ROTATION ANGLE SENSOR HAVING TWO SENSOR SIGNALS AND OPERATING METHOD

Abstract

The invention relates to a sensor arrangement for determining a rotation angle of a diametrically magnetized magnet about a rotation axis relative to a main support, containing two sensors at different circumferential positions having a radial distance to the rotation axis in order to detect tangential and axial components of the measurement field of the magnet, and an evaluating unit for determining the rotation angle from the components based on an arctangent function. In a method for determining the rotation angle, the components are detected by the sensors and the rotation angle is determined therefrom based on an arctangent function.

Claims

1. A sensor arrangement for determining a rotation angle of a magnet about an axis of rotation relative to a base carrier, the sensor arrangement comprising: the base carrier; the magnet configured to rotate relative to the base carrier about the axis of rotation to generate a magnetic measuring field; a first sensor positionally fixed relative to the base carrier and configured to capture a first tangential component and a first axial component of the measuring field with respect to the axis of rotation, wherein the first sensor is arranged at a first circumferential position with respect to the axis of rotation and at a first radial distance from the axis of rotation; at least one second sensor configured to capture a second tangential component and a second axial component of the measuring field with respect to the axis of rotation and which is arranged at a second circumferential position with respect to the axis of rotation and at a second radial distance from the axis of rotation; and an evaluation unit configured to determine the rotation angle from at least three of the first tangential component, the second tangential component, the first axial component, or the second axial component by means of an arc tangent function.

2. The sensor arrangement of claim 1, wherein: at least one of the first sensor or the second sensor is arranged in a manner offset by an axial distance in relation to a central plane, lying transversely with respect to the axis of rotation of the magnet in the axial direction of the axis of rotation.

3. The sensor arrangement of claim 2, wherein: at least two of the first sensor or the second sensor are arranged at at least one of a same axial distance or a same radial distance from the axis of rotation.

4. The sensor arrangement of claim 1, wherein: the first circumferential position and the first circumferential position are offset at right angles to one another.

5. The sensor arrangement of claim 1, wherein: the magnet is rotationally symmetrical with respect to the axis of rotation.

6. The sensor arrangement of claim 5, wherein: the magnet is a ring magnet which is arranged concentrically with respect to the axis of rotation.

7. The sensor arrangement of claim 1, wherein: an axial position of the magnet along the axis of rotation is variable with respect to the base carrier.

8. The sensor arrangement of claim 1, wherein: the evaluation unit comprises a raw angle module configured to form a raw angle for a respective sensor from a respective axial component and tangential component of the same sensor by means of an arc tangent function, wherein the evaluation unit is further configured to determine the rotation angle by processing the raw angle.

9. The sensor arrangement of claim 1, wherein: the evaluation unit comprises a mean value module configured to form a mean value from at least two of the first axial component, the second axial component, the first tangential component, or the second tangential component, wherein the evaluation unit is further configured to determine the rotation angle by processing the mean value.

10. A method for determining a rotation angle of a magnet about an axis of rotation relative to a base carrier, the method comprising: rotating the magnet relative to the base carrier about the axis of rotation to generate a magnetic measuring field; capturing, by a first sensor, a first tangential component and a first axial component of the measuring field with respect to the axis of rotation, wherein the first sensors is positionally fixed relative to the base carrier and is arranged at a first circumferential position with respect to the axis of rotation and at a first radial distance from the axis of rotation; capturing, by a second sensor, a second tangential component and a second axial component of the measuring field with respect to the axis of rotation, wherein the first sensors is arranged at a second circumferential position with respect to the axis of rotation and at a second radial distance from the axis of rotation; determining, by an evaluation unit, the rotation angle from at least three of the first tangential component, the second tangential component, the first axial component, or the second axial component by means of an arc tangent function.

11. The method of claim 10, further comprising: forming a raw angle for a respective sensor from a respective axial component and tangential component of the same sensor by means of an arc tangent function; and processing, by the evaluation unit, the raw angle to form the rotation angle.

12. The method of claim 11, further comprising: forming the raw angle is formed by means of an unweighted arc tangent function.

13. The method of claim 10, further comprising: forming at least one mean value from at least two of the first axial component, the second axial component, the first tangential component, or the second tangential component; and processing, by the evaluation unit, the mean value to form the rotation angle.

14. The method of claim 10, further comprising: forming individual raw angles for at least the first sensor and the second sensor, wherein the positions of the first sensor and the second sensor are selected in such a way that the individual raw angles have an axially symmetrical profile in relation to an ideal angle straight line, and the rotation angle is determined by forming mean values of the two raw angles.

15. The method of claim 10, further comprising: optimizing a profile of the determined rotation angle plotted against the actual rotation angle by means of an FEM analysis of the measuring field at the location of the sensor.

16. The method of claim 11, further comprising: forming at least one mean value from at least two of the first axial component, the second axial component, the first tangential component, the second tangential component, or the raw angle; and processing, by the evaluation unit, the mean value to form the rotation angle.

17. The sensor arrangement of claim 8, wherein: the evaluation unit comprises a mean value module configured to form a mean value from at least two of the first axial component, the second axial component, the first tangential component, the second tangential component, or the raw angle, wherein the evaluation unit is further configured to determine the rotation angle by processing the mean value.

Description

[0045] Other features, effects and advantages of the invention can be found in the following description of a preferred exemplary embodiment of the invention as well as of the appended figures, in which, in each case in a schematic basic diagram:

[0046] FIG. 1 shows a sensor arrangement according to the invention in a plan view and

[0047] FIG. 2 shows it in a side view,

[0048] FIG. 3 shows the raw angles of the two sensors from FIGS. 1 and 2 as well as the actual rotation angle and the determined rotation angle, plotted against the actual rotation angle,

[0049] FIG. 4 shows a sensor arrangement according to the prior art, and

[0050] FIG. 5 shows the raw angle of the sensor from FIG. 4, plotted against the actual rotation angle according to the prior art.

[0051] FIG. 1 (plan view in the direction of the arrow I in FIG. 2) and FIG. 2 (section in the direction of the arrows II-II in FIG. 1) show a sensor arrangement 8 according to the invention. The latter serves to determine a (determined) rotation angle WE of a magnet 6 about an axis of rotation 12 relative to a base carrier 14. The determined rotation angle WE is intended to ideally correspond here to the actual rotation angle WT of the magnet 6 about the axis of rotation 12. The base carrier 14 and magnet 6 are part of the sensor arrangement 8 here. The magnet 6 can therefore rotate about the axis of rotation 12 (indicated by means of a double arrow) and is diametrically magnetized here with respect to the axis of rotation 12. The magnet 6 therefore generates a magnetic measuring field 16 which is indicated here only symbolically by field lines.

[0052] A first sensor 18a of the sensor arrangement 8 is arranged in a positionally fixed manner relative to the base carrier 14. Said sensor 18a serves to capture a first tangential component KTa and a first axial component KAa of the measuring field 16. The terms “axial”, “tangential” etc. are to be understood here as being with respect to the axis of rotation 12. The first sensor 18a is arranged here at a first circumferential position UPa with respect to the axis of rotation 12 and at a first radial distance ARa from the axis of rotation 12.

[0053] The sensor arrangement 8 also contains a second sensor 18b for capturing a second tangential component KTb and a second axial component KAb of the measuring field 16. The second sensor 18b is arranged at a second circumferential position UPb with respect to the axis of rotation 12 and at a second radial distance RAb with respect to the axis of rotation 12.

[0054] The sensor arrangement 8 also contains an evaluation unit 28 for determining the rotation angle WE. In the example, the evaluation unit 28 uses for this purpose both tangential components KTa,b and axial components KAa,b of the first sensor 18a and second sensor 18b, as will be explained further below.

[0055] Both sensors 18a,b are arranged in an offset manner, by a first and a second axial distance AAa,b, which are the same here, in relation to a central plane 24, lying transversely with respect to the axis of rotation 12, of the magnet 6 in the axial direction of the axis of rotation 12. Furthermore, both sensors 18a,b are at the same radial distance ARa,b in relation to the axis of rotation 12. The two circumferential positions UPa,b also enclose a right angle with respect to the axis of rotation 12 here.

[0056] The magnet 6 is also embodied to be rotationally symmetrical with respect to the axis of rotation 12, here as a ring magnet which is arranged concentrically with respect to the axis of rotation 12. Therefore, said ring magnet has a central opening 10, which serves as a feedthrough for cables (not illustrated) when the sensor is installed in an application (not illustrated), e.g. a shift lever of an automobile.

[0057] The axial position PA of the magnet 6 on the axis of rotation 12 is variable, i.e. the magnet 6 can move in the direction of the illustrated double arrow. The axial distances AAa,b change uniformly during such a movement.

[0058] The evaluation unit 28 contains a raw angle module 32. The latter serves to form a raw angle WRa,b for the respective sensor 18a,b from a respective axial component KAa,b and tangential component KTa,b of the same sensor 18a,b by means of an arc tangent function, which raw angle WRa,b is then processed to form the rotation angle WE.

[0059] The evaluation unit 28 also contains a mean value module 30. The latter serves to form a mean value M from the two determined raw angles WRa,b, which mean value M is then processed to form the rotation angle WE, or constitutes the determined rotation angle WE here.

[0060] FIG. 3 illustrates how the two raw angles WRa,b are easily determined by means of a pure arc tangent function, that is to say without the abovementioned factors kx, ky or with kx=ky=1, and therefore have a nonlinear profile 26 when plotted against the actual rotation angle WT. The deviations of the profiles 26 from the actual rotation angle WT are illustrated in a highly enlarged fashion in the example. In practice, they vary within the range of single-digit degrees, generally below 1°. The deviations from or distortions of the actual rotation angle WT are in each case basically positively and negatively sinusoidal.

[0061] However, the formation of mean values

[00002]$\mathrm{WE}=\frac{\mathrm{WRa}+\mathrm{WRb}}{2}$

between the two raw angles WRa,b then yields the determined rotation angle WE on the ideal straight line which is described by the absolute rotation angle WT. Residual errors arise through nonlinearities of the overall system.

LIST OF REFERENCE SYMBOLS

[0062] 6 Magnet [0063] 8 Sensor arrangement [0064] 10 Opening [0065] 12 Axis of rotation [0066] 14 Base carrier [0067] 16 Measuring field [0068] 18a,b Sensor [0069] 24 Central plane [0070] 26 Profile [0071] 28 Evaluation unit [0072] 30 Mean value module [0073] 32 Raw angle module [0074] 100 Sensor arrangement [0075] 102 Sensor [0076] 104 Base carrier [0077] 106 Magnet [0078] 108 Axis of rotation [0079] 110 Measuring field [0080] 112 Evaluation unit [0081] WT Rotation angle (actual) [0082] WE Rotation angle (determined) [0083] N North pole [0084] S South pole [0085] KAa,b Axial component [0086] KTa,b Tangential component [0087] AAa,b Axial distance [0088] ARa,b Radial distance [0089] UPa,b Circumferential position [0090] M Mean value [0091] PA Axial position [0092] WRa,b Raw angle