Tracking Control Of Wheeled Mobile Robot With Uncertain Disturbance

With the rapid development of science and technology,the depth and range of human exploration activities have been continuously improved.Because robots can replace the work of humans including dangerous area assessment,explosive devices elimination and so on in hazardous and even life-threatening environments,wheeled mobile robots have been developed.The trajectory tracking process of the robot is susceptible to factors such as ground smoothness,load variation,external uncertain interference and feedback information integrity resulting in the reduced trajectory tracking performance of the mobile robot.In order to obtain accurate trajectory tracking effect,in this dissertation,the wheeled mobile robot is taken as the research object and the trajectory tracking control strategy is proposed to eliminate the adverse effects of the disturbance on the robot system.The main research contents are as follows.In this thesis,the four-wheeled mobile robot is treated as the research object and the special mechanical composition and structural layout of the mobile robot taking sliding turning as the steering mode are fully considered.The nonlinear kinematics model of the differential four-wheel-driven mobile robot with non-holonomic constraint is established.In the moving process of robots,the respective force of the four wheels is analyzed in detail.The nonlinear dynamics model of four-wheeled mobile robots is established by utilizing Lagrange method,which lays a foundation for the following research on trajectory tracking control of mobile robots.Based on the established nonlinear model of mobile robot,considering the external bounded disturbance factors affecting the system,an adaptive sliding mode backstepping controller is designed.The nonlinear disturbance observer is used to pre-estimate the observable disturbance in the system.The unobservable portions of the external disturbance signal can be compensated by the adaptive algorithm.Through the adjustment of controller parameters and adaptive law parameters,the trajectory tracking error can be approached to zero infinitely.The simulation results show that the adaptive back-step sliding mode control strategy can deal with the adverse effects of disturbance on the system,enabling the robot to track preset trajectories.A dynamic state model describing incomplete feedback information is established.Based on the model,a state observer is designed.A robust controller is designed for the uncertain disturbance factors existing in the output information.The stability analysis proves the exponentially asymptotic stability of the closed-loop system composed of the state observation error and trajectory tracking error is achieved.By adjusting the parameters of the controller,the trajectory tracking error can be approached to zero.The simulation results show that the robust control strategy with state observer can cope with the problem of incomplete feedback information,improve the anti-interference ability of the system and achieve the goal of the accurate robot trajectory tracking.