scholarly journals Humans optimally anticipate and compensate for an uneven step during walking

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Osman Darici ◽  
Arthur D Kuo
Keyword(s):  
Human Subjects ◽  
Mechanical Energy ◽  
Bipedal Walking ◽  
Time Of Arrival ◽  
Dynamic Prediction ◽  
Simple Task ◽  
Model Predictions ◽  
Steady Level ◽  
Speed Fluctuation ◽  
Energy Economy

The simple task of walking up a sidewalk curb is actually a dynamic prediction task. The curb is a disturbance that could cause a loss of momentum if not anticipated and compensated for. It might be possible to adjust momentum sufficiently to ensure undisturbed time of arrival, but there are infinite possible ways to do so. Much of steady, level gait is determined by energy economy, which should be at least as important with terrain disturbances. It is, however, unknown whether economy also governs walking up a curb, and whether anticipation helps. Here we show that humans compensate with an anticipatory pattern of forward speed adjustments, predicted by a criterion of minimizing mechanical energy input. The strategy is mechanistically predicted by optimal control for a simple model of bipedal walking dynamics, with each leg's push-off work as input. Optimization predicts a tri-phasic trajectory of speed (and thus momentum) adjustments, including an anticipatory phase. In experiment, human subjects ascend an artificial curb with the predicted tri-phasic trajectory, which approximately conserves overall walking speed relative to undisturbed flat ground. The trajectory involves speeding up in a few steps before the curb, losing considerable momentum from ascending it, and then regaining speed in a few steps thereafter. Descending the curb entails a nearly opposite, but still anticipatory, speed fluctuation trajectory, in agreement with model predictions that speed fluctuation amplitudes should scale linearly with curb height. The fluctuation amplitudes also decrease slightly with faster average speeds, also as predicted by model. Humans can reason about the dynamics of walking to plan anticipatory and economical control, even with a sidewalk curb in the way.

scholarly journals Humans optimally anticipate and compensate for an uneven step during walking

2020 ◽  
Author(s):  
Osman Darici ◽  
Arthur D. Kuo
Keyword(s):  
Energy Input ◽  
Human Subjects ◽  
Mechanical Energy ◽  
Selection Criterion ◽  
Time Of Arrival ◽  
Forward Speed ◽  
Dynamic Prediction ◽  
Simple Task ◽  
Average Speed ◽  
Walking Dynamics

ABSTRACTThe simple task of walking up a sidewalk curb is actually a dynamic prediction task. The curb is a disturbance that causes a loss of momentum, to be anticipated and compensated for. For example, the compensation might regain momentum and ensure undisturbed time of arrival. But without a selection criterion, there are infinite possible strategies. Here we show that humans compensate with an anticipatory pattern of forward speed adjustments, with a criterion of minimizing mechanical energy input. This is predicted by optimal control for a simple model of walking dynamics, with each leg’s push-off work as input. Optimization predicts a tri-phasic trajectory of speed (and thus momentum) adjustments, including an anticipatory, feedforward phase. In experiment, human subjects successfully regain time relative to undisturbed walking, with the predicted tri-phasic trajectory. They also scale the pattern with up- or down-steps, and inversely with average speed, as also predicted by model. Humans can reason about the dynamics of walking to plan anticipatory and economical control, even with a sidewalk curb in the way.

scholarly journals Exploring the utility of robots in exposure studies

2019 ◽  
Author(s):  
Elisabeth Feld-Cook ◽  
Rahul Shome ◽  
Rosemary T. Zaleski ◽  
Krishnan Mohan ◽  
Hristiyan Kourtev ◽  
...  
Keyword(s):  
New Product Development ◽  
Human Subjects ◽  
New Product ◽  
Health Science ◽  
Exposure Model ◽  
Proof Of Concept ◽  
Simple Task ◽  
Research Ethics Review ◽  
Exposure Data ◽  
Volatile Organic

AbstractObtaining valid, reliable quantitative exposure data can be a significant challenge for industrial hygienists, exposure scientists, and other health science professionals. In this proof-of-concept study, a robotic platform was programmed to perform a simple task as a plausible alternative to human subjects in exposure studies for generating exposure data. The use of robots offers several advantages over the use of humans. Research can be completed more efficiently and there is no need to recruit, screen, or train volunteers. In addition, robots can perform tasks repeatedly without getting tired allowing for collection of an unlimited number of measurements using different chemicals to assess exposure impacts from formulation changes and new product development. The use of robots also eliminates concerns with intentional human exposures while removing health research ethics review requirements which are time consuming. In this study, a humanoid robot was programmed to paint drywall, while volatile organic compounds were measured in air for comparison to model estimates. The measured air concentrations generally agreed with more advanced exposure model estimates. These findings suggest that robots have potential as a methodology for generating exposure measurements relevant to human activities, but without using human subjects.

scholarly journals Dynamics of Dense Water Descending a Continental Slope*

2005 ◽  
Vol 35 (8) ◽  
pp. 1318-1328 ◽  
Author(s):  
Hsien-Wang Ou
Keyword(s):  
Continental Slope ◽  
Mechanical Energy ◽  
Frictional Torque ◽  
Geostrophic Balance ◽  
Friction Control ◽  
Dense Water ◽  
Density Anomaly ◽  
Mass Properties ◽  
Model Predictions ◽  
Vorticity Balance

Abstract A reduced-gravity model is used to examine the dynamics of dense water descending a continental slope. The model solves for the geostrophically adjusted state before it is subjected to significant frictional decay. For such bottom-mounted flow, it is argued that frictional torque would dominate the net vorticity balance to equalize the edge flows, resulting in double velocity cores. Constrained by the geostrophic balance, the dense water thus may settle only over a concave bottom and is sheetlike, covering typically the whole slope rise. As such, the adjustment is characterized by a spreading rather than sinking of the layer—with little descent of the upper edge but a swift downslope current propelling the lower edge. Through the mechanical energy balance, it is found in addition that a greater density anomaly would increase the total entrainment flux to more strongly dilute the original anomaly, yielding a product water that is less varied in the water-mass properties. Model predictions compare favorably with some observed dense outflows, in support of the entrainment and friction control of the geostrophic adjustment.

scholarly journals Slackness between vessel and myocardium is necessary for coronary flow reserve

2012 ◽  
Vol 302 (11) ◽  
pp. H2230-H2242 ◽  
Author(s):  
Jonathan M. Young ◽  
Jenny S. Choy ◽  
Ghassan S. Kassab ◽  
Yoram Lanir
Keyword(s):  
Coronary Flow Reserve ◽  
Coronary Flow ◽  
Mechanical Energy ◽  
Potential Effect ◽  
Experimental Measurements ◽  
Flow Reserve ◽  
Model Predictions ◽  
Effectiveness And Efficiency ◽  
Vessel Resistance ◽  
Experimental Findings

Tone regulation in coronary microvessels has largely been studied in isolated vessels in the absence of myocardial tethering. Here, the potential effect of radial tethering and interstitial space connective tissue (ISCT) between coronary microvessels and the surrounding myocardium was studied. We hypothesized that rigid tethering between microvessels and the myocardium would constrain the active contraction of arterioles and is not compatible with the observed tone regulation. The ISCT between coronary microvessels and myocardium in five swine was found to increase exponentially from 0.22 ± 0.02 μm in capillaries (modified Strahler order 0) of the endocardium to 34.9 ± 7.1 μm in epicardial vessels ( order 10). Microvessels with both soft tethering and ISCT gap were capable of significant changes in vessel resistance (up to an ∼1,600% increase), consistent with experimental measurements of high coronary flow reserve. Additionally, the mechanical energy required for myogenic contraction was estimated. The results indicate that rigid tethering requires up to four times more mechanical energy than soft tethering in the absence of a gap. Hence, the experimental measurements and model predictions suggest that effectiveness and efficiency in tone regulation can be achieved only if the vessel is both softly tethered to and separated from the myocardium in accordance with the experimental findings of ISCT gap. These results have fundamental implications on future simulations of coronary circulation.

A model for determining alveolar and small airway dimensions from aerosol recovery data

1985 ◽  
Vol 58 (2) ◽  
pp. 582-591 ◽  
Author(s):  
F. S. Rosenthal
Keyword(s):  
Close Agreement ◽  
Human Subjects ◽  
Small Airway ◽  
Breath Holding ◽  
Morphometric Measurements ◽  
Model Predictions ◽  
Two Parameters ◽  
Best Fit ◽  
Airway Dimensions

A mathematical model is presented that allows the determination of alveolar and small airway dimensions from a series of aerosol recovery measurements performed at different inspiration volumes. The model assumes 1) a symmetric dichotomous lung, 2) representation of airway and alveoli as ensembles of straight tubes, and 3) Gaussian dispersion of the aerosol bolus. Calculations with this model using dimensions given by Weibel show general agreement with experimental data on six human subjects obtained by Palmes et al. (J. Appl. Physiol. 34: 356–360, 1973). Close agreement is found by varying two parameters describing alveolar size and airway size to obtain the best fit. The resulting estimates of size are almost independent of the choice of the dispersion coefficient; however, the estimate of alveolar size is quite dependent on the form of settling assumed during breath holding. The values of alveolar diameter in the six subjects, determined under the assumption of stirred settling, ranged from 0.13 to 0.33 mm, whereas under the assumption of still settling the range was 0.24–0.65 mm. Small airway (generations 18–24) dimensions ranged from 0.41 to 0.66 mm under the still-settling assumption and 0.39 to 0.63 mm under the stirred-settling assumption. With the assumption of an intermediate (partially stirred) form of settling, the alveolar diameter in the six subjects is 0.28 +/- 0.02 mm, in close agreement with morphometric measurements by other investigators. A partially stirred form of settling is also consistent with model predictions of recovery vs. breath-holding time and with cardiogenic gas mixing in the lung.

Biped gait generation based on parametric excitation by knee-joint actuation

Robotica ◽  
2009 ◽  
Vol 27 (7) ◽  
pp. 1063-1073 ◽  
Author(s):  
Yuji Harata ◽  
Fumihiko Asano ◽  
Zhi-Wei Luo ◽  
Kouichi Taji ◽  
Yoji Uno
Keyword(s):  
Parametric Excitation ◽  
Mechanical Energy ◽  
Biped Robot ◽  
Bipedal Walking ◽  
Reference Trajectory ◽  
Gait Generation ◽  
Total Mechanical Energy ◽  
Walking Performance ◽  
Excitation Mechanisms ◽  
Telescopic Legs

SUMMARYRestoration of mechanical energy dissipating on impact at the ground is necessary for sustainable gait generation. Parametric excitation is one approach to restore the mechanical energy. Asano et al. (“Parametric excitation mechanisms for dynamic bipedal walking,” IEEE International Conference on Robotics and Automation (2005) pp. 611–617.) applied parametric excitation to a biped robot with telescopic-legs, in which up-and-down motion restores total mechanical energy like playing on the swing. In this paper, parametric excitation principle is applied to a kneed biped robot with only knee actuation and it is shown that the robot walks successively without hip actuation. We also examine influences of several parameters and reference trajectory on walking performance.

A biomechanical model for encoding joint dynamics: applications to transfemoral prosthesis control

2012 ◽  
Vol 112 (9) ◽  
pp. 1600-1611 ◽  
Author(s):  
Chris A. McGibbon
Keyword(s):  
Energy State ◽  
Human Subjects ◽  
Mechanical Energy ◽  
Biomechanical Model ◽  
Sensor Data ◽  
Future Research ◽  
Fast Speed ◽  
The Future ◽  
Joint Dynamics ◽  
Energy States

This paper presents and tests a framework for encoding joint dynamics into energy states using kinematic and kinetic knee joint sensor data and demonstrates how to use this information to predict the future energy state (torque and velocity requirements) of the joint without a priori knowledge of the activity sequence. The intended application is for enhancing micro-controlled prosthetics by making use of the embedded sensory potential of artificial limbs and classical mechanical principles of a prosthetic joint to report instantaneous energy state and most probable next energy state. When applied to the knee during preferred and fast speed walking in 8 human subjects (66 preferred-speed trials and 50 fast-speed trials), it was found that joint energy states could be consistently sequenced (75% consensus) according to mechanical energy transference conditions and subsequences appeared to reflect the stability and energy dissipation requirements of the knee during gait. When simple constraints were applied to the energy transfer input conditions (their signs), simulations indicated that it was possible to predict the future energy state with an accuracy of >80% when 2% cycle in advance (∼20 ms) of the switch and >60% for 4% (∼40 ms) in advance. This study justifies future research to explore whether this encoding algorithm can be used to identify submodes of other human activity that are relevant to TFP control, such as chair and stair activities and their transitions from walking, as well as unexpected perturbations.

Dynamic Optimization of Human Running With Analytical Gradients

2015 ◽  
Vol 10 (2) ◽  
Author(s):  
Hyun-Joon Chung ◽  
Jasbir S. Arora ◽  
Karim Abdel-Malek ◽  
Yujiang Xiang
Keyword(s):  
Human Subjects ◽  
Reaction Force ◽  
Performance Measure ◽  
Joint Torque ◽  
Upper Body ◽  
Human Model ◽  
Dynamic Prediction ◽  
Foot Strike ◽  
Analytical Gradients ◽  
Human Running

The optimization-based dynamic prediction of 3D human running motion is studied in this paper. A predictive dynamics method is used to formulate the running problem, and normal running is formulated as a symmetric and cyclic motion. Recursive Lagrangian dynamics with analytical gradients for all the constraints and objective function are incorporated in the optimization process. The dynamic effort is used as the performance measure, and the impulse at the foot strike is also included in the performance measure. The joint angle profiles and joint torque profiles are calculated for the full-body human model, and the ground reaction force (GRF) is determined. Several cause-and-effect cases are studied, and the formulation for upper-body yawing motion is proposed and simulated. Simulation results from this methodology show good correlation with experimental data obtained from human subjects and the existing literature.

Design of Joint Angle Profiles for a Planar Five-Link Bipedal System

2004 ◽  
Vol 127 (2) ◽  
pp. 192-196 ◽  
Author(s):  
Q. Wu ◽  
C. Y. Chan
Keyword(s):  
Walking Speed ◽  
Joint Angle ◽  
Early Stage ◽  
Mechanical Energy ◽  
Bipedal Walking ◽  
Motion Coordination ◽  
Gait Patterns ◽  
Kinematic Constraints ◽  
Prosthetic Feet ◽  
Insight Into

A set of joint angle profiles for a five-link bipedal model walking on level ground is designed. One feature of the joint angle profiles is that after an impulsive energy injection at an early stage of each step, the mechanical energy of the bipedal system remains constant for the rest of the step. This feature is of special interest in the studies of energetics of bipedal walking and can be beneficial to the design of modern energy-storing prosthetic feet. The joint angle profiles also satisfy four kinematic constraints, i.e., the walking speed, stance knee bias, upright posture of the trunk and motion coordination. To obtain acceptable gait patterns, a set of parameters is carefully tuned to satisfy extra conditions (repeatable gait, no hyperextension, and no scuffing at the swing knee). This work can provide some insight into the mechanics of bipedal walking and has potential to establish a framework for estimating the optimal energy storage of modern prosthetic feet.

An Optimization Model of Self-Paced Tracking

1984 ◽  
Vol 28 (4) ◽  
pp. 398-402
Author(s):  
M. A. Montazer ◽  
Colin G. Drury
Keyword(s):  
Human Performance ◽  
Human Subjects ◽  
Line Drawing ◽  
Manual Control ◽  
Sampled Data ◽  
Control Task ◽  
Drawing Task ◽  
Model Predictions ◽  
Human Operators ◽  
Fixed Boundaries

A model which describes human performance in a self-paced tracking task was developed based on the notion that human operators are intermittent-acting or sampled-data servo-mechanisms. The model had a functional form in terms of the probability of success and failure resulting from the execution of a manual control task such as drawing a line between fixed boundaries. The human operator was modelled as an optimizer, balancing costs and penalties of speeds and errors to achieve a maximum expected payoff. The performance of the model was evaluated by simulating a line drawing task on a digital computer. Model predictions obtained via simulation were compared with the data collected from human subjects performing the actual task in a laboratory setting. The predictions of the model were confirmed, suggesting that human operators can in fact be modelled as optimizers when performing a manual control task.

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