Method and apparatus of micro-actuator control of the flying height of a read/write head in a hard disk drive
View Patent ↗Read-write head flying height controlled through micro-actuator assembly. Flying height controlled using DC line and ground line. Lateral position controlled using them and AC line. Micro-actuator assembly operates through three terminals coupled with these lines. Head gimbal assembly contains micro-actuator assembly mechanically coupling to slider with read-write head. Actuator arm includes at least one head gimbal assembly. Actuator arm assembly includes at least one actuator arm. Voice coil actuator includes actuator assembly. Hard disk drive containing voice coil actuator. Electrical interface circuit includes ground port, DC port, and AC port, for micro-actuator assembly. Servo controller drives micro-actuator assembly to control flying height and lateral position, preferably including electrical interface circuit. Manufacturing head gimbal assembly, actuator arm, actuator assembly, voice coil actuator, and hard disk drive, and products of these manufacturing processes.
1. A method controlling a read-write head coupled with a micro-actuator assembly in a hard disk drive, comprising the steps:
controlling a flying height of said read-write head off a rotating disk surface using a Direct Current (DC) line and a ground line, both electrically coupled with said micro-actuator assembly; and
controlling a lateral position of said read-write head over said rotating disk surface, using an Alternating Current (AC) line, said ground line and said DC line;
wherein the step controlling said flying height further comprises the steps:
applying a high DC voltage to said DC line relative to said ground line to induce said micro-actuator assembly to position said read-write head within said flying height off said rotating disk surface; and
applying a near-zero DC voltage to said DC line relative to said ground line to induce said micro-actuator assembly to position said read-write head above said flying height off said rotating disk surface.
2. The method of claim 1 , further comprising at least one of:
using a piezoelectric effect to control said lateral position; and
employing another piezoelectric effect to position said read-write head flying height over said rotating disk surface.
3. The method of claim 1 , wherein the step controlling said lateral position further comprises at least one of the steps:
controlling said lateral position of said read-write head over a track on said rotating disk surface when said high DC voltage is applied to said DC line;
following said track on said rotating disk surface while said high DC voltage is applied to said DC line; and
seeking said track on said rotating disk surface while said near-zero DC voltage is applied to said DC line.
4. The method of claim 3 , further comprising the step:
altering said high DC voltage by a DC increment to alter said flying height.
5. The method of claim 1 , further comprising:
simultaneously controlling lateral positions of additional read-write heads over additional rotating disk surfaces using additional AC lines electrically coupled with additional micro-actuator assemblies; and
controlling read-write head flying heights over said additional rotating disk surfaces using DC and ground lines electrically coupled with a respective additional micro-actuator assembly.
6. A micro-actuator assembly, comprising:
means for controlling a flying height of a read-write head off a rotating disk surface using a Direct Current (DC) line and a ground line, both electrically coupled with a micro-actuator assembly, and for applying a high DC voltage to said DC line relative to said ground line to induce said micro-actuator assembly to position said read-write head within said flying height off said rotating disk surface, and for applying a near-zero DC voltage to said DC line relative to said ground line to induce said micro-actuator assembly to position said read-write head above said flying height off said rotating disk surface;
means for controlling a lateral position of said read-write head over said rotating disk surface, using an Alternating Current (AC) line, said ground line and said DC line;
a ground terminal for electrically coupling to said ground line, a DC terminal for electrically coupling to said DC line, whereby said micro-actuator assembly responds to DC voltages to change the flying height of said read-write head above said rotating disk surface; and
an AC terminal for electrically coupling to said AC line, whereby said micro-actuator assembly responds to AC voltages to laterally position said read-write head.
7. The micro-actuator assembly of claim 6 , further comprising:
a planar micro-actuator electrically connected to said ground terminal, said AC terminal and said DC terminal to implement electrical control of said lateral position of said read-write head; and
a vertical micro-actuator electrically connected to said ground terminal and said DC terminal to implement electrical control of said read-write head above said rotating disk surface.
8. The micro-actuator assembly of claim 7 , wherein said planar micro-actuator further comprises:
a first planar micro-actuating arm electrically connected to said ground terminal and said AC terminal to provide a first contribution to move said lateral position of said read-write head;
a second planar micro-actuating arm electrically connected to said AC terminal and said DC terminal to provide a second contribution to move said lateral position of said read-write head.
9. The micro-actuator assembly of claim 8 ,
wherein said first planar micro-actuating arm employs a first piezoelectric effect;
wherein said second planar micro-actuating arm employs a second piezoelectric effect; and
wherein said vertical micro-actuator employs a third piezoelectric effect.
10. The micro-actuator assembly of claim 6 , further including an electrical interface circuit comprising:
a ground port electrically connected with said ground line;
a DC port electrically connected with said DC line; and
a Digital to Analog Converter (DAC) to at least partly drive an AC port connected to said AC line and thereby provides digital control of read-write head lateral positions supported by a program system and a memory.
11. The electrical interface circuit of claim 10 , further comprising
one of a switch controllably coupling said DC port with one of said high DC voltage and said near-zero voltage; and
a second DAC that at least partly drives said DC port line and thereby provides digital control of read-write head flying heights supported by a program system and a memory.
12. The electrical interface circuit of claim 10 , further comprising:
an integrated circuit providing said ground port, said DC port, and said AC port.
13. The electrical interface circuit of claim 10 , further comprising at least one of:
a voice coil responsive to a control signal for further control of said lateral position of said read-write head; and
a spindle motor responsive to a control signal for rotating a disk surface.
14. A head gimbal assembly, comprising:
a micro-actuator assembly with means for controlling a flying height of a read-write head off a rotating disk surface using a Direct Current (DC) line and a ground line, both electrically coupled with a micro-actuator assembly, and for applying a high DC voltage to said DC line relative to said ground line to induce said micro-actuator assembly to position said read-write head within said flying height off said rotating disk surface, and for applying a near-zero DC voltage to said DC line relative to said ground line to induce said micro-actuator assembly to position said read-write head above said flying height off said rotating disk surface, and further including means for controlling a lateral position of said read-write head over said rotating disk surface, using an Alternating Current (AC) line, said ground line and said DC line;
a ground terminal for electrically coupling to said ground line, a DC terminal for electrically coupling to said DC line, whereby said micro-actuator assembly responds to DC voltages to change the flying height of said read-write head above said rotating disk surface;
an AC terminal for electrically coupling to said AC line, whereby said micro-actuator assembly responds to AC voltages to laterally position said read-write head;
wherein the micro-actuator assembly is connected to a slider embedded with a read-write head; and further comprising:
said ground line is electrically connected to said ground terminal; said AC line is electrically connected to said AC terminal; and
said DC line is electrically connected to said DC terminal.
15. A hard disk drive, comprising:
a micro-actuator assembly with means for controlling a flying height of a read-write head off a rotating disk surface using a Direct Current (DC) line and a ground line, both electrically coupled with a micro-actuator assembly, and for applying a high DC voltage to said DC line relative to said ground line to induce said micro-actuator assembly to position said read-write head within said flying height off said rotating disk surface, and for applying a near-zero DC voltage to said DC line relative to said ground line to induce said micro-actuator assembly to position said read-write head above said flying height off said rotating disk surface, and further including means for controlling a lateral position of said read-write head over said rotating disk surface, using an Alternating Current (AC) line, said ground line and said DC line;
a voice coil actuator; and
a servo controller with a DC line output and an AC line output for respectively controlling a flying height and a lateral position of said read-write head off said rotating disk surface.
16. The hard disk drive of claim 15 , wherein said servo controller is responsive to a computer memory and a program system for controlling said flying height of said read-write head off said rotating disk surface using said DC line and said ground line; and for controlling said lateral position of said read-write head over said rotating disk surface, using said AC line, said ground line and said DC line.
17. The hard disk drive of claim 16 , wherein said computer controls a voice coil actuator to further control said lateral position of said read-write head.