Real-time master-based feedrate scheduling with kinematic constraints for five-axis machining

Feedrate scheduling with kinematic constraints is a challenging problem for five-axis machining. Linear and rotary drives of five-axis machine tools have different capabilities and limits. The main issue is that the feedrate profile generated by the existing five-axis feedrate scheduling method might violate kinematic constraints since the tangential and axial jerk could not be directly correlated due to nonlinear kinematics transformation. In this paper, a novel master-based feedrate scheduling (MBFS) approach with real-time and drive constraints is developed to generate smooth trajectories along five-axis linear toolpaths. Based on inverse kinematic equations, tooltip feed parameters are evaluated by a five-axis feed regulation formula (FFRF) such that axial velocities, accelerations, and jerks could be constrained within given limits simultaneously. The tooltip or rotary axis having the largest motion duration is selected to be the master, and the others are regarded as the slaves which move with the master synchronously. Rather than planning the feedrate profile using the curve parameter algorithm, linear and angular trajectories are planned by matching the same motion duration to realize time synchronization of five-axis motion. The local corner smoothing method is adopted to blend the velocities of the motion axes and generate cornering trajectories while satisfying corner position tolerance and drive constraints. Finally, experiments are conducted on a five-axis engraving machine to verify that the proposed method can satisfy the kinematic constraints, and improve tracking and contour accuracy.