An iterative feed rate scheduling method with confined high-order constraints in parametric interpolation

Feed rate scheduling of complex tool path is critical for improvement of processing efficiency by fully exploiting the dynamic performance of machine tool in CNC machining. To overcome the complexity and low efficiency of conventional feedrate scheduling algorithm in computation, an iterative feed rate optimization method is proposed. In this work, the constraints that can reach the third-order derivative of motion in trajectory and drive system are established according to the differential operation of tool path and the feed rate profile. Besides, the feed rate expressed in the form of B-spline curve is adjusted iteratively by raising the control points from a zero-speed velocity curve. Specifically, in each iteration process, the control points are raised one by one through binary search technique to approach the permissive maximum with the constraints bounded. The iteration process terminates when the maximum increment of control points is less than the predefined threshold and then a near time-optimal feed rate is achieved. The scheduled feed rate derived by the iterative optimization method possesses both superior time-optimality and enough motion smoothness to the constraints without leading to excessive computation load. At last, the validity of the proposed method is verified by the simulation cases and the experiments.

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