Research On Sliding Mode Control Strategy For The Cushion Robot With Velocity Constraints

With the increase of the elderly population,diseases such as brain atrophy and chronic muscle injury lead to an increasing number of patients with walking dysfunction year by year.Due to the limited medical resources,cushion robot has been developed.In practical application,too fast movement speed of cushion robot will affect the user's safety,so it is necessary to restrict the robot's speed to ensure the use's safety.However,limiting the speed of the robot will increase the tracking error,and the center of gravity of the robot with load will shift,which makes it difficult for the robot to accurately track the specified trajectory.In order to improve the stability of the cushion robot system and accurately track the trajectory,this paper studies the trajectory tracking of the cushion robot based on the sliding mode variable structure control theory.The main contents are as follows:The dynamic model of the cushion robot considering the center of gravity shift is established;Based on this model,a speed-constrained sliding mode variable structure controller is designed,and a real-time compensation strategy is adopted to compensate the errors of trajectory and speed tracking,so as to reduce the impact of speed limitation on the system and realize accurate tracking of trajectory;A new sliding mode approach rate reduction system is designed to improve system stability;Numerical simulation results show that the designed controller can cope with the influence of center of gravity shift and velocity constraint at the same time.In order to make the robot system track the desired trajectory in finite time under the condition of speed constraint,a new nonlinear sliding mode surface is designed.The controller of cushion robot is designed by using the global Terminal sliding mode control method;The method of sliding die surface is proved by Lyapunov theory;A new rate is proposed,which effectively reduces the buffeting effect of the system;The simulation results show that the controller designed has good robustness to the internal and external disturbances of the system.The comparison shows that the chattering suppression effect is obvious,the system error convergence speed is accelerated,and the robot can quickly and accurately track the predetermined trajectory.