scholarly journals Frequency-dependent force direction elucidates neural control of balance

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Kaymie Shiozawa ◽  
Jongwoo Lee ◽  
Marta Russo ◽  
Dagmar Sternad ◽  
Neville Hogan
Keyword(s):  
Neural Control ◽  
Inverted Pendulum ◽  
Control Method ◽  
Control Strategies ◽  
Quiet Standing ◽  
Assistive Device ◽  
Ground Reaction Forces ◽  
Control Effort ◽  
Frequency Dependent ◽  
Reaction Forces

Abstract Background Maintaining upright posture is an unstable task that requires sophisticated neuro-muscular control. Humans use foot–ground interaction forces, characterized by point of application, magnitude, and direction to manage body accelerations. When analyzing the directions of the ground reaction forces of standing humans in the frequency domain, previous work found a consistent pattern in different frequency bands. To test whether this frequency-dependent behavior provided a distinctive signature of neural control or was a necessary consequence of biomechanics, this study simulated quiet standing and compared the results with human subject data. Methods Aiming to develop the simplest competent and neuromechanically justifiable dynamic model that could account for the pattern observed across multiple subjects, we first explored the minimum number of degrees of freedom required for the model. Then, we applied a well-established optimal control method that was parameterized to maximize physiologically-relevant insight to stabilize the balancing model. Results If a standing human was modeled as a single inverted pendulum, no controller could reproduce the experimentally observed pattern. The simplest competent model that approximated a standing human was a double inverted pendulum with torque-actuated ankle and hip joints. A range of controller parameters could stabilize this model and reproduce the general trend observed in experimental data; this result seems to indicate a biomechanical constraint and not a consequence of control. However, details of the frequency-dependent pattern varied substantially across tested control parameter values. The set of parameters that best reproduced the human experimental results suggests that the control strategy employed by human subjects to maintain quiet standing was best described by minimal control effort with an emphasis on ankle torque. Conclusions The findings suggest that the frequency-dependent pattern of ground reaction forces observed in quiet standing conveys quantitative information about human control strategies. This study’s method might be extended to investigate human neural control strategies in different contexts of balance, such as with an assistive device or in neurologically impaired subjects.

scholarly journals Frequency-Dependent Force Direction Elucidates Neural Control of Balance

2020 ◽  
Author(s):  
Kaymie Shiozawa ◽  
Jongwoo Lee ◽  
Marta Russo ◽  
Dagmar Sternad ◽  
Neville Hogan
Keyword(s):  
Neural Control ◽  
Inverted Pendulum ◽  
Interaction Force ◽  
Intersection Point ◽  
Quiet Standing ◽  
Relative Cost ◽  
Control Effort ◽  
Frequency Dependent ◽  
Controller Parameter ◽  
Dependent Behavior

Abstract Background: Maintaining upright posture is an unstable task that requires control of translational and rotational motions. Humans use foot-ground interaction force, characterized by point of application, magnitude, and direction to manage body accelerations. Previous work identified a point of intersection of the foot-ground interaction force vectors that exhibited consistent frequency-dependent behavior. Methods: To test whether this frequency-dependent behavior provided a distinctive signature of neural control or was a necessary consequence of biomechanics, this study simulated quiet standing and compared the results with human subject data. If a standing human was modeled as a single inverted pendulum, no controller could reproduce the experimentally observed frequency-dependence of the intersection point height. The simplest competent model that approximated a standing human was a double inverted pendulum with torque-actuated ankle and hip joints. It was stabilized by a linear feedback controller based on position and velocity errors of each joint. Results: When the relative cost between state deviation and control effort was varied, the frequency at which the intersection point crossed the center of mass position shifted. A similar effect was obtained by varying the relative cost between the ankle and hip control effort. The relative strength of ankle and hip actuation noise added to the simulated system affected the intersection point height at high frequencies. Conclusions: As a range of controller parameter sets could stabilize this model and produce the observed change in the vertical position of the intersection point with increasing frequency, the decrease in intersection point height appears to reflect a biomechanical constraint and not a consequence of control. Among the several controller parameter sets considered, that which best reproduced the human experimental results used minimal control effort and more ankle torque than hip torque. This suggests that the neural strategy employed by human subjects to maintain quiet standing balance engages at least two degrees of freedom and is best described by minimal control eort and emphasizing ankle torque.

The Effects of Uni- and Bilateral Fatigue on Postural and Power Tasks

2013 ◽  
Vol 29 (1) ◽  
pp. 44-48 ◽  
Author(s):  
Paulo H. Marchetti ◽  
Maria I.V. Orselli ◽  
Marcos Duarte
Keyword(s):  
Lower Limb ◽  
Healthy Subjects ◽  
Postural Sway ◽  
Center Of Pressure ◽  
Lower Limbs ◽  
Quiet Standing ◽  
Ground Reaction Forces ◽  
Before And After ◽  
Reaction Forces ◽  
The Mean

The aim of this study was to investigate the effects of unilateral and bilateral fatigue on both postural and power bipedal tasks. Ten healthy subjects performed two tasks: bipedal quiet standing and a maximal bipedal counter-movement jumping before and after unilateral (with either the dominant or nondominant lower limb) and bilateral (with both lower limbs) fatigue. We employed two force plates (one under each lower limb) to measure the ground reaction forces and center of pressure produced by subjects during the tasks. To quantify the postural sway during quiet standing, we calculated the resultant center of pressure (COP) speed and COP area of sway, as well as the mean weight distribution between lower limbs. To quantify the performance during the countermovement jumping, we calculated the jump height and the peak force of each lower limb. We observed that both unilateral and bilateral fatigue affected the performance of maximal voluntary jumping and standing tasks and that the effects of unilateral and bilateral fatigue were stronger in the dominant limb than in the nondominant limb during bipedal tasks. We conclude that unilateral neuromuscular fatigue affects both postural and power tasks negatively.

scholarly journals Stabilization demands of walking modulate the vestibular contributions to gait

2020 ◽  
Author(s):  
Rina M. Magnani ◽  
Sjoerd M. Bruijn ◽  
Jaap H. van Dieën ◽  
Patrick A. Forbes
Keyword(s):  
Dynamic Stability ◽  
Vestibular Stimulation ◽  
Erector Spinae ◽  
Medial Gastrocnemius ◽  
Ground Reaction Forces ◽  
Local Dynamic ◽  
Control Effort ◽  
Gait Stability ◽  
Local Dynamic Stability ◽  
Reaction Forces

AbstractStable walking relies critically on motor responses to signals of head motion provided by the vestibular system, which are phase-dependent and modulated differently within each muscle. It is unclear, however, whether these vestibular contributions also vary according to the stability of the walking task. Here we investigate how vestibular signals influence muscles relevant for gait stability (medial gastrocnemius, gluteus medius and erector spinae) – as well as their net effect on ground reaction forces – while humans walked normally, with mediolateral stabilization, wide and narrow steps. We estimated coherence of electrical vestibular stimulation (EVS) with muscle activity and mediolateral ground reaction forces, together with local dynamic stability of trunk kinematics. Walking with external stabilization increased local dynamic stability and decreased coherence between EVS and all muscles/forces compared to normal walking. Wide-base walking also decreased vestibulo-motor coherence, though gait stability did not differ. Conversely, narrow-base walking increased local dynamic stability, but produced muscle-specific increases and decreases in coherence that resulted in a net increase in vestibulo-motor coherence with ground reaction forces. Overall, our results show that while vestibular contributions may vary with gait stability, they more critically depend on the stabilization demands (i.e. control effort) needed to maintain a stable walking pattern.

scholarly journals Stability in skipping gaits

2016 ◽  
Vol 3 (11) ◽  
pp. 160602 ◽  
Author(s):  
Emanuel Andrada ◽  
Roy Müller ◽  
Reinhard Blickhan
Keyword(s):  
Numerical Simulations ◽  
Inverted Pendulum ◽  
Ground Reaction Forces ◽  
Fast Running ◽  
Leg Stiffness ◽  
Adult Humans ◽  
Speed Range ◽  
Reaction Forces ◽  
System Energy ◽  
Male Subjects

As an alternative to walking and running, humans are able to skip. However, adult humans avoid it. This fact seems to be related to the higher energetic costs associated with skipping. Still, children, some birds, lemurs and lizards use skipping gaits during daily locomotion. We combined experimental data on humans with numerical simulations to test whether stability and robustness motivate this choice. Parameters for modelling were obtained from 10 male subjects. They locomoted using unilateral skipping along a 12 m runway. We used a bipedal spring loaded inverted pendulum to model and to describe the dynamics of skipping. The subjects displayed higher peak ground reaction forces and leg stiffness in the first landing leg (trailing leg) compared to the second landing leg (leading leg). In numerical simulations, we found that skipping is stable across an amazing speed range from skipping on the spot to fast running speeds. Higher leg stiffness in the trailing leg permits longer strides at same system energy. However, this strategy is at the same time less robust to sudden drop perturbations than skipping with a stiffer leading leg. A slightly higher stiffness in the leading leg is most robust, but might be costlier.

Ground Reaction Force Reduction of Biped Robot for Walking Along a Step with Dual Length Linear Inverted Pendulum Method

2013 ◽  
Vol 25 (1) ◽  
pp. 220-231 ◽  
Author(s):  
Fariz Ali ◽  
◽  
Naoki Motoi ◽  
Kirill Van Heerden ◽  
Atsuo Kawamura
Keyword(s):  
Inverted Pendulum ◽  
Reaction Force ◽  
Biped Robot ◽  
Ground Reaction Forces ◽  
Bipedal Robot ◽  
Impact Forces ◽  
Reaction Forces ◽  
Left And Right ◽  
Newton Raphson ◽  
Force Reduction

A bipedal robot should be robust and able to move in various directions on stairs. However, up to date many research studies have been focusing on walking in the up or down direction only. Therefore, a strategy to realize walking along a step is investigated. In conventional methods, CoM is moved up or down during walking in this situation. In this paper, a method named as Dual Length Linear Inverted Pendulum Method (DLLIPM) with Newton-Raphson is proposed for 3-D biped robot walking. The proposed method applies different length of pendulum at left and right legs in order to represent the CoM height. By using the proposed method, maximum impact forces are reduced. From the Ground Reaction Forces (GRF) data obtained in the simulations, the validity of the proposed method is confirmed.

scholarly journals Gravity Compensation and Feedback of Ground Reaction Forces for Biped Balance Control

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Satoshi Ito ◽  
Shingo Nishio ◽  
Yuuki Fukumoto ◽  
Kojiro Matsushita ◽  
Minoru Sasaki
Keyword(s):  
Control Method ◽  
Balance Control ◽  
Biped Robot ◽  
Effective Control ◽  
Ground Reaction Forces ◽  
Gravity Compensation ◽  
Reaction Forces ◽  
Error Accumulation ◽  
Integral Feedback ◽  
The Stability

This paper considers the balance control of a biped robot under a constant external force or on a sloped ground. We have proposed a control method with feedback of the ground reaction forces and have realized adaptive posture changes that ensure the stability of the robot. However, fast responses have not been obtained because effective control is achieved by an integral feedback that accompanies a time delay necessary for error accumulation. To improve this response, here, we introduce gravity compensation in a feedforward manner. The stationary state and its stability are analyzed based on dynamic equations, and the robustness as well as the response is evaluated using computer simulations. Finally, the adaptive behaviors of the robot are confirmed by standing experiments on the slope.

scholarly journals The Characteristics of Feet Center of Pressure Trajectory during Quiet Standing

2020 ◽  
Vol 10 (8) ◽  
pp. 2940
Author(s):  
Jacek Stodółka ◽  
Wieslaw Blach ◽  
Janez Vodicar ◽  
Krzysztof Maćkała
Keyword(s):  
Normative Data ◽  
Center Of Pressure ◽  
Bilateral Symmetry ◽  
Quiet Standing ◽  
Ground Reaction Forces ◽  
Scatter Plot ◽  
Additional Investigation ◽  
Plot Analysis ◽  
Reaction Forces ◽  
Positive Correlations

To investigate the level of bilateral symmetry or asymmetry between right and left foot center of pressure (COP) trajectory in the mediolateral and anteroposterior directions, this study involved 102 participants (54 females and 48 males). Ground reaction forces were measured using two Kistler force plates during two 45-s quiet standing trials. Comparisons of COP trajectory were performed by correlation and scatter plot analysis. Strong and very strong positive correlations (from 0.6 to 1.0) were observed between right and left foot anteroposterior COP displacement trajectory in 91 participants; 11 individuals presented weak or negative correlations. In the mediolateral direction, moderate and strong negative correlations (from −0.5 to −1.0) were observed in 69 participants, weak negative or weak positive correlations in 30 individuals, and three showed strong positive correlations (0.6 to 1.0). Additional investigation is warranted to compare COP trajectories between asymptotic individuals as assessed herein (to determine normative data) and those with foot or leg symptoms to better understand the causes of COP asymmetry and aid clinicians with the diagnosis of posture-related pathologies.

Impactless Biped Walking on Stairs

2013 ◽  
Author(s):  
Lulu Gong
Keyword(s):  
Control Method ◽  
Effective Control ◽  
Ground Reaction Forces ◽  
Biped Walking ◽  
Control Scheme ◽  
Reaction Forces ◽  
Consumption Energy ◽  
Ground Reactions ◽  
The Stability ◽  
Energetic Performance

A motion/force control scheme was proposed to investigate biped impactless walking, which has proven to be used effectively to achieve stable walking on slopes. This paper aims to investigate the efficiency of walking stairs. Good trajectory generation and effective control method are important for operating and ensuring the stability of biped walking on stairs. Walking is illustrated by a seven-link biped with six control actuators, the number of which always equals to that of motion and force specifications. In order to avoid impacts, the specified motion of the biped and its ground reactions are controlled. Control torques, ground reaction forces and consumption energy of the biped lower limb joints are calculated for ascending stairs, walking on flat terrain and descending stairs. Three different locomotion velocities are studied in order to compare the energetic performance of the biped walking up-and-down stairs.

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