Servo with agc for positioning a magnetic head

Claim 2

In an access mechanism for a data storage device which includes a linear actuator operatively connected to an array of read/write heads, apparatus for accurately maintaining the head array in position at a given track location on a rotating recording disk, including: a transducer including A fixed grating and a movable grating cooperating with a power source, a pair of light sources, a pair of photoelectric sensors and generating two alternating signals of the same frequency but 180* phase relation for producing a continuous signal indicative of instantaneous position of the head array; means for combining the two transducer signals and servoing the head array onto the intersection of the signals; and means for continuously monitoring the signal to maintain a constant ratio of signal strength to increment of displacement of the head array from the track centerline.

Claim 3

Apparatus as defined in claim 1 wherein: the last-named means include means for summing the amplitudes of the two signals and comparing the sum with a reference to produce an error signal which is applied to the power source to control the power supplied to the light sources.

Claim 4

Apparatus as defined in claim 1 wherein: the last-named means include means for comparing the gains of the two signals and generating an error signal which is applied to the power source to control the distribution of power between the two light sources.

Claim 5

In a servomechanism for positioning a movable member, apparatus for accurately maintaining the member in a position at a given location along the path of movement of the member, including, a pair of transducers each including means for producing an alternating signal indicative of movement of the movable member, said alternating signals being of equal frequency but out of phase with each other, means for comparing the two signals for servoing the movable member to positions related to the intersections of the two signals, a summing junction including means to compare the sum of the two signals with a known signal for generating a first error signal, a second means for comparing the two signals to generate a second error signal proportional to the algebraic difference between the two signals, means for adjusting the transducers in response to the first and second error signals to maintain the amplitude and gain of the transducer signals approximately equal.

Claim 6

In a servomechanism for positioning a movable member, apparatus for accurately maintaining the member in a position at a given location along the path of movement of the member, including, a pair of transducers each including means for producing an alternating signal indicative of movement of the movable member, said alternating signals being of equal frequency but out of phase with each other, means for comparing the two signals for servoing the movable member to positions related to the intersections of the two signals, a summing junction including means to compare the sum of the two signals with a known signal for generating a first error signal, a second means for comparing the two signals to generate a second error signal proportional to the algebraic difference between the two signals, means for adjusting the transducers in response to the first and second error signals to maintain the amplitude and gain of the transducer signals approximately equal.

Claim 7

Apparatus as defined in claim 4 wherein the transducers include a stationary grating and movable gratings fixed to the movable member, and light sources and cooperating photoelectric sensors for generating the alternating signals.

Claim 8

In an access mechanism for a data storage device which includes a linear actuator operatively connected to an array of read/write heads, apparatus for accurately maintaining the head array in position at a given track location on a rotating recording disc, including: a transducer, which generates two alternating signals of the same frequency but 180* phase relation, including a fixed element and a movable element for producing a continuous signal indicative of the instantaneous position of the head array; means for servoing the head array onto the signal; said means including means for combining the two signals and servoing the head array onto the intersection of the signals; means for continuously monitoring the signal to maintain a constant ratio of signal strength to increment of displacement of the head array from the track centerline; means for applying a small constant frequency oscillation to the mechanism to insure relative movement between the movable and the fixed elements of the transducer at all times.

Claim 9

In an access mechanism for a data storage device which includes a linear actuator operatively connected to an array of read/write heads, apparatus for accurately maintaining the head array in position at a given track location on a rotating recording disc, including: a transducer, which generates two alternating signals of the same frequency but 180* phase relation, including a fixed element and a movable element for producing a continuous signal indicative of the instantaneous position of the head array; means for servoing the head array onto the signal; said means including means for combining the two signals and servoing the head array onto the intersection of the signals; means for continuously monitoring the signal to maintain a constant ratio of signal strength to increment of displacement of the head array from the track centerline; means for applying a small constant frequency oscillation to the mechanism to insure relative movement between the movable and the fixed elements of the transducer at all times.