Method for calculation and electric machine

Abstract

The invention relates to a method for calculating (10) an operating variable (B) of an electric machine (12), comprising at least the steps of providing (14) a data set (16) formed from a plurality of sample points (c), multidimensional and depicting operating parameters of the electric machine (12) and specifying parameter values (C) of a periodic parameter of the operating variable (B) of the electric machine (12) in one dimension, specifying a query point (q) deviating from the sample points (c) in the dimensions of the data set (16), identifying (20) sample points (c) of the data set (16) locally assigned to the query point (q) as reference sample points (c 11 , c 12 , c 21 , c 22 ), parameter correction (24) of the parameter value (C 12 ) at least one second reference sample point (C 12) by a periodic shift depending on a parameter relationship between the parameter value (C 12 ) of the second reference sample point (c 12 ) and the parameter value (C 11 ) of a first reference sample point (c 11 ) to reduce periodically caused parameter discontinuities (18), calculating (26) an approximated parameter value (C q ) at the query point (q) by data approximation (28) at least depending on the corrected parameter value (C' 12 ), calculating (34) the operating variable (B) at least dependent on the approximated parameter value (C q ). Furthermore, the invention relates to an electric machine (12).

Description

[0001] The invention relates to a method for calculating an operating variable of an electric machine according to claim 1. Furthermore, the invention relates to an electric machine.

[0002] EP 2 266 201 A1 describes a control system for electric vehicles which optimizes the efficiency of the electric motor by calculating operating variables of the electric motor, such as the torque-producing current and the flux value, based on a torque specification.

[0003] The objective of the present invention is to calculate the operating parameters of the electric machine more accurately and quickly. Furthermore, the electric machine should operate more reliably and efficiently.

[0004] At least one of these objects is achieved by a calculation method having the features of claim 1. As a result, the parameter correction can be carried out more quickly and accurately and the operating variable can be calculated more accurately and quickly.

[0005] The electric machine can be an electric motor, in particular a permanent magnet synchronous motor. The electric machine can be arranged in a vehicle, in particular a motor vehicle.

[0006] The operating variable can be an operating characteristic of the electric machine, in particular a torque, a flux density, and / or a current density. The operating variable can be described as a complex value. The complex value can be described as a complex number in trigonometric form, in particular in exponential form with a magnitude and a phase, each as real values. The calculated operating variable can be used to improve the noise and vibration behavior of the electric machine.

[0007] The magnitude of the complex operating quantity can be calculated by a transient finite element simulation and subsequent harmonic decomposition, in particular by a Fast Fourier Transformation of a signal obtained over a complete electrical cycle.

[0008] The operating parameters of the data set may include an electrical current, in particular an effective current, an electrical voltage, in particular an effective voltage, a rotor angle, a magnetic field strength and / or a temperature of the electric machine.

[0009] The data set can be at least three-dimensional, with the parameter values in one dimension.

[0010] The sample points may be formed from measured and / or simulated data. The first and second sample points may be spaced apart from each other with respect to a first dimension of the data set. The first and second sample points may be equally positioned with respect to a second dimension of the data set perpendicular to the first dimension.

[0011] The parameter relationship may include a parameter difference between the parameter value of the second reference sample point and the parameter value of the first reference sample point.

[0012] The parameter can be periodic with a period of 2π, corresponding to 360°. The parameter can be cyclic in the complex plane of the operating variable, repeating every 2π, corresponding to 360°. If a multiple of 2π is added to the parameter value, the point representing the operating variable in the complex plane remains unchanged. The parameter can be the periodic phase of the complex operating variable, and the parameter value can be a phase value of the phase. The parameter relationship can be a phase relationship.

[0013] The parameter discontinuity can be a discontinuity or a jump, especially due to the change between the end of the period and the beginning of the period.

[0014] Data approximation may involve interpolation and / or extrapolation. The interpolation may be linear, bilinear, or polynomial. The extrapolation may be linear, bilinear, or polynomial.

[0015] In a preferred embodiment of the invention, it is advantageous if the parameter correction is carried out locally limited to the reference sample points locally assigned to the query point. This allows the parameter correction to be carried out specifically for each query point. A global parameter correction can be omitted. The original sample points and their parameter values, including the reference sample points and their parameter values, can be retained in the data set. The corrected parameter values can leave the original parameter values in the data set untouched. The corrected parameter values can be used exclusively to calculate the approximated parameter value.

[0016] In a specific embodiment of the invention, it is advantageous if the reference sample points comprise the sample points closest to the query point. For a data set with n dimensions, the reference sample points can comprise at least 2 n-1 Reference sample points include.

[0017] In a preferred embodiment of the invention, the parameter correction is performed for a plurality of additional reference sample points, and the approximate parameter value at the query point is calculated by interpolation and / or extrapolation, at least depending on the corrected parameter values of the reference sample points. The parameter correction of the parameter values of the plurality of reference sample points can be performed again for each query point.

[0018] In a specific embodiment of the invention, it is advantageous if the parameter correction involves applying a rounding function to the difference between the parameter value of the second reference sample point and the parameter value of the first reference sample point, wherein the result of the rounding function is a factor. The factor can be a natural number. The parameter correction of the parameter value C 12 of the second reference sample point can be determined depending on the parameter value C 11 of the first reference sample point by calculating the corrected parameter value C12' is calculated as follows C12'=f(R(C12−C112π))

[0019] In a preferred embodiment of the invention, it is advantageous if, with the parameter correction, the corrected parameter value is calculated as the sum or difference of the parameter value of the second reference sample point and the product of the factor and a periodic cycle of the periodic parameter. The periodic cycle can be the full periodic cycle of 2π, corresponding to 360°.

[0020] The parameter correction of the parameter value C 12 of the second reference sample point can be determined depending on the parameter value C 11 of the first reference sample point by calculating the corrected parameter value C 12 is calculated as follows C12'=C12−R(C12−C112π)⋅2π

[0021] In a preferred embodiment of the invention, it is advantageous if the corrected parameter value of the second reference sample point is in turn used to correct the parameter value of another reference sample point. This allows a serial correction of the parameter values to be performed.

[0022] In a preferred embodiment of the invention, it is advantageous if the parameter correction of the parameter value of a fourth reference sample point is carried out by a periodic shift depending on a parameter relationship between the parameter value of the fourth reference sample point and the parameter value of a third reference sample point. The parameter relationship can be a parameter difference between the parameter values of the fourth and third reference sample points.

[0023] The parameter correction of the parameter value C 22of the fourth reference sample point can be determined depending on the parameter value C 21 of the third reference sample point by calculating the corrected parameter value C22' is calculated as follows C22'=C22−R(C22−C212π)⋅2π

[0024] The third and fourth reference sample points may be spaced apart with respect to the first dimension. The third and fourth reference sample points may be equally positioned with respect to the second dimension.

[0025] In an advantageous embodiment of the invention, it is provided that the parameter correction of the third reference sample point is carried out at least as a function of a first averaged parameter difference between the corrected parameter value of the second reference sample point and the parameter value of the first reference sample point and a second averaged parameter difference between the corrected parameter value of the fourth reference sample point and the parameter value of the third reference sample point.

[0026] The corrected parameter value C21' of the third reference sample point can be calculated as follows C21'=C21−R(C2m−C1m2π)⋅2π

[0027] The first averaged parameter value C 1m can be calculated as follows C1m=C11+C12'2

[0028] The second averaged parameter value C 2m can be calculated as follows C2m=C21+C22'2

[0029] A further parameter correction of the already corrected parameter value of the fourth reference sample point can also be performed. The further parameter correction can be performed at least depending on the first and second averaged parameter difference. The further corrected parameter value C22'' of the fourth reference sample point can be calculated as follows C22''=C22'−R(C2m−C1m2π)⋅2π

[0030] Furthermore, within the scope of the invention, an electric machine with the features of claim 10 is proposed to solve at least one of the aforementioned problems. This allows the electric machine to be operated more reliably and efficiently.

[0031] Further advantages and advantageous embodiments of the invention emerge from the description of the figures and the illustrations. Character description

[0032] The invention is described in detail below with reference to the figures. They show in detail: Fig. 1: A method for calculating an operating variable in a specific embodiment of the invention. Fig. 2: A diagram of a data set of the procedure from Fig. 1.

[0033] Fig. 1 shows a method for calculating an operating variable in a specific embodiment of the invention. The method for calculating 10 an operating variable B of an electric machine 12 initially comprises providing 14 a data set 16 formed from a plurality of sample points, multidimensional and depicting operating parameters of the electric machine 12, which is preferably an electric motor, and specifying a periodic parameter of the operating variable B of the electric machine 12 in one dimension.

[0034] Data set 16, which is referred to as an example in the following description, is shown as a diagram in Fig. 2. As shown in Fig. 2 is particularly evident between the sample points c 11 and C 12 and between the sample points c 21 and c 22 a parameter discontinuity 18 is present, which arises from the periodic property of the parameter. The dimension of the x-axis can, for example, indicate a rotor angle of a rotor of the electric motor, in particular in degrees, and the dimension of the y-axis can indicate an effective electrical current, in particular in amperes. The dimension in the z-axis indicates the parameter value, for example a phase value of the torque of the electric motor, in particular in degrees. The grid points of the three-dimensional grid can be measured and / or simulated, in any case stored, sample points.

[0035] Returning to Fig. 1, the first dimension of the data set 16 has a number m of data points and the second dimension of the data set 16 has a number n of data points. Subsequently, a specification 19 of a query point q that differs from the sample points c is made in the dimensions of the data set 16. In Fig. 2 shows an example query point q with the values x = 83 and y = 134, for which the parameter value of the z-axis is to be determined.

[0036] With the given query point q, 20 of the sample points c of the data set 16 locally assigned to the query point q are identified as reference sample points. The reference sample points comprise the sample points c closest to the query point q. Assuming that the query point q lies between i and i+1 in the first dimension and between j and j+1 in the second dimension of the data set 16, the reference sample points are identified, i.e. selected, as follows: first reference sample point c 11 :c ij → c 11 second reference sample point c 12 :c i+1j → c 21 third reference sample point c 21 :c ij+1 → C 12 fourth reference sample point c 22 :c i+1j+1 → c 22

[0037] The existing sample points c ij , ci+1j , cij+1 , c i+1j+1 and their parameter values are not replaced in data set 16, but are used as reference sample points exclusively for further processing, in particular copied.

[0038] Subsequently, a parameter correction 24 of the parameter value C 12 of the second reference sample point by a periodic shift depending on a parameter relationship between the parameter value C 12 of the second reference sample point C 12 and the parameter value C 11 of the first reference sample point C 11 to reduce periodic parameter discontinuities. The parameter correction 24 can change the parameter value C 12 as corrected parameter value C 12 The parameter relationship can be a difference between the parameter value C 12 of the second reference sample point C 12 and the parameter value C 11of the first reference sample point C 11 be.

[0039] The parameter correction 24 comprises applying a rounding function R to the difference between the parameter value C 12 of the second reference sample point C 12 and the parameter value C 11 of the first reference sample point c 11 , where the result of the rounding function R is a factor. With the parameter correction 24, the corrected parameter value is calculated as the difference between the parameter value C 12 of the second reference sample point C 12 and the product of the factor and a periodic cycle, here 2π, corresponding to 360°. This calculates the corrected parameter value C12' C 12 calculated as follows C12'=C12−R(C12−C112π)⋅2π

[0040] The parameter correction 24 of the parameter value C 12 of the second reference sample point C 12is thus carried out by a periodic shift by the multiple of 2π specified by the factor.

[0041] The parameter value c 22 of the fourth reference sample point c 22 is determined as follows depending on the parameter value c 21 of the third reference sample point c 21 and the parameter value c 22 of the fourth reference sample point c 22 corrected C22'=C22−R(C22−C212π)⋅2π

[0042] The parameter correction 24 of the parameter value c 22 of the fourth reference sample point C 22 is thus carried out by a periodic shift by the multiple of 2π specified by the factor.

[0043] The corrected parameter value C 12 of the second reference sample point C 12 is in turn used for parameter correction 24 of the parameter value c 21 of the third reference sample point c 21used. For this purpose, the parameter correction 24 of the parameter value c 21 of the third reference sample point c 21 depending on a first averaged parameter value C 1m between the corrected parameter value C 12 of the second reference sample point C 12 and the parameter value C 11 of the first reference sample point C 11 and a second averaged parameter value C 2m between the corrected parameter value C22' of the fourth reference sample point C 22 and the parameter value c 21 of the third reference sample point c 21 carried out.

[0044] The first averaged parameter value C 1m is calculated as follows C1m=C11+C12'2

[0045] The second averaged parameter value C 2m is calculated as follows C2m=C21+C22'2

[0046] The corrected parameter value C21' of the third reference sample point is calculated as follows C21'=C21−R(C2m−C1m2π)⋅2π

[0047] Furthermore, the already corrected parameter value C22' of the fourth reference sample point C 22 corrected again and as a corrected parameter value C22'' calculated as follows C22''=C22'−R(C2m−C1m2π)⋅2π

[0048] The parameter corrections 24 of the multiple reference sample points c 12 , c 21 , c 22 are locally limited to the reference sample points individually assigned to the query point q.

[0049] With the corrected parameter values C11,C12',C21',C22'', where the parameter value C 11 of the first reference sample point c 11remains unchanged, an approximate parameter value C is calculated 26 q at the query point q by data approximation 28 depending on the corrected parameter values. The data approximation 28 can be a bilinear interpolation 30 or extrapolation 32 of the corrected parameter values C11,C12',C21',C22'' For example, applying a bilinear interpolation 30 in this example results in an output value of the approximated parameter value C q = 99.8.

[0050] Finally, a calculation 34 of the operating variable B is carried out, at least depending on the approximated parameter value C q carried out.

[0051] The procedure can be repeated for all given query points q and requires only minimal computational resources. List of reference symbols 10 Calculation methods 12 electric machine 14 Provision 16 data sets 18 Parameter discontinuity 19 Specification 20 Identification 24 Parameter correction 26 Calculate 28 Data approximation 30 Interpolation 32 Extrapolation 34 Calculate B Company size c sample point c 11 first reference sample point c 12 second reference sample point c 21 third reference sample point c 22 fourth reference sample point C Parameter value C q approximate parameter value q query point R rounding function QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2 266 201 A1

[0002]

Claims

[1] Method for calculating (10) an operating variable (B) of an electric machine (12), comprising at least the steps: Providing (14) a data set (16) formed from a plurality of sample points (c), depicting multidimensional operating parameters of the electric machine (12) and specifying parameter values (C) of a periodic parameter of the operating variable (B) of the electric machine (12) in one dimension, Specification of a query point (q) that differs from the sample points (c) in the dimensions of the data set (16), Identification (20) of sample points (c) of the data set (16) locally assigned to the query point (q) as reference sample points (c 11 , c 12 , c 21 , c 22 ), parameter correction (24) of the parameter value (C 12 ) at least one second reference sample point (c 12) by a periodic shift depending on a parameter relationship between the parameter value (C 12 ) of the second reference sample point (c 12 ) and the parameter value (C 11 ) of a first reference sample point (c 11 ) to reduce periodic parameter discontinuities (18), Calculating (26) an approximated parameter value (C q ) at the query point (q) by data approximation (28) at least depending on the corrected parameter value (C' 12 ), Calculating (34) the operating variable (B) at least as a function of the approximated parameter value (C q ). [2] Method for calculation (10) according to claim 1, characterized by that the parameter correction (24) is applied to the reference sample points (c 11 , c 12 , c 21 , c 22 ) is carried out locally. [3] Method for calculation (10) according to claim 1 or 2, characterized by that the reference sample points (c 11 , c 12 , c 21 , c 22 ) comprise the sample points (c) closest to the query point (q). [4] Method for calculation (10) according to one of the preceding claims, characterized by that the parameter correction (24) for several additional reference sample points (c 21 , c 22 ) is performed and the approximated parameter value (C q ) at the query point (q) by interpolation (30) and / or extrapolation (32) at least depending on the corrected parameter values (C' 12 , C' 21 , C' 22 ) of the reference sample points (22). [5] Method for calculation (10) according to one of the preceding claims, characterized by that the parameter correction (24) involves applying a rounding function (R) to the difference between the parameter value (C12 ) of the second reference sample point (c 12 ) and the parameter value (C 11 ) of the first reference sample point (c 11 ), where the result of the rounding function (R) is a factor. [6] Method for calculation (10) according to claim 5, characterized by that with the parameter correction (24) the corrected parameter value (C' 12 ) as the sum or difference of the parameter value (C 12 ) of the second reference sample point (c 12 ) and the product of the factor and a period cycle of the periodic parameter. [7] Method for calculation (10) according to one of the preceding claims, characterized by that the corrected parameter value (C' 12 ) of the second reference sample point (C 12 ) in turn for the parameter correction (24) of the parameter value (C 21 ) of another reference sample point (c 21 ) is used. [8] Method for calculation (10) according to one of the preceding claims, characterized by that the parameter correction (24) of the parameter value (C 22 ) of a fourth reference sample point (C 22 ) by a periodic shift depending on a parameter relationship between the parameter value (C 22 ) of the fourth reference sample point (c 22 ) and the parameter value (C 21 ) of a third reference sample point (c 21 ) takes place. [9] Method for calculation (10) according to claim 8, characterized by that the parameter correction (24) of the third reference sample point (c 21 ) at least depending on a parameter value between the corrected parameter value (C' 12 ) of the second reference sample point (c 12 ) and the parameter value (C 11 ) of the first reference sample point (c 11 ) first averaged parameter value (c 1m ) and one between the corrected parameter value (C'22 ) of the fourth reference sample point (c 22 ) and the parameter value (C 21 ) of the third reference sample point (c 21 ) second averaged parameter value (c 2m ) takes place. [10] Electric machine (12) which is designed to be operated as a function of an operating variable (B) calculated by a calculation method (10) according to one of the preceding claims.

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