The Design and Simulation of a Fuzzy Logic-Controlled Upper-body Exoskeleton for Lower-Limb Paraplegics Using Swing Through Gait Ambulation

Abstract

Currently, most of the research activities and the resulting commercial products offer motorized lower-limb exoskeletons that assist paraplegics in ambulating while standing up. However, there exist numerous gaiting techniques that enable the paralyzed to move using the upper extremities. This research aims for the development of an upper limb assistive technology that enables paraplegics to ambulate using a supported Swing Through Gait (STG) technique. The STG technique is known to require significant upper-body strength and superior balancing abilities during the swing phase. The challenge in the swing phase is due to the small contact area with the ground, represented by the ends of the crutches, and the large torques resulting from carrying the body and the swinging of the torso and legs. This article presents a control system that can be deployed onto an upper-limb rehabilitation exoskeleton that supports the STG ambulation technique. The controller is designed to recreate the STG using a rigid body dynamics model with a fuzzy logic controller guiding the motion of the shoulders and elbows. The controller is then calibrated and verified with experimental data measured from a spinal cord injured subject with complete thoracic lesion at T2 that relies on the STG pattern. The controller is further augmented by adding a failure detection and correction mode aimed at preventing falls and injuries in paraplegic users. The developed controller shows that it can control actuators in an exoskeleton to ambulate using the STG technique, detect falls/anomalies in the motion, and correct the falls to restore the intended trajectory. This work demonstrates that the proposed controller can be extended to an upper-limb exoskeleton to help support and rehabilitate paraplegic patients using the STG technique.