Calculation method, calculation device, and program

Abstract

The objective is to provide a calculation method, calculation device, and program that can reduce the time required for simulation. [Solution] The calculation method of the embodiment includes: performing a first simulation of driving a controlled object in a first drive pattern using a simulation model in which the element model is a model in which the electrical characteristics of a switching element are represented by resistance characteristics; extracting first time-series data of the drive signal output from the control model in the first simulation; and performing a second simulation of driving a controlled object in a first drive pattern using a simulation model in which the control model is a model that outputs the first time-series data in a time series, and the element model is a model that can output power loss including switching loss that occurs when the state of a switching element is switched.

Description

Technical Field

[0001] Embodiments of the present invention relate to an arithmetic method, an arithmetic device, and a program.

Background Art

[0002] In a circuit including a switching element, it is necessary to verify in advance by simulation the temperature of the switching element when the circuit operates. In this simulation, the more detailed the model of the circuit including the switching element is, the more accurately the temperature of the switching element when the circuit operates can be calculated. However, there has been a problem that the time required for the simulation increases as the model of the circuit becomes more detailed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide an arithmetic method, an arithmetic device, and a program capable of shortening the time required for simulation.

Means for Solving the Problems

[0005] The calculation method of the embodiment is a computer-based calculation method. The calculation method of the embodiment includes performing a calculation that includes a simulation using a simulation model having an element model corresponding to a switching element and a control model corresponding to a control unit that drives the switching element to control a controlled object. Performing the calculation includes: performing a first simulation of driving the controlled object in a first drive pattern using the simulation model in which the element model is a model in which the electrical characteristics of the switching element are represented by resistance characteristics; extracting first time-series data of the drive signal output from the control model in the first simulation; and performing a second simulation of driving the controlled object in a first drive pattern using the simulation model in which the control model is a model that outputs the first time-series data in a time series, and the element model is a model that can output power loss including switching loss that occurs when the state of the switching element is switched. [Brief explanation of the drawing]

[0006] [Figure 1] A block diagram showing the configuration of the arithmetic unit in the first embodiment. [Figure 2] A diagram showing an example of a motor system to be simulated in the first embodiment. [Figure 3] A figure showing an example of a simulation model in the first embodiment. [Figure 4] A figure showing another example of the simulation model in the first embodiment. [Figure 5] A figure showing an example of a detailed element model in the first embodiment. [Figure 6] A figure showing an example of a simplified element model in the first embodiment. [Figure 7] A graph showing an example of a drive signal output from the control model in the first embodiment. [Figure 8] A flowchart showing an example of the processing performed by the arithmetic unit in the first embodiment. [Figure 9] A graph showing an example of the first drive pattern in the first embodiment. [Figure 10] This figure shows an example of the switching operation of a simplified element model in the pre-simulation of the first embodiment. [Figure 11] This figure shows an example of the switching operation of the detailed element model in the main simulation of the first embodiment. [Figure 12] A graph showing an example of the temperature change of the element model calculated in the main simulation of the first embodiment. [Figure 13] A graph showing an example of the noise level of electromagnetic interference noise calculated in the main simulation in the first embodiment. [Figure 14] A diagram showing an example of a motor system to be simulated in the second embodiment. [Figure 15] A figure showing an example of a simulation model in the second embodiment. [Figure 16] A figure showing another example of the simulation model in the second embodiment. [Figure 17] A figure showing yet another example of the simulation model in the second embodiment. [Figure 18A] A flowchart showing a part of an example of the processing performed by the calculation unit in the second embodiment. [Figure 18B] A flowchart showing another part of an example of the processing performed by the arithmetic unit in the second embodiment. [Figure 18C] A flowchart showing yet another example of the processing performed by the arithmetic unit in the second embodiment. [Figure 19] A graph showing an example of a first drive pattern and an example of a second drive pattern in the second embodiment. [Figure 20] A diagram showing an example of a heating table in the second embodiment. [Figure 21] A figure showing an example of a noise table in the second embodiment. [Modes for carrying out the invention]

[0007] Hereinafter, an arithmetic method, an arithmetic device, and a program according to an embodiment will be described with reference to the drawings.

[0008] (First Embodiment) FIG. 1 is a block diagram showing the configuration of an arithmetic device ******** in the first embodiment. The arithmetic device 100 shown in FIG. 1 is a computer that can execute various arithmetic operations. The arithmetic device 100 is a circuit simulator device that can execute circuit simulations. As shown in FIG. 1, the arithmetic device 100 includes an arithmetic device main body 10, an input unit 20, and a display unit 30. The arithmetic device main body 10 is a computer main body. The input unit 20 is a part for the user of the arithmetic device 100 to input various information to the arithmetic device main body 10. The input unit 20 is, for example, a keyboard and a pointing device connected to the arithmetic device main body 10. The display unit 30 is a part for displaying the output from the arithmetic device main body 10. The display unit 30 is, for example, a display connected to the arithmetic device main body 10.

[0009] The arithmetic device main body 10 has an arithmetic unit 40 and a storage unit 50. The arithmetic unit 40 is a part that executes various arithmetic operations. The arithmetic unit 40 is, for example, a microprocessor such as a CPU. The arithmetic unit 40 executes, for example, a program stored in the storage unit 50 and executes various arithmetic operations. The arithmetic unit 40 executes an arithmetic operation including a simulation using a simulation model 70 corresponding to the motor system 60 shown in FIG. 2. In other words, the arithmetic method by the arithmetic unit 40 includes executing an arithmetic operation including a simulation using the simulation model 70.

[0010] It should be noted that there is an unclear "********" in the original text of ID=10. I have translated it as accurately as possible based on the context. If there is a specific correct content for this part, it can be adjusted accordingly.Figure 2 shows an example of a motor system 60 to be simulated. As shown in Figure 2, the motor system 60 includes a motor 61, a driven device 62, an inverter circuit 63, and a control unit 64. The motor 61 is, for example, a motor supplied with three-phase alternating current from the inverter circuit 63. In the first embodiment, the motor 61 is a controlled object controlled by the control unit 64. The driven device 62 is driven by the motor 61. The driven device 62 can be any device as long as at least a part of it is driven by the motor 61. Examples of the driven device 62 include the pump mechanism of an electric pump and an electric power steering device. The inverter circuit 63 has a plurality of switching elements 66. The plurality of switching elements 66 are transistors. The plurality of switching elements 66 are, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). The plurality of switching elements 66 are, for example, N-channel type MOSFETs. The plurality of switching elements 66 may also be P-channel type MOSFETs. In Figure 2, among the circuit symbols representing each switching element 66, the symbol indicating a diode represents the built-in diode, i.e., the body diode, of the switching element 66, which is a transistor. The switching element 66 may be a transistor other than a MOSFET. For example, the switching element 66 may be a field-effect transistor (FET) other than a MOSFET, or a bipolar transistor such as an insulated-gate bipolar transistor (IGBT). The inverter circuit 63 has six switching elements 66. The six switching elements 66 include two switching elements 66 that constitute the U-phase leg, two switching elements 66 that constitute the V-phase leg, and two switching elements 66 that constitute the W-phase leg.

[0011] The control unit 64 controls the motor 61 by driving a plurality of switching elements 66. The control unit 64 receives a command signal CS from a higher-level device (not shown). Based on the command signal CS, the control unit 64 switches the state of each switching element 66 between the ON state and the OFF state by inputting a gate voltage Vg to each of the plurality of switching elements 66. The command signal CS may also be a signal input to the control unit 64 from the driven device 62. In this case, for example, if the driven device 62 is an electric power steering device and the motor 61 is a motor that assists in providing the torque required for steering wheel operation, the command signal CS input to the control unit 64 from the driven device 62 is the torque command value required according to the steering wheel operation.

[0012] The motor current I flowing through the motor 61 is fed back to the control unit 64. In the first embodiment, the motor current I includes a U-phase current Iu, a V-phase current Iv, and a W-phase current Iw. The U-phase current Iu, V-phase current Iv, and W-phase current Iw are detected, for example, by ammeters installed on the wiring through which the currents of each phase flow. The U-phase current Iu, V-phase current Iv, and W-phase current Iw may be detected in any way. The motor speed N is fed back to the control unit 64 as the output of the motor 61.

[0013] As shown in Figure 1, the calculation unit 40 has a model generation unit 41 that generates a simulation model 70. The model generation unit 41 generates the simulation model 70 by combining models corresponding to each part of the motor system 60. Figure 3 is a diagram showing an example of the simulation model 70 in the first embodiment. Figure 4 is a diagram showing another example of the simulation model 70 in the first embodiment. As shown in Figures 3 and 4, the simulation model 70 includes a motor model 71, a mechanical model 72, an inverter circuit model 73, and a control model 74.

[0014] Motor model 71 is a model corresponding to a motor 61 to which motor current I is supplied from an inverter circuit 63. Motor model 71 is a model corresponding to a motor 61 to which three-phase alternating current is supplied from an inverter circuit 63. Mechanical model 72 is a model corresponding to a driven device 62 driven by the motor 61. Inverter circuit model 73 is a model corresponding to an inverter circuit 63 having a plurality of switching elements 66. Inverter circuit model 73 has a plurality of element models 76. The plurality of element models 76 are models corresponding to each of the plurality of switching elements 66. The plurality of element models 76 are models corresponding to transistors. The plurality of element models 76 are models corresponding to MOSFETs, for example. The inverter circuit model 73 in the first embodiment has six element models 76. The six element models 76 include two element models 76 corresponding to the two switching elements 66 that make up the U-phase leg, two element models 76 corresponding to the two switching elements 66 that make up the V-phase leg, and two element models 76 corresponding to the two switching elements 66 that make up the W-phase leg. The control model 74 is a model corresponding to the control unit 64 that controls the motor 61, which is the object to be controlled.

[0015] In the first embodiment, the model generation unit 41 generates two simulation models 70: a first simulation model 70A shown in Figure 3 and a second simulation model 70B shown in Figure 4. As shown in Figure 3, in the first simulation model 70A, the element model 76 is a simplified element model 76S, and the inverter circuit model 73 is a simplified inverter circuit model 73S. In the first simulation model 70A, the control model 74 is a detailed control model 74D. The first simulation model 70A has a command value input unit 75 that inputs a command signal CS to the detailed control model 74D. As shown in Figure 4, in the second simulation model 70B, the element model 76 is a detailed element model 76D, and the inverter circuit model 73 is a detailed inverter circuit model 73D. In the second simulation model 70B, the control model 74 is a simplified control model 74S. Unlike the first simulation model 70A, the second simulation model 70B does not have a command value input unit 75.

[0016] Figure 5 shows an example of the detailed element model 76D. The detailed element model 76D shown in Figure 5 is a model capable of reproducing the electrical characteristics in the transient response when the state of the switching element 66 is switched. In the first embodiment, the detailed element model 76D is a model capable of reproducing the operation including the transient response when the MOSFET is switched. The detailed element model 76D is a model in which information for calculating the transient response of the MOSFET is defined as electrical characteristics, such as the capacitance Cgs, Cgd of the oxide film of the switching element 66, the junction capacitance Cds of the built-in diode, i.e., the body diode, switching time information, and threshold voltage VGS. The detailed element model 76D is a model capable of outputting power loss, including switching loss that occurs when the state of the switching element 66 is switched.

[0017] As shown in Figure 5, the detailed element model 76D includes an element body model 76a, a gate resistance model 76g, and a voltage source model 76v. The element body model 76a is a model that defines information for calculating the transient response of the MOSFET. In Figure 5, the circuit symbol for the element body model 76a that indicates a diode represents the MOSFET's built-in diode, i.e., the body diode. The element body model 76a is, for example, a SPICE (Simulation Program with Integrated Circuit Emphasis) model with various parameters provided. The gate resistance model 76g is a model corresponding to the gate resistance connected to the gate of the switching element 66. The voltage source model 76v is a model corresponding to a voltage source that applies a gate voltage between the gate and source of the switching element 66. The voltage source model 76v converts the drive signal GS input from the control model 74 into a voltage and applies it as a gate voltage Vg between the gate and source of the element body model 76a.

[0018] Figure 6 shows an example of the simplified element model 76S. The simplified element model 76S is represented as a simple switch model that can reproduce the switching between the ON and OFF states of the switching element 66. The simplified element model 76S is a model in which the transient response when the switching element 66 is switched between the ON and OFF states is not calculated. The simplified element model 76S is a model in which the electrical characteristics of the switching element 66 are represented by resistance characteristics. A "model in which the electrical characteristics of the switching element 66 are represented by resistance characteristics" means, for example, that the information necessary to calculate the transient response of the switching element 66 is not specified, and the electrical characteristics of the switching element 66 are specified as resistance characteristics of the switching element 66, where the resistance value changes between the ON and OFF states.

[0019] As shown in Figure 6, the simplified element model 76S includes a first resistor 76r1, a second resistor 76r2, and a switch 76w. The first resistor 76r1 and the second resistor 76r2 are positioned between the drain and the source. The switch 76w can switch the state of the simplified element model 76S between a state where the drain and source are connected via the first resistor 76r1 and a state where the drain and source are connected via the second resistor 76r2. The state of the switch 76w is switched according to the drive signal GS input from the control model 74. The resistance value of the first resistor 76r1 is the resistance value of the switching element 66 when it is in the ON state. The resistance value of the second resistor 76r2 is the resistance value of the switching element 66 when it is in the OFF state. Therefore, by switching the switch 76w based on the drive signal GS, it is possible to reproduce the operation in which the state of the simplified element model 76S is switched and the resistance value of the simplified element model 76S changes. The resistance value of the second resistor 76r2 is greater than the resistance value of the first resistor 76r1. In the example in Figure 6, the state in which the switch 76w connects the drain and the first resistor 76r1 is shown by a solid line, and the state in which the switch 76w connects the drain and the second resistor 76r2 is shown by a dashed line.

[0020] The detailed control model 74D is a model capable of controlling the motor model 71 and inverter circuit model 73 in the same way that the control unit 64 controls the motor 61 and inverter circuit 63. As shown in Figure 3, in the first embodiment, the detailed control model 74D controls the motor model 71 and inverter circuit model 73 based on the command signal CS from the command value input unit 75. The motor current I and motor speed N are input to the detailed control model 74D. The detailed control model 74D controls the motor model 71 and inverter circuit model 73 by feedback control, in which the motor current I and motor speed N are fed back. In the first embodiment, the detailed control model 74D controls the motor model 71 and inverter circuit model 73 by pulse width modulation control (PWM). The detailed control model 74D inputs a drive signal GS to the inverter circuit model 73 that switches the state of element model 76 between an ON state and an OFF state based on the command signal CS and the fed-back motor current I and motor speed N. The detailed control model 74D generates multiple drive signals GS that are input to each of the multiple element models 76, and inputs these multiple drive signals GS to each of the multiple element models 76.

[0021] The simplified control model 74S outputs the first time-series data DC1 of the drive signal GS obtained by the pre-simulation SM1a described later using the detailed control model 74D, in a time-series manner, without being affected by inputs from other models, as the drive signal GS output to the inverter circuit model 73. The command signal CS, motor current I, and motor rotation speed N are not input to the simplified control model 74S.

[0022] Figure 7 is a graph showing an example of a drive signal GS output from control model 74. In the graph in Figure 7, the vertical axis represents the signal level, and the horizontal axis represents time t. The drive signal GS is, for example, a square wave that can be switched between 1 (high) and 0 (low). When the drive signal GS input to element model 76 is 1, element model 76 is in the ON state. When the drive signal GS input to element model 76 is 0, element model 76 is in the OFF state. If element model 76 is detailed element model 76D, when the drive signal GS is 1, the voltage source model 76v sets the voltage applied between the gate and source of detailed element model 76D to a predetermined voltage value that is greater than or equal to the threshold voltage. If element model 76 is detailed element model 76D, when the drive signal GS is 0, the voltage source model 76v sets the voltage applied between the gate and source of detailed element model 76D to a predetermined voltage value that is less than the threshold voltage. If element model 76 is the simplified element model 76S, when the drive signal GS is 1, the switch section 76w connects the drain to the first resistor section 76r1. If element model 76 is the simplified element model 76S, when the drive signal GS is 0, the switch section 76w connects the drain to the second resistor section 76r2.

[0023] As shown in Figures 3 and 4, in both the first simulation model 70A and the second simulation model 70B, the mechanical model 72 is the detailed mechanical model 72D. The detailed mechanical model 72D is a model created by modeling each part that constitutes the driven device 62, and is a model that can calculate the load that the driven device 62 applies to the motor 61 in response to the input from the motor 61. The detailed mechanical model 72D applies the calculated load to the motor model 71.

[0024] As shown in Figure 1, the calculation unit 40 includes an execution processing unit 42 and an output unit 43. The execution processing unit 42 is the part that executes a simulation using the simulation model 70 generated in the model generation unit 41. In the first embodiment, the execution processing unit 42 can execute a pre-simulation SM1a using the first simulation model 70A and a main simulation SM1b using the second simulation model 70B. In the first embodiment, the pre-simulation SM1a corresponds to the "first simulation". In the first embodiment, the main simulation SM1b corresponds to the "second simulation".

[0025] The output unit 43 is the part that outputs the processing results of the execution processing unit 42. The output unit 43 outputs the processing results of the execution processing unit 42 to the storage unit 50. For example, the output unit 43 outputs the processing results of the execution processing unit 42 to the storage unit 50 at each time step. The output unit 43 generates a display image based on the processing results of the execution processing unit 42. The output unit 43 outputs the display image to the display unit 30.

[0026] Figure 8 is a flowchart showing an example of the processing performed by the calculation unit 40 in the first embodiment. The processing flow shown in Figure 8 is a flow that performs a simulation of operating the motor 61 in the motor system 60 with a certain drive pattern, and estimates the temperature change of the switching element 66 and the noise level of electromagnetic interference noise (EMI noise) generated in the motor system 60 due to the switching element 66 based on the simulation.

[0027] As shown in Figure 8, the calculation unit 40 generates a first simulation model 70A (step S101). In the first embodiment, the calculation unit 40 generates the first simulation model 70A with the help of a model generation unit 41. The model generation unit 41 may generate the first simulation model 70A by selecting models for each part of the motor system 60, or it may generate the first simulation model 70A by replacing the element model 76 in the detailed simulation model 70 corresponding to the motor system 60 with a simplified element model 76S.

[0028] The calculation unit 40 performs a pre-simulation SM1a using the first simulation model 70A (step S102). In the first embodiment, the calculation unit 40 performs the pre-simulation SM1a using the execution processing unit 42. The pre-simulation SM1a is a simulation of the control unit 64 driving the motor 61 with the first drive pattern DP1. In other words, in the calculation method of the first embodiment, performing the calculation includes performing a pre-simulation SM1a of the motor 61 being driven with the first drive pattern DP1 using the first simulation model 70A, in which the element model 76 is a simplified element model 76S. The time step size in the pre-simulation SM1a is larger than the time step size in the main simulation SM1b. The time step size in the pre-simulation SM1a is a coarse time step size within a range that can reproduce the control operation using the first simulation model 70A. For example, the time step size in the pre-simulation SM1a is about 5 times or more and 30 times or less than the time step size in the main simulation SM1b.

[0029] Figure 9 is a graph showing an example of the first drive pattern DP1. In the graph in Figure 9, the vertical axis represents the motor rotation speed N, and the horizontal axis represents time t. In the example in Figure 9, the first drive pattern DP1 is a drive pattern in which the motor 61 is driven so that the motor rotation speed N increases linearly from zero to rotation speed Na, is maintained at a constant level for a certain period of time, and then decreases linearly again to zero.

[0030] As shown in Figure 3, in the pre-simulation SM1a, the inverter circuit model 73 is a simplified inverter circuit model 73S, the element model 76 is a simplified element model 76S, and the control model 74 is a detailed control model 74D. In the pre-simulation SM1a, the command signal CS necessary to drive the motor 61 with the first drive pattern DP1 is input to the detailed control model 74D from the command value input unit 75. In the pre-simulation SM1a, the motor current I and motor rotation speed N are fed back to the detailed control model 74D.

[0031] In the pre-simulation SM1a, the detailed control model 74D generates a drive signal GS, as shown in Figure 7, for each of the multiple simplified element models 76S based on the input command signal CS, and inputs it to each simplified element model 76S. Each simplified element model 76S is switched between an ON state and an OFF state based on the input drive signal GS. Figure 10 shows an example of the switching operation of the simplified element model 76S in the pre-simulation SM1a. The top graph in Figure 10 shows the change in the drive signal GS. The second graph from the top in Figure 10 shows the change in the gate voltage Vg of the simplified element model 76S. The third graph from the top in Figure 10 shows the change in the drain current Id flowing through the simplified element model 76S. The bottom graph in Figure 10 shows the change in the drain-source voltage Vds of the simplified element model 76S. In each graph in Figure 10, the horizontal axis represents time t. The simplified element model 76S is a model in which the gate voltage Vg, drain current Id, and drain-source voltage Vds change based on the input drive signal GS, as shown in Figure 10.

[0032] As shown in Figure 10, in the pre-simulation SM1a, at the moment the drive signal GS changes from 0 (low) to 1 (high), the gate voltage Vg changes from voltage VgL to voltage VgH, which is higher than the threshold voltage. Voltage VgL is a voltage lower than the threshold voltage, for example, 0[V]. Voltage VgL can be any value as long as it is lower than the threshold voltage. The gate voltage Vg is maintained at a constant voltage VgH while the drive signal GS is 1. In the pre-simulation SM1a, at the moment the drive signal GS changes from 0 to 1, the switch section 76w of the simplified element model 76S switches from a state where the drain and source are connected via the second resistor section 76r2 to a state where the drain and source are connected via the first resistor section 76r1. This reproduces the operation of the simplified element model 76S changing from the OFF state to the ON state. In the pre-simulation SM1a, the moment the simplified element model 76S is turned ON, the drain-source resistance of the simplified element model 76S becomes the resistance of the first resistor 76r1, and a drain current Id flows at value Ida. Also in the pre-simulation SM1a, the moment the simplified element model 76S is turned ON, the drain-source voltage Vds changes from voltage VdsH to a voltage lower than VdsH, VdsL. While the drive signal GS is 1, the drain current Id flows at a constant value Ida, and the drain-source voltage Vds is maintained at a constant voltage VdsL.

[0033] In the pre-simulation SM1a, the gate voltage Vg changes from voltage VgH to voltage VgL the moment the drive signal GS changes from 1 (high) to 0 (low). The gate voltage Vg is maintained at a constant voltage VgL while the drive signal GS is 0. In the pre-simulation SM1a, the moment the drive signal GS changes from 1 to 0, the switch section 76w of the simplified element model 76S switches from connecting the drain and source via the first resistor section 76r1 to connecting the drain and source via the second resistor section 76r2. This reproduces the operation of the simplified element model 76S changing from the ON state to the OFF state. In the pre-simulation SM1a, the moment the simplified element model 76S turns OFF, the resistance value between the drain and source of the simplified element model 76S becomes the resistance value of the second resistor section 76r2, and the drain current Id stops flowing. Furthermore, in the pre-simulation SM1a, the moment the simplified element model 76S turns OFF, the drain-source voltage Vds changes from voltage VdsL to voltage VdsH. While the drive signal GS is 0, no drain current Id flows, and the drain-source voltage Vds is maintained at a constant voltage VdsH.

[0034] As shown in Figure 8, the calculation unit 40 stores time-series data of the drive signal GS output from the detailed control model 74D in the pre-simulation SM1a (step S103). In step S103, the calculation unit 40 stores, for example, the time-series data of the drive signal GS output from the detailed control model 74D via the output unit 43 in the storage unit 50. The time-series data of the drive signal GS output from the detailed control model 74D is the first time-series data DC1. The first time-series data DC1 includes the time-series data of the drive signals GS input to each of the multiple simplified element models 76S in the pre-simulation SM1a. In step S103, the calculation unit 40 may store the first time-series data DC1 in the storage unit 50 after the pre-simulation SM1a is completed, or it may store the first time-series data DC1 in the storage unit 50 by sequentially storing the drive signal GS data in the storage unit 50 during the execution of the pre-simulation SM1a. Thus, performing calculations in the calculation method of the first embodiment includes extracting the first time-series data DC1 of the drive signal GS output from the control model 74 in the pre-simulation SM1a.

[0035] Here, in the pre-simulation SM1a, the drive signal GS output from the detailed control model 74D is determined based on the command signal CS and the feedback motor current I and motor speed N. The magnitude of the motor current I is not affected, or is almost not affected, by the change in drain current Id in the transient response when the switching element 66 is switched. Therefore, even if the element model 76 in the pre-simulation SM1a is a simplified element model 76S that cannot reproduce the electrical characteristics of the transient response during switching, the motor current I output from the inverter circuit model 73 is the same as, or almost the same as, if the element model 76 is a detailed element model 76D that can reproduce the electrical characteristics of the transient response during switching. The motor speed N is determined by the motor current I input to the motor model 71 and the load received from the mechanical model 72 connected to the motor model 71. In the pre-simulation SM1a, the mechanical model 72 is the detailed mechanical model 72D. Therefore, in the pre-simulation SM1a, the load that motor model 71 receives from mechanical model 72 is the same as the load that motor model 71 receives from mechanical model 72 when simulation model 70 is a fully detailed model, provided the motor current I is the same. Consequently, the motor rotation speed N in the pre-simulation SM1a is the same as, or approximately the same as, the motor rotation speed N when simulation model 70 is a fully detailed model. As a result, in the pre-simulation SM1a using the simplified element model 76S, the drive signal GS output from the detailed control model 74D is the same as, or approximately the same as, the drive signal GS when simulation model 70 is a fully detailed model. In this specification, "a certain parameter is approximately the same as another parameter" includes the fact that the difference between a certain parameter and another parameter is small enough to be negligible as an error.

[0036] The calculation unit 40 stores the first time series data DC1 in the storage unit 50, and then generates a simplified control model 74S based on the first time series data DC1 (step S104). In step S104, the calculation unit 40 generates the simplified control model 74S using the model generation unit 41. In step S104, the model generation unit 41 generates a model that outputs the first time series data DC1 stored in the storage unit 50 in a time series order, as the simplified control model 74S.

[0037] The calculation unit 40 generates a second simulation model 70B using the simplified control model 74S generated in step S104 (step S105). In step S105, the calculation unit 40 generates the second simulation model 70B with the model generation unit 41. In step S105, the model generation unit 41 generates the second simulation model 70B by, for example, replacing the detailed control model 74D of the first simulation model 70A with the simplified control model 74S generated in step S104, and replacing the simplified inverter circuit model 73S of the first simulation model 70A with the detailed inverter circuit model 73D stored in the storage unit 50. In step S105, the model generation unit 41 may also convert the simplified inverter circuit model 73S to the detailed inverter circuit model 73D by replacing each simplified element model 76S of the simplified inverter circuit model 73S with the detailed element model 76D stored in the storage unit 50.

[0038] The calculation unit 40 performs the main simulation SM1b using the second simulation model 70B generated in step S105 (step S106). In other words, performing calculations in the first embodiment includes performing the main simulation SM1b using the second simulation model 70B. In the first embodiment, the calculation unit 40 performs the main simulation SM1b using the execution processing unit 42. The main simulation SM1b, like the pre-simulation SM1a, is a simulation of when the control unit 64 drives the motor 61 with the first drive pattern DP1. The time step size in the main simulation SM1b is smaller than the time step size in the pre-simulation SM1a. The time step size in the main simulation SM1b is fine enough to reproduce the transient response behavior of the detailed element model 76D during switching.

[0039] As shown in Figure 4, in the main simulation SM1b, the inverter circuit model 73 is the detailed inverter circuit model 73D, the element model 76 is the detailed element model 76D, and the control model 74 is the simplified control model 74S. In the main simulation SM1b, the command signal CS, motor current I, and motor speed N are not input to the simplified control model 74S.

[0040] Figure 11 shows an example of the switching operation of the detailed element model 76D in the main simulation SM1b. The top graph in Figure 11 shows the drive signal GS. The second graph from the top in Figure 11 shows the gate voltage Vg of the detailed element model 76D. The third graph from the top in Figure 11 shows the drain current Id flowing through the detailed element model 76D. The bottom graph in Figure 11 shows the drain-source voltage Vds of the detailed element model 76D. In each graph in Figure 11, the horizontal axis represents time t. The detailed element model 76D is a model in which the gate voltage Vg, drain current Id, and drain-source voltage Vds are reproduced based on the input drive signal GS, including the transient response behavior during switching, as shown in Figure 11.

[0041] As shown in Figure 11, in the main simulation SM1b, even when the drive signal GS changes from 0 (low) to 1 (high), the gate voltage Vg does not instantaneously become voltage VgH, but rises with time t according to the value of the gate resistance model 76g, etc., to reach voltage VgH. In the main simulation SM1b, even when the drive signal GS changes from 1 to 0, the gate voltage Vg does not instantaneously become voltage VgL, but falls with time t to reach voltage VgL. Similarly, the drain current Id and drain-source voltage Vds also change with time t in accordance with the change in gate voltage Vg when the drive signal GS is switched between 0 and 1. Although not shown in Figure 11, the drain-source voltage Vds and drain current Id in the main simulation SM1b also reproduce the noise generated during switching.

[0042] When the main simulation SM1b starts, the simplified control model 74S outputs the drive signal GS of the first time series data DC1 in chronological order. In the main simulation SM1b, the calculation unit 40 calculates the power loss occurring in the detailed element model 76D at each time step. The calculation unit 40 calculates the power loss by multiplying the drain current Id by the drain-source voltage Vds. The power loss calculated in the main simulation SM1b includes the switching loss and conduction loss in the element model 76.

[0043] In the main simulation SM1b, the calculation unit 40 calculates the voltage value at a predetermined location in the second simulation model 70B and calculates the voltage waveform at that predetermined location. The predetermined location is not particularly limited as long as it is a location where electromagnetic interference noise caused by the transient response of the voltage generated by the switching operation of the detailed element model 76D can be detected.

[0044] As shown in Figure 8, the calculation unit 40 outputs the results of the main simulation SM1b (step S107). The output results of the main simulation SM1b include a graph showing the temperature change of the detailed element model 76D when the motor model 71 is driven with the first drive pattern DP1, and a graph showing the noise level of electromagnetic interference noise caused by the detailed element model 76D when the motor model 71 is driven with the first drive pattern DP1, for each frequency. The calculation unit 40 calculates the temperature change of the detailed element model 76D for each time step based on the power loss in the detailed element model 76D calculated for each time step in the main simulation SM1b. The calculation unit 40 applies a Fast Fourier Transform (FFT) to the voltage waveform calculated in the main simulation SM1b and calculates the noise level for each frequency. The calculation unit 40 sequentially applies the Fast Fourier Transform to the voltage waveform at predetermined time intervals and calculates the maximum value of the noise level at each frequency as the noise level at that frequency.

[0045] Figure 12 is a graph showing an example of the temperature change of the element model 76 calculated in the main simulation SM1b. In Figure 12, the vertical axis represents the temperature Tj of the element model 76, and the horizontal axis represents time t. Figure 13 is a graph showing an example of the noise level of electromagnetic interference noise calculated in the main simulation SM1b. In Figure 13, the vertical axis represents the noise level [dB], and the horizontal axis represents the frequency [Hz]. The noise level at each frequency in Figure 13 is the maximum value of the noise level calculated for each frequency in the main simulation SM1b. The calculation unit 40 outputs graphs such as those shown in Figures 12 and 13 to the display unit 30 via the output unit 43. By viewing the graphs displayed on the display unit 30, the user can obtain the simulated values ​​of the temperature change of the switching element 66 and the simulated noise level of electromagnetic interference noise when the motor 61 is driven by the first drive pattern DP1.

[0046] According to the first embodiment, the calculation method using the arithmetic unit 100 is a computer calculation method that includes performing calculations including a simulation using a simulation model 70 having an element model 76 corresponding to a switching element 66 and a control model 74 corresponding to a control unit 64 that drives the switching element 66 to control the motor 61. Performing such calculations includes performing a pre-simulation SM1a when the motor 61 is driven in a first drive pattern DP1 using a first simulation model 70A in which the element model 76 is a simplified element model 76S in which the electrical characteristics of the switching element 66 are shown as resistance characteristics; extracting first time-series data DC1 of the drive signal GS output from the control model 74 in the pre-simulation SM1a; and performing a main simulation SM1b when the motor 61 is driven in a first drive pattern DP1 using a second simulation model 70B in which the control model 74 is a simplified control model 74S that outputs the first time-series data DC1 in a time series, and the element model 76 is a detailed element model 76D that can output power loss including switching loss that occurs when the state of the switching element 66 is switched.

[0047] In the pre-simulation SM1a, the element model 76 is a simplified element model 76S in which the electrical characteristics of the switching element 66 are represented by resistance characteristics, so no calculations are performed regarding the transient response of the switching element 66 during switching. As a result, the computational load in the pre-simulation SM1a is smaller than when the element model 76 is the detailed element model 76D. On the other hand, as mentioned above, the drive signal GS output from the control model 74 changes based on the feedbacked motor current I, but the change in the drain current Id in the transient response of the switching element 66 has no effect on the motor current I, or is so small that it can be ignored. Therefore, in the pre-simulation SM1a using the simplified element model 76S, the first time-series data DC1 of the drive signal GS output from the control model 74 can be considered the same as the time-series data of the drive signal GS output from the control model 74 in a simulation where all simulation models 70 are detailed models. In the main simulation SM1b, by changing the control model 74 to a simplified control model 74S that outputs the first time-series data DC1 in chronological order, it is not necessary to perform feedback control in the control model 74 in the main simulation SM1b. Therefore, the computational load in the control model 74 can be reduced in the main simulation SM1b. In addition, in the main simulation SM1b, the element model 76 is a detailed element model 76D that can output power loss including switching loss that occurs when the state of the switching element 66 is switched. Therefore, by inputting the drive signal GS of the first time series data DC1 in chronological order into the detailed element model 76D, it is possible to calculate the power loss that occurs in the switching element 66 when the motor 61 is driven with the first drive pattern DP1. Since the power loss that occurs in the switching element 66 will be the same value if the input to the switching element 66 is the same, by inputting the drive signal GS of the first time series data DC1 into the detailed element model 76D using the simplified control model 74S, it is possible to calculate the same power loss as when the control model 74 was performing feedback control calculations in the pre-simulation SM1a.

[0048] As described above, according to the first embodiment, when performing the main simulation SM1b to reproduce the transient response of the switching element 66 during switching, it is not necessary to perform calculations related to feedback control by the control model 74. The computational load on the calculation unit 40 when reproducing the transient response of the switching element 66 during switching is greater than the computational load on the calculation unit 40 when reproducing other behaviors of the switching element 66. Therefore, if calculations related to feedback control are also performed in the control model 74 when reproducing the transient response, the computational load on the calculation unit 40 will increase synergistically. According to the first embodiment, in the pre-simulation SM1a which performs calculations related to feedback control by the control model 74, the element model 76 is a simplified element model 76S, and the transient response of the switching element 66 is not reproduced. Furthermore, in the main simulation SM1b, which calculates power loss including switching loss during the transient response of the switching element 66 using the detailed element model 76D, the control model 74 is a simplified control model 74S that outputs the first time-series data DC1 obtained in the pre-simulation SM1a in chronological order, and the calculations related to the feedback control of the control unit 64 are not reproduced. In other words, the calculations that reproduce the transient response of the switching element 66 and the calculations that reproduce the feedback control of the control unit 64 are not performed within a single simulation. Therefore, the synergistic increase in the computational load on the calculation unit 40 can be suppressed, and the computational load on the calculation unit 40 can be reduced. Consequently, the time required to simulate the motor system 60 can be shortened. In addition, by performing the main simulation SM1b using the simplified control model 74S that outputs the first time-series data DC1 in chronological order, the same power loss as when the simulation was performed using the detailed simulation model 70 can be calculated. Consequently, a decrease in the accuracy of the simulation results of the temperature change of the switching element 66 based on the power loss can be suppressed. As described above, according to the first embodiment, it is possible to reduce the time required for simulating the motor system 60 while suppressing a decrease in the accuracy of the results calculated by the simulation.

[0049] According to the first embodiment, the time step size in the pre-simulation SM1a is larger than the time step size in the main simulation SM1b. Therefore, the time required for the pre-simulation SM1a can be further reduced. Consequently, the total time required for the simulation of the motor system 60 can be further reduced. For example, if the time step size in the pre-simulation SM1a is 10 times or more than the time step size in the main simulation SM1b, the time required for the pre-simulation SM1a can be more preferably reduced.

[0050] According to the first embodiment, the arithmetic unit 100 includes an arithmetic unit 40 that performs calculations including simulations using a simulation model 70 having an element model 76 corresponding to a switching element 66 and a control model 74 corresponding to a control unit 64 that drives the switching element 66 to control the motor 61. The arithmetic unit 40 performs a pre-simulation SM1a when the motor 61 is driven in the first drive pattern DP1 using a first simulation model 70A in which the element model 76 is a simplified element model 76S in which the electrical characteristics of the switching element 66 are shown as resistance characteristics, and extracts the first time-series data DC1 of the drive signal GS output from the control model 74 in the pre-simulation SM1a. The arithmetic unit 40 performs a main simulation SM1b when the motor 61 is driven in the first drive pattern DP1 using a second simulation model 70B in which the control model 74 is a simplified control model 74S that outputs the first time-series data DC1 in a time series, and the element model 76 is a detailed element model 76D that can output power loss including switching loss that occurs when the state of the switching element 66 is switched. With such a computing device 100, the above-described calculation method can be executed, and the time required for simulating the motor system 60 can be reduced.

[0051] (Second embodiment) In the following description, configurations and methods similar to those in the embodiments described above may be omitted from explanation by using the same reference numerals. Figure 14 shows an example of a motor system 260 to be simulated in the second embodiment.

[0052] As shown in Figure 14, the control unit 264 in the motor system 260 inputs a drive capability control signal AS to the switching element 66 of the inverter circuit 63. The drive capability control signal AS is a signal that changes the characteristics of the switching element 66. In the second embodiment, the drive capability control signal AS is a signal that changes the resistance value of the gate resistor connected to the gate of the switching element 66. The control unit 264 adjusts the drive capability control signal AS output to the switching element 66 based, for example, the magnitude of the motor current I.

[0053] The control unit 264 outputs a drive capability control signal AS to the switching element 66 that increases the resistance value of the gate resistor when the motor current I is above a certain value. When the motor current I is large to a certain extent, the conduction loss in the switching element 66 becomes larger than the switching loss. In this case, even if the switching loss increases due to the increased resistance value of the gate resistor and the longer transient response time, the impact on the power loss generated in the switching element 66 is small. Therefore, when the motor current I is above a certain value, the control unit 264 increases the resistance value of the gate resistor to slow down the change in the drain-source voltage Vds during switching, thereby reducing electromagnetic interference noise.

[0054] The control unit 264 outputs a drive capability control signal AS to the switching element 66 that reduces the resistance value of the gate resistor when the motor current I is less than a certain value. When the motor current I is relatively small, the switching loss in the switching element 66 becomes larger than the conduction loss. Therefore, if the time required for the transient response during switching becomes longer and the switching loss generated in the switching element 66 increases, it has a significant impact on the power loss generated in the switching element 66. Accordingly, when the motor current I is less than a certain value, the control unit 264 reduces the switching loss by reducing the resistance value of the gate resistor and shortening the transient response time during switching. Other aspects of the motor system 260 are the same as other aspects of the motor system 60 in the first embodiment.

[0055] Figure 15 shows an example of the simulation model 70 in the second embodiment. Figure 16 shows another example of the simulation model 70 in the second embodiment. Figure 17 shows yet another example of the simulation model 70 in the second embodiment. In the second embodiment, the model generation unit 41 of the calculation unit 40 generates three simulation models 70: the first simulation model 270A shown in Figure 15, the second simulation model 270B shown in Figure 16, and the third simulation model 270C shown in Figure 17.

[0056] As shown in Figure 15, in the first simulation model 270A, the element model 76 is the simplified element model 76S, and the inverter circuit model 73 is the simplified inverter circuit model 73S. In the first simulation model 270A, the control model 74 is the detailed control model 274D. The detailed control model 274D is the same as the detailed control model 74D in the first embodiment, except that it outputs a drive capability control signal AS to the simplified inverter circuit model 73S. Other aspects of the first simulation model 270A are the same as other aspects of the first simulation model 70A in the first embodiment.

[0057] As shown in Figure 16, in the second simulation model 270B, the element model 76 is the detailed element model 276D, and the inverter circuit model 73 is the detailed inverter circuit model 273D. The detailed element model 276D differs from the detailed element model 76D in the first embodiment shown in Figure 5 in that the gate resistance model 76g is a variable resistor whose resistance value changes according to the drive capability control signal AS. Other aspects of the detailed element model 276D are the same as other aspects of the detailed element model 76D in the first embodiment. In the second simulation model 270B, the control model 74 is the detailed control model 274D. In the second simulation model 270B, the mechanical model 72 is the first simplified mechanical model 272Sa. In the second embodiment, the first simplified mechanical model 272Sa is a model that outputs a load to the motor model 71 due to viscous resistance proportional to the motor rotation speed N. The first simplified mechanical model 272Sa is stored in the storage unit 50 in advance, for example. The second simulation model 270B has a command value input unit 75.

[0058] As shown in Figure 17, in the third simulation model 270C, the element model 76 is the intermediate element model 276M. The intermediate element model 276M is a model in which the gate voltage Vg, drain current Id, and drain-source voltage Vds change in response to the drive signal GS, as shown in Figure 10, similar to the simplified element model 76S. The intermediate element model 276M is a model that outputs the power loss corresponding to the motor current I based on the thermal table HT created in the table generation simulation SM2b described later during switching. In other words, in the second embodiment, the intermediate element model 276M is a model that can output the power loss including the switching loss that occurs when the state of the switching element 66 is switched. Except for having the function of outputting the power loss, the intermediate element model 276M is the same as the simplified element model 76S. In the second embodiment, the intermediate element model 276M is a model that outputs the power loss including the switching loss and the conduction loss. In the third simulation model 270C, the inverter circuit model 73 is an intermediate inverter circuit model 273M in which each element model 76 is an intermediate element model 276M.

[0059] In the third simulation model 270C, the control model 74 is the simplified control model 274S. The simplified control model 274S outputs the third time-series data DC3, which is extracted in the pre-simulation SM2a described later, in a time-series manner, without being affected by inputs from other models. Other aspects of the simplified control model 274S are the same as other aspects of the simplified control model 74S in the first embodiment.

[0060] In the third simulation model 270C, the mechanical model 72 is the second simplified mechanical model 272Sb. The second simplified mechanical model 272Sb is a model that outputs the second time-series data DC2 extracted in the pre-simulation SM2a described later to the motor model 71 in a time-series manner, without relying on input from other models. The third simulation model 270C does not have a command value input unit 75.

[0061] In the second embodiment, the execution processing unit 42 of the calculation unit 40 is capable of executing a pre-simulation SM2a using the first simulation model 270A, a table generation simulation SM2b using the second simulation model 270B, and a main simulation SM2c using the third simulation model 270C. In the second embodiment, the pre-simulation SM2a corresponds to the "first simulation". In the second embodiment, the table generation simulation SM2b corresponds to the "third simulation". In the second embodiment, the main simulation SM2c corresponds to the "second simulation".

[0062] Figure 18A is a flowchart showing a part of an example of the processing performed by the calculation unit 40 in the second embodiment. Figure 18B is a flowchart showing another part of an example of the processing performed by the calculation unit 40 in the second embodiment. Figure 18C is a flowchart showing yet another part of an example of the processing performed by the calculation unit 40 in the second embodiment. The processing flow shown in Figures 18A to 18C is a flow that performs a simulation of operating the motor 61 in the motor system 260 with the first drive pattern DP1, and estimates the temperature change of the switching element 66 and the noise level of electromagnetic interference noise generated in the motor system 60 due to the switching element 66 based on the simulation.

[0063] As shown in Figure 18A, the calculation unit 40 generates a first simulation model 270A (step S201). In the second embodiment, the calculation unit 40 generates the first simulation model 270A using a model generation unit 41. The calculation unit 40 generates the first simulation model 270A in the same manner as in step S101 of the first embodiment. The calculation unit 40 performs a pre-simulation SM2a using the first simulation model 270A (step S202). The pre-simulation SM2a is a simulation of the control unit 64 driving the motor 61 with the first drive pattern DP1. The calculation unit 40 performs the pre-simulation SM2a in the same manner as in step S102 of the first embodiment. The time step in the pre-simulation SM2a is, for example, larger than the time step in the table generation simulation SM2b. The time step in the pre-simulation SM2a is, for example, about 5 times or more and 30 times or less than the time step in the table generation simulation SM2b.

[0064] The calculation unit 40 stores time-series data of the drive signal GS and time-series data of the drive capability control signal AS output from the detailed control model 274D in the pre-simulation SM2a (step S203). In step S203, the calculation unit 40 stores the time-series data of the drive signal GS and time-series data of the drive capability control signal AS output from the detailed control model 274D in the storage unit 50, for example, via the output unit 43. The time-series data of the drive signal GS output from the detailed control model 274D is the first time-series data DC1. The time-series data of the drive capability control signal AS output from the detailed control model 274D is the third time-series data DC3. The third time-series data DC3 includes the time-series data of each drive capability control signal AS input to each of the multiple simplified element models 76S in the pre-simulation SM2a. Thus, performing calculations in the calculation method of the second embodiment includes extracting the third time-series data DC3 of the drive capability control signal AS output from the control model 74 in the pre-simulation SM2a.

[0065] Here, in the pre-simulation SM1a, the drive capability control signal AS output from the detailed control model 74D is determined based on the feedback motor current I. As described above, the magnitude of the motor current I is not affected, or is almost not affected, by the instantaneous change in drain current Id during the transient response when the switching element 66 is switched. Therefore, even if the element model 76 is a simplified element model 76S that cannot reproduce the electrical characteristics of the transient response during switching in the pre-simulation SM2a, the motor current I output from the inverter circuit model 73 is the same as, or almost the same as, the case where the element model 76 is a detailed element model 76D that can reproduce the electrical characteristics of the transient response during switching. Therefore, even in the pre-simulation SM2a using the simplified element model 76S, the drive capability control signal AS that changes based on the motor current I is the same as, or almost the same as, the drive capability control signal AS when the simulation model 70 is a fully detailed model.

[0066] The calculation unit 40 stores time-series data of the load that the detailed mechanical model 72D applies to the motor model 71 in the pre-simulation SM2a (step S204). The time-series data of the load that the detailed mechanical model 72D applies to the motor model 71 is the second time-series data DC2. The second time-series data DC2 is data showing the torque waveform output from the motor model 71. The calculation unit 40 stores the second time-series data DC2 in the storage unit 50, for example, via the output unit 43. Thus, performing calculations in the calculation method of the second embodiment includes extracting the second time-series data DC2 of the load that the mechanical model 72 applies to the motor model 71 in the pre-simulation SM2a. Note that steps S203 and S204 may be performed in either order or simultaneously.

[0067] As shown in Figure 18B, after step S204, the calculation unit 40 generates the second simulation model 270B (step S205). In step S205, the model generation unit 41 of the calculation unit 40 generates the second simulation model 270B by, for example, replacing the simplified inverter circuit model 73S of the first simulation model 270A with the detailed inverter circuit model 273D stored in the storage unit 50 as described above, and replacing the mechanical model 72 of the first simulation model 270A with the first simplified mechanical model 272Sa stored in the storage unit 50 as described above. In step S205, the model generation unit 41 may also replace the simplified element model 76S of the simplified inverter circuit model 73S with the detailed element model 276D to make it the detailed inverter circuit model 273D.

[0068] The calculation unit 40 starts the table generation simulation SM2b using the second simulation model 270B generated in step S205 (step S206). In other words, performing calculations in the calculation method of the second embodiment includes changing the mechanical model 72 in the table generation simulation SM2b to a first simplified mechanical model 272Sa that outputs a load corresponding to the rotational speed of the motor model 71 to the motor model 71.

[0069] The table generation simulation SM2b is a simulation of when the control unit 64 drives the motor 61 with the second drive pattern DP2. The second drive pattern DP2 is a drive pattern in which the motor current I changes. In the second embodiment, the second drive pattern DP2 is a drive pattern that increases the motor current I from zero to the maximum current allowed in the motor system 260. In other words, performing the calculation in the calculation method of the second embodiment includes performing the table generation simulation SM2b when the motor 61 is driven with the second drive pattern DP2 in which the motor current I changes, using the second simulation model 270B, after performing the pre-simulation SM1a and before performing the main simulation SM2c.

[0070] Figure 19 is a graph showing an example of a first drive pattern DP1 and an example of a second drive pattern DP2. The upper graph in Figure 19 shows the first drive pattern DP1. The lower graph in Figure 19 shows the second drive pattern DP2. In the upper graph in Figure 19, the vertical axis represents the motor rotation speed N, and the horizontal axis represents time t. In the lower graph in Figure 19, the vertical axis represents the motor current I, and the horizontal axis represents time t. In the example in Figure 19, the first drive pattern DP1 is the same as the first drive pattern DP1 in the first embodiment. The second drive pattern DP2 shown in the example in Figure 19 is a drive pattern that increases the motor current I from zero to the maximum current Ia. The time ts2 during which the motor 61 is driven in the second drive pattern DP2 is shorter than the time ts1 during which the motor 61 is driven in the first drive pattern DP1. Time ts2 is, for example, less than or equal to one-tenth of time ts1. In the example in Figure 19, the second drive pattern DP2 is shown as a pattern in which the motor current I increases linearly. However, strictly speaking, the second drive pattern DP2 is a drive pattern in which the amplitude of the AC motor current I increases monotonically with time t. The waveform of the motor current I shown in the lower graph of Figure 19 may also be the waveform of the RMS value of the motor current I.

[0071] As shown in Figure 16, in the table generation simulation SM2b, the inverter circuit model 73 is the detailed inverter circuit model 273D, the element model 76 is the detailed element model 276D, the control model 74 is the detailed control model 274D, and the mechanical model 72 is the first simplified mechanical model 272Sa. In the table generation simulation SM2b, the detailed control model 274D receives the command signal CSa necessary to drive the motor 61 with the second drive pattern DP2 from the command value input unit 75. In the table generation simulation SM2b, the detailed control model 274D receives feedback of the motor current I and motor rotation speed N. The time step size in the table generation simulation SM2b is smaller than the time step size in the pre-simulation SM2a. The time step size in the table generation simulation SM2b is fine enough to reproduce the transient response behavior during switching of the detailed element model 276D.

[0072] As shown in Figure 18B, when the table generation simulation SM2b is started, the calculation unit 40 saves the switching loss occurring in the detailed element model 276D and the voltage waveform of the voltage at a predetermined location in the second simulation model 270B when the motor current I is a specific value (step S207). In other words, performing calculations in the calculation method of the second embodiment includes calculating the voltage value at a predetermined location in the second simulation model 270B in the table generation simulation SM2b. In step S207, the calculation unit 40 saves the switching loss and voltage waveform to the storage unit 50 via the output unit 43. In step S207, the calculation unit 40 saves the value of the switching loss occurring in the detailed element model 276D when the detailed element model 276D goes from the OFF state to the ON state, i.e., when it is turned on, and the value of the switching loss occurring in the detailed element model 276D when the detailed element model 276D goes from the ON state to the OFF state, i.e., when it is turned off.

[0073] Here, the detailed element model 276D is a model in which the gate voltage Vg, drain current Id, and drain-source voltage Vds are reproduced based on the input drive signal GS, including the transient response behavior during switching, as shown in Figure 11. In step S207, the calculation unit 40 calculates the switching loss during the switching by multiplying the drain-source voltage Vds in the transient response during switching by the drain current Id in the transient response during switching.

[0074] The predetermined location where the voltage of the voltage waveform saved in step S207 is calculated is not particularly limited, as long as it is a location where electromagnetic interference noise caused by the transient response of the voltage generated by the switching operation of the detailed element model 276D can be detected.

[0075] In the table generation simulation SM2b, step S207 is executed each time the motor current I increases at a predetermined interval. For example, the predetermined interval is 10[A]. In this case, step S207 is executed each time the motor current I increases by 10[A]. The calculation unit 40 determines whether the motor current I has reached the maximum current Ia (step S208) and continues to execute step S207 until it determines that the motor current I has not reached the maximum current Ia. If the calculation unit 40 determines that the motor current I has reached the maximum current Ia (step S208: YES), it terminates the table generation simulation SM2b (step S209). The value of the motor current I used in steps S207 and S208 may be the amplitude value of the motor current I or the effective value of the motor current I.

[0076] After the table generation simulation SM2b is completed, the calculation unit 40 performs a Fast Fourier Transform on the voltage waveforms saved in step S207 (step S210). The calculation unit 40 calculates the noise level of electromagnetic interference noise for each frequency for each specific motor current I by applying a Fast Fourier Transform to each voltage waveform saved for each specific motor current I value.

[0077] After performing a Fast Fourier Transform in step S210, the calculation unit 40 generates a thermal table HT and a noise table NT (step S211). In step S211, the calculation unit 40 generates the thermal table HT based on the switching losses saved for each specific motor current I in step S207. In the second embodiment, the thermal table HT corresponds to the "first relationship" between the motor current I and the switching losses. That is, performing calculations in the calculation method of the second embodiment includes calculating the thermal table HT as the first relationship between the motor current I and the switching losses based on the switching losses in the element model 76 calculated in the table generation simulation SM2b.

[0078] Figure 20 shows an example of a thermal table HT. As shown in Figure 20, the thermal table HT stores, for each value of motor current I, the value of the switching loss Eon[J] per second that occurs in the detailed element model 276D when it is turned on, and the value of the switching loss Eoff[J] per second that occurs in the detailed element model 276D when it is turned off. For example, in Figure 20, when the motor current I is 10[A], when the detailed element model 276D is turned on, 0.52 × 10⁻¹⁰ -4It is shown that a switching loss Eon occurs in [J]. The switching loss that occurs in the detailed element model 276D when the detailed element model 276D is turned on is calculated by multiplying the switching loss Eon by the switching time. The switching loss that occurs in the detailed element model 276D when the detailed element model 276D is turned off is calculated by multiplying the switching loss Eoff by the switching time. The "interpolation method" shown in the heat table HT is an interpolation method used when calculating the switching loss for motor current I values ​​other than those shown in the heat table HT. The relationship between motor current I and switching loss is, for example, nonlinear. Therefore, when calculating the switching losses Eon and Eoff for motor current I values ​​other than those shown in the heat table HT, the calculation unit 40 calculates the switching losses Eon and Eoff by nonlinear interpolation using a quadratic function. Note that if the relationship between motor current I and switching loss is linear, the calculation unit 40 may calculate the switching loss by linear interpolation instead of nonlinear interpolation. The value of the motor current I in the heat table HT may be the amplitude value of the motor current I, or the effective value of the motor current I.

[0079] In step S211, the calculation unit 40 generates a noise table NT based on the noise level for each frequency calculated for each specific motor current I in step S210. The noise table NT corresponds to a "second relationship" between the motor current I and the noise level. In other words, performing the calculation in the calculation method of the second embodiment includes calculating the noise table NT as a second relationship between the motor current I and the noise level of electromagnetic interference noise generated in the simulation model 70, based on the voltage value calculated in the table generation simulation SM2b.

[0080] Figure 21 shows an example of a noise table NT. As shown in Figure 21, the noise table NT stores the noise level for each predetermined frequency associated with each value of motor current I. For example, Figure 21 shows that when the motor current I is 10[A], the noise level at a frequency of 1MHz is 42.24[dB]. The "interpolation method" shown in the noise table NT is the interpolation method used when calculating the noise level for motor current I values ​​other than those shown in the noise table NT. The relationship between motor current I and noise level is, for example, linear. Therefore, when calculating the noise level for motor current I values ​​other than those shown in the noise table NT, the calculation unit 40 calculates the noise level by linear interpolation. If the relationship between motor current I and noise level is nonlinear, the calculation unit 40 may calculate the noise level by nonlinear interpolation using a quadratic function or the like instead of linear interpolation. The value of motor current I in the noise table NT may be the amplitude value of motor current I or the RMS value of motor current I.

[0081] As shown in Figure 18C, after step S211, the calculation unit 40 generates a third simulation model 270C (step S212). In step S212, the calculation unit 40 generates an intermediate element model 276M. The intermediate element model 276M is a model that outputs power loss, including switching loss, corresponding to motor current I, based on a thermal table HT. In step S212, the calculation unit 40 generates a simplified control model 274S. The simplified control model 274S is a model that outputs first time series data DC1 and third time series data DC3 in chronological order. In step S212, the calculation unit 40 generates a second simplified mechanical model 272Sb. The second simplified mechanical model 272Sb is a model that outputs second time series data DC2 to the motor model 71 in chronological order. Furthermore, the calculation unit 40 may generate a simplified control model 274S at a timing prior to step S212, provided that the first time series data DC1 and the third time series data DC3 have been extracted. Also, the calculation unit 40 may generate a second simplified mechanical model 272Sb at a timing prior to step S212, provided that the second time series data DC2 has been extracted.

[0082] In step S212, the calculation unit 40 generates a third simulation model 270C by, for example, replacing the element model 76 with the intermediate element model 276M, replacing the control model 74 with the simplified control model 274S, and replacing the mechanical model 72 with the second simplified mechanical model 272Sb. The calculation unit 40 then performs the main simulation SM2c using the generated third simulation model 270C (step S213). In other words, performing calculations in the calculation method of the second embodiment includes replacing the element model 76 in the main simulation SM2c with the intermediate element model 276M, replacing the control model 74 in the main simulation SM2c with the simplified control model 274S, and replacing the mechanical model 72 in the main simulation SM2c with the second simplified mechanical model 272Sb.

[0083] The main simulation SM2c is a simulation of the control unit 64 driving the motor 61 with the first drive pattern DP1. The time step size in the main simulation SM2c is larger than the time step size in the table generation simulation SM2b. The time step size in the main simulation SM2c is a coarse time step size within a range that can reproduce the temperature change in the intermediate element model 276M. The time step size in the main simulation SM2c is, for example, about 5 times or more and 30 times or less than the time step size in the table generation simulation SM2b. The time step size in the main simulation SM2c is, for example, the same as the time step size in the pre-simulation SM2a. The time step size in the main simulation SM2c may be larger than the time step size in the pre-simulation SM2a, or it may be smaller than the time step size in the pre-simulation SM2a.

[0084] The calculation unit 40 calculates the time change of the motor current I in the main simulation SM2c. The calculation unit 40 also calculates the time change of the temperature of the element model 76 in the main simulation SM2c. The temperature of the element model 76 changes according to the integrated value of the power generated in the element model 76. The calculation unit 40 calculates the temperature change of the intermediate element model 276M based on the power loss value output from the intermediate element model 276M in the main simulation SM2c. The intermediate element model 276M may be a model that outputs a power loss that includes switching loss but does not include conduction loss. In this case, the calculation unit 40 may calculate the conduction loss from the drain current Id and the resistance value of the intermediate element model 276M in the main simulation SM2c, and then calculate the power loss generated in the intermediate element model 276M based on the said conduction loss and the switching loss output from the intermediate element model 276M.

[0085] After performing the main simulation SM2c, the calculation unit 40 saves the motor current waveform and the temperature waveform of the element model 76 (step S214). The motor current waveform is the waveform of the motor current I that changes with time in the main simulation SM2c. The temperature waveform of the element model 76 is the waveform of the temperature of the element model 76 that changes with time in the main simulation SM2c. In step S214, the calculation unit 40 saves the motor current waveform and the temperature waveform of the element model 76 to the storage unit 50.

[0086] After saving the motor current waveform and the temperature waveform of the element model 76, the calculation unit 40 outputs a noise level from a specific range of the motor current waveform (step S215). In step S215, the calculation unit 40 outputs a noise level corresponding to the value of the motor current I for each time period, based on the noise table NT, for each frequency. In other words, performing the calculation in the second embodiment includes calculating the noise level in the main simulation SM2c based on the noise table NT as a second relationship and the motor current I output in the main simulation SM2c. The calculation unit 40 saves the noise level output for each frequency (step S216). At this time, if a noise level has already been saved at a certain frequency, the calculation unit 40 compares the saved noise level with the noise level output this time. If the noise level output this time is greater than the saved noise level, the calculation unit 40 updates the noise level at that frequency to the noise level output this time. If the noise level output this time is less than or equal to the saved noise level, the calculation unit 40 does not change the saved noise level for that frequency. By performing the process in step S216 on the entire saved motor current waveform, the maximum noise level for each frequency is calculated. This calculation method is called, for example, the Maxhold method.

[0087] After saving or updating the noise level output from a specific range of the motor current waveform, the calculation unit 40 determines whether the specific range of the motor current waveform outputting the noise level has reached the final time of the motor current waveform (step S217). If it is determined that the specific range of the motor current waveform outputting the noise level has not reached the final time of the motor current waveform (step S217: NO), the calculation unit 40 updates the range of the motor current waveform outputting the noise level to the next time range (step S218) and executes steps S215 and S216 again. If it is determined that the specific range of the motor current waveform outputting the noise level has reached the final time of the motor current waveform (step S217: YES), the calculation unit 40 outputs the simulation result (step S219). In the second embodiment, the simulation result output by the calculation unit 40 includes a graph showing the temperature change of the element model 76 over time, as illustrated in Figure 12, and a graph showing the noise level for each frequency, as illustrated in Figure 13. The simulation result is displayed on the display unit 30 via the output unit 43.

[0088] According to the second embodiment, the control target of the control unit 64 is a motor 61 to which motor current I is supplied from an inverter circuit 63 having a plurality of switching elements 66. The simulation model 70 includes an inverter circuit model 73 corresponding to the inverter circuit 63 and having a plurality of element models 76, and a motor model 71 corresponding to the motor 61. Performing the calculations includes, after performing the pre-simulation SM2a and before performing the main simulation SM2c, performing a table generation simulation SM2b when the motor 61 is driven in a second drive pattern DP2 in which the motor current I changes, using a second simulation model 270B which is a detailed element model 276D capable of reproducing the electrical characteristics in the transient response when the state of the switching element 66 is switched. Performing the calculations also includes calculating a thermal table HT as a first relationship between motor current I and switching loss based on the switching loss in the element model 76 calculated in the table generation simulation SM2b. Performing the calculation involves changing the element model 76 in the main simulation SM2c to an intermediate element model 276M that outputs power loss including switching loss corresponding to motor current I based on the thermal table HT. The time the motor 61 is driven in the second drive pattern DP2 is shorter than the time the motor 61 is driven in the first drive pattern DP1.

[0089] Here, since there is a correlation between motor current I and switching loss, by calculating the thermal table HT as the first relationship in the table generation simulation SM2b, it becomes possible to calculate the switching loss based on the motor current I and the thermal table HT. By making the element model 76 in the main simulation SM2c an intermediate element model 276M that can output power loss including switching loss based on the thermal table HT, the power loss in element model 76 can be calculated in the main simulation SM2c without reproducing the transient response of the switching element 66 during switching. Therefore, the computational load on the calculation unit 40 in the main simulation SM2c when driving the motor 61 with the first drive pattern DP1 can be reduced. This reduces the time required for the main simulation SM2c. Furthermore, while it is necessary to reproduce the transient response of the switching element 66 during switching in the table generation simulation SM2b, it is sufficient to obtain the thermal table HT as the first relationship in the table generation simulation SM2b. Therefore, by making the table generation simulation SM2b a simulation of driving the motor 61 with a second drive pattern DP2 that is shorter than the first drive pattern DP1, it is possible to suppress the time required for the table generation simulation SM2b. As a result, the time required for the main simulation SM2c can be reduced by more than the time required to execute the table generation simulation SM2b. Thus, according to the second embodiment, the time required for the overall simulation of the motor system 260 can be further reduced.

[0090] According to the second embodiment, the calculation includes: calculating a voltage value at a predetermined location in the second simulation model 270B in the table generation simulation SM2b; calculating a noise table NT as a second relationship between the motor current I and the noise level of electromagnetic interference noise generated in the second simulation model 270B based on the voltage value calculated in the table generation simulation SM2b; and calculating the noise level in the main simulation SM2c based on the noise table NT as the second relationship and the motor current I output in the main simulation SM2c. Therefore, in the main simulation SM2c, the noise level of electromagnetic interference noise can be calculated without reproducing the transient response of the switching element 66 during switching.

[0091] According to the second embodiment, the calculation involves extracting second time-series data DC2 of the load that the mechanical model 72 applies to the motor model 71 in the pre-simulation SM2a, and making the mechanical model 72 in the main simulation SM2c a model that outputs the second time-series data DC2 to the motor model 71 in a time-series manner. Therefore, it is not necessary to perform calculations to drive each part of the mechanical model 72 in the main simulation SM2c. Consequently, the time required for the main simulation SM2c can be reduced compared to the case where the mechanical model 72 in the main simulation SM2c is the detailed mechanical model 72D.

[0092] According to the second embodiment, performing the calculation involves changing the mechanical model 72 in the table generation simulation SM2b to a first simplified mechanical model 272Sa that outputs a load corresponding to the motor speed N to the motor model 71. In the table generation simulation SM2b, in order to calculate the first relationship, the thermal table HT, it is sufficient to change the motor current I, for example, as in the second drive pattern DP2. Therefore, in the table generation simulation SM2b, the mechanical model 72 can be any model as long as the motor current I can be changed. Thus, by making the mechanical model 72 a simplified model that outputs a load corresponding to the motor speed N, it is possible to calculate the thermal table HT while shortening the time required for the table generation simulation SM2b.

[0093] According to the second embodiment, the time step size in the pre-simulation SM2a is larger than the time step size in the table generation simulation SM2b. Therefore, the time required for the pre-simulation SM2a can be further reduced. Consequently, the total time required for the simulation of the motor system 260 can be further reduced.

[0094] According to the second embodiment, the time step size in the main simulation SM2c is larger than the time step size in the table generation simulation SM2b. Therefore, the time required for the main simulation SM2c can be further reduced. Consequently, the total time required for the simulation of the motor system 260 can be further reduced.

[0095] According to the second embodiment, the calculation includes extracting the third time-series data DC3 of the drive capability control signal AS output from the control model 74 in the pre-simulation SM2a, and changing the control model 74 in the main simulation SM2c to a simplified control model 274S that outputs the first time-series data DC1 and the third time-series data DC3 in chronological order. Therefore, even when the control unit 64 outputs the drive capability control signal AS, the time required for the main simulation SM2c can be shortened by changing the control model 74 to the simplified control model 274S.

[0096] According to at least one embodiment described above, the calculation method of the embodiment is a computer-based calculation method. The calculation method of the embodiment includes performing calculations that include a simulation using a simulation model having an element model corresponding to a switching element and a control model corresponding to a control unit that drives the switching element to control a controlled object. Performing calculations includes: performing a first simulation of driving a controlled object in a first drive pattern using a simulation model in which the element model is a model in which the electrical characteristics of the switching element are represented by resistance characteristics; extracting first time-series data of the drive signal output from the control model in the first simulation; and performing a second simulation of driving a controlled object in a first drive pattern using a simulation model in which the control model is a model that outputs the first time-series data in a time series, and the element model is a model that can output power loss including switching loss that occurs when the state of the switching element is switched. This makes it possible to shorten the time required for simulation.

[0097] The element model used in the second simulation only needs to be capable of outputting power loss, including switching loss, that occurs when the state of the switching element is switched. The element model used in the second simulation may be a model capable of calculating power loss by reproducing the transient response of the switching element, as in the detailed element model 76D of the first embodiment, or it may be a model capable of outputting power loss based on other information such as the thermal table HT (first relationship) without reproducing the transient response of the switching element, as in the intermediate element model 276M of the second embodiment. When calculating power loss in the switching element by reproducing the transient response of the switching element in the simulation of the embodiment, the specific method for calculating said power loss is not particularly limited, as long as it can calculate said power loss. When calculating the noise level of electromagnetic interference noise caused by the switching element by reproducing the transient response of the switching element in the simulation of the embodiment, the specific method for calculating said noise level is not particularly limited, as long as it can calculate said noise level.

[0098] The simulation target in the calculation method of the embodiment may be any target having a switching element and a control unit that drives the switching element to control the target. The target is not particularly limited. The first drive pattern may be any drive pattern. The second drive pattern may be any drive pattern in which the motor current changes and in which the motor is driven for a shorter time than the first drive pattern.

[0099] At least a portion of the functions of the arithmetic unit in the arithmetic device described in the above-described embodiment is realized, for example, by a microprocessor executing a program, i.e., software, stored in a memory unit. This program is, for example, a program that causes a computer to execute the arithmetic method described in the above-described embodiment. At least a portion of the functions of the arithmetic unit in the arithmetic device may be realized by hardware including circuit units such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), and GPU (Graphics Processing Unit), or by the cooperation of software and hardware.

[0100] The calculation method, calculation device, and program of the embodiment include the following appended embodiments. (Note 1) A method of calculation performed by a computer, The process includes performing calculations that involve simulation using a simulation model having an element model corresponding to a switching element and a control model corresponding to a control unit that drives the switching element to control the controlled object. Performing the aforementioned operation means Using the simulation model in which the element model is a model in which the electrical characteristics of the switching element are represented by resistance characteristics, a first simulation is performed when the controlled object is driven by a first drive pattern. In the first simulation, the first time-series data of the drive signal output from the control model is extracted, The second simulation is performed using the simulation model in which the control model is a model that outputs the first time series data in a time series, and the element model is a model that can output power loss including switching loss that occurs when the state of the switching element is switched, when the control target is driven in a first drive pattern. A calculation method that includes this. (Note 2) The controlled object is a motor to which motor current is supplied from an inverter circuit having a plurality of switching elements. The aforementioned simulation model, An inverter circuit model having a plurality of element models, which corresponds to the inverter circuit, A motor model corresponding to the aforementioned motor, It has, Performing the aforementioned operation means After performing the first simulation and before performing the second simulation, a third simulation is performed using the simulation model, which is a model capable of reproducing the electrical characteristics in the transient response when the state of the switching element is switched, to drive the motor in a second drive pattern in which the motor current changes. Based on the switching loss in the element model calculated in the third simulation, a first relationship between the motor current and the switching loss is calculated, The element model in the second simulation is made into a model that outputs the power loss, including the switching loss corresponding to the motor current, based on the first relationship, Includes, The calculation method described in Appendix 1, wherein the time the motor is driven in the second drive pattern is shorter than the time the motor is driven in the first drive pattern. (Note 3) Performing the aforementioned operation means In the third simulation, the voltage value at a predetermined location in the simulation model is calculated, Based on the voltage value calculated in the third simulation, a second relationship is calculated between the motor current and the noise level of electromagnetic interference noise generated in the simulation model. Based on the second relationship and the motor current output in the second simulation, the noise level in the second simulation is calculated, The calculation method described in Appendix 2, including the method described in Appendix 2. (Note 4) The simulation model has a mechanical model corresponding to a driven device driven by the motor, Performing the aforementioned operation means In the first simulation, extract the second time-series data of the load that the mechanical model imparts to the motor model, The mechanical model in the second simulation is made into a model that outputs the second time-series data to the motor model in a time-series manner, The calculation method described in Appendix 2 or Appendix 3, including the above. (Note 5) The calculation method described in Appendix 4, wherein performing the calculation includes making the mechanical model in the third simulation a model that outputs a load corresponding to the rotational speed of the motor model to the motor model. (Note 6) The calculation method described in any one of the appendices 2 to 5, wherein the time step size in the first simulation is larger than the time step size in the third simulation. (Note 7) The calculation method described in any one of the appendices 2 to 6, wherein the time step size in the second simulation is larger than the time step size in the third simulation. (Note 8) The calculation method described in any one of the appendices 1 to 7, wherein the time step size in the first simulation is larger than the time step size in the second simulation. (Note 9) The control unit outputs a drive capability control signal to the switching element that changes the characteristics of the switching element. Performing the aforementioned operation means In the first simulation, the third time series data of the drive capability control signal output from the control model is extracted, The control model in the second simulation is made into a model that outputs the first time series data and the third time series data in a time series order, The calculation method described in any one of the appendices 1 through 8, including the one specified above. (Note 10) The system includes a calculation unit that performs calculations including simulations using a simulation model having an element model corresponding to a switching element and a control model corresponding to a control unit that drives the switching element to control the controlled object. The aforementioned arithmetic unit, Using the simulation model in which the element model is a model in which the electrical characteristics of the switching element are represented by resistance characteristics, a first simulation is performed when the controlled object is driven by a first drive pattern. In the first simulation, the first time-series data of the drive signal output from the control model is extracted. A computing device that performs a second simulation of driving the controlled object in a first drive pattern using the simulation model, wherein the control model is a model that outputs the first time series data in a time series, and the element model is a model that can output power loss including switching loss that occurs when the state of the switching element is switched. (Note 11) A program that causes a computer to execute one of the calculation methods described in one of the appendices 1 through 9.

[0101] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0102] 40…Calculation unit, 61…Motor (controlled object), 62…Driven device, 63…Inverter circuit, 64, 264…Control unit, 66…Switching element, 70…Simulation model, 71…Motor model, 72…Mechanical model, 73…Inverter circuit model, 74…Control model, 76…Element model, 100…Calculation unit, AS…Drive capability control signal, DC1…First time series data, DC2…Second time series data, DC3…Third time series data, DP1…First drive pattern, DP2…Second drive pattern, GS…Drive signal, HT…Heat table (first relationship), I…Motor current, NT…Noise table (second relationship), SM1a, SM2a…Pre-simulation (first simulation), SM1b, SM2c…Main simulation (second simulation), SM2b…Table generation simulation (third simulation)

Claims

1. A method of calculation performed by a computer, The process includes performing calculations that involve simulation using a simulation model having an element model corresponding to a switching element and a control model corresponding to a control unit that drives the switching element to control the controlled object. Performing the aforementioned operation means Using the simulation model in which the element model is a model in which the electrical characteristics of the switching element are represented by resistance characteristics, a first simulation is performed when the controlled object is driven by a first drive pattern. In the first simulation, the first time-series data of the drive signal output from the control model is extracted, The second simulation is performed using the simulation model in which the control model is a model that outputs the first time-series data in a time-series manner, and the element model is a model that can output power loss including switching loss that occurs when the state of the switching element is switched, when the control target is driven in a first drive pattern. A calculation method that includes this.

2. The controlled object is a motor to which motor current is supplied from an inverter circuit having a plurality of switching elements. The aforementioned simulation model, An inverter circuit model having a plurality of element models, which corresponds to the inverter circuit, A motor model corresponding to the aforementioned motor, It has, Performing the aforementioned operation means After performing the first simulation and before performing the second simulation, a third simulation is performed using the simulation model, which is a model capable of reproducing the electrical characteristics in the transient response when the state of the switching element is switched, to drive the motor in a second drive pattern in which the motor current changes. Based on the switching loss in the element model calculated in the third simulation, a first relationship between the motor current and the switching loss is calculated, The element model in the second simulation is made into a model that outputs the power loss, including the switching loss corresponding to the motor current, based on the first relationship, Includes, The calculation method according to claim 1, wherein the time during which the motor is driven in the second drive pattern is shorter than the time during which the motor is driven in the first drive pattern.

3. Performing the aforementioned operation means In the third simulation, the voltage value at a predetermined location in the simulation model is calculated, Based on the voltage value calculated in the third simulation, a second relationship is calculated between the motor current and the noise level of electromagnetic interference noise generated in the simulation model. Based on the second relationship and the motor current output in the second simulation, the noise level in the second simulation is calculated, The calculation method according to claim 2, including the method described in claim 2.

4. The simulation model has a mechanical model corresponding to a driven device driven by the motor, Performing the aforementioned operation means In the first simulation, the second time-series data of the load that the mechanical model imparts to the motor model is extracted, The mechanical model in the second simulation is made into a model that outputs the second time-series data to the motor model in a time-series manner, The calculation method according to claim 2, including the method described in claim 2.

5. The calculation method according to claim 4, wherein performing the calculation includes making the mechanical model in the third simulation a model that outputs a load corresponding to the rotational speed of the motor model to the motor model.

6. The calculation method according to claim 2, wherein the time step size in the first simulation is larger than the time step size in the third simulation.

7. The calculation method according to claim 2, wherein the time step size in the second simulation is larger than the time step size in the third simulation.

8. The calculation method according to claim 1, wherein the time step size in the first simulation is larger than the time step size in the second simulation.

9. The control unit outputs a drive capability control signal to the switching element that changes the characteristics of the switching element. Performing the aforementioned operation means In the first simulation, the third time-series data of the drive capability control signal output from the control model is extracted, The control model in the second simulation is made into a model that outputs the first time series data and the third time series data in a time series order, The calculation method according to claim 1, including the method described in claim 1.

10. The system includes a calculation unit that performs calculations including simulations using a simulation model having an element model corresponding to a switching element and a control model corresponding to a control unit that drives the switching element to control the controlled object. The aforementioned arithmetic unit, Using the simulation model in which the element model is a model in which the electrical characteristics of the switching element are represented by resistance characteristics, a first simulation is performed when the controlled object is driven by a first drive pattern. In the first simulation, the first time-series data of the drive signal output from the control model is extracted. A computing device that performs a second simulation of driving the controlled object in a first drive pattern, using the simulation model in which the control model is a model that outputs the first time series data in a time series, and the element model is a model that can output power loss including switching loss that occurs when the state of the switching element is switched.

11. A program that causes a computer to execute the calculation method described in any one of claims 1 to 9.

Images