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 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 orthogonal error is converted by the evaluation unit into an amplitude difference between respective amplitudes of the first and second sensor signals based on a coordinate transformation of the first and second sensor signals. Each of the first and second sensor signals are adjusted by the evaluation unit based on the amplitude difference. An angular position of a rotational component is determined by the evaluation unit based on output from an a tan 2-function that takes the adjusted first and second sensor signals as input.

Description

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 that can rotate about a rotational axis is described therein, in which the angular position of the rotational component is detected 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 output by the sensor system.

SUMMARY

The disclosure provides an exemplary embodiment for detecting an angular position more accurately and quickly. The angular error caused by the orthogonal error can be compensated for. This makes it easier and faster to detect the angular position with reduced angular error.

A sensor unit and the rotational component can be arranged in a vehicle. The rotational component and a rotary 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 and/or second sensor signal can be a periodic signal. The first sensor signal can be a cosine signal, and the second sensor signal can be a sinusoidal signal.

An orthogonal error between the first sensor signal S₁ and the second sensor signal S₂ affecting an angular position α can be described via an offset angle φ as follows

$\begin{array}{cc}\left[\begin{array}{c}{S}_1\\ S_2\end{array}\right]=\left[\begin{array}{c}\cos \left(\alpha \right)\\ \sin \left(\alpha +\phi \right)\end{array}\right]& \left(1\right)\end{array}$

Knowing the offset angle φ, a second sensor signal S**₂ adjusted for the orthogonal error could be calculated according to the following

$\begin{array}{cc}{S}_2^{**}=\frac{S_2}{\cos \left(\phi \right)}-S_1·\tan \left(\phi \right)& \left(2\right)\end{array}$

The calculation of the offset angle φ, which has to be determined in advance for this purpose, is computationally expensive, time-consuming and uneconomical to perform while the sensor unit is in operation using conventional methods.

Instead of determining the offset angle φ, an orthogonal error can be suitably transformed into an amplitude difference of the amplitudes a, b of the sensor signals in a correction step preceding an evaluation step via the following coordinate transformation of the first and second sensor signals S₁, S₂

$\begin{array}{cc}\left[\begin{array}{c}{S}_1\\ S_2\end{array}\right]=\left[\begin{array}{c}\cos \left(\alpha \right)\\ \sin \left(\alpha +\phi \right)\end{array}\right]=\left[\begin{array}{cc}\cos \left(\frac{\pi }{4}\right)& -\sin \left(\frac{\pi }{4}\right)\\ \sin \left(\frac{\pi }{4}\right)& \cos \left(\frac{\pi }{4}\right)\end{array}\right]·\left[\begin{array}{c}a·\cos \left(\alpha +{\alpha }_0\right)\\ b·\sin \left(\alpha +{\alpha }_0\right)\end{array}\right]& \left(3\right)\end{array}$

A phase shift α₀ of the two sensor signals can be taken into account in this regard.

The coordinate transformation can be performed in a conversion step associated with the correction step. Preferably, a coordinate rotation of 45° is performed during the coordinate transformation, corresponding to

$\frac{\pi }{4}$

with the rotation matrix

$\begin{array}{cc}{\left[\begin{array}{cc}\cos \left(\frac{\pi }{4}\right)& -\sin \left(\frac{\pi }{4}\right)\\ \sin \left(\frac{\pi }{4}\right)& \cos \left(\frac{\pi }{4}\right)\end{array}\right]}^{-1}=\frac{\sqrt{2}}{2}·\left[\begin{array}{cc}1& 1\\ -1& 1\end{array}\right]& \left(4\right)\end{array}$

whereby the coordinate rotation resulting in the converted first sensor signal S*₁ and the converted second sensor signal S*₂ can be calculated as follows

$\begin{array}{cc}\left[\begin{array}{c}{S}_1^{*}\\ S_2^{*}\end{array}\right]=\frac{\sqrt{2}}{2}·\left[\begin{array}{c}{S}_1+S_2\\ S_2-S_1\end{array}\right]=\left[\begin{array}{c}a·\cos \left(\alpha +{\alpha }_0\right)\\ b·\sin \left(\alpha +{\alpha }_0\right)\end{array}\right]& \left(5\right)\end{array}$

If the converted sensor signals S*₁, S*₂ are transferred as arguments to an a tan 2 function in a subsequent evaluation step for calculating the angular position α, the converted sensor signals S*₁, S*₂ can also be calculated while omitting the prefactor via a subtraction and addition of the first and second sensor signals S₁, S₂ as follows

$\begin{array}{cc}\left[\begin{array}{c}{S}_1^{*}\\ S_2^{*}\end{array}\right]=\left[\begin{array}{c}{S}_1+S_2\\ S_2-S_1\end{array}\right]& \left(6\right)\end{array}$

The conversion step can be preceded by a normalization step that performs an offset correction and/or an amplitude correction of the unprocessed first and second sensor signals S₁⁰, S₂⁰ output by the sensor unit and then transfers the corrected first and second sensor signals S₁, S₂ to the conversion step.

In a calculation step associated with the correction step and following the conversion step, the converted first and second sensor signals S*₁, S*₂ can be adjusted for the amplitude difference and transferred to the evaluation step as an adjusted first sensor signal S**₁ and as an adjusted second sensor signal S**₂. In this regard, the amplitude A*₁ of the converted first sensor signal S*₁ can be calculated according to

A* ₁=max(S*₁)−min(S*₁)  (7)

and the amplitude A*₂ of the converted second sensor signal S*₂ can be calculated according to

A* ₂=max(S*₂)−min(S*₂)  (8)

Then the amplitude difference γ can be calculated as follows

$\begin{array}{cc}\gamma =\frac{a}{b}=\frac{A_1^{*}}{A_2^{*}}& \left(9\right)\end{array}$

Subsequently, the amplitude difference can be compensated for by adjusting the amplitude of the converted second sensor S*₂ signal by applying

A** ₂ =A* ₂*γ  (10)

and the converted first and second sensor signals S*₁, S*₂ are transferred to the evaluation step as an adjusted first sensor signal S**₁ and an adjusted second sensor signal S**₂.

In the evaluation step, the angular position a can be calculated using an a tan 2 function with the adjusted first and second sensor signals S**₁, S**₂.

Here, the maximum angular error ∈*_max caused by the amplitude difference 7 is defined as follows

$\begin{array}{cc}{ϵ}_{\max }^{*}=\mathrm{arc}\sin \left[\frac{\gamma -1}{\gamma +1}\right]& \left(11\right)\end{array}$

The offset angle φ can be calculated with the amplitude difference γ by transforming (3) as follows

$\begin{array}{cc}\phi =2·\arctan \left(\frac{\gamma -1}{\gamma +1}\right)& \left(12\right)\end{array}$

Thus, the maximum angular error ∈_max caused by the orthogonal error corresponding to the offset angle φ can be calculated as follows

$\begin{array}{cc}{ϵ}_{\max }\left(\phi \right)=\arcsin \left[\tan \left(\frac{\phi }{2}\right)\right]+\frac{\phi }{2}& \left(13\right)\end{array}$

The evaluation step can comprise a phase correction step in which the common phase shift α₀ of the first and second sensor signals S₁, S₂ is calculated and the angular position α is adjusted for this phase shift α₀ and output. The phase shift α₀ can be determined as follows

$\begin{array}{cc}{\alpha }_0=-\mathrm{arc}\tan \left(\frac{1}{\gamma }\right)& \left(14\right)\end{array}$

and be taken into account as a phase correction α*₀ via the following relation

$\begin{array}{cc}{\alpha }_0^{*}=-{\alpha }_0+\phi =\mathrm{arc}\tan \left(\frac{1}{\gamma }\right)+2·\mathrm{arc}\tan \left(\frac{\gamma -1}{\gamma +1}\right)-\frac{\pi }{2}& \left(15\right)\end{array}$

The phase correction step may be performed after applying the a tan 2 function.

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 comprising 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 operate 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 include 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 motion of the spindle can actuate the clutch.

Further advantages and advantageous embodiments of the disclosure are apparent from the description of the figures as well as the figures themselves.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

FIG. 2: shows a respective course of the first and second sensor signal depending on the angular position.

FIG. 3a: shows a curve graph of the first and second sensor signals.

FIG. 3b: shows a curve graph of the respective converted first and second sensor signals.

FIG. 4: shows a sequence of a method in an exemplary embodiment of the disclosure.

FIG. 5: shows a respective curve graph of the sensor signals according to the individual steps of the method according to FIG. 4.

FIG. 6: shows a respective angular error curve of the sensor signals according to the individual steps of the method according to FIG. 4.

FIG. 7: shows a dependence of the maximum angular error on the orthogonal error when using the method in an exemplary embodiment of the disclosure.

DETAILED DESCRIPTION

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.

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 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 the magnetic ring 26 causes the magnetic field to change as a function of the angular position of the rotor 18.

FIG. 2 shows a respective curve of first and second sensor signals S₁, S₂ as a function of the angular position α. The first sensor signal S₁ and the second sensor signal S₂ are each a periodic signal. The first sensor signal S₁ is a cosine signal and the second sensor signal S₂ is a sinusoidal signal, but it has an orthogonal error with respect to the cosine signal expressed by the offset angle φ. However, an exact determination of the angular position α based on the first and second sensor signal S₁, S₂ using an a tan 2 function requires an orthogonality of both sensor signals S₁, S₂. If a deviation from this is not taken into account, the determined angular position α can be subject to an angular error depending on the orthogonal error.

FIG. 3a shows a curve graph of the first and second sensor signals S₁, S₂. The first sensor signal S₁ is plotted on the x-axis and the second sensor signal S₂ is plotted on the y-axis. If both sensor signals S₁, S₂ were ideally orthogonal to one another, a circular curve graph would be the result. Due to the orthogonal error, the curve graph corresponding to the first and second sensor signals S₁, S₂ deviates from this and can be described by an ellipse with a major axis extending along an angle of 45°.

An orthogonal error between the first sensor signal S₁ and the second sensor signal S₂ affecting the angular position α can be described by the offset angle φ according to (1). Knowing the offset angle φ, a second sensor signal S**₂ adjusted for the orthogonal error can be calculated according to (2). However, calculating the offset angle φ using conventional methods is time-consuming, involves high computing power and is uneconomical to perform while the sensor unit 12 is in operation.

Instead of determining the offset angle φ, the orthogonal error can be converted in a conversion step via a coordinate transformation of the first and second sensor signals S₁, S₂ into an amplitude difference of the amplitudes a, b of the sensor signals S₁, S₂ according to (3) and output as converted sensor signals S₁, S₂.

FIG. 3b shows a curve graph of the converted first and second sensor signals S*₁, S*₂. The coordinate transformation is achieved by a coordinate rotation of 45°, corresponding to the rotation matrix according to (4). This results in an ellipse rotated 45° to that of FIG. 3a. The amplitudes a, b of the converted sensor signals S*₁, S*₂ can thus be further evaluated by determining an amplitude difference according to (9).

FIG. 4 shows a sequence of a method 100 in an exemplary embodiment of the disclosure. The method 100 detects an angular position a of a rotational component 24 that can rotate about a rotational axis via a sensor unit 12, which outputs an unprocessed first sensor signal S₁⁰ dependent on the angular position α and associated with a first detection position as well as an unprocessed second sensor signal S₂⁰ associated with a second detection position lying about the rotational axis perpendicular to the first detection position to an evaluation unit 102.

The evaluation unit 102 calculates the angular position α from the unprocessed first and second sensor signals S₁⁰, S₂⁰ by means of several steps. FIG. 5 shows a respective curve graph of the sensor signals output after the individual steps of this method and FIG. 6 shows a respective angular error graph of the angular error E of the sensor signals output after the corresponding steps of this method. Unless otherwise stated, the following explanation refers to the method according to FIG. 4, but explicitly refers to FIG. 5 and FIG. 6 in places.

The unprocessed sensor signal Sa in FIG. 5 causes the angular error Ea shown in FIG. 6. The angular error fa reaches high values, which make the detection of the angular position a unreliable if it is not taken into account. The angular error a can be significantly reduced by the subsequent further steps of the method.

The unprocessed first and second sensor signals S₁⁰, S₂⁰ are first transferred to a normalization step 104, which performs an offset correction 104.1 and an amplitude correction 104.2 of the unprocessed first and second sensor signals S₁⁰, S₂⁰ and outputs them as first and second sensor signals S₁, S₂ respectively.

The corresponding sensor signal Sb after the normalization step 104 is shown in FIG. 5 and, with respect to FIG. 6, is subject to a reduced angular error ∈_b, the amplitude of which has been reduced by more than 50% compared to the amplitude of the angular error ∈_a.

The first and second sensor signals S₁, S₂ are output to a subsequent correction step 106, which includes a conversion step 108 and a subsequent calculation step 110. The first and second sensor signals S₁, S₂ are converted in the conversion step 108 by a coordinate transformation 108.1, and thereby the orthogonal error of the first and second sensor signals S₁, S₂ is converted into an amplitude difference of the amplitudes a, b of the sensor signals S₁, S₂ via the coordinate transformation according to (3). Here, a phase shift α₀ of the two sensor signals S₁, S₂ is also taken into account. The coordinate transformation 108.1 is achieved by a coordinate rotation of 45°, with the rotation matrix according to (4).

The corresponding sensor signal Sc in FIG. 5 is illustrated as an ellipse rotated by 45°. The resulting angular error ∈_c in FIG. 6 is offset by 45° from the angular error ∈_b.

The respective converted first and second sensor signals S*₁, S*₂ can be calculated from the first and second sensor signals S₁, S₂ via (5). Since the converted first and second sensor signals S*₁, S*₂ are transferred as arguments to an a tan 2 function in an evaluation step 112 following the correction step 106 for calculating the angular position α, the converted sensor signals S*₁, S*₂ can also be calculated while omitting the prefactor according to (6).

In a calculation step 110 associated with the correction step 106 and subsequent to the conversion step 108, an amplitude A*₁ of the converted first sensor signal S*₁ according to (7) and an amplitude A*₂ of the converted second sensor signal S*₂ according to (8) are taken into account. An amplitude difference γ is determined via (9) and used in the calculation step 110 to adjust the amplitude A*₂ of the converted second sensor signal S*₂ according to (10). The converted first and second sensor signals S*₁, S*₂ are subsequently transferred to the evaluation step 112 as an adjusted first sensor signal S**₁ and as an adjusted second sensor signal S**₂.

The adjusted sensor signal Sd in FIG. 5 corresponds to a circle. The associated angular error ∈_d shown in FIG. 6 is constant.

In the evaluation step 112, the angular position α* is calculated using an a tan 2 function with the adjusted first and second sensor signals S**₁, S**₂. The evaluation step 112 includes a phase correction step 114 in which the phase shift ac is compensated for by a phase correction α*₀ according to (15). The angular position α is then output for further processing.

The angular error ∈_D in FIG. 6 is reduced to the maximum extent.

FIG. 7 shows a dependence of the maximum angular error ∈_max on the orthogonal error when using the method in an exemplary embodiment of the disclosure. The orthogonal error is expressed by the offset angle φ. The maximum angular error ∈_max is the more proportional to the offset angle φ. The array of curves shows the influence of noise and harmonic distortions on the sensor signals.

The curve Ka corresponds to a sensor signal influenced by harmonic disturbances, the curve Kb to a sensor signal influenced by noise and the curve Kc to a sensor signal influenced by both disturbances. Even with an offset angle φ of 20°, the maximum angular error ∈_max can be kept low by utilizing this method.

LIST OF REFERENCE SYMBOLS

• 10 Clutch actuator
• 12 Sensor unit
• 14 Spindle
• 16 Electric motor
• 18 Rotor
• 20 Planetary screw drive
• 22 Rotary element
• 24 Rotary component
• 26 Magnetic ring
• 28 Sensor element
• 30 Board
• 100 Method
• 102 Evaluation unit
• 104 Normalization step
• 104.1 Phase correction
• 104.2 Amplitude correction
• 106 Correction step
• 108 Conversion step
• 108.1 Coordinate transformation
• 110 Calculation step
• 112 Evaluation step
• 114 Phase correction step
• α Angular position
• α₀ Phase shift
• α*₀ Phase correction
• ∈ Angular error
• ∈_max Maximum angular error
• γ Amplitude difference
• Ka Curve
• Kb Curve
• Kc Curve
• φ Offset angle
• S₁ First sensor signal
• S₂ Second sensor signal
• Sa Sensor signal
• Sb Sensor signal
• Sc Sensor signal
• Sd Sensor signal
• S₁⁰ Unprocessed first sensor signal
• S₂⁰ Unprocessed second sensor signal
• S*₁ Converted first sensor signal
• S*₂ Converted second sensor signal
• S**₁ Adjusted first sensor signal
• S**₂ Adjusted second sensor 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 signal is associated with a second detection position lying about the rotational axis perpendicular to the first detection position;converting, via the evaluation unit, an orthogonal error into an amplitude difference between respective amplitudes of the first and second sensor signals based on a coordinate transformation of the first and second sensor signals;adjusting, via the evaluation unit, each of the first and second sensor signals based on the amplitude difference; anddetermining, via the evaluation unit, the angular position based on output from an a tan 2-function that takes the adjusted first and second sensor signals as input.

2. The method according to claim 1, further comprising converting, via the evaluation unit, the first and second sensor signals based on the coordinate transformation.

3. The method according to claim 2, wherein each of the converted first and second signals are adjusted based on the amplitude difference.

4. The method according to claim 1, wherein the coordinate transformation comprises a coordinate rotation of 45°.

5. The method according to claim 4, wherein the coordinate transformation is performed as subtraction and addition of the first and second sensor signals, respectively.

6. The method according to claim 1, further comprising, prior to converting the orthogonal error, performing, via the evaluation unit, at least one of an offset correction or an amplitude correction of the first and second sensor signals.

7. The method according to claim 1, further comprising: determining, via the evaluation unit, a common phase shift of the first and second sensor signals; andadjusting, via the evaluation unit, the angular position based on the phase shift.

8. The method according to claim 7, wherein the phase shift is determined after applying the a tan 2 function.

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 detection position;wherein the evaluation unit is configured to: convert an orthogonal error into an amplitude difference between respective amplitudes of the first and second sensor signals based on a coordinate transformation of the first and second sensor signals;adjust each of the first and second signals based on the amplitude difference; anddetermine the angular position based on output from an a tan 2-function that takes the adjusted first and second sensor signals as input.

10. A clutch actuator for a clutch, having 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 convert the first and second sensor signals based on the coordinate transformation.

14. The detection system according to claim 13, wherein each of the converted first and second signals are adjusted based on the amplitude difference.

15. The detection system according to claim 9, wherein the coordinate transformation comprises a coordinate rotation of 45°.

16. The detection system according to claim 15, wherein the coordinate transformation is performed as subtraction and addition of the first and second sensor signals, respectively.

17. The detection system according to claim 9, wherein the evaluation unit is further configured to, prior to converting the orthogonal error, perform at least one of an offset correction or an amplitude correction of the first and second sensor signals.

18. The detection system according to claim 9, wherein the evaluation unit is further configured to: determine a common phase shift of the first and second sensor signals; andadjust the angular position based on the phase shift.

19. 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.

20. The detection system according to claim 19, wherein the sensor element is axially spaced from the rotational element.