CLUTCH ACTUATOR, SENSING SYSTEM AND METHOD FOR SENSING AN ANGULAR POSITION OF A ROTATIONAL 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 is associated with a first detection position, and the second sensor signal is associated with a second detection position lying about the rotational axis perpendicular to the first detection position. An angular position 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 as input. A harmonic error is determined by the evaluation unit based on a periodic error signal that is superimposed on each of the sensor signals. An angular error of the angular position is determined by the evaluation unit based on the harmonic error. The angular position is updated by the evaluation unit based on the angular error.

Claims

1. A method for detecting an angular position of a rotational component rotatable 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 first sensor signal is dependent on the angular position and is associated with a first detection position, and the second sensor signal is associated with a second detection position lying about the rotational axis perpendicular to the first detection position; determining, via the evaluation unit, the angular position based on output from an atan2-function that takes the first and second sensor signals as input; determining, via the evaluation unit, a harmonic error based on a periodic error signal that is superimposed on each of the sensor signals; determining, via the evaluation unit, an angular error of the angular position based on the harmonic error; and updating, via the evaluation unit, the angular position based on the angular error.

2. The method according to claim 1, further comprising, determining, via the evaluation unit, an error amplitude and an error phase of each periodic error signal via a gradient-based method.

3. The method according to claim 3, further comprising determining, via the evaluation unit, an error amplitude and an error phase of each periodic error signal via a least squares method.

4. The method according to claim 3, further comprising determining, via the evaluation unit, the error amplitude and the error phase additionally via a gradient-based method.

5. The method according to claim 1, further comprising determining, via the evaluation unit, the angular error based on an error amplitude of each periodic error signal and a signal amplitude of each sensor signal.

6. The method according to claim 5, wherein the angular error is determined via a first calculation method when the respective periodic error signal changes concurrently with the corresponding sensor signal and via a second calculation method when the respective periodic error signal changes oppositely to the corresponding sensor signal.

7. The method according to claim 1, further comprising: assigning, via the evaluation unit, an error frequency to each periodic error signal, wherein the error frequency is integrally dependent on a rotational frequency of the corresponding sensor signal; and determining the angular error based on the error frequency.

8. The method according to claim 1, further comprising, prior to determining at least one of the angular position or the angular error, correcting, via the evaluation unit, at least one of the sensor signal based on at least one of an amplitude error, a phase error, or an orthogonal error.

9. A detection system for detecting an angular position of a rotational component rotatable about a rotational axis, 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 first sensor signal is dependent on the angular position and is associated with a first detection position, and the second sensor signal is associated with a second detection position lying about the rotational axis perpendicular to the first defection position; wherein the evaluation unit is configured to: determine the angular position based on output from an atan2-function that takes the first and second sensor signals as input; determine a harmonic error based on a periodic error signal that is superimposed on each of the sensor signals; determine an angular error of the angular position based on the harmonic error; and update the angular position based on the angular error.

10. A clutch actuator for clutch actuation, comprising a detection system according to claim 9.

11. The method according to claim 1, wherein the sensor unit includes: a fixed sensor element; and a rotational element that can rotate relative to the sensor element and jointly with the rotational component.

12. The method according to claim 11, 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 determine an error amplitude and an error phase of each periodic error signal via a gradient-based method.

14. The detection system according to claim 9, wherein the evaluation unit is further configured to determine an error amplitude and an error phase of each periodic error signal via a least squares method.

15. The detection system according to claim 14, wherein the evaluation unit is further configured to determine the error amplitude and the error phase additionally via a gradient-based method.

16. The detection system according to claim 9, wherein the evaluation unit is further configured to determine the angular error based on an error amplitude of each periodic error signal and a signal amplitude of each sensor signal.

17. The detection system according to claim 16, wherein the angular error is determined via a first calculation method when the respective periodic error signal changes concurrently with the corresponding sensor signal and via a second calculation method when the respective periodic error signal changes oppositely to the corresponding sensor signal.

18. The detection system according to claim 9, wherein the evaluation unit is further configured to: assign an error frequency to each periodic error signal, wherein the error frequency is integrally dependent on a rotational frequency of the corresponding sensor signal; and determine the angular error based on the error frequency.

19. The detection system according to claim 9, wherein the evaluation unit is further configured to, prior to determining at least one of the angular position or the angular error, correct at least one of the sensor signals based on at least one of an amplitude error, a phase error, or an orthogonal error.

20. The detection system according to claim 9, wherein the sensor unit includes: a fixed sensor element; and a rotational element that can rotate relative to the sensor element and jointly with the rotational component; wherein the sensor element is axially spaced from the rotational element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The disclosure is described in detail below with reference to the drawings. In the figures:

[0037] FIG. 1: shows a spatial cross-section through a clutch actuator with a sensor unit according to an exemplary embodiment of the disclosure.

[0038] FIG. 2: shows a flow chart of a method for the sensing of an angular position according to an exemplary embodiment of the disclosure.

[0039] FIG. 3: shows a comparison between a sensor signal with and without harmonic error.

[0040] FIG. 4: shows a curve graph and phase progression of a sensor signal influenced by a concurrent error signal.

[0041] FIG. 5: shows a curve graph and phase progression of a sensor signal influenced by an opposing error signal.

[0042] FIG. 6: shows a cost function of a harmonic optimization task to determine the error signal parameters.

[0043] FIG. 7: shows an angular error profile depending on the harmonic error when using the method according to an exemplary embodiment of the disclosure.

DETAILED DESCRIPTION

[0044] FIG. 1 shows a spatial cross-section through a clutch actuator 10 having a sensor unit 12 according to 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 having 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.

[0045] 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 Hall 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.

[0046] The effect of the magnetic field emanating from the rotational element 22 on the sensor element 28 makes it possible to detect the angular position of the rotational component 24, i.e., the rotor 18, since the diametric magnetization of magnetic ring 26 changes the magnetic field depending on the angular position of the rotor 18.

[0047] FIG. 2 shows a flow chart of a method 100 for sensing an angular position α according to an exemplary embodiment of the disclosure. The sensor unit 12 outputs to an evaluation unit 32 a first sensor signal S.sub.1 dependent upon the angular position α and assigned to a first sensing position, and a second sensor signal S.sub.2 assigned to a second sensing position lying perpendicularly to the first sensing position about the rotational axis.

[0048] The evaluation unit 32 calculates the angular position α based on the first and second sensor signals S.sub.1, S.sub.2 via an atan2 function in an evaluation step 102. The respective first and second sensor signals S.sub.1, S.sub.2 are periodic signals superimposed with a possible harmonic error. In particular, the first sensor signal S.sub.1 is a cosine signal and the second sensor signal S.sub.2 is a sinusoidal signal.

[0049] A harmonic error of the first sensor signal S.sub.1 affecting the angular position α can be described by means of (1). Analogously, a harmonic error of the second sensor signal S.sub.2 affecting the angular position α can be described by means of (2).

[0050] First, the first and second sensor signal S.sub.1, S.sub.2 are amplified in the evaluation unit 32 in a processing step 104 and sensed via an A/D converter. The first and second sensor signals S.sub.1, S.sub.2 processed in this way are then normalized in a preparation step 106, i.e., a possible amplitude error and offset error in the first and second sensor signal S.sub.1, S.sub.2 is compensated for or reduced as much as possible. Furthermore, a possible orthogonal error is preferably already eliminated or reduced as far as possible.

[0051] The first and second sensor signals S.sub.1, S.sub.2 prepared in this way are then transferred to the evaluation step 102, which calculates the angular position α therefrom. The first and second sensor signals S.sub.1, S.sub.2 are transferred to a calculation step 108, which runs in parallel to the evaluation step 102. This can increase the calculation speed.

[0052] In the calculation step 108, an angular error ϵ characterizing the harmonic error is calculated based on the first and second sensor signals S.sub.1, S.sub.2, and is then output in a correction step 110 following the evaluation step 108. In the correction step 110, the angular position α* calculated by the evaluation step 102 is adjusted for the angular error ϵ and output as the angular position α.

[0053] The calculation of the angular error ϵ requires that the parameters of the error amplitude A.sub.f and error phase φ that describe the error signal are determined. For this purpose, the calculation step 108 comprises a parameter determination step 108.1, with which the error amplitude A.sub.f and the error phase φ of the respective error signal are calculated. This calculation may be carried out using the least squares method using the relationship (7) in conjunction with a gradient-based method according to (10), which is realized by means of a cost function of the optimization task illustrated in FIG. 6. The parameters defined in this way can then be translated back according to (5), and output in a subsequent angular error calculation step 108.2 assigned to the calculation step 108.

[0054] The angular error calculation step 108.2 determines the angular error ϵ depending on the parameters and during the operation of the sensor unit 12 by case-dependent application of the first calculation method according to (13) or the second calculation method according to (14), and transfers this to the correction step 110. The correction step 110 adjusts the angular position α* output for this calculated angular error ϵ through the evaluation step 102 by using the atan2 function. The calculated angular position α is then output by the evaluation unit 32.

[0055] FIG. 3 shows a comparison between a sensor signal with and without a harmonic error. FIG. 3a) shows a curve graph of an ideal sensor signal S.sub.0 and a sensor signal S superimposed by an error signal corresponding to a harmonic error. The values on the x-axis represent the first sensor signal S.sub.1 associated with the sensor signal S and the values on the y-axis represent the second sensor signal S.sub.2 associated with the sensor signal S.

[0056] The harmonic error acts as a deviation of the sensor signal S starting from a circular shape and causes the deviations from the actual angular position α.sub.0 of the determined angular position α shown in FIG. 3b).

[0057] FIG. 4 shows a curve graph and phase progression of a sensor signal influenced by a concurrent error signal. The concurrent error signal can be taken into account by means of the relationship (13). The error signal S.sub.f changes in the process concurrently with the sensor signal S*, and the indicators shown in FIG. 4a) thus rotate counterclockwise in a concurrent manner. The error signal S.sub.f changes with the angular error frequency kω, and the sensor signal S* with the rotational frequency ωt. The sensor signal having the harmonic error S has the angular error ϵ with respect to the sensor signal S*.

[0058] FIG. 4b) shows the phase progression of the respective signals over the angular position α.

[0059] FIG. 5 shows the respective illustrations corresponding to FIG. 4, but here with the difference that the error signal S.sub.f changes oppositely to the sensor signal S* and the indicators shown in FIG. 5a) thus rotate oppositely.

[0060] In FIG. 7, an angular error profile is shown depending on the harmonic error when using the method according to an exemplary embodiment of the disclosure. The maximum angular error {circumflex over (ϵ)} is proportional to the harmonic error F and with a very large harmonic error F of 15%, the maximum angular error {circumflex over (ϵ)} is still less than 0.7°. As a result, the angular position α is determined efficiently, accurately and quickly, and also during operation of the sensor unit 12, with the smallest possible angular error ϵ.

LIST OF REFERENCE SYMBOLS

[0061] 10 Clutch actuator

[0062] 12 Sensor unit

[0063] 14 Spindle

[0064] 16 Electric motor

[0065] 18 Rotor

[0066] 20 Planetary roller screw drive

[0067] 22 Rotational element

[0068] 24 Rotational component

[0069] 26 Magnetic ring

[0070] 28 Sensor element

[0071] 30 Circuit board

[0072] 32 Evaluation unit

[0073] 100 Method

[0074] 102 Evaluation step

[0075] 104 Processing step

[0076] 106 Preparation step

[0077] 108 Calculation step

[0078] 108.1 Parameter determination step

[0079] 108.2 Angular error calculation step

[0080] 110 Correction step

[0081] α Angular position

[0082] A Signal amplitude

[0083] A.sub.1 Signal amplitude

[0084] A.sub.2 Signal amplitude

[0085] A.sub.f Error amplitude

[0086] A.sub.f,1 Error amplitude

[0087] A.sub.f,2 Error amplitude

[0088] c.sub.2 Parameter

[0089] c.sub.3 Parameter

[0090] ϵ Angular error

[0091] {circumflex over (ϵ)} Maximum angular error

[0092] F Harmonic error

[0093] φ Error phase

[0094] φ.sub.1 Error phase

[0095] φ.sub.2 Error phase

[0096] ω Rotational frequency

[0097] nω Error frequency

[0098] S Sensor signal

[0099] S* Sensor signal

[0100] S.sub.1 First sensor signal

[0101] S.sub.2 Second sensor signal

[0102] S.sub.f Error signal

[0103] S.sub.f,1 Error signal

[0104] S.sub.f,2 Error signal