| Lower limb dysfunction caused by disability,aging,traffic accidents and other reasons seriously affects the physical and mental health of patients.In traditional rehabilitation therapy,rehabilitation practitioners assist patients in moving their lower limbs.The training tasks are arduous and the number of rehabilitation practitioners is insufficient.There is an urgent need for a rehabilitation device to replace the rehabilitation practitioner to guide patients in lower limb training and help patients complete repetitive and tedious rehabilitation training.Most of the lower extremity rehabilitation equipment on the market is an end traction device designed with a treadmill exercise as a blue board,which can only achieve a fixed circular motion with a single track.The normal human gait is closer to the shape of an ellipse.Long-term use of circular trajectory training with different walking parameters from normal human body will cause the joint motion range to exceed the comfortable range of the human body.For some patients with joint deformities or severe injuries,it may even aggravate the condition.Therefore,it is extremely urgent to design a lower limb rehabilitation device that can realize any trajectory.This project analyzes the application of the mechanical structure and control strategy of lower limb rehabilitation equipment by investigating high-end medical rehabilitation equipment at home and abroad.Firstly,referring to the structure and movement mechanism of human lower limbs,the movement and stress of human lower limbs are analyzed.According to the gait data and the posture of the lower extremities,the working space of the rehabilitation equipment is determined by the graphic method.In this working space,two training paths of the circular trajector y and the elliptical trajectory are planned for the patient’s rehabilitation process,and they are decoupled to the rectangular coordinate system,the x axis and y axis.Secondly,the structure of the equipment is designed,and the main equipment such as ball screw and motor is selected.Then propose training methods suitable for different recovery periods for patients with different degrees of injury.In the early stage of rehabilitation training,the passive control method based on trajectory following was adopted,and the control performance of PID and PI+ correction system was compared by simulation.Taking into account the load changes,the interference signal is introduced,and the sliding mode controller is designed,so that the system can still real ize the accurate tracking of the trajectory even in the case of interference.In the middle and late stages of rehabilitation training,an active training method based on impedance control is used to control the dynamic relationship between the force and p osition of the humanmachine system.On the basis of position control,the impedance control model is added,through the control variable method,the influence of changing the impedance parameters on the end force is studied,and the reasonable control par ameters are selected according to the demand,and reasonable control parameters are selected.Due to the inaccuracy of the mathematical model of the actual system,the environmental parameters are constantly changing,which makes the actual control effect of impedance control not very good.By analyzing the steady-state error of impedance control,an adaptive control algorithm based on Lyapunov’s steady-state equation is derived.On the basis of the impedance model,an adaptive controller is added,an adaptive control law is designed,and the applicability of the adaptive algorithm in an unknown environment is simulated and analyzed.It can estimate environmental parameters in the real time and complete the follow-up of humanmachine forces.Based on the fractal theory,a model was established to demonstrate the relationship between the porous graphite permeability and the fractal dimension.It can predict the permeability of porous graphite and show the effects of the pore size on the permeability. |
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