Research On Electro-hydraulic Drive And Control System Of Ankle Foot Prosthesis

For lower limb amputees,wearing passive prosthesis with no net positive work output is difficult to restore sound limb function.Studies have shown that the loss of net positive work cause lower limb amputees to expend more energy to achieve their desired walking speed.In order to design an ankle-foot prosthesis with an actuator to actively plantar flex the ankle that has appropriate size and mass,this paper use electro-hydrostatic actuation system to design the ankle-foot prosthesis which has the characteristics of high efficiency and high power density ratio to meet the daily needs of lower limb amputees.This article explored the mechanics characteristics and correct energy effect of the ankle foot prosthesis should be achieved in each stage of the gait which embarks from the sound human ankle features,and established the basic principle behind the driving mechanism of the ankle-foot prosthesis is to restore the impedance characteristics of the human body and can store and reuse energy.Studies have shown that setting elastic elements in the driving device of the ankle foot prosthesis can reduce the peak output power and energy consumption of the ankle foot prosthesis,and the parameters of elastic elements play a key role in both aspect of the ankle foot prosthesis.Based on the electro-hydrostatic actuation system as the driving core design of ankle foot prosthesis,the spring parameters were optimized and the results of different optimization objectives were studied through simulation,which make the dynamic ankle foot prosthesis lighter,more compact and more efficient.In this paper,based on the electro hydraulic actuator system as the driving core,the spring parameters of the ankle foot prosthesis are optimized.The results obtained from different optimization objectives were studied through simulation,which made the dynamic ankle foot prosthesis lighter,more compact and more efficient.For the control strategy of the ankle-foot prosthesis,a biomimetic feedforward controller based on the Hill muscle model with muscle reflexes was designed to achieve the nonlinear impedance characteristics of a sound human body.The results of simulation analysis showed that the driving device of the ankle prosthesis designed in this paper has a small energy consumption,furthermore,it can restore the characteristics of the ankle joint in the walking process of a healthy human with its control system.