Dynamics Modelling of Milling Robot with Variable Posture

Industrial robots are more flexible and cost-effective than machine tools for milling large and complex structural parts. It has a greater advantage in some original position machining scenarios. However, its low stiffness and posture-dependent dynamic characteristics make milling processes prone to chatter, which affects surface quality of workpieces and even causes damage to tools. Milling stability predicted by stability lobe diagrams is an effective way of preventing chatter. However, when a robot moves over a wide range, its modal characteristics and stability also change significantly. Hence, accurate dynamics models are needed to predict the posture-dependent dynamic properties of industrial robots, which are demanding and difficult to obtain experimentally. In this work, a robotic dynamics model with variable posture is developed based on the transfer matrix method for multibody systems. The model prediction and correction are carried out by identifying joint stiffness and damping parameters in different workspaces. Finally, the developed model is verified through experiments.