Trajectory Tracking Control Of An Omnidirectional Mobile Manipulator Based On ADRC

A mobile manipulator has both wide workspace and flexible operation ability,and it is widely used in scientific investigation,medical service,industrial production and many other fields.The mobile manipulator is a kind of multi-input multi-output system with nonlinearity,strong coupling and time-varying.It is difficult to establish its precise mathematic model.In addition,there are a large number of parameter uncertainties,unmodeled dynamics and external disturbances.Therefore,designing a strong robust trajectory tracking controller with high tracking accuracy has become one of the topics in the field of mobile manipulator.In this paper,combined with the sliding mode control and the improved extended state observer,an active disturbance rejection control system is designed for trajectory tracking control of an omnidirectional mobile manipulator,with the presence of parameter uncertainties and external disturbances.The main research contents are:1)according to the structural characteristics of the omnidirectional mobile manipulator,the kinematics model and dynamics model are derived,the dynamic model has more practical value with the consideration of the dynamic characteristics of the motor.2)a linear active disturbance rejection control is designed for trajectory tracking control of the omnidirectional mobile manipulator in joint space,with the presence of parameter uncertainties and external disturbances.Stability analysis shows that bounded-input bounded-output stability is guaranteed for the control system.Simulation results demonstrate the effectiveness of the proposed control algorithm.3)aiming at the shortcomings of the linear active disturbance rejection control method in trajectory tracking control of the omnidirectional mobile manipulator in joint space,the traditional extended state observer is improved.The ability to estimate disturbance is enhanced.A sliding mode controller is designed to further improve the robustness and dynamic characteristics of the control system.The asymptotic stability of the control system is proved based on Lyapunov.The effectiveness and strong robustness of the control algorithm are verified by simulation.4)in view of the shortcomings of the control of the omnidirectional mobile manipulator in joint space,the trajectory tracking control of the end effector is studied based on operating space.At the same time,in order to ensure the robustness of the control system and avoid the chattering problem existing in the traditional sliding mode control,the controller adopts the Super Twisting algorithm.The Lyapunov method proves that the control system is asymptotically stable,and simulation results validate the effectiveness of the proposed controller.