Research On Finite-time Tracking Control Of The Omnidirectional Rehabilitative Training Walker With Consideration Of Dead-zone Effect

With the increase of the aged,brain or spine diseases lead to a significant increase in patients with walking dysfunction,resulting in a serious shortage of medical resources,which leads to the rapid development of rehabilitation robots.Rehabilitation robot usually needs to track the training trajectory specified by the doctor to help the patient walk training,and various tracking control methods have been proposed at present.However,these control methods do not consider the influence of the characteristics of dead-zone on the system performance,and most of them solve the problem of asymptotic tracking.The asymptotically stable system state will gradually tend to the equilibrium point with time,which may cause a large tracking error in the transient phase of the robot,so as to collide with the obstacle and affect the safety of the patient.In view of the above analysis,this paper studies the control of finite time with dead-zone compensation for an omnidirectional rehabilitation walking training robot.The main contents are as follows:For the problem of the characteristics of dead-zone in the omnidirectional rehabilitation training walking system,an adaptive estimation method for dead-zone width is proposed to obtain and compensate the dead-zone information;based on the Lyapunov finite time stability theory,a finite time controller is designed to ensure that the system can reach stability in a finite time;simulation and experimental studies show that the proposed finite time control method can quickly converge the system error and suppress the influence of the dead-zone characteristics on the system performance.Considering that the characteristics of the dead-zone will affect the tracking accuracy of the robot system,the radial basis function neural network method is used to approximate the dead-zone;combined with the backstepping recursive method,a finite time tracking controller is proposed to suppress the influence of the dead-zone on the tracking performance of the system and verify the finite time stability of the system;simulation studies show that the designed finite time controller can achieve stable tracking of the system in a finite time under the effect of the unknown dead-zone.On the basis of compensating the influence of the dead-zone on the system performance,for the rehabilitation robot system with various interferences and uncertainties,a nonlinear interference observer is designed to estimate the uncertainties and various interferences of the system online and a finite time controller is designed by using the interference estimate value,which suppresses the adverse influences of interference on the system and proves that the system is stable in finite time;simulation studies verify the effectiveness of the interference observer and the finite time controller.