Speed and position control apparatus for positioning a movable object

A position control apparatus for positioning a movable object comprising:

• signal generating means for generating false sine-wave two-phase signals having a phase difference equal or close to 90 degrees with each other so as to correspond to a movement of a movable member to be position-controlled;
• adding means to obtaining a sum signal of respective phase signals generated in said signal generating means;
• subtracting means for obtaining a subtraction signal of respective phase signals generated in said signal generating means;
• comparing means for making bi-leveled signals by comparing said sum signal with its mean value and by comparing said subtraction signal with its mean value;
• exclusive OR means for obtaining an exclusive OR output signal from said bi-leveled signals of the sum signal and the subtraction signal;
• selecting means for selecting either of said respective phase signals in response to said exclusive OR output signal;
• switching means for selectively outputting an output signal obtained from said selecting means or its inverted output signal having an opposite-polarity on the basis of the bi-leveled signal of said subtraction signal;
• AC component inputting means for inputting an AC component of said output signal fed from the switching means to a sample and hold circuit;
• and
• feedback means for returning an output of the sample and hold circuit, which holds a sample value inputted during a predetermined period of time in response to a building-up of said exclusive OR output signal, to its input terminal so as to realize a DC restoration.

A speed and position control apparatus for positioning a movable object comprising:

• signal generating means for generating false sine-wave two-phase signals having a phase difference equal or close to 90 degrees with each other so as to correspond to a movement of a movable member to be speed- or position-controlled;
• adding means for obtaining a sum signal of respective phase signals generated in said signal generating means;
• subtracting means for obtaining a subtraction signal of respective phase signals generated in said signal generating means;
• comparing means for making bi-leveled signals by comparing said sum signal with its mean value and by comparing said subtraction signal with its mean value;
• exclusive OR means for obtaining an exclusive OR output signal from said bi-leveled signals of the sum signal and the subtraction signal;
• differential means for generating differential signals of respective phase signals generated in said signal generating means;
• first selecting means for selecting either of said differential signals of respective phase signals in response to said exclusive OR output signal;
• first switching means for selectively outputting an output signal obtained from said first selecting means or its inverted output signal having an opposite-polarity on the basis of the bi-leveled signal of said subtraction signal;
• second selecting means for selecting either of said respective phase signals in response to said exclusive OR output signal;
• second switching means for selectively outputting an output signal obtained from said second selecting means or its inverted output signal having an opposite-polarity on the basis of the bi-leveled signal of said subtraction signal;
• AC component inputting means for inputting an AC component of said output signal fed from the second switching means to a sample and hold circuit;
• and
• feedback means for returning an output of the sample and hold circuit, which holds a sample value inputted during a predetermined period of time in response to a building-up of said exclusive OR output signal, to its input terminal so as to realize a DC restoration.

An apparatus selectively executing a speed control operation or a position control operation for a recording/reproducing head on the basis of a distance between a target position and an actual head position in the case where the recording/reproducing head is linearly shifted with respect to a disk-shaped recording medium so as to position the recording/reproducing head to the target position on the recording medium, said apparatus comprising:

• encoder for generating false sine-wave two-phase signals having a phase difference equal to or close to 90 degrees with each other so as to correspond to a movement of a recording/reproducing head;
• speed detecting means for detecting an actual shifting speed of the recording/reproducing head during the speed control operation;
• speed control signal generating means for generating a speed control signal on the basis of a difference between the actual shifting speed obtained from said speed detecting means and a head speed pattern interrelated with a distance between an actual position of the head and the target position;
• switching means for detecting a shifting distance of the recording/reproducing head based on a signal fed from either of said two phase-signals and switching, in response to this detected shifting distance, an operational condition from the speed control operation to the position control operation shortly before the recording/reproducing head approaches the target position;
• and
• enlarging means for enlarging, within a predetermined period of time immediately after the operational condition has been changed from the speed control operation to the position control operation, a detecting range of an error voltage for the position control operation to be greater than a minimum pitch detected by the encoder.