Research On Trajectory Tracking Control Of Uncertain Wheeled Mobile Robot

With the successive development of computer science,sensors,intelligent control theory,more and more attention has been paid to the research of robot.As a member of the robot's camp,mobile robot has been widely used for its simple structure and flexible operation.This dissertation focuses on dealing with the tracking control problem of nonholonomic wheeled mobile robots(WMRs)with uncertainties and external disturbances by combining backstepping method,adaptive technique,sliding mode variable structure technique and Lyapunov stability principle.Different controller are proposed according to WMRs kinematics,dynamics and actuator dynamics respectively..(1)The trajectory tracking control problem of the WMRs kinematics model is studied which satisfies constraints from velocity and acceleration.First two first-order filters are proposed to produce bounded and uniformly continuous feedback signals incorporated in the tracking controller.And then,a set of inequality conditions imposed on the filter parameters and a feedback parameter are derived to guarantee the satisfaction of the velocity and acceleration constraints.Finally,combined with extended Barbalat lemma,a Lyapunov function is selected to prove the the tracking errors converge to zero.(2)The problem of trajectory tracking of actuator dynamic model with uncertainties of the wheeled mobile robot is considered.Firstly,combined with adaptive technique and backstepping method,virtual speed and torque controller are designed.And then,a practical voltage controller is proposed.The uncertainties in the system are estimated by adaptive estimator.In addition,differential tracker is proposed to inhibit the problem of "explosion of complexity" in the backstepping design procedure.At last,the simulation is established to verify the effectiveness of the proposed algorithm.(3)A finite-time control approach for trajectory tracking of wheeled mobile robots in the presence of external disturbances and inertia uncertainties is developed.Different from previous methods,backstepping method isn't employed here.The problem of "explosion of complexity" caused by the repeated use of the virtual controller is avoided accordingly.Firstly,a finite-time angle velocity control is designed to ensure the convergence of WMRs orientation.The upper bound of uncertain parameters and external disturbance in the system are estimated by adaptive estimator,and the estimate values are introduced to controller to suppress the disturbance.Finally the finite-time linear velocity controller is designed to ensure that the WMRs position tracking error converges into a small region.