Study On Adaptive Motion Control Of Wheeled Mobile Robot With Time-varying Unknown Center Of Mass

Wheeled mobile robot(WMR)is a class of representative multiple input multiple output(MIMO)underactuated nonlinear systems containing nonholonomic constraints.Its motion control problem is very challenging.Due to the flexibility of the structure of wheeled mobile robot itself,which is widely applied in various fields(industry,agriculture,space exploration),these applications means that the wheeled mobile robot's work environment is complex,comprehensive and vulnerable to a variety of uncertainties and disturbances.Among them,the unknown mobility of the load makes the Center of Mass(CM)of the mobile robot uncertain,which makes the antisymmetric property of the system no longer set up,and brings challenges to the motion control of the mobile robot.How to improve the motion control performance of wheeled mobile robot under this complex uncertainty is of great significance.In the case of parameter uncertainty,sideslip and longitudinal sliding interference,this paper presents a more general modeling and motion control method for mobile robots under the uncertain CM.The motion modeling and control of a wheeled mobile robot in the case of actuator input saturation and actuator failure are discussed.Adaptive controllers for improving the performance of the robot are designed,such as the convergence of the error index and the limited trajectory output.The main research contents include:(1)The model description of a wheeled mobile robot with uncertain Center of Mass(CM)is studied.According to the deficiency of existing research and Lagrange's theory,a more universal mathematical model is established,which can reflect the change and uncertainty of the center of mass.(2)The trajectory tracking problem of wheeled mobile robot in the case of uncertain Center of Mass(CM)is studied.The adaptive controller is designed by the method of introducing the filter variable and applying the core function,this controller can make the trajectory tracking error eventually bounded.(3)The index convergence of trajectory tracking error of wheeled mobile robot is studied under the condition of uncertain Center of Mass(CM).The adaptive control algorithm is designed by introducing the intermediate variable and applying the core function.The algorithm can make the trajectory tracking error converge at an exponential speed.(4)The problem of trajectory output limited tracking of wheeled mobile robot under the condition of uncertain Center of Mass is discussed.Introducing an intermediate variable into a controller design based on an inverse tangent function,the design method of(Backstepping)is adopted,an adaptive control algorithm for a wheeled mobile robot to run in a predetermined range of trajectory is designed.Finally,the effectiveness of the designed methods are verified by the simulation results.