Dynamic approach of the feedrate interpolation for trajectory planning process in multi-axis machining

Abstract

Feedrate interpolation, which consists in generating the set points sent to the axis controllers from the initial path, constitutes a major line of the trajectory planning process. In multi-axis high-speed machining the feedrate is usually evaluated by a kinematic method as the maximum feedrate respecting the joint velocity, acceleration an jerk limits. However, this approach requires a difficult experimental tuning of the kinematic limits based on the observation of the axis behaviour that leads to a loss of productivity. The multiplication of the kinds of multi-axis machines in manufacturing leads to the need to take the dynamic behaviour into account, particularly for highly dynamic systems such as serial robots. A novel and efficient dynamic approach of the feedrate interpolation process is proposed in this paper. The system performance characteristics are checked through torque and torque rate limits at the actuator level. The integration of the dynamic model of the system enables to include different chosen effects such as inertia, centrifugal, Coriolis effects, gravity and friction forces. The dynamic model can be also easily adapted to different systems and processes such as serial manufacturing robots or multi-axis machining centers. Then, these new dynamic constraints lead to limit values based on the dynamic behaviour of the whole axis mechanical chain from the actuator to the end-effector and allow to be close from the system components technology. The efficiency of the proposed approach is demonstrated by several simulations on different systems and test paths and is compared to the usual kinematic method results.