Adaptive trajectory control to achieve smooth interaction force in robotic rehabilitation device

© 2014 The Authors. One of the main objectives of a successful lower limb robotic rehabilitation device is to obtain a smooth human machine interaction in different phases of gait cycle at the interaction point. The input (interaction force, Joint angle) and output (impedance) relationship of the control system is nonlinear. This paper proposes a fuzzy rule based controller to be used to control the interaction force at the patient exoskeleton interaction point. In achieving the objective, impedance, driver torque and angular velocity have been modulated in a way such that there is a reduction of interaction force. Minimum interaction force at the interaction point and tracking the defined gait trajectory with minimum error are set as benchmark to evaluate the performance in many tasks. In this paper there is an evaluation of what degree of impedance is ideal for what type of interaction force and joint angle to maintain a trajectory tunnel. This paper describes the control architecture of one Degree of freedom lower limb exoskeleton that has been specifically designed in order to ensure a proper trajectory control for guiding patient's limb along an adaptive reference gait pattern. The proposed methodology satisfies all the desired criteria for the device to be an ideal robotic rehabilitation device