阅读说明：本技术 电流测定系统、诊断系统 (Current measurement system and diagnostic system ) 是由 佐藤裕太 市桥弘英 池田和隆 于 2020-02-25 设计创作，主要内容包括：电流测定系统构成为对流过导体的、具有测定范围内的频率的交流电流进行测定。该电流测定系统具备：电流传感器,其具有构成为与导体磁耦合的测定线圈；以及分流电阻,其与测定线圈并联且两端与测定线圈的两端电连接。相对于交流电流的频率的、分流电阻的两端之间的输出电压在饱和频率下在饱和点饱和。频率的测定范围的上限值比交流电流的基本频率高。饱和频率为上限值以上。该电流测定系统能够提高对于比交流电流的基本频率高的频率成分的灵敏度。(The current measuring system is configured to measure an alternating current flowing through the conductor and having a frequency within a measurement range. The current measurement system includes: a current sensor having a measurement coil configured to magnetically couple to a conductor; and a shunt resistor connected in parallel with the measurement coil and having both ends electrically connected to both ends of the measurement coil. The output voltage between the two ends of the shunt resistance with respect to the frequency of the alternating current is saturated at a saturation point at a saturation frequency. The upper limit value of the frequency measurement range is higher than the fundamental frequency of the alternating current. The saturation frequency is not less than the upper limit. The current measuring system can improve the sensitivity to frequency components higher than the fundamental frequency of the alternating current.)

1. A current measurement system configured to measure an alternating current flowing through a conductor and having a frequency within a measurement range, the current measurement system comprising:

a current sensor having a measurement coil configured to magnetically couple to the conductor; and

a shunt resistor having two ends electrically connected to the two ends of the measurement coil,

wherein an output voltage between the two ends of the shunt resistance with respect to a frequency of the alternating current is saturated at a saturation point at a saturation frequency,

the upper limit value of the measurement range of the frequency is higher than the fundamental frequency of the alternating current,

the saturation frequency is equal to or higher than the upper limit value.

2. The amperometric detection system of claim 1,

in the measurement range, the output voltage increases as the frequency becomes higher.

3. Amperometric system according to claim 1 or 2,

the correlation of the frequency of the alternating current with the output voltage in the measurement range is represented by a straight line having a positive slope.

4. Amperometric system according to any one of claims 1 to 3,

the output voltage V2 is expressed by the following equation based on the alternating current I1, a coupling coefficient k of the conductor and the measurement coil, the frequency f of the alternating current, a self-inductance L1 of the measurement coil, a reactance R1 of the measurement coil, a resistance value R2 of the shunt resistance, and the number of turns N of the measurement coil,

[ numerical formula 3]

5. Amperometric system according to any one of claims 1 to 4,

the magnitudes of the self-inductance and reactance of the measurement coil and the resistance value of the shunt resistance are such that the saturation frequency is equal to or higher than the upper limit value of the measurement range.

6. Amperometric system according to any one of claims 1 to 5,

the upper limit value of the measurement range is ten times or more of the fundamental frequency of the alternating current.

7. Amperometric system according to any one of claims 1 to 6,

the current sensor also has a core having a portion that passes through the inside of the measurement coil.

8. Amperometric detection system according to any one of claims 1 to 7,

the ac power supply device further includes an analysis unit that performs frequency analysis on the time-series data of the output voltage to acquire data of a harmonic component of the ac current.

9. A diagnostic system configured to diagnose a driving device for driving a device, the diagnostic system comprising:

an amperometric system according to any one of claims 1 to 8; and

a determination section that determines a state of the device based on an output of the current measurement system,

wherein the driving means is supplied with the alternating current to drive the device.

Technical Field

The present disclosure relates to a current measurement system for measuring an alternating current and a diagnostic system including the current measurement system.

Background

Patent document 1 discloses a current measuring device (current measuring system). The current measurement system of patent document 1 includes a current sensor. In the current sensor, a detection coil is wound around a magnetic core annularly arranged around a conductor to be measured, and a shunt is connected between each of a high-potential-side output terminal and a ground-side output terminal of the detection coil.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2012 and 68191

Disclosure of Invention

The current measuring system is configured to measure an alternating current flowing through the conductor and having a frequency within a measurement range. The current measurement system includes: a current sensor having a measurement coil configured to magnetically couple to a conductor; and a shunt resistor connected in parallel with the measurement coil and having both ends electrically connected to both ends of the measurement coil. The output voltage between the two ends of the shunt resistance with respect to the frequency of the alternating current is saturated at a saturation point at a saturation frequency. The upper limit value of the frequency measurement range is higher than the fundamental frequency of the alternating current. The saturation frequency is not less than the upper limit.

The current measuring system can improve the sensitivity to frequency components higher than the fundamental frequency of the alternating current.

Drawings

Fig. 1 is a configuration diagram of a diagnostic system including a current measurement system according to an embodiment.

Fig. 2 is a circuit diagram of the measuring unit of the current measuring system according to the above embodiment.

Fig. 3 is an explanatory view of the measurement principle of the current measurement system according to the above embodiment.

Fig. 4 is an explanatory diagram of the frequency characteristic of the output of the current measuring system of the above embodiment.

Fig. 5 is a graph showing the frequency characteristics of the sensitivity of the current measurement system according to the above embodiment.

Fig. 6 is a graph showing the frequency characteristics of the sensitivity of the current measurement system of the comparative example.

Fig. 7 is a graph showing frequency components obtained in the current measurement system of the above embodiment.

Fig. 8 is a graph showing frequency components obtained in the current measurement system of the comparative example.

Fig. 9 is a graph showing frequency components obtained in the current measurement system of the above embodiment.

Fig. 10 is a graph showing frequency components obtained in the current measurement system of the comparative example.

Fig. 11 is a graph of frequency components of the alternating current obtained in the current measurement system of the above embodiment.

Fig. 12 is a graph of frequency components of the alternating current obtained in the current measurement system of the above embodiment.

Fig. 13 is a graph of frequency components of an alternating current obtained in the current measurement system of the comparative example.

Fig. 14 is a graph of frequency components of an alternating current obtained in the current measurement system of the comparative example.

Fig. 15 is a flowchart of the operation of the diagnostic system.

Detailed Description

(1) Detailed description of the preferred embodiments

(1.1) outline

Fig. 1 shows a diagnostic system 10 including a current measurement system 20 according to the present embodiment. Fig. 2 is a circuit diagram of the current measuring system. The current measurement system 20 is configured to measure an alternating current I1 flowing through the conductor 32. As shown in fig. 2, the current measurement system 20 includes: a current sensor 22 having a measurement coil 220 magnetically coupled to the conductor 32; and a shunt resistor 23 electrically connected between both ends 220a and 220b of the measurement coil 220. The shunt resistor 23 is connected in parallel with the measurement coil 220 and connected to both ends 220a and 220b of the measurement coil 220. The current measuring system 20 has a saturation point at which the output voltage V2 between the two ends of the shunt resistance 23 with respect to the frequency of the alternating current I1 is saturated at the saturation frequency. The upper limit value of the measurement range of the frequency of the alternating current I1 is higher than the fundamental frequency of the alternating current I1. The saturation frequency is not less than the upper limit of the measurement range.

In the current measuring system 20, an induced current corresponding to the ac current I1 flows through the measuring coil 220, and the output voltage V2 between the both ends 23a and 23b of the shunt resistor 23 has a value corresponding to the induced current. Also, in a range of frequencies lower than the saturation frequency at the saturation point, the output voltage V2 becomes larger as the frequency increases. In the current measurement system 20, the saturation frequency is higher than the fundamental frequency of the alternating current I1 and is equal to or higher than the upper limit value of the measurement range. According to the current measurement system 20 of the present embodiment, the sensitivity to a frequency component higher than the fundamental frequency of the ac current I1 can be improved.

(1.2) details

The diagnostic system 10 including the current measurement system 20 according to the present embodiment will be described in further detail below. The diagnostic system 10 is configured to diagnose the device 30. As an example, the device 30 diagnosed by the diagnostic system 10 is a working device. The job device is a device that executes a predetermined job. Examples of the predetermined operation include processing, conveying, arranging, and mounting of a material or an article. The machining includes, for example, physical processing such as boring, drilling, tapping, cutting, grinding, and chemical processing such as heating and cooling. The conveyance includes not only conveyance of solid articles such as parts and products but also conveyance of fluid in the flow path. Examples of such a working machine include machine tools such as lathes, machining centers, end mills, grinders, and drills, component mounting machines, conveyors, heat treatment apparatuses, pumps (e.g., vacuum pumps), compressors, polishing apparatuses (e.g., chemical mechanical polishing apparatuses), and combinations thereof.

(1.2.1) apparatus

As an example, the apparatus 30 functions as a lathe. The apparatus 30 may have a function as a machining center. The device 30 comprises a drive means 31 and a power supply means 33.

The driving device 31 is a device for driving the mechanism portion. In other words, the driving device 31 is a power source of the mechanism portion. The drive means 31 comprise a motor. The output of the motor varies according to the applied current. The mechanism unit is a device for performing a predetermined operation. The predetermined operation is an operation of machining the workpiece by rotating one of the tool and the workpiece relative to the other. That is, the apparatus 30 is a device for processing a workpiece to obtain a member of a desired shape. In an embodiment, the mechanism portion machines the workpiece by rotating the workpiece with respect to the tool. That is, the apparatus 30 has a function as a lathe. A tool is a member for machining a workpiece. The tool can be replaced. As an example, the workpiece is a metal body.

The motor is used to hold the tool at a predetermined position with respect to the workpiece in a direction along a central axis of rotation of the workpiece. That is, the driving device 31 is configured to: one of the tool and the workpiece is pressed against the other by the motor in a direction along a central axis of rotation of the other of the tool and the workpiece. In the present embodiment, the direction in which the output shaft of the rotor of the motor rotates is a direction along the central axis of rotation of one of the tool and the workpiece relative to the other, but is not limited thereto.

The motor is an ac motor that operates in an ac manner. The ac motor may be a three-phase ac motor or a single-phase ac motor. Specifically, the output of the motor, that is, the rotation speed of the motor, which is the number of revolutions per unit time, changes in accordance with a change in the fundamental frequency of the applied alternating current. For example, if the fundamental frequency becomes high, the output becomes large, that is, the rotation of the output shaft becomes fast, and if the fundamental frequency becomes low, the output becomes small, that is, the rotation of the output shaft becomes slow.

The power supply device 33 supplies an alternating current I1 to the motor of the drive device 31. In particular, the power supply device 33 supplies an ac current I1 to the motor of the drive device 31 in order to cause the mechanism unit to perform a predetermined operation. That is, the current I1 is supplied to the drive device 31 while the apparatus 30 is executing a prescribed job. The power supply device 33 is connected to the motor via a conductor 32 as an electric wire. In the present embodiment, the alternating current I1 has a fundamental frequency. The power supply device 33 has a function of adjusting the fundamental frequency of the alternating current I1. The power supply device 33 can be realized by a known ac power supply circuit, and therefore, a detailed description thereof is omitted.

(1.2.2) diagnostic System

The diagnostic system 10 determines the state of the tool as the state of the device 30. The state of the cutter is roughly classified into two types according to the presence or absence of damage. If the tool is not damaged, the diagnostic system 10 determines that the state of the device 30 is normal. Examples of damage to the tool include flank wear (flank wear), rake wear (crater wear), chipping, plastic deformation, chipping (welding), thermal cracking (thermal cracking), boundary wear, and chipping. Here, if the same device 30 is used, the wear of the tool will occur in the same manner. However, it is difficult to determine which kind of defect has occurred piece by piece for the same apparatus 30 regarding the defect of the tool and its sign. That is to say. The damage to the tool may be a damage that is easily determined or a damage that is difficult to determine. In the presence of damage to the tool, which is easily determined, the diagnostic system 10 determines the state of the device 30 as abnormal. On the other hand, in the case where there is a damage of the tool that is difficult to specify, the diagnostic system 10 determines the state of the device 30 as an indeterminate state. That is, the abnormality in the present embodiment is an abnormality known to the diagnostic system 10, and the indeterminate state is an abnormality unknown to the diagnostic system 10. The unknown abnormality also includes a sign of a defect.

As shown in fig. 1, the diagnostic system 10 includes a measuring unit 21, an acquiring unit 11, an extracting unit 12, a determining unit 13, an output unit 14, a collecting unit 15, a generating unit 16, and a storage unit 17. In the diagnostic system 10, the acquisition unit 11 and the extraction unit 12 constitute an analysis unit 24. The measuring unit 21 and the analyzing unit 24 constitute a current measuring system 20.

The measuring section 21 measures the ac current I1 and outputs waveform data (current waveform data) indicating a waveform related to the ac current I1. In the present embodiment, the measuring unit 21 measures the ac current I1 supplied to the driving device 31 of the instrument 30. The measuring portion 21 is attached to a conductor 32, and the conductor 32 is an electric wire through which an ac current I1 flows from the power supply device 33 to the drive device 31. As shown in fig. 1 and 2, the measuring unit 21 includes a current sensor 22 and a shunt resistor 23.

As shown in fig. 2, the current sensor 22 includes a measuring coil 220 and a core 221. The measurement coil 220 is disposed in the vicinity of the conductor 32 as a wire through which an alternating current I1 to be measured flows. More specifically, the measurement coil 220 is magnetically coupled to the conductor 32, which is a wire through which the ac current I1 flows. The core 221 has a portion 221b passing through the inside of the measurement coil 220. In the present embodiment, the core 221 has an annular shape enclosing the hollow portion 221 a. The core 221 is disposed so that the conductor 32 (wire) through which the alternating current I1 to be measured flows passes through the hollow portion 221a of the core 221. In the present embodiment, the current sensor 22 is a current transformer. In particular, the current transformer is preferably post-mountable to the conductor 32. That is, in the present embodiment, the measuring section 21 can be mounted on the conductor 32.

The shunt resistor 23 is electrically connected between both ends 220a and 220b of the measurement coil 220. The output voltage V2 between the two ends 23a, 23b of the shunt resistor 23 is the output of the measuring section 21.

Next, a relationship between the current I1 to be measured and the output voltage V2 as the output of the measuring unit 21 will be described. Fig. 3 is an equivalent circuit diagram of the measuring section 21. In fig. 3, the capacitance component of the measurement coil 220 is ignored. In fig. 3, the conductor 32 through which the alternating current I1 flows has a self-inductance L0. The measurement coil 220 has a self-inductance L1 and a reactance R1. The shunt resistor 23 has a resistance value R2. The conductor 32 is applied with a voltage V1. More specifically, the voltage V is the sum of the self-induced electromotive force caused by the current I1 and the electromotive force caused by the mutual inductance of the conductor 32 and the measurement coil 220. The mutual inductance M is the mutual inductance between the conductor 32 and the measurement coil 220. A current I2 flows in the shunt resistor 23.

Based on the above parameters and the angular frequency ω of the alternating current I1, the voltages V1, V2 are represented by the numerical expression 1.

[ numerical formula 1]

V1＝-jω·L0·Il+jω·M·I2

V2＝jω·M·I1-jω·L1·I2-R1·I2

Since the voltage V2 is equal to the product of the resistance R2 and the current I2 (R2 · I2), the voltage V2 can be expressed by equation 2.

[ numerical formula 2]

Voltage V2 is expressed by equation 3 based on coupling coefficient k of conductor 32 and measurement coil 220, frequency f of alternating current I1, and number of turns N of measurement coil 220.

[ numerical formula 3]

When the frequency f is low, the voltage V2 can be expressed by equation 4, and the voltage V2 is proportional to the frequency f.

[ numerical formula 4]

Fig. 4 is an explanatory diagram of the frequency characteristic of the output voltage V2 as the output of the current measurement system 20. Fig. 4 shows the measured value G11 and the theoretical value G12 of the output voltage V2. The theoretical value G12 is obtained based on equation 3. Regarding the saturation point, the output voltage V2 between both ends of the shunt resistor 23 with respect to the frequency f of the alternating current I1 as the measurement target is saturated at the saturation point Q1 at the saturation frequency P1. The saturation frequency P1 is given by (R1+ R2)/(2 pi · L1). The resonance frequency P2 of the measuring coil 220 is measured by 1/{2 π. (L1. C) based on the capacitance component C of the measuring coil^1/2Giving. In a general coil or a transformer used for the purpose of transmitting an ac signal, if an output varies depending on a frequency rather than a magnetic field from the outside, the purpose cannot be achieved. In common transformers, coils, and sensors, the frequency is low, on the order of tens of HzSaturation occurs and thus the unsaturated band is very narrow. In contrast, in the current sensor 20 of the embodiment, since the frequency of the upper limit of saturation can be adjusted, it is possible to make the current sensor unsaturated at high frequencies up to several tens kHz and several hundreds kHz.

As is apparent from fig. 4, in the case where the frequency f of the alternating current I1 is lower than the saturation frequency P1, the output voltage V2 increases as the frequency f becomes higher. In detail, in the case where the frequency f of the alternating current I1 is lower than the saturation frequency P1, the correlation between the frequency of the alternating current I1 and the output voltage V2 is represented by a straight line having a positive slope. When the frequency f is higher than the saturation frequency P1, the output voltage V2 between the two ends 23a and 23b of the shunt resistor 23 is constant with respect to the frequency f of the alternating current I1. In fig. 4, when the frequency is higher than the saturation frequency P1, the capacitance component C of the measurement coil 220 is ignored in the calculation of equation 3 because the measured value G11 is greatly different from the theoretical value G12.

Fig. 5 shows the sensitivity of the current measurement system 20 of the present embodiment when the magnitude of the alternating current I1 is constant. The sensitivity is the ratio of the output voltage V2 to the alternating current I1 (V2/I1). In the present embodiment, in the current measurement system 20, the upper limit of the measurement range of the frequency f is set higher than the fundamental frequency of the alternating current I1, and the saturation frequency P1 is set to be equal to or higher than the upper limit of the measurement range of the frequency of the current measurement system 20. Therefore, as shown in fig. 5, the sensitivity (V2/I1) of the current measurement system 20 of the present embodiment depends on the frequency. In particular, the higher the frequency f, the higher the sensitivity of the current measurement system 20 of the present embodiment. More specifically, the sensitivity of the current measurement system 20 of the present embodiment with respect to the frequency f of the alternating current I1 is represented by a straight line having a positive slope. As described above, the saturation frequency P1 is given by (R1+ R2)/(2 pi · L1). That is, the saturation frequency P1 depends on the resistance value R2 of the shunt resistor 23, and the self-inductance L1 and the reactance R1 of the measurement coil 220. In the present embodiment, the self-inductance L1 and the reactance R1 of the measurement coil 220 and the resistance value R2 of the shunt resistor 23 are set so that the saturation frequency P1 is not less than the upper limit of the measurement range.

When the reactance R1 of the measurement coil 220 is small and can be ignored, the saturation frequency P1 is given by R2/(2 pi · L1), and the expression 3 can be expressed as the expression 5.

[ numerical formula 5]

In the present embodiment, the upper limit of the measurement range of the frequency f is set to be ten times or more the fundamental frequency of the alternating current I1 to be measured. The lower limit of the measurement range is greater than 0.

In the machine 30, when the state of the tool of the machine 30 is abnormal, shearing, chipping, and cracking may occur when the tool is used to machine a workpiece. In this case, the driving device 31 may be forced in the direction along the axis of rotation of the workpiece. Such a force in the direction in which the workpiece is pressed by the tool (cutter) is also referred to as a back force. In addition, a force opposite to the machining direction, i.e., the moving direction of the tool on the workpiece, is also referred to as a feed component force. In particular, in the driving device 31, a force is applied in the direction along the axis of rotation of the workpiece to the rotor of the motor for holding the tool at a predetermined position with respect to the workpiece in the direction along the axis of rotation of the workpiece. This force is applied to the driving device 31 (the rotor of the motor) while the apparatus 30 is performing a predetermined work. Such forces may affect the change in angular velocity of the rotor. The change in the angular velocity of the rotor may be reflected in the current I1 provided to the motor. In addition, when a force is applied in a direction along the axis of rotation of the workpiece and the tool is displaced from the predetermined position, the apparatus 30 executes control for returning the tool to the predetermined position. Thus, the current I1 supplied to the motor may be changed by such control.

That is, the current I1 supplied to the drive device 31 is subject to a change due to a component in a particular direction of the force applied to the drive device 31, here a component in a direction along the axis of rotation of one of the tool and the workpiece relative to the other. In particular, the ac current I1 is supplied to the drive device 31 when the apparatus 30 is executing a predetermined job. Therefore, the measuring unit 21 measures the ac current I1 supplied to the driving device 31 of the instrument 30, and outputs waveform data (current waveform data) indicating a waveform related to the ac current I1. For example, the measuring section 21 is attached to the conductor 32.

Thus, in the diagnostic system 10, it is not necessary to provide the measuring unit 21 in the vicinity of the drive device 31. The measuring section 21 may be provided inside a control panel or the like in which the power supply device 33 is housed, as long as it can measure the current supplied to the motor. This eliminates the need for a device for installing the measuring section 21 and wiring in the mechanism section of the device 30, and eliminates the need for adjustment of the balance due to the installation of the measuring section 21. Further, therefore, when the measuring portion 21 is provided, measures (for example, oil resistance measures, heat resistance measures, water resistance measures, and the like) for enabling the measuring portion 21 to be used in an environment where a workpiece is processed are not necessary. This can reduce the maintenance load on the measurement unit 21. In addition, even when the apparatus 30 is working, the waveform data can be acquired. Therefore, it is not necessary to interrupt the operation of the device 30 in order to perform diagnosis using the diagnosis system 10. This can reduce the increase in the machining cycle due to diagnosis. Further, since the waveform data can be acquired even when the device 30 is operating, the state of the tool (for example, the degree of wear of the tool) can be grasped at any time, and the tool can be used to the limit. Further, since the indeterminate state different from both the normal state and the abnormal state can be detected, it is possible to reduce the number of defects (e.g., production defective products) that may occur due to the tool being in the indeterminate state. That is, with the diagnostic system 10, as maintenance on the equipment 30, state-based maintenance (CBM) can be applied instead of the existing time-based maintenance (TBM).

The analysis unit 24 includes an acquisition unit 11 and an extraction unit 12.

The acquisition unit 11 acquires waveform data (current waveform data) indicating a waveform of the alternating current I1 supplied to the drive device 31 of the apparatus 30. More specifically, the acquisition unit 11 is connected to the measurement unit 21, and acquires waveform data from the measurement unit 21. The waveform data from the measuring section 21 is time-series data of the output voltage V2 of the measuring section 21.

The acquisition unit 11 acquires waveform data indicating a waveform of the ac current I1 supplied to the drive device 31 of the device 30, that is, time-series data of the output voltage V2.

The extraction unit 12 acquires information used by the determination unit 13 from the waveform data acquired by the acquisition unit 11. The information used in the determination section 13 is information relating to a change due to a component in a specific direction of the force applied to the driving device. The extraction unit 12 converts the waveform indicated by the waveform data acquired by the acquisition unit 11 into a frequency axis waveform. More specifically, the extraction unit 12 performs frequency analysis on the time-series data of the output voltage V2 to acquire data of harmonic components of the alternating current I1 to be measured. The extraction section 12 extracts a portion of interest, which is a portion likely to contain a change due to a component in a specific direction of the force applied to the drive device 31, from the frequency axis waveform obtained by the conversion.

In the alternating current I1 supplied to the drive device 31 of the apparatus 30, a change due to a component in a specific direction of the force applied to the drive device 31 easily occurs at a component of a frequency region higher than that of the fundamental frequency. As described above, in the current measurement system 20 of the present embodiment, the saturation frequency P1 is set to be equal to or higher than the upper limit of the measurement range including the fundamental frequency of the alternating current I1 to be measured. As shown in fig. 5, the sensitivity (V2/I1) of the current measurement system 20 of the present embodiment has frequency dependency, and the higher the frequency f, the higher the sensitivity. Therefore, the current measurement system 20 of the present embodiment can extract, with higher sensitivity, a portion of interest that may include a change due to a component in a specific direction of the force applied to the driving device 31.

Patent document 1 describes the following: a shunt resistor of several tens to several hundreds ohms is mounted when the current leakage is measured; and a shunt resistor having a low resistance value such as several ohms when used for measuring the load current. This is in consideration of the amplitude of the alternating current, and this document does not describe any sensitivity to the frequency of the alternating current.

The advantages of the current measurement system 20 according to the present embodiment will be described using a comparative example of the current measurement system 20 according to the present embodiment. Fig. 6 is a graph showing the frequency characteristics of the sensitivity of the current measurement system of the comparative example. In the current measurement system of the comparative example, unlike the current measurement system 20 of the present embodiment, the saturation frequency P1 is set to be lower than the fundamental frequency of the alternating current I1 to be measured and equal to or lower than the lower limit of the measurement range. That is, as shown in fig. 6, the sensitivity of the current measurement system 20 of the comparative example does not have frequency dependence (the magnitude of the current I1 is constant in fig. 6). That is, the sensitivity of the current measuring system of the comparative example was constant regardless of the frequency.

Fig. 7 and 9 are graphs showing frequency components of the waveform of the output voltage V2 obtained in the current measurement system 20 of the present embodiment, and fig. 8 and 10 are graphs showing frequency components of the waveform of the output voltage V2 obtained in the current measurement system of the comparative example. In addition, the scale of the frequencies in fig. 7 to 10 is merely an example. This is the same in fig. 11 to 14.

Fig. 7 and 8 show the magnitude of the frequency component of the waveform of the output voltage V2, i.e., the sensitivity, obtained in the current measurement system 20 of the present embodiment to which the ac current I1 having the same magnitude and frequencies f0, f1, and … is input, and the current measurement system of the comparative example, respectively. As described above, the sensitivity (V2/I1) of the current measurement system 20 of the present embodiment is higher as the frequency f is higher, whereas the sensitivity of the current measurement system of the comparative example is constant regardless of the frequency f. For example, as shown in fig. 7 and 8, when the alternating current I1 to be measured includes components of the fundamental frequency f0 and the harmonic frequencies f1, f2, f3, f4, f5, and …, the current measurement system 20 of the present embodiment has a larger output corresponding to the components of the harmonic frequencies f1, f2, f3, f4, f5, and … than the current measurement system of the comparative example. Therefore, according to the current measurement system 20 of the present embodiment, the components of the harmonic frequencies f1, f2, f3, f4, f5, and … can be distinguished from the noise region R10. In the current measuring system of the comparative example, the harmonic frequencies f4, f5, and … are in the noise region R10 and cannot be distinguished from the noise region R10.

Fig. 9 and 10 show the frequency component of the output voltage of the current measurement system 20 in the embodiment to which the alternating current I1 supplied to the motor of the drive device 31 is input, and the frequency component of the output voltage of the current measurement system of the comparative example, respectively. In particular, in the present embodiment, the alternating current I1 to be measured is a current supplied to the motor of the drive device 31. Therefore, the alternating current I1 to be measured may include a torque component due to the torque fluctuation and a component due to a state change such as an abnormality of the device 30, that is, a component of the above-described portion of interest. Fig. 9 shows a torque component G21 and a component G22 of a portion of interest of the current measuring system 20 in the embodiment, and fig. 10 shows a torque component G31 and a component G32 of a portion of interest of the current measuring system in the comparative example. Of the torque components G21 and G31, the output of the component of the fundamental frequency of the current I1 to be measured is the strongest, and the output becomes weaker as the frequency becomes higher. On the other hand, in the components G22 and G32 of the target portion, the output tends to be stronger at frequencies f1, f2, and … higher than the fundamental frequency f0 of the alternating current I1 as the measurement target. Therefore, according to the current measurement system 20 of the present embodiment, the output of the component of the portion of interest can be made larger than that of the current measurement system of the comparative example.

As an example, fig. 11 and 12 show waveform data (current waveform data) output from the current measurement system 20 of the present embodiment on a frequency axis. Fig. 11 shows waveform data in the case where the tool is normal (in the case where the machine 30 is normal), and fig. 12 shows waveform data in the case where the tool is broken (in the case where the machine 30 is abnormal). As can be seen from fig. 11 and 12, a change such as the distinctive portion P10 occurs in the frequency axis waveform. This change is considered to be caused by a force applied to the rotor of the motor of the drive device 31 in a direction along the axis of rotation of one of the tool and the workpiece relative to the other. Thus, the extraction section 12 extracts a portion of interest that may include a change due to the back force applied to the driving device 31 from the frequency axis waveform. In the examples of fig. 3 and 4, the extracting unit 12 may extract a region having a frequency of 1000Hz to 1200kHz from the frequency axis waveform as the portion of interest.

Fig. 13 and 14 show frequency axis waveforms obtained based on waveform data (current waveform data) output from the current measurement system of the comparative example. Fig. 13 shows waveforms in the case where the tool is normal (the case where the machine 30 is normal), and fig. 14 shows waveforms in the case where the tool is defective (the case where the machine 30 is abnormal). The changes in the frequency axis waveform in both cases are not seen from fig. 13 and 14. From this, it was found that it is difficult to determine the abnormality of the device 30 in the current measurement system of the comparative example.

The determination section 13 determines the state of the apparatus 30 from the change due to the component in the specific direction of the force applied to the drive device 31. In the present embodiment, the determination unit 13 determines the state of the device 30 based on the attention portion extracted by the extraction unit 12. The state of the device 30 includes normal, abnormal, and uncertain states that are not any of normal and abnormal. That is, the determination section 13 determines which of the normal, abnormal, and indeterminate states the state of the device 30 is.

The determination section 13 determines the state of the apparatus 30 from the portion of interest using the learned models M11, M12. The learned model M11 is designed to output an unknown value (degree of unknown) for the input (portion of interest) that is supplied. The determination section 13 supplies the attention portion obtained from the extraction section 12 to the learned model M11, thereby determining whether or not the state of the apparatus 30 is an indeterminate state based on the value (unknown value) obtained from the learned model M11. For example, if the unknown value is equal to or greater than the threshold value, the determination section 13 may determine the state of the device 30 as the indeterminate state. In addition, if the unknown value is smaller than the threshold value, the determination section 13 may determine the state of the device 30 as not being the indeterminate state. Such a learned model M11 can be generated by unsupervised learning using a part of interest in the case where the device 30 is normal or abnormal as data for learning (training samples). The learned model M12 is designed to output an abnormal value (degree of abnormality) for the input (portion of interest) that is supplied. The determination section 13 supplies the attention portion obtained from the extraction section 12 to the learned model M12, thereby determining whether the state of the apparatus 30 is normal or abnormal based on the value (abnormal value) obtained from the learned model M12. For example, if the abnormal value is equal to or greater than the threshold value, the determination unit 13 may determine that the state of the device 30 is abnormal. In addition, if the abnormal value is smaller than the threshold value, the determination section 13 may determine the state of the device 30 as normal. Such a learned model M12 can be generated by unsupervised learning using data (a data set) for learning for specifying the relationship between a label corresponding to an abnormal value and a part of interest. The learned models M11, M12 are stored in the storage unit 17. The storage unit 17 may store a set of learned models M11 and M12 for each tool type. That is, the storage unit 17 may store a plurality of sets of learned models M11 and M12 corresponding to a plurality of types of tools, respectively.

The output unit 14 outputs the result of the determination by the determination unit 13. The output unit 14 includes, for example, an audio output device and a display. The display is a thin display device such as a liquid crystal display or an organic EL display. The output unit 14 may display the result of the determination by the determination unit 13 on a display or notify it through an audio output device. The output unit 14 may transmit the result of the determination by the determination unit 13 to an external device in the form of data or may accumulate the result. Further, the output unit 14 does not need to have both a sound output device and a display. The output unit 14 may also output the result of the determination by the determination unit 13 by e-mail or the like.

The collection unit 15 collects and accumulates the data acquired by the acquisition unit 11. In the present embodiment, the data acquired by the acquisition unit 11 includes waveform data from the measurement unit 21. The data collected by the collection unit 15 is used for generation and update of the learned models M11 and M12.

The generator 16 generates the learned models M11 and M12 to be used by the determination unit 13. The generation unit 16 generates the learned models M11 and M12 by a machine learning algorithm using a predetermined amount or more of data for learning. The data for learning may be prepared in advance, or may be generated from data accumulated in the collecting unit 15. By using the learning data generated from the data accumulated in the collection unit 15, it is possible to expect further improvement in the accuracy of the state determination using the learned models M11 and M12. In particular, even when it is determined that the state is indeterminate, if it can be determined as normal or abnormal, additional learning is performed for the indeterminate state that can be regarded as normal or abnormal, thereby improving the accuracy of determining whether normal or abnormal. The generator 16 evaluates the newly generated learned models M11, M12, and when the evaluation results of the learned models M11, M12 increase, the learned models M11, M12 stored in the storage 17 are replaced with the newly generated learned models M11, M12, and the learned models M11, M12 are updated. As described above, as a method of generating the learned models M11 and M12, unsupervised learning and supervised learning can be appropriately used according to the contents of the state. Further, as the unsupervised learning, a dimensional compression technique such as a representative principal component analysis, a self-organizing map, and a self-encoder can be used. In addition, as the supervised learning, a representative multilayer neural network having a supervised learning mechanism can be used.

In the diagnostic system 10, the acquisition unit 11, the extraction unit 12, the determination unit 13, the output unit 14, the collection unit 15, and the generation unit 16 can be realized by a computer system including one or more processors (e.g., microprocessors) and one or more memories, for example. That is, the one or more processors function as the acquisition unit 11, the extraction unit 12, the determination unit 13, the output unit 14, the collection unit 15, and the generation unit 16 by executing one or more programs stored in one or more memories. The one or more programs may be recorded in advance in the memory, may be provided via an electric communication line such as the internet, or may be provided by being recorded in a non-transitory recording medium such as a memory card.

(1.3) operation

The basic operation of the diagnostic system 10 is briefly described next. Fig. 15 is a flowchart of the operation of the diagnostic system 10.

The acquisition unit 11 acquires waveform data (current waveform data) indicating a waveform of the ac current I1 supplied to the motor of the drive device 31 of the instrument 30 from the measurement unit 21 (step S11). Next, the extraction unit 12 converts the waveform indicated by the waveform data acquired by the acquisition unit 11 into a frequency axis waveform, and extracts a portion including a change due to a component in a specific direction of the force applied to the drive device 31 from the frequency axis waveform (step S12). After that, the determination unit 13 determines the state of the device 30 from the parts extracted by the extraction unit 12 using the plurality of learned models M11, M12 (step S13). Finally, the output unit 14 outputs the determination result of the determination unit 13 (step S14). In this way, the diagnostic system 10 can diagnose the mechanism portion driven by the drive device 31 based on the waveform data indicating the waveform of the alternating current I1 supplied to the drive device 31 and present the result.

(2) Modification example

The embodiments of the present disclosure are not limited to the above embodiments. The above embodiment may be modified in various ways according to design and the like as long as the object of the present disclosure can be achieved. Modifications of the above embodiment will be described below.

In one modification, the upper limit value of the frequency measurement range of the current measurement system 20 is higher than the fundamental frequency f0 of the alternating current I1 to be measured. In particular, the measurement range is set to include frequency components, particularly harmonic components, which contribute to the determination by the determination unit 13 of the state of the device 30. The upper limit of the measurement range is at least twice the fundamental frequency of the ac current I1. The upper limit value may be five times or more, or ten times or more, the fundamental frequency of the alternating current I1 to be measured. The lower limit of the measurement range is not particularly limited, but is higher than 0. As described above, since the frequency component contributing to the determination by the determination unit 13 to determine the state of the device 30 is a harmonic component, the lower limit value may be the fundamental frequency of the alternating current I1 to be measured or may be higher than the fundamental frequency. In short, the measurement range of the frequency of the current measurement system 20 does not necessarily include the fundamental frequency of the alternating current I1 to be measured.

In the measurement unit 21, the measurement coil 220 does not need to be formed of a single coil, and may be formed of one or more coils. The shunt resistor 23 does not need to be a single resistor, and may be one or more resistors. In the above embodiment, the output voltage V2 between the two ends of the shunt resistor 23 is used as the output of the measuring section 21, but the measuring section 21 may be provided with a circuit element such as an amplifier that amplifies the output voltage V2.

The current measurement system 20 does not need to include the analysis unit 24. The measuring section 21 does not need to include the core 221. The current sensor 22 does not need to be a current transformer, and may have a function of measuring a current using a measurement coil magnetically coupled to a conductor through which an alternating current I1 to be measured flows. That is, as the current sensor 22, a known type of current sensor other than a current transformer can be used.

The determination section 13 determines the state of the device 30 as any one of a normal state, an abnormal state, and an indeterminate state, but is not limited thereto. The determination unit 13 can determine the degree of the normal, abnormal, and indeterminate states. Thus, the diagnostic system 10 can make different notifications depending on the degree of normal, abnormal, and indeterminate states. For example, the diagnostic system 10 may notify that there is a high possibility of being in an abnormal or indeterminate state in a case where the degree of normality is low. In addition, the diagnostic system 10 may perform processing such as stopping and notifying the operation of the device 30 when the degree of the abnormal and indeterminate states exceeds the threshold value. Alternatively, the states of the device 30 are not limited to three, i.e., normal, abnormal, and indeterminate states, and may be four or more, or two.

The diagnostic system 10 does not need to include the collection unit 15, the generation unit 16, and the storage unit 17. That is, the diagnostic system 10 may not have a function of updating the learned models M11, M12, … by itself. Further, the storage unit 17 does not need to store the plurality of learned models M11, M12, ….

The diagnostic system 10 may not include the extraction unit 12. For example, in a case where the user or another device performs the processing in the extraction section 12 instead, the diagnostic system 10 may not extract a portion including a change due to a component in a specific direction of the force applied to the drive device 31. The entire waveform represented by the waveform data acquired by the acquisition unit 11 may be input, and the state of the device 30 may be obtained and output from the learned models M11 and M12. That is, the extraction of the portion containing the change may be omitted.

In addition, the diagnostic system 10 need not have an output 14. For example, the diagnostic system 10 may be configured to output the state of the device 30 determined by the determination unit 13 to the outside of the diagnostic system 10.

The diagnostic system 10 may be configured by a plurality of computers, and the functions of the diagnostic system 10 (particularly, the acquisition unit 11, the extraction unit 12, the determination unit 13, the output unit 14, the collection unit 15, and the generation unit 16) may be distributed among a plurality of devices. For example, the acquisition unit 11, the extraction unit 12, the determination unit 13, and the output unit 14 may be provided in a personal computer or the like provided in a facility having a device, and the generation unit 16 and the output unit 14 may be provided in an external server or the like. In this case, the diagnostic system 10 is realized by cooperation of a personal computer and a server. Also, at least a part of the functions of the diagnostic system 10 may be realized by cloud (cloud computing), for example.

The main body of execution of the diagnostic system 10 described above includes a computer system. The computer system has a processor and a memory as hardware. The function as the execution subject of the diagnostic system 10 in the present disclosure is realized by executing a program recorded in a memory by a processor of a computer system. The program may be recorded in advance in a memory of the computer system or may be provided through an electric communication line. The program may be provided by being recorded on a non-transitory recording medium such as a memory card, an optical disk, or a hard disk drive that can be read by the computer system. A processor of a computer system is constituted by one or more electronic circuits including a semiconductor Integrated Circuit (IC) or a large scale integrated circuit (LSI). Here, the term "IC" or "LSI" is used, but the term may be changed depending on the degree of integration, and may be referred to as system LSI, VLSI (very large scale integration), or ULSI (ultra large scale integration). A field programmable gate array (FGPA) that is programmed after LSI manufacturing is completed, or a reconfigurable logic device that can reconfigure a bonding relationship inside LSI or can set circuit division inside LSI can also be used for the same purpose. The plurality of electronic circuits may be integrated in one chip or may be distributed over a plurality of chips. The plurality of chips may be integrated in one device or may be distributed among a plurality of devices.

In the above embodiment, the apparatus 30 is a lathe, but is not limited thereto. The device 30 may also be a pump, for example. Specifically, the device 30 may be a vacuum pump. Vacuum pumps are used in various fields such as the manufacture of semiconductor devices. In this case, the diagnostic system 10 may determine the state of the impeller or the deterioration of the bearing of the impeller as the state of the apparatus 30. Further, the apparatus 30 may be a component mounting machine. Specifically, the apparatus 30 may be a robot (robot arm) for performing mounting (assembly) of components. In this case, the diagnostic system 10 may determine the mounting state of the component as the state of the apparatus 30. Additionally, the apparatus 30 may be a grinding device. Specifically, the apparatus 30 may be a polishing device for performing chemical mechanical polishing. In this case, the diagnostic system 10 may determine the states of the polishing pad and the dresser as the states of the apparatus 30.

(3) Means for

As is apparent from the above embodiment and modifications, the present disclosure includes the following aspects. The following reference numerals in parentheses are merely provided to clarify the correspondence with the embodiments.

A first aspect is a current measurement system (20) including: a current sensor (22) having a measurement coil (220) magnetically coupled to a conductor (32) through which an alternating current (I1) to be measured flows; and a shunt resistor (23) electrically connected between both ends (220a, 220b) of the measurement coil (220). The current measurement system (20) has a saturation point at which an output voltage (V2) between both ends of the shunt resistor (23) with respect to the frequency of the alternating current (I1) to be measured is saturated. The upper limit of the frequency measurement range is larger than the fundamental frequency of the alternating current (I1) to be measured. The saturation frequency at the saturation point is equal to or higher than the upper limit value. According to the first aspect, the sensitivity to frequency components higher than the fundamental frequency of the alternating current (I1) can be improved.

The second mode is a current measurement system (20) based on the first mode. In the second aspect, the correlation between the frequency of the alternating current (I1) to be measured and the output voltage (V2) is represented by a straight line having a positive slope in the measurement range. According to the second aspect, the sensitivity to frequency components higher than the fundamental frequency of the alternating current (I1) can be improved.

The third mode is a current measurement system (20) based on the first or second mode. In the third aspect, the output voltage V2 is expressed by equation 3 based on the output voltage V2, the alternating current I1 to be measured, the coupling coefficient k between the conductor (32) and the measurement coil (220), the frequency f of the alternating current I1 to be measured, the self-inductance L1 of the measurement coil (220), the reactance R1 of the measurement coil (220), the resistance value R2 of the shunt resistor (23), and the number of turns N of the measurement coil (220).

[ numerical formula 3]

According to the third aspect, the sensitivity to a frequency component higher than the fundamental frequency of the alternating current (I1) can be improved.

A fourth aspect is a current measurement system (20) according to any one of the first to third aspects. In a fourth aspect, the magnitudes of the self-inductance and the reactance of the measurement coil (220) and the resistance value of the shunt resistor (23) are such that the saturation frequency is equal to or higher than the upper limit of the measurement range. According to the fourth aspect, the sensitivity to a frequency component higher than the fundamental frequency of the alternating current (I1) can be improved.

A fifth aspect is a current measurement system (20) according to any one of the first to fourth aspects. In a fifth aspect, the upper limit value of the measurement range is at least ten times the fundamental frequency of the alternating current (I1) to be measured. According to the fifth aspect, the sensitivity to a frequency component higher than the fundamental frequency of the alternating current (I1) can be improved.

A sixth aspect is a current measurement system (20) according to any one of the first to fifth aspects. In a sixth mode, the current sensor (22) further includes a core (221) at least a part of which passes through the inside of the measurement coil (220). According to the sixth aspect, the sensitivity to a frequency component higher than the fundamental frequency of the alternating current (I1) can be improved.

A seventh aspect is a current measurement system (20) according to any one of the first to sixth aspects. In a seventh aspect, the current measurement system (20) further includes an analysis unit (24), and the analysis unit (24) performs frequency analysis on the time-series data of the output voltage (V2) to acquire data of a harmonic component of the alternating current (I1) to be measured. According to the seventh aspect, the sensitivity to a frequency component higher than the fundamental frequency of the alternating current (I1) can be improved.

An eighth aspect is a diagnostic system (100) provided with a current measurement system (20) and a determination unit (13). The current measurement system (20) is a current measurement system according to any one of the first to seventh aspects, in which a current (I1) supplied to a drive device (31) of a device (30) is measured as the alternating current to be measured. The determination unit (13) determines the state of the device (30) based on the output of the current measurement system (20). According to the eighth aspect, the sensitivity to a frequency component higher than the fundamental frequency of the alternating current (I1) can be improved.

Description of the reference numerals

10: a diagnostic system; 13: a determination unit; 20: a current measuring system; 22: a current sensor; 220: a measuring coil; 221: a core; 23: a shunt resistor; 24: an analysis unit; 30: equipment; 31: a drive device; 32: a conductor; i1: an alternating current; v2: and outputting the voltage.