Control of brushless D-C motors

• US 3,906,320 A
• Filed: 10/23/1973
• Issued: 09/16/1975
• Est. Priority Date: 10/27/1972
• Status: Expired due to Term

• Current Assignee: Papst Licensing GmbH & Company Kg
• Original Assignee: Benno Doemen
• Inventors: Doemen, Benno
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Feldhaus, John J.
• Application Number:
  US05/408,781
• Time in Patent Office: 693 Days
• Field of Search: 318/341,254,331,138,328
• US Class Current: 318/400.04
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence

Abstract

To control the operation of brushless d-c motors, in which armature coils are pulse-energized, a signal representative of voltage induced in the armature coils is obtained, this signal is separated into its a-c and its d-c components and the a-c component is inverted to derive an inverted 180* out-of-phase signal. The timing of the energization of the motor windings is controlled, with respect to angular position of the rotor, by the inverted a-c signal component, and the extent, or pulse width, or pulse duration of the energization is controlled in dependence on the d-c component.

Claims

1. Method of controlling the operation of brushless d-c motors having a rotor (26), winding means (11, 12) being pulse-energized to generate torque pulses, and means (45, 46) to store magnetic energy during generation of torque and to release the stored energy during gaps between torque pulses to provide substantially uniform torque to the rotor during rotation thereof;

comprising the steps of deriving a signal (U70) representative of voltage induced in the motor winding means;

separating said signal into its a-c and its d-c components;

displacing the a-c component to derive a displaced signal (103) having absolute maxima and minima values which are displaced with respect to the absolute maxima and minima of said a-c component;

controlling the timing of energization of said motor winding means, with respect to angular rotor position, in dependence on said displaced a-c component; and

controlling the inteNsity of energization of said winding means in accordance with the d-c component.

2. Method according to claim 1, comprising the steps of generating a reference voltage signal;

comparing the d-c component with said reference voltage signal;

wherein the step of controlling the intensity of energization of said d-c motor means comprises applying a signal representative of the error between the reference signal and the d-c component to the winding means during a time controlled by said displaced a-c component.

3. Method according to claim 1, wherein the step of controlling the energization of said motor winding means comprises controlling the duration of ON-energization of said motor winding means and modifying said d-c component in accordance with a controllable signal.

4. Method according to claim 1, wherein the step of displacing the a-c component comprises inverting the a-c component to derive an inverted a-c component signal.

5. Brushless d-c motor and control circuit therefor, wherein the motor comprises a rotor (26);

winding means (11,

     12) being pulse-energized to generate torque pulses; and

means (45,

     46) to store magnetic energy during generation of torque and to release stored energy during gaps between torque pulses to provide a substantially uniform torque to the rotor during rotation thereof; and

wherein the control circuit for the motor comprises sensing means (68,

     69) connected to the winding means (11,

     12) sensing voltage (U70) induced in the winding means;

means (107) separating the a-c and d-c components of said induced voltage;

means (97'"'"''"'"', 98'"'"''"'"',

     117) displacing the a-c component to provide a displaced a-c signal having absolute maxima and minima which are displaced with respect to the maxima and minima of said induced voltage; and

means (84,

     87) connected to and controlled (94) by said displaced a-c component signal controlling the timing, with respect to instantaneous angular position of the rotor (26) of the energization pulses applied to said winding means, and further connected to and controlled (95) by said d-c component controlling the intensity of energization of the pulses.

6. Control circuit and motor according to claim 5 wherein the displacing means comprises an inverter circuit (117) to provide an inverted a-c component signal.

7. Control circuit and motor according to claim 5, wherein the controlling means (84, 87) comprises an operational amplifier (87);

means providing a d-c voltage of equal magnitude but opposite polarity to the d-c component;

first adding means adding said d-c voltage and said a-c component and connecting said first added voltage to the first input of said operational amplifier;

means providing a control voltage of polarity opposite to the polarity of the d-c component;

second adding means adding said control voltage and said d-c component and connecting said second added voltage to an input of said operational amplifier which is inverse with respect to said first input.

8. Control circuit and motor according to claim 7, further comprising an R/C circuit (90, 91) connected to operational amplifier to prevent rapid switching of the operational amplifier and provide for smooth turn-ON and turn-OFF of the pulses to the winding means of the motor.

9. Control circuit and motor according to claim 5, wherein the means separating a-c and d-c components comprises an R/C network (107) having at least one resistor (100, 105) and at least one capacitor (99, 106).

10. Control circuit and motor according to claim 9, wherein the R/C network comprises a pair of parallel R/C circuits, one of said circuits being a series combination of resistance and capacitance and the other circuit being a T-network.

11. Control circuit and motor according to claim 5, wherein the means (87) controlling the energization of the winding means controls pulse amplitude.

12. ContrOl circuit and motor according to claim 5, further comprising circuit means providing a command voltage, and means adding said command voltage to said d-c component, to shift the level thereof.

13. Control circuit and motor according to claim 12, wherein said circuit means comprises a constant current source (FIG. 8:

130).

14. Control circuit and motor according to claim 12, wherein said circuit means comprises a Zener diode circuit.

15. Control circuit and motor according to claim 5, wherein the winding means of the motor comprises two coils, each having a bifilar winding.

16. Control circuit and motor according to claim 15, wherein the sensing means comprises a multiphase half-wave rectifier, one each rectifier of a phase being connected to one of the conductors of the bifilar winding and sensing the voltage induced in the winding which does not have a current pulse flowing therethrough.

17. Control circuit and motor according to claim 5, wherein the means (84) controlling the energization of the pulse applied to the winding means controls the pulse width.

18. Control circuit and motor according to claim 5, further comprising circuit means providing a reference voltage, and means adding said reference voltage to said a-c component to shift the level thereof with respect to the induced voltage.

19. Control circuit and motor according to claim 18, wherein said circuit means comprises a Zener diode circuit.