Powered Ankle Joint Intelligent Prosthetic Control Theory And System Design

Intelligent prosthesis has been a heated research subject in the fields of robotics and biomedical engineering.Intelligent lower limb prosthesis is the best device compensating for amputees motor function.Now the most of intelligent prostheses entering the market only focus on the function of knee joint.It is rare to see the intelligent prosthesis which focuses on the function of ankle joint. Moreover,the most of ankle prostheses are passive ones which can not provide power but only passively assist knee joint to complete the basic function of walking. Besides,the passive ankle prosthesis is easily worn and poor somatosensory.In addition,it can not follow the healthy limb in a natural way.This thesis is devoted to studying the control methods and developing a powered ankle joint intelligent prosthesis controller,the main work is as follows:Firstly,VICON MX(Sports-captured System) is used in gait experiment. We analyzed the periodic changes of ankle joint angle, ground reaction force from people walking on the ground. These characteristics of ankle movement provide theoretical basis and data for the piecewise linearization and FSM control method of powered ankle joint intelligent prosthesis.Secondly, this thesis emphatically analyzes the characteristics of ankle joint angle and torque,and summarizes the rules. Multiple levels control method is applied in powered ankle prosthesis system. In the upper level control method,We use least square method to get different events of ankle joint angle and control indexes as well.Then,finite-state machine control method is applied in classifying these events and developing control strategy for each of the event,and the information collected by sensors is regarded as trigger event of FSM;As for bottom level control method,we apply PID method in controlling a DC motor,and we use fuzzy algorithm to tune parameters of PID which are based on the ankle angle deviation and ankle angle deviation rate.In addition,the ankle angle is used as the negative feedback signal to increase stability of the powered ankle joint control system.At last,the feasibility of multiple levels control method has been verified by trials.Thirdly, the powered ankle joint intelligent prostheses controller is designed,whose core is TMS320F2812. The hardware circuit of controller includes power module, reset module, sensor module, serial port communication module and DC motor driving module. In addition, software is designed elaborately. In summary, The controller runs steadily, has high controlling precision and fast response speed as well, which can meet the controlling requirement of powered ankle joint.At last, the main work of this thesis is summarized,and the problems of the design are analyzed carefully, and the innovative points are summarized.The research orientation of powered ankle joint intelligent prosthesis is put forward.