Development and control of a robotic lower limb exoskeleton for paraplegic patients

Robot-assisted therapy has gained wide attention in rehabilitation engineering, allowing patients with lower limb motor disorders to perform repeatable and consistent upright bipedal walking. The goal of this paper is to develop a novel wearable powered exoskeleton that enables the paraplegic to perform basic daily movements for active rehabilitation training of lower limbs. Mechanical structure and driving devices of the exoskeleton are reasonably designed and selected to ensure natural interaction with the user and provide sufficient driving torques in the course of walking. In order to avoid unwanted interaction forces between the exoskeleton and the patient, the passive exoskeleton testing system is proposed to measure and record various postures as the reference trajectories. In addition, a cascaded proportional-integral-derivative controller is designed to complete walking assistance tasks in passive control modes. Four typical trajectory tracking tasks are carried out for the sake of evaluating the accuracy and effectiveness of the proposed control strategy. Further experiments were conducted by a healthy subject wearing the rehabilitation exoskeleton to perform sit-to-stand and level walking, and the results demonstrated that the developed robot-assisted system had the natural period and favorable response patterns.