Validating Determinants for an Alternate Foot Placement Selection Algorithm During Human Locomotion in Cluttered Terrain

2007 ◽  
Vol 98 (4) ◽  
pp. 1928-1940 ◽  
Author(s):  
Renato Moraes ◽  
Fran Allard ◽  
Aftab E. Patla
Keyword(s):  
Dynamic Stability ◽  
Center Of Mass ◽  
Frontal Plane ◽  
Human Locomotion ◽  
The Body ◽  
Selection Algorithm ◽  
Foot Placement ◽  
Double Support ◽  
One Step ◽  
Base Of Support

The goal of this study was to validate dynamic stability and forward progression determinants for the alternate foot placement selection algorithm. Participants were asked to walk on level ground and avoid stepping, when present, on a virtual white planar obstacle. They had a one-step duration to select an alternate foot placement, with the task performed under two conditions: free (participants chose the alternate foot placement that was appropriate) and forced (a green arrow projected over the white planar obstacle cued the alternate foot placement). To validate the dynamic stability determinant, the distance between the extrapolated center of mass (COM) position, which incorporates the dynamics of the body, and the limits of the base of support was calculated in both anteroposterior (AP) and mediolateral (ML) directions in the double support phase. To address the second determinant, COM deviation from straight ahead was measured between adaptive and subsequent steps. The results of this study showed that long and lateral choices were dominant in the free condition, and these adjustments did not compromise stability in both adaptive and subsequent steps compared with the short and medial adjustments, which were infrequent and adversely affected stability. Therefore stability is critical when selecting an alternate foot placement in a cluttered terrain. In addition, changes in the plane of progression resulted in small deviations of COM from the endpoint goal. Forward progression of COM was maintained even for foot placement changes in the frontal plane, validating this determinant as part of the selection algorithm.

scholarly journals Dynamic and static stability in hexapedal runners.

1994 ◽  
Vol 197 (1) ◽  
pp. 251-269 ◽  
Author(s):  
L H Ting ◽  
R Blickhan ◽  
R J Full
Keyword(s):  
Dynamic Stability ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Stability Margin ◽  
Static Stability ◽  
Double Support ◽  
Wide Range ◽  
One Step ◽  
Energy And Momentum ◽  
Base Of Support

Stability is fundamental to the performance of terrestrial locomotion. Running cockroaches met the criteria for static stability over a wide range of speeds, yet several locomotor variables changed in a way that revealed an increase in the importance of dynamic stability as speed increased. Duty factors (the fraction of time that a leg spends on the ground relative to the stride period) decreased to 0.5 and below with an increase in speed. The duration of double support (i.e. when both tripods, or all six legs, were on the ground) decreased significantly with an increase in speed. All legs had similar touch-down phases in the tripod, but the shortest leg, the front one, lifted off before the middle and the rear leg, so that only two legs of the tripod were in contact with the ground at the highest speeds. Per cent stability margin (the shortest distance from the center of gravity to the boundaries of support, normalized to the maximum possible stability margin) decreased with increasing speed from 60% at 10 cms-1 to values less than zero at speeds faster than 50 cms-1, indicating instances of static instability at fast speeds. The center of mass moved rearward or posteriorly with respect to the base of support as speed increased. Moments about the center of mass, as shown by the center of pressure (the equivalent of a single 'effective' leg), were variable, but were balanced by opposing moments over a stride. Thus, hexapods can exploit the advantages of both static and dynamic stability. Static or quasi-static assumptions alone were insufficient to explain straight-ahead, constant-speed locomotion and may hinder discovery of behaviors that are dynamic, where kinetic energy and momentum can act as a bridge from one step to the next.

scholarly journals The critical phase for visual control of human walking over complex terrain

2017 ◽  
Vol 114 (32) ◽  
pp. E6720-E6729 ◽  
Author(s):  
Jonathan Samir Matthis ◽  
Sean L. Barton ◽  
Brett R. Fajen
Keyword(s):  
Complex Terrain ◽  
Visual Information ◽  
Center Of Mass ◽  
Ground Surface ◽  
The Body ◽  
Foot Placement ◽  
Preceding Step ◽  
Control Work ◽  
Base Of Support ◽  
Target Visibility

To walk efficiently over complex terrain, humans must use vision to tailor their gait to the upcoming ground surface without interfering with the exploitation of passive mechanical forces. We propose that walkers use visual information to initialize the mechanical state of the body before the beginning of each step so the resulting ballistic trajectory of the walker’s center-of-mass will facilitate stepping on target footholds. Using a precision stepping task and synchronizing target visibility to the gait cycle, we empirically validated two predictions derived from this strategy: (1) Walkers must have information about upcoming footholds during the second half of the preceding step, and (2) foot placement is guided by information about the position of the target foothold relative to the preceding base of support. We conclude that active and passive modes of control work synergistically to allow walkers to negotiate complex terrain with efficiency, stability, and precision.

scholarly journals Rethinking Margin of Stability: Incorporating Step-To-Step Regulation to Resolve the Paradox

2021 ◽  
Author(s):  
Meghan Kazanski ◽  
Joseph P. Cusumano ◽  
Jonathan B. Dingwell
Keyword(s):  
Inverted Pendulum ◽  
Balance Control ◽  
Center Of Mass ◽  
Frontal Plane ◽  
Lateral Instability ◽  
Foot Placement ◽  
Margin Of Stability ◽  
Increased Risk ◽  
Mediolateral Stability ◽  
Balance Dynamics

ABSTRACTMaintaining frontal-plane stability is a major objective of human walking. Derived from inverted pendulum dynamics, the mediolateral Margin of Stability (MoSML) is frequently used to measure people’s frontal-plane stability on average. However, typical MoSML-based analyses deliver paradoxical interpretations of stability status. To address mediolateral stability using MoSML, we must first resolve this paradox. Here, we developed a novel framework that unifies the well-established inverted pendulum model with Goal-Equivalent Manifold (GEM)-based analyses to assess how humans regulate step-to-step balance dynamics to maintain mediolateral stability. We quantified the extent to which people corrected fluctuations in mediolateral center-of-mass state relative to a MoSML-defined candidate stability GEM in the inverted pendulum phase plane. Participants’ variability and step-to-step correction of tangent and perpendicular deviations from the candidate stability GEM demonstrate that regulation of balance dynamics involves more than simply trying to execute a constant-MoSML balance control strategy. Participants adapted these step-to-step corrections to mediolateral sensory and mechanical perturbations. How participants regulated mediolateral foot placement strongly predicted how they regulated center-of-mass state fluctuations, suggesting that regulation of center-of-mass state occurs as a biomechanical consequence of foot placement regulation. We introduce the Probability of Instability (PoI), a convenient statistic that accounts for step-to-step variance to properly predict instability likelihood on any given future step. Participants increased lateral PoI when destabilized, as expected. These lateral PoI indicated an increased risk of lateral instability, despite larger (i.e., more stable) average MoSML. PoI thereby explicitly predicts instability risk to decisively resolve the existing paradox that arises from conventional MoSML implementations.

scholarly journals The ability to increase the base of support and recover stability is limited in its generalisation for different balance perturbation tasks

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Jil Bosquée ◽  
Julian Werth ◽  
Gaspar Epro ◽  
Thorben Hülsdünker ◽  
Wolfgang Potthast ◽  
...  
Keyword(s):  
Dynamic Stability ◽  
Single Step ◽  
Stability Performance ◽  
Rate Of Increase ◽  
One Step ◽  
Recovery Performance ◽  
The Stability ◽  
Base Of Support ◽  
Age Range ◽  
Induced Trip

Abstract Background The assessment of stability recovery performance following perturbations contributes to the determination of fall resisting skills. This study investigated the association between stability recovery performances in two perturbation tasks (lean-and-release versus tripping). Methods Healthy adults (12 young: 24 ± 3 years; 21 middle-aged: 53 ± 5 years; 11 old: 72 ± 5 years) were suddenly released from a forward-inclined position attempting to recover stability with a single step. In a second task, all participants experienced a mechanically induced trip during treadmill walking. To assess dynamic stability performance, the antero-posterior margin of stability (MoS), the base of support (BoS), and the rate of increase in BoS were determined at each foot touchdown (TD) for both tasks. Results Only weak to moderate correlations in dynamic stability performance parameters were found between the two tasks (0.568 > r > 0.305, 0.001 < p < 0.04). A separation of participants according to the number of steps required to regain stability in the lean-and-release task revealed that multiple- (more than one step) compared to single-steppers showed a significantly lower MoS at TD (p = 0.003; g = 1.151), lower BoS at TD (p = 0.019; g = 0.888) and lower rate of increase in BoS until TD (p = 0.002; g = 1.212) after release. Despite these profound subgroup differences in the lean-and-release task, no differences between multiple- and single-steppers were observed in the stability recovery performance during tripping. Conclusion The results provide evidence that the ability to effectively control dynamic stability following a sudden balance disturbance in adults across a wide age range is limited in its generalisation for different perturbation tasks.

scholarly journals Compliant leg behaviour explains basic dynamics of walking and running

2006 ◽  
Vol 273 (1603) ◽  
pp. 2861-2867 ◽  
Author(s):  
Hartmut Geyer ◽  
Andre Seyfarth ◽  
Reinhard Blickhan
Keyword(s):  
Mechanical System ◽  
Legged Locomotion ◽  
Human Locomotion ◽  
The Body ◽  
Phase Changes ◽  
Vertical Oscillation ◽  
Mass Model ◽  
Double Support ◽  
Walking Motion ◽  
The Many

The basic mechanics of human locomotion are associated with vaulting over stiff legs in walking and rebounding on compliant legs in running. However, while rebounding legs well explain the stance dynamics of running, stiff legs cannot reproduce that of walking. With a simple bipedal spring–mass model, we show that not stiff but compliant legs are essential to obtain the basic walking mechanics; incorporating the double support as an essential part of the walking motion, the model reproduces the characteristic stance dynamics that result in the observed small vertical oscillation of the body and the observed out-of-phase changes in forward kinetic and gravitational potential energies. Exploring the parameter space of this model, we further show that it not only combines the basic dynamics of walking and running in one mechanical system, but also reveals these gaits to be just two out of the many solutions to legged locomotion offered by compliant leg behaviour and accessed by energy or speed.

scholarly journals Body stability and muscle and motor cortex activity during walking with wide stance

2014 ◽  
Vol 112 (3) ◽  
pp. 504-524 ◽  
Author(s):  
Brad J. Farrell ◽  
Margarita A. Bulgakova ◽  
Irina N. Beloozerova ◽  
Mikhail G. Sirota ◽  
Boris I. Prilutsky
Keyword(s):  
Motor Cortex ◽  
Dynamic Stability ◽  
Balance Control ◽  
Discharge Rate ◽  
Three Dimensional ◽  
Forward Direction ◽  
The Body ◽  
Double Support ◽  
Layer V ◽  
Body Dynamic

Biomechanical and neural mechanisms of balance control during walking are still poorly understood. In this study, we examined the body dynamic stability, activity of limb muscles, and activity of motor cortex neurons [primarily pyramidal tract neurons (PTNs)] in the cat during unconstrained walking and walking with a wide base of support (wide-stance walking). By recording three-dimensional full-body kinematics we found for the first time that during unconstrained walking the cat is dynamically unstable in the forward direction during stride phases when only two diagonal limbs support the body. In contrast to standing, an increased lateral between-paw distance during walking dramatically decreased the cat's body dynamic stability in double-support phases and prompted the cat to spend more time in three-legged support phases. Muscles contributing to abduction-adduction actions had higher activity during stance, while flexor muscles had higher activity during swing of wide-stance walking. The overwhelming majority of neurons in layer V of the motor cortex, 82% and 83% in the forelimb and hindlimb representation areas, respectively, were active differently during wide-stance walking compared with unconstrained condition, most often by having a different depth of stride-related frequency modulation along with a different mean discharge rate and/or preferred activity phase. Upon transition from unconstrained to wide-stance walking, proximal limb-related neuronal groups subtly but statistically significantly shifted their activity toward the swing phase, the stride phase where most of body instability occurs during this task. The data suggest that the motor cortex participates in maintenance of body dynamic stability during locomotion.

Postural Stability While Walking and Carrying Loads in Various Postures

1994 ◽  
Vol 38 (10) ◽  
pp. 564-567 ◽  
Author(s):  
M.A. Holbein ◽  
M.S. Redfern
Keyword(s):  
Postural Stability ◽  
Center Of Mass ◽  
Frontal Plane ◽  
The Body ◽  
Limits Of Stability ◽  
Stability Analyses ◽  
Load Carrying ◽  
Mass Displacement ◽  
Stability Issues ◽  
Balance Loss

Falls, over-exertion injuries and other potential consequences of balance losses continue to be serious ergonomic concerns. Stability issues are important in the prevention of these injuries, especially when the task is complicated by handling loads. However, stability analyses are not typical components of ergonomic job analyses. This study demonstrated that stability assessments can be effective in recommending load-carrying strategies. In particular, the effects of load positioning and magnitude on stability were investigated. Unladen walking was also tested for comparison. Several stability measures were defined based on the body-and-load's center of mass displacement in the frontal plane. Statistical differences among the load positions and magnitudes were found and are discussed. Results were consistent across measures. Additional work is needed to better define the limits of stability while carrying and to relate these, or other, stability measures to the likelihood of a balance loss.

Biomechanical Role of the Locomotor System in Controlling Body Center of Mass Motion in Older Adults During Obstructed Gait

2010 ◽  
Vol 26 (2) ◽  
pp. 195-203 ◽  
Author(s):  
T.-M. Wang ◽  
H.-L. Chen ◽  
W.-C. Hsu ◽  
M.-W. Liu ◽  
T.-W. Lu
Keyword(s):  
Center Of Mass ◽  
Three Dimensional ◽  
Knee Extensor ◽  
Frontal Plane ◽  
The Elderly ◽  
The Body ◽  
Mass Motion ◽  
Obstacle Crossing ◽  
Locomotor System ◽  
Risk Of Falls

AbstractFifteen young and fifteen older healthy adults walked and crossed obstacles of three different heights while kinematic data and ground reaction forces were acquired to calculate the three-dimensional motion of the centre of mass (COM) and lower limb joint moments. The older group had greater normalized jerk score of the COM. When the leading limb was crossing, the older group kept the COM more posterior and on the trailing stance limb for longer with increased knee extensor crossing moments and thus decreased anterioposterior COM deceleration. When the trailing limb was crossing, the older group decreased vertical COM deceleration through increased hip extensor crossing moments. The older group maintained the same COM motion as the young in the frontal plane with greater hip and knee abductor crossing moments. The older group exhibited significant kinetic changes in their locomotor system with increased muscular demand, leading to a more jerky motion of the body COM. However, these changes helped to maintain the frontal COM motion and to achieve a sagittal COM motion pattern which is thought to be helpful for a safe and successful obstacle-crossing. Failure to meet the kinetic demands in the elderly may increase the risk of falls during obstacle-crossing.

scholarly journals Stepping in the direction of the fall: the next foot placement can be predicted from current upper body state in steady-state walking

2014 ◽  
Vol 10 (9) ◽  
pp. 20140405 ◽  
Author(s):  
Yang Wang ◽  
Manoj Srinivasan
Keyword(s):  
Steady State ◽  
Linear Function ◽  
Center Of Mass ◽  
Step Length ◽  
The Body ◽  
Upper Body ◽  
Significant Information ◽  
Foot Placement ◽  
Body State ◽  
Foot Position

During human walking, perturbations to the upper body can be partly corrected by placing the foot appropriately on the next step. Here, we infer aspects of such foot placement dynamics using step-to-step variability over hundreds of steps of steady-state walking data. In particular, we infer dependence of the ‘next’ foot position on upper body state at different phases during the ‘current’ step. We show that a linear function of the hip position and velocity state (approximating the body center of mass state) during mid-stance explains over 80% of the next lateral foot position variance, consistent with (but not proving) lateral stabilization using foot placement. This linear function implies that a rightward pelvic deviation during a left stance results in a larger step width and smaller step length than average on the next foot placement. The absolute position on the treadmill does not add significant information about the next foot relative to current stance foot over that already available in the pelvis position and velocity. Such walking dynamics inference with steady-state data may allow diagnostics of stability and inform biomimetic exoskeleton or robot design.

CENTER OF MASS-BASED ADMITTANCE CONTROL FOR MULTI-LEGGED ROBOT WALKING ON THE BOTTOM OF OCEAN

2015 ◽  
Vol 74 (9) ◽  
Author(s):  
Addie Irawan ◽  
Md. Moktadir Alam ◽  
Yee Yin Tan ◽  
Mohd Rizal Arshad
Keyword(s):  
Buoyancy Force ◽  
Center Of Mass ◽  
The Body ◽  
Total Force ◽  
Vertical Force ◽  
Hexapod Robot ◽  
Admittance Control ◽  
Foot Placement ◽  
Robot Locomotion ◽  
Foot Motion

This paper presents a proposed adaptive admittance control that is derived based on Center of Mass (CoM) of the hexapod robot designed for walking on the bottom of water or seabed. The study has been carried out by modeling the buoyancy force following the restoration force to achieve the drowning level according to the Archimedes’ principle. The restoration force needs to be positive in order to ensure robot locomotion is not affected by buoyancy factor. As a solution to regulate this force, admittance control has been derived based on the total force of foot placement to determine CoM of the robot while walking. This admittance control is designed according to a model of a real-time based 4-degree of freedom (DoF) leg configuration of a hexapod robot that able to perform hexapod-to-quadruped transformation. The analysis focuses on the robot walking in both configuration modes; hexapod and quadruped; with both tripod and traverse-trot walking pattern respectively. The verification is done on the vertical foot motion of the leg and the body mass coordination movement for each walking simulation. The results show that the proposed admittance control is able to regulate the force restoration factor by making vertical force on each foot sufficiently large (sufficient foot placement) compared to the buoyancy force of the ocean, thus performing stable locomotion for both hexapod and quadruped mode.

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