Method for fine actuation of a head during operation of a disk drive
View Patent ↗A disk drive includes a voice coil actuator, and a rotary fine actuator that is attached to the head mounting tongue of the flexure of a suspension assembly. The head is positioned during operation of the disk drive by a novel method. An electrical current is driven through a coil of the voice coil actuator to torque it towards a desired coarse position. First and second voltages are applied across first and second piezoelectric elements attached to the flexure, respectively. The first and second voltages cause longitudinal deformation of the first and second piezoelectric elements, respectively, the longitudinal deformation consisting of expansion relative to a zero-voltage state. The first and second voltages do not switch polarity during normal operation of the first and second piezoelectric elements.
1. A method to position a head during operation of a disk drive, the head being attached to a flexure of a suspension assembly, the suspension assembly being attached to a voice coil actuator having an actuator coil, the method comprising:
driving an electrical current through the actuator coil to move the voice coil actuator towards a coarse position;
applying a first voltage across a first piezoelectric element attached to the flexure, the first voltage causing a longitudinal deformation of the first piezoelectric element consisting of expansion relative to a zero-voltage state;
applying a second voltage across a second piezoelectric element attached to the flexure, the head being disposed between the first and second piezoelectric elements, the second voltage causing a longitudinal deformation of the second piezoelectric element consisting of expansion relative to a zero-voltage state;
wherein the first and second voltages do not switch polarity during normal operation of the first and second piezoelectric elements.
2. The method of claim 1 wherein driving the electrical current through the actuator coil torques the voice coil actuator towards a coarse position, and applying the first and second voltages causes the head to rotate to a fine position.
3. The method of claim 1 wherein the suspension assembly is attached to the voice coil actuator by a swage connection.
4. The method of claim 1 wherein the flexure includes a structural layer, a dielectric layer, and a conductive layer that defines a plurality of conductive traces, and wherein the head is electrically connected to more than one of the plurality of conductive traces, and the first and second piezoelectric elements are each electrically connected to at least one of the plurality of conductive traces.
5. A method to position a head during operation of a disk drive, the head being attached to a flexure of a suspension assembly, the suspension assembly being attached to a voice coil actuator having an actuator coil, the method comprising:
driving an electrical current through the actuator coil to move the voice coil actuator towards a coarse position;
applying a first voltage across a first piezoelectric element attached to the flexure, the first voltage causing a longitudinal deformation of the first piezoelectric element consisting of expansion relative to a zero-voltage state;
applying a second voltage across a second piezoelectric element attached to the flexure, the second voltage causing a longitudinal deformation of the second piezoelectric element consisting of expansion relative to a zero-voltage state;
wherein the first and second voltages do not switch polarity during normal operation of the first and second piezoelectric elements; and
wherein the first voltage and the second voltage are the same.
6. A method to position a head during operation of a disk drive, the head being attached to a flexure of a suspension assembly, the suspension assembly being attached to a voice coil actuator having an actuator coil, the method comprising:
driving an electrical current through the actuator coil to move the voice coil actuator towards a coarse position;
applying a first voltage across a first piezoelectric element attached to the flexure, the first voltage causing a longitudinal deformation of the first piezoelectric element consisting of expansion relative to a zero-voltage state;
applying a second voltage across a second piezoelectric element attached to the flexure, the second voltage causing a longitudinal deformation of the second piezoelectric element consisting of expansion relative to a zero-voltage state;
wherein the first and second voltages do not switch polarity during normal operation of the first and second piezoelectric elements; and
wherein the first voltage and the second voltage are never zero during normal operation of the first and second piezoelectric elements.
7. The method of claim 6 wherein the first voltage is time varying and fluctuates about a DC bias voltage, said fluctuation never exceeding a magnitude of the DC bias voltage.
8. The method of claim 6 wherein the second voltage is time varying and fluctuates about a DC bias voltage, said fluctuation never exceeding the DC bias voltage.
9. A method to position a head during operation of a disk drive, the head being attached to a flexure of a suspension assembly, the suspension assembly being attached to a voice coil actuator having an actuator coil, the method comprising:
driving an electrical current through the actuator coil to move the voice coil actuator towards a coarse position;
applying a first voltage across a first piezoelectric element attached to the flexure, the first voltage causing a longitudinal deformation of the first piezoelectric element consisting of expansion relative to a zero-voltage state;
applying a second voltage across a second piezoelectric element attached to the flexure, the second voltage causing a longitudinal deformation of the second piezoelectric element consisting of expansion relative to a zero-voltage state;
wherein the first and second voltages do not switch polarity during normal operation of the first and second piezoelectric elements; and
wherein the first piezoelectric element and the second piezoelectric element are bonded to mounting surfaces of a fine rotary actuator that is attached to a tongue of the flexure.
10. A method to position a head during operation of a disk drive, the head being attached to a flexure of a suspension assembly, the suspension assembly being attached to a voice coil actuator having an actuator coil, the method comprising:
driving an electrical current through the actuator coil to move the voice coil actuator towards a coarse position;
applying a first voltage across a first piezoelectric element attached to the flexure, the first voltage causing a longitudinal deformation of the first piezoelectric element consisting of expansion relative to a zero-voltage state;
applying a second voltage across a second piezoelectric element attached to the flexure, the second voltage causing a longitudinal deformation of the second piezoelectric element consisting of expansion relative to a zero-voltage state;
wherein the first and second voltages do not switch polarity during normal operation of the first and second piezoelectric elements; and
wherein the first piezoelectric element and the second piezoelectric element are embedded into windows in a frame of a fine rotary actuator that is attached to a tongue of the flexure.
11. A method to position a head during operation of a disk drive, the head being attached to a flexure of a suspension assembly, the suspension assembly being attached to a voice coil actuator having an actuator coil, the method comprising:
driving an electrical current through the actuator coil to move the voice coil actuator towards a coarse position;
applying a first voltage across a first piezoelectric element attached to the flexure, the first voltage causing a longitudinal deformation of the first piezoelectric element consisting of expansion relative to a zero-voltage state;
applying a second voltage across a second piezoelectric element attached to the flexure, the second voltage causing a longitudinal deformation of the second piezoelectric element consisting of expansion relative to a zero-voltage state;
wherein the first and second voltages do not switch polarity during normal operation of the first and second piezoelectric elements; and
wherein each of the first and second piezoelectric elements has an anchored end that does not substantially move relative to a tongue of the flexure when the first and second piezoelectric elements are caused to deform, and an actuated end that does not substantially move relative to the head when the first and second piezoelectric elements are caused to deform, and wherein the anchored end of the first piezoelectric element is disposed closer to the actuator coil than is a centroid of the head, and the anchored end of the second piezoelectric element is disposed further from the actuator coil than is the centroid of the head.