Fuzzy adaptation impedance of a 6 DOF parallel robot: application to peg in hole insertion

This paper deals with fuzzy adaptation of robot impedance to achieve a peg in hole insertion task. This task is performed by a 6 DOF (degree of freedom) parallel robot equipped with force sensors. The fuzzy controller is not trivial to derive because of the system nonlinearity and the high degree of coupling. Therefore the control scheme is based on the system features knowledge and a build up methodology to derive the optimal rule base which achieves the desired performance and the closed loop stability. Thus the main goal of the fuzzy controller is the online adaptation of the robot impedance using a nonlinear robot behavior model expressed as an IF-THEN rules base. The insertion task is performed with an external force control where the fuzzy controller simulates an adaptive robot impedance. Finally we provide an experimental comparison between an impedance control and a fuzzy external force control which is performed first as articular space control and second as operational space control