Magnetic senor digital processing interface for electrical motor application

• US 20040207392A1
• Filed: 04/22/2003
• Published: 10/21/2004
• Est. Priority Date: 04/17/2003
• Status: Active Grant

• Current Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Original Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Inventors: Kernhof, Juergen
• Granted Patent: US 7,064,538 B2
• Time in Patent Office: Days
• US Class Current: 324/207.25
• CPC Class Codes: G01D 5/24404 Interpolation using high frequency signals

Abstract

A system and methods for an interface for magnetic sensors to determine a rotational angle has been achieved. Said interface can be used for any kind of magnetic sensors providing analog signals of the sine and cosine values of the angle to be determined. Said analog signals are being processed in two measurement paths for the sine and cosine signal each until the desired angle is computed by a CORDIC processor. The first stage of said measurement path is the conversion of the sine and cosine signals from analog to digital by 2^nd order delta-sigma modulators with an over-sampling ratio. A low-pass decimation filter with sinc³ characteristic performs the digital value computation. The next stage normalizes the digitized sine and cosine values to correct offset and scaling deviations. Said CORDIC processor computes the angle to be determined by decomposing the desired rotation angle into iterations of pre-defined elementary rotation angles performing the rotation operation by simple shift-and-add operations replacing multiplication/division operations and the magnitude of the vector MAG={square root}{square root over (sin²+cos²)} using the output from said pair of normalization stages.

Claims

1. A system for an interface for magnetic sensors to determine an angle of rotation comprising:

an arrangement of magnetic sensors providing sine and cosine values of the angle to be determined;

two identical measurement paths to process said sine and cosine values each, comprising a pair of delta-sigma modulators to perform amplification and analog-to-digital conversion of said sine and cosine values, a pair of decimation filters performing the filtering and down-sampling of the delta-sigma modulator bit streams, a pair of a normalization stages performing the processing of normalization parameters;

a processor to compute the angle to be determined using the output from said pair of normalization stages;

a register file to store the results of said processor; and

a processor interface to external devices.

2. The system of claim 1 wherein said magnetic sensors are anisotropic magnetoresistive (AMR) sensors.

3. The system of claim 1 wherein said magnetic sensors are giant magnetoresistive (GMR) sensors.

4. The system of claim 1 wherein said magnetic sensors are Hall sensors.

5. The system of claim 1 wherein said pair of delta-sigma modulators are second order delta-sigma modulators.

6. The system of claim 5 wherein said delta-sigma modulators are operating with an over-sampling ratio.

7. The system of claim 6 wherein said over-sampling ratio amounts to 128.

8. The system of claim 1 wherein said decimation filters are low-pass filters.

9. The system of claim 8 wherein said low-pass filters have a sinc³ characteristic.

10. The system of claim 1 wherein said normalization stages are providing offset correction and scaling correction.

11. The system of claim 10 wherein said normalization stages are having four registers for offset correction of sine and cosine and scale factors for sine and cosine.

12. The system of claim 1 wherein said processor is a COordinate Rotational Digital Computer (CORDIC) processor.

13. The system of claim 1 wherein said processor calculates, additionally to the desired angle, the magnitude of the vector provided by the normalization stages following the equation MAG={square root}{square root over (sin²+cos²)}.

14. The system of claim 1 wherein said processor decomposes the desired rotation angle into iterations of pre-defined elementary rotation angles performing the rotation operation by simple shift-and-add operations replacing multiplication/division operations.

15. The system of claim 14 wherein said processor is using a lookup table to accelerate the iterations performed to compute the desired angle.

16. The system of claim 1 wherein said processor interface is a 16-bit peripheral bus interface of a micro-controller.

17. A system for an interface for magnetic sensors to determine an angle of rotation comprising:

an arrangement of anisotropic magnetoresisitive (AMR) sensors providing sine and cosine values of the angle to be determined;

two identical measurement paths to process said sine and cosine values each, comprising a pair of second order delta-sigma modulators operating with an over-sampling ratio to perform amplification and analog-to-digital conversion of said sine and cosine values, a pair of low-pass decimation filters having a sinc^M characteristic performing the filtering and down-sampling of the delta-sigma modulator bit streams, a pair of a normalization stages using offset and scaling normalization parameters;

a COordinate Rotational Digital Computer (CORDIC) processor to compute the angle to be determined by decomposing the desired rotation angle into iterations of pre-defined elementary rotation angles performing the rotation operation by simple shift-and-add operations replacing multiplication/division operations and the magnitude of the vector MAG={square root}{square root over (sin²+cos²)} using the output from said pair of normalization stages;

a register file to store said rotation angle and said vector magnitude; and

a 16-bit peripheral bus interface of a micro-controller.

18. The system of claim 17 wherein said over-sampling ratio amounts to 128.

19. The system of claim 17 wherein said sinc^M characteristic is a sinc³ characteristic.

20. A method for an interface for magnetic sensors to determine an angle of rotation comprising:

providing an arrangement of magnetic sensors providing sine and cosine values of said rotational angle, two measurement paths comprising a pair of delta-sigma modulators, a pair of decimation filters and a pair of normalization stages, further a processor, a register file and a processor interface to external devices;

perform analog-to digital conversion of sine and cosine values provided by magnetic sensors;

perform low-pass filtering and down-sampling of digitized bit stream;

normalize sine and cosine values to correct offset and scaling deviations;

compute desired rotation angle and magnitude of vector MAG=+{square root}{square root over (sin²+cos²)}; and

shift computed values of rotation angle and vector magnitude into register file.

21. The method of claim 20 wherein said magnetic sensors are anisotropic magnetoresistive (AMR) sensors.

22. The method of claim 20 wherein said magnetic sensors are giant magnetoresistive (GMR) sensors.

23. The method of claim 20 wherein said magnetic sensors are Hall sensors.

24. The method of claim 20 wherein said pair of delta-sigma modulators are second order delta-sigma modulators.

25. The method of claim 24 wherein said delta-sigma modulators are operating with an over-sampling ratio.

26. The method of claim 25 wherein said over-sampling ratio amounts to 128.

27. The method of claim 20 wherein said decimation filters are low-pass filters.

28. The method of claim 27 wherein said low-pass filters have a sinc³ characteristic.

29. The method of claim 20 wherein said normalization stages are providing offset correction and scaling correction.

30. The method of claim 29 wherein said normalization stages are having four registers for offset correction of sine and cosine and scale factors for sine and cosine.

31. The method of claim 20 wherein said processor is a COordinate Rotational Digital Computer (CORDIC) processor.

32. The method of claim 20 wherein said processor calculates, additionally to the desired angle, the magnitude of the vector provided by the normalization stages following the equation MAG={square root}{square root over (sin²+cos²)}.

33. The method of claim 20 wherein said processor decomposes the desired rotation angle into iterations of pre-defined elementary rotation angles performing the rotation operation by simple shift-and-add operations replacing multiplication/division operations.

34. The method of claim 33 wherein said processor is using a lookup table to accelerate the iterations performed to compute the desired angle.

35. The method of claim 20 wherein said processor interface is a 16-bit peripheral bus interface of a micro-controller.