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.

Description

TECHNICAL FIELD

The disclosure relates to a method for detecting an angular position of a rotational component. Furthermore, the disclosure relates to a detection system and a clutch actuator.

BACKGROUND

A method for detecting an angular position of a rotational component is described, for example, in WO 2018/219388 A1. A method for detecting an angular position of a rotational component rotatable about a rotational axis is described therein, in which the angular position of the rotational component is picked up by a sensor system arranged radially at a distance from the rotational axis. A magnetic ring arranged fixedly and concentrically on the rotating component causes a magnetic field that changes relative to the sensor system and is detected by the sensor system, wherein a signal picked up by the sensor system is evaluated with regard to the angular position. The signal picked up by the sensor system is evaluated with regard to amplitude information of the magnetic field and a correction parameter is determined from the amplitude information, by means of which an angular error in the angular position picked up from the signal of the sensor system is determined. The angular error is then used to correct the angular position determined from the signal emitted by the sensor system.

SUMMARY

The disclosure provides an exemplary embodiment for detecting an angular position more accurately and more quickly. The influence of harmonic interference on the sensor signal should be sensed and reduced. As a result, a harmonic error in the sensor signal can be reduced quickly, efficiently, and during operation of a sensor unit. The angular position can be determined more accurately, more quickly, and with less calculation effort. The reliability of the sensor signal is increased.

The sensor unit and the rotational component can be arranged in a vehicle. The rotational component and the rotational element may be arranged to be concentrically rotatable. The sensor unit can be designed as an angle sensor.

The sensor element can be a Hall sensor.

The rotational element can be a magnetic ring. The rotational element can be a permanent magnet. The rotational element can be diametrically magnetized.

A first sensor signal can be a cosine signal, and a second sensor signal can be a sinusoidal signal.

A harmonic error affecting the angular position can be assumed as a periodic error signal superimposed on the sensor signal, using the example of the first sensor signal S₁* having the signal amplitude A₁ as follows

S ₁ =S ₁ *+S _f,1 =A ₁ cos (ωt)±A_f,1·cos(nωt+φ₁)   (1)

The error signal characterizing S_f,1 the harmonic error of the first sensor signal S₁ has the error amplitude A_f,1 and the error frequency nωt with the error phase φ₁. The error signal S_f,1 is superimposed on the actual first sensor signal S₁*.

The rotation of the rotational element triggering the first sensor signal S₁ and also the second sensor signal S₂ occurs at the rotational frequency ω.

It could be determined that the main part of the overall error signal characterizing the harmonic error is limited to the error frequency nω, while the remaining signal components of the error signal can be assumed to have less of an impact thereon. The error signal can therefore be assigned an error frequency, which is integrally dependent on the rotational frequency ω of the sensor signal. For example, it could be found that the harmonic error with the portion associated with the error frequency nω is more than 1% and the angular error of the angular position is less than 0.6°, if this portion of the harmonic error can be compensated.

Analogous to the previous example on the first sensor signal according to (1), a harmonic error of the second sensor signal S₂ affecting the angular position can be described as follows

S _s =S ₂ *+S _f,2 =A ₂ cos (ωt)±A_f,2·cos(nωt+φ₂)   (2)

The error signal S_f,2 characterizing the harmonic error of the second sensor signal S₂ has the error amplitude A_f,2 and the error frequency nω with the error phase φ₂.

An adjustment of the respective first and second sensor signal can be performed, for example, by taking into account the respective Fourier coefficient of the error signal according to (1) and (2). The Fourier coefficient can be determined before the sensor unit is put into operation, and stored, for example, in a lookup table that takes it into account for the respective sensor signal. A lookup table for the first sensor signal S₁ and a lookup table for the second sensor signal S₂ are created for the respective retrieval during operation of the sensor unit.

Alternatively, the Fourier coefficient can also be determined during operation of the sensor unit. In this way, the influences that change the Fourier coefficient, such as the temperature and time-dependent influences, can be taken into account and the accuracy of the Fourier coefficient can be increased. The disadvantage here, however, is the much higher calculation demand compared to the one-time determination of the Fourier coefficient using lookup tables before commissioning.

An exemplary embodiment for determining the Fourier coefficient during operation of the sensor unit is described below. In particular, this presupposes that the respective sensor signal has already been corrected with regard to a possible amplitude error, offset error and/or orthogonal error, so that the respective error has already been eliminated or reduced as far as possible.

The calculation of the parameters of the respective error signal S_f, preferably the error amplitude and/or the error phase, can be performed in a parameter determination step that takes place during operation of the sensor unit within the calculation step. The least squares method proves to be the most suitable and is carried out using the example of the first sensor signal S₁ by reducing the function K, which is given as follows

$\begin{array}{cc}K=\sum _{i=1}^n{\left[S_1\left(x_i\right)-y_i\right]}^2& \left(3\right)\end{array}$

with the values calculated at the respective positions x_i for the first sensor signal S₁ and the measured values corresponding to these positions y_i of the sensor element.

On the example of the first sensor signal S₁ with the sensing position x, (1) can be transformed, with the assumption of a normalized first sensor signal S₁ with A₁=1, according to

$\begin{array}{cc}\begin{array}{c}{S}_1\left(x\right)=\cos \left(x\right)+A_{f,1}·\left[\cos \left(\mathrm{nx}\right)·\cos \left({\phi }_1\right)-\sin \left(\mathrm{nx}\right)·\sin \left({\phi }_1\right)\right]\\ =\cos \left(x\right)+c_2·\cos \left(\mathrm{nx}\right)+c_3·\sin \left(\mathrm{nx}\right)\\ =\sum _{j=1}^3{c}_j{\varphi }_j\left(x\right)\end{array}& \left(4\right)\end{array}$ $\mathrm{which}\mathrm{gives}$ $$\begin{gathered} \begin{array}{cc}{c}_1=1\text{ \\ c2=Af,1·cos⁡(φ1)⁢ \\ c3=Af,1·sin⁡(φ1)}& \left(5\right)\end{array} \end{gathered}$$

By knowing the parameters c₂ and c₃, the parameters describing the error signal can be calculated.

The default according to (3) can be established through (4) by the following gradient equations

$\begin{array}{cc}\frac{\delta K}{\delta c_j}=0& \left(6\right)\end{array}$

The solution of (6) can be found as follows, assuming a linear combination of the parameters c_j

c=(ϕ^Tϕ)⁻¹ϕ^Ty   (7)

with

ϕ=ϕ_j(x_i)

y=(y₁, . . . , y_n)

c=(1, c₂, c₃)   (8)

The calculation of ϕ can be done via a QR decomposition.

The function matrix ϕ can be calculated using a gradient-based method, for example by the method of steepest descent, by the following iterative step

f(θ^(k+1))=f(θ^(k))+∇f(θ^(k))^T·^(k)·∇f(θ^(k))   (9)

with the step length and the step index k and

θ^(k)=(c₂^(k), c₃^(k))   (10)

The minimum can thus be calculated quickly via an optimization task, for example using a cost function.

By means of the calculated parameters c₂ and c₃, the error signal S_f,1 and analogously, for the second sensor signal, by means of the corresponding parameters, the error signal S_f,2 can be calculated and the respective sensor signal according to (1) and (2) can be corrected.

A further possibility of compensating for the influence of the respective error signal is described below, which requires a further reduced calculation effort.

The angular position α* calculated after the evaluation step by applying the atan2 function is adjusted for an angular error ϵ in a correction step. The angular error ϵ is calculated from the parameters of the respective error signal sensed in a parameter determination step in an angular error calculation step within a calculation step. The correction step then gives the calculated angular position α. An angular error calculation step can be between the parameter determination step and the correction step.

In the angular error calculation step, the maximum angular error {circumflex over (ϵ)} is calculated as follows

$\begin{array}{cc}\widehat{ϵ}=\arcsin \left(\frac{A_f}{A}\right)& \left(11\right)\end{array}$

with the error amplitude A_f calculated on the example of the first sensor signal S₁ via (10) and (5) as well as the signal amplitude A of the sensor signal.

If the error amplitudes A_f,1 and A_f,2 of the first and second sensor signals S₁, S₂ are different, they can be considered averaged as follows.

$\begin{array}{cc}\widehat{ϵ}=\arcsin \left(\frac{A_{f,1}+A_{f,2}}{2·A}\right)& \left(12\right)\end{array}$

The angular error ϵ can be calculated with the angular error frequency kω and the error phase φ in parallel with an evaluation step in the angular error calculation step, or also in the correction step, on the one hand by a first calculation method as follows

$\begin{array}{cc}ϵ\left(\omega t\right)=\mathrm{arc}\sin \left(\frac{A_{f,1}+A_{f,2}}{2·A}\right)·\sin \left[\left(k+1\right)·\omega t+\phi \right]& \left(13\right)\end{array}$

if the error signal changes concurrently with the sensor signal, or alternatively via a second calculation method as follows

$\begin{array}{cc}ϵ\left(\omega t\right)=\mathrm{arc}\sin \left(\frac{A_{f,1}+A_{f,2}}{2·A}\right)·\sin \left[\left(k-1\right)·\omega t+\phi \right]& \left(14\right)\end{array}$

if the error signal changes oppositely with the sensor signal.

The error phase can be calculated using the following relationship

$\begin{array}{cc}\phi =\mathrm{atan}2\left(\frac{c_{3,1}+c_{3,2}}{c_{2,1}+c_{2,2}}\right)& \left(15\right)\end{array}$

with the parameters c_2,1, c_3,1 specified according to (5) for the first sensor signal S₁ and the corresponding parameters c_2,2, c_3,2 for the second sensor signal S₂.

Furthermore, a detection system for detecting an angular position of a rotational component is achieved by a method having at least one of the features indicated above. The detection system comprises an evaluation unit and a sensor unit, which has a fixed sensor element and a rotational element rotatable relative thereto and jointly with the rotational component.

Furthermore, a clutch actuator for clutch actuation, having such a detection system is provided. The clutch actuator can actuate a clutch designed as an e-clutch in a vehicle. The clutch actuator can be a modular clutch actuator, or MCA for short. This can comprise a rotor and a spindle. The rotor can perform a rotational movement, which is converted into a linear movement of the spindle via a planetary roller screw drive, abbreviated PWG. The linear movement of the spindle can actuate the clutch.

Further advantages and advantageous embodiments of the disclosure result from the description of the figures and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

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

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

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

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.

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.

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.

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 S₁ dependent upon the angular position α and assigned to a first sensing position, and a second sensor signal S₂ assigned to a second sensing position lying perpendicularly to the first sensing position about the rotational axis.

The evaluation unit 32 calculates the angular position α based on the first and second sensor signals S₁, S₂ via an atan2 function in an evaluation step 102. The respective first and second sensor signals S₁, S₂ are periodic signals superimposed with a possible harmonic error. In particular, the first sensor signal S₁ is a cosine signal and the second sensor signal S₂ is a sinusoidal signal.

A harmonic error of the first sensor signal S₁ affecting the angular position α can be described by means of (1). Analogously, a harmonic error of the second sensor signal S₂ affecting the angular position α can be described by means of (2).

First, the first and second sensor signal S₁, S₂ 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 S₁, S₂ 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 S₁, S₂ is compensated for or reduced as much as possible. Furthermore, a possible orthogonal error is preferably already eliminated or reduced as far as possible.

The first and second sensor signals S₁, S₂ 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 S₁, S₂ are transferred to a calculation step 108, which runs in parallel to the evaluation step 102. This can increase the calculation speed.

In the calculation step 108, an angular error ϵ characterizing the harmonic error is calculated based on the first and second sensor signals S₁, S₂, 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.

The calculation of the angular error ϵ requires that the parameters of the error amplitude A_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_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.

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.

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 S₀ 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 S₁ associated with the sensor signal S and the values on the y-axis represent the second sensor signal S₂ associated with the sensor signal S.

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 α₀ of the determined angular position α shown in FIG. 3b).

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_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_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*.

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

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

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

10 Clutch actuator

12 Sensor unit

14 Spindle

16 Electric motor

18 Rotor

20 Planetary roller screw drive

22 Rotational element

24 Rotational component

26 Magnetic ring

28 Sensor element

30 Circuit board

32 Evaluation unit

100 Method

102 Evaluation step

104 Processing step

106 Preparation step

108 Calculation step

108.1 Parameter determination step

108.2 Angular error calculation step

110 Correction step

α Angular position

A Signal amplitude

A₁ Signal amplitude

A₂ Signal amplitude

A_f Error amplitude

A_f,1 Error amplitude

A_f,2 Error amplitude

c₂ Parameter

c₃ Parameter

ϵ Angular error

{circumflex over (ϵ)} Maximum angular error

F Harmonic error

φ Error phase

φ₁ Error phase

φ₂ Error phase

ω Rotational frequency

nω Error frequency

S Sensor signal

S* Sensor signal

S₁ First sensor signal

S₂ Second sensor signal

S_f Error signal

S_f,1 Error signal

S_f,2 Error signal

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; andupdating, 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; anddetermining 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; anda 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; andupdate 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; anda 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; anddetermine 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; anda 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.