Dynamic modeling and stability prediction in robotic machining

Machining with anthropomorphic robotic manipulators is used to increase the flexibility and reduce the costs of production. Productivity in robotic machining processes is limited by low rigidity of robot structure and vibration instability in machining (chatter). Vibration instability analysis in robotic machining process is a challenging issue due to the variability of the dynamic behavior of the robot within its workspace. Hence, a dynamic model which correctly takes these variations into account is important to define the cutting parameters and the robot configurations to be adapted along a machining trajectory. In this paper, a multi-body dynamic model of a serial robot is elaborated using beam elements which can easily be integrated into the machining trajectory planning. The beam element geometry, elasticity, and damping parameters are adjusted on the basis of experimental identifications. A stability diagram based on regenerative chatter in milling operations as a function of the kinematic redundancy variable is established. It is shown that stability in robotic machining can be ensured through the optimization of the robot configurations, without changing the cutting parameters, in order to maintain productivity performance. The predicted stability diagram is validated by experimental robotic machining results.