Development of Human-inspired Robotic Exoskeleton (HuREx) designed for Lower-limb Gait Rehabilitation for Stroke Patients

Abstract

Stroke is one of the leading cause of physical disability in New Zealand and many suffer paralysis to their limbs. Unfortunately, fewer than 50% of survivors regaining their independence after 6 months particularly due to the inability to walk properly. One of the reason for the slow recovery of the gait function is that the current rehabilitation technique used is labour intensive and time consuming for the therapists and difficult to perform it effectively. In order to improve the gait rehabilitation process, robot assisted gait rehabilitation has gained much interest over the past years. There have been many prototypes and commercial products for the robot assisted rehabilitation, but many had limitations. One of which is being bulky and had uncomfortable attachment for the patients. Improper attachment not only create uncomfortable feeling and pain for the patient but also causes human-robot axis misalignment which could lead to an injury with long term use. Another limitation is the lack of mechanical compliance which is the key to improve the safety of the operation and comfort for the patient. In order to address the limitations identified, a new robot orthosis, Human-inspired Robotic Exoskeleton (HuREx) was developed. HuREx consists of a compact exoskeleton parts custom fit for each individual patient manufactured using a rapid prototyping technique. Pneumatic Muscle Actuators (PMA) were used as they exhibit natural compliance and configured antagonistically. The design of the orthosis and the actuation mechanism made the system highly nonlinear. Therefore, an advanced model-based feedforward (FF) controller was designed and implemented to achieve the speed and accuracy of the response required. Many experiments were carried out to observe the performance and verify the proof of concept. The contributions of this research are the development of new robotic exoskeleton device designed to be light weight, comfortable and safe to use for gait rehabilitation for stroke patients, which were lacking in the existing devices. Another contribution is the establishment of new manufacturing technique that allow custom exoskeleton component for each individual patient. Finally the development of advanced model-based FF controller that achieves fast and accurate tracking performance.