Control device

Abstract

An AD converter (38) converts an analog signal into digital data at a sampling frequency compliant with a request for synchronous PWM processing of a motor. The digital data output by the AD converter (38) is input to a DFT circuit (36). The DFT circuit (36) is provided with a thinning-out circuit (54). The thinning-out circuit (54) inputs, to an FFT (56), data obtained by thinning out time-series data sampled at the sampling frequency. The FFT (56) calculates data related to a Fourier coefficient by using the input data.

Description

Control device

[0007]

[0001] The present disclosure relates to a control device.

[0002] Patent Document 1 describes a control device that executes a process of correcting a target value of a motor rotation speed according to a frequency fluctuation component obtained by Fourier-transforming the motor rotation speed. This process aims to suppress fluctuations in the output torque of the motor.

[0003] On the other hand, synchronous PWM processing is well-known as control of a control amount of a motor.

[0004] Japanese Patent Application Laid-Open No. 2016-127649

[0005] When executing synchronous PWM processing, it is necessary to sample input data at a sampling frequency that is an integer multiple of the electrical angular frequency. On the other hand, when adjusting the input data used in Fourier transform to the sampling frequency of synchronous PWM processing, its resolution is limited by the sampling frequency and may not achieve the desired resolution.

[0006] A control device according to a first aspect for solving the above problems is a control device that controls a control amount of a control target, including a control circuit, an AD converter that converts an analog signal into digital data, a decimation circuit, and a Fourier transform circuit; the control circuit is configured to execute a process of controlling the control amount based on first digital data that is the digital data obtained by converting a predetermined analog signal by the AD converter; the Fourier transform circuit is configured to output coefficient data, which is data indicating Fourier coefficients, to the control circuit based on time-series data of conversion data; the conversion data is second digital data that is the digital data converted by the AD converter or data calculated from the second digital data, the second digital data is data synchronized with the first digital data; and the decimation circuit is a circuit that selects the conversion data used for calculating the coefficient data by decimating the time-series data.

[0007] In the above configuration, the decimation circuit decimates the conversion data, thereby changing the sampling frequency of the conversion data used to calculate the coefficient data relative to the sampling frequency of the AD converter. This prevents the calculation accuracy of the coefficient data from being limited by the sampling frequency of the AD converter.

[0008] The control device in the second aspect is the control device described in the first aspect, wherein the sampling frequency of the conversion data is equal to the sampling frequency of the first digital data input to the control circuit.

[0009] In the above configuration, conversion data sampled at the same frequency as the sampling frequency of the digital data input to the control circuit is input to the decimation circuit. By decimating this conversion data, coefficient data can be calculated from the time-series data of the conversion data sampled at a sampling frequency different from the sampling frequency of the digital data input to the control circuit.

[0010] The control device described in the third aspect is the control device described in the second aspect, wherein the controlled object is a rotating electric machine, the output voltage of an inverter is applied to the terminals of the rotating electric machine, the AD converter is configured to convert the predetermined analog signal into first digital data at a frequency that is an integer multiple of the electrical angular frequency of the rotating electric machine, the control circuit is configured to perform synchronous PWM processing, and the synchronous PWM processing is a process that sets the switching pattern of the inverter based on the first digital data as an input variable each time the predetermined analog signal is converted into first digital data at a frequency that is an integer multiple of the frequency.

[0011] In the above configuration, even though the conversion data is sampled at a sampling frequency equal to the sampling frequency defined by the synchronous PWM processing, the sampling frequency of the conversion data used to calculate the coefficient data can be changed by downsampling the conversion data.

[0012] The control device according to the fourth aspect is the control device according to any one of the first to third aspects, wherein the decimation circuit includes a first decimation circuit and a second decimation circuit, the Fourier transform circuit includes a first Fourier transform circuit and a second Fourier transform circuit, the intervals at which the first decimation circuit and the second decimation circuit decimate the conversion data are different from each other, the first Fourier transform circuit is configured to calculate the coefficient data using the conversion data decimated by the first decimation circuit, and the second Fourier transform circuit is configured to calculate the coefficient data using the conversion data decimated by the second decimation circuit.

[0013] In the above configuration, since it includes a first decimation circuit and a second decimation circuit, the first Fourier transform circuit and the second Fourier transform circuit can calculate coefficient data based on conversion data sampled at different sampling frequencies. Therefore, even if the frequencies for which coefficient data is to be obtained are different, the coefficient data can be calculated with high accuracy.

[0014] The control device in the fifth aspect is the control device described in any one of the first to fourth aspects, wherein the Fourier transform circuit is configured to generate the coefficient data by fast Fourier transform.

[0015] In the above configuration, by employing a fast Fourier transform algorithm, the computational load on the Fourier transform circuit caused by the calculation of coefficient data can be reduced. The control device in the sixth aspect is the control device described in any one of the first to fifth aspects, wherein the control circuit is configured to input frequency identification data, which is data for identifying the frequency for which Fourier coefficients are to be obtained, to the Fourier transform circuit, and the decimation circuit is configured to select the conversion data to be used for calculating the coefficient data by decimating the conversion data according to the frequency identification data.

[0016] In the above configuration, the Fourier transform circuit decimates the conversion data according to the frequency-specific data, thereby changing the ratio between the frequency for which the Fourier coefficients are to be determined and the sampling frequency. The control device described in the seventh aspect is a control device described in any one of the above aspects 3 to 6 (excluding those not included in the third aspect), wherein the rotating electric machine is a motor that drives a compressor, the output voltage of an inverter is applied to the terminals of the motor, the Fourier transform circuit is configured to calculate the coefficient data corresponding to a rational multiple of the mechanical angular frequency of the motor using the conversion data decimated by the decimation circuit, the control circuit is configured to perform an output voltage adjustment process, and the output voltage adjustment process is configured to operate the output voltage of the inverter based on the coefficient data as an input variable.

[0017] The torque applied by the compressor to the motor fluctuates according to the compressor's rotation angle. Therefore, the load torque applied by the compressor to the motor is a rational number multiple of the motor's mechanical angle. In evaluating the effect of this load torque, the amplitude of the fluctuation component with a frequency that is an integer multiple of the fluctuation period of the load torque applied by the compressor to the motor is useful information. However, if conversion data sampled at a sampling frequency determined by the requirements of synchronous PWM processing is used, there is a risk that the coefficient data corresponding to the frequency of that fluctuation component cannot be calculated with high accuracy. Therefore, in the above configuration, by downsampling the conversion data, the coefficient data related to the Fourier coefficient of this fluctuation component can be calculated with the desired resolution. Then, by manipulating the inverter output voltage based on this coefficient data, torque fluctuations can be suppressed.

[0018] The control device according to the eighth aspect is a control device according to any one of the above aspects 3 to 7 (excluding those not relating to the third aspect), wherein the output voltage of the inverter is applied to the terminals of the rotating electric machine, the Fourier transform circuit is configured to calculate coefficient data corresponding to a frequency 3n times the electrical angular frequency of the rotating electric machine (where n is a natural number of 1 or more) using the conversion data thinned by the thinning circuit, the control circuit is configured to perform an output voltage adjustment process, and the output voltage adjustment process is configured to operate the output voltage of the inverter based on the coefficient data as an input variable.

[0019] Spatial harmonics in rotating electric machines tend to exhibit a prominent frequency component at 3n times the electrical angular frequency. However, using conversion data sampled at a sampling frequency determined by the requirements of synchronous PWM processing may result in inaccurate calculation of coefficient data corresponding to 3n times the electrical angular frequency. Therefore, in the above configuration, the coefficient data can be calculated with the desired resolution by downsampling the conversion data. By manipulating the inverter output voltage based on the coefficient data of the frequency component at 3n times the electrical angular frequency, the reduction in controllability of the controllable variable of the rotating electric machine caused by spatial harmonics can be suppressed.

[0020] The control device of the ninth aspect is a control device described in any one of the third to eighth aspects (excluding those not included in the third aspect), wherein the control circuit is configured to perform a diagnostic process, the Fourier transform circuit is configured to calculate coefficient data corresponding to a rational multiple of the mechanical angular frequency of the rotating electric machine using the conversion data thinned by the thinning circuit, and the diagnostic process is a process that diagnoses whether or not there is an abnormality in the controlled object based on the coefficient data as an input variable.

[0021] The characteristic frequencies of physical quantities resulting from the operation of a rotating electric machine tend to be rational multiples of the rotational speed. Therefore, the values ​​of these characteristic frequency components tend to differ depending on whether or not there is a malfunction in the rotating electric machine or the equipment driven by it. On the other hand, if conversion data sampled at a sampling frequency determined by the requirements of synchronous PWM processing is used, there is a risk that the coefficient data corresponding to the above characteristic frequencies cannot be calculated with high accuracy. In this configuration, the above coefficient data can be calculated with the desired resolution by downsampling the conversion data. This enables high-precision diagnosis of the presence or absence of malfunctions.

[0022] This is a block diagram showing the configuration of an air conditioning system according to the first embodiment. This is a block diagram showing the processing performed by the CPU of the control device according to the same embodiment. This is a block diagram showing the configuration of a DFT circuit of the control device according to the same embodiment. This is a flowchart showing the procedure of processing performed by the CPU of the control device according to the same embodiment. This is a flowchart showing the procedure of processing performed by the DFT circuit of the same embodiment. This is a block diagram showing the processing performed by the CPU of the control device according to the second embodiment. This is a block diagram showing the configuration of a DFT circuit of the control device according to the third embodiment. This is a flowchart showing the procedure of processing performed by the CPU of the fourth embodiment. This is a flowchart showing the procedure of processing performed by the CPU of the same embodiment.

[0023] <First Embodiment> The first embodiment will be described below with reference to the drawings. "Prerequisite Configuration" Figure 1 shows the configuration of the air conditioning system according to this embodiment.

[0024] The air conditioning system 10 receives power from, for example, a grid power supply 20. The air conditioning system 10 includes a compressor 12. The rotating shaft 12a of the compressor 12 is mechanically connected to the rotating shaft 14a of a motor 14. The motor 14 is, for example, a three-phase synchronous motor. The motor 14 may also be, for example, an embedded magnet synchronous motor. The output voltage of the inverter 16 is applied to each terminal of the motor 14. The inverter 16 is a circuit that converts the voltage of a DC voltage source into an AC voltage and applies it to the motor 14.

[0025] The inverter 16 has three series connections of switching elements S#p on the upper arm and S#n on the lower arm, where "# = u, v, w". Freewheeling diodes D#p and D#n are connected in antiparallel to each of these switching elements S#p and S#n.

[0026] Power from the grid power supply 20 is supplied to the input terminals of the inverter 16 via the AC / DC conversion circuit 18. A smoothing capacitor 17 is provided between the AC / DC conversion circuit 18 and the inverter 16.

[0027] The control device 30 includes a CPU 32, memory 34, DFT circuit 36, and AD converter 38. The CPU 32 controls the control amount of the motor 14, which is the object controlled by the control device 30, by executing a program stored in the memory 34. The DFT circuit 36 ​​and AD converter 38 are hardware processing circuits.

[0028] The CPU 32 refers to the mechanical angle θm of the motor 14 detected by the rotation angle sensor 40 in order to control the control variable. The CPU 32 also refers to the vibration detection signal O of the compressor 12 detected by the vibration sensor 42. The CPU 32 also refers to the current I flowing through the motor 14 detected by the current sensor 44. The current sensor 44 is configured, for example, with a shunt resistor provided on the DC bus on the negative side of the inverter 16 and a voltage sensor that detects the voltage drop across the shunt resistor. In other words, the current I in this embodiment is the current flowing through the DC bus on the negative side. The CPU 32 also refers to the input voltage Vin of the inverter 16 detected by the voltage sensor 46.

[0029] "Processing by CPU 32" Figure 2 shows a part of the processing performed by the CPU 32. The processing shown in Figure 2 is achieved by the CPU 32 repeatedly executing a program stored in memory 34, for example, at a predetermined cycle.

[0030] The target angular velocity setting process M10 is the process of setting the target angular velocity ω*0, which is the target value of the rate of change of the machine angle θm. The correction process M12 is the process of substituting the value obtained by correcting the target angular velocity ω*0 by the correction amount Δωc, which will be described later, into the target angular velocity ω*. The angular velocity calculation process M14 is the process of calculating the angular velocity ωm based on the machine angle θm, which has been converted into digital data by the AD converter 38, as an input variable. The deviation calculation process M16 is the process of calculating the deviation Δω, which is the value obtained by subtracting the angular velocity ωm from the target angular velocity ω*. The current command value setting process M18 is the process of calculating the current command value id* for the d axis and the current command value iq* for the q axis based on the deviation Δω as an input variable.

[0031] The electrical angle calculation process M19 is a process that assigns the remainder obtained by dividing the value obtained by multiplying the mechanical angle θm, which has been converted into digital data by the AD converter 38, by the number of pole pairs p, by 360, to the electrical angle θe. The two-phase conversion process M20 is a process that calculates the d-axis current id and the q-axis current iq based on the input variables: the current I, which has been converted into digital data by the AD converter 38, the switching pattern, and the electrical angle θe. The switching pattern is determined by the on and off states of the switching elements S#p and S#n of the inverter 16. The switching pattern determines the voltage vector of the output voltage of the inverter 16. The deviation calculation process M22 is a process that calculates the q-axis current deviation, which is the value obtained by subtracting the q-axis current iq from the q-axis current command value iq*. The deviation calculation process M24 is a process that calculates the d-axis current deviation, which is the value obtained by subtracting the d-axis current id from the d-axis current command value id*.

[0032] The voltage command value setting process M26 is a process that sets the output voltage command value of the inverter 16 based on the deviation output of the deviation calculation processes M22 and M24, which are input variables, and the q-axis current command value iq* and the d-axis current command value id*. As an example, the voltage command value setting process M26 includes a process to calculate the q-axis voltage command value and the d-axis voltage command value based on the sum of the output values ​​of the proportional element and the differential element, each of which is an input variable of the pair of deviations. Furthermore, the voltage command value setting process M26 includes a process to correct the above voltage command value by non-interference control based on the q-axis current command value iq* and the d-axis current command value id*, which are input variables. The voltage command value setting process M26 may also include a process to correct the above voltage command value for induced voltage compensation based on the rate of change of the electrical angle θe, which is an input variable.

[0033] The voltage command value setting process M26 outputs amplitude Va and phase δ as variables indicating the output voltage of the inverter 16. The operation signal generation process M28 calculates operation signals g#p and g#n for the switching elements S#p and S#n based on the amplitude Va and phase δ as input variables. In this embodiment, as an example, the operation signals g#p and g#n are calculated by triangular wave comparison PWM processing. In particular, in this embodiment, the operation signals g#p and g#n are calculated by so-called synchronous PWM processing, which sets the carrier frequency to an integer multiple of the electrical angular frequency of the motor 14. In other words, the switching pattern of the inverter 16 is set by synchronous PWM processing.

[0034] Figure 2 illustrates a case where half a period of the U-phase voltage command value vu*, determined by amplitude Va and phase δ, corresponds to two periods of a triangular waveform carrier. The PWM signal gu in Figure 2 is determined by comparing the magnitudes of the voltage command value vu* and the carrier. Dead time compensation is applied to the PWM signal gu to generate the final operation signals gup and gun.

[0035] The vibration suppression process M30 is a process that calculates a correction amount Δωc to suppress the vibration of the compressor 12. This vibration is synchronized with the change in the rotation angle of the rotating shaft 12a of the compressor 12. The input variable for the vibration suppression process M30 is the Fourier amplitude Ift. The Fourier amplitude Ift is calculated by the DFT circuit 36.

[0036] "About the DFT Circuit 36" Figure 3 shows the configuration of the DFT circuit 36. The electrical angle calculation unit 50 is a circuit that calculates the electrical angle θe by multiplying the mechanical angle θm, which has been converted into digital data by the AD converter 38, by the number of pole pairs p and then dividing the result by 360. The q-axis current calculation unit 52 is a process that calculates the q-axis current iq based on the current I, which has been converted into digital data by the AD converter 38 as an input variable. The q-axis current calculation unit 52 refers to the switching pattern of the inverter 16 and the electrical angle θe in order to calculate the q-axis current iq.

[0037] The decimation circuit 54 is a circuit that selects the q-axis current iq to be used in the FFT 56 by decimating the time-series data of the q-axis current iq calculated by the q-axis current calculation unit 52. The FFT 56 is a circuit that calculates the Fourier amplitude Ift by performing a fast Fourier transform of the q-axis current selected by the decimation circuit 54. As an example, the FFT 56 calculates the Fourier amplitude Ift using the Cooley-Tukey type FFT algorithm.

[0038] Register 58 stores the target frequency ft, which is the frequency at which the Fourier amplitude Ift is to be calculated, and the required resolution Δf for the Fourier amplitude Ift. The sampling frequency setting unit 60 is a circuit that sets the sampling frequency of the AD converter 38.

[0039] "Setting Register 58" Figure 4 shows the procedure for setting register 58. The series of processes shown in Figure 4 are realized by the CPU 32 repeatedly executing the program stored in memory 34, for example, at a predetermined cycle. In the following, the step number of each process is represented by a number preceded by "S".

[0040] In the series of processes shown in FIG. 4, the CPU 32 first acquires the angular velocity ωm (S10). Then, the CPU 32 substitutes the value obtained by multiplying the angular velocity ωm by the coefficient Kt into the target frequency ft (S12). The target frequency ft is the frequency for which the Fourier amplitude Ift is to be obtained. The coefficient Kt is a coefficient for converting the angular velocity ωm into the frequency of the load torque caused by the compressor 12. The coefficient Kt is, for example, an integer of 1 or more.

[0041] Next, the CPU 32 sets the resolution Δf (S14). Then, the CPU 32 outputs the target frequency ft and the resolution Δf to the DFT circuit 36 (S16). When the CPU 32 completes the process of S16, the series of processes shown in FIG. 4 is temporarily terminated.

[0042] "Operation of the DFT Circuit 36" FIG. 5 shows the operation of the DFT circuit 36 according to the setting of the register 58. The sampling frequency setting unit 60 first substitutes the value obtained by multiplying the electrical angular frequency fe by the value of 2 to the power of "n" into the PWM frequency fpwm (S20). "n" is an integer of 1 or more. Then, the sampling frequency setting unit 60 outputs the PWM frequency fpwm to the AD converter 38 (S22).

[0043] On the other hand, the decimation circuit 54 searches for the value of the decimation interval M that satisfies the following conditions A to D (S24). Condition A: This is a condition that the number of operations N for calculating the Fourier amplitude Ift is 2 to the power of "t". "t" is an integer of 1 or more. This is a condition in view of the fact that in the FFT algorithm, generally, the number of operations is a power of 2.

[0044] Condition B: This is a condition that the value obtained by dividing the sampling frequency fs by the number of operations N is equal to the resolution Δf. This condition is for satisfying the set resolution Δf. Condition C: This is a condition that the value obtained by dividing the PWM frequency fpwm by the value of the decimation interval M is equal to the sampling frequency fs.

[0045] Condition D: A condition that the specified variable k for determining the target frequency ft is equal to the value obtained by dividing the target frequency ft by the resolution Δf. Here, the specified variable k is the variable that appears in the independent variable "2·π·j·k·m / (2^t)" of the exponential function in the discrete Fourier transform. Here, "2^t" indicates the t-th power of 2. Also, the variable m is a variable for adding the values of the exponential function from 0 to 2^t - 1. Also, the imaginary unit is denoted as "j".

[0046] The decimation circuit 54 sets the decimation interval M obtained by the process of S24 to the actual decimation interval (S26). Also, the decimation circuit 54 outputs the value of the specified variable k obtained by the process of S24 to the FFT 56 (S28).

[0047] When the process of S28 is completed, the process of FIG. 5 that is periodically executed is temporarily terminated. "Operations and Effects of the Present Embodiment" The CPU 32 controls the angular velocity of the motor 14 by synchronous PWM processing. Therefore, the CPU 32 samples input variables such as the current I, which are synchronous PWM processing input variables, at the PWM frequency fpwm that is an integer multiple of the electrical angular frequency of the motor 14.

[0048] On the other hand, the DFT circuit 36 shares the ADC 38 with the CPU 32. Therefore, the output of the ADC 38 input to the DFT circuit 36 is updated at the period of the reciprocal of the PWM frequency fpwm.

[0049] When the FFT 56 calculates the Fourier amplitude Ift using digital data obtained by sampling with the PWM frequency fpwm as the sampling frequency, there is a possibility that it may be difficult to set its resolution to a desired resolution.

[0050] Therefore, data decimated by the decimation circuit 54 is input to the FFT 56. Thereby, the sampling frequency of the digital data input to the FFT 56 can be changed with respect to the PWM frequency fpwm. Therefore, the FFT 56 can calculate the Fourier amplitude Ift with a desired resolution.

[0051] For example, if the angular velocity ωm is "35 Hz", the number of pole pairs p is "3", and the variable n in S20 is "8", then the PWM frequency fpwm is set to "105 × 256 = 26880 Hz". The CPU 32 then updates the switching pattern based on the sampling values ​​of the current I 256 times per electrical angular period.

[0052] On the other hand, in this case, for example, if both the target frequency ft and the resolution Δf are "35", the decimation interval M by the decimation circuit 54 is set to "1". This allows the FFT 56 to use all of the current I input to the DFT circuit 36 ​​to calculate the Fourier amplitude Ift with the desired resolution. In other words, without decimation by the decimation circuit 54, the FFT 56 can use all of the current I input to the DFT circuit 36 ​​to calculate the Fourier amplitude Ift with the desired resolution. However, the number of calculations N in this case is 256.

[0053] However, for example, if the angular velocity ωm and target frequency ft are "30 Hz", the number of pole pairs p is "3", the variable n in S20 is "8", and the resolution Δf is "10", then without decimation, the number of calculations required to satisfy the resolution Δf requirement would be "9.256". This does not satisfy the requirement of FFT56 that the number of calculations N be a power of 2.

[0054] As described above, the following effects and advantages can be obtained with respect to this embodiment. (1-1) The sampling frequency of the current I input to the DFT circuit 36 ​​is equal to the sampling frequency of the current I used by the CPU 32 for controlling the motor 14. Therefore, the sampling frequency of the current input to the DFT circuit 36 ​​is completely determined by the requirements of the synchronous PWM processing. For this reason, the usefulness of the decimation circuit 54 is particularly great.

[0055] (1-2) The DFT circuit 36 ​​is equipped with an FFT 56 that calculates the Fourier amplitude Ift using a fast Fourier transform algorithm. Therefore, the Fourier amplitude Ift can be calculated efficiently.

[0056] (1-3) The CPU 32 inputs the target frequency ft and resolution Δf into the register 58, and the decimation circuit 54 sets the decimation interval M. This allows the CPU 32 to calculate the Fourier amplitude Ift of the target frequency ft so as to satisfy the resolution Δf.

[0057] (1-4) The torque applied by the compressor 12 to the motor 14 fluctuates according to the rotation angle of the compressor 12. Therefore, the load torque applied by the compressor 12 to the motor 14 is a rational number multiple of the mechanical angle θm of the motor 14. In evaluating the effect of this load torque, the amplitude of the fluctuation component at a frequency that is an integer multiple of the fluctuation period of the load torque applied by the compressor 12 to the motor 14 is useful information. Therefore, the CPU 32 set the target frequency ft to a rational number multiple of the electrical angular frequency. Then, the target angular velocity ω*0 was corrected according to the Fourier amplitude Ift corresponding to the target frequency ft. This makes it possible to suppress torque fluctuations caused by fluctuations in the load torque of the compressor 12.

[0058] <Second Embodiment> The second embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings.

[0059] Figure 6 shows the processing performed by the CPU 32. In Figure 6, for convenience, the same reference numerals are used for the processing corresponding to the processing shown in Figure 2. As shown in Figure 6, the deviation calculation processing M16 in this embodiment inputs the deviation between the target angular velocity ω* set by the target angular velocity setting processing M10 and the angular velocity ωm to the current command value setting processing M18.

[0060] Phase correction process M30a calculates a correction amount Δδ to correct the phase δ of the output voltage 16 in order to suppress torque ripple caused by spatial harmonics. Correction process M12a is a process that inputs the value obtained by correcting the phase δ set by voltage command value setting process M26 with the correction amount Δδ to the operation signal generation process M28.

[0061] Phase correction process M30a is a process that calculates a correction amount Δδ based on the Fourier amplitude Vft as an input variable. The target frequency ft corresponding to the Fourier amplitude Vft is a multiple of 3 of the angular velocity ωm. More specifically, the target frequency ft is a multiple of 3 of the electrical angular frequency of the motor 14. This setting is based on the fact that the spatial harmonics of the motor 14 tend to have a prominent frequency component at 3n times the electrical angular frequency.

[0062] In this embodiment, the input voltage Vin is converted into digital data by the AD converter 38 and input to the DFT circuit 36. The AD converter 38 also sequentially converts analog signals other than the current I into digital data at the sampling period of the current I.

[0063] Here, for example, let's consider the case where the angular velocity ωm is "23 Hz", the number of pole pairs p is "4", the target frequency ft is "23 Hz", and the resolution is "1 Hz". In that case, the electrical angular frequency is "92 Hz". The sampling frequency of the AD converter 38 is set to an integer multiple of "92 Hz", for example, "92 × 128 Hz". Then, the decimation circuit 54 is set to a decimation interval M of "92". As a result, a resolution of "1 Hz" can be achieved with a calculation count N of "128".

[0064] <Third Embodiment> The third embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings.

[0065] Figure 7 shows the configuration of the DFT circuit 36 ​​according to this embodiment. In Figure 7, for convenience, the same reference numerals are used for circuits corresponding to the circuit shown in Figure 3. As shown in Figure 7, this embodiment includes two decimation circuits 54(1) and 54(2) and two FFTs 56(1) and 56(2). In this embodiment, the DFT circuit 36 ​​receives a detection signal O that has been converted into digital data by the AD converter 38. The AD converter 38 also converts the detection signal O into digital data at the sampling period of the current I.

[0066] Figure 8 shows the procedure for setting register 58. The series of processes shown in Figure 8 are realized by the CPU 32 repeatedly executing a program stored in memory 34, for example, at a predetermined cycle. In Figure 8, for convenience, the processes corresponding to the processes shown in Figure 4 are assigned the same step numbers.

[0067] In the series of processes shown in Figure 8, when the CPU 32 completes the process in S10, it substitutes the value obtained by multiplying the angular velocity ωm by the coefficient Kt(1) into the target frequency ft(1), and also substitutes the value obtained by multiplying the angular velocity ωm by the coefficient Kt(2) into the target frequency ft(2) (S12a). The coefficients Kt(1) and Kt(2) are coefficients that convert the angular velocity ωm to a frequency that becomes significant due to an abnormality in the compressor 12. The coefficients Kt(1) and Kt(2) are rational numbers.

[0068] The CPU 32 sets the resolution Δf(1) for the target frequency ft(1) and the resolution Δf(2) for the target frequency ft(2) (S14a). Then, the CPU 32 outputs the target frequencies ft(1) and ft(2) and the resolutions Δf(1) and Δf(2) to the DFT circuit 36 ​​(S16a).

[0069] When the CPU 32 completes the process in S16a, it terminates the series of processes shown in Figure 8. Figure 9 shows the procedure for diagnosing whether or not there is an abnormality in the compressor 12 based on the detection signal O. The process shown in Figure 9 is realized by the CPU 32 repeatedly executing a program stored in memory 34, for example, at a predetermined cycle.

[0070] In the series of processes shown in Figure 9, the CPU 32 first obtains the Fourier amplitude Off(1) related to the target frequency ft(1) calculated by the FFT 56 (S30). Then the CPU 32 determines whether the Fourier amplitude Off(1) is greater than or equal to the threshold Off1th (S32). This process determines whether or not a first abnormality has occurred in the compressor 12.

[0071] If the CPU 32 determines that the Fourier amplitude Off(1) is greater than or equal to the threshold Off1th (S32: YES), it determines that there is a first abnormality in the compressor 12 (S34). When the CPU 32 completes the process in S34, or when it makes a negative determination in the process in S32, it obtains the Fourier amplitude Off(2) related to the target frequency ft(2) calculated by the FFT 56 (S36). Then, the CPU 32 determines whether the Fourier amplitude Off(2) is greater than or equal to the threshold Off2th (S38). This process determines whether there is a second abnormality in the compressor 12.

[0072] If the CPU 32 determines that the Fourier amplitude Off(2) is greater than or equal to the threshold Off2th (S38: YES), it determines that there is a second abnormality in the compressor 12 (S40). Note that when the CPU 32 completes the process in S40, or when it makes a negative determination in the process in S38, it temporarily terminates the series of processes shown in Figure 9.

[0073] For example, let's consider the case where the angular velocity ωm is "60 Hz", the number of pole pairs p is "3", the target frequencies ft(1) and ft(2) are "60 Hz" and "90 Hz" respectively, the resolutions Δf(1) and Δf(2) are "2 Hz" and "3 Hz" respectively, and the variable n in S20 is "7". In this case, the PWM frequency fpwm is 180 × 128 = 23040 Hz. The decimation circuit 54(1) is set to a decimation interval M of 90. This allows us to calculate the Fourier amplitude Off(1) with a resolution Δf(1) of 2 Hz and a target frequency ft(1) of 20 Hz. The decimation circuit 54(2) is set to a decimation interval M of 60. This allows us to calculate the Fourier amplitude Off(3) with a resolution Δf(2) of 3 Hz and a target frequency ft(2) of 30 Hz.

[0074] According to this embodiment described above, in addition to the effects similar to those of (1-1) to (1-3) of the first embodiment, the following further actions and effects can be obtained. (3-1) The characteristic frequencies of the physical quantities caused by the operation of the motor 14 tend to be frequencies that are rational multiples of the electrical angular frequency. Therefore, the values ​​of these characteristic frequency components tend to differ depending on whether or not there is a malfunction in the motor 14 or the compressor 12 driven by the motor 14. Therefore, the CPU 32 sets the target frequencies ft(1) and ft(2) to these frequencies. As a result, the CPU 32 can diagnose whether or not there is a malfunction based on the Fourier amplitudes Off(1) and Off(2) as input variables.

[0075] (3-2) Multiple decimation circuits 54 and FFTs 56 are provided. This makes it possible to calculate the Fourier amplitudes Offt(1) and Offt(2) for different target frequencies ft(1) and ft(2) simultaneously.

[0076] <Correspondence> The correspondence between the matters in the above embodiment and the matters described in the "Means for Solving the Problems" section is as follows. Below, the correspondence is shown for each number of the viewpoint described in the "Means for Solving the Problems" section. [1, 2, 5] The control circuit corresponds to the CPU 32. The AD converter corresponds to the AD converter 38. The decimation circuit corresponds to the decimation circuits 54, 54(1), and 54(2). The Fourier transform circuit corresponds to the FFTs 56, 56(1), and 56(2). The first digital data, the second digital data, and the conversion data correspond to the current I, current I, and q-axis current iq in the first embodiment, respectively. The first digital data, the second digital data, and the conversion data correspond to the current I, input voltage Vin, and input voltage Vin in the second embodiment, respectively. The first digital data, the second digital data, and the conversion data correspond to the current I, detection signal O, and detection signal O in the third embodiment, respectively. [3] The rotating electric machine corresponds to the motor 14. [4] The first decimation circuit and the second decimation circuit correspond to the decimation circuits 54(1) and 54(2). The first Fourier transform circuit and the second Fourier transform circuit correspond to the FFTs 56(1) and 56(2). [6] The frequency identification data corresponds to the data indicating the target frequency ft. [7] The output voltage adjustment process corresponds to the process shown in Figure 2. [8] The output voltage adjustment process corresponds to the process shown in Figure 6. [9] The diagnostic process corresponds to the process shown in Figure 9.

[0077] <Other Embodiments> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0078] "Regarding the Sampling Frequency Setting Unit 60" In the above embodiment, the resolution Δf of the coefficient data may be taken into consideration when setting the PWM frequency fpwm by the sampling frequency setting unit 60. However, the resolution Δf may be taken into consideration. Specifically, for example, the DFT circuit 36 ​​may perform a process to simultaneously determine the decimation interval M, the PWM frequency fpwm, and the number of calculations N. This makes it possible to more reliably suppress the situation in which it is not possible to set coefficient data that satisfies the resolution Δf despite performing the decimation process.

[0079] - It is not essential that the sampling frequency setting unit 60 be packaged together with the FFT 56, etc. - It is not essential that the control device 30 includes the sampling frequency setting unit 60 as a hardware processing circuit. For example, the processing in S20 and S22 may be performed by the CPU 32.

[0080] Regarding the thinning circuit: The number of thinning circuits provided by the control device 30 is not limited to one or two. For example, there may be three or more.

[0081] - It is not necessary for the decimation circuit to be packaged together with the Fourier transform circuit. - It is not necessary for the decimation circuit to perform the processes S24 to S28. For example, if the target frequency ft is predetermined to be one, the decimation circuit may simply be a circuit that performs decimation according to an invariant decimation interval M.

[0082] Regarding Fourier transform circuits: It is not necessary for the number of decimation circuits and the number of Fourier transform circuits to be the same. For example, one decimation circuit may be provided with multiple Fourier transform circuits. Here, if the sampling timing of the first data in the time series data of the transformation data used by different Fourier transform circuits to calculate the coefficient data is different, the update cycle of the coefficient data can be shortened.

[0083] - It is not necessary for the Fast Fourier Transform algorithm to be a Cooley-Tukey type FFT algorithm. - It is not necessary for the Fourier Transform circuit to be a circuit that calculates coefficient data based on the Fast Fourier Transform algorithm.

[0084] Regarding the DFT circuit: It is not essential that the DFT circuit 36 ​​includes a q-axis current calculation unit 52. Furthermore, it is not essential that the q-axis current iq input to the decimation circuit 54 is a value calculated by a hardware processing circuit. For example, the q-axis current iq input to the decimation circuit 54 may be a value calculated by the CPU 32.

[0085] "Regarding the conversion data" - The conversion data for the motor 14's current is not limited to the q-axis current iq. The conversion data for the motor 14's current may be, for example, the d-axis current id. The conversion data for the motor 14's current may be, for example, the current I. Also, for example, the conversion data for the motor 14's current may be the output line current of the inverter 16. Also, for example, the conversion data for the motor 14's current may be the α-phase current or β-phase current obtained by two-phase conversion of the output line current of the inverter 16. The conversion data for the motor 14's current may be, for example, the M-axis current or T-axis current obtained by coordinate transformation based on the angle of the primary magnetic flux of the motor 14. Note that the coordinate transformation used to generate the conversion data for the motor 14's current is not limited to those exemplified above.

[0086] The conversion data for the motor 14's current does not necessarily have to be data for a current that fluctuates moment by moment. The conversion data for the motor 14's current may be, for example, a quantity proportional to the amplitude of the output line current, α-phase current, or β-phase current, or the square of the same quantity. Alternatively, for example, the conversion data for the motor 14's current may be a quantity relating to the difference between the maximum and minimum values ​​of the q-axis current or d-axis current.

[0087] The conversion data for the motor 14 voltage is not limited to the input voltage Vin. The conversion data for the motor 14 voltage may be, for example, the output line voltage of the inverter 16. Alternatively, the conversion data for the motor 14 voltage may be the d-axis voltage or the q-axis voltage. The coordinate transformation used to generate the conversion data for the motor 14 voltage is not limited to a coordinate transformation to the d and q axes.

[0088] The conversion data for the motor 14 voltage does not necessarily have to be voltage data that fluctuates moment by moment. The conversion data for the motor 14 voltage may be a quantity proportional to the amplitude of the output line voltage, or the square of the same quantity. For example, the conversion data for the motor 14 voltage may be a quantity relating to the difference between the maximum and minimum values ​​of the d-axis voltage or the q-axis voltage.

[0089] The conversion data may be, for example, the instantaneous power of the motor 14. The conversion data related to power may be, for example, instantaneous imaginary power, apparent power, active power, or reactive power.

[0090] - The conversion data may be, for example, the armature flux linkage. The conversion data related to magnetic flux may be, for example, the d-axis magnetic flux or the q-axis magnetic flux. - The conversion data may also be, for example, physical quantities estimated using a physical model based on sensor detection values, such as magnetic pole position or motor 14 torque.

[0091] - The analog signal used to generate the digital data for conversion may be, for example, a magnetic pole position signal obtained from an encoder or the like. Alternatively, the analog signal used to generate the digital data for conversion may be a sound signal obtained from a sound sensor that senses the sound around the motor 14. Alternatively, the analog signal used to generate the digital data for conversion may be a temperature signal obtained from a temperature sensor that senses the temperature around the motor 14.

[0092] Regarding coefficient data: It is not mandatory for coefficient data to consist solely of data relating to the amplitude of the target frequency component. Coefficient data may, for example, include data relating to both the amplitude and phase of the target frequency component.

[0093] "Regarding countermeasures for load torque pulsation" - It is not essential that the manipulated variable for the load torque suppression process is the correction amount Δωc of the target angular velocity ω*. The manipulated variable for the load torque suppression process may be, for example, either the amplitude Va or the phase δ of the output voltage of the inverter 16.

[0094] The Fourier coefficients used as input for the processing to address load torque pulsation are not limited to Fourier coefficients for a single frequency. The Fourier coefficients used as input for the processing to address load torque pulsation may be Fourier coefficients for multiple different frequencies.

[0095] - It is not essential that the input variable for FFT56 used to calculate the Fourier amplitude Ift, which is the input for the processing to counteract load torque pulsation, be the q-axis current iq. The input variable for FFT56 may be, for example, the U-phase current. Alternatively, the input variable for FFT56 may be the current I.

[0096] "Regarding Torque Ripple Suppression Treatment Caused by Spatial Harmonics" - It is not essential that the manipulated variable for torque ripple suppression treatment caused by spatial harmonics be the phase δ. The manipulated variable for torque ripple suppression treatment caused by spatial harmonics may be, for example, the amplitude Va of the output voltage of the inverter 16.

[0097] - The input variable for the torque ripple suppression process caused by spatial harmonics does not necessarily have to be a Fourier coefficient for a single harmonic. For example, the input variable for the torque ripple suppression process caused by spatial harmonics may be a Fourier coefficient for multiple different harmonics.

[0098] Regarding output voltage adjustment processing: The dq-axis current feedback processing is not limited to processing using PD control. The dq-axis current feedback processing may, for example, use PID control. Furthermore, the dq-axis current feedback processing is not limited to classical control; for example, model predictive control may also be used.

[0099] - It is not mandatory for the output voltage adjustment process to include current feedback processing for the dq axis. For example, the output voltage adjustment process may be a process related to direct torque control.

[0100] Regarding the control variable of motor 14: It is not essential that the control variable of motor 14 be angular velocity ωm. The control variable of motor 14 may be, for example, the torque of motor 14.

[0101] Regarding rotating electric machines: The rotating electric machine is not limited to the motor 14 that drives the compressor 12. For example, it could be a motor mounted on a circulator.

[0102] Regarding the motor: The motor is not limited to embedded magnet synchronous motors; for example, an induction motor may also be used. Furthermore, the motor may be a brushed DC motor.

[0103] Regarding software processing circuits: It is not mandatory for a software processing circuit to be a CPU. For example, a software processing circuit may include both a CPU and a GPU.

[0104] Regarding the control device: The control object of the control device is not limited to the motor 14 that drives the compressor 12. As described above, the embodiments can be modified in various ways and details without departing from the spirit and scope of the claims.

[0105] 10...Air conditioning system 12...Compressor 14...Motor 30...Control device

Claims

1. A control device for controlling a control variable of a controlled object, comprising: a control circuit (32); an AD converter (38) for converting an analog signal into digital data; a decimation circuit (54); and a Fourier transform circuit (56), wherein the control circuit (32) is configured to perform a process for controlling the control variable based on first digital data which is the digital data obtained by converting a predetermined analog signal by the AD converter (38); the Fourier transform circuit (56) is configured to output coefficient data which is data indicating Fourier coefficients based on time-series data of the conversion data to the control circuit (32); the conversion data is second digital data which is the digital data obtained by converting the AD converter (38), or data calculated from the second digital data, the second digital data is data synchronized with the first digital data; and the decimation circuit (54) is a control device which is a circuit that selects the conversion data to be used for calculating the coefficient data by decimating the time-series data.

2. The control device according to claim 1, wherein the sampling frequency of the conversion data is equal to the sampling frequency of the first digital data input to the control circuit (32).

3. The control device according to claim 2, wherein the controlled object is a rotating electric machine (14), the output voltage of an inverter (16) is applied to the terminals of the rotating electric machine (14), the AD converter (38) is configured to convert the predetermined analog signal into first digital data at a frequency that is an integer multiple of the electrical angular frequency of the rotating electric machine (14), the control circuit (32) is configured to perform synchronous PWM processing, and the synchronous PWM processing is a process of setting the switching pattern of the inverter (16) based on the first digital data as an input variable each time the predetermined analog signal is converted into first digital data at a frequency that is an integer multiple of the frequency.

4. The control device according to any one of claims 1 to 3, wherein the decimation circuit (54) includes a first decimation circuit (54(1)) and a second decimation circuit (54(2)), the Fourier transform circuit (56) includes a first Fourier transform circuit (56(1)) and a second Fourier transform circuit (56(2)), the first decimation circuit (54(1)) and the second decimation circuit (54(2)) have different intervals for decimating the conversion data, the first Fourier transform circuit (56(1)) is configured to calculate the coefficient data using the conversion data decimated by the first decimation circuit (54(1)), and the second Fourier transform circuit (56(2)) is configured to calculate the coefficient data using the conversion data decimated by the second decimation circuit (54(2)).

5. The control device according to any one of claims 1 to 4, wherein the Fourier transform circuit (56) is configured to generate the coefficient data by fast Fourier transform.

6. The control device according to any one of claims 1 to 5, wherein the control circuit (32) is configured to input frequency identification data, which is data for identifying the frequency for which Fourier coefficients are to be obtained, to the Fourier transform circuit (56), and the decimation circuit (54) is configured to select the conversion data to be used for calculating the coefficient data by decimating the conversion data according to the frequency identification data.

7. The control device according to claim 3 and any one of claims 4 to 6 when referring to claim 3, wherein the rotating electric machine (14) is a motor that drives a compressor, the output voltage of an inverter (16) is configured to be applied to the terminals of the motor, the Fourier transform circuit (56) is configured to calculate coefficient data corresponding to a rational multiple of the mechanical angular frequency of the motor using the conversion data thinned by the thinning circuit (54), the control circuit (32) is configured to perform an output voltage adjustment process, and the output voltage adjustment process is configured to operate the output voltage of the inverter (16) based on the coefficient data as an input variable.

8. The control device according to claim 3 and any one of claims 4 to 7, when referring to claim 3, wherein the output voltage of an inverter (16) is applied to the terminals of the rotating electric machine (14), the Fourier transform circuit (56) is configured to calculate coefficient data corresponding to a frequency 3n times the electrical angular frequency of the rotating electric machine (14) (where n is a natural number of 1 or more) using the conversion data thinned by the thinning circuit (54), the control circuit (32) is configured to perform an output voltage adjustment process, and the output voltage adjustment process is configured to operate the output voltage of the inverter (16) based on the coefficient data as an input variable.

9. The control device according to claim 3 and any one of claims 4 to 8 when referring to claim 3, wherein the control circuit (32) is configured to perform a diagnostic process, the Fourier transform circuit (56) is configured to calculate coefficient data corresponding to a rational multiple of the mechanical angular frequency of the rotating electric machine (14) using the conversion data thinned by the thinning circuit (54), and the diagnostic process is a process of diagnosing whether or not there is an abnormality in the controlled object based on the coefficient data as an input variable.

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