to replace the classical quadratic discrepancy terms with adaptive ones. These adaptive terms rely on adapted projections on a suitable basis. Two versions of these adaptive terms are proposed (one with a straightforward use of the projections and the other with relaxed projections) together with iterative algorithms minimizing the obtained functional. We prove the convergence and stability of corresponding algorithms. Moreover we prove that for a straightforward use of these adaptive projections, although the process is consistent, valuable information may be lost, which is not the case with the ...
In this work we studied the application of adaptive learning and optimization to chemical process control. The work covered theory as well as practical applications of adaptive and nonlinear control, including multivariable periodic control The main findings were: 1. Linear adaptive control systems may display chaotic behavior. The chaos has small amplitude if the algorithm is properly implemented. 2. Stability theory for nonlinear adaptive control has been developed. 3. Experimental evaluation of predictive control was performed. 4. A theory for periodic control and adaptive periodic control of chemical processes was developed.
1988-12-31
In this work we studied the application of adaptive learning and optimization to chemical process control. The work covered theory as well as practical applications of adaptive and nonlinear control, including multivariable periodic control The main findings were: 1. Linear adaptive control systems may display chaotic behavior. The chaos has small amplitude if the algorithm is properly implemented. 2. Stability theory for nonlinear adaptive control has been developed. 3. Experimental evaluation of predictive control was performed. 4. A theory for periodic control and adaptive periodic control of chemical processes was developed.
Genetics of thermophilic bacteria. [Bacillus stearothermophilus:a2]
Organisms adapted to high temperature have evolved a variety of unique solutions to the biochemical problems imposed by this environment. Adaptation is commonly used to describe the biochemical properties of organisms which have become adapted to their environment (genetic adaptation). It can also mean the direct response-at the cellular level-of an organism to changes in temperature (physiological adaptation). Thermophilic bacilli (strains of Bacillus stearothermophilus) can exhibit a variety of biochemical adaptations in response to changes in temperature. These include changes in the composition and stability of the membrane, metabolic potential, the transport of amino acids, regulatory mechanisms, ribose methylation of tRNA, protein thermostability, and nutritional requirements. The objectives of the research were to develop efficient and reliable genetic systems to analyze and manipulate B. Stearothermophilus, and to use these systems initiate a biochemical, molecular, and genetic investigations of genes that are required for growth at high temperature.
Genetics of thermophilic bacteria. [Bacillus stearothermophilus:a2]
1991-01-01
Organisms adapted to high temperature have evolved a variety of unique solutions to the biochemical problems imposed by this environment. Adaptation is commonly used to describe the biochemical properties of organisms which have become adapted to their environment (genetic adaptation). It can also mean the direct response-at the cellular level-of an organism to changes in temperature (physiological adaptation). Thermophilic bacilli (strains of Bacillus stearothermophilus) can exhibit a variety of biochemical adaptations in response to changes in temperature. These include changes in the composition and stability of the membrane, metabolic potential, the transport of amino acids, regulatory mechanisms, ribose methylation of tRNA, protein thermostability, and nutritional requirements. The objectives of the research were to develop efficient and reliable genetic systems to analyze and manipulate B. Stearothermophilus, and to use these systems initiate a biochemical, molecular, and genetic investigations of genes that are required for growth at high temperature.
Genetics of thermophilic bacteria. Final progress report, May 1, 1984--April 30, 1991
Organisms adapted to high temperature have evolved a variety of unique solutions to the biochemical problems imposed by this environment. Adaptation is commonly used to describe the biochemical properties of organisms which have become adapted to their environment (genetic adaptation). It can also mean the direct response-at the cellular level-of an organism to changes in temperature (physiological adaptation). Thermophilic bacilli (strains of Bacillus stearothermophilus) can exhibit a variety of biochemical adaptations in response to changes in temperature. These include changes in the composition and stability of the membrane, metabolic potential, the transport of amino acids, regulatory mechanisms, ribose methylation of tRNA, protein thermostability, and nutritional requirements. The objectives of the research were to develop efficient and reliable genetic systems to analyze and manipulate B. Stearothermophilus, and to use these systems initiate a biochemical, molecular, and genetic investigations of genes that are required for growth at high temperature.
Genetics of thermophilic bacteria. Final progress report, May 1, 1984--April 30, 1991
1991-12-31
Organisms adapted to high temperature have evolved a variety of unique solutions to the biochemical problems imposed by this environment. Adaptation is commonly used to describe the biochemical properties of organisms which have become adapted to their environment (genetic adaptation). It can also mean the direct response-at the cellular level-of an organism to changes in temperature (physiological adaptation). Thermophilic bacilli (strains of Bacillus stearothermophilus) can exhibit a variety of biochemical adaptations in response to changes in temperature. These include changes in the composition and stability of the membrane, metabolic potential, the transport of amino acids, regulatory mechanisms, ribose methylation of tRNA, protein thermostability, and nutritional requirements. The objectives of the research were to develop efficient and reliable genetic systems to analyze and manipulate B. Stearothermophilus, and to use these systems initiate a biochemical, molecular, and genetic investigations of genes that are required for growth at high temperature.
An adaptive FEA method to predict surface quality in hard machining
2006-01-01
A significant problem of studying surface integrity using FEA simulation is the severe element distortions on the machined surface. The severe distortions raise significant numerical problems in performing a simulation and analyzing surface integrity. In this study, adaptive meshing techniques of initial angle control (IAC) and mesh constraint control (MCC) were exploited to improve mesh quality of the machined surface. Simulations with and without adaptive meshing and different adaptive techniques were conducted and compared to evaluate their effectiveness on surface mesh quality. The simulation results have shown that the use of adaptive mesh in metal cutting simulations improves the stability of saw-tooth chip formation. Adaptive mesh can significantly mitigate element distortions, stre...
The neuro-muscular and musculo-skeletal characterization of children with joint hypermobility
2009-01-01
In children, joint hypermobility (typified by structural instability of joints) manifests clinically as neuro-muscular and musculo-skeletal conditions and conditions associated with development and organization of control of posture and gait (Finkelstein, 1916; Jahss, 1919; Sobel, 1926; Larsson, Mudholkar, Baum and Srivastava, 1995; Murray and Woo, 2001; Hakim and Grahame, 2003; Adib, Davies, Grahame, Woo and Murray, 2005:). The process of control of the relative proportions of joint mobility and stability, whilst maintaining equilibrium in standing posture and gait, is dependent upon the complex interrelationship between skeletal, muscular and neurological function (Massion, 1998; Gurfinkel, Ivanenko, Levik and Babakova, 1995; Shumway-Cook and Woollacott, 1995). The efficiency of this relies upon the integrity of neuro-muscular and musculo-skeletal components (ligaments, muscles, nerves), and the Central Nervous System’s capacity to interpret, process and integrate sensory information from visual, vestibular and proprioceptive sources (Crotts, Thompson, Nahom, Ryan and Newton, 1996; Riemann, Guskiewicz and Shields, 1999; Schmitz and Arnold, 1998) and development and incorporation of this into a representational scheme (postural reference frame) of body orientation with respect to internal and external environments (Gurfinkel et al., 1995; Roll and Roll, 1988). Sensory information from the base of support (feet) makes significant contribution to the development of reference frameworks (Kavounoudias, Roll and Roll, 1998). Problems with the structure and/ or function of any one, or combination of these components or systems, may result in partial loss of equilibrium and, therefore ineffectiveness or significant reduction in the capacity to interact with the environment, which may result in disability and/ or injury (Crotts et al., 1996; Rozzi, Lephart, Sterner and Kuligowski, 1999b). Whilst literature focusing upon clinical associations between joint hypermobility and conditions requiring therapeutic intervention has been abundant (Crego and Ford, 1952; Powell and Cantab, 1983; Dockery, in Jay, 1999; Grahame, 1971; Childs, 1986; Barton, Bird, Lindsay, Newton and Wright, 1995a; Rozzi, et al., 1999b; Kerr, Macmillan, Uttley and Luqmani, 2000; Grahame, 2001), there has been a deficit in controlled studies in which the neuro-muscular and musculo-skeletal characteristics of children with joint hypermobility have been quantified and considered within the context of organization of postural control in standing balance and gait. This was the aim of this project, undertaken as three studies. The major study (Study One) compared the fundamental neuro-muscular and musculo-skeletal characteristics of 15 children with joint hypermobility, and 15 age (8 and 9 years), gender, height and weight matched non-hypermobile controls. Significant differences were identified between previously undiagnosed hypermobile (n=15) and non-hypermobile children (n=15) in passive joint ranges of motion of the lower limbs and lumbar spine, muscle tone of the lower leg and foot, barefoot CoP displacement and in parameters of barefoot gait. Clinically relevant differences were also noted in barefoot single leg balance time. There were no differences between groups in isometric muscle strength in ankle dorsiflexion, knee flexion or extension. The second comparative study investigated foot morphology in non-weight bearing and weight bearing load conditions of the same children with and without joint hypermobility using three dimensional images (plaster casts) of their feet. The preliminary phase of this study evaluated the casting technique against direct measures of foot length, forefoot width, RCSP and forefoot to rearfoot angle. Results indicated accurate representation of elementary foot morphology within the plaster images. The comparative study examined the between and within group differences in measures of foot length and width, and in measures above the support surface (heel inclination angle, forefoot to rearfoot angle, normalized arch height, height of the widest point of the heel) in the two load conditions. Results of measures from plaster images identified that hypermobile children have different barefoot weight bearing foot morphology above the support surface than non-hypermobile children, despite no differences in measures of foot length or width. Based upon the differences in components of control of posture and gait in the hypermobile group, identified in Study One and Study Two, the final study (Study Three), using the same subjects, tested the immediate effect of specifically designed custom-made foot orthoses upon balance and gait of hypermobile children. The design of the orthoses was evaluated against the direct measures and the measures from plaster images of the feet. This ascertained the differences in morphology of the modified casts used to mould the orthoses and the original image of the foot. The orthoses were fitted into standardized running shoes. The effect of the shoe alone was tested upon the non-hypermobile children as the non-therapeutic equivalent condition. Immediate improvement in balance was noted in single leg stance and CoP displacement in the hypermobile group together with significant immediate improvement in the percentage of gait phases and in the percentage of the gait cycle at which maximum plantar flexion of the ankle occurred in gait. The neuro-muscular and musculo-skeletal characteristics of children with joint hypermobility are different from those of non-hypermobile children. The Beighton, Solomon and Soskolne (1973) screening criteria successfully classified joint hypermobility in children. As a result of this study joint hypermobility has been identified as a variable which must be controlled in studies of foot morphology and function in children. The outcomes of this study provide a basis upon which to further explore the association between joint hypermobility and neuro-muscular and musculo-skeletal conditions, and, have relevance for the physical education of children with joint hypermobility, for footwear and orthotic design processes, and, in particular, for clinical identification and treatment of children with joint hypermobility. Publisher: Queensland University of Technology
Large Field of View, Modular, Stabilized, Adaptive-Optics-Based Scanning Laser Ophthalmoscope
2007-05-01
Full Text Available.We describe the design and performance of an adaptive optics retinal imager that is optimized for use during dynamic correction for eye movements. The system incorporates a retinal tracker and stabilizer, a wide field line scan Scanning Laser Ophthalmocsope (SLO), and a high resolution MEMS based adaptive optics SLO. The detection system incorporates selection and positioning of confocal apertures, allowing measurement of images arising from different portions of the double pass retinal point spread function (psf). System performance was excellent. The adaptive optics increased the brightness and contrast for small confocal apertures by more than 2x, and decreased the brightness of images obtained with displaced apertures, confirming the ability of the adaptive optics system to improve the pointspread function. The retinal image was stabilized to within 18 microns 90% of the time. Stabilization was sufficient for cross-correlation techniques to automatically align the images.
Trend of adaptive control theory. Tekio seigyo riron no doko
1990-08-10
Since the name of adaptive control came up about 25 years ago, it has been actively studied as a control theory which could maintain the desired performances in spite of unknown or uncertain dynamic characteristics of the plant. By 1980, limitation of signals and the asymptotic convergence within the adaptive loop were proven, whereby the adaptive theory in the ideal state was approximately completed. However, in the application to an actual system, owing to the unrealistic condition of the ideal conditions, the reduction of the robustness has been pointed out; presently a study on the robust adaptive control is attracting the attention of the researchers. This report descibes the following items. Key factors of the adaptive control (asymptotic stability of a non-linear systems. Estimation of outline parameters. positive-reality and Kalman-Yakubovich Theorem). Robust adaptive control (Condition and limitation of adaptive control of ideal state. Application of non-minimum phase system and delta-operator). Hybrid adaptive control. 19 refs., 8 figs.
Transistorized ignition with new kind of point-gap control and idling stabilization
1982-08-13
The ignition is adaptable to different transmitter systems. It stabilizes the idling by controlling the firing angle by way of a delay element and produces maximal spark energy in all speed ranges by means of a comparator with a gliding switching threshold. From the idling stabilization it is also possible to derive the thrust cutout and the idling adjustment. The article also looks at operating experience.
Stabilizing periodic orbits of chaotic systems using fuzzy adaptive sliding mode control
2008-08-15
In this paper by using a combination of fuzzy identification and the sliding mode control a fuzzy adaptive sliding mode scheme is designed to stabilize the unstable periodic orbits of chaotic systems. The chaotic system is assumed to have an affine form x{sup (n)} = f(X) + g(X)u where f and g are unknown functions. Using only the input-output data obtained from the underlying dynamical system, two fuzzy systems are constructed for identification of f and g. Two distinct methods are utilized for fuzzy modeling, the least squares and the gradient descent techniques. Based on the estimated fuzzy models, an adaptive controller, which works through the sliding mode control, is designed to make the system track the desired unstable periodic orbits. The stability analysis of the overall closed loop system is presented in the paper and the effectiveness of the proposed adaptive scheme is numerically investigated. As a case of study, modified Duffing system is selected for applying the proposed method to stabilize its 2{pi} and 4{pi} periodic orbits. Simulation results show the high performance of the method for stabilizing the unstable periodic orbits of unknown chaotic systems.
MASA syndrome is caused by mutations in the neural cell adhesion gene, L1CAM
1994-09-01
The MASA syndrome is a recessive X-linked disorder characterized by Mental retardation, Adducted thumbs, Shuffling gait and Aphasia. Recently we found that MASA in one family was likely caused by a point mutation in exon 6 of the L1CAM gene. This gene has also been shown to be involved in X-linked hydrocephalus (HSAS). We have screened 60 patients with either sporadic HSAS or MASA as well as two additional families with MASA. For the screening, we initially utilized 3 cDNA probes for the L1CAM gene. In one of the MASA families, K8310, two affected males were found to have an altered BglII band. The band was present in their carrier mother but not in their normal brothers. This band was detected by the entire cDNA probe as well as the cDNA probe for 3{prime} end of the gene. Analysis of the L1CAM sequence indicated the altered BglII site is distal to the exon 28 but proximal to the punative poly A signal site. It is hypothesized that this point mutation alters the stability of the L1CAM mRNA. This is being tested using cell lines established from the two affected males.
Biologically inspired joint control for a humanoid robot
2004-01-01
The GuRm is a 1.2m tall, 23 degree of freedom humanoid consuucted at the University of Queensland for research into humanoid robotics. The key challenge being addressed by the GuRw projcct is the development of appropriate learning strategies for control and coodinadon of the robot’s many joints. The development of learning strategies is Seen as a way to sidestep the inherent intricacy of modeling a multi-DOP biped robot. This paper outlines the approach taken to generate an appmpria*e control scheme for the joinis of the GuRoo. The paper demonsrrates the determination of local feedback control parameters using a genetic algorithm. The feedback loop is then augmented by a predictive modulator that learns a form of feed-fonward control to overcome the irregular loads experienced at each joint during the gait cycle. The predictive modulator is based on thc CMAC architecture. Results from tats on the GuRoo platform show that both systems provide improvements in stability and tracking of joint control. Publisher: The Institute of Electrical and Electronics Engineers Contributor: G. Cheng; S. Schaal Coverage: 2004-01-01T00:00:00Z
2009-01-01
In this paper, a robust intelligent sliding model control (RISMC) scheme using an adaptive recurrent cerebellar model articulation controller (RCMAC) is developed for a class of uncertain nonlinear chaotic systems. This RISMC system offers a design approach to drive the state trajectory to track a desired trajectory, and it is comprised of an adaptive RCMAC and a robust controller. The adaptive RCMAC is used to mimic an ideal sliding mode control (SMC) due to unknown system dynamics, and a robust controller is designed to recover the residual approximation error for guaranteeing the stable characteristic. Moreover, the Taylor linearization technique is employed to derive the linearized model of the RCMAC. The all adaptation laws of the RISMC system are derived based on the Lyapunov stability analysis and projection algorithm, so that the stability of the system can be ...
2008-01-01
The relationships between structure, activity, stability and flexibility of a cold-adapted aminopeptidase produced by a psychrophilic marine bacterium have been investigated in comparison with a mesophilic structural and functional human homolog. Differential scanning calorimetry, fluorescence monitoring of thermal- and guanidine hydrochloride-induced unfolding and fluorescence quenching were used to show that the cold-adapted enzyme is characterized by a high activity at low temperatures, a low structural stability versus thermal and chemical denaturants and a greater structural permeability to a quenching agent relative to the mesophilic homolog. These findings support the hypothesis that cold-adapted enzymes maintain their activity at low temperatures as a result of increased global or ...
Adaptive prey behavior and the dynamics of intraguild predation systems
2010-01-01
Intraguild predation constitutes a widespread interaction occurring across different taxa, trophic positions and ecosystems, and its endogenous dynamical properties have been shown to affect the abundance and persistence of the involved populations as well as those connected with them within food webs. Although optimal foraging decisions displayed by predators are known to exert a stabilizing influence on the dynamics of intraguild predation systems, few is known about the corresponding influence of adaptive prey decisions in spite of its commonness in nature. In this study, we analyze the effect that adaptive antipredator behavior exerts on the stability and persistence of the populations involved in intraguild predation systems. Our results indicate that adaptive prey behavior in the for...
2008-01-01
People have paid more attention to enhancing voltage stability margin since voltage collapses happened in some power systems recently. This paper proposes an optimal reactive power flow (ORPF) incorporating static voltage stability based on a multi-objective adaptive immune algorithm (MOAIA). The main idea of the proposed algorithm is to add two parts to an existing immune algorithm. The first part defines both partial affinity and global affinity to evaluate the antibody affinity to the multi-objective functions. The second part uses adaptive crossover, mutation and clone rates for antibodies to maintain the antibodies diversity. Hence, the proposed algorithm can achieve a dynamic balance between individual diversity and population convergence. The paper describes ORPF's multi-objective functional mathematical model and the constraint conditions. The ...
Asymptotic stabilization of a nonlinear axially moving string by adaptive boundary control
2010-01-01
In this paper, a robust adaptive boundary control for an axially moving string that shows nonlinear behavior resulting from spatially varying tension is investigated. A hydraulic actuator equipped with a damper is used as the control actuator at the right boundary of the string. The Lyapunov redesign method is employed to derive a robust control algorithm employing adaptation laws that estimate three unknown system parameters (mass per unit length of string, lumped mass of hydraulic actuator, and damping coefficient of damper) and an unknown boundary disturbance. The uniform asymptotic stability (when the three parameters are all unknown), the exponential stability (when they are known), and the uniform ultimate boundedness (with a bounded boundary disturbance) of the closed loop system ar...
2010-01-01
This article presents a new scheme for load curtailment in the power system under critical contingencies that may pose a threat to the frequency and voltage stability of the system. The proposed scheme is based on a two-stage load-shedding strategy. In the first stage, disturbances have been classified based on the computed value of the disturbance power, and the load-shedding requirement in the system has been assessed based on the frequency stability, as well as dynamic voltage stability, conditions. The scheme assumes the availability of real-time data from a synchrophasor-based wide area monitoring and control system. A dynamic voltage stability criterion has been developed in this stage using a voltage stability risk index to assess the voltage stability in real time. Suitable locatio...
2009-10-01
Full Text Available.Thermal adaptation of individual proteins is often achieved through modulating protein stability, with proteins that are adapted to extreme cold environments having increased conformational flexibility when brought to mesophilic conditions. Conversely, proteins adapted to higher temperatures appear less dynamic and are found to be much more stable against thermal denaturation than their mesophilic counterparts. According to the current paradigm, the adaptation of an organism for survival at higher or lower temperatures is facilitated by the adaptation of the component proteins. We note, however, that these observations have been carried out on relatively few proteins. The extent to which the conformational stabilities of all members of the proteome have been modulated for thermal adaptation remains unclear, with no direct experimental strategies to address this issue. Adapted extremophilies are likely to use a multitude of molecular and biophysical strategies for survival and, therefore, evolution of specific biophysical properties of proteins for optimal function may not be necessary for all proteins in the proteome. Using a sequence-based predictor of protein stability, eScape, an in silico examination of several extremophilic proteomes shows a correlation between the collective stability of the proteins and the thermal range of survival for the organism as expected. Unexpectedly, however, the analysis shows that protein thermostability is modified to different extents across the proteome and depends on the functional role for which the protein is involved. Identification of these differences provides unique opportunities to study interdependence within the proteome as well as the role that the proteome plays in the process of evolutionary thermal adaptation.
Do Humans Optimally Exploit Redundancy to Control Step Variability in Walking?
2010-07-01
Full Text Available.It is widely accepted that humans and animals minimize energetic cost while walking. While such principles predict average behavior, they do not explain the variability observed in walking. For robust performance, walking movements must adapt at each step, not just on average. Here, we propose an analytical framework that reconciles issues of optimality, redundancy, and stochasticity. For human treadmill walking, we defined a goal function to formulate a precise mathematical definition of one possible control strategy: maintain constant speed at each stride. We recorded stride times and stride lengths from healthy subjects walking at five speeds. The specified goal function yielded a decomposition of stride-to-stride variations into new gait variables explicitly related to achieving the hypothesized strategy. Subjects exhibited greatly decreased variability for goal-relevant gait fluctuations directly related to achieving this strategy, but far greater variability for goal-irrelevant fluctuations. More importantly, humans immediately corrected goal-relevant deviations at each successive stride, while allowing goal-irrelevant deviations to persist across multiple strides. To demonstrate that this was not the only strategy people could have used to successfully accomplish the task, we created three surrogate data sets. Each tested a specific alternative hypothesis that subjects used a different strategy that made no reference to the hypothesized goal function. Humans did not adopt any of these viable alternative strategies. Finally, we developed a sequence of stochastic control models of stride-to-stride variability for walking, based on the Minimum Intervention Principle. We demonstrate that healthy humans are not precisely “optimal,” but instead consistently slightly over-correct small deviations in walking speed at each stride. Our results reveal a new governing principle for regulating stride-to-stride fluctuations in human walking that acts independently of, but in parallel with, minimizing energetic cost. Thus, humans exploit task redundancies to achieve robust control while minimizing effort and allowing potentially beneficial motor variability.
A pneumatically powered knee-ankle-foot orthosis (KAFO) with myoelectric activation and inhibition
Full Text Available.BackgroundThe goal of this study was to test the mechanical performance of a prototype knee-ankle-foot orthosis (KAFO) powered by artificial pneumatic muscles during human walking. We had previously built a powered ankle-foot orthosis (AFO) and used it effectively in studies on human motor adaptation, locomotion energetics, and gait rehabilitation. Extending the previous AFO to a KAFO presented additional challenges related to the force-length properties of the artificial pneumatic muscles and the presence of multiple antagonistic artificial pneumatic muscle pairs.MethodsThree healthy males were fitted with custom KAFOs equipped with artificial pneumatic muscles to power ankle plantar flexion/dorsiflexion and knee extension/flexion. Subjects walked over ground at 1.25 m/s under four conditions without extensive practice: 1) without wearing the orthosis, 2) wearing the orthosis with artificial muscles turned off, 3) wearing the orthosis activated under direct proportional myoelectric control, and 4) wearing the orthosis activated under proportional myoelectric control with flexor inhibition produced by leg extensor muscle activation. We collected joint kinematics, ground reaction forces, electromyography, and orthosis kinetics.ResultsThe KAFO produced ~22%–33% of the peak knee flexor moment, ~15%–33% of the peak extensor moment, ~42%–46% of the peak plantar flexor moment, and ~83%–129% of the peak dorsiflexor moment during normal walking. With flexor inhibition produced by leg extensor muscle activation, ankle (Pearson r-value = 0.74 ± 0.04) and knee ( r = 0.95 ± 0.04) joint kinematic profiles were more similar to the without orthosis condition compared to when there was no flexor inhibition (r = 0.49 ± 0.13 for ankle, p = 0.05, and r = 0.90 ± 0.03 for knee, p = 0.17).ConclusionThe proportional myoelectric control with flexor inhibition allowed for a more normal gait than direct proportional myoelectric control. The current orthosis design provided knee torques smaller than the ankle torques due to the trade-off in torque and range of motion that occurs with artificial pneumatic muscles. Future KAFO designs could incorporate cams, gears, or different actuators to transmit greater torque to the knee.
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