Electricity: motive power systems – Positional servo systems
Reexamination Certificate
1998-03-27
2001-04-03
Sircus, Brian (Department: 2837)
Electricity: motive power systems
Positional servo systems
C318S615000, C360S078090, C360S078050
Reexamination Certificate
active
06211638
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to a method and apparatus for controlling a reluctance force motor and, more particularly, to a method and apparatus for linearizing the control of a reluctance force motor having a nonlinear transfer function.
BACKGROUND OF THE INVENTION
Hard disk drive systems have a rotating magnetic disk, an arm movable under control of an actuator which is a voice coil motor, and a read/write head supported on the arm and disposed adjacent to the rotating disk. In response to movement of the arm, the read/write head moves approximately radially of the disk. Some hard disk drive systems of this general type also include a microactuator, which is disposed between the read/write head and the arm, and which can effect movement of the read/write head relative to the arm in a direction radially of the disk. The microactuator can move the read/write head more rapidly than the voice coil motor, but has a substantially smaller range of movement. Therefore, the voice coil motor and moveable arm are used to effect coarse positioning of the read/write head relative to the disk, and the microactuator is used to effect fine positioning of the read/write head relative to the disk.
Such a microactuator may typically include at least one reluctance force motor, such as an electromagnet arrangement having a coil which can be electrically energized to operate the microactuator. One particular type of microactuator has such a reluctance force motor with a highly nonlinear transfer function. In other words, the movement of the read/write head which is effected by the microactuator varies in a highly nonlinear manner with respect to linear variations in a control signal supplied to the microactuator. This nonlinear transfer function of the microactuator creates a relatively complex design problem with respect to development of a control system or control loop to generate the control signal for the microactuator, because a nonlinear control loop is much more complex and difficult to design than a linear control loop.
SUMMARY OF THE INVENTION
From the foregoing, it may be appreciated that a need has arisen for a method and apparatus for controlling a microactuator or other reluctance force motor which has a nonlinear transfer function, and that there is a need for simplifying the design and complexity of a control system or control loop which generates a control signal for such a reluctance force motor. According to the present invention, in order to address this need, a method and apparatus are provided for controlling an apparatus which includes a reluctance force motor having a drive arrangement operative to effect movement of a member away from an initial position in response to a control signal, the drive arrangement having a nonlinear transfer function which causes a displacement of the member from the initial position to vary nonlinearly with respect to variation of the control signal. The method and apparatus involve generating a parameter that represents a desired force to be exerted on the member in order to effect movement of the member away from the initial position thereof, and generating the control signal in response to the parameter according to a nonlinear transfer function which is substantially an inverse of the nonlinear transfer function of the drive arrangement.
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DiRenzo Michael T.
Heaton Mark W.
Masten Michael K.
Brady III Wade James
Sircus Brian
Swayze, Jr. W. Daniel
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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