Torque mode control of a Bowden cable-driven assistive system

A cable-driven actuating system is proposed in this paper. The proposed system is attractive for rehabilitation systems because the weight of the actuator is not imposed on the human body. Since the end-effector and the actuators are connected by Bowden cables, the humans are allowed to freely move in a certain range while being assisted. However, it is a challenge to account for the variable friction of the Bowden cable and the inertia and friction of the actuator in the design of control algorithms. In this paper, a hierarchical control strategy is adopted to control the proposed cable-driven actuating system. To determine the reference trajectory of the motor in real-time, a sensor fusion method based on a kinematic Kalman filter with MEMS accelerometers is proposed. By the proposed control methods, the cable-driven actuating system realizes a precise force-mode actuation. The system performance is evaluated by experiments.