Dynamic Whole-Body Motion Generation Under Rigid Contacts and Other Unilateral Constraints

Abstract

Abstract-The most widely-used technique to generate wholebody motions on a humanoid robot accounting for various tasks and constraints is the inverse kinematics. Based on the taskfunction approach, this class of methods makes possible the coordination of the robot movements to execute several tasks in parallel and account for the sensor feedback, in real-time thanks to the low computation cost. To some extent, it also enables dealing with some of the robot constraints (e.g. joint limits or visibility) and managing the quasi-static balance of the robot. In order to fully use the whole range of possible motions, this paper proposes to extend the task-function approach to handle the full dynamics of the robot multi-body along with any constraint written as equality or inequality of the state and control variables. The definition of multiple objectives is made possible by ordering them inside a strict hierarchy. Several models of contact with the environment can be implemented in the framework. We propose a reduced formulation of the multiple rigid planar contact that keeps a low computation cost. The efficiency of this approach is illustrated by presenting several multi-contact dynamic motions in simulation and on the real HRP-2 robot.

Optimization-based locomotion planning, estimation, and control design for the atlas humanoid robot

“…Several researchers have recently explored using QPs to control bipedal systems both in simulation [1,17,48,41,39,26] and in hardware [2,32,60,36]. As in our formulation, these optimizations typically employ low-dimensional dynamic quantities such as center of mass (COM) acceleration [1], rate of change of linear and angular momenta [48,32,39], zero moment point (ZMP) [60], or canonical walking functions [2], where the QP cost consists of a weighted distance from a reference value computed using a simple PD control rule [1,48,32].…”

On Weight-Prioritized Multitask Control of Humanoid Robots

“…inverse dynamics control, operational or task function space control... raises a number of challenging problems [3]- [6]. Typical such problems include simultaneous resolution of redundancy and underactuation, or actuation through frictioncone-constrained unilateral contact forces.…”

Whole-body model-predictive control applied to the HRP-2 humanoid

“…Once more, the computation cost of the method is kept low by considering only the instantaneous linearization of the system at the current time instant. This more-complex OSID model provides more expressiveness than IK: for example, it is possible to consider instantaneous balance criteria like the ZMP on flat terrain [6] or the positivity of the contact forces in case of multiple contacts [7]. However, the instantaneous linearization once more limits the range of expressiveness.…”