Modeling And Control Of The Mechanical Prosthetic Leg

Historically,amputees have always been a large proportion of society due to the wars,work accidents and diseases.With a rising number of those amputees,various supporting devices become an essential part of their life to get rid of those disturbances.For the purpose of improving amputees' life quality,the prosthetic leg is selected as the object of study.Moreover,the design and research of the mechanical prosthetic leg is purposed.Motions of the human leg are firstly analyzed in order to define the normal human gait pattern.The Lagrangian method is used to establish a dynamic model of the prosthetic leg.The dynamic model is represented as a mathematical model which can be applied in designing and analyzing the system of the mechanical prosthetic leg.According to the motions of the human leg,an experimental model of the prosthetic leg is designed,machined and assembled.The experimental model consists of hip assembly,thigh,knee assembly and shin.The control of the hip joint is a closed loop system which is driven by a DC motor,and the rotary encoder is taken as the sensor.The system of the knee joint is only working in the braking condition.It is controlled by a hydraulic brake which is driven by a servo motor.Simulink software is used to establish the simulation of systems of both the hip and knee joint which is based on classical PID control regarding the motions of the mechanical prosthetic leg.Then,a simulation design of PD+Fuzzy logic control of the knee system is established.The simulation results prove that the system has good tracking performance.The last part of the study is design of a control system for the experimental model.The computer and Simulink are selected as the interface and control software,respectively.Hip system hardware consists of a DC motor,Arduino Mega2560 board,L298 N motor driver and an encoder.Knee system hardware consists of a servo motor,Arduino Mega2560 board,a hydraulic brake and an encoder.PID control and PID+Fuzzy control algorithms of the hip system are trialed respectively.The test results show that PID+Fuzzy control algorithm provides superior tracking performance.