Variable Impedance Control for Safety and Usability in Telemanipulation

Abstract

In recent years, haptic telemanipulation has been introduced to control robots remotely with an input device that generates force feedback. Compliant control strategies are needed to ensure safe interaction between humans and robots. Accurate and precise manipulation requires a stiff setup of the impedance parameters, while safety demands for low stiffness. This paper proposes an impedance-based control approach that combines stiff manipulation with a safety mechanism that adapts compliance when required. We introduce three system modes: operation, safety and recovery mode. If the external forces exceed a defined force threshold, the system switches to the compliant safety mode. A user input triggers the recovery process that increases the stiffness back to its nominal value. This paper suggests an energy tank, which limits the change of stiffness to ensure stability during recovering phase. We validate the functionality of this approach using a real telemanipulation setup and show that the suggested tank enables recovery even from large displacements.