Research On Artificial Active Ankle Based On Electrohydraulic Direct Drive Technology

Millions of people around the world are suffering from lower extremity injuries.Most existing passive ankle prostheses rely on elastic elements for energy storage and release.They can provide a simple support function for the human body and cannot fully realize the functions of the ankle joints of the human body.And will lead to the asymmetry of human gait.Considering the advantages of small size,light weight,simple structure,and high power density ratio,the electrohydraulic direct drive system is applied to active ankle prostheses.Based on the function and characteristics of normal human ankle joints,this article aims to design an ankle prosthesis that can help all patients with knee amputees to achieve all gait functions to ensure their normal life and workability.This article mainly conducted the following studies:The ankle joint movement mechanism,kinematics and biomechanical characteristics during normal human walking are analyzed to complete the gait phase division of the ankle joint and clear design indicators.According to the function to be completed,the choice of driving mode,the kinematics analysis of the dynamic artificial pedal and the analysis of the hydraulic part principle are completed,and the overall modeling of the dynamic artificial pedal system is completed.The modeling and analysis of electrohydraulic direct drive system for dynamic artificial pedals mainly includes the model of brushless DC servo motor speed control system and pump control cylinder system.Then the modeling of the electrohydraulic direct drive system is completed,and the stability of the system is analyzed.And the influence of parameters on the dynamic and static characteristics of the system,and the simulation analysis of the passive stage.According to the dynamical characteristics of active artificial pedals,the control strategy is studied.The upper-level control adopts a finite state controller to identify the heel landing during the control of the plantar flexion stage during normal walking.The factors that may cause misjudgment and the method to avoid misjudgment are analyzed.The motor start time and commutation time are determined,and an effective recognition of various postures of the human body is achieved.The lower level control is based on the characteristics of time delay and nonlinearity of the electrohydraulic direct drive system.Fuzzy PID is used for control and simulation analysis is performed.It has good control performance.An experimental platform for an active artificial pedal system was set up,an innovative scheme was formulated,bench experiments and walking experiments were performed on active artificial pedals,and the system performance was analyzed.The feasibility of applying electrohydraulic direct injection technology to dynamic artificial pedals and the control system were verified.Performance and correctness of finite state controllers.