| 摘要 |
Positioning of a movable body can be achieved at a high resolution by making use of two position signals generated by a position detector, whose magnitudes are sinusoidal functions having different phases of the position of the movable body. On the basis of the two sinusoidal position signals, two bi-level digital position signals having different phase from each other are derived, and digital control for movement of the movable body is effected by making use of these two bi-level digital position signals until the movable body is brought into the proximity of a desired position. Thereafter, control is switched from the digital control to analog control for movement of the movable body, in which a position signal whose manitude is a sinusoidal function of the position of the movable body and has a zero-cross point at the desired position is used as a reference position signal. This reference position signal can be synthesized from the two position signals generated by the position detector by means of a simple signal synthesizer circuit according to the present invention. The signal synthesizer circuit comprises two multiplier type digital-analog converters, each of which is applied with a digital input signal and an analog input signal such as, for example, the above-mentioned sinusoidal position signal generated by the position detector and generates an analog output signal that is product including an algebraic sign of the digital input signal and the analog input signal, and an adder having the respective analog output signals of the two multiplier type digital-analog converters applied to its input. By appropriately selecting the digital values of the digital input signals, a desired reference position signal can be derived at the output of the adder.
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