Upper Limb Rehabilitation System Based On Functional Electrical Stimulation

With the increase of the domestic aging population,the number of associated strokes is also increasing year by year.Stroke has become the leading cause of death and disability among the elderly in China;1.5 to 2 million stroke patients survive each year,with three-quarters of them having varying degrees of motor dysfunction.Rehabilitation treatment is an effective way to alleviate patients’ motor dysfunction and restore voluntary movement ability.However,there is a shortage of rehabilitation medical resources in China,and the traditional rehabilitation process involves rehabilitation physicians or mechanical exoskeleton equipment to assist stroke patients in rehabilitation exercises,which is labor-intensive and requires high requirements for rehabilitation sites,limiting the popularity of rehabilitation therapy.Functional electrical stimulation has the advantages of high safety,wearable,easy to use and a wide range of use scenarios.Upper limb rehabilitation equipment based on functional electrical stimulation provides an effective rehabilitation method for stroke patients.Most of the functional electrical stimulation devices currently in clinical use are open-loop controlled,with limited therapeutic effect and control accuracy.In order to improve the control accuracy and therapeutic effect,this thesis designs a closed-loop torque control system for the upper limb system to achieve precise control of the musculoskeletal output torque.This thesis focuses on the following research elements.(1)According to the structural properties and motor properties of musculoskeletal,the Hammerstein model is improved by introducing hysteresis curves and time lag function links to establish an empirical musculoskeletal model.The parameters of the musculoskeletal system model are identified by iterative least squares method,and the experimental results show that the model can better characterize the human musculoskeletal system.(2)Uncertainty of musculoskeletal system leads to the degradation of control accuracy.In this thesis,we fuse the Active Disturbance Rejection Controller,inverse model linearization method and time-lag matching method,and estimate and compensate the disturbance and unmodeled dynamics to achieve the accurate control of muscle output force.The Active Disturbance Rejection Controller design is carried out for the upper limb rehabilitation system,and the inference is justified for parameter rectification.(3)The overall design of the upper limb rehabilitation system was proposed.In the hardware platform design,the components were firstly selected,and then the multiple-channel electrical stimulators with boost power supply module is designed.In the software system,threshold voltage test,musculoskeletal model and parameter identification and Active Disturbance Rejection Controller algorithm are implemented;and the system construction and testing are completed.(4)Numerical simulation and experimental analysis are carried out.According to the simulation data,the experimental verification is carried out in the upper limb rehabilitation system designed in this thesis,and the trajectory of the step signal and sine wave signal under different stimulation intensities was tracked.By comparing the control effects of the Active Disturbance Rejection Controller and the PID controller,the results show that the Active Disturbance Rejection Controller has better control accuracy and anti-interference ability.