Development and Control of a 'Soft-Actuated' Exoskeleton for Use in Physiotherapy and Training

Full or partial loss of function in the upper limb is an increasingly common due to sports injuries, occupational injuries, spinal cord injuries, and strokes. Typically treatment for these conditions relies on manipulative physiotherapy procedures which are extremely labour intensive. Although mechanical assistive device exist for limbs this is rare for the upper body. In this paper we describe the construction and testing of a seven degree of motion prototype upper arm training/ rehabilitation (exoskeleton) system. The total weight of the uncompensated orthosis is less than 2 kg. This low mass is primarily due to the use of a new range of pneumatic Muscle Actuators (pMA) as power source for the system. This type of actuator, which has also an excellent power/weight ratio, meets the need for safety, simplicity and lightness. The work presented shows how the system takes advantage of the inherent controllable compliance to produce a unit that is extremely powerful, providing a wide range of functionality (motion and forces over an extended range) in a manner that has high safety integrity for the patient. A training control scheme is introduced which is used to control the orthosis when used as exercise facility. Results demonstrate the potential of the device as an upper limb training, rehabilitation and power assist (exoskeleton) system.