Method for compensating for interference of a measured angle signal of a magnetic angle sensor of an electric machine, a correspondingly designed microcontroller, an electric machine, and a computer program product

Abstract

A method for compensating interference in a measured angle signal of a magnetic angle sensor of an electrical machine, wherein the method includes: receiving a measured angle signal, estimating a current error and/or a misalignment error in the measured angle signal, calculating an expected rotor angle from the measured angle signal, taking into account the estimated current error and/or the estimated misalignment error, such as during operation of the electrical machine. The present invention furthermore relates to a microcontroller for calculating interference in a measured angle signal of a magnetic angle sensor of an electrical machine, to an electrical machine having a magnetic angle sensor and a microcontroller and to a computer program product.

Claims

1. A method for compensating interference in a measured angle signal of a magnetic angle sensor of an electrical machine, comprising the steps of: providing a measured angle signal; providing a current error being part of the measured angle signal; providing a misalignment error being part of the measured angle signal; and providing an expected rotor angle; providing a measured rotor angle detected by the magnetic angle sensor; providing an estimated rotor angle from an amplitude and an offset of the magnetic angle sensor; receiving the measured angle signal; estimating at least one of the current error or the misalignment error in the measured angle signal by determining a difference from the measured rotor angle minus the estimated rotor angle; calculating the expected rotor angle from the measured angle signal, taking into account at least one of the estimated current error or the estimated misalignment error during operation of the electrical machine.

2. The method as claimed in claim 1, further comprising the steps of: providing a microcontroller; providing a calculation program stored in the microcontroller; and delivering the measured angle signal to the calculation program to estimate the current error and/or the misalignment error.

3. The method as claimed in claim 2, further comprising the steps of: providing the measured angle signal to further comprise at least one error; providing the calculation program to further comprise a model; and providing at least one rotor state; detecting the at least one rotor state by way of the received measured angle signal; mapping at least one of an angle, or an angular velocity, or an angular acceleration onto the current actual rotor state taking into account the at least one error in the measured angle signal.

4. The method of claim 3, further comprising the steps of providing the at least one error to further comprise at least one of an amplitude error, an offset error, the misalignment error, or the current error.

5. The method of claim 2, further comprising the steps of: providing an amplitude error; and providing an offset error; delivering at least one of the amplitude error or the offset error to the calculation program to calculate the expected rotor angle.

6. The method of claim 5, further comprising the steps of: providing at least one observer; providing an observed system; and providing at least one interfering variable; determining the rotor angle error using the at least one observer to reconstruct non-measurable variables from at least one input variable of the observed system and at least one output variable of the observed system.

7. The method of claim 6, further comprising the steps of providing the at least one input variable to further comprise at least one interfering variable.

8. The method of claim 6, further comprising the steps of providing the at least one output variable to further comprise at least one measured variable.

9. The method of claim 6, further comprising the steps of providing the at least one observer to be a Luenberger observer or a Kalman filter.

10. The method of claims 1, further comprising the steps of: providing a rotor angle error; using at least one of the estimated current error or the estimated misalignment error to estimate the rotor angle error by determining a difference from the measured rotor angle minus the estimated rotor angle.

11. The method of claim 10, further comprising the steps of deriving at least one of the actual rotor angle, or the actual angular velocity, or the actual angular acceleration from the estimated rotor angle error.

12. The method of claim 10, further comprising the steps of using the rotor angle error to calculate the expected rotor angle from the received measured angle signal taking into account at least one of the current error or the misalignment error.

13. The method of claim 1, further comprising the steps of: providing three current phases being part of the electrical machine; providing a plurality of errors, each of the plurality of errors corresponding to one of the three current phases; taking into account the plurality of errors when estimating the current error.

14. The method of one of claim 13, further comprising the steps of adding the plurality of errors together to result in one error.

15. The method claim 1, further comprising the steps of calculating the difference from the received measured angle signal affected by current errors to estimate the misalignment error.

16. The method claim 1, further comprising the steps of: providing a microcontroller for receiving the measured angle signal; calculating interference in the measured angle signal of the magnetic angle sensor of the electrical machine using the microcontroller.

17. The method of claim 16, further comprising the steps of: providing a rotor being part of the electrical machine; and providing a permanent magnet arranged on the rotor such that the permanent magnet induces a measureable magnetic field in the angle sensor through a movement of the rotor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and objects of the present invention will become apparent to a person skilled in the art by putting the present teaching into practice and taking into consideration the accompanying drawings, in which:

(2) FIG. 1 shows an arrangement of a sensor and of a permanent magnet on a rotor of an electrical machine;

(3) FIG. 2 shows a schematic depiction of the magnetoresistive effect in permalloy;

(4) FIG. 3 shows a schematic depiction of the structure of an observer;

(5) FIG. 4 shows a schematic depiction of a typical current error;

(6) FIG. 5 shows a diagram of an offset and amplitude observer;

(7) FIG. 6 shows measurement results of the misalignment error using an embodiment of the proposed method;

(8) FIG. 7 shows a diagram of a misalignment error observer;

(9) FIG. 8 shows a diagram of a current error observer;

(10) FIG. 9 shows a schematic depiction of the structure of the proposed method according to one preferred embodiment;

(11) FIG. 10 shows measurement results that were obtained using a method known from the prior art; and

(12) FIG. 11 shows measurement results that were obtained using the proposed method according to one preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(13) The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

(14) Further advantages of popular embodiments are explained in a summary of the following FIGS. 1 to 11.

(15) FIG. 1 shows an arrangement of a magnetic angle sensor 12 and of a permanent magnet 14 that is arranged on a rotor 16 of an electrical machine 10. As illustrated in FIG. 1, the sensor 12 is arranged on a substrate 17 opposite the permanent magnet 14. The substrate 17 is preferably designed as a PCB board or as a ceramic plate. The sensor 12 is arranged opposite the permanent magnet 14 along an axial axis 18 that runs along an extent of the rotor 16. A position of the rotor 16 on which the permanent magnet 14 is arranged is able to be measured by way of the magnetic angle sensor 12. The magnetic angle sensor 12 may for example include a permalloy alloy in which the resistance changes with the direction of the magnetic field. A movement 20 of the rotor 16 is indicated for example in FIG. 1 by the arrow 20. The movement 20 of the rotor 16 may therefore be detected by the angle sensor 12. The angle sensor 12 detects for example the rotor position angle α, the rotor angular velocity α′ and/or the rotor angular acceleration α″.

(16) The magnetic angle sensor 12 preferably contains an alloy in which the measurable resistance in the form of a magnetization M changes as a function of a direction of a magnetic field H. This effect is known as the magnetoresistive effect. Such an alloy may be for example a permalloy alloy. A permalloy alloy preferably contains up to 80% by weight of nickel and up to 20% by weight of iron. FIG. 2 shows a schematic depiction of the magnetoresistive effect. In this case, I indicates a current that is able to be measured in the alloy 20 and that is able to be measured between a voltage difference 22, 24. It is furthermore conceivable for an alloy other than permalloy to be used, as long as the alloy that is used has the magnetoresistive effect.

(17) FIG. 3 shows a schematic depiction of the structure of an observer. The sensor 12 detects the values (sin(θ), cos(θ)) and delivers them to a calculation model. A is the system matrix and C is the output matrix of the system (A, C). The variables A and C may be used to determine whether the system is observable. The system is observable when for example the Kalman criterion or another criterion is met. If this is the case, a state ξ of the system may thus be determined, wherein the estimation error θ−{tilde over (θ)} is amplified by the matrix L in order to correct the estimated value for the state ξ of the system. If the matrix (A-LC) contains only eigenvalues with a negative real part, the observer is stable. The system of equations is then solved by integration, as a result of which the system state ξ is determined.

(18) FIG. 4 shows a schematic depiction of a typical current error X in vector form. A current I measured by the angle sensor 12 includes the current error components X=(x.sub.I, y.sub.I), which lead to the measured angle α.sub.I. The measured phases of the current itself are generally not affected by errors. However, the magnetic field caused by the phase currents causes an error in the sensor. The measured angle α.sub.I therefore does not correspond to the actual angle α, and so the measured angle α.sub.I must be corrected accordingly by subtraction.

(19) FIG. 5 shows a diagram of an offset observer and/or amplitude observer. The variable ΔU is in this case the difference between the measured sensor value (sin(θ), cos(θ)) and the estimate. The variable L is a freely selectable error gain. T is the weighting of the error, which is given by a partial derivation of the sensor signal according to the error sources amplitude and offset. The estimated values for amplitude and offset are adapted by integrating the sensor error—weighted with L and T.

(20) The influence of the offset error is generally the same, whereas the influence of the amplitude error changes with the angle α. A distinction is thereby able to be drawn between the error that contains the offset and the error that contains the amplitude error.

(21) FIG. 6 shows measurement results of the misalignment error in relation to the rotor angle position using one embodiment of the proposed method. FIG. 6a shows measured sensor signals that were measured by the sensor 12, and ideal cosine and sine curves without a model for the offset error for comparison. FIG. 6b shows a resulting angle error AgErr, which results from the misalignment error, superimposed on a modeled angle error AgErrMdl. FIG. 6c shows the difference from the angle error AgErr minus the modeled angle error AgErrMdl. FIG. 6c shows a constant value that fluctuates in terms of absolute value by less than 1°.

(22) FIG. 7 shows a diagram of a misalignment observer, wherein the misalignment error is estimated as a difference between the measured angle and the estimated angle. Otherwise, the calculation runs in parallel with the calculation described with regard to FIG. 5, to which reference is hereby made.

(23) In contrast to FIGS. 5 and 7, FIG. 8 shows a diagram of a current error observer. This furthermore differs in that an error is assigned to each phase I.sub.2, I.sub.2, I.sub.3 of the current I, such that the current error components x.sub.I and y.sub.I may be written as a sum, as described herein. The parameters of the matrix T are freely selectable and include gain factors

(24) $L=\left[\begin{array}{c}{I}_1\\ I_2\\ I_3\end{array}\right].$

(25) Using the detected current of each phase, the parameters p.sub.xn,p.sub.yn, n=1, 2, 3 are able to be adapted accordingly, as is illustrated schematically in FIG. 8.

(26) FIG. 9 shows a schematic depiction of the structure of the proposed method according to one preferred embodiment. In this method of FIG. 9, inter alia, the interference in a measured angle signal of a magnetic angle sensor of an electrical machine is compensated. Wherein the method includes the following steps: receiving a measured angle signal, estimating a current error and/or a misalignment error in the measured angle signal, and calculating an expected rotor angle from the measured angle signal, taking into account the estimated current error and/or the estimated misalignment error, such as during operation of the electrical machine.

(27) FIG. 9 shows an overview of the signal flow of the proposed method. The idea of the method or of the algorithm is to determine non-measurable variables by comparing expected sensor signals (sine signals, cosine signals) with actually measured sensor signals. This takes place in step 30 ‘Rotor Angle Error Calculation’. Before this, however, sensor signals measured by the angle sensor 12 in step 29 are delivered to the described algorithm. The estimation for the rotor state (angle, angular velocity, angular acceleration) is improved by way of the angle error. This takes place in step 32 ‘Rotor Shaft State Observer’. The expected sensor values may be calculated from the estimated rotor angle with ideal values for the amplitude and the offset of the sensor. This takes place in step 34 ‘Sensor Model’. If the sensor behavior deviates from the ideal, this affects the estimation of the rotor state. In a step 36, of a loop 36, the calculated sensor values may again be delivered to the calculation method for compensating interfering fields until no or only a slight deviation from the ideal is able to be established. At the same time, the detected sensor signals are delivered directly to the sensor model 34 in a step 31, such that the sensor model is able to determine the parameters for the sensor model from the measured and the estimated values.

(28) FIG. 10 shows model results that were obtained using a method known from the prior art. The estimation according to the method known from the prior art leads to greatly scattered values between 14 800 and 15 100 rpm, that is to say to values that scatter over a range of 300 rpm.

(29) FIG. 11, on the other hand, shows model results that were obtained using the proposed method according to one preferred embodiment. Using the proposed method, values that constantly scatter in a small range of up to 20 rpm are achieved.

(30) The curves 40 in FIGS. 10 and 11 each show measured curves or results, and the curves 42 each show calculated curves.

(31) The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

LIST OF REFERENCE SIGNS

(32) 10 electrical machine 12 magnetic angle sensor 14 permanent magnet 16 rotor 17 substrate 18 rotor axis 20 movement of the rotor 21 alloy 22, 24 potential difference I current H magnetic field M magnetization α rotor angle α′ angular velocity α″ angular acceleration 29 step 30 rotor angle error calculation step 32 rotor state observer step 34 sensor model 36 loop 40 measured curve 42 calculated curve