Inverse Transfer Function Compensation for NC Control

Abstract

Since present numerical control machines (hereinafter referred to as "NC" machines) invariably use proportional control, there is a large time lag intrinsic to this control. Consequently, in the state of simultaneous plural-axes control, a locus error proportional to the movement speed inevitably results. Since this servo lag error is dependent on the proportional gain and acceleration/deceleration time constants after interpolation, this system parameter adjusts for each machine in advance and interpolates the NC data that are input while always performing optimum "inverse transfer function compensation" (gain compensation and phase compensation) on the said NC data. This has completely eliminated the first-order lag error which had resulted from the high-speed process. For example, when this system is combined with the machining center HA-5VA, it can move on a steep curve up to R5 mm with the tool center locus at a tangent speed of 6 m/min without any servo lag error. In addition, as a result of incorporating the above compensatory method, this system identifies the acceleration/deceleration of the response output with high precision. This allows the system to perform automatic acceleration/deceleration without any redundancy, using 1OO% of the servo actuater's power.