CLUTCH ACTUATOR, DETECTION SYSTEM AND METHOD FOR DETECTING AN ANGULAR POSITION OF A ROTARY COMPONENT

Abstract

A first sensor signal and a second sensor signal are provided by a sensor unit to an evaluation unit. The first sensor signal is dependent on the angular position, and the second sensor signal is phase-shifted by 90° with respect to the first sensor signal. A noise value that is superimposed on each sensor signal due to noise in the corresponding sensor signal is determined by the evaluation unit. Each sensor signal is corrected by the evaluation unit based on the noise value determined for the corresponding sensor signal. Highest amplitudes for each of the first and second sensor signals are determined by the evaluation unit as a maximum value of amplitudes of the respective sensor signals detected over multiple revolutions of the rotational element. An angular portion of a rotational component is determined by the evaluation unit based on output from an atan2-function that takes the first and second sensor signals and the highest amplitudes as input.

Claims

1. A method for detecting an angular position of a component about a rotational axis, the method comprising providing, via a sensor unit, a first sensor signal and a second sensor signal to an evaluation unit, wherein the sensor unit includes a fixed sensor element and a rotational element rotatable relative to the sensor element and jointly with the rotational component, and wherein the first sensor signal is dependent on the angular position, and the second sensor signal is phase-shifted by 90° with respect to the first sensor signal; determining, via the evaluation unit, a noise value that is superimposed on each sensor signal due to noise in the corresponding sensor signal; then correcting, via the evaluation unit, each sensor signal based on the noise value determined for die corresponding sensor signal; determining, via the evaluation unit, highest amplitudes for each of the first and second sensor signals as a maximum value of amplitudes of the respective sensor signals detected over multiple revolutions of the rotational element, and determining, via the evaluation unit, the angular position based on output front an atan2-function that takes the first and second sensor signals and the highest amplitudes as input.

2. The method according to claim 1, further comprising, adjusting, via the evaluation unit, the noise value superimposed on each sensor signal at each revolution of thy relational element.

3. The method according to claim 1, wherein the highest amplitude of the respective sensor signal is determined as half of a distance between a maximum amplitude and a minimum amplitude of the corresponding sensor signal.

4. The method according to claim 1, further comprising determining, via the evaluation unit, an amplitude error by comparing the highest amplitudes, and updating, via the evaluation unit, one of the highest amplitudes based on the amplitude error.

5. The method according to claim 1, further comprising determining, via the evaluation unit, the noise value that is superimposed on each sensor signal based on a number of measurement points.

6. The method according to claim 5, wherein the number of measurement points is at least 2000.

7. The method according to anyone claim 1, further comprising determining, via the evaluation unit, the noise value that is superimposed on each sensor signal based on a temperature of the sensor unit.

8. The method according to claim 1, wherein the rotational component is a rotor of an electric motor or a component connected in a rotationally fixed manner to the rotor.

9. A detection system for detecting an angular position of a rotational component, the detection system comprising: an evaluation unit, and a sensor unit configured to provide a first sensor signal and a second sensor signal to the evaluation unit, wherein the sensor unit includes a fixed sensor dement and a rotational element rotatable relative to the sensor element and jointly with the rotational component, and wherein the first sensor signal is dependent on the angular position, and the second sensor signal is phase-shifted by 90° with respect to the first sensor signal, wherein the evaluation unit is configured to: determine a noise value that is superimposed on each sensor signal due to noise in the corresponding sensor signal; then correct each sensor signal based on the noise value determined for the corresponding sensor signal; determine highest amplitudes for each of the first and second sensor signals as a maximum value of amplitudes of the respective sensor signals detected over multiple revolutions of the rotational element; and determine the angular position based on output from an atan2-function that takes the first and second sensor signals and the highest amplitudes as input.

10. A clutch actuator for a clutch having a detection system according to claim 9.

11. The method according to claim 5, wherein the number of measurement points are is determined based on a rotational speed of the rotational element and a sampling frequency of the sensor element.

12. The method according to claim 1, wherein the sensor element is axially spaced from the rotational element.

13. The detection system according to claim 9, wherein the evaluation unit is further configured to adjust the noise value that is superimposed on each sensor signal at each revolution of the rotational element.

14. The detection system according to claim 9, wherein the evaluation unit is further configured to determine the noise value that is superimposed on each sensor signal based on a number of measurement points.

15. The detection system according to claim 14, wherein the number of measurement points are is determined based on a rotational speed of the rotational element and a sampling frequency of the sensor element.

16. The detection system according to claim 14, wherein the number of measurement points is at least 2000.

17. The detection system according to claim 9, wherein the evaluation unit is further configured to determine the noise value that is superimposed on each sensor signal based on a temperature of the sensor unit.

18. The detection system according to claim 9, wherein the rotational component is a rotor of an electric motor or a component connected in a rotationally fixed manner to the rotor.

19. The detection system according to claim 9, wherein, the highest amplitude of the respective sensor signal is determined as half of a distance between a maximum amplitude and a minimum amplitude of the corresponding sensor signal.

20. The detection system according to claim 9, wherein the sensor element is axially spaced from the rotational element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The disclosure is described in detail below with reference to the drawings. Specifically:

[0034] FIG. 1: shows a spatial cross-section through a clutch actuator with a sensor unit in an exemplary embodiment of the disclosure.

[0035] FIG. 2: shows a first and second sensor signal of a sensor unit in an exemplary embodiment of the disclosure.

[0036] FIG. 3: shows the influence of an amplitude deviation on the angular position.

[0037] FIG. 4: shows the effect of noise on a sensor signal of the sensor unit in an exemplary embodiment of the disclosure.

[0038] FIG. 5: shows a method for detecting an angular position in an exemplary embodiment of the disclosure.

[0039] FIG. 6: shows a comparison of the accuracy of a method in an exemplary embodiment of the disclosure versus a conventional method.

[0040] FIG. 7: shows a comparison of the accuracy of an optimized method in another exemplary specific embodiment of the disclosure versus a conventional method.

[0041] FIG. 8: shows a graph of an angular error as a function of the amplitude ratio.

DETAILED DESCRIPTION

[0042] FIG. 1 shows a spatial cross-section through a clutch actuator 10 with a sensor unit 12 in an exemplary embodiment of the disclosure. The clutch actuator 10 is a modular clutch actuator, a so-called MCA, comprising a spindle 14 and an electric motor 16 with a rotatable rotor 18. The spindle 14 performs a linear movement for clutch actuation and is moved by a rotational movement of the electromechanically driven rotor 18 via a planetary roller screw drive 20, abbreviated PWG.

[0043] The sensor unit 12 is arranged to detect an angular position of the rotor 18 and has a rotational element 22 which is embodied as a magnetic ring 26 that is non-rotatably connected to a rotational component 24 embodied as the rotor 18. The magnetic ring 26 is in particular a permanent magnet and diametrically magnetized. The sensor unit 12 also has a sensor element 28 which is embodied as a magnetic sensor, in particular as a Hail sensor. The sensor element 28 is mounted on a circuit board 30 axially spaced from the rotational element 22 and enables a magnetic field emanating from the rotational element 22 to be detected.

[0044] The effect of the magnetic field emanating from rotational element 22 on the sensor element 28 makes it possible to detect the angular position of rotational component 24, i.e., the rotor 18, since the diametrical magnetization of the magnetic ring 26 changes the magnetic field as a function of the angular position of the rotor 18.

[0045] FIG. 2 shows a first and second sensor signal S.sub.1, S.sub.2 of a sensor unit in an exemplary embodiment of the disclosure. The first sensor signal S.sub.1 is a sine signal and the second sensor signal S.sub.2 is a 90° phase shifted cosine signal. The first sensor signal S.sub.1 arises at a first measurement position on a sensor element and the second sensor signal S.sub.2 at a second measurement position on the sensor element that is perpendicular thereto about the rotational axis. The phase shift between the first sensor signal S.sub.1 and the second sensor signal 5.sub.2 is due to the perpendicular position of the first and second measurement positions to one another.

[0046] The graph of an ideal first sensor signal S.sub.1 is plotted in comparison with the first sensor signal S.sub.1. The first sensor signal S.sub.1 is subject to an amplitude shift relative to the ideal first sensor signal S.sub.1, which reduces the amplitude. The reason for this can be attenuations, interference effects and/or measurement errors.

[0047] FIG. 3 shows the influence of an amplitude shift on the angular position. The first sensor signal S.sub.1 is shown as a projection onto the Y-axis and the second sensor signal S.sub.2 as a projection onto the x-axis. Based on the illustration in FIG. 2, the first sensor signal S.sub.1 is reduced by an amplitude shift, resulting in an ellipse instead of a circle, which is the case with the idealized first and second sensor signals S.sub.1, S.sub.2. This causes an angular error ϵ in detecting the angular position α. The angle error ϵ, which arises due to the amplitude shift between the amplitude A.sub.l of the first sensor signal and the amplitude A.sub.2 of the second sensor signal, can be calculated as follows

[00006]$\begin{array}{cc}ϵ=\arcsin \frac{\gamma -1}{\gamma +1}& \left(8\right)\end{array}$$\mathrm{with}$$\begin{array}{cc}\gamma =\frac{A_1}{A_2}& \left(9\right)\end{array}$

[0048] However, knowledge of the actual amplitudes of the first and second sensor signals S.sub.1, S.sub.2 are crucial for detecting the angular position α. This is because the angular position α can be calculated using the amplitudes A.sub.1, A.sub.2 as a function of the first sensor signal S.sub.1 and the second sensor signal S.sub.2 via an atan2 function.

[0049] In this case, the amplitudes A.sub.1, A.sub.2 of the first and second sensor signals S.sub.1, S.sub.2 may be determined using a max-min method, in which the calculation power can be kept as low as possible. The amplitudes A.sub.1, A.sub.2 of the first and second sensor signals S.sub.1, S.sub.2 recorded during the rotation of the rotational element are stored and corrected during operation of the sensor unit as soon as correspondingly higher values are determined. However, this method is susceptible to noise.

[0050] FIG. 4 shows the effect of noise on a sensor signal S of the sensor unit in an exemplary embodiment of the disclosure. The solid line corresponds to an ideal curve of the sensor signal S, which can be the first or second sensor signal S.sub.1. S.sub.2, as a function of the angular position a and the dashed curves show the bandwidth of the noise-affected values of the sensor signal S.

[0051] The noise can be described by a probability function g. If the noise is assumed to be white noise, this can be represented by a normal distribution. Due to the noise, a maximum expected noise value N is assumed.

[0052] An ideal maximum amplitude S.sub.max of the sensor signal S deviates from the measured maximum amplitude S.sub.max of the sensor signal S. An ideal minimum amplitude S.sub.min of the sensor signal S therefore deviates from the measured minimum amplitude S.sub.min of the sensor signal S.

[0053] FIG. 5 shows a method 100 for detecting an angular position α in an exemplary embodiment of the disclosure. The first and second sensor signals S.sub.1, S.sub.2 output by the sensor unit 12 are output to an evaluation unit 32. In an amplitude determination step AM, the evaluation unit 32 determines the respective highest amplitude Â.sub.1, Â.sub.2 of the first and second sensor signals S.sub.1, S.sub.2. In an evaluation step AW, the evaluation unit 32 determines the angular position a using an atan2 function that takes the first and second sensor signal S.sub.1, S.sub.2 and the determined highest amplitudes Â.sub.1; Â.sub.2 as input.

[0054] In a monitoring step ÜW, the highest amplitude Â.sub.1 of the first sensor signal S.sub.1 and the highest amplitude Â.sub.2 of the second sensor signal S.sub.2 is calculated in each case as the maximum value of the respective sensor signals S.sub.1, S.sub.2 determined over at least one revolution of the rotational element 22. The highest amplitude Â.sub.1 of the first sensor signal S.sub.1 is the maximum value of the amplitude A.sub.1 of the first sensor signal S.sub.1 and can be calculated via (1).

[0055] Accordingly, the highest amplitude Â.sub.2 of the second sensor signal S.sub.2 is the maximum value of the amplitude A.sub.2 of the second sensor signal S.sub.2, following the calculation according to (2).

[0056] The respective amplitude A, for example at each revolution, is calculated according to (6) with the maximum amplitude S.sub.max and the minimum amplitude S.sub.min of the respective sensor signal S.sub.1, S.sub.2.

[0057] In a signal detection step SE, the evaluation unit 32 calculates the respective sensor signal S.sub.1, S.sub.2 based on a number of measurement points m of the sensor element 28. The number of measurement points m can be calculated from a rotational speed n and a sampling frequency f.sub.s of the sensor element 28 according to (5).

[0058] In a noise detection step RE preceding the amplitude determination step AM, a noise value N, which is superimposed on the corresponding first and/or second sensor signal S.sub.1, S.sub.2, is calculated and transferred to the amplitude determination step AM, in which the former is taken into account according to (7).

[0059] As a result, the amplitude A and also the highest amplitude Â.sub.1, Â.sub.2 of the respective sensor signal S.sub.1, S.sub.2 can be determined more precisely and the error E in the calculation of the angular position α can thus be reduced. The angular position α can be detected more accurately, faster and with as little computational power as possible.

[0060] The noise value N is calculated and taken into account at least in each revolution, for example. The noise value N can be calculated from the relation according to (3), with the temperature T of the sensor unit 12, the probability function g and with the measurement point ratio i, which can be calculated from (5).

[0061] It is advantageous if the relation f(T) is described by (5), with the reference temperature T.sub.r and the previously determined value f(T.sub.r) and the parameters a.sub.1 and a.sub.2 to be defined in advance, for example before commissioning.

[0062] A more precise calculation with an assumed non-linear profile of the noise value N can be performed using (6).

[0063] The parameters a, b and c must be determined, for example, before the sensor unit 12 is commissioned. This relationship can be stored in a lookup table and retrieved from it during operation.

[0064] Assuming white noise, the probability function g is a normal distribution and can be calculated via (7).

[0065] FIG. 6 shows a comparison of the accuracy of a method in an exemplary embodiment of the disclosure versus a conventional method. Curve 102 represents the accuracy curve of a conventional method as a function of the number of measurement points m and curve 104 represents the accuracy curve of a method in an exemplary embodiment of the disclosure.

[0066] Compared to curve 102, above a number of measurement points in of 400, curve 104 is far more accurate and converges with an increasing number of measurement points m. In contrast to this, the inaccuracy of the conventional method increases with an increasing number of measurement points m.

[0067] In the method in an exemplary embodiment of the disclosure, a linear dependency of the noise value N on the probability function g(i) was assumed. For example, from the ratio i calculated during operation dependent on the number of measurement points m according to (4) and a lookup table mapping the relationship between i and g(i), created in particular initially, for example in an end-of-line determination, the respective associated value g(i) can be determined, possibly by linear interpolation during operation.

[0068] FIG. 7 shows a comparison of the accuracy of a method in another exemplary embodiment of the disclosure versus a conventional method. In the curve 106, a non-linear dependency according to (6) was assumed between the noise value N and the probability function g(i).

[0069] In comparison to the shape of the curve 102 for a conventional method and also in comparison to the method with an assumed linear dependency, the accuracy can be increased even further.

[0070] FIG. 8 shows a graph of an angular error ϵ as a function of the amplitude ratio γ. The angular error ϵ is plotted as a function of the amplitude ratio γ according to (9). In practice, the angular error ϵ should be less than ±0.25%, which means that according to (8) the amplitude difference must not exceed 0.5%. This requirement can be achieved with a number of measurement points m of 2000. If the sampling frequency f.sub.s is 20 kHz the rotational speed n should therefore be below 600 rpm.

LIST OF REFERENCE SYMBOLS

[0071] 10 Clutch actuator [0072] 12 Sensor unit [0073] 14 Spindle [0074] 16 Electric motor [0075] 18 Rotor [0076] 20 Planetary roller screw drive [0077] 22 Rotational element [0078] 24 Rotational component [0079] 26 Magnetic ring [0080] 28 Sensor element [0081] 30 Circuit board [0082] 32 Evaluation Unit [0083] 100 Method [0084] 102 Curve [0085] 104 Curve [0086] 106 Curve [0087] A.sub.1 Amplitude of the first sensor signal [0088] Â.sub.1 Highest amplitude of the first sensor signal [0089] A.sub.2 Amplitude of the second sensor signal [0090] Â.sub.2 Highest amplitude of the second sensor signal [0091] α Angular position [0092] c Angle discretization [0093] ϵ Angular error [0094] f.sub.s Sampling frequency [0095] g Probability function [0096] γ Amplitude ratio [0097] i Measurement point ratio [0098] m Number of measurement points [0099] n Rotational speed [0100] N Noise value [0101] S.sub.1 First sensor signal [0102] S.sub.1 First ideal sensor signal [0103] S.sub.2 First sensor signal [0104] S.sub.2 Second ideal sensor signal [0105] S Sensor signal [0106] S.sub.max Ideal maximum amplitude [0107] S.sub.max Maximum amplitude [0108] S.sub.min Ideal minimum amplitude [0109] S.sub.min Minimum amplitude [0110] T Temperature [0111] AM Amplitude determination step [0112] AW Evaluation step [0113] ÜW Monitoring step [0114] RE Noise detection step [0115] SE Signal acquisition step