Digital servo system using microcomputer for controlling phase and speed of rotary body

摘要

A microcomputer (20) servo control the rotational speed and the rotational phase of a cylinder motor (37) of a VTR in a digital manner. The microcomputer (20) generates a 10-bit digital phase error signal DPH having sufficiently low conversion gain and a 10-bit digital speed error signal DSP having sufficiently low conversion gain in response to an FG signal generated with rotation of a cylinder motor. The digital phase error signal DPH and the digital speed error signal DSP are added to each other in a digital manner in the addition ratio 1:8. In addition, this result of addition is amplified by four times in a digital manner by extracting eight lower order bits thereof and then, converted into an analogue signal and supplied to the cylinder motor as a servo control signal. Thus, since the error signals are added to each other in a digital manner and then, the added signal amplified as required, a digital servo having a large capture range can be achieved as whole.