MONITORING BI-DIRECTIONAL MOTOR DRIVE FAILURE IN ELECTRO-OPTICAL READER
First Claim
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1. An arrangement for detecting a malfunction of a bi-directional motor drive in a reader for electro-optically reading indicia, the arrangement comprising:
- a) a resonant motor having a rotor oscillatable about an axis;
b) a permanent magnet jointly oscillatable with the rotor;
c) a scanning element jointly oscillatable with the rotor, and operative for directing a light beam at the indicia to be electro-optically read;
d) a drive coil in operational proximity with the magnet, and operative for generating a drive signal to drive the rotor, the magnet and the scanning element in opposite directions about the axis over the indicia at a resonant frequency;
e) a feedback winding in operational proximity with the magnet, and operative for generating a feedback signal having a feedback frequency corresponding to the resonant frequency during oscillation of the magnet;
f) a zero crossing detector for detecting zero crossings of the feedback signal to generate a start of scan (SOS) signal having an SOS frequency; and
g) a control processor for monitoring the SOS frequency, and for sensing the malfunction when the SOS frequency is outside a predetermined range of SOS frequencies.
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Abstract
Malfunction of a bi-directional resonant motor drive in an electro-optical reader is detected without new hardware by monitoring the frequency of a start-of-scan signal, and by determining whether the monitored frequency lies within a predetermined frequency range.
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Citations
10 Claims
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1. An arrangement for detecting a malfunction of a bi-directional motor drive in a reader for electro-optically reading indicia, the arrangement comprising:
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a) a resonant motor having a rotor oscillatable about an axis;
b) a permanent magnet jointly oscillatable with the rotor;
c) a scanning element jointly oscillatable with the rotor, and operative for directing a light beam at the indicia to be electro-optically read;
d) a drive coil in operational proximity with the magnet, and operative for generating a drive signal to drive the rotor, the magnet and the scanning element in opposite directions about the axis over the indicia at a resonant frequency;
e) a feedback winding in operational proximity with the magnet, and operative for generating a feedback signal having a feedback frequency corresponding to the resonant frequency during oscillation of the magnet;
f) a zero crossing detector for detecting zero crossings of the feedback signal to generate a start of scan (SOS) signal having an SOS frequency; and
g) a control processor for monitoring the SOS frequency, and for sensing the malfunction when the SOS frequency is outside a predetermined range of SOS frequencies. - View Dependent Claims (2, 3, 4, 5)
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6. A method of detecting a malfunction of a bi-directional motor drive in a reader for electro-optically reading indicia, the method comprising the steps of:
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a) mounting a rotor of a resonant motor for oscillation about an axis;
b) mounting a permanent magnet for joint oscillation with the rotor;
c) mounting a scanning element for joint oscillation with the rotor;
d) directing a light beam at the indicia to be electro-optically read;
e) generating a drive signal to drive the rotor, the magnet and the scanning element in opposite directions about the axis over the indicia at a resonant frequency;
f) generating a feedback signal having a feedback frequency corresponding to the resonant frequency during oscillation of the magnet;
g) detecting zero crossings of the feedback signal to generate a start of scan (SOS) signal having an SOS frequency; and
h) monitoring the SOS frequency, and sensing the malfunction when the SOS frequency is outside a predetermined range of SOS frequencies. - View Dependent Claims (7, 8, 9, 10)
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Specification