Force control based on biarticular muscle system and its application to novel robot arm driven by planetary gear system

We have suggested a novel statics and force control can be achieved in a more simple way by using the biarticular muscle coordinate. In order to verify these characteristics, a robot arm with two links that are driven by planetary gear is developed in this paper. First, the complicated muscle structure is simplified as a three-pair six-muscle model including the biarticular muscle. Then based on the configuration, statics at the endeffector is redefined and a force control algorithm is suggested. The suggested statics and force control have the advantage of its simplicity. Then a novel robot arm to emulate the biarticular muscle is developed. A planetary gear system is adopted to transfer torque generated by a motor to two joints. Unnecessary coupling caused by the planetary gear is removed by disturbance observer control. Experiments done by the robot arm verifies the effectiveness of the suggested statics and force control.