Magnetic Absolute Encoder

• US 20080157705A1
• Filed: 12/07/2007
• Published: 07/03/2008
• Est. Priority Date: 12/28/2006
• Status: Active Grant

• Current Assignee: Harmonic Drive Systems Inc.
• Original Assignee: Harmonic Drive Systems Inc.
• Inventors: Mitamura, Muneo, Abe, Toshiyuki, Sasaki, Kozo, Maruyama, Toshiki
• Granted Patent: US 7,471,080 B2
• Time in Patent Office: Days
• US Class Current: 318/564
• CPC Class Codes: G01D 5/24428 Error prevention
• CPC Class Codes: G01D 5/24447 by energy backup
• CPC Class Codes: G01D 5/24461 by redundancy or plausibility

Abstract

In the magnetic absolute encoder, an ordinary operating circuit and an ordinary/backup operating circuit are actuated during ordinary operation in which power is supplied from the ordinary operating power supply; the single-rotation absolute value (1) and single-rotation absolute value (2) detected by these circuits are compared by the abnormality diagnosis circuit, and the presence or absence of an abnormality is automatically judged During backup in which the ordinary operating power supply is interrupted, only the low-power-consumption ordinary/backup operating circuit is actuated, and the multiple-rotation value (2) is detected At the point in time at which the system is returned to ordinary operation, the multiple-rotation value setting circuit sets the multiple-rotation value (2) as the multiple-rotation value (1) of the ordinary operating circuit. As a result, the calculation operation of the multiple-rotation value (1) can be restarted.

Claims

1. A magnetic absolute encoder comprising:

a magnetic sensor which outputs at least a pair of sine wave signals differing in phase by 90 degrees in association with the rotation of a multipolar-magnetized rotor;

main calculation means which detects the output of the magnetic sensor at a first detection period, and which calculates a single-rotation absolute value (1) that expresses the absolute position within one rotation of the rotor, and a multiple-rotation value (1) that expresses the number of rotations of the rotor from a preset origin;

backup calculation means which detects the output of the magnetic sensor at a second detection period that is longer than the first detection period, and which calculates a single-rotation absolute value (2) that expresses the absolute position within one rotation of the rotor, and a multiple-rotation value (2) that expresses the number of rotations of the rotor from the origin;

power supply control means which controls to drive the main calculation means and the backup calculation means using power supplied from a main power supply, and which controls to drive only the backup calculation means using power supplied from a backup power supply in cases where the main power supply is interrupted; and

an abnormality diagnosis means which compares the single-rotation absolute value (1) and single-rotation absolute value (2) respectively calculated by the main calculation means and the backup calculation means actuated by power from the main power supply, and which judges that an abnormality has occurred in cases where a state in which the difference between these values is equal to or greater than a predetermined difference continues for a specified number of rotations.

2. The magnetic absolute encoder according to claim 1, wherein the abnormality diagnosis means compares the multiple-rotation value (1) and the multiple-rotation value (2) respectively calculated by the main calculation means and the backup calculation means actuated by power from the main power supply, and which judges that an abnormality has occurred in cases where a state in which the difference between these values is equal to or greater than a predetermined difference continues for a specified number of rotations.

3. The magnetic absolute encoder according to claim 1, wherein the magnetic sensor comprises a first magnetic sensor that outputs a pair of sine wave signals differing in phase by 90 degrees in association with the rotation of the rotor, and a second magnetic sensor that outputs a pair of sine wave signals differing in phase by 90 degrees in association with the rotation of the rotor;

the main calculation means detects the output of the first magnetic sensor at the first detection period, and calculates the single-rotation absolute value (1) and the multiple-rotation value (1), and

the backup calculation means detects the output of the second magnetic sensor at the second detection period, and calculates the single-rotation absolute value (2) and the multiple-rotation value (2).

4. The magnetic absolute encoder according to claim 3, wherein

the main calculation means detects the output of the second magnetic sensor at the first detection period, and calculates a single-rotation absolute value (3) that expresses the absolute position within one rotation of the rotor, and

the abnormality diagnosis means compares the single-rotation absolute value (1) and the single-rotation absolute value (3) respectively calculated on the basis of the outputs of the first magnetic sensor and second magnetic sensor, and judges that an abnormality has occurred in cases where a state in which the difference between these values is equal to or greater than a predetermined difference continues for a specified number of rotations.

5. The magnetic absolute encoder according to claim 3, wherein

the magnetic sensor comprises a third magnetic sensor which outputs a pair of sine wave signals differing in phase by 90 degrees in association with the rotation of the rotor,

the main calculation means detects the output of the third magnetic sensor at the first detection period, and calculates a single-rotation absolute value (3) that expresses the absolute position within one rotation of the rotor, and

the abnormality diagnosis means compares the single-rotation absolute value (1) and the single-rotation absolute value (3) respectively calculated on the basis of the outputs of the first magnetic sensor and the third magnetic sensor, and judges that an abnormality has occurred in cases where a state in which the difference between these values is equal to or greater than a predetermined difference continues for a specified number of rotations.

6. The magnetic absolute encoder according to claim 1, wherein

the backup calculation means calculates only the multiple-rotation value (2) and stores this value in memory while actuated by power supplied from the backup power supply.

7. The magnetic absolute encoder according to claim 1, further comprising multiple-rotation value setting means which, at the point in time at which the supply of power from the main power supply is restarted and the main calculation means returns to an operating state, sets the multiple-rotation value (2) calculated by the backup calculation means as the multiple-rotation value (1) obtained by the main calculation means at this point in time.

8. The magnetic absolute encoder according to claim 1, further comprising warning means which outputs a warning in cases where the abnormality diagnosis means has judged that an abnormality has occurred.

9. The magnetic absolute encoder according to claim 2, wherein

the backup calculation means calculates only the multiple-rotation value (2) and stores this value in memory while actuated by power supplied from the backup power supply.

10. The magnetic absolute encoder according to claim 3, wherein

the backup calculation means calculates only the multiple-rotation value (2) and stores this value in memory while actuated by power supplied from the backup power supply.

11. The magnetic absolute encoder according to claim 4, wherein

the backup calculation means calculates only the multiple-rotation value (2) and stores this value in memory while actuated by power supplied from the backup power supply.

12. The magnetic absolute encoder according to claim 5, wherein

the backup calculation means calculates only the multiple-rotation value (2) and stores this value in memory while actuated by power supplied from the backup power supply.

13. The magnetic absolute encoder according to claim 2, further comprising multiple-rotation value setting means which, at the point in time at which the supply of power from the main power supply is restarted and the main calculation means returns to an operating state, sets the multiple-rotation value (2) calculated by the backup calculation means as the multiple-rotation value (1) obtained by the main calculation means at this point in time.

14. The magnetic absolute encoder according to claim 3, further comprising multiple-rotation value setting means which, at the point in time at which the supply of power from the main power supply is restarted and the main calculation means returns to an operating state, sets the multiple-rotation value (2) calculated by the backup calculation means as the multiple-rotation value (1) obtained by the main calculation means at this point in time.

15. The magnetic absolute encoder according to claim 4, further comprising multiple-rotation value setting means which, at the point in time at which the supply of power from the main power supply is restarted and the main calculation means returns to an operating state, sets the multiple-rotation value (2) calculated by the backup calculation means as the multiple-rotation value (1) obtained by the main calculation means at this point in time.

16. The magnetic absolute encoder according to claim 5, further comprising multiple-rotation value setting means which, at the point in time at which the supply of power from the main power supply is restarted and the main calculation means returns to an operating state, sets the multiple-rotation value (2) calculated by the backup calculation means as the multiple-rotation value (1) obtained by the main calculation means at this point in time.

17. The magnetic absolute encoder according to claim 2, further comprising warning means which outputs a warning in cases where the abnormality diagnosis means has judged that an abnormality has occurred.

18. The magnetic absolute encoder according to claim 3, further comprising warning means which outputs a warning in cases where the abnormality diagnosis means has judged that an abnormality has occurred.

19. The magnetic absolute encoder according to claim 4, further comprising warning means which outputs a warning in cases where the abnormality diagnosis means has judged that an abnormality has occurred.

20. The magnetic absolute encoder according to claim 5, further comprising warning means which outputs a warning in cases where the abnormality diagnosis means has judged that an abnormality has occurred.