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Capacitive Encoder for Commutation and Rate Feedback

IP.com Disclosure Number: IPCOM000046277D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

Kilen, RS: AUTHOR

Abstract

Shown above are the printed circuit patterns for the stator and rotor in a capacitive encoder. Patterns 10-17 on the stator and 18 and 19 on the rotor perform a commutation function. Patterns 20 and 21 on the stator and 22 and 23 on the rotor perform a rate feedback function. Pattern 24 on the stator is shared by both the commutation and rate feedback functions.

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Capacitive Encoder for Commutation and Rate Feedback

Shown above are the printed circuit patterns for the stator and rotor in a capacitive encoder. Patterns 10-17 on the stator and 18 and 19 on the rotor perform a commutation function. Patterns 20 and 21 on the stator and 22 and 23 on the rotor perform a rate feedback function. Pattern 24 on the stator is shared by both the commutation and rate feedback functions.

In practice, the stator and rotor are mounted face-to-face on a common axis, with a small gap (typically about 0.25 mm) between them. The rotor is mounted to the motor shaft and the stator is mounted in a fixed position usually attached to the motor housing.

For the commutation function, Clock 1 is applied to pattern 10, while clock 2 is applied to pattern 24. The commutation signals are taken from patterns 12, 14 and 16. To suppress the carrier on the commutation channels A, B and C (patterns 12, 14 and 16), patterns 11 and 17 are driven by Clock 2 and Clock 1, respectively. Clocks 1 and 2 are 180OE out of phase. In addition, patterns 13 and 15 are grounded.

For the rate feedback function, Clock 1 is applied to pattern 21, and Clock 2 is applied to pattern 24. Capacitive coupling through patterns 22 and 23 of the rotor results in the rate feedback signal on channel HF (pattern 20).

To provide independent optimization of the functions, patterns 19 and 22, which could have been shared on the rotor, are split as shown. This also gives better isolation bet...