Modeling Of Motor-unit In Biomimetic Control Of Prosthetic Hands

This research studies the modeling of motor-unit in the biomimetic control of prosthetic hands,mainly discussing how to improve the performance of prosthetic hands through model-based control.Model-based control can be divided into two aspects: control strategy and execution unit.In the terms of control strategy,the slow simulation platform of single-joint spinal cord reflex was firstly established based on the "neuromorphic model",which simulates the single-joint virtual finger pulled by muscles.The movement of the virtual finger reflects the opening and closing of the prosthetic hand.Based on this platform,the experimental environment of the hardware prosthetic hand control system can be reproduced,and more micro-details can be observed.In addition,this study attempts to optimize the control strategy.The results of stretch reflex experiment showed that extreme fibers’ differentiation had a negative effect on the stability and anti-interference capability of the virtual finger.The recovery time and variance of joint displacement were significantly improved after the perfection of muscle force-length characteristics.Based on the slow simulation calibration experiment,the accurate calculation formula of Lce was deduced,and the feedback adjustment error was reduced.The formula was applied to the hardware control system of the prosthetic hand.The application results of the force bar experiment were shown in this paper.As for the force execution module,the linear motor with force feedback was used to build a force follower,but because of its conflict with the feedback regulation mechanism of the muscle spindle,the position control scheme of linear motor was proposed.Through the stiffness experiments,the feasibility of the scheme and its advantage in the establishment of small stiffness output are proved: the lower limit of stiffness output is 17.69N/m,which can better cover the minimum stiffness of real hands than the original torque motor.However,there are still some shortcomings in establishing high stiffness,and further exploration and tests are needed.