外文原文HighspeedCNCsystemdesign.docVIP

High speed CNC system design Abstract A servo control system capable of delivering rapid and accurate feed motion is a necessity for high speed machine tools. The control law must be designed to provide a high tracking bandwidth as well as adequate disturbance rejection and parameter variation robustness, in order minimize the following errors in each axis. This also contributes to the minimization of the contour errors in the machined part. This paper provides a systematic approach for designing such a control law. Position, velocity, and disturbance estimates are obtained using a Kalman filter. The feedback loop is closed using a pole placement controller with disturbance cancellation, in order to counteract the detrimental effects of friction, cutting forces, and drive parameter variations. The overall tracking bandwidth is widened by compensating for the closed loop dynamics in a feedforward manner. Also, the tracking errors due to friction transients at the corners and arc quadrants are reduced by precompensating for the expected friction forces. The contribution of each component in the control scheme to the contouring accuracy has been experimentally verified, and the overall contouring performance has been demonstrated in high speed machining tests. The experimental results were obtained using the smooth trajectory generation algorithm and identified axis and friction models which have been presented in Parts I and II respectively, of this paper. 1. Introduction High speed machining techniques require faster feed motion between the tool and workpiece,in proportion to the increased spindle speed. However, due to the limited bandwidth achievableby using only P, PD, or PID types of servo controllers, which are the most common ones used in industrial CNCs, there will be tracking errors in each axis as the closed loop control systemis not able to follow the rapidly varying position commands [1]. On the other hand, the friction in the guideways, as well as cuttin