Abstract: For dynamics modelling and solution of machine drive system, servo drive system and NC interpolation module, a new NURBS interpolation algorithm is proposed. In every interpolator period the reference velocity is set by the trajectory planner, then according to the geometry characteristics the maximum velocity is limited to meet the chord error demand. The dynamic equations are solved to calculate the needed torque if the reference velocity is transported to servo unit. If the needed torque is greater than maximum one that servo system can provide, a proper deceleration is applied for decreasing the reference velocity. At last first-order Taylor’s expansion approximation is employed to calculate the new interpolation point. This algorithm can adjust the feedrate where the curvature is great, so as to meet the requirement on chord error, and make the interpolation velocity instruction area smooth. This algorithm can ensure the servo units to achieve the interpolation point in time, thus avoiding machining error.

Key words: Adaptive feedrate, Chord error, Curvature, Dynamics of machine tools, NURBS interpolator