scholarly journals Optimization of Coupling Ratio and Kinematics of an Underactuated Robot Leg for Passive Terrain Adaptability

2012 ◽  
Author(s):  
Oren Y. Kanner ◽  
Aaron M. Dollar
Keyword(s):  
Performance Metrics ◽  
Reaction Force ◽  
The Body ◽  
Joint Torque ◽  
Design Parameters ◽  
Leg Length ◽  
Coupling Ratio ◽  
Joint Torques ◽  
Robot Leg ◽  
Underactuated Robot

This paper investigates how the passive adaptability of an underactuated robot leg to uneven terrain is affected by variations in design parameters. In particular, the ratio between the joint torques, the ratio between the link lengths, and the initial joint rest angles are varied to determine configurations that allow for maximum terrain roughness adaptability while minimizing the transmission of disturbance forces to the body. The results show that a proximal/distal joint torque coupling ratio of 1.58, proximal/distal leg length ratio of 0.5, and an initial proximal joint angle of −49 degrees maximize the terrain variability over which the robot can remain stable by exerting a near-constant vertical reaction force while minimizing lateral force and moment disturbances. In addition, the spring stiffness ratio allows for a tradeoff to be made between the different performance metrics.

scholarly journals Kinematic Design of an Underactuated Robot Leg for Passive Terrain Adaptability and Stability

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
Oren Y. Kanner ◽  
Aaron M. Dollar
Keyword(s):  
Reaction Force ◽  
The Body ◽  
Joint Torque ◽  
Length Ratio ◽  
Segment Length ◽  
Design Parameters ◽  
Coupling Ratio ◽  
Robot Leg ◽  
Distal Joint ◽  
Underactuated Robot

This paper investigates how the passive adaptability of an underactuated robot leg to uneven terrain is affected by variations in design parameters. In particular, the joint torque coupling ratio, segment length ratio, and rest angles are varied to determine configurations that allow for maximum terrain roughness adaptability while minimizing the transmission of disturbance forces to the body. In addition, a series of alternate leg actuation configurations are considered. The results show that a proximal/distal joint torque coupling ratio of 2 with an inverted distal joint, a proximal/distal leg length ratio of 1.25, and an initial proximal joint angle of −53 deg maximize the terrain variability over which the robot can remain stable by exerting a near-constant vertical reaction force while minimizing lateral force and moment disturbances. In addition, the spring stiffness ratio allows for a tradeoff to be made between the different performance metrics. Finally, the robot's stability with respect to its posture is discussed.

A Postural Model of Balance-Correcting Movement Strategies

1992 ◽  
Vol 2 (4) ◽  
pp. 323-347
Author(s):  
J.H.J. Allum ◽  
F. Honegger
Keyword(s):  
Normal Subjects ◽  
Opposite Polarity ◽  
The Body ◽  
Joint Torque ◽  
Support Surface ◽  
Joint Torques ◽  
Eyes Closed ◽  
Movement Strategies ◽  
Eyes Open ◽  
Balance Corrections

The patterns of joint torques and movement strategies underlying human balance corrections were examined using a postural model. Two types of support-surface perturbation, dorsiflexion rotation (ROT) and rearward translation (TRANS), were employed. These two perturbations were adjusted to produce similar profiles of ankle dorsiflexion in order to obtain information on the role of lower leg proprioceptive inputs on triggering balance corrections. In addition, the dependence of balance control on head angular and linear accelerations was investigated by comparing the responses of normal and vestibularly deficient subjects under eyes-closed and eyes-open conditions. Differences in ROT and TRANS movement strategies were examined in three ways First, the amplitude and polarity of active joint torques were analysed. These were obtained by altering joint torques applied to a postural model until movements of the model accurately duplicated those of measured responses. Second, the pattern of body-segment angular movements depicted by stick figures moving in response to the computed joint torques was investigated. Third, the peak amplitude and patterns of crosscorrelations between joint torques were measured. Active ankle, knee, and hip joint torques computed for normal subjects rotated the body forward for ROT. In the case of TRANS, computed active torques in normal were of opposite polarity to those of ROT and reversed the forward motion of the body. Subjects with vestibular deficits had lower amplitude torques for ROT and failed to counter the platform rotation. Hip torques for TRANS in vestibular deficient subjects were of opposite polarity to those of normal subjects and resulted in excessive forward trunk rotation. Normally, neck torques acted to stabilize the head in space when trunk angular velocity peaked. Vestibular deficient subjects displayed head movements in response to ROT similar to those generated when neck torques were absent. For TRANS, these same subjects exhibited overcompensatory neck torques. Stick figures of normal responses indicated a stiffening of the body into a leg and a trunk-head link for ROT and a flexible multilink motion for TRANS. Likewise, normal response strategies, defined by using crosscorrelations of joint torques, differed for ROT and TRANS. All joint torque crosscorrelations were significant for TRANS. Neck torques led those of all other joint torques by 40 ms or more, and hip joint led ankle torques by 30 ms. Joint torque correlations for ROT were organised around hip and ankle torques without a major correlation to neck torques. Fundamental changes in all torque crosscorrelations occurred for vestibularly deficient subjects under both eyes-open and eyes-closed conditions. These results support the hypothesis that the modulation of postural responses by vestibular signals occurs at all major joint links of the upright human body and that the strategy underlying balance corrections at the hip and neck is selected independent of local sensory input from the lower leg. Rearward translation and dorsiflexion rotation of a support-surface elicit different movement strategies when ankle angle, changes are matched for such disturbances to human upright balance.

The Sensitivity of Joint Torques During Running to Forceplate Data Error

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Anne Schmitz ◽  
Jaclyn Norberg
Keyword(s):  
Center Of Pressure ◽  
A Priori ◽  
Reaction Force ◽  
Analysis Data ◽  
Monte Carlo Analysis ◽  
Joint Torque ◽  
Single Subject ◽  
Joint Torques ◽  
Data Error ◽  
The Relationship

The purpose of this study was to evaluate the relationship between forceplate inaccuracies and joint torques during running. Instrumented gait analysis data were collected on a single subject running above ground. A Monte Carlo analysis was performed using 60 simulations. In each simulation, joint torques were computed as the ground reaction force (GRF) data were perturbed. Errors in joint torques were larger for proximal joints compared to the distal joints. These errors in joint torques were due more to inaccuracies in the GRF magnitude than the center of pressure (COP) measurements. Clinically, these results may be used to determine a priori the forceplate accuracy needed to measure a desired difference in joint torque between patient populations.

Active compliance control of the hydraulic actuated leg prototype

2017 ◽  
Vol 37 (3) ◽  
pp. 356-368 ◽  
Author(s):  
Guoteng Zhang ◽  
Zhenyu Jiang ◽  
Yueyang Li ◽  
Hui Chai ◽  
Teng Chen ◽  
...  
Keyword(s):  
Design Methodology ◽  
Joint Torque ◽  
Hydraulic Actuator ◽  
Passive Components ◽  
Content Type ◽  
Joint Torques ◽  
Compliant Motion ◽  
Model Based ◽  
Active Compliance ◽  
Robot Leg

Purpose Legged robots are inevitably to interact with the environment while they are moving. This paper aims to properly handle these interactions. It works to actively control the joint torques of a hydraulic-actuated leg prototype and achieve compliant motion of the leg. Design/methodology/approach This work focuses on the modelling and controlling of a hydraulic-actuated robot leg prototype. First, the design and kinematics of the leg prototype is introduced. Then the linearlized model for the hydraulic actuator is built, and a model-based leg joint torque controller is presented. Furthermore, the virtual model controller is implemented on the prototype leg to achieve active compliance of the leg. Effectiveness of the controllers are validated through the experiments on the physical platform as well as the results from simulations. Findings The hydraulic joint torque controller presented in this paper shows good torque tracking performance. And the actively compliant leg successfully emulates the performance of virtual passive components under dynamic situations. Originality/value The main contribution of this paper is that it proposed a model-based active compliance controller for the hydraulic-actuated robot leg. It will be helpful for those robots that aim to achieve versatile and safe motions.

scholarly journals Effects of body movement on yaw motion in bipedal running lizard by dynamic simulation

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243798
Author(s):  
Jeongryul Kim ◽  
Hongmin Kim ◽  
Jaeheung Park ◽  
Hwa Soo Kim ◽  
TaeWon Seo
Keyword(s):  
Dynamic Simulation ◽  
Body Movement ◽  
The Body ◽  
Joint Torque ◽  
Stride Frequency ◽  
Body Movements ◽  
Joint Torques ◽  
Biomechanical Simulation ◽  
Bipedal Gait ◽  
The Relationship

Lizards run quickly and stably in a bipedal gait, with their bodies exhibiting a lateral S-shaped undulation. We investigate the relationship between a lizard’s bipedal running and its body movement with the help of a dynamic simulation. In this study, a dynamic theoretical model of lizard is assumed as a three-link consisting of an anterior and posterior bodies, and a tail, with morphometrics based on Callisaurus draconoides. When a lizard runs straight in a stable bipedal gait, its pelvic rotation is periodically synchronized with its gait. This study shows that the S-shaped body undulation with the yaw motion is generated by minimizing the square of joint torque. Furthermore, we performed the biomechanical simulation to figure out the relationship between the lizard’s lateral body undulation and the bipedal running locomotion. In the biomechanical simulation, all joint torques significantly vary by the waist and tail’ motions at the same locomotion. Besides, when the waist and tail joint angles increase, the stride length and duration of the model also increase, and the stride frequency decreases at the same running speed. It means that the lizard’s undulatory body movements increase its stride and help it run faster. In this study, we found the benefits of the lizard’s undulatory body movement and figured out the relationship between the body movement and the locomotion by analyzing the dynamics. In the future works, we will analyze body movements under different environments with various simulators.

scholarly journals Optimal Limb Length Ratio of Quadruped Robot Minimising Joint Torque on Slopes

2009 ◽  
Vol 6 (3-4) ◽  
pp. 259-268 ◽  
Author(s):  
Tadayoshi Aoyama ◽  
Kosuke Sekiyama ◽  
Yasuhisa Hasegawa ◽  
Toshio Fukuda
Keyword(s):  
Simulation Analysis ◽  
Slope Angle ◽  
Quadruped Robot ◽  
Working Environment ◽  
Joint Torque ◽  
Limb Length ◽  
Optimal Structure ◽  
Length Ratio ◽  
Leg Length ◽  
Joint Torques

This paper aims to determine an optimal structure for a quadruped robot, which will allow the robot’s joint torque sum to be minimised. An animal’s characteristic limb length ratio is a vital part of its overall morphology and the one that enables it to travel easily through its environment. For the same reason, a robot’s structure needs to be suitably designed for locomotion in its working environment. Joint torques are necessary to maintain the posture of the robot and to accelerate joint angles during walking motion, hence, minimisation of joint torques reduces energy consumption. We performed a numerical simulation in which we analysed the joint torques for various limb lengths and slope angles in order to determine the optimal structure of a robot walking on a slope. Our investigation determines that the optimal Ratio of Rear Leg Length (RRL) can be derived by the use of a simulation designed to determine the physical structure of quadruped robot. Our analysis suggests that joint torque will increase as the slope angle becomes steeper if the rear legs of the robot are shorter than its forelegs, and that joint torque will decrease as the slope angle declines if the robot’s forelegs are shorter than its rear legs. Finally, experimental results validated our simulation analysis.

Development of 3D Equipment Interaction With Predictive Dynamics in Human Motion Simulation

2016 ◽  
Author(s):  
Hyun-Joon Chung ◽  
Yujiang Xiang
Keyword(s):  
Human Body ◽  
Degrees Of Freedom ◽  
Reaction Force ◽  
Human Motion ◽  
The Body ◽  
Joint Torque ◽  
Human Model ◽  
Motion Simulation ◽  
Predictive Dynamics ◽  
Human Motion Simulation

3D equipment interaction module in human motion simulation is developed in this paper. A predictive dynamics method is used to simulate human motion, and a helmet is modeled as the equipment that is attached to the human body. We then implement this method using the predictive dynamics task of walking. A mass-spring-damper system is attached at the top of the head as a helmet model. The equations of motion for the helmet are also derived in a recursive Lagrangian formulation within the same inertial reference frame as the human model’s. The total number of degrees of freedom for the human model is 55 — 6 degrees of freedom for global translation and rotation, and 49 degrees of freedom for the body. The helmet has 7 degrees of freedom, but 6 of them are dependent to the human model. The movement of the helmet is analyzed due to the human motion. Then, the reaction force between the human body and the equipment is calculated. Once the reaction force is obtained, it is applied to the human body as an external force in the predictive dynamics optimization process. Results include the motion of equipment, the force acting on body at the attachment point, the joint torque profiles, and the ground reaction force profiles at the foot contacting point.

On the Use of Induced End Effector Force Analysis for Determining Muscle Roles During Movement

2007 ◽  
Author(s):  
Stephen J. Piazza ◽  
Vladimir M. Zatsiorsky
Keyword(s):  
Electrical Stimulation ◽  
Muscle Function ◽  
Muscle Force ◽  
Human Movement ◽  
The Body ◽  
Joint Torque ◽  
Force Analysis ◽  
End Effector ◽  
Joint Torques ◽  
Muscle Strengthening

It is often of interest in studies of human movement to quantify the function of a muscle force or muscular joint torque. Such information is useful for the identification of the causes of movement disorders and for predicting the effects of interventions including surgical procedures, targeted muscle strengthening, focal treatments for spasticity, and functional electrical stimulation. One useful way to characterize the actions of muscle forces or muscular joint torques is to create linked-segment models of the body and analyze these linkages to determine the joint angular accelerations or end effector forces that result solely from the application of the muscle force or torque in question. Such induced acceleration (IA) analyses or induced end effector force (IEF) analyses have been applied most often to quantify muscle function during normal and pathological walking [1,2].

scholarly journals Immediate compensation for variations in self-generated Coriolis torques related to body dynamics and carried objects

2013 ◽  
Vol 110 (6) ◽  
pp. 1370-1384 ◽  
Author(s):  
Pascale Pigeon ◽  
Paul DiZio ◽  
James R. Lackner
Keyword(s):  
Dynamic Properties ◽  
Arm Movement ◽  
The Body ◽  
Joint Torque ◽  
Movement Trajectory ◽  
Joint Torques ◽  
Intersegmental Dynamics ◽  
The Right ◽  
Dynamic Dominance ◽  
Interaction Torques

We have previously shown that the Coriolis torques that result when an arm movement is performed during torso rotation do not affect movement trajectory. Our purpose in the present study was to examine whether torso motion-induced Coriolis and other interaction torques are counteracted during a turn and reach (T&R) movement when the effective mass of the hand is augmented, and whether the dominant arm has an advantage in coordinating intersegmental dynamics as predicted by the dynamic dominance hypothesis (Sainburg RL. Exp Brain Res 142: 241–258, 2002). Subjects made slow and fast T&R movements in the dark to just extinguished targets with either arm, while holding or not holding a 454-g object. Movement endpoints were equally accurate at both speeds, with either hand, and in both weight conditions, but subjects tended to angularly undershoot and produce more variable endpoints for targets requiring greater torso rotation. There were no changes in endpoint accuracy or trajectory deviation over repeated movements. The dominant right arm was more stable in its control of trajectory direction across targets, whereas the nondominant left arm had an improved ability to stop accurately on the target for higher levels of interaction torques. The trajectories to more eccentric targets were straighter when performed at higher speeds but slightly more deviated when subjects held the weight. Subjects did not slow their torso velocity or change the timing of the arm and torso velocities when holding the weight, although there was a slight decrease in their hand velocity relative to the torso. The delay between the onsets of torso and finger movements was almost twice as large for the right arm than the left, suggesting the right arm was better able to account for torso rotation in the arm movement. Holding the weight increased the peak Coriolis torque by 40% at the shoulder and 45% at the elbow and, for the most eccentric target, increased the peak net torque by 12% at the shoulder and 34% at the elbow. In accordance with Sainburg's dynamic dominance hypothesis, the right arm exhibited an advantage for coordinating intersegmental dynamics, showing a more stable finger velocity in relation to the torso across targets, decreasing error variability with movement speed, and more synchronized peaks of finger relative and torso angular velocities in conditions with greater joint torque requirements. The arm used had little effect on the movement path and the magnitude of the joint torques in any of the conditions. These results indicate that compensations for forthcoming Coriolis torque variations take into account the dynamic properties of the body and of external objects, as well as the planned velocities of the torso and arm.

scholarly journals Upper-Limb Isometric Force Feasible Set: Evaluation of Joint Torque-Based Models

Biomechanics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 102-117
Author(s):  
Nasser Rezzoug ◽  
Vincent Hernandez ◽  
Philippe Gorce
Keyword(s):  
Upper Limb ◽  
Isometric Force ◽  
Joint Torque ◽  
Force Distribution ◽  
Prediction Errors ◽  
Feasible Set ◽  
Joint Torques ◽  
Motor Abilities ◽  
Capacity Evaluation ◽  
Measured Force

A force capacity evaluation for a given posture may provide better understanding of human motor abilities for applications in sport sciences, rehabilitation and ergonomics. From data on posture and maximum isometric joint torques, the upper-limb force feasible set of the hand was predicted by four models called force ellipsoid, scaled force ellipsoid, force polytope and scaled force polytope, which were compared with a measured force polytope. The volume, shape and force prediction errors were assessed. The scaled ellipsoid underestimated the maximal mean force, and the scaled polytope overestimated it. The scaled force ellipsoid underestimated the volume of the measured force distribution, whereas that of the scaled polytope was not significantly different from the measured distribution but exhibited larger variability. All the models characterized well the elongated shape of the measured force distribution. The angles between the main axes of the modelled ellipsoids and polytopes and that of the measured polytope were compared. The values ranged from 7.3° to 14.3°. Over the entire surface of the force ellipsoid, 39.7% of the points had prediction errors less than 50 N; 33.6% had errors between 50 and 100 N; and 26.8% had errors greater than 100N. For the force polytope, the percentages were 56.2%, 28.3% and 15.4%, respectively.

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