Device for controlling an electronically commutated motor

• US 20030057903A1
• Filed: 09/26/2002
• Published: 03/27/2003
• Est. Priority Date: 09/26/2001
• Status: Active Grant

• Current Assignee: SNR Roulements
• Original Assignee: SNR Roulements
• Inventors: Desbiolles, Pascal, Nicot, Christophe, Friz, Achim
• Granted Patent: US 6,683,427 B2
• Time in Patent Office: Days
• US Class Current: 318/254
• CPC Class Codes: B62D 15/02 Steering position indicators ; Steering position determination; Steering aids
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position

Abstract

The invention relates to a device for controlling an electronically commutated motor (1) comprising P phases and N pairs of poles (5), said device comprising:

a circular multipole encoder (4) comprising a main multipole track (4a) and a multipole commutation track (4b) comprising 2*P*N singularities (4b1-4b6) equidistributed angularly;

a fixed sensor (6) capable of delivering square digital signals A, B in quadrature and a digital signal C in the form of 2*P*N pulses (TP1-TP6) per revolution of the encoder;

a commutation circuit (7) having 2*P*N switches (T1-T6);

a control circuit (8) for the commutation circuit (7) which:

from the signal c supplies commutation signals for the switches (T1-T6); and

from the signals A, B and according to a first current set point (I*) defines a second current set point (Iref) which controls the current (Im) supplying the phase windings of the motor (1).

Claims

1. A device for controlling an electronically commutated motor (1) comprising P phases and N pairs of poles, said device comprising:

a circular multipole encoder (4) intended to perform, together with the rotor (2) of the motor (1), a plurality of revolutions around its axis of rotation, said encoder (4) comprising a main multipole track (4a) and a multipole commutation track (4b) comprising 2*P*N singularities (4b1-4b6) equidistributed angularly, the main (4a) and commutation (4b) tracks being concentric on the encoder (4);

a fixed sensor (6) disposed opposite and at air gap distance from the encoder (4), comprising at least three sensing elements, at least two of which are positioned opposite the main track (4a) so as to deliver two periodic electrical signals S1, S2 in quadrature, and at least one of which is positioned opposite the commutation track (4b) so as to deliver an electrical signal S3, the sensor (6) comprising an electronic circuit capable, from the signals S1, S2 and S3, of delivering square digital signals A, B in quadrature and a digital signal C in the form of 2*P*N pulses (TP1-TP6) per revolution of the encoder;

a circuit for commutating (7) the currents in the phase windings of the motor (1) having 2*P*N switches (T1-T6);

a control circuit (8) for the commutation circuit (7) which;

from the signal C supplies commutation signals for the switches (T1-T6); and

from the signals A, B and according to a first current set point (I*) defines a second current set point (Iref) which controls the current (Im) supplying the phase windings of the motor (1).

2. A control device according to claim 1, characterised in that the control circuit (8) comprises a regulation loop controlled by the second current set point (Iref) originating from an electronic circuit (9), said control circuit (8) being capable of modulating the commutation signals in terms of width and duration by means of an AND logic function (13).

3. A control device according to claim 1 or 2, characterised in that the control circuit (8) comprises a microprocessor (12) integrating at least one commutation logic for the commutation circuit (7).

4. A control device according to any one of claims 1 to 3, characterised in that the encoder (4) is formed from a multipole magnetic ring on which there are magnetised a plurality of pairs of equidistributed North and South poles (5) with a constant angular width so as to form the main track (4a) and commutation track (4b), a magnetic singularity (4b1-4b6) being formed from two pairs of poles which are different from the others.

5. A control device according to claim 4, characterised in that the sensing elements are chosen from amongst the group comprising Hall effect sensors, magnetoresistors and giant magnetoresistors.

6. A control device according to any one of claims 1 to 3, characterised in that the encoder (4) is formed from a target on which the reference (4a) and commutation (4b) tracks have been etched so as to form an optical pattern analogous to a multipole magnetic pattern, the sensing elements then being formed from optical detectors.

7. A control device according to claim 5 or 6, characterised in that the sensor (6) comprises a plurality of aligned sensing elements which are disposed opposite and at air gap distance from the main track (4a).

8. A control device according to any one of claims 1 to 7, characterised in that the sensor (6) comprises an interpolator increasing the resolution of the output signals.

9. A control device according to any one of claims 1 to 8, characterised in that the sensor (6) is integrated in an ASIC type circuit (19).

10. A control device according to any one of claims 1 to 9, characterised in that the encoder (4) is associated with the rotating ring (14) of an anti-friction bearing (15) allowing the rotation of the rotor (2) or that of a member rotated by the rotor (2).

11. A control device according to claim 10, characterised in that the sensor (6) is associated with the fixed ring (16) of the anti-friction bearing (15).

12. A control device according to claim 10, characterised in that the sensor (6) is separate from the fixed ring (16) of the anti-friction bearing (15).

13. A control device according to any one of claims 1 to 12, characterised in that the control circuit (8) comprises means of initialising the position of the rotor (2) allowing the commutation signals to be adapted to the direction of rotation desired for the rotor (2).

14. A method for using a control device according to any one of claims 1 to 13, in which the control signals make it possible, according to predetermined commutation logic, to actuate the switches (T1-T6) in twos in turn, the transition from the actuation of two switches (T1-T6) to the following two taking place each time an electrical pulse (TP1-TP6) of the signal C is detected.

15. A method according to claim 14, characterised in that it comprises a preliminary step of indexing the encoder (4) in which the phase displacement is stored in an EEPROM or Flash type memory of the control circuit (8).

16. A method according to claim 14 or 15 when it depends on claim 13, characterised in that, upon powering up of the device, a procedure of initialising the position of the rotor (2) is performed, said procedure comprising the steps of:

a) selecting commutation logic making the stator field rotate in one direction;

b) operating the control circuit (8) according to a first state of this logic in order to actuate two switches (T1-T6) for a given time interval in order to supply two phases of the motor (1) with a current (Iinit) sufficient to rotate the rotor (2);

c) detecting, by analysis of the signals A, B, the direction of rotation of the rotor (2) under the action of this current (Iinit);

d) if the rotor (2) does not rotate, making a transition to the second state of the commutation logic and then reiterate the preceding steps;

e) if the rotor (2) rotates in the same direction as the stator field, changing the commutation logic and then reiterate the preceding steps;

f) when the rotor (2) rotates in the opposite direction to the stator field, reiterating steps b) and c) with the successive states of the commutation logic until there is a reversal of the direction of rotation of the rotor (2);

g) upon the reversal of the direction of rotation of the rotor (2), making a transition to the state n−

2 of the commutation logic in order to detect a new reversal of the direction of rotation of the rotor (2);

h) detecting the position of the pulse (TP1-TP6) of the signal C recorded during step g) so as to obtain the relative position of the rotor (2) with respect to this pulse;

said method making it possible, according to the direction of rotation desired for the rotor (2), to select the corresponding commutation logic.

17. An anti-friction bearing (15) intended to provide the rotation of the rotor (2) of an electronically commutated motor (1) comprising P phases and N pairs of poles (5) or that of a member rotated by said rotor (2), said anti-friction bearing (15) comprising a fixed ring (16), a rotating ring (14) and rolling bodies disposed between said rings (16, 14), in which:

there is associated with the rotating ring (14) a circular multipole encoder (4) comprising a main multipole track (4a) and a multipole commutation track (4b) comprising 2*P*N singularities (4b1-4b6) equidistributed angularly, the main (4a) and commutation (4b) tracks being concentric on the encoder (4); and

there is associated with the fixed race (16) a fixed sensor (6) disposed opposite and at air gap distance from the encoder (4), comprising at least three sensing elements, at least two of which are positioned opposite the main track (4a) so as to deliver two square digital signals A, B in quadrature, and at least one of which is positioned opposite the commutation track (4b) so as to deliver a signal C in the torm of 2*P*N pulses (TP1-TP6) per revolution of the encoder (4), the signal C being intended to supply commutation signals to the motor (1) and the signals A, B being intended, according to a current set point (I*), to control the current (Im) supplying the motor (1).