Method and device for determining angular position

• US 7,873,493 B2
• Filed: 10/07/2008
• Issued: 01/18/2011
• Est. Priority Date: 10/11/2007
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Tenten, Wilfried
• Primary Examiner(s): Bui; Bryan
• Application Number:
  US12/287,302
• Publication Number:
  US 20090096445A1
• Time in Patent Office: 833 Days
• Field of Search: 702/151, 702/145, 324/207.12, 324/207.25, 318/479
• US Class Current: 702/151
• CPC Class Codes: G01B 21/22 for measuring angles or tapers; for testing the alignment of axes

Abstract

A method for determining angular position, which removes a systematic error in the angular position determination and requires a low calculating effort, by determining a first factor and a second factor as a function of an angular position, forming a first product from a first signal and the first factor, and a second product of the second signal and the second factor, forming a subtraction result by the subtraction of the second product from the first product, and comparing the subtraction result to a quantity.

Claims

1. A method for determining a resulting value for an angular position, the method comprising:

circuitry performing the following;

determining a first factor and a second factor as a function of an initial angular position value;

forming a first product from a first signal of a first sensor and the first factor and a second product from a second signal of a second sensor and the second factor;

forming a subtraction result by subtracting the second product from the first product;

comparing the subtraction result to a predetermined quantity;

determining an additional first factor and an additional second factor as a function of an additional angular position, the additional angular position selected based on the comparison;

forming an additional first product from the first signal and the additional first factor and an additional second product from the second signal and the additional second factor;

forming an additional subtraction result by subtracting the additional second product from the additional first product;

comparing the additional subtraction result to the predetermined quantity; and

determining a resulting value for a first angular position based on the comparison of the additional subtraction result to the predetermined quantity.

2. The method of claim 1, wherein the additional angular position is determined by successive approximation so that the difference between the additional subtraction result and the predetermined quantity for the additional angular position is less than the difference between the subtraction result and the predetermined quantity for the angular position, so as to determine a resulting value for the angular position at a point in time.

3. The method of claim 2, wherein the predetermined quantity is zero.

4. The method of claim 2, wherein the first signal is obtained by subtracting a value from a first sinusoidal measuring signal, and wherein the second signal is obtained by subtracting an additional value from a second sinusoidal measuring signal.

5. The method of claim 2, wherein the factors correspond to elements of a matrix for the transformation of coordinates of a vector in a coordinate system having oblique coordinates to coordinates of the vector in a coordinate system having orthogonal coordinates.

6. The method of claim 2, further comprising:

determining a following first factor and a following second factor as a function of an initial following angular position;

forming a following first product from a following first signal and the following first factor and a following second product from a following second signal and the following second factor;

forming a following subtraction result by subtracting the following second product from the following first product;

comparing the following subtraction result to the predetermined quantity; and

refining the initial following angular position based on the comparison of the following subtraction result to the quantity to obtain a refined following angular position.

7. The method of claim 6, further comprising:

determining another following first factor and another following second factor as a function of the refined following angular position;

forming another following first product from the following first signal and the another following first factor, and another following second product from the following second signal and the another following second factor;

forming another following subtraction result by subtracting the another following second product from the another following first product;

comparing the another following subtraction result to the predetermined quantity; and

determining a resulting value for the following angular position based on the comparison of the another following subtraction result to the predetermined quantity.

8. The method of claim 7, wherein:

the refined following angular position is determined by successive approximation so that the difference between the another following subtraction result and the predetermined quantity for the refined following angular position is less than the difference between the following subtraction result and the following quantity for the following angular position; and

the following angular position corresponds to a point in time following a first point in time to which the first angular position corresponds.

9. The method of claim 8, wherein an angular velocity is determined based on the resulting value for the first angular position and the resulting value for the following angular position and a difference between the first point in time and the following point in time.

10. The method of claim 8, wherein a difference between the resulting value for the following angular position and the resulting value for the first angular position is compared to a threshold value, so as to determine whether the angular velocity is zero.

11. A device for determining a resulting value for an angular position, the device comprising:

a factor determination device to determine a first factor and a second factor as a function of an initial angular position value;

a product-forming device to form a first product from a first signal and the first factor, and a second product from the second signal and the second factor;

a subtraction device for forming a subtraction result by subtracting the second product from the first product;

a comparison device to compare the subtraction result to a predetermined quantity; and

a refinement device to refine the initial angular position based on a result of the comparison to obtain an additional angular position;

wherein;

the factor determination device determines an additional first factor and an additional second factor as a function of the additional angular position;

the product-forming device forms an additional first product from the first signal and the additional first factor and additional second product from the second signal and the additional second factor;

the subtraction device forms an additional subtraction result by subtracting the additional second product from the additional first product;

the comparison device compares the additional subtraction result to the predetermined quantity; and

the refinements device determines a resulting value for a first angular position based on the comparison of the additional subtraction result to the predetermined quantity.

12. A method for determining a refined value of an angular position, the method comprising:

obtaining a first signal and a second signal using a sensor system; and

iteratively performing the following process by circuitry;

determine a first factor and a second factor as a function of a value of the angular position;

obtain a first product of the first signal and the first factor;

obtain a second product of the second signal and the second factor;

obtain a difference between the first and second products; and

refine the value of the angular position based on the obtained difference;

wherein the iterative process is performed until the value of the angular position is refined to a predetermined degree of refinement.

13. The method of claim 12, wherein, in each of the iterations, the value of the angular position is refined by either adding to the value of the angular position or subtracting from the value of the angular position a modification value.

14. The method of claim 13, wherein the modification value is halved after each of the iterations.

15. The method of claim 14, wherein, in each respective iteration, the refinement includes selecting whether to add the modification value to, or subtract the modification value from, the value of the angular position, such that an absolute value of the difference that would be obtained if a subsequent iteration would be performed would be less than an absolute value of the difference obtained in the respective iteration.

16. The method of claim 13, wherein, for each of the iterations:

the iteration further includes comparing the difference to a predetermined quantity; and

the refinement includes determining whether to add the modification value to the value of the angular position or to subtract the modification value from the value of the angular position based on the comparison.

17. The method of claim 16, wherein, in each iteration:

the respective difference is obtained by subtracting the second product from the first product;

the respective comparison indicates whether the respective obtained difference is positive or negative.

18. The method of claim 17, wherein the predetermined quantity is zero.

19. The method of claim 18, wherein for iteration other than a first iteration, an absolute value of the difference that is obtained for the respective iteration is less than an absolute value of the difference obtained in the iteration immediately preceding the respective iteration.

20. The method of claim 12, wherein, for each of the iterations:

the iteration further includes comparing the difference to a predetermined quantity; and

the refinement of the value is in accordance with the comparison.

21. The method of claim 12, wherein the sensor system includes a first sensor via which the first signal is obtained and a second sensor via which the second signal is obtained.

22. The method of claim 21, wherein each of the first and second sensors includes a coil mounted on a rotatable mechanical element, and the sensor system further includes a magnet mounted on a stationary mechanical element.