Electricity: motive power systems – Switched reluctance motor commutation control
Patent
1993-06-15
1995-11-14
Ro, Bentsu
Electricity: motive power systems
Switched reluctance motor commutation control
318431, H02P 614, H02P 620
Patent
active
054669979
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to motor control systems, and more particularly to a spin motor control system for disk drive apparatus.
2. Description of the Relevant Art
Magnetic disk storage systems such as hard disk drive systems and floppy disk drive systems have been and continue to be the predominant mechanisms for providing large volumes of relatively low-cost computer accessible memory or storage. A typical hard disk drive system includes a number of adjacently positioned disks coated with an appropriate magnetic material that are mounted for rotation on a common spindle. The typical system further includes a set of transducer heads carried in pairs on elongated supports for insertion between adjacent disks wherein the heads of each pair face in opposite directions to engage opposite surfaces of the adjacent disks. The transducer heads transform magnetic variations into electric variations when reading data stored on the disks, and transform electric variations to magnetic variations when writing data to be stored on the disks. The support structure is coupled to a positioner motor that typically includes a coil mounted within a magnetic field for linear movement and is typically oriented relative to the disks to move the heads radially over the disk surfaces to thereby enable the heads to be positioned over any annular track on the surfaces. During normal operation, the positioner motor, in response to control signals from a host computer, positions the transducer heads radially for recording data signals on, or retrieving data signals from, a pre-selected one of a set of concentric storage tracks on the disks.
A typical hard disk drive system also includes a spin motor operatively connected to the spindle for rotating the magnetic disks during data read and data write operations. An electronic control and driving circuit is coupled between the spin motor and the host microprocessor interface to provide drive signals to the motor windings to thereby control the speed and other operating parameters of the spin motor, as well as to control initial start-up of the spin motor.
FIG. 1 is a schematic view of a portion of a three-phase brushless spin motor 10 connected to associated control and drive circuitry. For the particular example illustrated herein, spin motor 10 is a twelve pole motor having nine windings. The nine windings are grouped into three sets, wherein each winding set is selectively driven at a predetermined phase and is represented by one of phase windings 12, 14, 16. As known to those skilled in the art, a sequencer 18 and a motor amplifier 20 collectively operate to selectively drive the phase windings 12, 14, 16 in a manner as explained below to thereby induce rotation of the rotor shaft of motor 10.
Referring next to FIG. 2A in conjunction with FIG. 1, traces 1, 2, and 3 illustrate the motor torque generated when a constant current flows through selected pair combinations of phase windings 12, 14, 16 with respect to motor electrical degrees. Trace 1 shows the motor torque curve with respect to electrical degrees when transistors 20a and 20f are turned on (20b-20e turned off), resulting in the flow of current from phase A winding 12 to phase C winding 16. Similarly, trace 2 shows the motor torque curve on the common horizontal axis when transistors 20a and 20d are turned on, resulting in the flow of current from phase A winding 12 to phase B winding 14. Finally, trace 3 shows the motor torque curve when transistors 20d and 20e are turned on, resulting in the flow of current from phase C winding 16 to phase B winding 14. The extremum torque points occur 60 electrical degrees apart. For a twelve pole motor, 360 electrical degrees correspond equivalently to 1/6 of a mechanical revolution of the rotor.
To spin the rotor in one continuous direction, the motor torque must be either continuously positive or continuously negative. A continuously positive motor torque, for example, can be provided by designing and controlling sequencer 18
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Blagaila John H.
Utenick Michael R.
Integral Peripherals, Inc.
Ro Bentsu
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