# US 5,710,509 A · Phase difference detection device for an inductive position detector

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- Number: US 5,710,509 A
- Document ID: US5710509A
- Status: Granted
- Kind: A
- Application number: 08/550,358
- Filed: 1995-10-30
- Granted: 1998-01-20
- Earliest claimed: 1995-10-30
- Assignees: Atsutoshi Goto
- Inventors: Atsutoshi Goto; Yasuhiro Yuasa; Shuiti Tanaka; Nobuyuki Akatsu; Kazuya Sakamoto; Hiroshi Sakamoto; Akio Yamamoto
- Web page: https://patentgrep.com/patent/US5710509A

## CPC

- G01D 5/2073: {by movement of a single coil with respect to two or more coils}
- H03M 1/645: {for position encoding, e.g. using resolvers or synchros (H03M1/485 takes precedence)}
- G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)

## Abstract

Two A.C. output signals amplitude-modulated in accordance with two function values (sine and cosine) differing from each other in correspondence to a position-to-be-detected are received from a position sensor such as a resolver. By performing an addition or subtraction between a signal derived by shifting the electric phase of one of the received A.C. output signals by a predetermined angle, and the other received signal, two electric A.C. signals (sin(.omega.t .+-.d.+-..theta.), sin(.omega.t.+-.d-.theta.)) are electrically synthesized which have electric phase angles (.theta.) corresponding to the position-to-be-detected and are phase-shifted in opposite directions. ".+-.d" here represents phase variation error caused by factors, other than the position-to-be-detected, such as temperature change. In the synthesized two signals, the phase variation errors (.+-.d) appear in the same direction, while the phase differences (.theta.) corresponding to the position are shifted in opposite, positive and negative, directions. Thus, by measuring the respective phase shift amounts (.+-.d.+-..theta., .+-.d-.theta.) and performing appropriate operation, it is allowed to cancel out or extract the error (.+-.d) so that an accurate phase difference (.theta.) can be detected.

## Claims

### Claim 1

A phase difference detection device for an inductive position detector, said position detector being excited by a predetermined reference signal to generate first and second A.C. output signals, said first A.C. output signal having been amplitude-modulated using, as an amplitude coefficient, a first function value corresponding to a position-to-be-detected, and said second A.C. output signal having been amplitude-modulated using, as an amplitude coefficient, a second function value corresponding to the position-to-be-detected, said phase difference detection device comprising:
a phase shift circuit operatively coupled to said position detector to shift an electric phase of said first A.C. output signal by a predetermined angle;
an addition circuit operatively coupled to said phase shift circuit and to said position detector to perform an addition operation between an output signal of said phase shift circuit and said second A.C. output signal so as to synthesize a first data signal having an electric phase angle shifted in one of positive and negative directions in correspondence to the position-to-be-detected;
a subtraction circuit operatively coupled to said phase shift circuit and to said position detector to perform a subtraction operation between the output signal of said phase shift circuit and said received second A.C. output signal so as to synthesize a second data signal having an electric phase angle shifted in other of the positive and negative directions in correspondence to the position-to-be-detected;
a first operation circuit operatively coupled to said addition circuit to measure an electric phase difference between said predetermined reference signal and said first data signal to obtain first phase data;
a second operation circuit operatively coupled to said subtraction circuit to measure an electric phase difference between said predetermined reference signal and said second data signal to obtain second phase data; and
a third operation circuit operatively coupled to said first and second operation circuits to calculate position detection data corresponding to the position-to-be-detected on the basis of said first and second phase data.

### Claim 2 (depends on 1)

A phase difference detection device as defined in claim 1 wherein said third operation circuit is further adapted to obtain error data by calculating a difference between respective absolute values of said first and second phase data, and to obtain said position detection data by performing an operation to remove the error data from one of said first and second phase data.

### Claim 3 (depends on 1)

A phase difference detection device as defined in claim 1, further comprising:
a fourth operation circuit operatively coupled to said first and second operation circuits to detect a coincidence in zero cross between said first and second data signals;
a holding circuit operatively coupled to said fourth operation circuit to, in response to detection of the coincidence in zero cross between said first and second data signals, hold error data based on an electric phase difference of at least one of said first and second data signals from said predetermined reference signal;
wherein, said third operation circuit is further adapted to, at least when said position-to-be-detected is moving, modify said position detection data based on the electric phase difference of said at least one of said first and second data signals by use of the error data.

### Claim 4 (depends on 1)

A phase difference detection device as defined in claim 1 wherein said first and second function values are in a respective sine and cosine relation.

### Claim 5 (depends on 1)

A phase difference detection device as defined in claim 1 wherein said third operation circuit is further adapted to add said first and second phase data.

### Claim 6 (depends on 1)

A phase difference detection device as defined in claim 1 wherein said third operation circuit is further adapted to obtain error data by calculating a difference between respective absolute values of said first and second phase data, and outputs said error data as indicative of a temperature change of said device.

### Claim 7

A method of detecting a position by use of an inductive position detector, said position detector being excited by a predetermined reference signal to generate a first output signal having been amplitude-modulated using, as an amplitude coefficient, a first function value corresponding to a position-to- be-detected and generate a second output signal having been amplitude-modulated using, as an amplitude coefficient, a second function value corresponding to the position-to-be-detected, said method comprising the steps of:
receiving said first and second output signals from said position detector;
forming first and second data signals by combining said received first and second output signals, said first data signal having an electric phase angle shifted in a positive direction in relation to the position-to-be-detected, said second data signal having an electric phase angle shifted in a negative direction in relation to the position-to-be-detected;
measuring an electric phase difference between said predetermined reference signal and said first data signal to obtain first phase data;
measuring an electric phase difference between said predetermined reference signal and said second data signal to obtain second phase data; and
calculating position detection data corresponding to the position-to-be-detected on the basis of said first and second phase data.

### Claim 8 (depends on 7)

A method of detecting a position as defined in claim 7 further comprising the steps of:
detecting a coincidence in zero cross between said first and second data signals;
holding, as error data, data based on said phase data in response to a coincidence in zero cross between said first and second data signals detected in said detecting step; and
obtaining position detection data corresponding to the position-to-be-detected, by modifying said phase data by use of the error data held in said holding step, at least when the position-to-be-detected is moving.