| The number of amputees caused by diseases or accidents is increasing year by year.In order to restore the original form and function of the disabled limbs,reduce the dysfunction,restore the ability to exercise and live,live independently,study and work,and make them return to society,it is necessary to assist patients to adapt the knee prosthesis.So as to make the knee prosthesis move naturally,the motion Angle and speed of the knee prosthesis should be similar to that of the healthy human body,whose essence is the damping control of the knee prosthesis.In this paper,the damping control of knee prosthesis is studied,and a small hydraulic cylinder with adjustable damping is designed,which can realize the switching between non-damping mode,downward locking mode and bidirectional adjustable damping mode.Based on the magnetorheological(MR)damping control technology,a smart knee prosthesis is designed,which is compact in structure and light in weight.Combined with the supporting control algorithm,it can realize highly anthropomorphic gait movement and help amputees rebuild walking ability.Based on hydraulic cylinder and magnetorheological technology,this paper developed small hydraulic cylinder and intelligent control knee prosthesis respectively,and studied the following contents:(1)Human knee movement data acquisition.Vicon motion acquisition system and force plate are used to capture the moving gait of healthy human body,and the reaction data of plate and ground are combined.Opensim software is used to reverse solve the kinematic data and dynamic data of the moving gait process of healthy human knee joint.Based on the obtained data,a complete gait cycle is analyzed.(2)Manual adjustment damping small hydraulic cylinder design.According to the requirements of joint prosthesis,a small hydraulic cylinder with compact oil circuit and adjustable resistance was designed.After processing physical samples,a torque test platform of active and passive prosthesis including a knee-like prosthesis fixture was built to test its adjustable range.(3)Structural design of MR Intelligent knee prosthesis.Since the small hydraulic cylinder cannot automatically adjust its own damping to adapt to the wearer’s walking at asynchronous speed,and the joint torque has a great influence on the out-of-sync speed walking,the magnetorheological intelligent control type knee prosthesis is further designed to control the joint torque.The dimensional structure of the core parts of the prosthesis was determined by the kinematics analysis of the prosthesis and the theoretical calculation of the magnetic field of the closed magnetic circuit of the prosthesis.The theoretical relationship between the current and the joint torque was obtained by electromagnetic simulation.The control algorithm of MR Intelligent knee prosthesis was developed.Combined with the Angle sensor,uniaxial pressure sensor and inertial measurement Unit(IMU)on the prosthesis,the Angle,forward pressure and attitude data of the prosthesis in motion are collected.The finite-state machine algorithm was developed to recognize the stage of gait,and the current value was adjusted by PWM to control the intensity of the internal magnetic field of the prosthetic,and the torque required by the current gait was output.(4)Test and analysis of MR Intelligent knee prosthesis.The active and passive prosthetic torque experiment platform was used to conduct bench test on the intelligent knee prosthesis,and the actual relationship between the current and the torque of the prosthesis was obtained.Based on the data of human thigh swing,ADAMS was used to simulate the dynamics of the intelligent prosthesis,and the torque required by the knee joint of the intelligent prosthesis to maintain the normal gait was obtained.Based on Matlab Simulink module,the main controller of intelligent prosthesis is developed.According to the walking speed and gait cycle stage of human body,the joint torque can be controlled autonomously to achieve normal walking gait. |
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