Rotation speed identification system for rotary machine

Abstract

This rotation speed identification system 5 for a rotary machine 1 includes: a sensor 7 for measuring a state quantity of the rotary machine 1; and a processing circuit 61 for recording time history data which are measurement results of the sensor 7. The processing circuit 61 performs a frequency analysis on the time history data to create a frequency spectrum, and divides the frequency spectrum into a first section and a second section. Furthermore, the processing circuit 61 identifies one of first-to-third order frequencies of amplitude in the first section as an actual characteristic frequency of the rotary machine 1 on the basis of the first-to-third order frequencies of amplitude in the first section and at least one of first-to-third order frequencies of amplitude in the second section, and converts the frequency identified as the actual characteristic frequency into the rotation speed of the rotary machine.

Description

Rotation speed identification system for rotating machinery

[0001] The present disclosure relates to a rotation speed identification system for rotating machinery.

[0002] For rotating machinery such as hydraulic rotating machinery, electric motors, compressors, turbines, and bearings, there is a desire to grasp the rotation speed without using a rotation speed sensor. For example, Patent Document 1 describes a rotation speed measurement method for obtaining the rotation speed ω of a hydraulic rotating machine including a piston of a Z book from pressure pulsations.

[0003] Specifically, Patent Document 1 describes the following three equations as equations for calculating the rotation speed ω. f in Equation 1 ｎ and f ｎ－１ are the frequencies of the nth and n - 1th peak frequency components when the pressure pulsation is Fourier-transformed. fmax in Equation 2 is the frequency of the maximum amplitude when the pressure pulsation is Fourier-transformed. fc in Equation 3 is the frequency difference between adjacent peak frequency components when the pressure pulsation is Fourier-transformed, and is the frequency difference closest to the average value of those frequency differences. ω = 60·(f ｎ - f ｎ－１ ) / Z ··· (Equation 1) ω = 60·fmax / Z ··· (Equation 2) ω = 60·fc / Z ··· (Equation 3)

[0004] Japanese Patent No. 6968942

[0005] The rotation speed measurement method of Patent Document 1 assumes that in the frequency spectrum obtained by frequency analyzing the pressure pulsation, there are no frequency components with prominent amplitudes other than the characteristic frequency, which is the product of the rotation frequency and the number of pistons, and its harmonics (for example, twice or three times the characteristic frequency). However, when actually measuring the state quantity of a rotating machine with a sensor, there are frequency components with prominent amplitudes other than the characteristic frequency and its harmonics. In that case, an incorrect rotation speed is calculated by the rotation speed measurement method of Patent Document 1.

[0006] Therefore, an object of the present disclosure is to provide a rotation speed identification system for rotating machinery that can identify the correct rotation speed even when there are frequency components with prominent amplitudes other than the characteristic frequency and its harmonics.

[0007] This disclosure provides a rotational speed identification system for a rotating machine, comprising: a sensor for measuring state quantities of a rotating machine; and a processing circuit for recording time history data which is the measurement result of the sensor, wherein the processing circuit performs frequency analysis on the time history data to create a frequency spectrum, divides the frequency spectrum into a first section of low frequency bands and a second section of high frequency bands based on a base frequency range which is the variation range of a characteristic frequency which is the product of the rotational frequency and the number of rotating elements of the rotating machine, identifies one of the first to third amplitude frequencies in the first section as the actual characteristic frequency of the rotating machine based on at least one of the first to third amplitude frequencies in the second section, and converts the frequency identified as the actual characteristic frequency into the rotational speed of the rotating machine.

[0008] This disclosure provides a rotational speed identification system for a rotating machine, comprising: a sensor for measuring state quantities of a rotating machine; and a processing circuit for recording time history data which is the measurement result of the sensor, wherein the processing circuit performs frequency analysis on the time history data to create a frequency spectrum, divides the frequency spectrum into a first lower frequency band and a second higher frequency band based on a base frequency range which is the variation range of a characteristic frequency which is the product of the rotational frequency and the number of rotating elements of the rotating machine, identifies one of the first to third highest amplitude frequencies in the first band as the actual characteristic frequency of the rotating machine based on at least three frequencies in the first band including the first to third highest amplitude frequencies and at least three frequencies in the second band including the first to third highest amplitude frequencies, and converts the frequency identified as the actual characteristic frequency into the rotational speed of the rotating machine.

[0009] According to this disclosure, a rotational speed identification system for a rotating machine is provided that can identify the correct rotational speed even when there are frequency components with dominant amplitudes other than the characteristic frequency and its harmonics.

[0010] This is a schematic diagram of a rotating machine evaluation system according to one embodiment. This is an example of a frequency spectrum. This is another example of a frequency spectrum. This is a flowchart of the processing performed by the processing circuit. This is a flowchart of the processing performed by the processing circuit. This is a schematic diagram of a modified rotating machine evaluation system.

[0011] Figure 1 shows a rotational speed identification system 5 for a rotating machine 1 according to one embodiment. In this embodiment, the rotational speed identification system 5 includes a sensor 7 for measuring state variables of the rotating machine 1 and a control device 6 electrically connected to the sensor 7.

[0012] The rotating machine 1 has M rotating elements. In this embodiment, the rotating machine 1 is a hydraulic rotating machine 10. However, the rotating machine 1 may also be an electric motor, compressor, turbine, bearing, etc.

[0013] Furthermore, in this embodiment, the hydraulic rotary machine 10 is a hydraulic pump 10A that supplies working fluid to the hydraulic actuator 3 via a directional control valve 2. Moreover, in this embodiment, the hydraulic pump 10A is a swashplate type or swash-shaft type axial piston pump. That is, the number of rotating elements M mentioned above is the number of pistons.

[0014] However, the hydraulic pump 10A may be a gear pump or a vane pump, etc. If the hydraulic pump 10A is a gear pump, the number of rotating elements M is the number of teeth on the gear, and if the hydraulic pump 10A is a vane pump, the number of rotating elements M is the number of vanes.

[0015] Alternatively, the hydraulic rotating machine 10 may be an axial piston motor. In this case as well, the number of rotating elements M is the number of pistons. Furthermore, if the rotating machine 1 is an electric motor, the number of rotating elements M is half the number of poles; if the rotating machine 1 is a compressor or turbine, the number of rotating elements M is the number of blades; and if the rotating machine 1 is a rolling bearing, the number of rotating elements M is the number of rolling elements such as balls or rollers.

[0016] In Figure 1, the hydraulic actuator 3 is a double-acting cylinder, but the hydraulic actuator 3 may also be a hydraulic motor. Alternatively, the hydraulic actuator 3 may be a single-acting cylinder. Furthermore, if the hydraulic actuator 3 is a double-acting cylinder or a hydraulic motor, the hydraulic pump 10A may be a bidirectional pump that does not require a directional control valve 2 and is connected to the hydraulic actuator 3 to form a closed circuit.

[0017] The hydraulic pump 10A is driven by a prime mover 4. The prime mover 4 is either an engine or an electric motor. In this embodiment, the hydraulic pump 10A is a variable displacement type with a changeable tilt angle. However, the hydraulic pump 10A may also be a fixed displacement type.

[0018] In this embodiment, the rotating machine 1 is a hydraulic rotating machine 10, so the sensor 7 that measures the state quantities of the rotating machine 1 is a pressure sensor 7A that measures the pressure of the working fluid used in the hydraulic rotating machine 10. In this embodiment, the pressure sensor 7A measures the discharge pressure of the hydraulic pump 10A, which is the hydraulic rotating machine 10.

[0019] The control device 6 includes a processing circuit 61 that records time history data, which is the measurement result of the pressure sensor 7A, and a user interface 62 having a display screen that functions as an input and display device. The user interface 62 is, for example, a touchscreen. However, instead of the control device 6 including the user interface 62, an input and a display device may be electrically connected to the control device 6.

[0020] With respect to the control device 6, the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, dedicated processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions, or hardware programmed to perform the enumerated functions. The hardware may be hardware disclosed herein, or other known hardware that is programmed or configured to perform the enumerated functions. If the hardware is a processor, which is considered a type of circuit, then the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or the processor.

[0021] The processing circuit 61 uses the recorded time history data to identify the rotational speed of the hydraulic rotary machine 10. The processing performed by the processing circuit will be explained below with reference to the flowcharts shown in Figures 4 and 5.

[0022] The hydraulic rotary machine 10 operates between a minimum operating speed Nmin [rpm] and a maximum operating speed Nmax [rpm]. The minimum operating speed Nmin and the maximum operating speed Nmax are input to the control device 6 in advance via the user interface 62 and recorded in the processing circuit 61. The minimum operating speed Nmin divided by 60 is the minimum rotational frequency Fmin [Hz], and the maximum operating speed Nmax divided by 60 is the maximum rotational frequency Fmax [Hz]. Hereinafter, assuming that the hydraulic rotary machine 10 is mounted on construction machinery, we will assume that the minimum operating speed Nmin is 800 rpm and the maximum operating speed Nmax is 2000 rpm, but it goes without saying that the rotational speed range is not limited to this.

[0023] First, the processing circuit 61 performs frequency analysis on the recorded time history data to create a frequency spectrum as shown in Figure 2 or Figure 3 (step S1). The frequency analysis may be performed using either the Fast Fourier Transform or the Discrete Fourier Transform.

[0024] In the frequency spectrum, the amplitude is generally dominant at the characteristic frequency, which is the product of the rotation frequency and the number of rotational elements M, and at its harmonics (e.g., twice or three times the characteristic frequency). The nth multiple of the rotation frequency is the nth-order rotational component. For example, assuming that the number of pistons, M, is 9, the characteristic frequency is the 9th-order rotational component, and the harmonics of the characteristic frequency are the 18th and 27th-order rotational components.

[0025] Next, the processing circuit 61 divides the frequency spectrum into a first section of lower frequencies and a second section of higher frequencies based on the base frequency range (step S2). The base frequency range is the range of variation of the characteristic frequency, which is the product of the rotation frequency of the hydraulic rotary machine 10 and the number of rotating elements M. That is, the lower limit of the base frequency range is Fmin × M, and the upper limit is Fmax × M. Assuming that the minimum operating rotation speed Nmin is 800 rpm, the maximum operating rotation speed Nmax is 2000 rpm, and the number of pistons is 9, the base frequency range is 120 Hz or more and 300 Hz or less.

[0026] The first interval includes the base frequency range. The lower limit of the first interval is preferably greater than Fmin × (M-1) and less than or equal to Fmin × M. This is because, when the hydraulic rotary machine 10 is operated at the lowest rotation frequency Fmin, the rotation (M-1)th order component can be excluded from the first interval. For example, the lower limit of the first interval is 80% to 100% of the lower limit of the base frequency range. If the lower limit of the first interval is greater than Fmin × (M-1) or 80% or more of the lower limit of the base frequency range, then frequency components with dominant amplitudes and frequencies near zero can be excluded from the first interval, as shown in Figures 2 and 3. In this embodiment, we assume that the lower limit of the first interval is 108 Hz.

[0027] On the other hand, it is desirable that the upper limit of the first interval be less than three times the lower limit of the base frequency range. Furthermore, it is desirable that the upper limit of the first interval be greater than or equal to Fmax × M and less than Fmax × (M+1). This is because, when the hydraulic rotary machine 10 is operated at the maximum rotational frequency Fmax, the rotational (M+1)th order component can be prevented from being included in the first interval. For example, the upper limit of the first interval is 100% or more and 120% or less of the upper limit of the base frequency range. In this embodiment, we assume that the upper limit of the first interval is 330 Hz.

[0028] The second interval is the interval from the upper limit of the first interval. It is desirable that the upper limit of the second interval be greater than twice the upper limit of the base frequency range. Furthermore, it is desirable that the upper limit of the second interval be between 200% and 240% of the upper limit of the first interval, because this allows the second interval to be a relatively narrow range. In this embodiment, we assume that the upper limit of the second interval is 660 Hz.

[0029] After dividing the frequency spectrum into a first section and a second section, the processing circuit 61 selects the frequency F1-1 with the highest amplitude, the frequency F1-2 with the second highest amplitude, and the frequency F1-3 with the third highest amplitude in the first section, and selects the frequency F2-1 with the highest amplitude, the frequency F2-2 with the second highest amplitude, and the frequency F2-3 with the third highest amplitude in the second section (step S3).

[0030] Subsequently, the processing circuit 61 identifies one of the first to third amplitude frequencies F1-1, F1-2, F1-3 in the first section as the actual characteristic frequency of the hydraulic rotary machine 10, based on the first to third amplitude frequencies F1-1, F1-2, F1-3 in the first section and at least one of the first to third amplitude frequencies F2-1, F2-2, F2-3 in the second section (steps S4 to S6 and steps S11, S12, S14, S15).

[0031] First, the processing circuit 61 determines whether the highest frequency among the first to third highest amplitude frequencies F1-1, F1-2, and F1-3 in the first interval is twice the other frequencies (step S4). In both Figure 2 and Figure 3, the frequency F1-1, which is the highest amplitude frequency, is the highest frequency, so the processing circuit 61 determines whether F1-1 is twice F1-2 and whether F1-1 is twice F1-3.

[0032] In both Figure 2 and Figure 3, F1-1 is neither twice F1-2 nor twice F1-3. However, if the highest frequency among the first to third highest amplitude frequencies F1-1, F1-2, and F1-3 in the first interval is twice as high as the other frequencies (Yes in step S4), the processing circuit 61 determines whether the frequency that is twice as high as the highest frequency among F1-1, F1-2, and F1-3 is three times as high as the frequency F2-1, the highest amplitude frequency in the second interval (step S5).

[0033] If the frequency that is twice the highest frequency among F1-1, F1-2, and F1-3 is three times the frequency F2-1, which has the highest amplitude in the second interval (Yes in step S5), the processing circuit 61 identifies the frequency that is twice the highest frequency among F1-1, F1-2, and F1-3 as the actual characteristic frequency.

[0034] For example, if the frequency F1-2, which is the second highest amplitude frequency among F1-1, F1-2, and F1-3, is twice the frequency F1-1, which is the highest amplitude frequency, and three times the frequency F2-1, which is the highest amplitude frequency in the second section, the processing circuit 61 identifies the frequency F1-2, which is the second highest amplitude frequency in the first section, as the actual characteristic frequency.

[0035] On the other hand, if the frequency that is twice the highest frequency among F1-1, F1-2, and F1-3 is not three times the frequency F2-1, which has the highest amplitude in the second interval (No in step S5), the processing circuit 61 determines that it was not possible to identify the actual characteristic frequency and outputs no rotational speed (step S7).

[0036] In step S4, as shown in Figures 2 and 3, if the highest frequency among the first to third highest amplitude frequencies F1-1, F1-2, F1-3 in the first section does not have a twofold relationship with any of the other frequencies (No in step S4), the processing circuit 61 checks all possible pairs to determine if there are any pairs of first to third highest amplitude frequencies F1-1, F1-2, F1-3 in the first section that have a twofold relationship with the first to third highest amplitude frequencies F2-1, F2-2, F2-3 in the second section (step S11).

[0037] If, as a result of the determination in step S11, there is one pair between F1-1, F1-2, F1-3 and F2-1, F2-2, F2-3 that have a 2x relationship, the processing circuit 61 identifies the lower frequency of the pair with the 2x relationship as the actual characteristic frequency (step S12). In both Figure 2 and Figure 3, only the pair between the frequency F1-1, which has the highest amplitude in the first section, and the frequency F2-1, which has the highest amplitude in the second section, has a 2x relationship.

[0038] If, as a result of the determination in step S11, there are two or more pairs of F1-1, F1-2, F1-3 and F2-1, F2-2, F2-3 that have a 2x relationship, the processing circuit 61 determines whether the two or more pairs with a 2x relationship include a pair of the frequency F1-1 with the highest amplitude in the first section and the frequency F2-1 with the highest amplitude in the second section (step S14).

[0039] If two or more pairs that have the aforementioned 2x relationship include a pair of the frequency F1-1 with the highest amplitude in the first interval and the frequency F2-1 with the highest amplitude in the second interval (Yes in step S14), the processing circuit 61 identifies the frequency F1-1 with the highest amplitude in the first interval as the actual characteristic frequency.

[0040] On the other hand, if the pair of the frequency F1-1 with the highest amplitude in the first interval and the frequency F2-1 with the highest amplitude in the second interval is not included in the two or more pairs that have the aforementioned 2x relationship (No in step S14), the processing circuit 61 determines that it was not possible to identify the actual characteristic frequency and outputs no rotational speed (step S16).

[0041] Further, as a result of the determination in step S11, if there is no pair having a double relationship between F1-1, F1-2, F1-3 and F2-1, F2-2, F2-3, the processing circuit 61 outputs no rotational speed on the assumption that the identification of the actual characteristic frequency was impossible (step S13).

[0042] After identifying the actual characteristic frequency of the hydraulic rotary machine 10, the processing circuit 61 identifies the rotational speed by converting the frequency identified as the actual characteristic frequency into the rotational speed of the hydraulic rotary machine 10 (step S8). Specifically, the processing circuit 60 multiplies the frequency identified as the actual characteristic frequency by 60 / M. Thereafter, the processing circuit 61 displays the identified rotational speed of the hydraulic rotary machine 10 on the display screen of the user interface 62.

[0043] As described above, in the rotational speed identification system 5 of the present embodiment, since the first section includes the base frequency range, the characteristic frequency is always included in the first section. Also, since the upper limit of the first section is less than three times the lower limit of the base frequency range, the third harmonic of the characteristic frequency is not included in the first section. Further, since the upper limit of the second section is greater than twice the upper limit of the base frequency range, the second harmonic of the characteristic frequency is included in either the first section or the second section. Thus, by setting the first section and the second section such that the characteristic frequency is included in the first section, the second harmonic of the characteristic frequency is included in either the first section or the second section, and the third harmonic of the characteristic frequency is not included in the first section, the correct rotational speed can be identified based on at least one of the frequencies of the first to third amplitudes in the first section and the frequencies of the first to third amplitudes in the second section.

[0044] Also, in the present embodiment, by the processing of steps S4 to S6, the rotational speed can be identified when the second harmonic of the characteristic frequency is included in the first section, and by steps S11 and S12, the rotational speed can be identified when the second harmonic of the characteristic frequency is included in the second section.

[0045] Furthermore, in the present embodiment, by the processes of steps S14 and S15, an appropriate pair can be selected from two or more pairs that have a two-fold relationship between the frequencies F1-1, F1-2, F1-3 of the first to third amplitudes in the first section and the frequencies F2-1, F2-2, F2-3 of the first to third amplitudes in the second section.

[0046] <Modification Example> The present disclosure is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present disclosure.

[0047] For example, like the rotational speed identification system 5A of the modification example shown in FIG. 6, the hydraulic pump 10A may be a double pump including a first pump 10a and a second pump 10b, and the sensor 7 may include a first pressure sensor 7B that measures the discharge pressure of the first pump 10a and a second pressure sensor 7C that measures the discharge pressure of the second pump 10b.

[0048] In this case, the processing circuit 61 may perform frequency analysis on the time history data, which is the measurement result of the first pressure sensor 7B, to create a first frequency spectrum, perform frequency analysis on the time history data, which is the measurement result of the second pressure sensor 7C, to create a second frequency spectrum, and then multiply the amplitudes of the first frequency spectrum and the second frequency spectrum for each frequency to create a frequency spectrum divided into a first section and a second section. With this configuration, when the hydraulic pump 10A is a double pump, the rotational speed can be identified with high accuracy.

[0049] The processing circuit 61 may identify one of the first to third amplitude frequencies F1-1, F1-2, F1-3 in the first section as the characteristic frequency of the hydraulic rotary machine 10, based on at least three frequencies including the first to third amplitude frequencies F1-1, F1-2, F1-3 in the first section and at least three frequencies including the first to third amplitude frequencies F2-1, F2-2, F2-3 in the second section. In this case as well, the correct rotational speed can be identified based on at least three frequencies including the first to third amplitude frequencies F1-1, F1-2, F1-3 in the first section and at least three frequencies including the first to third amplitude frequencies 2-1, F2-2, F2-3 in the second section.

[0050] For example, the processing circuit 61 may identify one of the frequencies of the first to third amplitudes in the first section as the characteristic frequency of the hydraulic rotary machine 10, based on the frequencies of the first to fourth amplitudes in the first section and the frequencies of the first to fourth amplitudes in the second section. The processing in this case is the same as in the embodiment described above. Furthermore, even if the rotary machine 1 is not the hydraulic rotary machine 10, the characteristic frequency of the rotary machine 1 can be identified using the same processing as in the embodiment described above.

[0051] Furthermore, if the rotating machine 1 is an axial piston motor, the sensor 7 that measures the state variables of the rotating machine 1 may be a pressure sensor that measures the inflow pressure of the axial piston motor as the pressure of the working fluid used in the hydraulic rotating machine 10.

[0052] <Summary> In a first aspect, the present disclosure provides a rotational speed identification system for a rotating machine, comprising: a sensor for measuring state quantities of a rotating machine; and a processing circuit for recording time history data which is the measurement result of the sensor, wherein the processing circuit performs frequency analysis on the time history data to create a frequency spectrum, divides the frequency spectrum into a first section of low frequency bands and a second section of high frequency bands based on a base frequency range which is the variation range of a characteristic frequency which is the product of the rotational frequency and the number of rotating elements of the rotating machine, identifies one of the first to third amplitude frequencies in the first section as the actual characteristic frequency of the rotating machine based on at least one of the first to third amplitude frequencies in the second section, and converts the frequency identified as the actual characteristic frequency into the rotational speed of the rotating machine.

[0053] According to the above configuration, by setting the first and second sections so that the characteristic frequency is included in the first section, the second harmonic of the characteristic frequency is included in either the first or second section, and the third harmonic of the characteristic frequency is not included in the first section, the correct rotational speed can be identified based on at least one of the first to third amplitude frequencies in the first section and the first to third amplitude frequencies in the second section.

[0054] As a second aspect, the present disclosure provides a rotational speed identification system for a rotating machine, comprising: a sensor for measuring state quantities of a rotating machine; and a processing circuit for recording time history data which is the measurement result of the sensor, wherein the processing circuit performs frequency analysis on the time history data to create a frequency spectrum, divides the frequency spectrum into a first lower frequency band and a second higher frequency band based on a base frequency range which is the variation range of a characteristic frequency which is the product of the rotational frequency and the number of rotating elements of the rotating machine, identifies one of the first to third highest amplitude frequencies in the first band as the actual characteristic frequency of the rotating machine based on at least three frequencies in the first band including the first to third highest amplitude frequencies and at least three frequencies in the second band including the first to third highest amplitude frequencies, and converts the frequency identified as the actual characteristic frequency into the rotational speed of the rotating machine.

[0055] According to the above configuration, by setting the first and second sections so that the characteristic frequency is included in the first section, the second harmonic of the characteristic frequency is included in either the first or second section, and the third harmonic of the characteristic frequency is not included in the first section, the correct rotational speed can be identified based on at least three frequencies in the first section that include the first to third highest amplitude frequencies and at least three frequencies in the second section that include the first to third highest amplitude frequencies.

[0056] In a third embodiment, in the first or second embodiment, the first interval includes the base frequency range, the upper limit of the first interval is less than three times the lower limit of the base frequency range, and the second interval is the interval from the upper limit of the first interval, the upper limit of the second interval may be greater than twice the upper limit of the base frequency range. With this configuration, since the first interval includes the base frequency range, the characteristic frequency is always included in the first interval. Also, since the upper limit of the first interval is less than three times the lower limit of the base frequency range, the third harmonic of the characteristic frequency is never included in the first interval. Furthermore, since the upper limit of the second interval is greater than twice the upper limit of the base frequency range, the second harmonic of the characteristic frequency will be included in either the first or second interval.

[0057] In a fourth embodiment, in any of the first to third embodiments, the lower limit of the first interval may be 80% or more and 100% or less of the lower limit of the base frequency range. With this configuration, frequency components with dominant amplitudes and frequencies near zero can be excluded from the first interval.

[0058] In a fifth embodiment, in the first to third embodiments, when the lowest rotational frequency of the rotating machine is Fmin and the number of rotational elements of the rotating machine is M, the lower limit of the first interval may be greater than Fmin × (M-1) and less than or equal to Fmin × M. With this configuration, frequency components with dominant amplitudes near zero frequency can be excluded from the first interval. Moreover, when the rotating machine is operated at the lowest rotational frequency, the rotational (M-1)th order component can be ensured not to be included in the first interval.

[0059] In a sixth embodiment, in any of the first to fifth embodiments, the upper limit of the first section may be 100% or more and 120% or less of the upper limit of the base frequency range, and the upper limit of the second section may be 200% or more and 240% or less of the upper limit of the first section. With this configuration, the second section can be made to a somewhat narrow range.

[0060] In a seventh aspect, in any of the first to fifth aspects, when the maximum rotational frequency of the rotating machine is Fmax and the number of rotational elements of the rotating machine is M, the upper limit of the first interval may be Fmax × M or greater and less than Fmax × (M+1), and the upper limit of the second interval may be 200% or more and 240% or less of the upper limit of the first interval. With this configuration, the second interval can be made to a relatively narrow range. Moreover, when the rotating machine is operated at the maximum rotational frequency, the first interval can be made so as not to include the (M+1)th rotational component.

[0061] In an eighth aspect, in any of the first to seventh aspects, the processing circuit may determine whether the frequency with the 2x relationship and the frequency with the 1st amplitude in the second section are 3x relationship when the highest frequency among the first to third amplitude frequencies in the first section is twice the other frequency, and if they are 3x, identify the frequency with the 2x relationship as the actual feature frequency. With this configuration, the rotational speed can be identified when the 2x harmonic of the feature frequency is included in the first section.

[0062] In a ninth aspect, in the eighth aspect, if the highest frequency among the first to third most amplitude frequencies in the first section is not twice as high as any of the other frequencies, the processing circuit may determine whether there is a pair of frequencies that are twice as high as the first to third most amplitude frequencies in the first section and the first to third most amplitude frequencies in the second section. If there is one such pair, the lower frequency of the pair that is twice as high may be identified as the actual characteristic frequency. With this configuration, the rotational speed can be identified when the second section contains a harmonic that is twice the characteristic frequency.

[0063] In a tenth embodiment, in the ninth embodiment, the processing circuit may, if there are two or more pairs that have a 2x relationship, determine whether the two or more pairs include a pair of the frequency with the highest amplitude in the first section and the frequency with the highest amplitude in the second section. If the two or more pairs include a pair of the frequency with the highest amplitude in the first section and the frequency with the highest amplitude in the second section, the frequency with the highest amplitude in the first section may be identified as the actual characteristic frequency. With this configuration, an appropriate pair can be selected from two or more pairs that have a 2x relationship between the frequencies with the highest to third highest amplitude in the first section and the frequencies with the highest to third highest amplitude in the second section.

[0064] In an eleventh embodiment, in any of the first to tenth embodiments, for example, when the number of rotating elements of the rotating machine is M, the processing circuit may convert the frequency identified as the actual characteristic frequency into the rotational speed of the rotating machine by multiplying the frequency identified as the actual characteristic frequency by 60 / M.

[0065] In a twelfth embodiment, in any of the first to eleventh embodiments, for example, the rotating machine may be a hydraulic rotating machine, and the state variable may be the pressure of the working fluid used in the hydraulic rotating machine.

[0066] In a thirteenth embodiment, in the twelfth embodiment, the hydraulic rotary machine is a hydraulic pump including a first pump and a second pump, the sensor includes a first pressure sensor for measuring the discharge pressure of the first pump and a second pressure sensor for measuring the discharge pressure of the second pump, the processing circuit may create a first frequency spectrum by frequency analysis of the measurement result of the first pressure sensor, create a second frequency spectrum by frequency analysis of the measurement result of the second pressure sensor, and create a frequency spectrum divided into a first section and a second section by multiplying the amplitude of the first frequency spectrum and the amplitude of the second frequency spectrum for each frequency. With this configuration, the rotational speed can be identified with high accuracy when the hydraulic pump is a double pump.

[0067] 1 Rotating machine 10 Hydraulic rotating machine 10A Hydraulic pump 5, 5A Evaluation system 61 Processing circuit 7 Sensors 7A Pressure sensor 7B First pressure sensor 7C Second pressure sensor

Claims

1. A rotational speed identification system for a rotating machine, comprising: a sensor for measuring state quantities of a rotating machine; and a processing circuit for recording time history data which is the measurement result of the sensor, wherein the processing circuit is configured to: perform frequency analysis on the time history data to create a frequency spectrum; divide the frequency spectrum into a first lower frequency band and a second higher frequency band based on a base frequency range which is the variation range of a characteristic frequency which is the product of the rotational frequency and the number of rotating elements of the rotating machine; identify one of the first to third highest amplitude frequencies in the first band as the actual characteristic frequency of the rotating machine based on at least one of the first to third highest amplitude frequencies in the first band and at least one of the first to third highest amplitude frequencies in the second band; and convert the frequency identified as the actual characteristic frequency into the rotational speed of the rotating machine.

2. A rotational speed identification system for a rotating machine, comprising: a sensor for measuring state quantities of a rotating machine; and a processing circuit for recording time history data which is the measurement result of the sensor, wherein the processing circuit is configured to: perform frequency analysis on the time history data to create a frequency spectrum; divide the frequency spectrum into a first lower frequency band and a second higher frequency band based on a base frequency range which is the variation range of a characteristic frequency which is the product of the rotational frequency and the number of rotating elements of the rotating machine; identify one of the first to third highest amplitude frequencies in the first band as the actual characteristic frequency of the rotating machine based on at least three frequencies in the first band including the first to third highest amplitude frequencies and at least three frequencies in the second band including the first to third highest amplitude frequencies; and convert the frequency identified as the actual characteristic frequency into the rotational speed of the rotating machine.

3. The rotational speed identification system for a rotating machine according to claim 1 or 2, wherein the first interval includes the base frequency range, the upper limit of the first interval is less than three times the lower limit of the base frequency range, and the second interval is an interval from the upper limit of the first interval, the upper limit of the second interval is greater than twice the upper limit of the base frequency range.

4. The rotational speed identification system for a rotating machine according to claim 1 or 2, wherein the lower limit of the first interval is 80% or more and 100% or less of the lower limit of the base frequency range.

5. The rotational speed identification system for a rotating machine according to claim 1 or 2, wherein, when the minimum rotational frequency of the rotating machine is Fmin and the number of rotational elements of the rotating machine is M, the lower limit of the first interval is greater than Fmin × (M-1) and less than or equal to Fmin × M.

6. The rotational speed identification system for a rotating machine according to claim 1 or 2, wherein the upper limit of the first interval is 100% or more and 120% or less of the upper limit of the base frequency range, and the upper limit of the second interval is 200% or more and 240% or less of the upper limit of the first interval.

7. The rotational speed identification system for a rotating machine according to claim 1 or 2, wherein, when the maximum rotational frequency of the rotating machine is Fmax and the number of rotating elements of the rotating machine is M, the upper limit of the first interval is greater than or equal to Fmax × M and less than Fmax × (M + 1), and the upper limit of the second interval is 200% or more and 240% or less of the upper limit of the first interval.

8. The rotational speed identification system for a rotating machine according to claim 1 or 2, wherein the processing circuit determines whether, if the highest frequency among the first to third most amplitude frequencies in the first section is twice as high as any other frequency, the frequency having a twice relationship is three times as high as the frequency with the highest amplitude in the second section, and if it is three times as high, identifies the frequency having a twice relationship as the actual characteristic frequency.

9. The rotational speed identification system for a rotating machine according to claim 8, wherein the processing circuit determines, if the highest frequency among the first to third most amplitude frequencies in the first section is not twice as high as any of the other frequencies, whether there is a pair between the first to third most amplitude frequencies in the first section and the first to third most amplitude frequencies in the second section that is twice as high 10. The rotational speed identification system for a rotating machine according to claim 9, wherein the processing circuit determines whether, if there are two or more pairs having the relationship of 2, the two or more pairs include a pair of the frequency with the highest amplitude in the first section and the frequency with the highest amplitude in the second section, and if the two or more pairs include a pair of the frequency with the highest amplitude in the first section and the frequency with the highest amplitude in the second section, the processing circuit identifies the frequency with the highest amplitude in the first section as the actual characteristic frequency.

11. When the number of rotating elements of the rotating machine is M, the processing circuit converts the frequency identified as the actual characteristic frequency into the rotational speed of the rotating machine by multiplying the frequency identified as the actual characteristic frequency by 60 / M, the rotational speed identification system for a rotating machine according to claim 1 or 2.

12. The rotational speed identification system for a rotating machine according to claim 1 or 2, wherein the rotating machine is a hydraulic rotating machine, and the state variable is the pressure of the working fluid used in the hydraulic rotating machine.

13. The rotational speed identification system for a rotating machine according to claim 12, wherein the hydraulic rotating machine is a hydraulic pump including a first pump and a second pump, the sensor includes a first pressure sensor for measuring the discharge pressure of the first pump and a second pressure sensor for measuring the discharge pressure of the second pump, the processing circuit creates a first frequency spectrum by frequency analysis of the measurement result of the first pressure sensor, creates a second frequency spectrum by frequency analysis of the measurement result of the second pressure sensor, and creates a frequency spectrum divided into a first section and a second section by multiplying the amplitude of the first frequency spectrum and the amplitude of the second frequency spectrum for each frequency.

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