Automated Off-line Generation of Stable Variable Impedance Controllers According to Performance Specifications

Abstract - In this paper, we propose a novel methodology to off-line generate stable Variable Impedance Controllers for any parameter modulation law depending on exogenous signals to the robot, as e.g. the exerted force by the human in a collaborative task. The aim is to find the optimal controller according to a desired trade-off between accuracy and control effort. Each controller is formulated as a polytopic Linear Parameter Varying system consisting on a set of vertex system at the limit operation points. Then, stability and operating properties can be assessed through Linear Matrix Inequalities, from which an optimality index can be obtained. This index is used by a genetic optimisation algorithm to iteratively generate new controller solutions towards the best one. To exemplify our method, we choose a case study of modulation laws for tasks that require a physical interaction between human and robot, and evaluate generated solutions for different trade-offs on a object handover scenario using a 7-DoF WAM robotic manipulator.

Keywords - Compliance and Impedance Control; Linear Parameter Varying (LPV); Linear Matrix Inequalities (LMI); physical Human-Robot Interaction

Extra: Extended Appendix