| 摘要 |
PURPOSE:To stably hold the frequency characteristic of a servo system by a method wherein, when the number of revolutions of a motor is changed by a number-of-revolutions changeover means, a reference-voltage control means changes a reference voltage and the operating point of a phase control signal is moved to a point where a quantization error is small. CONSTITUTION:The velocity control output AFC of a PLL control IC 10 is in inverse proportion to a target velocity omega0, a control-system gain is changed due to a change in the number of revolutions, and the control stability is worsened. Then, resistances 16, 17, 18 which decide the output AFC are connected in parallel, analog switches 31, 32 are turned on/off according to the number of revolutions, and only the gain of the output AFC is changed. When the number of revolutions is changed and a motor current is changed, the output voltage of the AFC is changed, and there is a possibility that the output voltage is passed through a point where the quantization error of a D/A converter is increased. However, when transistors 33, 34 are turned on/off by signals SIG 5, SIG 6 and a Vref is changed so as to match a motor current Imu, one output voltage of an APC can be moved to a desired point. |
