Device for detecting multi-turn absolute rotation angle and method for detecting the same

• US 9,513,142 B2
• Filed: 01/06/2012
• Issued: 12/06/2016
• Est. Priority Date: 01/07/2011
• Status: Active Grant

• Current Assignee: Oriental Motor Company Limited
• Original Assignee: Oriental Motor Company Limited
• Inventors: Houda, Akihiko
• Primary Examiner(s): Tsai, Carol S
• Application Number:
  US13/978,375
• Publication Number:
  US 20130289936A1
• Time in Patent Office: 1,796 Days
• Field of Search: 702/151, 477/107, 477/102, 477/3, 477/20, 477/15, 477/54, 738/624.6, 738/623.26, 708/201, 324/207.25, 324/207.2
• US Class Current: 1/1
• CPC Class Codes: G01B 5/24 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 2205/26 Details of encoders or position sensors specially adapted to detect rotation beyond a full turn of 360°, e.g. multi-rotation
• CPC Class Codes: G01D 2205/28 The target being driven in rotation by additional gears
• CPC Class Codes: G01D 5/20 by varying inductance, e.g. by a movable armature
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence

Abstract

There is provided a method for calculating with high accuracy a multi-turn absolute rotation angle of a motor rotating shaft coupled to a motor output shaft. In a rotation angle detection device according to this invention, a rotation angle θ_n of an n-th rotating shaft satisfies the relationship with a rotation angle θ₁ of the motor rotating shaft: θ_n=(−(m±1)/m)ⁿ⁻¹×θ₁. The rotation angle detection device as an embodiment of a mechanism satisfying the relationship includes a gear mechanism in which a gear having (m±1) teeth meshes with a gear having m teeth between each adjacent two of first to n-th rotating shafts. A multi-turn rotation angle of the first rotating shaft is expanded to a detected value p₁ of the first rotating shaft which is a rotation angle of the first rotating shaft and R₀×m⁰+R₁×m¹+ . . . R_n−2×mⁿ⁻² corresponding to the number of revolutions of the first rotating shaft, coefficients R₀ to R_n−2 are obtained on the basis of detected values from angle detectors of the respective shafts, and the multi-turn rotation angle of the first rotating shaft is calculated. Detection errors generated in the angle detectors of the second and subsequent rotating shafts can be effectively reduced, and a high-accuracy multi-turn rotation angle can be calculated.

Claims

1. A rotation angle detection device for detecting an absolute rotation angle of a first rotating shaft of first to nmax-th rotating shafts, comprising:

a transmission mechanism adapted to transmit revolution from the first rotating shaft of the first to nmax-th rotating shafts down to an nmax-th rotating shaft of the first to nmax-th rotating shafts; and

an angle detector adapted to detect respective rotation angles of the first rotating shaft to an n-th rotating shaft of the first to nmax-th rotating shafts;

wherein;

the first rotating shaft comprises a rotation angle θ

₁;

the n-th rotating shaft comprises a rotation angle θ

_n; and

the rotation angle θ

_n satisfies a relationship with the rotation angle θ

₁ as follows;

2. The rotation angle detection device according to claim 1, wherein:

a rotation angle calculated value θ

_c of the first rotating shaft is calculated as follows;

θ

_c=mod((k₁×

p₁+k₂×

p₂+ . . . +k_n×

p_n),u)×

m<sup>n−

1</sup>

where (a) p₁, P₂, . . . , p_n are angle detected values of the first rotating shaft to the n-th rotating shaft which are detected by the angle detector, (b) u is an angle detected quantity for one cycle of the first to nmax-th rotating shafts, (c) mod(x,a) is a modulo operation which obtains a remainder left over when x is divided by a, and (d) coefficients k₁, . . . , k_n are a positive integer or a negative integer including a zero and the coefficients k₁, . . . , k_n correspond to a coefficient of an (n−

1)-th degree term in x, respectively, when an expression (x+1)<sup>n−

1</sup> is expanded.

3. The rotation angle detection device according to claim 1, wherein:

the transmission mechanism transmits the revolution with the change ratio of (m±

1)/m.

4. A rotation angle detection device for detecting a multi-turn absolute rotation angle of a first rotating shaft coupled to a motor, comprising:

a gear mechanism comprising multiple gears, the multiple gears being fixed to rotating shafts from the first rotating shaft to an n-th rotating shaft; and

an angle detector adapted to detect respective rotation angles of the first rotating shaft to the n-th rotating shaft;

wherein;

the multiple gears continuously mesh with each other; and

the gear mechanism comprises multiple pairs of gears, each pair of the multiple pairs of gears being meshed together such that a ratio of change in rotational speed is (m±

1)/m between two continuous rotating shafts.

5. A method for calculating a multi-turn absolute rotation angle of a first rotating shaft in a multi-turn absolute rotation angle detection device, the multi-turn absolute rotation angle detection device including (i) a transmission mechanism adapted to transmit revolution from the first rotating shaft of first to nmax-th rotating shafts down to the nmax-th rotating shaft and (ii) an angle detector adapted to detect angle detected values p₁ to p_nmax within one revolution of the first rotating shaft to the nmax-th rotating shaft, wherein a rotation angle θ

_n of an n-th rotating shaft satisfies a relationship with a rotation angle θ

₁ of the first rotating shaft as follows;

6. The method according to claim 5, wherein:

estimating the coefficient R<sub>n−

2</sub> comprises;

obtaining a periodic signal S(m<sup>n−

1</sup>) using detected values of n shafts by a periodic signal formula as follows;

S<sub>(mn−

1)</sub>=mod((k₁×

p₁+k₂×

p₂′

+k₃×

p₃′

+ . . . +k<sub>n−

1</sub>×

p<sub>n−

1</sub>′

+k_n×

p_n)×

J<sup>n−

1</sup>,u),

where (a) k₁, k₂, . . . k_n are coefficients of a (n−

1)-th degree term in x of an expansion k₁×

x⁰+k₂×

x¹+k₃×

x²+ . . . +k_nx<sup>n−

1</sup> of (x+1)<sup>n−

1</sup>, (b) mod(x,a) is a modulo operation which obtains a remainder left over when x is divided by a, and (c) J is a sign-adjusting term which is 1 if a change ratio between each adjacent two of the first to nmax-th rotating shafts is −

(m−

1)/m and is −

1 when the change ratio is −

(m+1)/m;

multiplying the periodic signal S(m<sup>n−

1</sup>) of the n-th rotating shaft by m<sup>n−

1</sup> to obtain a rotation angle calculated value θ

₁(m<sup>n−

1</sup>); and

determining the coefficient R<sub>n−

2</sub> such that a result of calculating the rotation angle calculation formula that obtains the rotation angle calculated value θ

₁(m<sup>n−

1</sup>)′

of the n-th rotating shaft approximates the rotation angle calculated value θ

¹(m<sup>n−

1</sup>);

wherein;

the rotation angle calculated value θ

₁(m<sup>n−

1</sup>)′

of the n-th rotating shaft is obtained by substituting the coefficient R<sub>n−

2</sub> that is determined into the rotation angle calculation formula; and

an angle corrected value p_n′

is obtained by substituting the rotation angle calculated value θ

₁(m<sup>n−

1</sup>)′

obtained into an angle corrected value formula as follows;

7. The method according to claim 6, wherein:

estimating the coefficient R<sub>n−

2</sub> comprises computing the coefficient R<sub>n−

2</sub> according to an operation INT(x) as follows;

8. The method according to claim 6, wherein:

the multi-turn absolute rotation angle detection device further includes (a) multiple other transmission mechanisms which are provided in parallel with the transmission mechanism and (b) multiple other angle detectors; and

the method further comprises calculating multiple periodic signals based on multiple angle detected values detected by the angle detector and the multiple other angle detectors.

9. The method according to claim 8, wherein:

periods of the multiple periodic signals are relatively prime to each other.

10. The method according to claim 5, wherein:

estimating the coefficient R<sub>n−

2</sub> comprises determining an integer which most closely approximates a result of calculating an integer formula as follows;

11. The method according to claim 5, wherein:

the multi-turn absolute rotation angle detection device further includes (a) multiple other transmission mechanisms which are provided in parallel with the transmission mechanism and (b) multiple other angle detectors; and

the method further comprises calculating the multi-turn absolute rotation angle based on multiple angle detected values detected by the angle detector and the multiple other angle detectors.

12. A device for calculating a multi-turn absolute rotation angle, comprising:

a transmission mechanism adapted to transmit revolution from a first rotating shaft of first to nmax-th rotating shafts down to an nmax-th rotating shaft of the first to nmax-th rotating shafts;

an angle detector adapted to detect an angle detected value p₁ to an angle detected value p_nmax within one revolution of the first rotating shaft to the nmax-th rotating shaft; and

a computing unit adapted to calculate a multi-turn absolute rotation angle calculated value θ

₁(m<sup>nmax−

1</sup>)′

of the first rotating shaft based on the angle detected value p₁ to the angle detected value p_nmax;

wherein;

the first rotating shaft comprises a rotation angle θ

₁;

an n-th rotating shaft of the first to nmax-th rotating shafts comprises a rotation angle θ

_n; and

the rotation angle θ

_n satisfies a relationship with the rotation angle θ

₁ as follows;

13. The device according to claim 12, wherein the computing unit contains circuitry configured to:

obtain a periodic signal S(m<sup>n−

1</sup>) obtained from detected values of n shafts by a period signal formula as follows;

S<sub>(mn−

1)</sub>=mod((k₁×

p₁+k₂×

p₂′

+k₃×

p₃′

+ . . . +k<sub>n−

1</sub>×

p<sub>n−

1</sub>′

+k_n×

p_n)×

J<sup>n−

1</sup>,u)

where (a) k₁, k₂, . . . k_n are coefficients of a (n−

1)-th degree term in x of an expansion k₁×

x⁰+k₂×

x¹+k₃×

x²+ . . . +k_nx<sup>n−

1</sup> of (x+1)<sup>n−

1</sup>, (b) mod(x,a) is a modulo operation which obtains a remainder left over when x is divided by a, and (c) J is a sign-adjusting term which is 1 if a change ratio between each adjacent two of the first to nmax-th rotating shafts is −

(m−

1)/m and is −

1 when the change ratio is −

(m+1)/m;

obtain a rotation angle calculated value θ

₁(m<sup>n−

1</sup>) by multiplying the periodic signal S(m<sup>n−

1</sup>) of the n-th rotating shaft by m<sup>n−

1</sup>;

determine a coefficient R<sub>n−

2</sub> such that a result of calculating the rotation angle calculation formula that obtains the rotation angle calculated value θ

₁(m<sub>n−

1</sub>)′

of the n-th rotating shaft approximates the rotation angle calculated value θ

₁(m<sup>n−

1</sup>);

substitute the coefficient R<sub>n−

2</sub> determined into the rotation angle calculation formula to obtain the rotation angle calculated value θ

₁(m<sup>n−

1</sup>)′

of the n-th rotating shaft; and

obtain an angle corrected value pⁿ′

by substituting the rotation angle calculated value θ

₁(m<sup>n−

1</sup>)′

obtained into an angle corrected value formula as follows;

14. The device according to claim 13, wherein:

the coefficient R<sub>n−

2</sub> is determined according to an operation INT(x) as follows;

15. The device according to claim 13, further comprising:

multiple other transmission mechanisms which are provided in parallel with the transmission mechanism; and

multiple other angle detectors;

wherein;

multiple periodic signals are calculated based on multiple angle detected values detected by the angle detector and the multiple other angle detectors.

16. The device according to claim 15, wherein:

periods of the multiple periodic signals are relatively prime to each other.

17. The device according to claim 12, wherein:

the coefficient R<sub>n−

2</sub> is obtained by determining an integer which most closely approximates a result of calculating an integer formula as follows;

18. The device according to claim 12, further comprising:

multiple other transmission mechanisms which are provided in parallel with the transmission mechanism; and

multiple other angle detectors;

wherein;

the multi-turn absolute rotation angle is calculated based on multiple angle detected values detected by the angle detector and the multiple other angle detectors.

19. The device according to claim 18, wherein:

the first rotating shaft of the transmission mechanism and first rotating shafts of the multiple other transmission mechanisms are a same rotating shaft.

20. A method for calculating a multi-turn absolute rotation angle calculated value θ

₁(m<sup>nmax−

1</sup>)′

of a first rotating shaft in a multi-turn absolute rotation angle detection device, the multi-turn absolute rotation angle detection device including (i) a transmission mechanism adapted to transmit revolution from the first rotating shaft of first to nmax-th rotating shafts down to the nmax-th rotating shaft of the first to nmax-th rotating shafts and (ii) an angle detector adapted to detect an angle detected value p₁ to an angle detected value p_nmax within one revolution of the first rotating shaft to the nmax-th rotating shaft, wherein a rotation angle θ

_n of an n-th rotating shaft of the first to nmax-th rotating shafts satisfies a relationship with a rotation angle θ

₁ of the first rotating shaft as follows;

21. The method according to claim 20, wherein:

determining the coefficient R<sub>n−

2</sub> comprises determining an integer which most closely approximates a result of calculating an operation as follows;

22. The method according to claim 20, wherein:

the multi-turn absolute rotation angle detection device further includes (a) multiple other transmission mechanisms which are provided in parallel with the transmission mechanism and (b) multiple other angle detectors; and

the method further comprises calculating a multi-turn absolute rotation angle based on multiple angle detected values detected by the angle detector and the multiple other angle detectors.

23. The method according to claim 22, wherein:

the first rotating shaft of the transmission mechanism and first rotating shafts of the multiple other transmission mechanisms are a same rotating shaft.