Kinematic control of redundant manipulators: generalizing the task priority framework to inequality tasks

International audienceThe redundant mechanical systems like humanoid robots are designed to fulfill multiple tasks at a time. A task, in velocity-resolved inverse kinematics, is a desired value for a function of the robot configuration that can be regulated with an Ordinary Differential Equation. When facing simultaneous tasks, the corresponding equations can be grouped in a single system, or better, sorted in priority and solved each in the solutions set of higher priority tasks. This elegant framework for hierarchical task regulation has been implemented as a sequence of Least Squares problems. Its limitation lies in the handling of inequality constraints, which are usually transformed into more restrictive equality constraints through potential fields. In this paper, we propose a new prioritized task regulation framework based on a sequence of quadratic programs (QP) that removes the limitation. At the basis of the proposed algorithm is a study of the optimal sets resulting from the sequence of QPs. The algorithm is implemented and illustrated in simulation on the humanoid robot HRP-2