Method for determining the rotational angle output signal of a position sensor

Abstract

The invention relates to a method for determining a rotational angle output signal of a position sensor. In this method, a rotational angle position is measured as a measured angle signal (φ Mess ) as a function of time (S100), and the measured angle signal (φ Mess ) is corrected using a correction angle signal (φ Korr ) (S110) in order to obtain a filter input angle signal (φ FiltEin ). The correction input angle signal (φ KorrEin ) is output as the rotational angle output signal (S140). Furthermore, the filter input angle signal (φ FiltEin ) is filtered (S120) in order to obtain a correction input angle signal (φ KorrEin ), and the correction angle signal (φ Korr ) is determined depending on the correction input angle signal (φ KorrEin ), a frequency (f Mess ) of the filter input angle signal (φ FiltEin ), and an angle error signal (φ Fehler ) (S130), wherein the angle error signal (φ Fehler ) is determined by calculating a difference between the filter input angle signal (φ FiltEin ) and the correction input angle signal (φ KorrEin ). The determination (S130) of the correction angle signal (φ Korr ) comprises determining (S131) a first coefficient and a second coefficient for a first and a second component of at least one harmonic of the angle error signal (φ Fehler ) and determining (S132) the correction angle signal (φ Korr ) depending on the determined first and second coefficients, a first angular function of the first component, and a second angular function of the second component of the at least one harmonic using the frequency (f Mess ) of the filter input angle signal (φ FiltEin ).

Description

[0001]R.404987 Description Title Method for determining a rotation angle output signal from a position sensor The present invention relates to a method for determining a rotation angle output signal from a position sensor as well as a computing unit and a computer program for carrying out the method. Background of the invention Position sensors, such as inductive ones or those based on a magnetoresistive effect, such as GMR (giant magnetoresistance) or TMR (tunnel magnetoresistance), can be used to determine a rotation angle. The rotational movement generates sine and cosine signals in the position sensor, which signals can be recorded by an analog-to-digital converter (ADC). An angle signal determined from these signals can have periodic errors, in particular oscillations. In particular, phase shifts, harmonics orHarmonics on the sine and cosine signals and mechanical influences cannot always be corrected. Disclosure of the Invention According to the invention, a method for determining a rotation angle output signal of a position sensor as well as a computing unit and a computer program for carrying out the method are proposed with the features of the independent R.404987 patent claims. Advantageous embodiments are the subject of the subclaims and the following description. The invention reduces the harmonic error in the position angle signal of a position sensor, which leads to significant rotation angle inaccuracies, by determining and compensating for the harmonic oscillations. This allows the angular quality to be specifically processed in order to achieve the required measurement accuracy, whereby the method is independent of the design, principle, or type of position sensor.In the method according to the invention for determining a rotation angle output signal of a position sensor, a rotation angle position is measured as a function of time as a measured angle signal (raw signal) and corrected with a correction angle signal to obtain a filter input angle signal. The filter input angle signal is passed through a filter, in particular a state variable filter, to determine a correction input angle signal, which is also output as a rotation angle output signal. Using the rotation angle output signal, an electrical machine, for example, can be controlled. The filtering can, in particular, include low-pass filtering, so that as the frequency increases, in particular the harmonic components are filtered out. The correction angle signal is then determined from the angle error, a frequency, in particular the fundamental frequency, the filter input angle signal, and the correction input angle signal.The difference between the filter input angle signal and the correction input angle signal determines an angle error, which essentially includes the filtered-out components, and thus in particular the harmonic components. To determine the correction angle signal, a first coefficient and a second coefficient are determined for a first and a second component of at least one harmonic of the angle error signal. The coefficients are in particular amplitude values ​​for a first and a second component of at least one harmonic. The components can be represented by angle functions, R.404987 in particular sine and cosine functions. Furthermore, a representation using real and imaginary components is also conceivable.Subsequently, the correction angle signal is determined as a function of the determined first and second coefficients and the first angle functions of the first component and the second angle function of the second component of the at least one harmonic using the frequency of the filter input angle signal. The correction angle signal is in particular the sum of a product of the first coefficient with the angle function of the first component and a product of the second coefficient with the angle function of the second component. The angle of the angle function is in particular, depending on the harmonic, a multiple of the frequency, in particular the fundamental frequency, of the filter input angle signal multiplied by time. The correction angle signal essentially contains the harmonic components and their phase position up to a specific or desired order, which are thus subtracted from the raw signal.The method can compensate for periodic angular errors, particularly those caused by harmonics, allowing the angle of rotation to be determined more accurately. The invention can, for example, improve the control of electrical machines comprising a stator and a rotor. This allows significant torque inaccuracies caused by the angular error, which cannot be compensated with previous concepts, to be compensated for, thereby meeting torque accuracy requirements and enabling efficient operation of an electrical machine. Furthermore, cost-effective position sensors can achieve the required measurement accuracies through targeted processing of the angular quality, allowing the method to be implemented cost-effectively. R.404987 Furthermore, the method is not tied to the type or measuring principle of the position sensor or the design of the electrical machine with the position sensor, since the correction is carried out on the angle. It can therefore be transferred to different, even older, types of position sensors, whereby an improvement in torque accuracy can be achieved even in existing systems or future new position sensor systems. In one embodiment, to determine the first coefficient and the second coefficient for the first and second components of at least one harmonic of the angle error signal, the product of the correction input angle signal and the angle function of the first or second component of the at least one harmonic is integrated over a predetermined period of time using the frequency of the filter input angle signal. The predetermined period of time can in particular be the sampling period of the position sensor.By integrating the specified product over time, the coefficients can be determined precisely, allowing the angle error to be compensated particularly precisely and thus achieving the aforementioned advantages in an optimized manner. In an alternative embodiment, to determine the first coefficient and the second coefficient for the first and second components of at least one harmonic of the angle error signal, the product of the correction input angle signal and the first or second angle function of the first or second component of the at least one harmonic, using the frequency of the filter input angle signal, is added at a predetermined time to the first or second coefficient of the previous time in order to obtain the first or second coefficient.The specified time and the previous time are separated by a period of time corresponding to the sampling period of the position sensor. This allows the method to be carried out with low computing power, whereby the aforementioned advantages can be achieved in a simple and efficient manner, particularly even in older computing units with limited computing power. R.404987 In particular, by storing the last determined first and second coefficients at the end of a rotary movement after restarting the angle measurement, harmonics can be compensated in a reduced time, since a correction angle signal is already available with which the measured angle signal can be corrected.In one embodiment, the product of the correction input angle signal and the first angle function of the first component, and the product of the correction input angle signal and the second angle function of the second component, are further formed using an adaptation rate. By using the adaptation rate, also referred to as the "learning rate," a faster adaptation of the first and second coefficients to the angle error can be achieved, thereby reducing the computational effort and the learning time for compensating the angle error. In one embodiment, the first and second coefficients are determined for at least two, three, or four harmonics, and the correction angle signal is determined by the sum of the correction angle signals for each of the harmonics.While improvements in the angle signal can be achieved simply by compensating a single harmonic, particularly the dominant harmonic, the torque accuracy is further improved by compensating multiple harmonics, particularly harmonics of the first to fourth order, because the corrected angle better reflects the actual angle. Since the first to fourth harmonics represent the most dominant oscillations in a system consisting of a position sensor and a rotor, the best results for the angle signal can be achieved with low computational effort by compensating these four harmonics. In one embodiment, the filter input signal is filtered by a state variable filter, which is in particular a filter with low-pass behavior. A state variable filter with low-pass behavior can advantageously dampen the harmonics in the angle signal at high speeds. R.404987 By determining the frequency of the filter input angle signal in the state variable filter, periodic oscillations or harmonics in the frequency of the angle signal at high speeds can be compensated, thereby improving the accuracy of the correction and allowing the method to be carried out in an optimized manner. In a further embodiment, to determine the first coefficient and the second coefficient for a first and a second component of at least one harmonic of the angle error signal, the angular function of a component of the at least one harmonic is determined using the frequency of the filter input angle signal and a phase of the angle error signal. The phase position of the angle error signal and thus the phase position of the individual harmonics is determined in particular by the state variable filter based on its transfer function.In order to determine the phase position of the angular error exactly, the phase response of the angular error is determined using the transfer function of the state variable filter ^. ^,^ ( ^ ) certainly: with the filter input angle signal ^ ^^^^^^^ , Correction input angle signal ^ ^^^^^^^ and angle error signal ^ ^^^^^^ . The transfer function ^ ^,^ ( ^ ) of the state variable filter, which has the following form: ^ ^ ^ ^ + ^ ^ ^ ^ + ^ ^ ( ^ ^,^ ^) = ^ ^ + ^ ^ ^ ^ + ^ ^ ^ ^ + ^ ^ The variables ^ ^ , ^ ^ and ^ ^are filter coefficients that serve to determine the frequency at which the oscillations should be damped, and ^ is the Laplace operator that transforms the transfer function into the Laplace domain. By using the phase of the angle error signal, the determination of the correction angle signal can be further improved, thereby increasing the angle quality R.404987 and torque accuracy, which leads to improved control of the electric machine. A computing unit according to the invention, e.g., a control unit of a motor vehicle, is configured, in particular in terms of programming, to carry out a method according to the invention.The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, since this entails particularly low costs, in particular if an executing control unit is also used for other tasks and is therefore already present. Finally, a machine-readable storage medium is provided with a computer program stored thereon as described above. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, and others. Downloading a program via computer networks (Internet, intranet, etc.) is also possible. Such a download can be wired or cable-based or wireless (e.g. via a WLAN network, a 3G, 4G, 5G or 6G connection, etc.).The invention is shown schematically in the drawing using an exemplary embodiment and is described below with reference to the drawing. Further advantages and embodiments of the invention emerge from the description and the accompanying drawing. Brief description of the drawings Figure 1 shows a block diagram of a computing unit as it can form the basis of the invention; Figure 2 shows a flow diagram of an embodiment of the method. Embodiment(s) of the invention R.404987 Figure 1 shows a block diagram of a computing unit as it can form the basis of the invention. The computing unit has a state variable filter, ZVF, 1 and a correction module 2. The computing unit can be implemented in an evaluation unit of a rotary encoder or position encoder. Figure 2 shows a flow diagram of an embodiment of the method as it can be carried out, for example, in the computing unit shown in Figure 1.In particular, the method is repeated at each time point k, with successive time points (e.g. ^ and ^ + 1) being separated by a sampling period ^. ^ of the position sensor. Figures 1 and 2 are described in the following in a coherent and comprehensive manner. In a step S100, a rotation angle position is measured as a function of time as an angle signal ^ ^^^^ measured. The angle signal ^ ^^^^ can be measured in particular by a position sensor (not shown), which is arranged, for example, on the rotor of an electric machine. The position sensor can generate a sine and cosine signal, whereby the angle can be determined according to atan2(sin / cos). The measured angle signal ^ ^^^^ is in a step S110 with a correction angle signal ^ ^^^^ corrected to a filter input angle signal ^ ^^^^^^^which is fed to the state variable filter 1 as an input signal. The correction of the measured angle signal ^ ^^^^ can be achieved in particular by forming a difference between the angle signal ^ ^^^^ and the correction angle signal ^ ^^^^ The correction angle signal ^ ^^^^ is output by the correction module 2. In a next step S120, the filter input angle signal ^ ^^^^^^^ filtered by the state variable filter 1 to produce a correction input angle signal ^ ^^^^^^^ The filtered signal corresponding to the R.404987 correction input angle signal ^ ^^^^^^^is simultaneously output as a rotation angle output signal, step S140. The rotation angle output signal can then be used further, step S150, for example, for controlling an electrical machine within the framework of vector control, etc. The state variable filter 1 is, in particular, a filter with low-pass behavior, by which harmonic components can be filtered out with increasing frequency or increasing speed. The state variable filter 1 also determines, in particular, a frequency ^ ^^^^ of the filter input angle signal ^ ^^^^^^^ based on the filter input angle signal ^ ^^^^^^^ and then gives the frequency ^ ^^^^ and the correction input angle signal ^ ^^^^^^^ to the correction module 2. In a block S130 in the correction module 2, the correction angle signal ^ ^^^^ depending on the correction input angle signal ^ ^^^^^^^ , the frequency ^ ^^^^of the filter input angle signal and the angle error signal ^ ^^^^^^ , which is the difference between the correction angle input signal ^ ^^^^^^^ and the filter input angle signal ^ ^^^^^^^ is determined. The block S130 of determining the correction angle signal ^ ^^^^ comprises a step S131 of determining a first coefficient and a second coefficient for a first and a second component of at least one harmonic of the angle error signal ^ ^^^^^^ . The components are represented below by angle functions, in particular sine and cosine functions. To determine the first coefficient and the second coefficient, an algorithm can be used that calculates a product of the correction input angle signal ^ ^^^^^^^ and an angular function of the first or second component of the harmonic over a given period of time. In particular, the product can also include an adjustment rate ^^ which allow a faster adaptation of the first and second coefficients to the R.404987 angular error. The argument of the angular function includes the frequency ^ ^^^^ of the filter input angle signal ^ ^^^^^^^ and a phase ^ ^ , which is determined by the correction module 2 using the transfer function of the state variable filter, where the period ^ ^ which can correspond in particular to the sampling rate of the position sensor. Alternatively, it is also possible to determine the first and second coefficients for a selected time ^ using an algorithm in which the first and second coefficients of the previous time ^ − 1 are multiplied by the product of the correction input angle signal ^ ^^^^^^^ and the angular function of the first or second component of the harmonic. The product can, in particular, determine the adjustment rate ^ ^The argument of the angle function consists of the frequency ^ ^^^^ of the filter input angle signal ^ ^^^^^^^ and the phase ^ ^ , which is determined by the correction module 2 based on the transfer function of the state variable filter, where the time is the time ^ ⋅ ^ ^ is chosen, where ^ ^ is the calculation time (time difference between two sampling points, which can correspond in particular to the sampling rate of the position sensor) and k is the numbering of the samples. In a step S132, the correction angle signal ^ ^^^^ depending on the determined first and second coefficients and a first angle function of the first component and a second angle function of the second component of the at least one harmonic using the frequency ^ ^^^^ of the filter input angle signal ^ ^^^^^^^ In other words, the correction angle signal ^^^^^ from a number of harmonics. In the following, step S130 and the associated steps S131 and S132, in which the correction angle signal ^ ^^^^ determined, will be explained in more detail using equations. The index "^" denotes the order of the harmonic under consideration, and quantities with such an index can assume different values ​​depending on the harmonic order under consideration. The angle signals are, even if not specified separately, time-dependent angle signals. R.404987 The angle error signal ^ ^^^^^^can be represented by a sum of an angular function of a first and second component, each multiplied by an amplitude of the error. The components are represented below as sine and cosine components, but can also be represented using real and imaginary components. To determine the total error, the harmonics are summed. The parameterized representation of the angular error signal is ^^^^^^ can be given by the following equation: Where ^ ^ the amplitude of the cosine component and ^ ^ the amplitude of the sine component of the ^-th harmonic. The angular frequency ^ ^ is given by: The angular frequency ^ ^ of the trigonometric functions is therefore a multiple, depending on the order ^ of the harmonic, of the frequency determined by the state variable filter 1 ^ ^^^^ of the filter input angle signal ^ ^^^^^^^. The correction input angle signal ^ ^^^^^^^ can be further represented as follows: Where ^ ^^^^^^ the angle error signal, especially in parameterized representation, ^ ^,^ (^) the transfer function of the state variable filter 1 and ^ ^^^^^^^ the correction input angle signal output by state variable filter 1. R.404987 The relationship between the angle error signal ^ ^^^^^^ , the filter input angle signal ^ ^^^^^^^ and the correction input angle signal ^ ^^^^^^^ can be represented as follows: This also includes the phase ^ ^ of the transfer function, which can then be used to determine the coefficients. The phase can be calculated using the following equation with the angular frequency ^ ^ . To compensate for the periodic angle errors, the correction angle signal ^ ^^^^ the angle error signal ^^^^^^^ are equivalent to: This means that the coefficients ^ ^ and ^^ ^ the coefficient ^ ^ and ^ ^ of the angle error signal ^ ^^^^^^ in parameterized representation to compensate for the angular error. This can be achieved using the following update algorithm: Where ^ is the adjustment rate and the phase of the By integrating these equations over a given period ^ ^ , which can correspond in particular to the sampling rate of the position sensor, the first coefficient ^ ^ and the second coefficient ^^ ^ be determined. In discrete time intervals, the update algorithm can alternatively be implemented as follows: Where ^ ^ a predetermined period of time, which can correspond in particular to the sampling rate of the position sensor. The first and second coefficients ^ ^ , ^^ ^are determined during the implementation of the algorithm by adding the coefficients of the previous time ^ − 1 to the product of the adjustment rate, the correction input angle signal at the selected time ^, and the angle function of the harmonic component at the selected time ^. The time points are located around the period ^ ^ This procedure corresponds to a discrete integration using the Euler method, particularly the Euler method applied backward. The method can therefore be performed with less computing power and can therefore also be implemented in older systems. The correction angle signal can be represented using the determined coefficients and angle functions of the harmonic components as follows: This compensates for periodic angle errors, which correspond in particular to the oscillations of one or more harmonics, whereby, for example, an electrical angle of an electrical machine can be determined more precisely. Since the electrical angle is necessary to determine the torque of an electrical machine, the determination of the torque can be improved and thus the efficiency of the electrical machine increased. R.404987 Furthermore, the method is not tied to a specific type of position sensor or system structure and can therefore be used in older systems as well as future systems. In test bench measurements in which an electrical machine was controlled using the angles determined by the method according to the invention, the selected harmonics could be compensated very well, whereby the method was tested across the entire speed range of the electrical machine.

Claims

R.404987 Claims 1. Method for determining a rotation angle output signal of a position sensor, comprising: measuring (S100) a rotation angle position as a function of time as a measured angle signal (^ ^^^^ ), Correcting (S110) the measured angle signal (^ ^^^^ ) with a correction angle signal (^ ^^^^ ) to generate a filter input angle signal (^ ^^^^^^^ ) to obtain; filtering (S120) the filter input angle signal (^ ^^^^^^^ ) to get a correction input angle signal (^ ^^^^^^^ ) to obtain; determining (S130) the correction angle signal (^ ^^^^ ) depending on the correction input angle signal (^ ^^^^^^^ ), a frequency (^ ^^^^ ) of the filter input angle signal (^ ^^^^^^^ ) and an angle error signal (^ ^^^^^^ ), where the angle error signal (^ ^^^^^^ ) by forming a difference between the filter input angle signal (^ ^^^^^^^ ) and the correction input angle signal (^ ^^^^^^^) is determined, and outputting (S140) the correction input angle signal (^ ^^^^^^^ ) as the rotation angle output signal, wherein determining (S130) the correction angle signal (^ ^^^^ ) comprises: - determining (S131) ​​a first coefficient and a second coefficient for a first and a second component of at least one harmonic of the angle error signal (^ ^^^^^^ ), and - determining (S132) the correction angle signal (^ ^^^^ ) depending on the determined first and second coefficients and a first angle function of the first component and a second angle function of the second component of the at least one harmonic using the frequency (^ ^^^^ ) of the filter input angle signal (^ ^^^^^^^ ). R.404987 2. The method according to claim 1, wherein determining (S131) ​​the first coefficient and the second coefficient for the first and the second component of at least one harmonic of the angle error signal (^^^^^^^ ) includes: Integrating a product of the correction input angle signal (^ ^^^^^^^ ) and the first angular function of the first component of the at least one harmonic, using the frequency (^ ^^^^ ) of the filter input angle signal (^ ^^^^^^^ ), over a given period of time to obtain the first coefficient, and integrating a product of the correction input angle signal (^ ^^^^^^^ ) and the second angular function of the second component of the at least one harmonic, using the frequency (^ ^^^^ ) of the filter input angle signal (^ ^^^^^^^ ), over the predetermined period of time to obtain the second coefficient.

3. The method according to claim 1, wherein determining (S131) ​​the first coefficient and the second coefficient for the first and second components of at least one harmonic of the angle error signal (^ ^^^^^^ ) includes: Adding a product of the correction input angle signal (^^^^^^^^ ) and the first angular function of the first component of the at least one harmonic, using the frequency (^ ^^^^ ) of the filter input angle signal (^ ^^^^^^^ ), at a predetermined time with the first coefficient of a previous time to obtain the first coefficient, and adding a product of the correction input angle signal (^ ^^^^^^^ ) and the first angular function of the first component of the at least one harmonic, using the frequency (^ ^^^^ ) Filter input angle signal (^ ^^^^^^^ ), at the predetermined time with the first coefficient of the previous time to obtain the first coefficient.

4. The method according to claim 2 or 3, wherein the product of the correction input angle signal (^ ^^^^^^^ ) and the first angle function of the first component and the product of the correction input angle signal (^ ^^^^^^^) and the second angle function of the second part, further using an adjustment rate (^ ^ ) are formed. R.404987 5. Method according to one of the preceding claims, wherein the first and second coefficients are determined for at least two, preferably three, particularly preferably four, harmonics and the correction angle signal (^ ^^^^ ) is the sum of the correction angle signals for each of the harmonics.

6. The method according to one of the preceding claims, wherein the filtering (S120) is carried out by a state variable filter (1), wherein the state variable filter (1) is in particular a filter with low-pass behavior.

7. The method according to claim 6, wherein for determining (S131) ​​the first coefficient and the second coefficient for the first and the second component of at least one harmonic of the angle error signal (^ ^^^^^^) the angular function of each component of at least one harmonic using the frequency (^ ^^^^ ) of the filter input angle signal (^ ^^^^^^^ ) and a phase of the angle error signal (^ ^^^^^^ ) is determined.

8. The method according to claim 7, wherein the phase of the angle error signal (^ ^^^^^^ ) is determined using the transfer function of the state variable filter (1).

9. The method according to claim 8, wherein the transfer function of the angular error is given by the following equation: with the transfer function ^ ^,^ ( ^ ) , the filter input angle signal ^ ^^^^^^^ , the correction input angle signal ^ ^^^^^^^ , the filter coefficient ^ ^ , ^ ^ and ^ ^ and the Laplace operator ^.

10. Method according to one of the preceding claims, wherein the correcting (S110) of the measured angle input signal (^ ^^^^) forming a difference between the measured angle input signal (^ ^^^^ ) and the specific correction angle signal (^ ^^^^ ) includes. R.404987 11. The method according to any one of the preceding claims, further comprising using (S150) the rotation angle output signal for controlling an electrical machine.

12. A computing unit configured to perform all method steps of a method according to any one of the preceding claims.

13. A computer program that causes a computing unit to perform all method steps of a method according to any one of claims 1 to 11 when executed on the computing unit.

14. A machine-readable storage medium having a computer program according to claim 13 stored thereon.

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