Excitation waveform determining device, motor driving device, excitation waveform determining method, motor driving method, and program

Abstract

An excitation waveform determination device (100) sets an initial candidate solution group (IS) and a new candidate solution group (US) as one or more candidate groups for an excitation waveform on the basis of harmonic superimposition conditions (HC) that are information for identifying harmonics to be superimposed on the fundamental wave included in the excitation waveform, executes an electromagnetic field analysis to calculate electromagnetic forces generated in a stator (320) when candidate solutions included in the one or more set candidate solution groups for the excitation waveform are caused to flow through the motor (M), and determines the excitation waveform on the basis of results of executing the electromagnetic field analysis.

Description

[Technical field]

[0001] The present invention relates to an excitation waveform determination device, a motor drive device, an excitation waveform determination method, a motor drive method, and a program, which are particularly suitable for use in exciting a motor. This application claims priority based on Japanese Patent Application No. 2021-185783 filed in Japan on November 15, 2021, the contents of which are incorporated herein by reference in their entirety. [Background technology]

[0002] If a motor vibrates during operation, it may generate noise. Furthermore, if a motor serving as a power source in a hybrid or electric vehicle vibrates, it may affect the ride comfort. Therefore, it is desirable to suppress the vibration of the rotating electric machine. In order to suppress the vibration of the motor, it is possible to change the structure of the motor. However, for example, when changing the structure of an existing motor, large-scale work such as replacing the rotating electric machine is required. Therefore, an excitation signal supplied to the stator coil of the motor to excite the motor is controlled.

[0003] Non-Patent Document 1 describes the use of an excitation current in which a third harmonic current is superimposed on a fundamental current as an excitation current to be passed through a PMSM (Permanent Magnet Synchronous Motor) with an open winding structure in order to suppress the occurrence of torque ripple. Patent Document 1 also describes the use of an excitation current to be passed through an n-phase AC drive current, in which, when the fundamental current of each phase of an n-phase AC is expressed as B×cosθ+C×sinθ, a higher-order current expressed as e×cos(pθ)+f×sin(pθ), where p=6m±1 (m is a natural number), is added to the fundamental current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-312520 A [Non-patent literature]

[0005] [Non-Patent Document 1] Kazunari Honda and Kan Akatsu, "Study on a drive method for open-winding PMSM using third-harmonic current control," IEEJ Transactions on Electrical Engineering, Vol. 141, No. 1, pp. 35-45, January 1, 2021 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the technology described in Non-Patent Document 1, the order of the high frequency to be superimposed on the fundamental wave, which can reduce the torque ripple of the synchronous motor, is specified in advance based on theoretical considerations, and only the harmonic components of the specified order are superimposed on the fundamental wave current. Also, in the technology described in Patent Document 1, the order of the high frequency to be superimposed on the fundamental wave, which can reduce the radial electromagnetic force of the synchronous motor, is specified in advance based on the results of phenomenological considerations, and only the harmonic components of the specified order are superimposed on the fundamental wave current. Therefore, it is difficult to say that the excitation current obtained by the method described in Non-Patent Document 1 and Patent Document 1 is sufficient to suppress the vibration of the motor, and there is a possibility that there is a more optimal excitation current. In fact, Non-Patent Document 1 shows that the sixth harmonic component of the torque ripple of the PMSM can be sufficiently suppressed, but the vibration of the PMSM cannot be sufficiently suppressed.

[0007] The present invention has been made in consideration of the above problems, and has an object to determine a time waveform of an excitation signal that can effectively suppress vibration of a motor. [Means for solving the problem]

[0008] The excitation waveform determination device of the present invention is an excitation waveform determination device that determines an excitation waveform, which is a time waveform of an excitation signal supplied to a stator coil of a motor, and includes a candidate solution setting unit that sets a candidate solution group including one or more candidate solutions of the excitation waveform, an electromagnetic field analysis unit that calculates an electromagnetic force generated in the stator of the motor when the candidate solution included in the candidate solution group is supplied to the motor by performing an electromagnetic field analysis, and an excitation waveform determination unit that determines the excitation waveform based on a result of the electromagnetic field analysis performed by the electromagnetic field analysis unit, wherein the candidate solution setting unit has an initial candidate solution setting unit that sets an initial group of candidate solutions based on a fundamental wave condition, which is information that specifies a fundamental wave of the excitation waveform, and a harmonic superposition condition, which is information that specifies a harmonics to be superimposed on the fundamental wave, and a candidate solution update unit that sets a new group of candidate solutions from the input candidate solution group, and the excitation waveform determination unit determines the excitation waveform from the initial group of candidate solutions or the new group of candidate solutions. The motor driving device of the present invention is a motor driving device that drives a motor, and includes an operating condition acquisition unit that acquires operating conditions when the motor is operating, an excitation waveform acquisition unit that acquires information that identifies the excitation waveform corresponding to the operating conditions when the motor is operating, acquired by the operating condition acquisition unit, from information that identifies the excitation waveform determined for each fundamental wave condition by the excitation waveform determination device, and an excitation signal generation unit that generates an excitation signal for exciting the motor based on the information that identifies the excitation waveform acquired by the excitation waveform acquisition unit.

[0009] The excitation waveform determination method of the present invention is an excitation waveform determination method for determining an excitation waveform, which is a time waveform of an excitation signal supplied to a stator coil of a motor, and includes a candidate solution setting step of setting a candidate solution group including one or more candidate solutions of the excitation waveform, an electromagnetic field analysis step of calculating, by performing an electromagnetic field analysis, an electromagnetic force generated in the stator of the motor when the candidate solution included in the candidate solution group is supplied to the motor, and an excitation waveform determination step of determining the excitation waveform based on a result of the electromagnetic field analysis performed by the electromagnetic field analysis step.The candidate solution setting step includes an initial candidate solution setting step of setting an initial group of candidate solutions based on a fundamental wave condition, which is information that specifies a fundamental wave of the excitation waveform, and a harmonic superposition condition, which is information that specifies a harmonic to be superimposed on the fundamental wave, and a candidate solution updating step of setting a new group of candidate solutions from the input candidate solution group, and the excitation waveform determination step determines the excitation waveform from the initial group of candidate solutions or the new group of candidate solutions. The motor driving method of the present invention is a motor driving method for driving a motor, and includes an operating condition acquisition step of acquiring operating conditions when the motor is operating, an excitation waveform acquisition step of acquiring information identifying the excitation waveform corresponding to the operating conditions when the motor is operating acquired by the operating condition acquisition step from information identifying the excitation waveform determined for each fundamental wave condition by the excitation waveform determination method, and an excitation signal generation step of generating an excitation signal for exciting the motor based on the information identifying the excitation waveform acquired by the excitation waveform acquisition step.

[0010] The program of the present invention causes a computer to function as each part of the excitation waveform determining device. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of a functional configuration of an excitation waveform determining device. [Diagram 2] FIG. 2 is a diagram illustrating an example of a functional configuration of the motor drive device. [Diagram 3] FIG. 3 is a diagram illustrating an example of a configuration of a motor. [Figure 4] FIG. 4 is a diagram showing an example of a time waveform of an excitation current. [Diagram 5] FIG. 5 is a flowchart illustrating an example of a method for determining an excitation waveform. [Figure 6] FIG. 6 is a flowchart illustrating an example of a motor driving method. [Figure 7] FIG. 7 is a diagram illustrating an example of a hardware configuration of the excitation waveform determining device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the term "the same thing" in terms of length, position, size, spacing, etc., includes not only things that are strictly the same, but also things that are different within the scope of the invention (for example, things that differ within the tolerance range determined at the time of design).

[0013] The motor drive system of this embodiment includes an excitation waveform determining device 100 and a motor drive device 200. FIG. 1 is a diagram showing an example of the functional configuration of the excitation waveform determining device 100. FIG. 2 is a diagram showing an example of the functional configuration of the motor drive device 200. The hardware of the excitation waveform determining device 100 and the motor drive device 200 may be realized, for example, by using an information processing device including a processor (e.g., a CPU), a storage device (e.g., a main storage device and an auxiliary storage device), and various interface devices, or dedicated hardware. Note that this embodiment illustrates a case where the excitation waveform determining device 100 and the motor drive device 200 are realized by different hardware. However, the excitation waveform determining device 100 and the motor drive device 200 may be realized by one hardware (one device).

[0014] [Excitation waveform determination device 100] First, an example of the functions of the excitation waveform determining device 100 will be described. The excitation waveform determining device 100 determines an excitation waveform, which is a time waveform of an excitation signal to be supplied to a stator coil of the motor M in order to excite the motor M. In this embodiment, a case where a time waveform of an excitation current is determined as the excitation waveform is exemplified. However, a time waveform of an excitation voltage may be determined as the excitation waveform. The excitation waveform only needs to have a value at each time of one electrical angle cycle. For example, when the excitation waveform is set to a value at each time of one electrical angle cycle, the value at each time of each electrical angle cycle is derived from the value. Also, for example, when a value at each time of the remaining electrical angle half cycle is derived from a value at each time of the electrical angle half cycle, the excitation waveform only needs to have a value at each time of the electrical angle half cycle.

[0015] <Motor M> FIG. 3 is a diagram showing an example of the configuration of the motor M. In FIG. 3, the arrows and symbols shown beside x, y, and z indicate the directions of the x, y, and z coordinates in the xyz Cartesian coordinate system. The symbol with a black circle (●) in a white circle (◯) indicates the direction of the z coordinate. The positive direction of the z axis is the direction from the back side to the front side of the paper. In FIG. 3, the arrows and symbols shown beside r, θ, and z indicate the directions of the r, θ, and z coordinates in the cylindrical coordinate system. The origin of each coordinate is, for example, the rotation axis 0 (center line) of the motor M. However, in FIG. 3, for convenience of notation, each coordinate is shown at a position away from the rotation axis 0 of the motor M.

[0016] In FIG. 3, the motor M includes a rotor 310 and a stator 320. The rotor 310 includes a rotor core 311 and permanent magnets 312a to 312d. The rotor core 311 is formed, for example, by stacking a plurality of electromagnetic steel plates having the same planar shape. The rotor core 311 is not limited to one using an electromagnetic steel plate, which is an example of a soft magnetic plate. The rotor core 311 may be, for example, a powder magnetic core, an amorphous core, or a nanocrystalline core. The rotor core 311 is formed with through holes 311a to 311i that penetrate in a direction parallel to the rotation shaft of the motor M (z-axis direction).

[0017] The center position of the through hole 311a is the same as the position of the rotation axis 0 of the motor M. A rotation shaft is installed in the through hole 311a. The through holes 311b-311e are arranged at intervals in the circumferential direction (θ direction) of the motor M so as to surround the through hole 311a. The through holes 311b-311e have the same shape and size. Permanent magnets 312a-312d are installed in the through holes 311b-311e. With the permanent magnets 312a-312d arranged in the through holes 311b-311e, gaps are formed on both sides of the permanent magnets 312a-312d. The gaps are partial areas of the through holes 311b-311e.

[0018] The through holes 311f-311i are arranged in an area closer to the outer periphery of the motor M (in the positive direction of the r-axis) than the through holes 311b-311e. The through holes 311f-311i have the same shape and size. For example, rivets (not shown) for fixing the rotor core 311 are provided in the through holes 311f-311i.

[0019] Rotor core 311 is formed by stacking and fixing a plurality of electromagnetic steel sheets, each having a shape in which holes corresponding to through holes 311a-311i as described above are formed in a circle, such that the positions of the holes are aligned. Note that through holes other than through holes 311a-311i may be formed in rotor core 311. Furthermore, instead of at least one of through holes 311b-311e, another through hole having at least one of the shape, size, and position different from that of the through hole may be formed in rotor core 311. Furthermore, rotor core 311 may be configured by applying a so-called skew.

[0020] The stator 320 includes a stator core 321 and a stator coil 322. The stator core 321 is formed by stacking, for example, a plurality of electromagnetic steel plates having the same planar shape. The stator core 321 is not limited to one using an electromagnetic steel plate, which is an example of a soft magnetic plate. The stator core 321 may be, for example, a powder core, an amorphous core, or a nanocrystalline core. The stator core 321 has a plurality of teeth portions 321a and a yoke portion 321b (core back portion). For convenience of notation, in FIG. 3, only one of the plurality of teeth portions is denoted by the reference symbol 321a.

[0021] The teeth 321a are arranged at equal intervals in the circumferential direction of the motor M. The teeth 321a have the same shape and size. The yoke 321b has a generally hollow cylindrical shape. The teeth 321a and the yoke 321b are arranged such that the inner end face of the yoke 321b coincides with the outer end face of the teeth 321a. However, the teeth 321a and the yoke 321b are integrated (there is no boundary line).

[0022] Further, the stator coil 322 is disposed in the slot 321c. The slot 321c is a region between two adjacent teeth portions 321a spaced apart in the circumferential direction of the motor M. For convenience of notation, only one stator coil is denoted by the reference numeral 322 in FIG.

[0023] A plurality of electromagnetic steel sheets, each processed to have a shape corresponding to the plurality of teeth portions 321a and yoke portions 321b (slots) as described above, are stacked and fixed so that their contours (inner and outer edges) match with respect to a circle to form stator core 321. Stator core 321 may be configured by applying a so-called skew.

[0024] As is clear from FIG. 3, in this embodiment, the motor M is an inner rotor type IPM (Interior Permanent Magnet) motor. However, the motor M is not limited to an inner rotor type IPM motor. For example, the motor M may be a motor other than a synchronous motor, or may be an outer rotor type motor. Furthermore, the motor M is not limited to a radial gap type motor, and may be an axial gap type motor.

[0025] <Condition Acquisition Unit 101> The condition acquisition unit 101 acquires various conditions necessary for calculations to determine the excitation waveform in the excitation waveform determination device 100. The condition acquisition unit 101 acquires at least the fundamental wave condition BC and the harmonic superposition condition HC. The condition acquisition unit 101 may also acquire the operating conditions of the motor M. The fundamental wave condition BC is information for identifying a fundamental wave (sine wave). The fundamental wave condition BC includes, for example, the amplitude of the fundamental wave and the frequency of the fundamental wave (fundamental frequency). The fundamental wave condition BC may also include a lead angle.

[0026] The operating conditions of the motor M include a speed command value of the motor M and a torque command value of the motor M. The speed command value of the motor M is a command value for the rotation speed of the motor M. The torque command value of the motor M is a command value for the torque of the motor M. The speed command value of the motor M and the torque command value of the motor M acquired by the condition acquisition unit 101 are values ​​(assumed values) assumed as the rotation speed and torque of the motor M. The rotation speed of the motor M corresponds to the fundamental frequency. The torque of the motor M corresponds to the amplitude and advance angle of the excitation current. Therefore, the condition acquisition unit 101 may acquire the amplitude and frequency included in the fundamental wave condition BC by calculating them from the operating conditions of the motor M. In this embodiment, a case will be illustrated in which the condition acquisition unit 101 acquires the fundamental wave condition BC by calculating them from the operating conditions of the motor M.

[0027] For example, a lookup table that stores the rotation speed, torque, and lead angle of the motor M in association with the amplitude, fundamental frequency, and lead angle of the fundamental wave may be stored in advance in the excitation waveform determining device 100. In this case, the condition acquiring unit 101 reads out the amplitude, fundamental frequency, and lead angle of the fundamental wave from the lookup table as information corresponding to the speed command value of the motor M and the torque command value of the motor M. In addition, when the lead angle is fixed, the lead angle may or may not be stored in the lookup table.

[0028] The harmonic superimposing condition HC is information for specifying the harmonic to be superimposed on the fundamental wave. In this embodiment, the harmonic superimposing condition HC includes a harmonic order n, which is information for specifying the order of the harmonic to be superimposed on the fundamental wave included in the excitation waveform. In addition, in this embodiment, a positive integer value n of 2 or more is acquired by the condition acquiring unit 101 as the harmonic order n. In addition, in this embodiment, a case is illustrated in which, when the harmonic order n is acquired, harmonics of each order from 2 to n are superimposed on the fundamental wave. For example, when 3 (n=3) is acquired as the harmonic order n, the second harmonic and the third harmonic are superimposed on the fundamental wave. However, the harmonic order n is not limited to being determined in this manner. For example, the value of n may be set one by one. For example, when 3 (n=3) is acquired as the harmonic order n, only the third harmonic may be superimposed on the fundamental wave. Moreover, when 3 and 5 (n=3, 5) are acquired, the third harmonic and the fifth harmonic may be superimposed on the fundamental wave. In this manner, in this embodiment, any order can be set as the order of the harmonic (harmonic order n) to be superimposed on the fundamental wave.

[0029] The harmonic superposition condition HC may include information for specifying the amplitude of each harmonic. However, in this embodiment, the amplitude of each harmonic is set in the candidate solution setting unit 103 described later. Therefore, the harmonic superposition condition HC does not include information for specifying the amplitude of each harmonic.

[0030] Moreover, the harmonic superposition condition HC does not necessarily have to include the harmonic order n as long as it is information for specifying the harmonic to be superposed on the fundamental wave. For example, the harmonic superposition condition HC may include information capable of specifying the harmonic order n instead of or in addition to the harmonic order n. The information capable of specifying the harmonic order n is, for example, the nth harmonic frequency (a frequency that is n times the fundamental wave frequency). The harmonic superposition condition HC is preferably information capable of specifying the harmonic order n without performing frequency analysis (Fourier transform). This is because it is possible to reduce the calculation load. For example, when at least one of the harmonic order n and the nth harmonic frequency is included in the harmonic superposition condition HC, the harmonic superposition condition HC includes information capable of specifying the harmonic order n without performing frequency analysis. However, the harmonic superposition condition HC may be information capable of specifying the harmonic order n by performing frequency analysis (Fourier transform). For example, the harmonic superposition condition HC may include a modulation condition. The modulation condition is information used to modulate the fundamental wave. The modulation condition includes, for example, at least one of a modulation rate and the number of pulses per electrical angle period.

[0031] In addition, the fundamental wave condition BC and the harmonic superposition condition HC are preferably information that specifies the fundamental frequency and the harmonic frequency, respectively, without performing frequency analysis (Fourier transform). This is because it is possible to reduce the calculation load. For example, if the fundamental wave condition BC includes the fundamental frequency and the harmonic superposition condition HC includes the harmonic order n, the fundamental wave condition BC and the harmonic superposition condition HC include information that specifies the fundamental frequency and the harmonic frequency, respectively, without performing frequency analysis.

[0032] The condition acquisition unit 101 acquires information necessary for executing an electromagnetic field analysis, which will be described later, in addition to the fundamental wave condition BC and the harmonic superposition condition HC. The condition acquisition unit 101 acquires, for example, the shape, size, and physical property values ​​of the motor M.

[0033] An example of the manner in which the condition acquisition unit 101 acquires various conditions is an input operation by an operator OP of a user interface of the excitation waveform determination device 100. However, the manner in which the condition acquisition unit 101 acquires various conditions is not limited to an input operation by the operator OP. For example, the condition acquisition unit 101 may acquire various conditions by receiving them from an external device or reading them from a portable storage medium.

[0034] <Reference value calculation unit 102> The reference value calculation unit 102 calculates an electromagnetic force reference value, which is an electromagnetic force generated in the stator 320 (stator core 321) of the motor M when the motor M is excited with an excitation current of the fundamental wave, based on the fundamental wave condition BC acquired by the condition acquisition unit 101. Here, the electromagnetic force reference value is F s The reference value calculation unit 102 calculates a torque reference value, which is a torque generated in the motor M when the motor M is excited with an excitation current of the fundamental wave, based on the fundamental wave condition BC acquired by the condition acquisition unit 101. Here, the torque reference value is expressed as T s It is written as follows.

[0035] Here, the electromagnetic force reference value F s The reason for calculating is explained below. As described later, the electromagnetic field analysis unit 104 calculates an electromagnetic force calculation value, which is an electromagnetic force generated in the stator 320 (stator core 321) of the motor M when the motor M is excited with an excitation current in which a fundamental wave is superimposed with a harmonic. Here, the electromagnetic force calculation value is F c The main cause of noise generated in the motor M is the vibration of the stator 320 (stator core 321). The vibration of the stator 320 is directly evaluated by the electromagnetic force generated in the stator 320 of the motor M. Then, the electromagnetic force calculation value F c is the electromagnetic force reference value F s The smaller the electromagnetic force calculation value F is, the more the noise of the motor M is reduced compared to the case where the fundamental wave is used as the excitation current. c and the electromagnetic force reference value F sTherefore, in this embodiment, the reference value calculation unit 102 evaluates the difference (magnitude of difference) between the electromagnetic force calculation value F c and the electromagnetic force reference value F s To evaluate the difference with the electromagnetic force reference value F s Calculate.

[0036] Next, the torque reference value T s The reason for calculating is explained below. As described later, the electromagnetic field analysis unit 104 calculates a torque calculation value generated in the motor M when the motor M is excited with an excitation current in which a fundamental wave is superimposed with a harmonic. Here, the torque calculation value is T c As mentioned above, the calculated electromagnetic force F c is the electromagnetic force reference value F s The smaller the calculated torque value T is, the less the noise of the motor M will be. However, by superimposing harmonics on the fundamental wave, the effective value of the excitation current becomes smaller, which may cause a case where the motor M cannot output the expected torque. From this point of view, c and the torque reference value T s It is preferable that the difference between the calculated torque value T c and the torque reference value T s To evaluate the difference between the torque reference value T s Calculate.

[0037] The reference value calculation unit 102 calculates the magnetic flux density (vector) B in each part of the motor M when the motor M is excited with the excitation current of the fundamental wave identified as described above, by performing electromagnetic field analysis using numerical analysis. In this embodiment, a case where a nonlinear unsteady finite element method, which is an example of numerical analysis, is used for the electromagnetic field analysis is illustrated. In addition, in this embodiment, a case where the magnetic flux density B and the eddy current density (vector) Je in each of the elements (meshes) set for the calculation model of the motor M are calculated is illustrated. Note that a numerical analysis method (discretization method) other than the finite element method, such as a difference method, may be used for the electromagnetic field analysis.

[0038] The A-φ method is one of the methods of electromagnetic field analysis using the finite element method. In this case, the basic equations for performing electromagnetic field analysis are given by the following equations (1) to (4) based on Maxwell's equations. In each equation, → indicates a vector.

[0039]

number

[0040] In equations (1) to (4), μ is magnetic permeability, A is vector potential, σ is electrical conductivity, J0 is excitation current density, Je is eddy current density, and B is magnetic flux density. Vector potential A and scalar potential φ are found by simultaneously solving equations (1) and (2). Then, magnetic flux density B and eddy current density Je are found for each element from equations (3) and (4). In equation (1), to simplify the notation, the x-component of magnetic permeability μ x , y component μ y , z component μ z If (μ x =μ y =μ z The formula for (in the case of

[0041] In this embodiment, the reference value calculation unit 102 calculates the electromagnetic force F generated in the stator core 321 based on the magnetic flux density B in each element set for the stator core 321. The reference value calculation unit 102 also calculates the torque T generated in the motor M based on the magnetic flux density B in each element set for the air gap between the rotor core 311 and the stator core 321. The electromagnetic force F and the torque T are calculated, for example, by using a known nodal force method. In the nodal force method, a Maxwell stress tensor is calculated based on the magnetic flux density B, and the electromagnetic forces F in the r direction, θ direction, and z direction are calculated using the Maxwell stress tensor. r , F θ , F z The electromagnetic force (vector) F containing the components is calculated. In addition, the electromagnetic force F in the θ direction θThe torque (vector) T is calculated by using the above formula. Note that the method for calculating the electromagnetic force F and the torque T is not limited to the nodal force method, and other known methods may be used.

[0042] Although the case where a three-dimensional analysis is performed has been exemplified here, it is not necessary to perform a three-dimensional analysis. For example, a two-dimensional analysis may be performed on a cross section of the motor M cut perpendicularly to the rotation axis 0 (z-axis direction). In addition, the method for performing the electromagnetic field analysis is a common method, and therefore a detailed description of the electromagnetic field analysis will be omitted. In addition, the torque reference value T s Since corresponds to the amplitude of the fundamental wave, it is also possible to calculate it from the fundamental wave. Therefore, it is not necessary to use the results of the electromagnetic field analysis to calculate the torque reference value T s There is no need to calculate

[0043] <Candidate solution setting unit 103> The candidate solution setting unit 103 sets one or more candidate solutions of the excitation waveform based on the fundamental wave condition and the harmonic superposition condition (harmonic order n) acquired by the condition acquisition unit 101. Here, the fundamental wave condition is written as BC, and the harmonic superposition condition is written as HC. In this embodiment, the candidate solution setting unit 103 includes an initial candidate solution setting unit 103a and a candidate solution updating unit 103b. The initial candidate solution setting unit 103a generates an initial candidate solution group consisting of one or more candidate solutions based on the fundamental wave condition BC and the harmonic superimposition condition HC (harmonic order n) acquired by the condition acquisition unit 101. The candidate solution update unit 103b sets a new candidate solution group from the input candidate solution group. For example, an excitation waveform in which harmonics of orders n and less than n are superimposed on a fundamental wave is set as a candidate solution. Here, the initial candidate solution group is denoted as IS. Also, the new candidate solution group is denoted as US.

[0044] In this embodiment, the initial candidate solution setting unit 103a and the candidate solution updating unit 103b set multiple candidate solutions (initial candidate solution group IS and new candidate solution group US) according to a real-coded genetic algorithm, which is an example of a metaheuristics method. However, optimization calculations may be performed using a metaheuristics method other than the genetic algorithm. Examples of metaheuristics methods other than the genetic algorithm include hill climbing, tabu search, simulated annealing, and ant colony optimization.

[0045] The number of candidate solutions included in the candidate solution group (initial candidate solution group IS and new candidate solution group US) may be a number determined by an optimization calculation algorithm, or may be determined by a user's designation of the number, calculation time, etc. When the number of harmonic orders specified by the harmonic order n included in the harmonic superposition condition HC is one, the initial candidate solution setting unit 103a and the candidate solution update unit 103b set a time waveform obtained by superimposing a time waveform of a fundamental wave on a time waveform of a harmonic of that order as one of the candidate solutions. When the number of harmonic orders specified by the harmonic order n included in the harmonic superposition condition HC is two or more, the initial candidate solution setting unit 103a and the candidate solution update unit 103b set a time waveform obtained by superimposing a time waveform of a fundamental wave on a time waveform obtained by adding together the time waveforms of the two or more harmonics as one of the candidate solutions. One candidate solution includes information for specifying a value (current value) at each time of one electrical angle cycle.

[0046] The initial candidate solution setting unit 103a sets the order specified by the harmonic order n as the harmonic order. The initial candidate solution setting unit 103a also sets parameters other than the harmonic order, for example, randomly. The initial candidate solution setting unit 103a calculates an initial candidate solution based on the harmonic order and parameters other than the harmonic order. The initial candidate solution setting unit 103a calculates multiple initial candidate solutions by varying the contents of the harmonic order and parameters other than the harmonic order. The initial candidate solution setting unit 103a sets the multiple initial candidate solutions as an initial candidate solution group IS. The candidate solution update unit 103b also sets candidate solutions in the second and subsequent iterations of the genetic algorithm as new candidate solutions. At this time, the candidate solution update unit 103b selects, for example, a predetermined number of candidate solutions in ascending order of the value of the evaluation function J in equation (5) calculated by the evaluation unit 105a described later as new candidate solutions US from among multiple candidate solutions included in the current candidate solution group input to the candidate solution update unit 103b. At this time, the candidate solution update unit 103b selects only candidate solutions that satisfy the constraint equation in equation (6) calculated by the evaluation unit 105a described later. In other words, the candidate solution update unit 103b sorts the candidate solutions that satisfy the constraint equation in equation (6) in ascending order of the value of the evaluation function J in equation (5), and selects a predetermined number of the sorted candidate solutions in ascending order of the value of the evaluation function J.

[0047] Then, the candidate solution update unit 103b executes crossover and mutation. The candidate solution update unit 103b sets the selected predetermined number of candidate solutions and the candidate solutions generated by crossover and mutation as a new candidate solution group US (next generation candidate solution group). The new candidate solution group US generated by crossover and mutation is also generated based on the fundamental wave condition BC and the harmonic superposition condition HC (harmonic order n) acquired by the condition acquisition unit 101. As described above, one candidate solution includes a value (current value) at each time of one electrical angle cycle.

[0048] In this embodiment, a case where the above-mentioned candidate solutions are candidate solutions for the time waveform of the excitation current will be illustrated. Fig. 4 is a diagram showing an example of the time waveform of the excitation current 401. As shown in Fig. 4, the time waveform (excitation waveform) of the excitation current 401 is a time waveform in which harmonics are superimposed on a fundamental wave.

[0049] <Electromagnetic field analysis section 104> The electromagnetic field analysis unit 104 derives the magnetic flux density B and eddy current density Je in the motor M when the motor M is excited with each candidate solution of the excitation waveform (excitation current) included in the candidate solution group (initial candidate solution group IS and new candidate solution group US) set by the candidate solution setting unit 103, by performing an electromagnetic field analysis based on Maxwell's equations. Then, based on the magnetic flux density B in each element set for the stator core 321, the electromagnetic field analysis unit 104 calculates the electromagnetic force F generated in the stator 320 (stator core 321) as an electromagnetic force calculation value F c In addition, the electromagnetic field analysis unit 104 calculates the torque T generated in the motor M based on the magnetic flux density B in each element set for the air gap between the rotor core 311 and the stator core 321 as a torque calculation value T c An example of the method for calculating the magnetic flux density B, the eddy current density Je, the electromagnetic force, and the torque is as described in the section <Reference value calculation unit 102>, so a detailed description of the calculation method will be omitted here. In this embodiment, the electromagnetic force reference value F s and the calculated electromagnetic force F c Here, the electromagnetic force reference value F is expressed as a vector (a vector determined by a circumferential component and a radial component). However, this is not necessarily the case. For example, the electromagnetic force reference value F s and the calculated electromagnetic force F c may be expressed using only the radial component.

[0050] <Excitation Waveform Determination Unit 105> The excitation waveform determination unit 105 determines an excitation waveform from the initial candidate solution group IS or a new candidate solution group US set by the candidate solution setting unit 103 based on the result of the electromagnetic field analysis performed by the electromagnetic field analysis unit 104. In other words, if the excitation waveform determination unit 105 can determine (select) an excitation waveform from the initial candidate solution group IS, the candidate solution setting unit 103 does not set a new candidate solution group US. On the other hand, if the excitation waveform determination unit 105 cannot determine an excitation waveform from the initial candidate solution group IS, the candidate solution setting unit 103 sequentially generates a new candidate solution group US by updating the initial candidate solution group IS. The excitation waveform determination unit 105 determines (selects) an excitation waveform from the new candidate solution group US sequentially generated by the candidate solution setting unit 103. In this embodiment, the excitation waveform determination unit 105 has an evaluation unit 105a and a determination unit 105b.

[0051] <<Evaluation Unit 105a>> The evaluation unit 105a calculates values ​​of evaluation indices including an electromagnetic force evaluation index for evaluating the value of an electromagnetic force generated in the stator 320 (stator core 321) based on the result of the electromagnetic field analysis performed by the electromagnetic field analysis unit 104. In this embodiment, the evaluation unit 105a further calculates, as an evaluation index, a value of a torque evaluation index for evaluating the value of a torque generated in the stator 320 (stator core 321) based on the result of the electromagnetic field analysis performed by the electromagnetic field analysis unit 104. As described above, in this embodiment, the electromagnetic force calculation value F calculated by the electromagnetic field analysis unit 104 c is the electromagnetic force reference value F calculated by the reference value calculation unit 102. s The smaller the electromagnetic force calculation value F c and the electromagnetic force reference value F s In this embodiment, the torque calculation value T c is the torque reference value T calculated by the reference value calculation unit 102. s It is preferable not to deviate too much from the calculated torque value T c and the torque reference value T sThe case where the index for evaluating the difference between the torque and the torque saturation torque is used as the torque evaluation index will be exemplified.

[0052] Here, the electromagnetic force is calculated as a vector, so the electromagnetic force calculation value F c The size of |F c Similarly, the electromagnetic force reference value F s The size of |F s In addition, the torque is calculated as a vector, so the calculated torque value T c The size of |T c Similarly, the torque reference value T s The size of |T s In this embodiment, the electromagnetic force calculation value F c and the electromagnetic force reference value F s The case where the difference between the calculated torque value T c and the torque reference value T s The case where the difference between is evaluated using the constraint equation (6) below will be illustrated.

[0053]

number

[0054] In formula (5), min. is a symbol indicating that the minimum value of J is to be calculated. In formula (6), ε is a positive value that is set in advance. If the value of ε is too large, the torque calculation value T c and the torque reference value T s A candidate solution that has a large difference from is more likely to be selected. On the other hand, if the value of ε is too small, there is a risk that a solution cannot be found (so-called no solution). ε is set in advance from this perspective. In this embodiment, the value on the right side of equation (5) and the value on the left side of equation (6) are examples of the values ​​of the evaluation indexes. Also, the right side of equation (5) is an example of an electromagnetic force evaluation index, and the left side of equation (6) is an example of a torque evaluation index.

[0055] When the evaluation unit 105a calculates the value of the evaluation index as described above, the candidate solution update unit 103b sorts the candidate solutions that satisfy the constraint equation (6) in order from the smallest value of the evaluation function J in equation (5), and selects a predetermined number of the sorted candidate solutions in order from the smallest value of the evaluation function J. Then, the candidate solution update unit 103b executes crossover and mutation. The candidate solution update unit 103b sets the selected predetermined number of candidate solutions and the candidate solutions generated by crossover and mutation as a new candidate solution group US (next generation candidate solution group).

[0056] The processes in the candidate solution update unit 103b, the electromagnetic field analysis unit 104, and the evaluation unit 105a are repeatedly executed until a predetermined calculation end condition is satisfied. The candidate solution update unit 103b outputs a candidate solution when the predetermined calculation end condition is satisfied to the determination unit 105b. Here, the candidate solution when the predetermined calculation end condition is satisfied is denoted as ES. In this embodiment, a case where an optimization calculation is executed by a real-valued genetic algorithm is exemplified. Therefore, as the calculation end condition, a condition generally adopted in the genetic algorithm method is used, such as a predetermined number of generation changes being performed, or the difference between the candidate solution from the previous time and the current time being a predetermined condition (for example, the candidate solution from the previous time and the current time is no longer changed). Incidentally, since the genetic algorithm itself can be realized by known technology, a detailed description thereof will be omitted here.

[0057] <<Decision section 105b>> The determining unit 105b determines an excitation waveform based on the value of the evaluation index calculated by the evaluating unit 105a. The determination unit 105b determines, among the candidate solutions ES when a predetermined calculation end condition is satisfied, the candidate solution for which the value of the evaluation function J in equation (5) is the smallest as the optimum solution, and calculates (determines) the excitation waveform identified from the candidate solution as the optimum solution of the excitation waveform. The optimum solution of the excitation waveform includes information for identifying the value (current value) at each time of one electrical angle cycle. In the following description, the information included in the optimum solution of the excitation waveform for identifying the value (current value) at each time of one electrical angle cycle is also referred to as optimum waveform identification information.

[0058] <Processing for each fundamental wave condition BC (operating condition of motor M)> The processing by the reference value calculation unit 102, the candidate solution setting unit 103, the electromagnetic field analysis unit 104, and the excitation waveform determination unit 105 is performed for each of one or more fundamental wave conditions BC acquired by the condition acquisition unit 101. As described above, the fundamental wave conditions BC include the amplitude and frequency (fundamental frequency) of the fundamental wave. The fundamental wave conditions BC may also include a lead angle. The rotation speed of the motor M corresponds to the fundamental frequency. The torque of the motor M corresponds to the amplitude and lead angle of the excitation current. Therefore, performing the processing by the reference value calculation unit 102, the candidate solution setting unit 103, the electromagnetic field analysis unit 104, and the excitation waveform determination unit 105 for each of one or more fundamental wave conditions BC corresponds to performing the processing for each of one or more operating conditions (rotation speed, torque, etc.) of the motor M. In addition, when there is only one fundamental wave condition BC (operating condition of the motor M) acquired by the condition acquisition unit 101, the processing by the reference value calculation unit 102, the candidate solution setting unit 103, the electromagnetic field analysis unit 104, and the excitation waveform determination unit 105 need only be performed for that fundamental wave condition BC (operating condition).

[0059] <Output unit 106> The output unit 106 outputs the optimum solution (optimum waveform identification information) of the excitation waveform determined by the determination unit 105b. An example of an output form of the optimum waveform identification information is transmission to the motor driving device 200. The communication between the excitation waveform determining device 100 and the motor driving device 200 may be wired communication or wireless communication. The output form of the optimum waveform identification information is not limited to transmission to the motor driving device 200. For example, the output unit 106 may store the optimum waveform identification information in a storage medium inside or outside the excitation waveform determining device 100, or may display it on a computer display.

[0060] [Motor driving device 200] Next, a description will be given of an example of functions of the motor driving device 200. The motor driving device 200 drives the motor M based on the excitation waveform determined by the excitation waveform determining device 100. <Excitation waveform storage section 201> The excitation waveform storage unit 201 stores the optimum waveform specification information determined by the excitation waveform determination device 100 for each operating condition of the motor M. As described above, the operating conditions of the motor M include a speed command value of the motor M and a torque command value of the motor M. The excitation waveform storage unit 201 may be located outside the motor drive device 200. The excitation waveform determination device 100 determines the optimum waveform specification information for each of one or more fundamental wave conditions BC. As described above, determining the optimum waveform specification information for each of one or more fundamental wave conditions BC is equivalent to determining the optimum waveform specification information for each of one or more operating conditions of the motor M. Therefore, storing the optimum waveform specification information determined by the excitation waveform determination device 100 for each operating condition of the motor M is equivalent to storing the optimum waveform specification information determined by the excitation waveform determination device 100 for each fundamental wave condition BC.

[0061] <Operation condition acquisition unit 202> The operating condition acquisition unit 202 acquires new operating conditions different from the current operating conditions as operating conditions when the motor M is operated. It is assumed that there are no current operating conditions when the motor M starts operating. Therefore, when the motor M starts operating, the operating condition acquisition unit 202 acquires the operating conditions at the start of operation of the motor M as new operating conditions. As described above, the operating conditions of the motor M include a speed command value of the motor M and a torque command value of the motor M. For example, the operating condition acquisition unit 202 acquires the operating conditions when the motor M is operated from the control device 210. Here, the operating conditions when the motor M is operated are represented as OC. For example, the control device 210 may generate a torque command value according to the difference between the actual torque value and the target value of the motor M, or may generate a speed command value according to the difference between the actual rotation speed value and the target value of the motor M. Note that the operating condition acquisition unit 202 does not necessarily need to acquire the operating conditions OC when the motor M is operated from the control device 210. For example, the operating conditions OC during operation of the motor M may be set (scheduled) in advance. In such a case, the operating condition acquisition unit 202 may acquire the set operating conditions based on, for example, an input operation by an operator of a user interface of the motor drive device 200.

[0062] <Excitation waveform acquisition unit 203> The excitation waveform acquisition unit 203 acquires optimal waveform identification information corresponding to the operating conditions OC when the motor M is operating, acquired by the operating condition acquisition unit 202, from the optimal waveform identification information for each operating condition of the motor M stored in the excitation waveform memory unit 201.

[0063] <Excitation signal generation unit 204> The excitation signal generating unit 204 generates an excitation current for exciting the motor M based on the optimum waveform identification information acquired by the excitation waveform acquiring unit 203. For example, when the motor driving device 200 executes PWM (Pulse Width Modulation) control, the excitation signal generating unit 204 executes, for example, the following process. First, the excitation signal generating unit 204 generates a modulated wave based on the optimum waveform identification information. Then, the excitation signal generating unit 204 generates a pulse signal by comparing the generated modulated wave with a predetermined carrier wave (e.g., a triangular wave), and supplies the pulse signal to the stator coil 322 of the motor M. Note that the method of generating the excitation current is not limited to a method based on PWM control, and may be other known methods (e.g., a method based on PAM (Pulse Amplitude Modulation) control). Also, the excitation signal generating unit 204 may supply the excitation current specified by the optimum waveform identification information to the motor M as it is. In addition, the excitation signal generating unit 204 may convert the excitation current specified by the optimal waveform specifying information into an excitation voltage using the impedance of the motor M and supply it to the motor M.

[0064] [flowchart] Next, an example of an excitation waveform determination method of this embodiment using the excitation waveform determination device 100 will be described with reference to the flowchart of Fig. 5. The flowchart of Fig. 5 may be realized, for example, by a process including a processor of the excitation waveform determination device 100 executing a program stored in a storage device of the excitation waveform determination device 100. First, in step S501, the condition acquisition unit 101 acquires various conditions necessary for calculations to determine the excitation waveform in the excitation waveform determination device 100. These conditions include a fundamental wave condition BC and a harmonic superposition condition HC. In this embodiment, a case is illustrated in which the condition acquisition unit 101 acquires the fundamental wave condition BC by calculating the fundamental wave condition BC based on the operating conditions of the motor M. The operating conditions of the motor M include a speed command value of the motor M and a torque command value of the motor M. Next, in step S502, the condition acquisition unit 101 selects one fundamental wave condition BC that has not been selected in this step S502 from among the fundamental wave conditions BC (operating conditions of the motor M) acquired in step S501.

[0065] Next, in step S503, the reference value calculation unit 102 calculates an electromagnetic force reference value F, which is an electromagnetic force generated in the stator 320 (stator core 321) of the motor M when the motor M is excited with an excitation current of a fundamental wave specified from the fundamental wave condition BC selected in step S502. s and the torque reference value T which is the torque generated in the motor M when the motor M is excited by the excitation current of the fundamental wave. s and are calculated by performing an electromagnetic field analysis on the motor M.

[0066] Next, in step S504, the initial candidate solution setting unit 103a sets an initial candidate solution group IS, which is an initial value of a candidate solution group made up of a plurality of candidate solutions of the excitation waveform. Next, in step S505, the electromagnetic field analysis unit 104 performs step S 504 The electromagnetic force calculation value F is the electromagnetic force generated in the stator 320 (stator core 321) of the motor M when the motor M is excited with the excitation waveform (excitation current) specified by the candidate solution set in c and the calculated torque T which is generated in the motor M when the motor M is excited with the excitation waveform (excitation current) c The electromagnetic field analysis unit 104 calculates the above electromagnetic force calculation values ​​F c and the calculated torque value T cThe calculation of is performed for each of the candidate solutions included in the initial candidate solution group IS.

[0067] Next, in step S506, the evaluation unit 105a calculates the electromagnetic force F c and the electromagnetic force reference value F s The value of the evaluation index that evaluates the difference between the calculated torque value T c and the torque reference value T s Specifically, the evaluation unit 105a calculates the value of the evaluation index that evaluates the difference between the evaluation function J(=|F c |-|F s |) and the left side of equation (6) (||T s |-|T c Calculate the value of ||.

[0068] Next, in step S507, the candidate solution update unit 103b updates the candidate solution group to set a new candidate solution group US. Specifically, the candidate solution setting unit 103 arranges the candidate solutions that satisfy the constraint equation (6) in order from the smallest value of the evaluation function J in equation (5), and selects a predetermined number of the arranged candidate solutions in order from the smallest value of the evaluation function J. Then, the candidate solution update unit 103b executes crossover and mutation. The candidate solution update unit 103b sets the selected predetermined number of candidate solutions and the candidate solutions generated by crossover and mutation as a new candidate solution group US (next generation candidate solution group).

[0069] Next, in step S508, the determining unit 105b judges whether or not the calculation end condition is satisfied. If the result of this judgment is that the calculation end condition is not satisfied (NO in step S508), the process of step S505 is executed again. In this case, in step S505, the new candidate solution group US updated in step S507 is used instead of the initial candidate solution group IS set in step S504.

[0070] As a result of the determination in step S508, if the calculation end condition is satisfied (YES in step S508), the process of step S509 is executed. In step S509, the determination unit 105b determines the candidate solution having the smallest value of the evaluation function J in equation (5) among the candidate solutions ES when the calculation end condition is satisfied as the optimal solution, and calculates (determines) the excitation waveform identified from the candidate solution as the optimal solution of the excitation waveform. Then, the determination unit 105b generates information for identifying the value (current value) at each time of one electrical angle cycle, which is included in the optimal solution of the excitation waveform, as optimal waveform identification information.

[0071] Next, in step S510, the output section 106 outputs to the motor driving device 200 the optimum waveform identification information generated in step S509. Next, in step S511, the excitation waveform determining device 100 judges whether or not optimal waveform identification information has been generated for all of the fundamental wave conditions BC (operating conditions of the motor M) acquired in step S501. If the result of this judgment is that optimal waveform identification information has not been generated for all of the fundamental wave conditions BC (operating conditions of the motor M) acquired in step S501 (NO in step S511), the process of step S502 is executed again. Then, when optimal waveform identification information has been generated for all of the fundamental wave conditions BC (operating conditions of the motor M) acquired in step S501 (YES in step S511), the process according to the flowchart of FIG. 5 ends.

[0072] Next, an example of the motor driving method of this embodiment using the motor driving device 200 will be described with reference to the flowchart of Fig. 6. It is assumed here that optimal waveform specification information for fundamental wave conditions BC corresponding to all operating conditions assumed as operating conditions of the motor M is stored in the excitation waveform storage unit 201 before the flowchart of Fig. 6 is started. The flowchart of Fig. 6 may be realized, for example, by a process including a processor of the motor driving device 200 executing a program stored in a storage device of the motor driving device 200.

[0073] First, in step S601, the operating condition acquisition unit 202 determines whether or not an operating condition different from the current operating condition has been acquired as an operating condition OC during operation of the motor M. If the result of this determination is that the operating condition OC during operation of the motor M has not been acquired (NO in step S601), the operating condition acquisition unit 202 waits until the operating condition OC during operation of the motor M is acquired. Then, when the operating condition OC during operation of the motor M is acquired (YES in step S601), the process of step S602 is executed.

[0074] In step S602, the motor driving device 200 determines whether or not to terminate the operation of the motor M based on the operating condition OC during operation of the motor M. If the result of this determination is that the operation of the motor M is not to be terminated (NO in step S602), the process of step S603 is executed. In step S603, the excitation waveform acquisition unit 203 acquires optimal waveform specification information corresponding to the operating condition OC during operation of the motor M acquired by the operating condition acquisition unit 202 from the optimal waveform specification information for each fundamental wave condition BC (operating condition of the motor M) stored in the excitation waveform storage unit 201.

[0075] Next, in step S604, the excitation signal generating unit 204 generates an excitation current for exciting the motor M based on the optimal waveform specifying information acquired in step S603, and supplies the generated excitation current to the motor M.

[0076] As a result of the determination in step S602 described above, when the operation of the motor M is to be ended (step S60 2 If the answer is YES in step S605, the process of step S605 is executed. In step S605, the excitation signal generating unit 204 stops the supply of the excitation current to the motor M. When the process of step S605 ends, the process according to the flowchart in FIG. 6 ends.

[0077] <Hardware of the excitation waveform determining device 100> Next, a description will be given of an example of hardware of the excitation waveform determining device 100. In Fig. 7, the excitation waveform determining device 100 has a CPU 701, a main memory device 702, an auxiliary memory device 703, a communication circuit 704, a signal processing circuit 705, an image processing circuit 706, an I / F circuit 707, a user interface 708, a display 709, and a bus 710.

[0078] The CPU 701 controls the entire excitation waveform determining device 100. The CPU 701 uses the main memory device 702 as a work area to execute programs stored in the auxiliary memory device 703. The main memory device 702 temporarily stores data. The auxiliary memory device 703 stores various types of data in addition to the programs executed by the CPU 701.

[0079] The communication circuit 704 is a circuit for communicating with the outside of the excitation waveform determining device 100. The communication circuit 704 may perform wireless communication or wired communication with the outside of the excitation waveform determining device 100.

[0080] The signal processing circuit 705 performs various signal processing operations on signals received by the communication circuit 704 and signals input under the control of the CPU 701 . The image processing circuit 706 performs various types of image processing on the input signal under the control of the CPU 701. The signal that has undergone this image processing is output to a display 709, for example. The user interface 708 is a part where an operator OP issues instructions to the excitation waveform determining device 100. The user interface 708 has, for example, buttons, switches, dials, etc. The user interface 708 may also have a graphical user interface using a display 709.

[0081] The display 709 displays an image based on the signal output from the image processing circuit 706. The I / F circuit 707 exchanges data with devices connected to the I / F circuit 707. In FIG. 7, a user interface 708 and a display 709 are shown as devices connected to the I / F circuit 707. However, the devices connected to the I / F circuit 707 are not limited to these. For example, a portable storage medium may be connected to the I / F circuit 707. At least a part of the user interface 708 and the display 709 may be located outside the excitation waveform determining device 100.

[0082] The CPU 701, the main storage device 702, the auxiliary storage device 703, the signal processing circuit 705, the image processing circuit 706, and the I / F circuit 707 are connected to a bus 710. Communication between these components is performed via the bus 710. The hardware of the motor driving device 200 may be realized by replacing the excitation waveform determining device 100 with the motor driving device 200 in the <Hardware of the excitation waveform determining device 100> section and FIG. 7. Therefore, a detailed description of the hardware of the motor driving device 200 will be omitted. The hardware of the excitation waveform determining device 100 and the motor driving device 200 is not limited to the hardware shown in FIG. 7 as long as it can realize the functions of the excitation waveform determining device 100 and the motor driving device 200 described above. For example, a GPU may be used as a processor instead of or in addition to the CPU 701.

[0083] [Calculation example] Next, a calculation example will be explained. In this calculation example, a numerical analysis was performed on an inner rotor type IPM motor as the motor to be calculated. The typical specifications of an IPM motor are as follows: Stator outer diameter: 140mm Rotor outer diameter: 88.4mm Height (core stack thickness): 24mm vinegar Te Number of slots: 48 Number of poles: 8 The results of this calculation example are shown in Table 1. Note that in Table 1, the electromagnetic force and torque values ​​are non-dimensional relative values ​​with their respective maximum values ​​being 1.

[0084] [Table 1]

[0085] In Table 1, opt (invention example) indicates that the IPM motor was excited with the optimal solution (excitation current) of the excitation waveform calculated using the method of this embodiment. sin (comparison example) indicates that the IPM motor was excited with the fundamental wave (excitation current) used when the optimal solution of the excitation waveform was calculated. In the explanation of this calculation example, the optimal solution (excitation current) of the excitation waveform calculated using the method of this embodiment is also referred to as the opt current. In addition, the fundamental wave (excitation current) used when the optimal solution of the excitation waveform was calculated is also referred to as the sin current.

[0086] The rotation speed is the rotation speed of the IPM motor (rotor). The electromagnetic force is the electromagnetic force generated in the stator core. The torque is the torque generated in the IPM motor. The reduction rate is the reduction rate of the electromagnetic force generated in the IPM motor when excited with an opt current compared to the electromagnetic force generated in the IPM motor when excited with a sin current. Specifically, the reduction rate is calculated by performing the calculation (sin-opt)÷sin×100. In this formula, opt is the electromagnetic force generated in the IPM motor when excited with an opt current. sin is the electromagnetic force generated in the IPM motor when excited with a sin current.

[0087] From Table 1, it can be seen that under all of conditions 1 to 4, opt (example of the invention) reduces the electromagnetic force more than sin (comparative example). It can also be seen that under operating conditions such as condition 1, where the rotation speed and torque are small and the vibration of the IPM motor is not large, the electromagnetic force reduction effect is not large. A comparison of conditions 1 and 2 shows that the greater the torque, the greater the electromagnetic force reduction effect. A comparison of conditions 1, 3 and 4 shows that the higher the rotation speed, the greater the electromagnetic force reduction effect. From the above, it can be seen that in this calculation example, the greater the torque and rotation speed, the greater the electromagnetic force reduction effect can be expected.

[0088] Therefore, the output unit 106 (FIG. 1) may output the excitation waveform based on the rotation speed and torque. Specifically, the output unit 106 may output a candidate solution ES when a calculation end condition is satisfied when a predetermined output condition is satisfied. The predetermined output condition is, for example, a condition determined from the following three conditions. The first condition is a rotation speed condition that the rotation speed of the motor M is equal to or higher than a predetermined rotation speed. The second condition is a torque condition that the torque of the motor M is equal to or higher than a predetermined torque. The third condition is a condition that both the rotation speed condition and the torque condition are satisfied (the rotation speed of the motor M is equal to or higher than a predetermined rotation speed and the torque of the motor M is equal to or higher than a predetermined torque). In addition, the output unit 106 may not output a candidate solution when the predetermined output condition is not satisfied, and may output, for example, information indicating that the output condition is not satisfied. For example, by doing this, the motor drive device 200 (FIG. 2) can use the excitation waveform determined by the excitation waveform determination device 100 within a range corresponding to at least one of the rotation speed condition and the torque condition. Therefore, when driving the motor M, the motor drive device 200 can use the excitation waveform determined by the excitation waveform determination device 100 only when the vibration suppression effect of the motor M is high. For example, when the excitation signal generation unit 204 generates an excitation waveform using an inverter such as a PWM inverter, the excitation waveform to be generated may become complex. In this case, the switching of the inverter may increase, which may increase losses. Therefore, when the vibration suppression effect of the motor M is small or almost nonexistent, the motor drive device 200 can drive the motor M with a normal excitation waveform. Note that, for example, the excitation waveform determination device 100 determines whether the torque condition is satisfied by using the torque reference value T output from the reference value calculation unit 102. sIn this way, the excitation waveform determination device 100 can, for example, exclude candidate solutions that do not satisfy the torque condition from candidates for the optimum solution. This allows the load on the excitation waveform determination device 100 to be reduced. Furthermore, the excitation waveform acquisition unit 203 may determine whether or not to use the information from the excitation waveform storage unit 201 based on the operating conditions obtained from the operating condition acquisition unit 202 and at least one of the torque condition and the rotation speed condition. Furthermore, when the information from the excitation waveform storage unit 201 is not used, the excitation waveform acquisition unit 203 may calculate the excitation waveform by a known normal process, or may acquire an excitation waveform generated by another functional unit (not shown) that performs a known normal process.

[0089] [summary] As described above, in this embodiment, the excitation waveform determination device 100 sets an initial candidate solution group IS and a new candidate solution group US as one or more candidate groups of the excitation waveform based on the harmonic superposition condition HC, which is information specifying the harmonics to be superimposed on the fundamental wave included in the excitation waveform. The excitation waveform determination device 100 calculates, by performing an electromagnetic field analysis, the electromagnetic force generated in the stator 320 (stator core 321) when a candidate solution included in one or more candidate solution groups of the set excitation waveform is applied to the motor M. The excitation waveform determination device 100 determines the excitation waveform based on the results of the electromagnetic field analysis. Therefore, it is possible to determine the time waveform of the excitation signal that can effectively suppress vibration of the motor M.

[0090] In this embodiment, the excitation waveform determining device 100 calculates values ​​of evaluation indices including an electromagnetic force evaluation index for evaluating the value of the electromagnetic force generated in the stator 320 (stator core 321) based on the results of the electromagnetic field analysis, and determines the excitation waveform based on the calculated evaluation index values. Therefore, the excitation waveform can be determined based on objective index values. Therefore, it is possible to determine the time waveform of the excitation signal that can more reliably suppress vibration of the motor M.

[0091] In the present embodiment, the excitation waveform determining device 100 uses the electromagnetic force calculation value F as the value of the electromagnetic force evaluation index for evaluating the value of the electromagnetic force generated in the stator 320 (the stator core 321). c and the electromagnetic force reference value F s The excitation waveform is determined using the value of an evaluation index that evaluates the difference between the fundamental wave and the electromagnetic force generated in the stator 320 (stator core 321) of the motor M. Therefore, the excitation waveform can be determined based on the result of evaluating how much the electromagnetic force generated in the stator 320 (stator core 321) of the motor M can be reduced compared to the case where the motor M is excited with the fundamental wave.

[0092] In this embodiment, the excitation waveform determining device 100 performs an electromagnetic field analysis to obtain the electromagnetic force reference value F s Therefore, it is possible to use an accurate electromagnetic force as the electromagnetic force generated in the stator 320 (stator core 321) of the motor M when the motor M is excited with the fundamental wave.

[0093] Furthermore, in this embodiment, the excitation waveform determination device 100 executes an electromagnetic field analysis to calculate the electromagnetic force generated in the stator 320 (stator core 321) and the torque generated in the motor M when the candidate solution is supplied to the stator coil 322 of the motor M. Therefore, the excitation waveform can be determined taking into consideration not only the electromagnetic force generated in the stator 320 (stator core 321) but also the torque generated in the motor M. Therefore, it is possible to determine the time waveform of the excitation signal that can more effectively suppress vibration of the motor M.

[0094] In the present embodiment, the excitation waveform determination device 100 uses the calculated torque value T c and the torque reference value T s The excitation waveform is determined using the value of the evaluation index that evaluates the difference between the fundamental wave and the root mean square wave. Therefore, it is possible to determine an excitation waveform whose effective value does not deviate significantly from the fundamental wave. In this embodiment, the excitation waveform determination device 100 performs an electromagnetic field analysis to determine the torque reference value T sTherefore, an accurate torque can be used as the torque generated in the motor M when the motor M is excited by the fundamental wave.

[0095] In addition, in this embodiment, the excitation waveform determining device 100 acquires a harmonic superimposition condition HC including a harmonic order n (n is an integer equal to or greater than 2) that is information specifying the order of a harmonic to be superimposed on a fundamental wave included in the excitation waveform, and sets a candidate solution in which harmonics of orders n and less than n are superimposed on the fundamental wave. Therefore, it is possible to set candidates for the excitation waveform without limiting the order of the harmonic to a specific order. Therefore, it is possible to determine a time waveform of an excitation signal that can more effectively suppress vibration of the motor M.

[0096] In addition, in this embodiment, the excitation waveform determination device 100 sets new candidate solutions by a metaheuristics method, and therefore can determine a time waveform of an excitation signal that can effectively suppress vibration of the motor M without theoretical or phenomenological considerations.

[0097] In addition, in this embodiment, the excitation waveform determination device 100 determines the excitation waveform for each fundamental wave condition BC. Therefore, even if the operating conditions of the motor M corresponding to the fundamental wave condition BC change, it is possible to determine the time waveform of the excitation signal that can effectively suppress vibration of the motor M under each operating condition.

[0098] Furthermore, in this embodiment, the motor driving device 200 acquires optimal waveform identification information corresponding to the operating conditions OC when the motor M is in operation from among the optimal waveform identification information that identifies the excitation waveform determined for each fundamental wave condition BC by the excitation waveform determination device 100. The motor driving device 200 generates an excitation signal for exciting the motor M based on the acquired optimal waveform identification information. Therefore, vibration of the motor M can be effectively suppressed regardless of the operating conditions OC when the motor M is in operation.

[0099] [Variations] In this embodiment, the calculated electromagnetic force F c and the electromagnetic force reference value Fs In this embodiment, the difference between the calculated torque value T c and the torque reference value T s The difference between the calculated electromagnetic force F and the calculated electromagnetic force F is evaluated using the constraint equation (6). However, this is not necessarily required. c and the electromagnetic force reference value F s and the calculated torque T c and the torque reference value T s The difference between may be evaluated using the following equation (7):

[0100]

number

[0101] In equation (7), w1 and w2 are weighting coefficients having positive values. The weighting coefficients w1 and w2 are the weighting coefficients of the electromagnetic force calculation value F c and the electromagnetic force reference value F s Evaluation of the difference between the calculated torque and the calculated torque T c and the torque reference value T s This is a preset coefficient to balance the evaluation of the difference between the calculated electromagnetic force F c and the electromagnetic force reference value F s The difference between this is the calculated torque value T c and the torque reference value T s If the difference between the weighting coefficient w1 and the weighting coefficient w2 is more important than the difference between the weighting coefficient w1 and the weighting coefficient w2, the value of the weighting coefficient w1 is made larger than the value of the weighting coefficient w2. When the evaluation function J in equation (7) is used, the constraint equation in equation (6) is not necessary.

[0102] Furthermore, in equations (5) and (7), the optimization problem is a minimization problem for finding the minimum value of the evaluation function J. However, this is not necessarily the case. For example, the evaluation function J may be an evaluation function obtained by multiplying the entire right-hand side of equations (5) and (7) by (-1). In this case, the optimization problem becomes a maximization problem for finding the maximum value of the evaluation function J.

[0103] In addition, in the present embodiment, a case has been exemplified in which the excitation waveform determining device 100 (candidate solution setting unit 103) sets a plurality of candidate solutions as candidate solutions. However, the number of candidate solutions set by the excitation waveform determining device 100 (candidate solution setting unit 103) may be one. In this case, for example, when an electromagnetic force or torque generated in the stator 320 (stator core 321) when the excitation waveform of a candidate solution is supplied to the motor M is lower than a threshold value, the excitation waveform determining device 100 may determine the candidate solution as the excitation waveform to be supplied to the motor M.

[0104] The excitation waveform determining device, the motor driving device, the excitation waveform determining method, and the motor driving method described in the embodiments of the present invention can be realized by a computer executing a program. A computer-readable recording medium having the program recorded thereon and a computer program product such as the program can also be applied as an embodiment of the present invention. The computer-readable recording medium refers to a non-transient recording medium. A non-transient recording medium is, for example, a recording medium that can continue to record data even if no power is supplied to the recording medium from an external source. Examples of non-transient recording media that can be used include flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, magnetic tapes, non-volatile memory cards, ROMs, and the like. The embodiments of the present invention may be realized by a PLC (Programmable Logic Controller) or by dedicated hardware such as an ASIC (Application Specific Integrated Circuit). Furthermore, the above-described embodiments of the present invention are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features. [Industrial Applicability]

[0105] The present invention can be used, for example, to drive a motor.

Claims

1. An excitation waveform determination device that determines an excitation waveform, which is a time waveform of an excitation signal supplied to a stator coil of a motor, comprising: a candidate solution setting unit that sets a candidate solution group including one or more candidate solutions of the excitation waveform; an electromagnetic field analysis unit that calculates an electromagnetic force generated in a stator of the motor when the candidate solution included in the candidate solution group is supplied to the motor by performing an electromagnetic field analysis; an excitation waveform determination unit that determines the excitation waveform based on a result of the electromagnetic field analysis performed by the electromagnetic field analysis unit; Equipped with The candidate solution setting unit an initial candidate solution setting unit that sets an initial group of candidate solutions based on a fundamental wave condition that is information that specifies a fundamental wave of the excitation waveform and a harmonic superposition condition that is information that specifies a harmonic to be superposed on the fundamental wave; a candidate solution update unit that sets a new candidate solution group from the input candidate solution group, The excitation waveform determination unit is an excitation waveform determination device that determines the excitation waveform from among the initial candidate solution group or the new candidate solution group.

2. The excitation waveform determination unit is an evaluation unit that calculates, based on a result of the electromagnetic field analysis, values ​​of evaluation indexes including an electromagnetic force evaluation index for evaluating a value of an electromagnetic force generated in the stator by the candidate solution; A determination unit that determines the excitation waveform based on the value of the evaluation index calculated by the evaluation unit; 2. The excitation waveform determining device according to claim 1, further comprising:

3. 3. The excitation waveform determining device according to claim 2, wherein the electromagnetic force evaluation index is an index for evaluating a difference between an electromagnetic force calculation value, which is an electromagnetic force generated in the stator by the candidate solution calculated by the electromagnetic field analysis unit, and an electromagnetic force reference value, which is an electromagnetic force generated in the stator when the fundamental wave excitation signal is supplied to a stator coil of the motor.

4. 4. The excitation waveform determining device according to claim 3, further comprising a reference value calculation unit that calculates the electromagnetic force reference value by performing an electromagnetic field analysis.

5. The excitation waveform determination device according to any one of claims 1 to 4, wherein the electromagnetic field analysis unit further calculates a torque generated in the motor when the candidate solution of the excitation waveform included in the group of candidate solutions is supplied to a stator coil of the motor by executing the electromagnetic field analysis.

6. The excitation waveform determination unit is an evaluation unit that calculates, based on a result of the execution of the electromagnetic field analysis, values ​​of evaluation indexes including a torque evaluation index for evaluating a value of a torque generated in the motor by the candidate solution; A determination unit that determines the excitation waveform based on the value of the evaluation index calculated by the evaluation unit, 6. The excitation waveform determination device according to claim 5, wherein the torque evaluation index is an index for evaluating a difference between a torque calculation value, which is a torque generated in the motor by the candidate solution calculated by the electromagnetic field analysis unit, and a torque reference value, which is a torque corresponding to an amplitude of the excitation signal of the fundamental wave.

7. The harmonic superposition condition includes a harmonic order that is information for specifying an order of the harmonic, 5. The excitation waveform determination device according to claim 1, wherein the initial group of candidate solutions includes candidate solutions in which harmonics of orders n and less than n are superimposed on a fundamental wave, where the harmonic order is n (n is an integer equal to or greater than 2).

8. 5. The excitation waveform determining device according to claim 1, wherein the candidate solution updating unit sets the new candidate solution by a metaheuristics technique.

9. the electromagnetic field analysis unit calculates, for each fundamental wave condition, an electromagnetic force generated in the stator when the candidate solution included in the candidate solution group is supplied to a stator coil of the motor by performing an electromagnetic field analysis; The excitation waveform determination device according to any one of claims 1 to 4, wherein the excitation waveform determination unit determines the excitation waveform for each fundamental wave condition based on a result of the electromagnetic field analysis performed by the electromagnetic field analysis unit.

10. A motor drive device that drives a motor, An operating condition acquisition unit that acquires operating conditions during operation of the motor; an excitation waveform acquisition unit that acquires information that identifies the excitation waveform determined for each fundamental wave condition by the excitation waveform determination device according to any one of claims 1 to 4, the information identifying the excitation waveform that corresponds to the operating condition acquired by the operating condition acquisition unit during operation of the motor; an excitation signal generating unit that generates an excitation signal for exciting the motor based on information that specifies the excitation waveform acquired by the excitation waveform acquiring unit; A motor drive device comprising:

11. An excitation waveform determination method for determining an excitation waveform, which is a time waveform of an excitation signal supplied to a stator coil of a motor, comprising the steps of: a candidate solution setting step of setting a candidate solution group including one or more candidate solutions of the excitation waveform; an electromagnetic field analysis step of calculating, by performing an electromagnetic field analysis, an electromagnetic force generated in a stator of the motor when the candidate solution included in the candidate solution group is supplied to the motor; an excitation waveform determination step of determining the excitation waveform based on a result of the electromagnetic field analysis performed in the electromagnetic field analysis step; Equipped with The candidate solution setting step includes: an initial candidate solution setting step of setting an initial group of candidate solutions based on a fundamental wave condition, which is information for specifying a fundamental wave of the excitation waveform, and a harmonic superposition condition, which is information for specifying a harmonic to be superposed on the fundamental wave; a candidate solution updating step of setting a new group of candidate solutions from the input group of candidate solutions, The excitation waveform determining step is an excitation waveform determining method for determining the excitation waveform from among the initial candidate solution group or the new candidate solution group.

12. A motor driving method for driving a motor, comprising: An operating condition acquisition step of acquiring operating conditions during operation of the motor; an excitation waveform acquisition step of acquiring information that identifies the excitation waveform determined for each fundamental wave condition by the excitation waveform determination method according to claim 11, the information identifying the excitation waveform that corresponds to the operating condition during operation of the motor acquired by the operating condition acquisition step; an excitation signal generating step of generating an excitation signal for exciting the motor based on information for identifying the excitation waveform acquired in the excitation waveform acquiring step; A motor driving method comprising:

13. A program for causing a computer to function as each unit of the excitation waveform determining device according to any one of claims 1 to 4.

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