scholarly journals Quadrupedal Robots Whole-Body Motion Control Based on Centroidal Momentum Dynamics

2019 ◽  
Vol 9 (7) ◽  
pp. 1335 ◽  
Author(s):  
Mingmin Liu ◽  
Daokui Qu ◽  
Fang Xu ◽  
Fengshan Zou ◽  
Pei Di ◽  
...  
Keyword(s):  
Inverse Dynamics ◽  
Rate Of Change ◽  
Body Motion ◽  
Whole Body ◽  
Quadratic Program ◽  
Control Task ◽  
Joint Torques ◽  
Reaction Forces ◽  
Real Hardware ◽  
Capture Point

In this paper, we demonstrate a method for quadruped dynamic locomotion based oncentroidal momentum control. Our method relies on a quadratic program that solves an optimalcontrol problem to track the reference rate of change of centroidal momentum as closely as possiblewhile satisfying the dynamic, input, and contact constraints of the full quadruped robot dynamics.Given the desired footstep positions, the according reference rate of change of the centroidalmomentum is formulated as a feedback control task derived from the CoM motions of a simplifiedmodel (linear inverted pendulum) based on Capture Point dynamics. The joint accelerations and theGround Reaction Forces(GRFs) outputted from the quadratic program solver are used to calculatethe desired joint torques using an inverse dynamics algorithm. The performance of the proposedmethod is tested in simulation and on real hardware.

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.

scholarly journals Inverse and forward dynamics: models of multi–body systems

2003 ◽  
Vol 358 (1437) ◽  
pp. 1493-1500 ◽  
Author(s):  
E. Otten
Keyword(s):  
Inverse Dynamics ◽  
Temporal Patterns ◽  
Forward Dynamics ◽  
Muscle Forces ◽  
Complex Behaviour ◽  
Joint Torques ◽  
Advantages And Disadvantages ◽  
Reaction Forces ◽  
Internal Forces ◽  
Multi Body

Connected multi–body systems exhibit notoriously complex behaviour when driven by external and internal forces and torques. The problem of reconstructing the internal forces and/or torques from the movements and known external forces is called the ‘inverse dynamics problem’, whereas calculating motion from known internal forces and/or torques and resulting reaction forces is called the ‘forward dynamics problem’. When stepping forward to cross the street, people use muscle forces that generate angular accelerations of their body segments and, by virtue of reaction forces from the street, a forward acceleration of the centre of mass of their body. Inverse dynamics calculations applied to a set of motion data from such an event can teach us how temporal patterns of joint torques were responsible for the observed motion. In forward dynamics calculations we may attempt to create motion from such temporal patterns, which is extremely difficult, because of the complex mechanical linkage along the chains forming the multi–body system. To understand, predict and sometimes control multi–body systems, we may want to have mathematical expressions for them. The Newton–Euler, Lagrangian and Featherstone approaches have their advantages and disadvantages. The simulation of collisions and the inclusion of muscle forces or other internal forces are discussed. Also, the possibility to perform a mixed inverse and forward dynamics calculation are dealt with. The use and limitations of these approaches form the conclusion.

Efficient ZMP Formulation and Effective Whole-Body Motion Generation for a Human-Like Mechanism

2008 ◽  
Author(s):  
Joo H. Kim ◽  
Yujiang Xiang ◽  
Rajankumar Bhatt ◽  
Jingzhou Yang ◽  
Hyun-Joon Chung ◽  
...  
Keyword(s):  
Dynamic Balance ◽  
Body Motion ◽  
Whole Body ◽  
Motion Generation ◽  
Standing Posture ◽  
Upright Standing ◽  
Task Requirements ◽  
Reaction Forces ◽  
Zero Moment ◽  
Physics Based Simulation

An approach of generating dynamic biped motions of a human-like mechanism is proposed. An alternative and efficient formulation of the Zero-Moment Point for dynamic balance and the approximated ground reaction forces/moments are derived from the resultant reaction loads, which includes the gravity, the externally applied loads, and the inertia. The optimization problem is formulated to address the redundancy of the human task, where the general biped and task-specific constraints are imposed depending on the task requirements. The proposed method is fully predictive and generates physically feasible human-like motions from scratch; it does not require any input reference from motion capture or animation. The resulting generated motions demonstrate how a human-like mechanism reacts effectively to different external load conditions in performing a given task by showing realistic features of cause and effect. In addition, the energy-optimality of the upright standing posture is numerically verified among infinite feasible static biped postures without self contact. The proposed formulation is beneficial to motion planning, control, and physics-based simulation of humanoids and human models.

Effect of Having A-Priori Knowledge of the Floor's Contaminant Condition on the Biomechanics of Slips

2002 ◽  
Vol 46 (13) ◽  
pp. 1181-1185 ◽  
Author(s):  
Rakié Cham ◽  
Brian Moyer ◽  
Mark S. Redfern
Keyword(s):  
A Priori ◽  
Young Male ◽  
Body Motion ◽  
Whole Body ◽  
A Priori Knowledge ◽  
Heel Contact ◽  
Reaction Forces ◽  
Hip Flexion ◽  
Gait Disturbances ◽  
Priori Knowledge

Injuries and deaths are often the result of slips/falls. The perceived danger of slipping affects gait biomechanics. This paper investigated the effect of having a-priori knowledge of the floor's contaminant condition on the biomechanics of slips. Five healthy young male subjects donned a safety harness and walked across a walkway, while ground reaction forces and whole body motion were recorded bilaterally at 60 Hz. Slips on soapy floors occurred under 3 “knowledge” conditions: (1) unexpected slips, (2) slips when uncertain of the contaminant condition, and (3) slips when walking onto known contaminated floors. in (2) and (3), i.e. anticipation of slippery surfaces, subjects generated proactive reactions (reduced stance duration and foot angle at heel contact as well as greater hip flexion) compared to unexpected conditions in (1). Those reactions reduced slip potential but also minimized gait disturbances (reduced slip distance and sliding velocity of the heel) when a slip occurred.

Kinesiological Factors in Vertical Jump Performance: Differences Within individuals

1997 ◽  
Vol 13 (1) ◽  
pp. 45-65 ◽  
Author(s):  
Luis F. Áragón-Vargas ◽  
M. Melissa Gross
Keyword(s):  
Vertical Jump ◽  
Video Data ◽  
Whole Body ◽  
Jump Performance ◽  
Joint Torques ◽  
Vertical Jumping ◽  
Single Subjects ◽  
Negative Impulse ◽  
Reaction Forces ◽  
Coordination Patterns

The purpose of this study was to examine the changes in both the coordination patterns of segmental actions and the dynamics of vertical jumping that accompany changes in vertical jump performance (VJP) occurring from trial to trial in single subjects. Ground reaction forces and video data were analyzed for 50 maximal vertical jumps for 8 subjects. It was possible to predict VJP from whole-body or even segmental kinematics and kinetics in spite of the small jump performance variability. Best whole-body models included peak and average mechanical power, propulsion time, and peak negative impulse. Best segmental models included coordination variables and a few joint torques and powers. Contrary to expectations, VJP was lower for trials with a proximal-to-distal sequence of joint reversals.

Study on kinematics and inverse dynamics of legged mobile manipulator for determining feet-terrain reaction forces and joint torques

2018 ◽  
Vol 233 (9) ◽  
pp. 3117-3136
Author(s):  
Kondalarao Bhavanibhatla ◽  
Dilip Kumar Pratihar
Keyword(s):  
Power Consumption ◽  
Inverse Dynamics ◽  
Kinematic Model ◽  
High Mobility ◽  
General Purpose ◽  
Robotic System ◽  
Mobile Manipulator ◽  
Space Applications ◽  
Joint Torques ◽  
Reaction Forces

Legged mobile manipulator is a robotic system that consists of a serial manipulator rigidly mounted on a multi-legged platform. Its high mobility and dexterity makes this robotic system more suitable to be used in disaster management and space applications, where there will be an uneven and unstructured terrain. However, its high power consumption and low stability under external disturbances are the challenges to be solved. In this paper, an attempt is made to determine the feet-terrain reaction forces and joint actuating torques, which ensures the minimum power consumption. Initially, the kinematic model of the robotic system is developed using general-purpose rigid body analysis. Newton–Euler approach is then utilized to formulate the coupled dynamics of this multi-body system. The developed inverse dynamics model considers the inertial effects of the manipulator and moving legs on the trunk body and stationary legs. However, it has no unique solution due to its high redundancy. Therefore, it has been formulated as an optimization problem in order to minimize the power consumption after satisfying some functional constraints. The performance of the developed approach has been tested on computer simulations. The results show that the developed model can efficiently study the kinematics and dynamics of the legged mobile manipulator and also explain the nature of shifting of center of gravity of the combined robotic system due to the movement of the manipulator links. The developed model is a generalized one and it can be used for carrying out stability analysis and designing suitable controller for the combined robotic system.

Balancing While Executing Competing Reaching Tasks: An Attractor-Based Whole-Body Motion Control System Using Gravitational Stiffness

2016 ◽  
Vol 13 (01) ◽  
pp. 1550046 ◽  
Author(s):  
Federico L. Moro
Keyword(s):  
Motion Control ◽  
Physical Simulation ◽  
Torque Control ◽  
Body Motion ◽  
Whole Body ◽  
Entire Body ◽  
Joint Torques ◽  
Floating Base ◽  
Wide Range ◽  
Low Dimensional

Whole-body control (WBC) systems represent a wide range of complex movement skills in the form of low-dimensional task descriptors which are projected on to the robot’s actuator space. Using these methods allow to exploit the full capabilities of the entire body of redundant, floating-base robots in compliant multi-contact interaction with the environment, to execute any single task and simultaneous multiple tasks. This paper presents an attractor-based whole-body motion control (WBMC) system, developed for torque-control of floating-base robots. The attractors are defined as atomic control modules that work in parallel to, and independently from the other attractors, generating joint torques that aim to modify the state of the robot so that the error in a target condition is minimized. Balance of the robot is guaranteed by the simultaneous activation of an attractor to the minimum effort configuration, and of an attractor to a zero joint momentum. A novel formulation of the minimum effort is proposed based on the assumption that whenever the gravitational stiffness is maximized, the effort is consequently minimized. The effectiveness of the WBMC was experimentally demonstrated with the COMAN humanoid robot in a physical simulation, in scenarios where multiple conflicting tasks had to be accomplished simultaneously.

A Least-Squares Estimation Approach to Improving the Precision of Inverse Dynamics Computations

1998 ◽  
Vol 120 (1) ◽  
pp. 148-159 ◽  
Author(s):  
A. D. Kuo
Keyword(s):  
Least Squares ◽  
Inverse Dynamics ◽  
Weighted Least Squares ◽  
Euler Method ◽  
Measured Data ◽  
Joint Torque ◽  
Ground Reaction Forces ◽  
Joint Torques ◽  
Wide Range ◽  
Reaction Forces

A least-squares approach to computing inverse dynamics is proposed. The method utilizes equations of motion for a multi-segment body, incorporating terms for ground reaction forces and torques. The resulting system is overdetermined at each point in time, because kinematic and force measurements outnumber unknown torques, and may be solved using weighted least squares to yield estimates of the joint torques and joint angular accelerations that best match measured data. An error analysis makes it possible to predict error magnitudes for both conventional and least-squares methods. A modification of the method also makes it possible to reject constant biases such as those arising from misalignment of force plate and kinematic measurement reference frames. A benchmark case is presented, which demonstrates reductions in joint torque errors on the order of 30 percent compared to the conventional Newton–Euler method, for a wide range of noise levels on measured data. The advantages over the Newton–Euler method include making best use of all available measurements, ability to function when less than a full complement of ground reaction forces is measured, suppression of residual torques acting on the top-most body segment, and the rejection of constant biases in data.

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