System Design And Control Strategy Research For The Power Assist Exoskeleton Robot

Exoskeleton robot is a kind of wearable device which can assist and improve human movement. Nowadays, large numbers of scholars focus on exoskeleton because of its significant application value. Some exoskeletons are developed in practical applications. However, domestic researches are still in the laboratory stage, and there are also many problems in theory researches and practical applications. The purpose of our project is to develop a comfortable and convenient exoskeleton robot. Therefore, the control system and the control strategies of the exoskeleton robot are studied in this paper.Stability and reliability are both the foundation of theory researches and the key of practical applications in the robot system development. According to the requirements of exoskeleton, the highly integrated control system is designed in this paper, including DSP+ARM based controller, modular sensors and CANopen based bus communication protocol. All of the basic functions of exoskeleton can be realized utilizing the designed controller and can work without the host computer. Bus interfaces are employed in the modular sensors for the small volume. Meanwhile, the developed CANopen protocol which meets the international standards is easy to expand and exchange.Considering the role of human in the trajectory planning, decomposition velocity control strategy is designed based on the movement recognition of body extremities. Meanwhile, the desired extremities trajectories and the decomposition velocity models are focused. In order to improve the hysteresis of system, the desired velocities of exoskeleton extremities are obtained by the feedback force and body velocity which is estimated by Kalman filtering. For the underactuated problem that three degrees of freedom movements are actuated by two joints in the stance phase, an inverted pendulum model with variable pendulum length is proposed. In this model, torso planar movement can be converted as the pitch of the torso and the variety of the length between the ankle and hip. After then, the desired extremities velocities in the stance phase can be reasonably assigned to the actuated joints.Exoskeleton which is integrated with the control system is assembled. The control system which is embedded in the exoskeleton shell is reliable and convenient. On this basis, experiments are performed including predetermined gait trajectory experiment, swing phase experiment, stance phase experiment, load test, continuous walking experiment and adaptability test of complicated environment of stairs, slope and lawn. Reliability of the control system and feasibility of the control strategy in this paper are verified by means of experiments. The results meet the application requirements.