PURPOSE: To eliminate a time delay by providing a means to directly feed back a voice coil motor VCM to an input of a power amplifier and providing a saturation decision means to decide whether or not the power amplifier is saturated. CONSTITUTION: VCM current i(t) is fed back to an input terminal of a power amplifier IPA 64, and the VCM current is totaled with an analog control signal U(t) in the amplifier 64. The amplifier 64 is changed into a low-pass filter with a linear characteristic, and accurately measures the VCM current when operating within a linear range. After updating a predicted value by using a linear model of the VCM current or a saturation model, a microprocessor 50 is in the state immediately to receive values of the following linear wave PESP and a square wave PESQ. By using these values with the predicted values including a predicted value of the VCM current and being updated in a state variable, an estimated value of the state variable, the following control signal, is calculated. Thus, by maintaining an accurate VCM current, a data recording disk file with no delay time is obtainable.
展开▼
