Study On The Trajectory Tracking Robust Control Strategy Of Industrial Robot Manipulator

Robot manipulators are widely used in medical security,industrial production,and agricultural development.With the development of science and technology,the robot manipulator also plays an important role in ocean monitoring,aerospace,and other military fields.Therefore,the operation of the robot manipulator is not only limited to the repetitive positioning in practice but also achieving the desired tracking accuracy for a given trajectory has become a key research issue.However,due to external time-varying disturbances and the inherent friction,the control problem becomes more complex in the high-precision trajectory tracking control of the robot manipulator system.In this paper,high-precision trajectory tracking control schemes and high-performance force/position hybrid control strategies are studied for the robot manipulator system with external time-varying disturbances,uncertain dynamic parameters,and friction nonlinearity,as well as the robot manipulator system with input saturation,matched and mismatched disturbances.The main contributions of this paper are as follows:(1)The mathematical model of the multi-degree-of-freedom robot manipulator is established.Firstly,the mathematical model of the multi-degree-of-freedom robot manipulator is established by the Lagrange dynamics method.Then,considering the influence of the system friction,we established and analyzed the dynamical and static friction mathematical model,respectively.Finally,we proposed some theories as the theoretical support for the stability analysis.(2)A robust trajectory tracking control strategy with a disturbance observer is proposed for robot manipulators subjected to complex time-varying disturbances.Firstly,the backstepping method is used to design the trajectory tracking controller with the friction model,and then the first-order filter is introduced into the controller to solve the complex derivation problem of the virtual control input.An adaptive disturbance observer is designed to observe external disturbances online to address the problem that time-varying disturbances can influence tracking accuracy.The adaptive law can simplify the selection of parameters and get the appropriate gain for the observer.We designed a simplified neural network to approximate the modeling uncertainties caused by physical factors and measurement errors,which can reduce the number of hidden neurons.The system is proved to be semi-globally asymptotically stable by Lyapunov stability theory.The simulation results show that the robot manipulator can overcome the external disturbances well and track the trajectory quickly and accurately,which effectively improves the tracking accuracy of the system.(3)A novel robust hybrid force/position control(ARHFPC)strategy is proposed for robot manipulators subject to dynamic uncertainties and unknown matched and mismatched disturbances under input saturation.Firstly,the position controller is designed based on the backstepping approach.The first-order low-pass filter and the auxiliary dynamic system are synthesized into the controller to overcome the virtual control’s complex derivative operation and handle the input saturation effect,respectively.The radial basis function NN(RBFNN)is utilized for approximating the dynamic uncertainties and matched disturbances.Then,a novel mismatched disturbances observer is designed for the mismatched disturbances.Finally,a fuzzy proportional-integral(FPI)control is presented for increasing the accuracy of control over the interaction force between the end-effector and external environment.It is theoretically proved that all signals in the closed-loop control system of robot manipulators are locally uniformly ultimately bounded(UUB).Simulation results illustrate the effectiveness and robustness of the proposed control scheme.This paper has in-depth discussions the trajectory tracking control problem and hybrid position/force control problem of robot manipulator with considering the input saturation,joint friction,complex matched and mismatched diaturbances,and model uncertainties.Some novel approaches are proposed in the design of the control system,and the proposed approach will enhance the position tracking and force tracking accuracy of the robot manipulator.