Research On Controlling Method Of Prosthetic Knee Based On Finite State Machine

As a powerful aid for the disabled to return to society,artificial limbs are developing towards the direction of intelligence.In addition,a large proportion of prosthesis users are patients with unilateral trans-femoral amputation,with many residual limbs retained but no knee joint.Due to the limitation of technical level,the current manufacturing level of lower limb prosthesis in China cannot meet the needs of the majority of disabled people.Therefore,it is of great significance to study more intelligent lower limb prosthesis to improve their living conditions.Based on the principle of finite state machine,this paper studies a control method for this type of prosthetic knee joint.In this paper,the trajectory of each joint of the healthy leg is taken as the ideal target of the control of lower limb prosthesis,and the platform of lower limb movement data acquisition is built.The PhaseSpace camera array is used to collect the lower limb movement data of healthy human.The human knee joint is abstracted into a simplified model to obtain the maximum and minimum torques that may appear in various road conditions.There are various control methods for prosthetic knee joint.This paper studies from the perspective of position control and establishes the control model of prosthetic knee joint based on the mathematical principle of FSM.After selecting two-phase hybrid stepping motor as the power source,the standard pulse signal and pulse frequency variation rule of a driving motor are calculated.The actual lower limb prosthesis will have operation deviation within a single gait interval.In this paper,the method of iterative learning control(ILC)is adopted to study the gait adjustment method of a single cycle,and the theoretical analysis curve is made.Two unsatisfactory cases of gait interval switching are considered: premature/untimely,and corresponding countermeasures are given.Taking the change law of plantar pressure as the data source of step velocity measurement,the step velocity is reversely calculated according to the proportion of interval to the total period.Based on the two problems of gait speed adaptation and internal adjustment of gait cycle,it is pointed out that the improvement of each index is not isolated,but related to some extent.In the flat forward mode,the calculated theoretical control information is used for motor simulation,and the pulse width modulation method is used to calculate the other control information.The reliability of the above research is confirmed.In the non-walking motion mode,the simulation model of motor controlled by torque is established.The control methods of prosthesis and knee joint are summarized.