Study On Robot Trajectory Tracking Based On Linear Active Disturbance Rejection Control Technique

Robot system is a class of highly nonlinear, strong coupling, time-varying and MIMO(Multiple Input Multiple Output)system, and there are many uncertainties in the system such as un-modeled dynamics, external disturbances, friction, etc, resulting in the problem of trajectory tracking control becomes very complex. With the rapid development of modern industry, the requirements of performance and precision of robot are more and more higher, to accommodate this phenomenon, further research on trajectory tracking control of robot has a very important practical significance.LADRC (Linear Active Disturbance Rejection Controller) is the linearization of ADRC (Active Disturbance Rejection Controller), it not only retains the control effect of ADRC, but also simplifies the parameter setting. LADRC is not overly dependent on the accurate mathematical model of robot and can estimate and compensate the general disturbance that includes coupling term and various uncertain factors by LESO (Linear Extended State Observer), so the joint variables decouple with the joint input torques completely and the complex control of robot is simplified to the linear control, the result is that control object becomes simple and the performance of the system is improved.Firstly, this paper take four degrees of freedom SCARA industrial robot as an example to deeply analyze motion characteristic of industrial robot and find out the kinematics equation of SCARA robot. On this basis, further discuss the problem about how to establish the dynamic model of robot and establish the dynamic model of SCARA robot by Lagrangian method.Secondly, this paper ascertain the development and principle of ADRC, focus on the analysis of the relationship between ADRC and LADRC and the problem of LADRC parameter tuning, and present a complete second-order LADRC algorithm, later take a MIMO system as an example to discuss the decoupling principle of LADRC.Thirdly, on the basis of the established robot dynamic model, this paper analysis of the shortcomings of classic PD controller in the trajectory tracking control of robot with uncertainties, thus LADRC is proposed for trajectory tracking control of robot and the trajectory tracking controller based on LADRC is designed. Through the study of the dynamic simulation of the designed controller, the results indicate that LADRC has strong robustness against uncertainties in the robot system.At last, this paper designed a two degrees of freedom industrial robot to verify the trajectory tracking controller based on LADRC, experimental results prove LADRC is valid and feasible in the trajectory tracking control system of robot.