Grinding force estimation and control of grinding robot with variable impedance control strategy

The unstable contact force during robot grinding results in an inconsistent material removal rate, poor surface quality, and reduced machining accuracy. In this work, an independently controlled grinding end-effector was designed to improve the cutting stability and maintain a constant contact force during the robot grinding process. An online estimation method of external grinding force based on generalized momentum is proposed to reduce the influence of vibration force noise on the measurement data and reduce the complexity of the control system. A robot grinding dynamics model and a grinding contact force compensation model were developed. A variable impedance grinding control strategy was proposed, which does not consider the stiffness of the workpiece, in order to maintain a consistent normal grinding force and guarantee the stability of the material removal rate. Finally, an experimental study was conducted to evaluate the effectiveness of this robotic grinding system. The experimental results demonstrate that the force estimator can accurately estimate the grinding contact force. Furthermore, the proposed robot grinding system is effective for different workpiece contours while maintaining a consistent normal grinding force. Compared to the teaching method without force control, the average roughness is reduced by 38%.