Research On Variable Structure Control Method Based On Omnidirectional Rehabilitative Training Walker

With the growth of aging population,there are more and more patients with motor dysfunction caused by diseases or external injuries.The science of medical research on rehabilitation exercise training can promote the recovery of the patients,so the rehabilitation training robots have been developed.The rehabilitation robot is a nonlinear system with high uncertainty and susceptible to external disturbances.When tracking motion is carried out along the determined trajectory,it is susceptible to load mass,center of gravity shift,unmodeled dynamics,surrounding environment,mechanical deformation,feedback information measurement error and other factors,so it is difficult to ensure the accuracy of system tracking.In the view of these problems,scholars have designed a lot of control methods,and made a lot of achievements.However,almost all these control methods are with the purpose of tracking,but they ignore the speed of rehabilitation robot and convergence time.This paper takes the dynamic model of the rehabilitation robots as the research objects,and the dynamic model of the gravity center offset is studied.The thesis adopts the variable structure control algorithm to design the corresponding controller,on the premise of ensuring that a certain tracking precision,realizing the limited speed and determining the convergence time,and the specific research contents are as follows:When the system tracking error is bigger,rehabilitation robot will produce larger movement speed to eliminate the tracking error.The influence of the speed on the users is considered,and the controller with the function of limited speed is designed.The detailed design ideas are as follows: the safety speed is definite at first,and application of inversion method is designed for speed and trajectory compensation algorithm.Then the author uses the variable structure control method to design controller which can restrict the speed directly.Next the author demonstrates the stability of the system.At last,the author compares the displacement tracking.So the effectiveness of the control strategy is verified by simulation experiments,and the function of limiting the rate is achieved.Secondly,for restraining the chattering of system and ensuring the status of the system can converge to the equilibrium point in a finite time,on the premise of ensuring the dynamic performance of variable structure,the author designs a new control method to ensure the accuracy of trajectory tracking.This thesis presents an improved adaptive effect of double power reaching rate to reduce the chattering of the system.Besides,the sliding surface is redesigned to ensure that the system state can converge in finite time.The simulation system has a good effect,which can accelerate the convergence speed of system error,and the desired trajectory tracking effect is obvious.