| Up to now,many achievements have been made on trajectory tracking of wheeled mobile robots,however,only a few of them consider the saturation constraint of the actuator motor.For the actual robot system,there is saturation constraint because the actuator is affected by its own mechanical characteristics.If the control input exceeds the maximum limit of the actuator motor,the stability of the system may be reduced or even lead to system instability.Therefore,it is of great practical significance to design a trajectory tracking controller with limited input for wheeled mobile robots.In this thesis,the problem that the actuator motor of the robot is subject to saturation constraint is fully considered,and the trajectory tracking control of the wheeled mobile robot is studied.The main work contents are as follows:(1)The trajectory tracking control problem of wheeled mobile robot with limited input velocity is studied.Firstly,in order to overcome the problem that the wheeled mobile robot posture and the error model is not bijective,a fourth-order kinematic model is adopted.Then,considering the saturation constraint of the actuator motor,a velocity limited trajectory tracking law is designed based on the fourth-order kinematic model to ensure that the linear velocity and angular velocity of the robot meet the expected constraints,and the stability analysis is given.Finally,the effectiveness of the proposed method is verified by simulation and experiment.(2)The trajectory tracking control problem of wheeled mobile robot with limited velocity and acceleration is studied.In order to avoid the abnormal operation of the motor caused by the rapid change of velocity,the acceleration limitation of the robot is also taken as one of the control objectives.Firstly,the bounded and uniformly continuous feedback signals are obtained by introducing two first-order filters.Then,taking linear velocity and angular velocity as control inputs,a trajectory tracking control law is proposed based on the fourth-order kinematic model,which can restrict the velocity and acceleration of the robot,and the stability analysis is given.Finally,the proposed control method is verified by simulation and experiment.(3)Based on the kinematic model and dynamic model,the trajectory tracking control of wheeled mobile robot with limited velocity and acceleration is studied.Firstly,a simplified dynamic model is established.Then,the motion control law proposed in(1)is used as the virtual velocity control law,and the torque control law is proposed as the control input to ensure the robot velocity and acceleration constraints.Finally,the effectiveness of the proposed method is verified by simulation and experiment. |
