Research On Active Control Of Active-passive Knee Prosthesis

The number of amputees due to various accidents and diseases is increasing in China,and for these patients,wearing a prosthesis is the main means to recover their walking.Due to the low cost of traditional mechanical prosthesis,it is more widely used,but this kind of prosthesis has the disadvantages of unnatural gait,high walking consumption,and can only run at a single speed.With the development of modern science and technology,multidisciplinary integration of intelligent prosthesis has become a research hotspot.China’s prosthetic level than developed countries have a big gap,foreign high-performance prosthesis is expensive,domestic amputation patients face a large economic burden,advanced prosthetic technology is in urgent need of a breakthrough.The passive prosthesis can adjust the damping at the knee joint to automatically adapt to changes in walking patterns,while the powered prosthesis has an active torque output function to better compensate for the biomechanical characteristics of the amputated limb.In this paper,we propose an active-passive knee joint prosthesis that combines hydraulic cylinder drive and simple structure,focusing on the simulation modeling and position control algorithm of the active hydraulic system of the active-passive prosthesis for the features of the active-passive prosthesis and the functions to be performed by the knee joint of the prosthesis,as follows:Combining the motion characteristics of knee joints of healthy human lower limbs,the changes of knee joint angles,moments and powers under typical motion patterns are analyzed,and the laws of knee joint energy generation and dissipation are summarized.For the proposed active drive system of active-passive prosthesis,the gait change mechanism and control strategy of the knee joint of the prosthesis are studied under the known road conditions and gait speed,and a control scheme combining gait switching and position control by a finite state machine is proposed.A closed-loop control system with fuzzy PID and an open-loop control system based on database are designed for the characteristics of the position control system and the hydraulic active drive system.A joint simulation model of the active drive of the prosthesis was established using Simulink and AMESim,and it was verified that the fuzzy PID control algorithm has better response characteristics in the position control of the prosthesis compared with the conventional PID in the simulation case.Using the characteristics of iterative learning control,a database of open-loop is constructed using iterative learning control,and it is verified based on simulation that iterative learning control can achieve better convergence in the prosthetic control system.Finally,an experimental rig is built to design the position control system for active drive of the prosthesis,and the experimental results verify the correctness of the simulation model and the closed-loop position control algorithm.In this paper,the proposed active-passive knee prosthesis is studied by simulation modeling and active control,which expands the research ideas of knee prosthesis control.