Research on the S-shaped time-rounding series feedrate scheduling based on NURBS curve

Abstract

The inconsistency between continuous feedrate scheduling and discrete interpolation of Non-Uniform Rational B-Splines (NURBS) curves as toolpath interpolation affects the interpolation accuracy and motion smoothness of computer numerical control (CNC) machining. The S-shaped series feedrate scheduling method of the NURBS curve is presented to meet the consistency between feedrate scheduling and interpolation, and the needs of the motor to receive accurate discrete pulses to avoid chatter. The acceleration and deceleration margin factor models are respectively established in the acceleration and deceleration stages to compensate for the velocity loss in the discrete process, so that the feedrate scheduling can be accurately reached in each acceleration and deceleration stage. Based on this, 17 kinds of acceleration and deceleration situations are summarized according to the comparison of displacement, start and end velocity, and the number of interpolation cycles. The butterfly three-segment trajectories are selected for simulation in Matlab. The experimental platform is built based on the Codesys platform programing, and the series feedrate scheduling of the proposed method for a NURBS toolpath is carried out. Both simulations and experiments have verified the effectiveness of the algorithm.