ArXiv | 2019
Evaluation of a 1-DOF Hand Exoskeleton for Neuromuscular Rehabilitation
Abstract
A low-cost 1-DOF hand exoskeleton for neuromuscular rehabilitation has been designed and assembled. It consists of a base equipped with a servo motor, an index finger part, and a thumb part, connected through three gears. The index part has a tri-axial load cell and an attached ring to measure the finger force. An admittance control scheme was designed to provide intuitive control and positive force amplification to assist the user s finger movement. To evaluate the effects of different control parameters on neuromuscular re-sponse of the fingers, we created an integrated exoskeleton-hand musculo-skeletal model to virtually simulate and optimize the control loop. The exo-skeleton is controlled by a proportional derivative controller that computes the motor torque to follow a desired joint angle of the index part, which is obtained from inverse kinematics of a virtual end-effector mass driven by the finger force. We conducted parametric simulations of the exoskeleton in action, driven by the user s closing and opening finger motion, with different proportional gains, end-effector masses, and other coefficients. We com-pared the interaction forces between the index finger and the ring in both passive and active modes. The best performing assistive controller can re-duce the force from around 1.45N (in passive mode) to only around 0.52N, more than 64% of reduction. As a result, the muscle activations of the flex-ors and extensors were reduced significantly. We also noted the admittance control scheme is versatile and can also provide resistance (e.g. for strength training) by simply increasing the virtual end-effect mass.