ANGLE SENSOR AND METHOD FOR OPERATING AN ANGLE SENSOR

Abstract

Angle sensor (90), including: a first sensor element (91) which is configured to output a first sensor signal as a function of a magnetic field dependent on a rotation angle of a measured object at the location of the first sensor element (91); a second sensor element (92) configured to output a second sensor signal depending on the magnetic field at the location of the second sensor element (92), which depends on the rotation angle of the object being measured; and a processor (98) configured for a calibration mode of the angle sensor (90) different from an operating mode, in order to ensure at least one 360° rotation of the object being measured during the calibration mode to determine a first offset value of the first sensor signal; to determine a second offset value of the second sensor signal; to determine an amplitude correction value based on the signal amplitudes of the first and second sensor signals, and a non-volatile memory (100; 103) configured to store the first and second offset values ​​determined by the processor (98) during calibration mode and the amplitude correction value for an application in operating mode, wherein the processor (98) is configured to determine the rotation angle based on the first and second sensor signals, the first and second offset values ​​and / or the amplitude correction value during the operating mode of the angle sensor (90) with rotations of the measured object in a rotation angle range of less than 360°.

Description

Technical field

[0001] The present disclosure relates generally to angle sensors and in particular to calibrations of angle sensors at the end of a production line with so-called end-of-line (EoL) calibrations. background

[0002] One of the most important requirements for modern angle sensors is the accuracy and control of angular errors, taking into account mechanical misalignments. Some causes of mechanical misalignment include x- and y-displacement between the sensor elements and the magnet, air gap variation (z-displacement), various types of tilt (e.g., package or housing tilt), and / or magnetization tilt.

[0003] Horizontal alignment and system tilt (for example, between the package and the magnet) are typically the responsibility of the angle sensor manufacturer. Robust mechanical designs can now achieve good accuracy values ​​of approximately + / - 300 µm x- and y-displacement and a tilt of approximately 2°. However, only about 3° to 4° of magnetization tilt is usually guaranteed.

[0004] Currently, one solution to ensure a sufficient error budget over an entire service life, including mechanical stresses and temperature influences, is the application of end-of-life (EoL) calibration. This often involves the use of so-called multi-point calibration methods, in which deviations of an angle sensor's angle estimates from several known reference angles (scanning points) are detected and recorded, for example, in a lookup table (LUT). Correction values ​​for the angle estimates can then be derived from this data.

[0005] Multi-point calibration methods can, however, incur additional costs for both chip and system manufacturers. For example, enabling on-chip programming of sampling points requires a LUT with EEPROM (Electrically Erasable Programmable Read-Only Memory) and other associated functions. The more sampling points required, the greater the impact on chip area. Studies show that at least 32 sampling points are necessary for automotive applications to achieve acceptable angular accuracy using multi-point calibration methods. For a system manufacturer, correcting the angular error requires significant effort during end-of-line (EoL) testing and incurs additional costs, as this calibration process is time-consuming (360° rotation and comparison with a reference, calculation of sampling point corrections, and write commands to the chip to save the calibration settings).The more sampling points are programmed, the longer the programming time.

[0006] In-situ calibrations during the operation of angle sensors are described in US 2013 / 0 268 234 A1, DE 10 2015 117 763 A1, DE 10 2004 024 398 A1.

[0007] Therefore, one of the purposes of this disclosure is to compensate for mechanical misalignments in angle sensors through more efficient EoL calibrations. Summary

[0008] The problem is solved by devices and methods according to the independent claims. Advantageous further developments are the subject of the dependent claims.

[0009] According to a first aspect of the present disclosure, an angle sensor is provided. The angle sensor comprises a first sensor element configured to output a first sensor signal at the location of the first sensor element, depending on the magnetic field at the location of the first sensor element and dependent on the rotation angle of the object being measured. The angle sensor comprises a second sensor element configured to output a second sensor signal at the location of the second sensor element, also dependent on the rotation angle of the object being measured. A processor is provided, configured for a calibration mode of the angle sensor, to determine, for a rotation of the object being measured during the calibration mode, a first offset value of the first sensor signal, a second offset value of the second sensor signal, and an amplitude correction value based on the signal amplitudes of the first and second sensor signals.Furthermore, the processor is designed to store the first determined offset value, the second determined offset value, and the determined amplitude correction value for correcting a rotation angle estimate in an operating mode of the angle sensor.

[0010] The proposed angle sensor therefore includes an auto-calibration function that permanently stores amplitude and offset compensation parameters, thus enabling auto-calibration with a special calibration mode that can be performed as an end-of-line (EoL) calibration. The angle sensor can therefore be put into a dedicated calibration mode. The auto-calibration mode can be used during an EoL calibration instead of a multi-point calibration and is not intended for in-situ calibration during normal operation.

[0011] According to some embodiments, the angle sensor is designed to determine the first offset value, the second offset value, and the amplitude correction value for at least one full 360° rotation of the object being measured (e.g., a shaft) during calibration mode. At least one full 360° rotation of the object being measured during calibration mode can facilitate the determination of the respective minimum and maximum signal amplitudes of the first and second sensor signals. However, embodiments that require less than one 360° rotation of the object being measured during calibration mode are also conceivable. During the rotation of the object being measured during calibration mode, the minimum and maximum signal amplitudes of the first and second sensor signals should ideally be traversed.

[0012] According to some embodiments, the angle sensor further comprises non-volatile memory configured to store the first and second offset values ​​and the amplitude correction value determined by the processor during calibration mode for subsequent use in (normal) operating mode. In some embodiments, the angle sensor can be integrated on a semiconductor chip, and the chip can include non-volatile memory for the first and second offset values ​​and the amplitude correction value. Examples of non-volatile semiconductor memory include EPROM and flash memory. Thus, during normal operation in operating mode, a rotation angle estimation can be performed based on currently measured sensor signals and the compensation values ​​determined and stored during calibration mode.

[0013] According to some embodiments, the first and second sensor elements are each designed as magnetic field sensors. Examples of magnetic field sensors include Hall effect sensors (lateral or vertical Hall effect sensors) or magnetoresistive (XMR) sensors. Embodiments are also conceivable in which the first and second sensor elements are each designed as inductive sensors. The basic principle of inductive sensors is a change in inductance or its quality factor due to a change in position relative to a conductive and / or ferromagnetic part.

[0014] According to some embodiments, the first and second sensor elements are designed to output sensor signals that are essentially phase-shifted by 90° in response to the magnetic field at the location of the respective sensor element, which depends on the rotation angle of the object being measured. It will be obvious to those skilled in the art that sensor signals phase-shifted by exactly 90° are the ideal case, which is never fully achieved in practice due to manufacturing tolerances and the associated mechanical misalignments.

[0015] To obtain sensor signals that are essentially 90° phase-shifted, some embodiments allow the first sensor element to be sensitive to a first directional component (e.g., x-direction) of the magnetic field, and the second sensor element to be sensitive to a second directional component (e.g., y-direction) of the magnetic field, with the second directional component being perpendicular to the first. Such embodiments can be implemented, for example, using XMR sensor elements (e.g., GMR, TMR, AMR). Other embodiments allow both the first and second sensor elements to be sensitive to the same directional component (e.g., z-direction) of the magnetic field. The 90° phase shift between the first and second sensor signals can then be adjusted by the respective placement of the first and second sensor elements.

[0016] Without mechanical misalignments between the sensor elements and the object being measured, the first and second sensor signals would ideally each have a mean value of zero for a 360° rotation of the object during calibration mode. However, any existing mechanical misalignments result in a mean value that is not zero. Therefore, the first and second offset values ​​indicate the actual mean deviation from zero. Furthermore, without mechanical misalignments, the first and second sensor signals would ideally have identical signal amplitudes. However, any existing mechanical misalignments result in unequal signal amplitudes for the two sensor signals. According to some embodiments, the amplitude correction value corresponds to a ratio of the signal amplitudes of the first and second sensor signals.In the following, signal amplitude is understood to be the difference between the minimum and maximum of the respective sensor signal.

[0017] According to some embodiments, the processor is designed to determine, during an operating mode of the angle sensor (after the initial calibration mode), a rotation angle AE for rotations of the measured object in a rotation angle range of less than 360° based on the first and second sensor signals, the first and second offset values ​​and / or the amplitude correction value.

[0018] According to some embodiments, the processor is configured to calculate the rotation angle AE based on AE=atan(ADC1−Off1;[ADC2−Off2]*mm) to determine, where ADC1 is the first (digitized) sensor signal, ADC2 the second (digitized) sensor signal, Off1 the first offset value, Off2 the second offset value, and mm the amplitude correction value. For example, Offx (x = 1, 2) Offx=1 / 2(ADCx_max+ADCx_min) and mm for example mm=ADC1max−ADC1_minADC2max−ADC2_min are equivalent to.

[0019] According to some embodiments, the processor is configured to determine, during the calibration mode of the angle sensor for predetermined reference rotation angles (scanning points) of a multi-point calibration procedure, a rotation angle estimate of the measured object based on the first and second sensor signals, the first and second offset values, and / or the amplitude correction value, and to store the difference between the respective rotation angle estimate and the reference rotation angle as an angle correction value. The proposed end-of-line (EoL) autocalibration can therefore optionally be combined with multi-point calibration to further increase estimation accuracy.Accordingly, the processor can be configured to determine, during the normal operating mode of the angle sensor, for rotations of the measured object in a rotation angle range of less than 360°, a first rotation angle estimate based on the first and second sensor signals, the first and second offset values ​​and / or the amplitude correction value, and a second rotation angle estimate based on the first rotation angle estimate and at least one angle correction value of the multi-point calibration.

[0020] According to a further aspect of the present disclosure, a method for operating an angle sensor is proposed. The method comprises outputting a first sensor signal from a first sensor element as a function of a magnetic field at the location of the first sensor element, which depends on the rotation angle of a measured object, and outputting a second sensor signal from a second sensor element as a function of the magnetic field at the location of the second sensor element, which also depends on the rotation angle of the measured object. During a calibration mode of the angle sensor, a rotation of the measured object is performed, and a first offset value of the first sensor signal, a second offset value of the second sensor signal, and an amplitude correction value based on the signal amplitudes of the first and second sensor signals are determined.In calibration mode, the first and second offset values ​​and the amplitude correction value are stored for later application in an operating mode of the angle sensor.

[0021] For end-of-line (EoL) calibration, the device can be switched to calibration mode. In calibration mode, measurements are taken to determine the offset values ​​and the amplitude correction value. The determined values ​​can be stored in non-volatile memory. Calibration mode can be performed, for example, once after installing the angle sensor in a mounting environment. After calibration, the angle sensor can be operated in normal mode.

[0022] According to some embodiments, during calibration mode, the first offset value, the second offset value, and the amplitude correction value are determined for at least one 360° rotation of the object being measured. At least one full 360° rotation of the object being measured during calibration mode can facilitate the determination of the respective minimum and maximum signal amplitudes of the first and second sensor signals.

[0023] According to some embodiments, the method further comprises an operating mode of the angle sensor downstream of the calibration mode, in which rotations of the object being measured are performed by less than 360°. In this operating mode, a rotation angle estimate is determined based on the first and second sensor signals, the stored first and second offset values, and the stored amplitude correction value.

[0024] After calibration mode, the system can be switched to normal operating mode. The offset values ​​and amplitude correction values ​​determined in calibration mode can then be applied to the measured sensor signals to obtain a corrected rotation angle estimate.

[0025] According to some embodiments, during calibration mode for predetermined reference rotation angles (scanning points), a rotation angle estimate of the measured object can be determined based on the first and second sensor signals, the first and second offset values, and the amplitude correction value. Additionally, the difference between the respective rotation angle estimate and the reference rotation angle can be stored as an angle correction value. The proposed end-of-line (EoL) autocalibration can therefore also be combined with multi-point calibration for predetermined reference rotation angles to further increase estimation accuracy.Accordingly, during the operating mode of the angle sensor, for rotations of the measured object in a rotation angle range of less than 360°, a first rotation angle estimate can be determined based on the first and second sensor signals, the stored first and second offset values ​​and / or the stored amplitude correction value, and a second rotation angle estimate can be determined based on the first rotation angle estimate and at least one stored angle correction value.

[0026] Exemplary embodiments of the present disclosure relate to a one-time application of an autocalibration function, preferably with full rotation of the object being measured. This enables simple amplitude and offset correction during a typical end-of-line (EoL) calibration without an external reference. Furthermore, it can accelerate the calibration / initial programming process on a system manufacturer's production line. The function itself is easy to implement and, in combination with multi-point calibration functions, can even improve angular performance or offer the potential to eliminate the need for multi-point calibration functions, thus saving chip area. Character description

[0027] Some examples of devices and / or methods are explained in more detail below with reference to the accompanying figures. These show: Fig. 1A an angular error distribution for a differential angle sensor with a reading radius of 1mm at an air gap of 1.7mm and room temperature conditions in front of a typical target magnet with a diameter of 6mm and perfect magnet inclination close to 0°; Fig. 1B an angular error distribution of a typical measurement in front of the reference magnet with off-center alignment; Fig. 2A ADC output signals of a typical measurement in front of the reference magnet with near-ideal centering and thus a nearly perfectly calculated angular linearity; Fig. 2B ADC output signals of a typical measurement in front of the reference magnet with a significant deviation from the center alignment and a resulting angular nonlinearity; Fig. 3A, B Angle error comparison for center alignment and corner alignment; Fig. 4 a flowchart of a method for operating an angle sensor according to an embodiment; Fig. 5 a block diagram of an EoL autocalibration according to an exemplary embodiment; Fig. 6A, B a comparison of angular errors without and with EoL autocalibration; Fig. 7 a block diagram of an EoL autocalibration according to a further embodiment; Fig. 8A, B Block diagrams of calibration mode and operating mode according to exemplary embodiments; and Fig. 9 a block diagram of an angle sensor IC according to an exemplary embodiment. Description

[0028] Several examples will now be described in more detail with reference to the accompanying figures, which illustrate some of these examples. The thickness of lines, layers, and / or areas may be exaggerated in the figures for clarity.

[0029] While further examples of various modifications and alternative forms are suitable, some specific examples are accordingly shown in the figures and are described in detail below. However, this detailed description does not limit further examples to the specific forms described. Further examples may encompass all modifications, correspondences, and alternatives that fall within the scope of revelation. Equal or similar reference signs throughout the description of the figures refer to identical or similar elements that, upon comparison, may be implemented identically or in a modified form while providing the same or a similar function.

[0030] It is understood that when an element is described as "connected" or "coupled" to another element, the elements may be connected or coupled directly or via one or more intermediate elements. When two elements A and B are combined using "or," this is to be understood as revealing all possible combinations, i.e., only A, only B, and A and B, unless explicitly or implicitly defined otherwise. An alternative formulation for the same combinations is "at least one of A and B" or "A and / or B." The same applies, mutatis mutandis, to combinations of more than two elements.

[0031] The terminology used here to describe certain examples is not intended to be limiting for other examples. Where a singular form, e.g., "a" and "the," "a," "a," is used, and the use of only a single element is neither explicitly nor implicitly defined as mandatory, further examples may also use plural elements to implement the same function. Similarly, where a function is subsequently described as being implemented using multiple elements, further examples may implement the same function using a single element or a single processing entity.It is further understood that the terms “include”, “comprehensive”, “exhibit” and / or “exhibit” when used specify the presence of the indicated features, integers, steps, operations, processes, elements, components and / or a group thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, processes, elements, components and / or a group thereof.

[0032] Unless otherwise defined, all terms (including technical and scientific terms) are used herein in their usual sense within the field to which examples belong.

[0033] As mentioned at the beginning, possible causes for mechanical misalignment include x- and y-displacements between sensor elements and magnet, air gap variation (z-displacement), inclination of various types (for example, package or housing inclination) and / or magnetization inclination.

[0034] This shows Fig. 1A an example of an angular error distribution along an x- and y-displacement. Fig. Figure 1A shows an example of relatively good sensor-magnet alignment. This is evident from the local minimum of the angular error near the (0 / 0) position and peak error values ​​at corresponding corners (0.8 / 0.8) or (-0.8 / -0.8). Such results can be achieved, for example, with additional support from optical alignment devices and multiple measurements on a dedicated laboratory test bench. However, such perfect alignment is generally not possible at the installation site of a system with an angle sensor and a measured object.

[0035] Fig. Figure 1B shows an angular error distribution of a typical measurement in front of a reference magnet with off-center alignment. The in Fig. The results shown in Figure 1B represent a known problem for gradient-based angle sensors. The use of gradient-based angle sensors, i.e., differential angle sensors, can offer robustness in a stray field. A differential sensor design allows for the compensation of homogeneous stray fields, but on the other hand, it makes the sensor more sensitive to mechanical misalignments.

[0036] Fig. Figure 2A (left) shows the signal waveform of the analog-to-digital converter (ADC) output signals of a differential angle sensor with x and y channels for a typical measurement in front of a reference magnet with near-ideal centering. The signal amplitudes of the differential x and y signals are nearly identical, and the phase shift between the differential x and y signals is nearly 90°. This results in a nearly perfect calculated angular linearity (right).

[0037] In contrast, the Fig. 2B (left) ADC output signals from a typical measurement in front of a reference magnet with a significant deviation from the center alignment (x-shift = 1.2 mm and y-shift = -1.2 mm). This misalignment results in a significant signal amplitude mismatch, so that the resulting angular nonlinearity for a calculated angle comparison is clearly visible in the figure on the right.

[0038] The Fig. 3A and Fig. Figure 3B shows an angular error comparison for the center alignment (0 / 0) ( Fig. 3A) with the corner orientation (1.2 / -1.2) ( Fig. 3B). Note the different y-axis scales, with a maximum angular error (AE) of less than 0.6° for center alignment and more than a factor of 10 larger errors for the misaligned example. This illustrates the need to compensate for such types of errors. Typically, so-called end-of-line (EoL) multi-point calibrations are used for this purpose. In this process, an (error-prone) angle estimate is performed for each of several known reference rotation angles or sampling points. The difference between the respective angle estimate and the reference rotation angle can be stored as an angle correction value. As mentioned earlier, multi-point calibration methods can incur additional costs for both chip manufacturers and system manufacturers.

[0039] Therefore, the present disclosure proposes to compensate for mechanical misalignments by means of an integrated auto-calibration, which, thanks to on-chip parameter storage, can first be performed in an EoL calibration mode and then applied in normal operation.

[0040] This shows Fig. Figure 4 shows a flowchart of a method 40 for operating a differential angle sensor according to an embodiment of the present disclosure. The method 40 relates to an end-of-line (EoL) calibration mode of the angle sensor, during which a rotation of the object being measured is performed. The rotation is preferably, but not necessarily, at least one full 360° rotation of the object being measured, such as a shaft, a wheel, or another angle encoder.

[0041] First, at 41, a first sensor signal is output by a first sensor element as a function of a magnetic field at the location of the first sensor element, which depends on the rotation angle of a measured object. At 42, a second sensor signal is output by a second sensor element as a function of the magnetic field at the location of the second sensor element, which depends on the rotation angle of the measured object. The two sensor elements can be components of a differential angle sensor. For example, the sensor elements can be Hall effect sensors or XMR sensors. Particularly with Hall effect sensors, a 90° phase shift between the first and second sensor signals can be achieved by positioning the two sensor elements differently. This makes such arrangements particularly susceptible to mechanical misalignment.

[0042] During calibration mode, a first offset value of the first sensor signal is determined at 43. The offset value here refers to a deviation from an ideal mean value of zero. According to some embodiments, the first offset value can be determined according to Off1=1 / 2(ADC1_max+ADC1_min) The values ​​are determined where ADC1_max represents the maximum value of the first sensor signal during rotation and ADC1_min represents the minimum value of the first sensor signal during rotation. Ideally, i.e., with no mechanical misalignment, the first offset value Off1 would be zero. In practice, however, a non-zero value can be expected.

[0043] During calibration mode, a second offset value of the second sensor signal is also determined at 44. According to some embodiments, the second offset value can be... Off2=1 / 2(ADC2_max+ADC2_min) The values ​​are determined where ADC2_max represents the maximum value of the second sensor signal during rotation and ADC2_min represents the minimum value of the second sensor signal during rotation. Ideally, i.e., with no mechanical misalignment, the second offset value Off1 would be zero. In practice, however, a non-zero value can be expected.

[0044] During calibration mode, a gain or amplitude correction value is also determined at 45 based on the signal amplitudes of the first and second sensor signals. According to some embodiments, the amplitude correction value can be... mm=ADC1_max−ADC1_minADC2_max−ADC2_min The values ​​are determined where (ADC1_max - ADC1_min) represents the difference between the minimum and maximum of the first sensor signal, i.e., its signal amplitude, and (ADC2_max - ADC2_min) represents the difference between the minimum and maximum of the second sensor signal, i.e., its signal amplitude. It is clear that, for example, the reciprocal of the above fraction could also be used as the amplitude correction value.

[0045] During calibration mode, the first offset value Off1, the second offset value Off2, and the amplitude correction value mm are saved for later use in normal operation. Alternatively, the sample values ​​ADC1_max, ADC1_min, ADC2_max, and ADC2_min could also be saved for later use in normal operation after end-of-life calibration.

[0046] The normal operating mode of the angle sensor is in Fig. 4 at 50 is indicated. In normal operating mode 50, rotations of the measured object that may be less than 360° can be performed, for example, over an angular range of only 90°, 120°, or 180°. In normal operating mode, a corrected (rotational) angle estimate AE can be determined based on the measured first and second sensor signals ADC1, ADC2, the stored first and second offset values ​​Off1, Off2, and the stored amplitude correction value mm. According to some embodiments, the corrected angle AE in normal operating mode can be determined according to AE=atan(ADC1−Off1;[ADC2−Off2]*mm) can be estimated, where atan(.,.) is an arctangent operation which can be implemented, for example, using the CORDIC algorithm (Coordinate Rotation Digital Computer).

[0047] Under normal operating conditions, i.e., in normal operating mode, the angle sensor can read the compensation parameters Off1, Off2, and mm from non-volatile memory and apply them to the currently measured samples ADC1 and ADC2 of the first and second sensor signals to obtain a corrected angle estimate. Although the autocalibration step is performed over at least one full rotation (360°) in normal operation, rotations of less than 360° can also be compensated. Typical angle ranges for chassis applications, for example, are rotations of 90°, 120°, or 180° in normal operation.

[0048] Exemplary implementations propose an auto-calibration function that permanently stores gain and offset compensation parameters, thus enabling auto-calibration with a special calibration mode that can be performed as an end-of-line (EoL) calibration. On-chip calibration without an external reference is possible. Only a rotation of the object being measured is required, which provides the maximum and minimum values ​​of the sensor signals. In any case, this can be achieved with a 360° rotation of the object being measured or the angle encoder. Compared to multi-point calibrations, a significant acceleration of the calibration process can be achieved. Furthermore, less memory space may be sufficient, as only three or four compensation values ​​need to be stored non-volatilely.

[0049] A block diagram of an angle correction based on the described EoL autocalibration can be presented as shown in Fig. 5 will be shown.

[0050] At 51, the raw data received from ADC1 of the first sensor element (e.g., x-channel) can be compensated at 53, for example, according to x = (ADC1 - Off1). At 52, the raw data received from ADC2 of the second sensor element (e.g., y-channel) can be compensated at 54, for example, according to y = [ADC2 - Off2] * mm. The compensation values ​​Off1, Off2, mm can be read from a non-volatile on-chip memory 55. At 56, the angle estimation takes place according to AE = atan(x; y). A compensated first-order angle estimate is then output at 57.

[0051] The performance of the proposed concept can be assessed by comparing the Fig. 6A and Fig. be assessed as 6B. Fig. Figure 6A shows a typical sensor-magnet alignment for a chassis application as the initial situation. The minimum angular error AE is 0.39°, and the maximum angular error for the entire scan matrix (within a + / -0.75 mm grid in the x and y directions) is 4.31°. The in Fig. The results shown in Figure 6B are based on the same raw sensor data, but with autocalibration according to an exemplary implementation. The minimum angular error AE is reduced from 0.39° to 0.28°, while the maximum angular error AE is also significantly reduced from 4.31° to 2.04°. It can be seen that the improvement factor varies with the actual position of the sensor relative to the magnet. Overall, however, a significant improvement can be achieved compared to an estimate based solely on the raw signal data.

[0052] The described end-of-line (EoL) autocalibration can, according to some implementations, also be combined with an additional multi-point calibration. This is illustrated in the schematic block diagram of the Fig. 7 explained.

[0053] The in Fig. The concept shown in section 7 differs from Fig. 5. This is achieved by the fact that, after the first-order angle estimation at 56, there is a further second-order angle correction that can further improve the first-order angle estimate using additionally stored multi-point calibration data. A first rotation angle estimation at 56 is therefore based, as in Fig. 5 on the first and second raw sensor signals 51, 52, the first and second offset values ​​Off1, Off2, and the amplitude correction value mm, which can be read from memory 75. A second rotation angle estimate at 77 is based on the first rotation angle estimate 56 and at least one stored angle correction value from a multi-point calibration performed during calibration mode. A stored angle correction value can correspond to a difference between a known reference rotation angle (sampling point) and the first rotation angle estimate at 56 determined during calibration mode. An angle correction value can be stored for each reference rotation angle targeted during calibration mode.For example, during calibration mode, for a known reference rotation angle of 10°, the first-order angle estimate at position 66 might have yielded an estimate of 9.6°, resulting in an angle correction value of +0.4° that can be applied for a predetermined angle range around 10°. If, during normal operation, the first-order angle estimate at position 56 yields an estimate of 11.2°, for example, this value can be corrected to 11.6° using the angle correction value of +0.4° in the second-order angle correction at position 77.

[0054] To improve accuracy, interpolation can be performed between adjacent angle correction values ​​to obtain a correction value that matches the first rotation angle estimate at 56. For example, if an angle correction value of -0.4° was determined during calibration mode for a reference rotation angle of 20°, first-order angle estimates at 56 between 10° and 20° can be interpolated between the corresponding angle correction values ​​of +0.4 and -0.4. If, for example, the first-order angle estimate at 56 yields an estimate of 14° during normal operation, this value can be corrected to 14.08° using an interpolated angle correction value of (0.6 * 0.4° - 0.4 * 0.4°) = 0.08° during the second-order angle correction at 77.

[0055] For this purpose, during the calibration mode of the angle sensor, a rotation angle estimate of the measured object can be determined beforehand for predetermined (i.e. known) reference rotation angles (sample values) based on the first and second sensor signals ADC1, ADC2, the first and second offset values ​​Off1, Off2 and the amplitude correction value mm, and a difference between the respective rotation angle estimate and the reference rotation angle can be stored as an angle correction value.

[0056] In principle, a device according to the proposed concept offers a dedicated calibration state, accessible during a dedicated calibration operating mode. This calibration operating mode includes determining the compensation parameters Off1, Off2, and mm required for first-order angle estimation. This is not intended as in-situ calibration during normal operation. Once the device is operational, a calibration state can be activated. Optionally, a multi-point calibration for second-order angle estimation can also be performed. A possible procedure is described in Fig. 8A shown.

[0057] The procedure requires an end-of-line calibration capability at the system integrator. Once the calibration state has been activated at step 81, a 360° rotation of a target shaft can be performed at step 82. After the full rotation, the compensation parameters Off1, Off2, and mm can be calculated without an external ideal reference. If an external ideal reference is available, additional linearization concepts (e.g., multi-point calibration) can be applied at step 83. A final step at step 84 is the storage of the compensation parameters Off1, Off2, and mm in the LUT (Linear Utilization Table).

[0058] Under normal operating conditions (see Fig. 8B) the device can read the compensation parameters Off1, Off2 and mm from the LUT at 85 and perform first-order autocompensation and, if necessary, additionally second-order multipoint compensation at 86.

[0059] Since both auto-calibration and, if necessary, multi-point calibration are available, a flexible compensation concept can be offered with examples depending on the actual accuracy requirements.

[0060] Fig. Figure 9 shows a possible chip architecture of an angle sensor 90 according to an exemplary embodiment as a block diagram.

[0061] The chip comprises an analog section A and a digital section D. Analog section A includes a first differential reverb plate 91 (x-channel) and an ADC 93 connected downstream of the reverb plate 91. Analog section A further includes a second differential reverb plate 92 (x-channel) and an ADC 94 connected downstream of the reverb plate 92. Digital section D comprises a digital filter 95 coupled to the output of the ADC 93 and a digital filter 96 coupled to the output of the ADC 94. The digital filters 95 and 96 can apply the compensation parameters Off1, Off2, and mm, stored via EEPROM 103 and LUT 100, to the x-channel and y-channel signals to obtain a first-order angle estimate in an angle estimator 98. This first-order angle estimate can then be further processed by the angle estimator 98 with additional multi-point angle correction values ​​from the LUT 100 to obtain a second-order angle estimate.The angle processor 98 can perform angle calculations using a hardware- and / or software-based atan2 (or CORDIC) angle calculation. The estimated angle values ​​can then be transmitted via an interface 101 (e.g., PSI5, PWM, SENT / SPC, UART) to one or more external processors or control units.

[0062] Some advantages of the proposed end-of-line (EoL) autocalibration, where compensation parameters are permanently stored in a LUT, include the elimination of the need for an external reference. Without an external reference, only a 360° rotation of the object being measured is required; a high-precision angular resolution encoder is unnecessary. Calibration can be performed more quickly because no external post-processing (e.g., comparison with a linear reference, calculation of sampling points) is required. Furthermore, significantly fewer compensation parameters need to be stored compared to multi-point calibration. Increased automation can also be achieved.

[0063] The proposed end-of-line (EoL) autocalibration can be used for sub-360° applications. For example, the sensor can be directly mounted to the magnet, and on-chip calibration can be initiated for a 180° angular range. Autocalibration functions as long as a maximum and minimum value for x and y, or sine and cosine, can be identified. The proposed concept is not limited to gain and offset compensation; in principle, all types of autocalibration can be applied, depending on the computational capabilities of the chip's digital components. For instance, this function can be implemented with a more complex chip-by-chip approach, where a powerful microcontroller is equipped with additional functions such as DFT analysis or other more complex mathematical capabilities, and the results can be stored in the LUT.With a chip equipped with a charging pump, the user can start the calibration mode and program the device itself after a 360° rotation.

[0064] The aspects and features described together with one or more of the previously detailed examples and figures can also be combined with one or more of the other examples to replace an identical feature of the other example or to additionally introduce the feature into the other example.

[0065] Examples may also include a computer program with program code for performing one or more of the above procedures, or refer to the execution of the computer program on a computer or processor. Steps, operations, or processes of various procedures described above may be performed by programmed computers or processors. Examples may also include program storage devices, such as digital data storage media, that are machine-, processor-, or computer-readable and encode machine-executable, processor-executable, or computer-executable programs of instructions. The instructions perform or cause some or all of the steps of the procedures described above. The program storage devices may, for example,Digital storage media, magnetic storage media such as magnetic disks and magnetic tapes, hard disk drives, or optically readable digital data storage media. Further examples may also include computers, processors, or control units programmed to perform the steps of the procedures described above, or (field) programmable logic arrays (PLAs) or (field) programmable gate arrays (PGAs) programmed to perform the steps of the procedures described above.

[0066] The descriptions and drawings only illustrate the principles of revelation. Furthermore, all examples presented here are expressly intended for illustrative purposes only, to assist the reader in understanding the principles of revelation and the concepts contributed by the inventor(s) to the advancement of technology. All statements made here regarding principles, aspects, and examples of revelation, as well as specific examples thereof, include their corresponding references.

[0067] A functional block designated as a "means for..." performing a specific function can refer to a circuit configured to perform that function. Thus, a "means for something" can be implemented as a "means configured for or suitable for something," e.g., a component or circuit configured for or suitable for the specific task.

[0068] The functions of various elements shown in the figures, including each functional block designated as "means," "means of providing a signal," "means of generating a signal," etc., can be implemented in the form of dedicated hardware, e.g., "a signal provider," "a signal processing unit," "a processor," "a controller," etc., as well as in hardware capable of executing software in conjunction with associated software. When provided by a processor, the functions can be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some or all of which can be shared.However, the term "processor" or "controller" is by no means limited to hardware capable solely of executing software, but can include digital signal processor hardware (DSP hardware; DSP = Digital Signal Processor), network processors, application-specific integrated circuits (ASICs = Application Specific Integrated Circuits), field-programmable gate arrays (FPGAs = Field Programmable Gate Arrays), read-only memory (ROMs = Read Only Memory) for storing software, random-access memory (RAMs = Random Access Memory), and non-volatile storage devices. Other hardware, both conventional and / or custom-designed, may also be included.

[0069] A block diagram, for example, can represent a rough circuit diagram that implements the principles of the disclosure. Similarly, a flowchart, a process flowchart, a state transition diagram, pseudocode, and the like can represent various processes, operations, or steps that are, for example, substantially depicted in a computer-readable medium and thus executed by a computer or processor, regardless of whether such a computer or processor is explicitly shown. Methods disclosed in the description or in the claims can be implemented by a component that includes means for performing each of the respective steps of these methods.

[0070] It is understood that the disclosure of multiple steps, processes, operations, or functions in the description or claims should not be interpreted as being in a specific order unless explicitly or implicitly stated otherwise, for example, for technical reasons. Therefore, the disclosure of multiple steps or functions does not restrict them to a specific order unless these steps or functions are not interchangeable for technical reasons. Furthermore, in some examples, a single step, function, process, or operation may include and / or be broken down into multiple sub-steps, sub-functions, sub-processes, or sub-operations. Such sub-steps may be included and form part of the disclosure of that single step unless explicitly excluded.

Claims

[1] Angle sensor (90), comprising: a first sensor element (91) which is configured to output a first sensor signal as a function of a magnetic field dependent on a rotation angle of a measured object at the location of the first sensor element (91); a second sensor element (92) configured to output a second sensor signal depending on the magnetic field at the location of the second sensor element (92), which depends on the rotation angle of the object being measured; and a processor (98) configured for a calibration mode of the angle sensor (90) different from an operating mode, in order to ensure at least one 360° rotation of the object being measured during the calibration mode to determine a first offset value of the first sensor signal; to determine a second offset value of the second sensor signal; to determine an amplitude correction value based on the signal amplitudes of the first and second sensor signals, and a non-volatile memory (100; 103) configured to store the first and second offset values ​​determined by the processor (98) during calibration mode and the amplitude correction value for an application in operating mode, wherein the processor (98) is configured to determine the rotation angle based on the first and second sensor signals, the first and second offset values ​​and / or the amplitude correction value during the operating mode of the angle sensor (90) with rotations of the measured object in a rotation angle range of less than 360°. [2] Angle sensor (90) according to claim 1, wherein the first sensor element (91) is sensitive to a first directional component of the magnetic field and the second sensor element (92) is sensitive to a second directional component of the magnetic field, wherein the second directional component is perpendicular to the first directional component. [3] Angle sensor (90) according to claim 1, wherein the first and second sensor element (91; 92) are sensitive to the same directional component of the magnetic field, wherein a 90° phase shift between the first and second sensor signal is set by the locations of the first and second sensor element. [4] Angle sensor (90) according to one of the preceding claims, wherein the first and the second sensor element (91; 92) are each designed as a magnetic field sensor element. [5] Angle sensor (90) according to one of the preceding claims, wherein the first and second sensor signals for the 360° rotation of the object being measured during the calibration mode ideally have a mean value of zero and the first and second offset values ​​indicate a respective actual mean deviation from zero. [6] Angle sensor (90) according to one of the preceding claims, wherein the amplitude correction value corresponds to a ratio of the signal amplitudes of the first and the second sensor signal. [7] Angle sensor (90) according to one of the preceding claims, wherein the angle sensor (90) is integrated on a chip and the chip comprises the non-volatile memory (100; 103) for the first and second offset values ​​and the amplitude correction value. [8] Angle sensor (90) according to one of the preceding claims, wherein the processor (98) is configured to determine the rotation angle, AE, based on AE=atan(ADC1−Off1;[ADC2−Off2]*mm) to determine, where ADC1 is the first sensor signal, ADC2 is the second sensor signal, Off1 is the first offset value, Off2 is the second offset value, and mm is the amplitude correction value. [9] Angle sensor (90) according to one of the preceding claims, wherein the processor (98) is configured to perform the calibration during the calibration mode of the angle sensor (90) to determine a rotation angle estimate of the measured object for predetermined reference rotation angles based on the first and second sensor signals, the first and second offset values ​​and / or the amplitude correction value, and to store the difference between the respective rotation angle estimate and the reference rotation angle as an angle correction value. [10] Angle sensor (90) according to claim 9, wherein the processor (98) is configured to, during the operating mode of the angle sensor (90), for rotations of the measured object in a rotation angle range of less than 360° to determine a first rotation angle estimate (56; 85) based on the first and second sensor signals, the first and second offset values ​​and the amplitude correction value and a second rotation angle estimate (77; 86) based on the to determine the first rotation angle estimate (56; 85) and at least one angle correction value. [11] Method (40) for operating an angle sensor (90), comprising: Output (41) of a first sensor signal from a first sensor element (91) as a function of a magnetic field at the location of the first sensor element (91) which depends on a rotation angle of a measured object; Output (42) of a second sensor signal from a second sensor element (92) as a function of the magnetic field at the location of the second sensor element (92), which depends on the rotation angle of the object being measured; during a calibration mode of the angle sensor (90) different from an operating mode, in which at least one 360° rotation of the object being measured is performed: Determining (43) a first offset value of the first sensor signal; Determining (44) a second offset value of the second sensor signal; Determining (45) an amplitude correction value based on signal amplitudes of the first and second sensor signals, Storing (46) the first and second offset values ​​and the amplitude correction value in non-volatile memory (100; 103); and furthermore, encompassing the operating mode of the angle sensor (90) in which rotations of the measured object of less than 360° are carried out, wherein in the operating mode a rotation angle estimate is determined based on the first and second sensor signals, the stored first and second offset values ​​and the stored amplitude correction value. [12] Method (40) according to claim 11, wherein during the calibration mode of the angle sensor (90) a rotation angle estimate of the object being measured is determined for predetermined reference rotation angles based on the first and second sensor signals, the first and second offset values ​​and the amplitude correction value, and a difference between the respective rotation angle estimate and the reference rotation angle is stored as an angle correction value. [13] Method (40) according to claim 12, wherein during the operating mode of the angle sensor (90), for rotations of the measured object in a rotation angle range of less than 360° a first rotation angle estimate (56; 85) is determined based on the first and second sensor signals, the first and second offset values ​​and the amplitude correction value, and a second rotation angle estimate (77; 86) is determined based on the first rotation angle estimate (56; 85) and at least one stored angle correction value. [14] Method (40) according to one of claims 11 to 13, wherein the calibration mode is performed after the angle sensor (90) is installed in an installation environment and the angle sensor (90) is operated in the operating mode after the calibration mode.

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