| In various industrial scenarios such as mold production,automobile manufacturing,precision instruments,etc.,polishing is considered to be one of the indispensable processing technologies.Manual polishing is inefficient and easy to cause harm to human bodies.With the gradual improvement of automation,robots can be used in practical intelligent polishing.This paper aims at the precision calibration and force control technology of industrial robots,the research work on PD adaptive variable admittance force and position hybrid control method of grinding and polishing robot based on closed-loop calibration was carried out to solve the problem of high-precision force and position hybrid control of macro-mini robot,which can be used for free-form surface grinding and polishing operations,and provide solutions and technical support for intelligent grinding and polishing processing in industrial scenes.Firstly,aiming at the problem of low positioning accuracy of industrial robot,the kinematics model and spherical center distance error model of polishing robot are established by using MDH method.MDH method is used to build the kinematics model of the industrial robot body,and the forward and inverse solutions are verified by simulation;based on the kinematics model,the differential geometry error model is established.Furthermore,a low-cost closed-loop calibration method is used to establish the spherical center distance error model through spherical constraint equation and distance error calibration equation.Secondly,the methods of geometric error parameter identification and joint space error compensation of robot are studied,and a closed-loop calibration algorithm is developed.The QR decomposition method is used to remove the redundancy of the Jacobian matrix of the robot’s geometric error,optimize the number of measuring position and pose points,and the Levenberg-Marquardt identification algorithm is used to realize the identification of the robot’s geometric error parameters.The maximum deviation is reduced by 59.19%,and the average deviation is reduced by 70.84%;a closed loop calibration algorithm is developed by using joint space error compensation method to compensate the geometric error identification results of the robot,and is applied to the simulation of the grinding and polishing process trajectory.After error compensation,the trajectory tends to the expected trajectory.Then,the macro-mini robot grinding and polishing system is designed.Based on the constant force control idea,the PD adaptive variable admittance force control method is innovatively proposed,and the gravity compensation is carried out for the end effector,and the force control algorithm is developed.The PD adaptive variable admittance control method is studied.The PD regulator is used to adjust the force deviation,and the adaptive control law is used to update the damping term in the system admittance parameters.The force control algorithm is developed.The simulation analysis shows that the force overshoot during the contact of the grinding and polishing process is reduced,and the expected force can be stably tracked.The constant force control process of the grinding and polishing process is realized,which proves that the force control algorithm has stability and convergence.Finally,the macro-mini robot polishing system platform was built,and the closedloop calibration experiment and polishing force control experiment were carried out.The experimental verification of the PD adaptive variable admittance force and position hybrid control method of the polishing robot based on closed-loop calibration was realized.The closed-loop calibration method is adopted to compensate the error of the grinding and polishing robot.The absolute positioning accuracy after compensation is improved from 1.0080 mm to 0.2722 mm.In the force tracking experiment,the force control algorithm proposed controls the force tracking error of the plane,inclined plane and free surface within 0.15 N,0.24 N and 0.50 N respectively.In the grinding and polishing experiment,the grinding and polishing force tracking error is controlled within 0.80 N,and the overshoot is less than 4.5%,the robustness and force tracking performance of the proposed force control algorithm are verified. |
