Final servo control in NC systems

An improved final servo control for numerical control systems of the type which perform linear and/or circular interpolation by iterative updating of commanded position signals. The improvements are embodied in means to sense when the servo loop has had an offset error introduced by drift or aging of the final amplifier or similar components, together with means for progressively and automatically removing such error; and by means to avoid attempts at extreme acceleration or deceleration beyond the ability of the servo power element (motor) to accomplish, -by creating from an iteratively updated primary position command signal, whose rate of change may suddenly alter by a wide margin, a secondary position command signal which varies ultimately by the same amount but at a lesser rate of change.