Motion Pattern Recognition And Control Of Active Knee Prosthesis

High-performance knee prosthesis provides a powerful guarantee for transfemoral amputee.It can help them restoring their normal function and sending them back to society. In recentdecades, transfemoral prostheses have changed from purely mechanical systems tomicroprocessor control systems. The commercial transfemoral prostheses remain limited toenergetically passive devices. The prostheses can achieve the function of level ground walking,but in the case of asymmetric gait affect stump muscle and skeleton. Active knee prosthesis canprovide assistance in stance phase and complete extension in swing phase using motor power.The control signal acquisition and joint angle anthropomorphic character is the importantguarantee in control accuracy of active knee prosthesis. Motion information acquisition systemof affected-side is established. The system is used to recognized motion pattern of typicalcyclical movement. The control method of active knee prosthesis is studied based on Finite StateMachine (FSM). The main content of the dissertation could be presented as follows:1. VICON MX system is used to capture five typical cyclical movements. The location ofeach mark point is obtained. The range of hip joint, knee joint and ankle joint angle is collected.3D force plates AMTI and Novel Pedar-X is used to measure ground reaction force of five gaits.The gait cycle is divided into different phases based on force data. The lower limb joint angle ofamputee who wears passive knee prosthesis is gathered. The angle of sound-side and affect-sideis compared. The result is that wearing passive knee prosthesis is not only cause asymmetricalgait, but also put extra pressure on sound side.2. The3D model of human is built using Solidworks, which based on theory of humansegmented in ergonomics. Kinematics of lower limb is analyzed by COSMOSMotion. The jointangle data is used in3D model as input signal. Angular velocity and angular acceleration iscalculated. The lower limb is divided into three parts and each part is rigid model. Dynamicequation is established based on Newton’s second law and Newton-Euler equation. Based on thisDynamic equation joint moment and power is computed. Kinetics of lower limb is analyzed.3. The sensor system of active knee prosthesis is designed. Motion information and footpressure is collected. The sensor system is composed of accelerometer and gyroscopes, whichused to obtain motion information of transfemoral amputee. The characteristic value is extractedby wavelet package. K-Nearest Neighbor (KNN) algorithm is used in motion pattern of typicalcyclical movement. Pressure sensor is placed in heel and toe, which used to detect the phases ofeach gait. The sensor can recognized motion pattern and phases quickly and precisely.4. The Active Knee Prosthesis not only provides power for amputee, but also coordinatesthe movements of sound-side. The five typical motions are repeatability and periodicity. Finite State Machine (FSM) is used in the control methods of Active Knee Prosthesis. The five typicalmotions are detailed planning, which contain input events and states. The input events are comefrom sensor information. The state is come from control mode database.