Research On Grinding Force Control Strategy Of Industrial Robot Based On Impedance Control

In recent years,with the deepening of intelligent manufacturing and the rapid development of robot technology,industrial robot has been widely used in various fields of industry as an advanced and efficient automation equipment.However,due to the high stiffness and low positioning accuracy of industrial robot itself,and the tasks they face are becoming more and more complex,especially for contact operations such as grinding and polishing,it is difficult to meet the task requirements only by traditional position control.Therefore,how to make the industrial robot have good compliance,and realize accurate force tracking control in complex grinding and polishing environment has become an urgent problem to be solved in engineering.Based on impedance control,this paper proposes two force control strategies for unknown and complex grinding environment.(1)Based on impedance control,an adaptive force control strategy based on neural network damping ratio model is proposed.By designing an activation function that can describe the mechanism relationship between force error and damping ratio,the neural network damping ratio model is constructed.The damping coefficient of the impedance controller is dynamically adjusted to adapt to the dynamic changes of the end environment by the model.Thus,the force overshoot caused by contact and the force tracking error in steady state can be effectively reduced.The simulation results show that the adaptive impedance control method based on neural network damping ratio model can effectively realize force tracking control in complex unknown environment.(2)Based on impedance control,an adaptive force control method based on Fractional Order PID is proposed.By designing an adaptive control rate,the position and stiffness of the environment are estimated online to dynamically plan the adaptive reference trajectory to reduce the error of force tracking in unknown environment;In order to further improve the dynamic performance of the system,reduce the contact force overshoot and suppress the interference of the external environment.The Fractional Order PID is introduced to deal with the force tracking error to feed-forward compensation impedance model The simulation results show that the adaptive impedance control method based on fractional PID improves the force control performance of the system and effectively reduces the steady-state error of contact force.On the force control grinding experimental platform built by MOTOMAN-GP7 industrial robot and six-dimensional force sensor,the proposed adaptive impedance control strategy based on neural network damping ratio model and the adaptive impedance control strategy based on fractional PID are verified by grinding experiments respectively.The results show that the force control strategy proposed in this paper has better performance than the force control strategy based on traditional impedance control.