| Robotic manipulators have been widely used in industrial production tasks such as welding,handling,palletizing,and spraying.The smooth execution of these tasks requires the robotic manipulators to be equipped with high-performance controllers to achieve high-precision,fast-paced trajectory tracking control.In addition,with the continuous advancement of industrial automation and the rapid development of modern technology,the tasks performed by the robotic manipulator are becoming more and more complex,such as polishing,deburring and assembly,which often require the robotic manipulator to interact with the environment to generate a certain amount of energy interact.Obviously,the robust position tracking controller cannot help the robot to successfully complete these tasks,and thus the force control that interacts with the environment is very important.In the process of force controller design,force feedback is essential information.Considering the production cost of force sensors and the reasons why their installation and deployment will increase the mechanical design complexity of the manipulator system,the research on force estimation emerges as the times require and receives high attention.This paper focuses on the high-performance position control technology and force estimation technology of the robotic manipulator system.The robotic manipulator system are introduced in detail from these aspects: the motion control unit,the servo drive unit and the basic mechanical unit.The kinematics and dynamics models of the manipulator system are deduced by using D-H parameter modeling and Newton-Euler principle respectively,and the parameters of the manipulator dynamics model are identified by the least square method,thereby establishing the manipulator system dynamics model.The factors affecting the accuracy of position tracking and force estimation are analyzed.In order to improve the performance,the design ideas of disturbance observer technology,sliding mode control theory,model predictive control theory and non-smooth control theory are combined,and corresponding solutions are designed.The research is carried out from the following four aspects:(1)In order to improve the motion beat and tracking accuracy of the manipulator system,a new controller composed of a discrete-time extended state observer and a discrete-time fast terminal sliding mode controller is proposed.First,the Euler-discrete method is used to discretize the manipulator system.Subsequently,the system disturbances are estimated using a discretized extended state observer.Compared with traditional delay estimation methods,the discretized expanded state observer can not only estimate system disturbances,but also avoid the effects of measurement noise and spikes.In addition,the Lyapunov method proves that the position tracking error accuracy of the manipulator system is the third-order infinitesimal of the sampling time.Finally,experiments show that the proposed control algorithm can achieve high-speed and high-precision position tracking control.(2)Considering dynamic constraints on robot velocity and acceleration is of the essence.However,the system uncertainties arising from unmodeled dynamics,coupling,friction and unpredictable external disturbances brings serious challenges to the realization of constraints and accurate trajectory tracking.To deal with this problem,an optimal control solution for the trajectory tracking problem is proposed.First,the manipulator system is discretized by the Euler-discrete method.Then,a discrete-time super-twisting observer is designed to observe the system disturbance in real time,and combined with the feedback linearization technique to directly compensate the known nonlinear dynamic model,a revised prediction model of the manipulator system is obtained.The optimal control input sequence of the manipulator system is obtained by using the design ideas of multi-step prediction,receding optimization and Lagrange multiplier method.Finally,the experimental results verify the effectiveness of the proposed method.(3)A non-smooth tracking control scheme of a manipulator system based on output feedback is proposed for the situation that the joint velocity signal of the manipulator system cannot be obtained.First,through the system control input and known position signal,a non-smooth observer is constructed to estimate the joint velocity signal,unknown disturbance and uncertain nonlinear functions.Subsequently,a non-recursive tracking control method based on joint position outputs is designed using the observed values.The stability of the closed-loop system of the manipulator is proved by a Lyapunov method and the homogeneous system theory.Finally,the simulation and experimental results demonstrate the effectiveness of the proposed algorithm.(4)A high-order non-smooth contact force observer is proposed for the case of no sensor in the interaction between manipulators and environments.According to the manipulator model,a non-smooth contact force observer with higher precision,faster response and more generalization ability is designed and is used in applications such as drag teaching,collision detection and impedance control.Finally,comparative experimental evaluations demonstrate the effectiveness of the proposed contact force observer. |
