scholarly journals Whole-Body Dynamic Analysis of Challenging Slackline Jumping

2020 ◽  
Vol 10 (3) ◽  
pp. 1094 ◽  
Author(s):  
Kevin Stein ◽  
Katja Mombaur
Keyword(s):  
Center Of Pressure ◽  
Center Of Mass ◽  
Contact Forces ◽  
Joint Torque ◽  
Whole Body ◽  
Reconstruction Method ◽  
Motion Reconstruction ◽  
Interaction Forces ◽  
Optimization Framework ◽  
Equations Of Motions

Maintaining balance on a slackline is a challenging task in itself. Walking on a high line, jumping and performing twists or somersaults seems nearly impossible. Contact forces are essential to understanding how humans maintain balance in such challenging situations, but they cannot always be measured directly. Therefore, we propose a contact model for slackline balancing that includes the interaction forces and torques as well as the position of the Center of Pressure. We apply this model within an optimization framework to perform a fully dynamic motion reconstruction of a jump with a rotation of approximately 180 ° . Newton’s equations of motions are implemented as constraints to the optimization, hence the optimized motion is physically feasible. We show that a conventional kinematic analysis results in dynamic inconsistencies. The advantage of our method becomes apparent during the flight phase of the motion and when comparing the center of mass and angular momentum dynamics. With our motion reconstruction method all momentum is conserved, whereas the conventional analysis shows momentum changes of up to 30%. Furthermore, we get additional and reliable information on the interaction forces and the joint torque that allow us to further analyze slackline balancing strategies.

scholarly journals Sliding Balance Control of a Point-Foot Biped Robot Based on a Dual-Objective Convergent Equation

2021 ◽  
Vol 11 (9) ◽  
pp. 4016
Author(s):  
Yizhou Lu ◽  
Junyao Gao ◽  
Xuanyang Shi ◽  
Dingkui Tian ◽  
Yi Liu
Keyword(s):  
Balance Control ◽  
Center Of Mass ◽  
Biped Robot ◽  
Optimization Method ◽  
Contact Forces ◽  
Joint Torque ◽  
Whole Body ◽  
Physical Constraints ◽  
Equilibrium Control ◽  
Control Framework

The point-foot biped robot is highly adaptable to and can move rapidly on complex, non-structural and non-continuous terrain, as demonstrated in many studies. However, few studies have investigated balance control methods for point-foot sliding on low-friction terrain. This article presents a control framework based on the dual-objective convergence method and whole-body control for the point-foot biped robot to stabilize its posture balance in sliding. In this control framework, a dual-objective convergence equation is used to construct the posture stability criterion and the corresponding equilibrium control task, which are simultaneously converged. Control tasks are then carried out through the whole-body control framework, which adopts an optimization method to calculate the viable joint torque under the physical constraints of dynamics, friction and contact forces. In addition, this article extends the proposed approach to balance control in standing recovery. Finally, the capabilities of the proposed controller are verified in simulations in which a 26.9-kg three-link point-foot biped robot (1) slides over a 10∘ trapezoidal terrain, (2) slides on terrain with a sinusoidal friction coefficient between 0.05 and 0.25 and (3) stands and recovers from a center-of-mass offset of 0.02 m.

Balance Recovery based on Whole-Body Control using Joint Torque Feedback for Quadrupedal Robots

2021 ◽  
pp. 1-18
Author(s):  
Young Hun Lee ◽  
Hyunyong Lee ◽  
Hansol Kang ◽  
Jun Hyuk Lee ◽  
Ji Man Park ◽  
...  
Keyword(s):  
Force Feedback ◽  
Center Of Mass ◽  
Legged Locomotion ◽  
Joint Torque ◽  
Whole Body ◽  
External Disturbances ◽  
Feed Forward ◽  
The Moment ◽  
Joint Torque Feedback ◽  
Capture Point

Abstract In legged locomotion, the contact force between a robot and the ground plays a crucial role in balancing the robot. However, in quadrupedal robots, general whole-body controllers generate feed-forward force commands without considering the actual torque or force feedback. This paper presents a whole-body controller by using the actual joint torque measured from a torque sensor, which enables the quadrupedal robot to demonstrate both dynamic locomotion and reaction to external disturbances. We compute external joint torque using the measured joint torque and the robot's dynamics, and then transform this to the moment of the center of mass (CoM). Using the computed CoM moment, the moment-based impedance controller distributes a feed-forward force corresponding to the desired moment of the CoM to stabilize the robot's balance. Furthermore, to recover balance, the CoM motion is generated using capture point-based stepping control and zero moment point trajectory. The proposed whole-body controller was tested on a quadrupedal robot, named AiDIN-VI. Locomotive abilities on uneven terrains and slopes and in the presence of external disturbances are verified through experiments.

Robust Bipedal Locomotion Based on a Hierarchical Control Structure

Robotica ◽  
2019 ◽  
Vol 37 (10) ◽  
pp. 1750-1767 ◽  
Author(s):  
Jianwen Luo ◽  
Yao Su ◽  
Lecheng Ruan ◽  
Ye Zhao ◽  
Donghyun Kim ◽  
...  
Keyword(s):  
Center Of Pressure ◽  
Center Of Mass ◽  
Hierarchical Control ◽  
Middle Level ◽  
Smooth Transition ◽  
Whole Body ◽  
Joint Torques ◽  
Low Level ◽  
Hybrid Controller ◽  
High Level

SummaryTo improve biped locomotion’s robustness to internal and external disturbances, this study proposes a hierarchical structure with three control levels. At the high level, a foothold sequence is generated so that the Center of Mass (CoM) trajectory tracks a planned path. The planning procedure is simplified by selecting the midpoint between two consecutive Center of Pressure (CoP) points as the feature point. At the middle level, a novel robust hybrid controller is devised to drive perturbed system states back to the nominal trajectory within finite cycles without chattering. The novelty lies in that the hybrid controller is not subject to linear CoM dynamic constraints. The hybrid controller consists of two sub-controllers: an oscillation controller and a smoothing controller. For the oscillation controller, the desired CoM height is specified as a sine-shaped function, avoiding a new attractive limit cycle. However, this controller results in the inevitable chattering because of discontinuities. A smoothing controller provides continuous properties and thus can inhibit the chattering problem, but has a smaller region of attraction compared with the oscillation controller. A hybrid controller merges the two controllers for a smooth transition. At the low level, the desired CoM motion is defined as tasks and embedded in a whole body operational space (WBOS) controller to compute the joint torques analytically. The novelty of the low-level controller lies in that within the WBOS framework, CoM motion is not subject to fixed CoM dynamics and thus can be generalized.

scholarly journals Human kinematic, kinetic and EMG data during different walking and stair ascending and descending tasks

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Tiziana Lencioni ◽  
Ilaria Carpinella ◽  
Marco Rabuffetti ◽  
Alberto Marzegan ◽  
Maurizio Ferrarin
Keyword(s):  
Lower Limb ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Simulation Models ◽  
Human Locomotion ◽  
Surface Emg ◽  
Whole Body ◽  
Bipedal Robots ◽  
Lower Limb Muscles ◽  
Reaction Forces

AbstractThis paper reports the kinematic, kinetic and electromyographic (EMG) dataset of human locomotion during level walking at different velocities, toe- and heel-walking, stairs ascending and descending. A sample of 50 healthy subjects, with an age between 6 and 72 years, is included. For each task, both raw data and computed variables are reported including: the 3D coordinates of external markers, the joint angles of lower limb in the sagittal, transversal and horizontal anatomical planes, the ground reaction forces and torques, the center of pressure, the lower limb joint mechanical moments and power, the displacement of the whole body center of mass, and the surface EMG signals of the main lower limb muscles. The data reported in the present study, acquired from subjects with different ages, represents a valuable dataset useful for future studies on locomotor function in humans, particularly as normative reference to analyze pathological gait, to test the performance of simulation models of bipedal locomotion, and to develop control algorithms for bipedal robots or active lower limb exoskeletons for rehabilitation.

Optimization-Based Whole-Body Control of a Series Elastic Humanoid Robot

2016 ◽  
Vol 13 (01) ◽  
pp. 1550034 ◽  
Author(s):  
Michael A. Hopkins ◽  
Alexander Leonessa ◽  
Brian Y. Lattimer ◽  
Dennis W. Hong
Keyword(s):  
Inverse Dynamics ◽  
Contact Forces ◽  
Joint Torque ◽  
Whole Body ◽  
Quadratic Program ◽  
Successful Implementation ◽  
Control Approach ◽  
Floating Base ◽  
High Level ◽  
Series Elastic

As whole-body control approaches begin to enter the mainstream of humanoid robotics research, there is a real need to address the challenges and pitfalls encountered in hardware implementations. This paper presents an optimization-based whole-body control framework enabling compliant locomotion on THOR, a 34 degree of freedom humanoid featuring force-controllable series elastic actuators (SEAs). Given desired momentum rates of change, end-effector accelerations, and joint accelerations from a high-level locomotion controller, joint torque setpoints are computed using an efficient quadratic program (QP) formulation designed to solve the floating-base inverse dynamics (ID). Constraints on the centroidal dynamics, frictional contact forces, and joint position/torque limits ensure admissibility of the optimized joint setpoints. The control approach is supported by an electromechanical design that relies on custom linear SEAs and embedded joint controllers to accurately regulate the internal and external forces computed by the whole-body QP. Push recovery and walking tests conducted using the THOR humanoid validate the effectiveness of the proposed approach. In each case, balancing is achieved using a planning and control approach based on the time-varying divergent component of motion (DCM) implemented for the first time on hardware. We discuss practical considerations that led to the successful implementation of low-impedance whole-body control on our hardware system including the design of the robot’s high-level standing and stepping behaviors and low-level joint-space controllers. The paper concludes with an application of the presented approach for a humanoid firefighting demonstration onboard a decommissioned US Navy ship.

Analyzing and Reducing Energy Usage in a Humanoid Robot During Standing Up and Sitting Down Tasks

2016 ◽  
Vol 13 (04) ◽  
pp. 1650014 ◽  
Author(s):  
Ercan Elibol ◽  
Juan Calderon ◽  
Martin Llofriu ◽  
Wilfrido Moreno ◽  
Alfredo Weitzenfeld
Keyword(s):  
Humanoid Robot ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Electrical Power ◽  
Joint Torque ◽  
Q Learning ◽  
Current Usage ◽  
Standing Up ◽  
Joint Velocity ◽  
Joint Acceleration

The aim of this paper is to reduce the energy consumption of a humanoid by analyzing electrical power as input to the robot and mechanical power as output. The analysis considers motor dynamics during standing up and sitting down tasks. The motion tasks of the humanoid are described in terms of joint position, joint velocity, joint acceleration, joint torque, center of mass (CoM) and center of pressure (CoP). To reduce the complexity of the robot analysis, the humanoid is modeled as a planar robot with four links and three joints. The humanoid robot learns to reduce the overall motion torque by applying Q-Learning in a simulated model. The resulting motions are evaluated on a physical NAO humanoid robot during standing up and sitting down tasks and then contrasted to a pre-programmed task in the NAO. The stand up and sit down motions are analyzed for individual joint current usage, power demand, torque, angular velocity, acceleration, CoM and CoP locations. The overall result is improved energy efficiency between 25–30% when compared to the pre-programmed NAO stand up and sit down motion task.

POSTURE CONTROL AND BALANCE DURING TAI CHI CHUAN PUSH HANDS MOVEMENTS IN A FIXED STANCE

2012 ◽  
Vol 12 (05) ◽  
pp. 1250030 ◽  
Author(s):  
LIN-HWA WANG ◽  
KUO-CHENG LO ◽  
FONG-CHIN SU
Keyword(s):  
Tai Chi ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Reaction Force ◽  
Whole Body ◽  
Expert Group ◽  
Tai Chi Chuan ◽  
Kinematic Data ◽  
Analysis System ◽  
Force Data

The present study investigated the adequacy of the interaction between the center of mass (COM) and the center of pressure (COP) for maintaining dynamic stability during Tai Chi Chuan (TCC) Push Hands movements in a fixed stance. The COM of the whole body and COP were calculated. Four TCC experts, with 10.3 ± 1.7 years' experience in the Push Hands technique, and 4 TCC beginners, with 2.5 ± 1.3 years' Push Hands experience, were recruited. An Expert Vision Eagle motion analysis system collected kinematic data and 4 Kistler force plates collected the ground reaction force data. The expert group of TCC practitioners showed a significantly more vertical (P = 0.001) direction in the neutralizing circle, and significantly larger values for anterior–posterior (A–P) (P = 0.006) and vertical (P = 0.0004) displacement in the enticing circle, than the beginner group. Compared with the beginner group, the expert group demonstrated significantly greater velocity A–P (P = 0.001) and vertical (P = 0.001) COM displacements in the enticing circle. A significant extent main effect (P = 0.0028) was observed for the COPA–P excursion between the expert and beginner groups during Push Hands movements. The greater A–P force generated by both groups during the initiation of the Push Hands cycle probably reflects the more rapid and forward-oriented nature of this movement. The TCC beginners might have difficulties with movement transfers because of disruptions in the temporal sequencing of the forces. Overall, results indicated that the initial experience-related differences in COM transfers are reflected in the Push Hands movement cycle.

scholarly journals Trajectory Optimization for Hybrid Wheeled-Legged Robots in Challenging Terrain

2020 ◽  
Author(s):  
Vivian Suzano Medeiros ◽  
Marco Antonio Meggiolaro
Keyword(s):  
Trajectory Optimization ◽  
Experimental Tests ◽  
Contact Forces ◽  
Legged Robots ◽  
Whole Body ◽  
Planning Problem ◽  
Average Speed ◽  
Optimization Framework ◽  
Promising Solution ◽  
Reference Trajectories

Wheeled-legged robots are a promising solution for agile locomotion in challenging terrain, combining the speed of the wheels with the ability of the legs to cope with unstructured environments. This paper presents a trajectory optimization framework that allows wheeled-legged robots to navigate in challenging terrain, e.g., steps, slopes, gaps, while negotiating these obstacles with dynamic motions. The framework generates the robot’s base motion as well as the wheels’ positions and contact forces along the trajectory, accounting for the terrain map and the dynamics of the robot. The knowledge of the terrain map allows the optimizer to generate feasible motions for obstacle negotiation in a dynamic manner, at higher speeds. To take full advantage of the hybrid nature of wheeled-legged robots, driving and stepping motions are both considered in a single planning problem that can generate trajectories with purely driving motions or hybrid driving-stepping motions. The optimization is formulated as a Nonlinear Programming Problem (NLP) employing a phase-based parametrization to optimize over the wheels’ motion and contact forces. The reference trajectories are tracked by a hierarchical whole-body controller that computes the torque actuation commands for the robot. The motion plans are verified on the quadrupedal robot ANYmal equipped with non-steerable torque-controlled wheels in simulations and experimental tests. Agile hybrid motions are demonstrated in simulations with discontinuous obstacles, such as floating steps and gaps, at an average speed of 0.75 m/s.

On the Manipulability of the Center of Mass of Humanoid Robots: Application to Design

2010 ◽  
Author(s):  
Sebastien Cotton ◽  
Philippe Fraisse ◽  
Andrew P. Murray
Keyword(s):  
Humanoid Robot ◽  
Mechanical Design ◽  
Dynamic Balance ◽  
Center Of Mass ◽  
Humanoid Robots ◽  
Contact Forces ◽  
Joint Torque ◽  
Contact Points ◽  
Floating Base ◽  
Space Formulation

This paper proposes an analysis of the manipulability of the Center of Mass (CoM) of humanoid robots. Starting from the dynamic equations of humanoid robots, the operational space formulation is used to express the dynamics of humanoid robots at their CoM and under their specific characteristics: a free-floating base, forces at contact points, and dynamic balance constraints. After a review of the kinematic manipulability of the CoM, the concept of dynamic manipulability of the CoM is introduced. The latter represents the ability of a humanoid robot to generate a spatial motion under a stability criterion. The size and shape of the dynamic manipulability of the CoM are a function of the joint torque limitations, the contact forces and the zero moment point used as a stability criteria. Two calculations of the CoM dynamic manipulability are proposed, a fast ellipsoid approximation, and the exact polyhedron computation. A case study illustrates the proposed approach on the HOAP3 humanoid robot and its use for mechanical design optimization.

scholarly journals The Relationships Among Sagittal-Plane Lower Extremity Moments: Implications for Landing Strategy in Anterior Cruciate Ligament Injury Prevention

2009 ◽  
Vol 44 (1) ◽  
pp. 33-38 ◽  
Author(s):  
Yohei Shimokochi ◽  
Sae Yong Lee ◽  
Sandra J. Shultz ◽  
Randy J. Schmitz
Keyword(s):  
Anterior Cruciate Ligament ◽  
Lower Extremity ◽  
Sagittal Plane ◽  
Center Of Pressure ◽  
Cruciate Ligament ◽  
Center Of Mass ◽  
Knee Extensor ◽  
Whole Body ◽  
Plantar Flexor ◽  
Anterior Cruciate

Abstract Context: Excessive quadriceps contraction with insufficient hamstrings muscle cocontraction has been shown to be a possible contributing factor for noncontact anterior cruciate ligament (ACL) injuries. Assessing the relationships among lower extremity internal moments may provide some insight into avoiding muscle contraction patterns that increase ACL injury risk. Objective: To examine the relationships of knee-extensor moment with ankle plantar-flexor and hip-extensor moments and to examine the relationship between knee moment and center of pressure as a measure of neuromuscular response to center-of-mass position. Design: Cross-sectional study. Setting: Applied Neuromechanics Research Laboratory. Patients or Other Participants: Eighteen healthy, recreationally active women (age  =  22.3 ± 2.8 years, height  =  162.5 ± 8.1 cm, mass  =  57.8 ± 9.3 kg). Intervention(s): Participants performed a single-leg landing from a 45-cm box onto a force plate. Kinetic and kinematic data were collected. Main Outcome Measure(s): Pearson product moment correlation coefficients were calculated among the net peak knee-extensor moment (KEMpk), sagittal-plane ankle (AM) and hip (HM) net internal moments, and anterior-posterior center of pressure relative to foot center of mass at KEMpk (COP). Results: Lower KEMpk related to both greater AM (r  =  −0.942, P < .001) and HM (r  =  −0.657, P  =  .003). We also found that more anterior displacement of COP was related to greater AM (r  =  −0.750, P < .001) and lower KEMpk (r  =  0.618, P  =  .006). Conclusions: Our results suggest that participants who lean the whole body forward during landing may produce more plantar-flexor moment and less knee-extensor moment, possibly increasing hip-extensor moment and decreasing knee-extensor moment production. These results suggest that leaning forward may be a technique to decrease quadriceps contraction demand while increasing hamstrings cocontraction demand during a single-leg landing.

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