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.

scholarly journals Simulation of Disturbance Recovery Based on MPC and Whole-Body Dynamics Control of Biped Walking

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2971 ◽  
Author(s):  
Xuanyang Shi ◽  
Junyao Gao ◽  
Yizhou Lu ◽  
Dingkui Tian ◽  
Yi Liu
Keyword(s):  
Large Scale ◽  
Center Of Mass ◽  
Biped Robot ◽  
Optimization Method ◽  
Stability Control ◽  
Body Motion ◽  
Whole Body ◽  
Human Beings ◽  
Foot Placement ◽  
Body Dynamics

Biped robots are similar to human beings and have broad application prospects in the fields of family service, disaster rescue and military affairs. However, simplified models and fixed center of mass (COM) used in previous research ignore the large-scale stability control ability implied by whole-body motion. The present paper proposed a two-level controller based on a simplified model and whole-body dynamics. In high level, a model predictive control (MPC) controller is implemented to improve zero moment point (ZMP) control performance. In low level, a quadratic programming optimization method is adopted to realize trajectory tracking and stabilization with friction and joint constraints. The simulation shows that a 12-degree-of-freedom force-controlled biped robot model, adopting the method proposed in this paper, can recover from a 40 Nm disturbance when walking at 1.44 km/h without adjusting the foot placement, and can walk on an unknown 4 cm high stairs and a rotating slope with a maximum inclination of 10°. The method is also adopted to realize fast walking up to 6 km/h.

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.

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.

scholarly journals Universal Walking Control Framework of Biped Robot Based on Dynamic Model and Quadratic Programming

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Xiaokun Leng ◽  
Songhao Piao ◽  
Lin Chang ◽  
Zhicheng He ◽  
Zheng Zhu
Keyword(s):  
Motion Control ◽  
Dynamic Characteristics ◽  
Control Method ◽  
Constraint Equation ◽  
Biped Robot ◽  
Equation System ◽  
Whole Body ◽  
Optimal Controller ◽  
Control Framework ◽  
The Stability

Biped robot research has always been a research focus in the field of robot research. Among them, the motion control system, as the core content of the biped robot research, directly determines the stability of the robot walking. Traditional biped robot control methods suffer from low model accuracy, poor dynamic characteristics of motion controllers, and poor motion robustness. In order to improve the walking robustness of the biped robot, this paper solves the problem from three aspects: planning method, mathematical model, and control method, forming a robot motion control framework based on the whole-body dynamics model and quadratic planning. The robot uses divergent component of motion for trajectory planning and introduces the friction cone contact model into the control frame to improve the accuracy of the model. A complete constraint equation system can ensure that the solution of the controller meets the dynamic characteristics of the biped robot. An optimal controller is designed based on the control framework, and starting from the Lyapunov function, the convergence of the optimal controller is proved. Finally, the experimental results show that the method is robust and has certain anti-interference ability.

Contact-Dependent Balance Stability of Walking Robots

2017 ◽  
Author(s):  
Carlotta Mummolo ◽  
William Z. Peng ◽  
Carlos Gonzalez ◽  
Joo H. Kim
Keyword(s):  
Stability Region ◽  
Balance Control ◽  
Center Of Mass ◽  
Biped Robot ◽  
Walking Robots ◽  
Ground Contact ◽  
Robotic Platform ◽  
Contact Configuration ◽  
The Stability ◽  
Balance Stability

A novel theoretical framework for the identification of the balance stability regions of biped systems is implemented on a real robotic platform. With the proposed method, the balance stability capabilities of a biped robot are quantified by a balance stability region in the state space of center of mass (COM) position and velocity. The boundary of such a stability region provides a threshold between balanced and falling states for the robot by including all possible COM states that are balanced with respect to a specified feet/ground contact configuration. A COM state outside of the stability region boundary is the sufficient condition for a falling state, from which a change in the specified contact configuration is inevitable. By specifying various positions of the robot’s feet on the ground, the effects of different contact configurations on the robot’s balance stability capabilities are investigated. Experimental walking trajectories of the robot are analyzed in relationship with their respective stability boundaries, to study the robot balance control during various gait phases.

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.

Quantifying Segmental Contributions to Center-of-Mass Motion During Dynamic Continuous Support Surface Perturbations Using Simplified Estimation Models

2020 ◽  
Vol 36 (4) ◽  
pp. 198-208
Author(s):  
Alison Schinkel-Ivy ◽  
Vicki Komisar ◽  
Carolyn A. Duncan
Keyword(s):  
Balance Control ◽  
Center Of Mass ◽  
Three Dimensional ◽  
The Body ◽  
Whole Body ◽  
Mass Motion ◽  
Support Surface ◽  
Body Segments ◽  
Body Model ◽  
Full Body

Investigating balance reactions following continuous, multidirectional, support surface perturbations is essential for improving our understanding of balance control in moving environments. Segmental motions are often incorporated into rapid balance reactions following external perturbations to balance, although the effects of these motions during complex, continuous perturbations have not been assessed. This study aimed to quantify the contributions of body segments (ie, trunk, head, upper extremity, and lower extremity) to the control of center-of-mass (COM) movement during continuous, multidirectional, support surface perturbations. Three-dimensional, whole-body kinematics were captured while 10 participants experienced 5 minutes of perturbations. Anteroposterior, mediolateral, and vertical COM position and velocity were calculated using a full-body model and 7 models with reduced numbers of segments, which were compared with the full-body model. With removal of body segments, errors relative to the full-body model increased, while relationship strength decreased. The inclusion of body segments appeared to affect COM measures, particularly COM velocity. Findings suggest that the body segments may provide a means of improving the control of COM motion, primarily its velocity, during continuous, multidirectional perturbations, and constitute a step toward improving our understanding of how the limbs contribute to balance control in moving environments.

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.

Stability Region-Based Analysis of Walking and Push Recovery Control

2021 ◽  
Vol 13 (3) ◽  
Author(s):  
William Z. Peng ◽  
Hyunjong Song ◽  
Joo H. Kim
Keyword(s):  
Sagittal Plane ◽  
Center Of Mass ◽  
Biped Robot ◽  
Optimization Method ◽  
Order System ◽  
Double Support ◽  
Push Recovery ◽  
One Step ◽  
To Come ◽  
Time Required

Abstract To achieve walking and push recovery successfully, a biped robot must be able to determine if it can maintain its current contact configuration or transition into another one without falling. In this study, the ability of a humanoid robot to maintain single support (SS) or double support (DS) contact and to achieve a step are represented by balanced and steppable regions, respectively, as proposed partitions of an augmented center-of-mass-state space. These regions are constructed with an optimization method that incorporates full-order system dynamics, system properties such as kinematic and actuation limits, and contact interactions with the environment in the two-dimensional sagittal plane. The SS balanced, DS balanced, and steppable regions are obtained for both experimental and simulated walking trajectories of the robot with and without the swing foot velocity constraint to evaluate the contribution of the swing leg momentum. A comparative analysis against one-step capturability, the ability of a biped to come to a stop after one step, demonstrates that the computed steppable region significantly exceeds the one-step capturability of an equivalent reduced-order model. The use of balanced regions to characterize the full balance capability criteria of the system and benchmark controllers is demonstrated with three push recovery controllers. The implemented hip–knee–ankle controller resulted in improved stabilization with respect to decreased foot tipping and time required to balance, relative to an existing hip–ankle controller and a gyro balance feedback controller.

scholarly journals ANALYSIS OF DYNAMIC BALANCE CONTROL IN TRANSTIBIAL AMPUTEES WITH USE OF A POWERED PROSTHETIC FOOT

2016 ◽  
Vol 28 (02) ◽  
pp. 1650011
Author(s):  
Shaun C. Resseguie ◽  
Li Jin ◽  
Michael E. Hahn
Keyword(s):  
Balance Control ◽  
Dynamic Balance ◽  
Center Of Mass ◽  
Whole Body ◽  
Mass Motion ◽  
Camera System ◽  
Prosthetic Foot ◽  
Motion Data ◽  
Walking Speeds ◽  
Transtibial Amputees

Powered prosthetic feet (PPF) are designed to provide transtibial amputees (TTA) with active propulsion and range of motion similar to that of the biological limb. Previous studies have demonstrated the PPF’s ability to increase TTA walking speeds while reducing the energetic costs, however, little is known about its effects on dynamic balance control. The purpose of this pilot study was to assess dynamic balance control in TTA subjects during level ground walking and obstacle-crossing tasks. Control subjects ([Formula: see text]) and TTA subjects ([Formula: see text]) were instructed to complete a series of functional walking tasks. The TTA subjects completed the walking protocol twice, first in their passive energy-storing prosthetic foot (ESPF) and again in the prescribed PPF after two weeks of acclimation. Motion data were collected via a 10-camera system with a 53-marker and 15-segment body model. Whole body medial-lateral center of mass motion (displacement and peak velocity) was analyzed and used as a functional indicator of dynamic balance control. Findings indicate no difference in the dynamic balance control of TTA wearing the PPF compared to the ESPF. However, there was an observed trend of walking speed and obstacle height affecting balance control within the groups.

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