External six-bar mechanism rehabilitation device for index finger: Development and shape synthesis

Abstract

This work proposes a novel external Stephenson-III six-bar mechanism-based rehabilitation device. This device has been designed to rehabilitate the patient’s finger for the action of grabbing, also known as flexion and extension. A predefined trajectory is used to synthesize the mechanism using TeachingLearning-Optimization algorithm (TLBO) and Particle swarm optimization algorithm (PSO). The trajectory data was obtained after image processing by grabbing a particular object 30 times to record the flexion and extension motion of the index finger. An optimization problem was formulated and results of TLBO and PSO were compared. The mechanism obtained from TLBO algorithm was deemed better in terms of precision and feasible configuration. Using clinical biomechanical data for flexion/extension of index finger, position and static force analysis are performed. The CAD model of the mechanism was then tested for feasibility in a CAD/Software. Excess mass was removed using topology optimization and a 20% mean reduction for every link was achieved. An index finger rehabilitation device employing an external six-bar mechanism was obtained, that would help a patient with motor control loss to rehabilitate and bring normalcy to life. The design of exoskeleton was able to match the trajectory of the index. Shape synthesis ensured a 20% reduction in overall mass of the linkages.