  In high speed CNC (Compute Numerical Control) machining, the feed rate
scheduling has played an important role to ensure machining quality and
machining efficiency. In this paper, a novel feed rate scheduling method is
proposed for generating smooth feed rate profile conveniently with the
consideration of both geometric error and kinematic error. First, a
relationship between feed rate value and chord error is applied to determine
the feed rate curve. Then, breaking points, which can split whole curve into
several blocks, can be found out using proposed two step screening method. For
every block, a feed rate profile based on the Sigmoid function is generated.
With the consideration of kinematic limitation and machining efficiency, a
time-optimal feed rate adjustment algorithm is proposed to further adjust feed
rate value at breaking points. After planning feed rate profile for each block,
all blocks feed rate profile will be connected smoothly. The resulting feed
rate profile is more concise compared with the polynomial profile and more
efficient compared with the trigonometric profile. Finally, simulations with
two free-form NURBS curves are conducted and comparison with the sine-curve
method are carried out to verify the feasibility and applicability of the
proposed method.
