Fuzzy Sliding Mode Control of a Bio-Inspired Exoskeleton Robot in Pick and Place Task with Obstacle Avoidance

In daily life activities, pick and place task is one of the most common human arm movements. This task is usually performed by human in the presence of obstacles. In order to help the disable people during this daily movement, rehabilitation exoskeletons are utilized. In this paper, the pick and place problem is formulated and solved for an exoskeleton robot that is worn by a subject who needs assistance for this task with the existence of obstacles. For a specific movement in the transverse plane in which the task occurs most frequently, the kinematic and dynamic modeling of an exoskeleton has been established. The movement of the end-effector is directed with two attractive and repulsive potential field in the neighborhood of desired final position and obstacles, respectively. A fuzzy sliding mode controller is designed to control the exoskeleton in obstacle avoidance and reaching the target. The saturation function is used to reduce the chance of chattering in the systems response. The fuzzy logic is applied to tune the coefficient of sliding mode surface. The model is designed to be studied in both problems of regulation and tracking. In order to verify the theoretical results, the experimental setup by human arm has been planned and the kinematic data is acquired using motion capture system. The comparison between the experimental and simulation results show the acceptable adaptation.