Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2000-02-11
2003-07-29
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S075000, C360S077030
Reexamination Certificate
active
06600622
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates in general to an improved disk drive and in particular to detecting displacement of the actuator in a disk drive. Still more particularly, the invention relates to using the micro actuator transducer in a disk drive as a sensor for sensing head displacement due to contact with a rotating disk.
2. Description of the Prior Art
A disk drive utilizes actuators for reading and writing data to its rotating disks. The radial positions of the actuators, relative to tracks on the disks, are typically controlled by a transducer in a closed-loop servo system. Some disk drives utilize two-stage actuators for reading and writing to the disks. A two-stage actuator comprises a primary actuator arm and a micro actuator arm that is pivotally mounted to and extends from a distal end of the primary actuator arm. The micro actuator arm has one or more heads on its distal end for interacting with a respective disk. The micro actuator arm also has a smaller mass and therefore significantly higher mechanical bandwidth than the primary actuator arm.
During operation of the disk drive, the heads on the micro actuator arms occasionally will contact the spinning disks, thereby subjecting the micro actuator arms to radial displacement relative to the disks. In the prior art, in-situ schemes such as magnetic envelope or thermal MR sensing are used to detect this displacement. Magnetic sensing is difficult in that one must distinguish between track misregistrations from head-disk contact events. Moreover, thermal MR measurements require additional drive circuitry which adds significant cost to the device.
However, the relative displacement of the distal and proximal ends of the micro actuator arms are indicative of the sliding forces generated during head-disk contacts. Since these contact-generated displacements did not originate from the controlling servo system, they appear as intermittent signals that are unlikely to occur during position error signal measurements. Thus, it would be desirable to control the micro actuator arm while distinguishing disk contact with the micro actuator arm without adding additional circuitry. Such a system for controlling and monitoring the actuator would be both simpler and more robust than prior art methods.
SUMMARY OF THE INVENTION
The present invention utilizes a disk drive with a simple detector circuit that is connected to the distal end of a two-stage actuator. The actuator has a micro actuator that is used for fine track positioning of a read/write head relative to a disk. Intermittent contact between the head on the micro actuator and the disk produces forces that are detected and measured by the micro actuator drive circuitry. These measurements are used to determine if excessive contact is occurring between the head and its respective disk, and for predictive failure analysis or recovery operations.
Alternatively, the present invention also comprises a differential method where the output signals from multiple micro actuators are compared in order to improve noise immunity. In addition, comparisons between the forces at the proximal and distal ends of any of the micro actuators are used to better identify the source of such forces. For example, this allows the system to distinguish between common mode forces such as those generated by windage and flex cable bias, from forces generated by intermittent head-disk contacts.
Another embodiment of the invention is to use the micro actuator as a detector for slider-disk contact that does not utilize a position error signal. In this mode, the track position is maintained by using the arm actuator. A signal from the micro actuator is used to electronically detect the slider-disk contact. The signal is available since the motor also functions as a generator, e.g., piezoelectric or voice coil-based micro actuators, or any micro actuator that is capable of generating a signal in response to an applied force or displacement.
Accordingly, it is an object of the present invention to provide an improved disk drive.
It is an additional object of the present invention to provide a system and method for detecting displacement of the actuator in a disk drive.
Still another object of the present invention is to use the micro actuator transducer in a disk drive as a sensor for sensing head displacement due to contact with a rotating disk.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the preferred embodiment of the present invention, taken in conjunction with the appended claims and the accompanying drawings.
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Bracewell & Patterson LLP
Habermehl James L
Hitachi Global Storage Technologies - Netherlands B.V.
Hudspeth David
Truelson Roy W.
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