Research on Posture-Dependent Mode Coupling Chatter in Robotic Milling

In recent years, industrial robot has been widely used in milling because of its good flexibility. However, flexibility leads to the posture-dependent stability problem, while articulated structure makes mode coupling chatter more easily excited. All the above problems are research focus and difficulties in the robot milling field. In order to figure out the mechanism of posture-dependent mode coupling chatter in robotic milling, in this paper, a dynamic model considering the mode coupling chatter is first established, and the stability criterion of the mode coupling chatter is proposed by introducing the vibration form solution. Then the posture-dependence components in the stability criterion are derived in detail, the deformation ratio coefficient of the robot which refers to the ratio of vibration amplitude in different directions under the current cutting parameters is proposed, and the posture-dependence of the chatter is clarified. Finally, through simulation experiment, the change of robot stability with posture is analyzed, and the cutting experiment is used to verify the simulation results. The results show that the mode coupling chatter model of robot milling based on posture dependence is more accurate and can be used as the theoretical basis for the optimization of robot milling parameters such as posture optimization and tool path planning.