US 7,471,080 B2Granted

Magnetic absolute encoder

AssigneeHarmonic Drive Systems Inc.

InventorsKozo Sasaki, Toshiki Maruyama, Toshiyuki Abe, Muneo Mitamura

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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.

Claims20

Dependent claims

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.

3 more elements

Dependencies are inferred from the claim text.