Method and apparatus for brushless DC motor speed control

A method of initiating and controlling the rotation of a rotor of a brushless DC motor of the type having multiple windings, related as phases, for conducting torque-producing current therethrough, comprising the steps of:

• sequentially powering each phase of the DC motor for a short predetermined time period;
• obtaining a peak amplitude value of the current conducted by the motor when a phase is powered during each corresponding short predetermined time period;
• determining a one-peak amplitude value having a magnitude greater than the other peak amplitude values;
• and
• applying a torque-producing current to the DC motor in a phase determined by the determined one-peak amplitude value.

A commutatorless direct current motor having a rotor for rotating with respect to a stator, said motor comprising:

• (a) means, provided on the rotor, for establishing a plurality of first magnetic fields;
• (b) means, provided on the stator, for inducing a second magnetic field;
• and
• (c) control means, coupled to said inducing means, for directing a discrete short-period inducement of said second magnetic field and a discrete long-period inducement of said second magnetic field wherein said discrete short period inducement is insufficient to cause rotation of said rotor and said discrete long-period inducement is sufficient to cause rotation of said rotor, said control means including means for monitoring the interaction of said discrete short-period induced second magnetic field with said first magnetic fields.

A commutatorless direct current motor having a rotor for rotating with respect to a stator, said motor comprising:

• (a) means, provided on the rotor, for establishing a plurality of first magnetic fields;
• (b) means, provided on the stator, for inducing a second magnetic field, said inducing means including a plurality of windings;
• and
• (c) control means, coupled to said inducing means, for directing a short-period inducement of said second magnetic field, said control means including means for monitoring the interaction of said short-period induced second magnetic field with said first magnetic fields, wherein each short-period inducement of said second magnetic field is obtained by the application of a current pulse through a respective phase pair of said windings as selected by said control means, wherein said monitoring means monitors the current pulse response of each said phase pair of said windings.

In a commutatorless direct current motor having an armature and a multiple-magnet rotor, wherein said armature includes a plurality of windings for generating torque-inducing magnetic fields in response to current pulses and wherein:

• said multiple-magnet rotor is caused to rotate between rotational positions relative to said armature in response to the application of long-duration current pulses to the windings, an improvement permitting the unique armature relative rotational position of said multiple-magnet rotor to be identified exclusively through the use of said windings as positional sensors, said improvement comprising:
• (a) control means for applying a a respective short-duration current pulse to each phase pair of said windings, said short-duration current pulses being insufficient to rotate said multiple-magnet rotor between rotational positions;
• and
• (b) means for detecting the respective response of the phase pairs of said windings to said short-duration current pulse.

A commutatorless direct current motor comprising:

• (a) an armature including a plurality of windings having first and second ends, said first ends of said windings being connected together, whereby sets of two said second ends define phase pairs of said windings;
• (b) a permanent magnet motor assembly including a plurality of magnets and rotatable with respect to said armature;
• and
• (c) control means, coupled to said respective second ends of said windings, for directing the operation of said motor, said control means including means for selectively providing commutation power to phase pairs of said windings, means for successively applying a short-duration current pulse to each phase pair of said windings, means for detecting a peak voltage developed across said second ends of each phase pair of said windings, means for comparing the detected peak voltages of each phase pair of said windings, and means for identifying a specific one of said magnets as being positionally related to the one of the phase pairs of said windings corresponding to a largest phase pair peak voltage detected.

A system for controlling the rotation of a motor having a rotor with multiple magnetic poles and a stator with a plurality of windings permitting the conduction of torque inducing current therein, said system comprising:

• (a) means for selecting windings for the conduction of current to cause rotation of the rotor;
• (b) means for applying a short-duration current pulse to selected ones of the windings;
• and
• (c) control means, responsive to the characteristics of the response of the windings to the application of the short-duration current pulse, for controlling said selecting means and said applying means to determine the unique position of the magnetic poles of the rotor with respect to the windings, said control means including means for sensing the peak voltage developed by the selected ones of the windings in response to the application of the short-duration current pulse.

A control system for providing rotation control of a hard-disk drive spin motor wherein the spin motor includes a rotor having a plurality of permanent magnet poles and a stator having a plurality of windings, each winding having first and second ends with the first ends of the windings being interconnected, said control system comprising:

• (a) a spin motor driver coupled to the second ends of the windings for conducting current pulse through phase pairs of the windings defined by pairs of second ends, said spin motor driver providing a sense signal proportional to the magnitude of the current pulse conducted through the windings;
• (b) a control circuit coupled to said spin motor drive to provide control signals for the selection of phase pairs of windings for the conduction of the current pulse, said control circuit including timing means for establishing the period of the application of respective current pulses to phase pairs of windings including a long-duration period current pulse to induce the rotation of the rotor to a different pole position with respect to the windings and a short-duration period current pulse wherein the short-duration current pulse conducted by a selected phase pair of windings is less than sufficient to induce rotation of the rotor to a different pole position with respect to the windings, said control circuit including microprocessor means, responsive to said sense signal as respectively produced in response to the conduction of current pulse for a short-duration period by each of the phase pairs of windings, for determining the unique pole position of the rotor with respect to the phase pairs of windings.

A method of operating a control system for providing rotation control of a hard-disk drive spin motor, wherein the spin motor includes a rotor having a plurality of permanent magnet poles and a stator having a plurality of windings, each winding having first and second ends with the first ends of the windings being interconnected and wherein a spin motor drive current circuit is coupled to the second ends of the windings for switching current through phase pairs of the windings as defined by pairs of said second ends, said spin motor drive current circuit providing a sense signal proportional to the magnitude of the current conducted through the phase pairs of windings, the method comprising the steps of:

• (a) applying a short-duration period current pulse to each phase pair of windings, where said short-duration current pulse is insufficient to cause rotation of said rotor to the next pole position relative to said stator;
• (b) acquiring the sense signal produced by said spin motor drive current circuit in response to the respective application of the short-duration period current pulses;
• (c) comparing the sense signals acquired to identify a phase pair of windings corresponding to an acquired sense signal distinguishable from the remaining acquired sense signals;
• and
• (d) selecting a phase pair of windings for the conduction of a long-duration period current pulse to induce rotation of the rotor.

A method of operating a control system in hard-disk media for providing rotation control of a hard-disk drive spin motor, wherein the spin motor includes a rotor having a plurality of permanent magnet poles and a stator having a plurality of windings, each winding having first and second ends with the first ends of the windings being interconnected and wherein a spin motor drive current circuit is coupled to the second ends of the windings for switching current through phase pairs of the windings as defined by pairs of said second ends, said spin motor drive current circuit providing a sense signal proportional to the magnitude of the current conducted through the phase pairs of windings, the method comprising the steps of:

• (a) initiating the rotation of the rotor to a first predetermined rotation rate by repeating the steps of:
• (i) applying a short-duration period current pulse to a phase pair of windings, where said short-duration current pulse is insufficient to cause rotation of said rotor to the next pole position relative to said stator;
• (ii) acquiring the sense signal produced by said spin motor drive current circuit in response to the application of the short-duration period current pulse;
• (iii) comparing the sense signals acquired for each phase pair of windings to identify a phase pair of windings corresponding to an acquired sense signal distinguishable from the remaining acquired sense signals;
• and
• (iv) selecting a phase pair of windings for the conduction of current to induce rotation of the rotor;
• (b) increasing the rotation rate of the motor to a second predetermined rate by repeating the steps of:
• (i) sensing the back-EMF developed in the phase pairs of windings;
• and
• (ii) providing current to a next phase pair of windings selected from a predetermined series of phase pair winding commutation states in response to the sensing of a predetermined level of back-EMF;
• and
• (c) maintaining the rotation race of the rotor at a third predetermined rate by repeating the steps of:
• (i) receiving rotation rate feedback information from the hard disk media;
• and
• (ii) adjusting the level of current provided to the phase pairs of windings to compensate for deviation of the rotation rates of the rotor from the third predetermined rate.