Control of physical interaction tasks using pneumatic soft-robots

Abstract:
Compactness, passive (inherent) compliance and low weight are the most important benefits of pneumatic soft-actuators with rotary elastic chambers (REC-actuators). Robots with these natural back-drivable actuators are well suitable for safe physical interaction tasks especially in service and rehabilitation, where human and robots operate in direct contact. In this paper the application of different control strategies for physical interaction of pneumatic soft-robots is considered. For control feedback the current measurements of pressure and joint angle position as well as a force/torque observer based on inverted experimental torque characteristics of the REC-actuators are utilized. An adaptive admittance control with trajectory modification (ACTM) is compared by simulation to an adaptive admittance control with variable stiffness regulation (ACSR) using a model of a planar robot with two rotary joints. Both concepts enable desired force tracking in constraint direction and compliant position control in unconstraint direction. Furthermore the more promising ACSR approach was implemented and validated within an experimental setup using a planar soft-robot with two REC-actuators by tracking even or lightly curved surfaces without knowledge of the environment parameters.