Design, Calibration, and Control of Compliant Force-Sensing Gripping Pads for Humanoid Robots

This paper introduces a pair of low-cost, light-weight, and compliant force-sensing gripping pads used for manipulating box-like objects with smaller-sized humanoid robots. These pads measure normal gripping forces and center of pressure (CoP). A calibration method is developed to improve the CoP measurement accuracy. A hybrid force-alignment-position control framework is proposed to regulate the gripping forces and to ensure the surface alignment between the grippers and the object. Limit surface theory is incorporated as a contact friction modeling approach to determine the magnitude of gripping forces for slippage avoidance. The integrated hardware and software system is demonstrated with an NAO humanoid robot. Experiments show the effectiveness of the overall approach.