Safety-based Stable Variable Impedance Controller for Interaction Tasks Involving Human Body Surfaces

Abstract - This paper contributes to the design of controllers to enhance safety in tasks involving contact with a human body surface using a robotic manipulator, particularly we use bathing and showering as examples. Our solution consists on a variable impedance controller with safety-based parameter modulation laws that consider both free space motion and contact phases of the interaction. To validate our controllers, we also introduce a novel formulation for variant impedance controllers in terms of a Takagi-Sugeno fuzzy model that allows to off-line assess stability and optimality through Linear Matrix Inequalities. A comparison against a state-of-art method in simulated and real scenarios is provided using the 7-DoF WAM robotic manipulator. In both cases, the proposed controller shows the best trade-off without compromising safety nor stability.

Keywords - Safety; physical Human-Robot Interaction; Compliance and Impedance Control