Polyphase brushless DC Motor control

• US 5,223,771 A
• Filed: 09/25/1992
• Issued: 06/29/1993
• Est. Priority Date: 06/17/1991
• Status: Expired due to Term

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital (Thailand) Company Limited (Western Digital Corporation)
• Inventors: Chari, Srinivasan V.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US07/951,378
• Time in Patent Office: 277 Days
• Field of Search: 318/138, 318/254, 318/439
• US Class Current: 318/400.09
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: H02P 6/22 in a selected direction of rotation

Abstract

A system for controlling the operation of a polyphase DC motor having a rotor and a plurality of phase windings with separate outer terminals and a common center tap terminal supplies electrical energy sequentially to the phase windings to produce rotation of the rotor relative to the phase windings. The voltage between the outer terminal of one of the phase windings and the center tap terminal is sensed during periods when that one phase winding is not energized to control the sequential supplying of electrical energy to the phase windings.

Claims

1. Motor driver circuitry for controlling the operation of a brushless DC type motor to rotate revolving magnetic disks in a hard disk drive, the motor being of the type having a permanent magnet rotor connected to the revolving magnetic disks and magnetically coupled to a stator including a plurality of phase windings each having an outer terminal and a common center terminal configured to be individually energized in a sequence to cause the rotor to rotate unidirectionally, the motor drive circuitry comprising;

sensing circuit means connected between the common center terminal and an outer terminal of one of the plurality of phase windings for determining an initial angular position of the rotor;

timing circuit means for providing a timing reference signal synchronized with the rotor to define a succession of time intervals such that each time interval marks the movement of the rotor through a known rotation angle;

a micro processor including;

first sequencing means having a first and a second operational phase, said first sequencing means being responsive to the determined initial angular position of the rotor for providing an energization signal to said phase windings to cause the rotor to move in a single direction to a predetermined angular position with respect to the stator phase windings in the first operational phase, said first sequencing means thereafter supplying a sequence of energization signals to said phase windings to cause the rotor to rotate from its initial position and accelerate to a predetermined intermediate rotational velocity in the second operational phase;

second sequencing means having a signal processing input for receiving said timing reference signal, said second sequencing means successively providing a stator phase winding energization sequence to cause the rotor to accelerate from the predetermined intermediate rotational velocity to a predetermined final rotational velocity, said second sequencing means having means for periodically comparing a time interval of the timing reference signal to a corresponding time interval of the energization sequence and for computing a next phase winding energization sequence for use in correcting any error in rotor angular velocity;

control circuit means for providing a control signal when the desired final rotational velocity is reached; and

commutator circuit means having a signal processing input for receiving the said reference signal and having a control input for receiving said control signal, said commutator circuit means being responsive to said control signal and having means responsive to said timing reference signal for providing a phase winding energization sequence to cause the rotor to maintain its predetermined final rotational velocity.

2. Motor driver circuitry in accordance with claim 1, wherein said commutator circuit means further includes first signal storing circuit means responsive to said timing reference signal for producing and temporarily storing a stored signal that represents at least one integer multiple of an actual time interval of rotor rotation.

3. Motor drive circuitry in accordance with claim 2, wherein said microprocessor compares the stored actual time interval of rotor rotation to a desired time interval of rotor rotation and calculates a set of operational signals for use in correcting any error in actual rotor rotational velocity from its desired final rotational velocity.

4. Motor driver circuitry in accordance with claim 3, wherein said commutator circuit means further includes second signal storing circuit means for receiving and temporarily storing the set of calculated operational signals from said microprocessor such that each signal in the set represents a commutation parameter used to provide a phase winding energization sequence.

5. A method for controlling the operation of a brushless DC type motor to rotate revolving magnetic disks in a hard disk drive, the motor being of the type having a permanent magnet rotor connected to the revolving magnetic disks and magnetically coupled to a stator including a plurality of phase windings each having an outer terminal and a common center terminal configured to be individually energized in a sequence to cause the rotor to rotate unidirectionally, comprising the steps of;

sensing the voltage between the common center terminal and an outer terminal of one of the plurality of phase windings to determine an initial angular position of the rotor;

providing a timing reference signal synchronized with the rotor to define a succession of time intervals such that each time interval marks the movement of the rotor through a known rotation angle;

providing a first sequencing means having a first and a second operational phase, said first sequencing means being responsive to the determined initial angular position of the rotor for providing an energization signal to said phase windings to cause the rotor to move in a single direction to a predetermined angular position with respect to the stator phase windings in the first operational phase,

thereafter supplying a sequence of energization signals from said first sequencing means to said phase windings to cause the rotor to rotate from its initial position and accelerate to a predetermined intermediate rotational velocity in the second operational phase;

providing a second sequencing means having a signal processing input for receiving said timing reference signal, said second sequencing means successively providing a stator phase winding energization sequence to cause the rotor to accelerate from the predetermined intermediate rotational velocity to a predetermined final rotational velocity, said second sequencing means periodically comparing a time interval of the timing reference signal to a corresponding time interval of the energization sequence and computing a next phase winding energization sequence for use in correcting any error in rotor angular velocity;

providing a control signal when the desired final rotational velocity is reached; and

processing said timing reference signal and said control signal for providing a phase winding energization sequence to cause the rotor to maintain its predetermined final rotational velocity.

6. A method in accordance with claim 5, including the steps of producing and temporarily storing a stored signal that represents at least one integer multiple of an actual time interval of rotor rotation.

7. A method in accordance with claim 6, including the steps of comparing actual time interval of rotor rotation to a desired time interval of rotor rotation;

and

calculating a set of operational signals for use in correcting any error in actual rotor rotational velocity from its desired final rotational velocity.

8. A method in accordance with claim 7, including the step of receiving and temporarily storing the set of calculated operational signals from a microprocessor such that each signal in the set represents a commutation parameter used to provide a phase winding energization sequence.