Active robot hand compliance using operational space and Integral Sliding Mode Control

Abstract

This paper establishes a novel approach of robust active compliance control for a robot hand via an Integral Sliding Mode Controller (ISMC). The ISMC allows us to introduce a model reference approach where a virtual mass-spring damper system can be used to design a compliant control. In order to allow for practical grasping, we consider the shape of the object to be grasped. Hence, the work exploits a grasping technique via Cylindrical and Spherical coordinate systems due to their simplicity and geometric suitability. The control uses the operational space approach. Thus, the control is split into a task control and a particular optimizing posture control. The experimental results show that target trajectories can be easily followed by the task control despite the presence of friction and stiction while the posture controller maintains a desired finger posture. When the object is grasped, the compliant control will automatically adjust to a specific compliance level. Once a specific compliance model has been achieved, the fixed compliance controller can be tested for a specific scenario. The experimental results prove that the BERUL hand can automatically and successfully attain different compliancy levels for a particular object via the ISMC.