Measuring device, measuring method, and program

Abstract

To calculate the direct current resistance of an object to be measured through simple processing.SOLUTION: A measuring device 1 acquires measurement data indicating the frequency characteristics of an AC impedance obtained on the basis of a response signal generated in an object to be measured 9 in a state where a signal having an AC component is supplied to the object to be measured 9, and from the acquired measurement data, extracts at least the frequency characteristics of the AC impedance lower than the peak frequency Fp of the AC impedance in which a tangent is parallel to an axis representing a real part, in an arc R of the lowest frequency region FRmin in the Nyquist diagram. The measuring device 1 calculates a circle Ca proximate to the shape (Rr) of the frequency characteristics of the AC impedance extracted in the Nyquist diagram, and in the calculated circle Ca, estimates the value of a real part of an AC impedance X in which the value of an imaginary part is zero, of the AC impedance having a lower frequency than the peak frequency Fp, as the direct current resistance of the object to be measured.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a measuring device, a measuring method, and a program.

Background Art

[0002] Patent Document 1 discloses a DC resistance evaluation device that calculates the internal DC resistance value of a battery under measurement based on the measurement result of impedance measurement means and a selected equivalent circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described DC resistance evaluation device, in order to calculate the DC resistance of the measurement target, it is necessary to select an equivalent circuit and perform an equivalent circuit analysis for calculating the circuit constants optimal as the equivalent circuit using impedance data. For this reason, there has been a problem that the load required for the analysis process becomes large.

[0005] The present invention has been made paying attention to such problems, and an object thereof is to calculate the DC resistance of a measurement target by simple processing.

Means for Solving the Problems

[0006] According to an aspect of the present invention, a measuring device includes an acquisition unit that acquires measurement data indicating frequency characteristics of an AC impedance obtained based on a response signal generated in a measurement target while supplying a signal having an AC component to the measurement target. Further, the measuring device includes an extraction unit that extracts at least frequency characteristics of the AC impedance lower than a vertex frequency of the AC impedance whose tangent is parallel to an axis representing a real part among arcs in the lowest frequency region in a Nyquist diagram from the measurement data, and a calculation unit that calculates a circle approximating the shape of the frequency characteristics of the AC impedance extracted by the extraction unit in the Nyquist diagram. And the measuring device includes a resistance estimation unit that estimates, as a DC resistance of the measurement target, a value of a real part of the AC impedance whose imaginary part value is zero among the AC impedances having a frequency lower than the vertex frequency in the circle calculated by the calculation unit.

Advantages of the Invention

[0007] According to this aspect, a process of approximating the shape of the frequency characteristics of the AC impedance at a frequency lower than the vertex frequency in the Nyquist diagram to a circular shape and estimating, as the DC resistance of the measurement target, the value of the real part where the imaginary part on the approximated circle becomes zero is executed. Therefore, it is possible to reduce the processing load required for calculating the DC resistance compared to the process of performing equivalent circuit analysis and calculating the DC resistance.

[0008] Thus, according to the above aspect, the DC resistance of the measurement target can be calculated by a simple process.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

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Figure 8

[0010] Hereinafter, each embodiment of the present invention will be described with reference to the accompanying drawings. In this specification, the same or equivalent elements are denoted by the same reference numerals throughout.

[0011] (First Embodiment) FIG. 1 is a diagram showing the configuration of a measurement system 100 including a resistance measurement device 1 according to the first embodiment.

[0012] The measurement system 100 is a system for measuring the DC resistance of a measurement target 9. The measurement system 100 according to the first embodiment measures the AC impedance of the measurement target 9 in a state where the measurement target 9 is compressed with a predetermined pressure, and calculates the DC resistance of the measurement target 9.

[0013] The measurement target 9 is an object including a resistance component and a capacitance component. For example, a liquid, a mixed liquid in which an insoluble solid substance is mixed with the liquid, and a powder can be mentioned as the measurement target 9. Examples of the liquid or the mixed liquid include a slurry used in the production of a positive electrode material or a negative electrode material of a battery. Examples of the powder include a powder used in the production of an all-solid-state battery.

[0014] The measurement object 9 of the first embodiment is a solid electrolyte used in the manufacture of all-solid-state batteries. The measurement system 100 of the first embodiment for measuring the electrical characteristics of the solid electrolyte includes a resistance measuring device 1, an AC measuring device 2, and a compression device 3.

[0015] The compression device 3 is used to enable the measurement of the electrical characteristics of the measurement object 9 in a state where the forming pressure for forming the powder of the measurement object 9 acts on it for use as a product. The compression device 3 compresses the measurement object 9 with a predetermined pressure. For example, a pressure of several tens [kN] is applied to the measurement object 9. Depending on the measurement object 9, the predetermined pressure may be several tens or several hundreds [N].

[0016] The compression device 3 of the first embodiment includes a pair of electrode portions 31a and 31b that sandwich the measurement object 9, and a pressurizing portion 32 that applies a high-load pressurizing force for compressing the measurement object 9 to the pair of electrode portions 31a and 31b.

[0017] The measurement object 9 is placed between the pair of electrode portions 31a and 31b by the measurer, and a pressure is applied vertically from the electrode portion 31b toward the electrode portion 31a by the pressurizing portion 32. As a specific example, the measurement object 9 is accommodated in a housing hole of a die (not shown), and the pair of electrode portions 31a and 31b are inserted into the die and sandwiched between them, and the die, the pair of electrode portions 31a and 31b, and the measurement object 9 are placed on the compression device 3 as a unit.

[0018] In addition, a voltage application cable of the AC measuring device 2 is connected to the pair of electrode portions 31a and 31b, and a current detection cable of the AC measuring device 2 is connected to the electrode portion 31b.

[0019] The AC measuring device 2 supplies an electrical signal having an AC component to the measurement object 9 and detects a response signal generated in the measurement object 9 in this state. The shape of the electrical signal supplied to the measurement object 9 may be a waveform such as a sine wave, a rectangular wave, or a sawtooth wave. Also, the electrical signal may be a signal in which an AC component is superimposed on a DC component.

[0020] The AC measuring device 2 calculates a measured value of the AC impedance, which is a complex number impedance, using the supplied value of the electrical signal and the detected value of the response signal. The AC measuring device 2 measures the AC impedance for each frequency by detecting the response signal generated in the measurement target 9 while sweeping the frequency of the electrical signal supplied to the measurement target 9 within a predetermined frequency range.

[0021] The AC measuring device 2 of the first embodiment includes a constant voltage supply circuit that supplies an AC voltage V, which is controlled so that the sine wave voltage value is constant, as a signal having an AC component, to the measurement target 9, and a current detection circuit that detects the magnitude of the AC response current I flowing through the measurement target 9. Further, the AC measuring device 2 includes a control circuit that sweeps the frequency of the AC voltage V supplied from the constant voltage supply circuit.

[0022] The frequency sweep range is set, for example, from several [Hz] to several [MHz], and the amplitude of the AC voltage V is set, for example, from several [mV] to several hundred [mV]. The AC measuring device 2 outputs a group of measured values of the AC impedance at each measured frequency as measurement data indicating the frequency characteristics of the AC impedance to the resistance measuring device 1.

[0023] The resistance measuring device 1 constitutes a measuring device that measures the DC resistance of the measurement target 9 based on the measurement data indicating the frequency characteristics of the AC impedance of the measurement target 9. For example, the resistance measuring device 1 plots the measurement data on a complex plane to create a complex plane impedance diagram in order to measure the DC resistance. In the first embodiment, as an example of the complex plane impedance diagram, a Nyquist diagram with the real part and the imaginary part of the AC impedance as the real axis and the imaginary axis, respectively, is adopted.

[0024] The resistance measuring device 1 is realized, for example, by a computer including one or a plurality of processors and a recording medium. The resistance measuring device 1 of the first embodiment includes a storage unit 10, a processing unit 20, an operation unit 30, and a display unit 40.

[0025] The memory unit 10 stores the measurement data by the AC measuring device 2 and the calculation results by the processing unit 20. Further, the memory unit 10 constitutes a computer-readable recording medium on which a program for controlling the operation of the processing unit 20 is recorded. The memory unit 10 is realized by a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory), for example.

[0026] The processing unit 20 executes a resistance measurement process for measuring the DC resistance of the measurement target 9 based on the measurement data output from the AC measuring device 2. The processing unit 20 is realized by a processor such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or a DSP (digital signal processor), for example.

[0027] The operation unit 30 is composed of a plurality of push buttons provided around the display screen, a touch sensor arranged within the screen of the display unit 40, or a keyboard and a mouse, etc. The operation unit 30 receives the input operation of the user and generates an operation signal indicating the content of the received input operation.

[0028] Examples of the input operation include an operation of pressing a power button, an operation of setting measurement conditions and display conditions, and an operation of instructing the start or end of the measurement process, etc. The operation unit 30 outputs the generated operation signal to the processing unit 20.

[0029] The display unit 40 displays the measurement result indicating the DC resistance of the measurement target 9, the measurement conditions, etc. The display unit 40 is constituted by a touch panel so that the user can visually recognize information and operate it, for example. Instead of this, the display unit 40 may be realized by a liquid crystal display or an LED display, etc. The display unit 40 functions as an output means for outputting the calculation result by the processing unit 20.

[0030] As described above, the measurement system 100 according to the first embodiment can measure the electrical characteristics of the powder of the measurement object 9 with a high molding pressure as a product in a state that conforms to the actual product state.

[0031] In the first embodiment, an example in which powder is used as the measurement object 9 has been described. However, the measurement object 9 is not limited to this, and may be a liquid or a mixture that can be measured by the AC measuring device 2 and does not require the compression device 3. Further, in the first embodiment, the resistance measuring device 1 and the AC measuring device 2 are configured separately, but the AC measuring device 2 may be provided in the resistance measuring device 1.

[0032] Subsequently, the detailed configuration of the processing unit 20 will be described with reference to FIG. 2.

[0033] FIG. 2 is a block diagram showing the functional configuration of the processing unit 20 of the resistance measuring device 1 according to the first embodiment.

[0034] The processing unit 20 includes a measurement data acquisition unit 21, an arc data extraction unit 22, and a complex plane processing unit 23.

[0035] The measurement data acquisition unit 21 functions as acquisition means for acquiring measurement data from the AC measuring device 2. The acquired measurement data is data indicating the frequency characteristics of the AC impedance obtained based on the response signal generated in the measurement object 9 in a state where a signal having an AC component is supplied to the measurement object 9 as described above.

[0036] The measurement data acquisition unit 21 of the first embodiment may acquire measurement data from the AC measuring device 2, or may acquire the measurement data recorded in the storage unit 10 by reading it out. The measurement data acquisition unit 21 outputs the acquired measurement data to the arc data extraction unit 22.

[0037] The arc data extraction unit 22 functions as an extraction means for extracting arc data to be subjected to circle fitting from the measurement data. The extracted arc data is data indicating the frequency characteristics of the AC impedance at a frequency lower than the peak frequency of the arc having the lowest frequency region among one or a plurality of arcs in the Nyquist diagram. The peak frequency of the arc in the lowest frequency region in the Nyquist diagram is the frequency of the AC impedance at which the tangent becomes parallel to the real axis representing the real part among a group of AC impedances forming the arc.

[0038] Note that the above-mentioned arc in the lowest frequency region corresponds to the arc when there is only one arc drawn in the Nyquist diagram from the measurement data, and when there are a plurality of arcs, it corresponds to the arc drawn by a group of AC impedances having the lowest frequency region.

[0039] The arc data extraction unit 22 extracts arc data from the measurement data according to the input operation of the measurer with respect to the operation unit 30 shown in FIG. 1. For example, the measurer visually observes the Nyquist diagram displayed on the display unit 40 and designates at least the low-frequency side of the arc in the lowest frequency region in the Nyquist diagram by the operation unit 30.

[0040] Then, in the operation unit 30, an operation signal indicating the part of the arc designated by the measurer is generated, and the arc data extraction unit 22 outputs a group of AC impedances corresponding to the part of the arc indicated by the operation signal to the complex plane processing unit 23 as arc data.

[0041] Note that when the slope of the tangent of the AC impedance at the lowest frequency in the arc in the lowest frequency region is positive (plus), the arc data extraction unit 22 may determine that the arc does not extend to the lower frequency side than the peak frequency and end the measurement of the DC resistance of the measurement target 9.

[0042] The complex plane processing unit 23 performs circle fitting to approximate the arc drawn on the Nyquist diagram based on the arc data output from the arc data extraction unit 22, and identifies the intersection point between the approximated circle obtained by the circle fitting and the real axis of the Nyquist diagram. The complex plane processing unit 23 of the first embodiment includes a circle fitting calculation unit 23A and a DC resistance estimation unit 23B.

[0043] The circle fitting calculation unit 23A functions as a calculation means for calculating a circle that approximates the shape of the frequency characteristics of the AC impedance extracted by the arc data extraction unit 22 in the Nyquist diagram.

[0044] In the first embodiment, the circle fitting calculation unit 23A performs circle fitting on the arc drawn on the Nyquist diagram based on the arc data. The circle fitting calculation unit 23A sequentially changes the center position and radius of the circle on the Nyquist diagram so that the difference between the arc data and the circle on the Nyquist diagram is minimized by using calculation processing such as the least squares method as a general circle fitting process.

[0045] Then, the circle fitting calculation unit 23A acquires the circle with the smallest difference between the arc on the Nyquist diagram and the approximate circle, and outputs approximate data indicating the acquired circle to the DC resistance estimation unit 23B. This approximate data shows, for example, a group of numerical values forming the circle, or the center position and radius of the circle.

[0046] The DC resistance estimation unit 23B functions as a resistance estimation means for estimating the DC resistance of the measurement target 9.

[0047] In the first embodiment, the DC resistance estimation unit 23B extracts a group of AC impedances having a frequency lower than the vertex frequency of the above-described arc data from among the group of AC impedances forming the circle calculated by the circle fitting calculation unit 23A based on the approximate data.

[0048] Then, the DC resistance estimation unit 23B identifies the real part value of the AC impedance whose imaginary part value is zero among the group of extracted AC impedances, and calculates the identified real part value as the DCR (Direct Current Resistance) of the measurement target 9.

[0049] The DCR is the DC resistance of the entire bulk portion of the measurement target 9, excluding the resistance components of the pair of electrode portions 31a and 31b. The DC resistance estimation unit 23B outputs the calculated DCR of the measurement target 9 to the storage unit 10.

[0050] In this way, the DC resistance estimation unit 23B estimates, as the DC resistance of the measurement target 9, the real part value of the AC impedance whose imaginary part value is zero among the group of AC impedances having a frequency lower than the vertex frequency of the arc drawn by the measurement data in the circle calculated by the circular fitting calculation unit 23A.

[0051] Also, the DC resistance estimation unit 23B outputs the calculated DCR of the measurement target 9 to the display unit 40. Thereby, the display unit 40 displays the DCR of the measurement target 9 on the screen as a measurement result.

[0052] Next, a method for estimating the DC resistance of the measurement target 9 by the processing unit 20 of the first embodiment will be briefly described with reference to FIG. 3.

[0053] FIG. 3 is a diagram for explaining an example of a method for estimating the DCR of the measurement target 9 using circular fitting.

[0054] FIG. 3 shows a Nyquist diagram with the real axis representing the real part of the AC impedance as the horizontal axis and the imaginary axis representing the imaginary part as the vertical axis, and a Cole-Cole plot diagram in which the sign of the imaginary axis is inverted.

[0055] In the Cole-Cole plot, an arc R drawn by the measurement data acquired by the measurement data acquisition unit 21 is indicated by a dashed line. In the arc R, as the value of the real part becomes smaller, the frequency of the AC impedance becomes larger. In this example, there is one arc R, and the arc R corresponds to the arc in the lowest frequency region FRmin.

[0056] Also, among a group of AC impedances included in the measurement data, the frequency of the AC impedance P whose tangent is parallel to the real axis is shown as the peak frequency Fp. In other words, the AC impedance P is the AC impedance in which the perpendicular line is orthogonal to the real axis among the measurement data in the Cole-Cole plot. Also, the frequency of the AC impedance A is the upper limit of the arc data to be subjected to circle fitting, and in this example, it is a frequency lower than the peak frequency Fp.

[0057] And the frequency of the AC impedance B is the lower limit of the arc data, and in this example, it is the frequency of the AC impedance in which the absolute value of the imaginary part is minimized among a group of AC impedances having a frequency lower than the frequency of the AC impedance A. Also, the approximate circle Ca obtained by circle fitting is indicated by a solid line.

[0058] As shown in FIG. 3, first, the measurement data acquired by the measurement data acquisition unit 21 is displayed on the display unit 40 as an arc R in the Cole-Cole plot. Then, in order to ensure the estimation accuracy of the DCR, the measurer designates a group of AC impedances on the low-frequency side of the arc R as the target of circle fitting.

[0059] Specifically, the measurer designates, on the operation unit 30, the frequency range from the upper limit frequency of the AC impedance A to the lower limit frequency of the AC impedance B among a group of AC impedances having a frequency lower than the peak frequency Fp of the AC impedance P from among the displayed measurement data.

[0060] As the number of plots of the AC impedance to be circularly fitted, at least about 3 are desirable. Therefore, it is desirable that the frequency range be determined so as to include the AC impedances at at least 3 frequencies as a group of AC impedances lower than the vertex frequency Fp of the AC impedance P.

[0061] When the frequency range is specified by the operation unit 30, the arc data extraction unit 22 extracts arc data indicating a group of AC impedances in the frequency range specified by the operation unit 30 from the measurement data. Then, in the circular fitting calculation unit 23A, circular fitting is performed on the shape of the arc Rr for circular fitting drawn by the extracted arc data, and as a result, the approximate circle Ca is calculated.

[0062] Subsequently, in the DC resistance estimation unit 23B, the real part value of the AC impedance X corresponding to the intersection of the approximate circle Ca and the real axis is calculated as the DCR of the measurement target 9. That is, in the approximate circle Ca calculated by the circular fitting calculation unit 23A, the real part value of the AC impedance X whose imaginary part value is zero among the AC impedances having a frequency lower than the vertex frequency Fp of the AC impedance P is estimated as the DC resistance of the measurement target 9.

[0063] In the verification test, for the measurement target 9 whose actual DC resistance value is 81.0 [Ω], as a result of executing the estimation process of the first embodiment, the estimated value of the DC resistance of the measurement target 9 was about 81.2 [Ω], and the estimation error was about 0.3%. Therefore, the inventors have learned that this estimation process has an estimation accuracy comparable to the DC resistance value obtained by equivalent circuit analysis.

[0064] Thus, the inventors have found that for the measurement target 9 having an electrical characteristic in which the arc R in the lowest frequency region FRmin extends to the lower frequency side than the vertex frequency Fp, by performing circular fitting using the group of AC impedances of the arc R, the real part value of the intersection (X) of the approximate circle Ca and the real axis can be regarded as the DCR of the measurement target 9.

[0065] In particular, the inventors have found that the estimation accuracy tends to improve by subjecting a group (Rr) of AC impedances on the lower frequency side than the apex frequency Fp of the arc R to circular fitting. Therefore, as described above, the processing unit 20 of the first embodiment estimates the real part value of the intersection point (X) between the circle Ca obtained by circular approximation of the arc Rr on the lower frequency side than the apex frequency Fp and the real axis as the DC resistance of the measurement target 9.

[0066] Next, a measurement method of the measurement system 100 according to the first embodiment will be described with reference to FIGS. 4 to 6.

[0067] FIG. 4 is a flowchart showing an example of a processing procedure of a measurement method for measuring the DC resistance of the measurement target 9.

[0068] In step S1, the compression device 3 compresses the measurement target 9 at a predetermined pressure according to the actual product state.

[0069] In step S2, the AC measuring device 2 executes an AC impedance measurement process for measuring the AC impedance of the measurement target 9 in a state where the measurement target 9 is compressed by the compression device 3. Details of this process will be described later with reference to FIG. 5.

[0070] In step S3, the resistance measuring device 1 executes a DCR estimation process for estimating the DCR of the measurement target 9 based on the measurement data indicating the frequency characteristics of the AC impedance measured by the AC measuring device 2. Details of this process will be described later with reference to FIG. 6.

[0071] When the process of step S3 is completed, a series of processing procedures for the measurement method of the first embodiment ends.

[0072] Subsequently, FIG. 5 is a flowchart showing an example of a processing procedure of the AC impedance measurement process executed in step S2.

[0073] In step S21, as shown in FIG. 1, the AC measuring device 2 applies an alternating voltage V whose voltage value is controlled to be constant to the measurement target 9 in the state where the measurement target 9 is compressed in step S1. For example, the effective value of the applied alternating voltage is set to several hundred [mV], and the frequency of the alternating voltage is set to several [MHz].

[0074] In step S22, the AC measuring device 2 detects an alternating response current I flowing through the measurement target 9 in the state where the alternating voltage V is applied to the measurement target 9 in step S21. Then, the AC measuring device 2 measures an AC impedance represented by a complex number based on the current value of the detected response current I and the voltage value of the applied alternating voltage V.

[0075] In step S23, the AC measuring device 2 calculates a measured value of the AC impedance for each swept frequency while sweeping the frequency of the alternating voltage V within a predetermined frequency range. For example, the predetermined frequency range is set to a frequency range from several [Hz] to several [MHz].

[0076] In step S24, the AC measuring device 2 outputs a group of calculated measured values of the AC impedance as measurement data indicating the frequency characteristics of the AC impedance.

[0077] Then, when the process of step S24 is completed, the AC impedance measurement process of step S2 ends, and the process returns to the processing procedure of the measurement method shown in FIG. 4 and proceeds to the DCR estimation process of step S3.

[0078] FIG. 6 is a flowchart showing an example of the processing procedure of the DCR estimation process executed in step S3.

[0079] In step S31, the resistance measuring device 1 acquires the measurement data generated in step S2.

[0080] Therefore, step S31 corresponds to an acquisition step of acquiring measurement data indicating the frequency characteristics of the AC impedance obtained based on the response signal generated in the measurement target 9 in a state where a signal having an AC component is supplied to the measurement target 9.

[0081] In step S32, as shown in FIG. 3, the resistance measuring device 1 extracts a group of AC impedances having a frequency lower than the apex frequency Fp of the AC impedance P that is the apex of the arc R having the lowest frequency region in the Nyquist diagram in which the measurement data is plotted. The AC impedance P is the AC impedance in which the tangent is parallel to the real axis on the arc R in the Nyquist diagram among the measurement data.

[0082] Therefore, step S32 corresponds to an extraction step of extracting at least the frequency characteristics (Rr) of the AC impedance that is lower than the apex frequency Fp of the AC impedance P where the tangent is parallel to the axis representing the real part among the arcs R in the lowest frequency region FRmin in the Nyquist diagram from the measurement data.

[0083] In step S33, the resistance measuring device 1 performs a circular fitting that approximates a circle to the arc Rr that is the shape of the frequency characteristics of the AC impedance extracted in step S32 in the Nyquist diagram. An approximate circle Ca is obtained by the circular fitting.

[0084] Therefore, step S33 corresponds to a calculation step of calculating a circle Ca that approximates the shape (Rr) of the frequency characteristics of the AC impedance extracted in step S32 in the Nyquist diagram.

[0085] In step S34, the resistance measuring device 1 obtains the value of the real part of the AC impedance X whose imaginary part value is zero among the group of AC impedances having a frequency lower than the apex frequency Fp of the AC impedance P that is the apex of the arc in the circle approximated in step S33.

[0086] In step S35, the resistance measuring device 1 outputs the real part value of the AC impedance X obtained in step S34 as an estimated value of the DCR of the measurement target 9. For example, the resistance measuring device 1 outputs the estimated value of the DCR of the measurement target 9 to the storage unit 10 or the display unit 40. Thereby, the estimated value of the DCR of the measurement target 9 is recorded in the storage unit 10 or displayed on the display unit 40.

[0087] Therefore, steps S34 and S35 correspond to a resistance estimation step of estimating the real part value of the AC impedance X whose imaginary part value is zero among the AC impedances having a frequency lower than the vertex frequency Fp of the approximate circle Ca calculated by step S33 as the DC resistance of the measurement target 9.

[0088] When the process of step S35 is completed, the DCR estimation process of step S3 ends, and the process returns to the process procedure shown in FIG. 4, and a series of process procedures for the measurement method ends.

[0089] Next, the operation and effect according to the first embodiment will be described.

[0090] The resistance measuring device 1 in the first embodiment includes a measurement data acquisition unit 21 that functions as an acquisition means for acquiring measurement data indicating the frequency characteristics of the AC impedance obtained based on the response signal generated in the measurement target in a state where a signal having an AC component is supplied to the measurement target 9. Further, the resistance measuring device 1 includes an arc data extraction unit 22 that functions as an extraction means for extracting at least the frequency characteristics of the AC impedance having a frequency lower than the vertex frequency Fp of the AC impedance P whose tangent is parallel to the axis representing the real part among the arcs R in the lowest frequency region FRmin in the Nyquist diagram from the measurement data.

[0091] In addition, the resistance measuring device 1 includes a circle fitting calculation unit 23A that functions as a calculation means for calculating a circle Ca that approximates the shape (Rr) of the frequency characteristics of the AC impedance extracted by the arc data extraction unit 22 in the Nyquist diagram. Then, in the circle Ca calculated by the circle fitting calculation unit 23A, the resistance measuring device 1 includes a DC resistance estimation unit 23B that functions as a resistance estimation means for estimating the value of the real part of the AC impedance X whose imaginary part value is zero among the AC impedances having a frequency lower than the peak frequency Fp as the DC resistance (DCR) of the measurement target 9.

[0092] Also, the measurement method in the first embodiment includes an acquisition step (S31) of acquiring the above measurement data, and an extraction step (S32) of extracting at least the frequency characteristics of the AC impedance having a frequency lower than the peak frequency Fp of the AC impedance P whose tangent is parallel to the axis representing the real part among the arcs R in the lowest frequency region FR in the Nyquist diagram from the measurement data. Further, the measurement method includes a calculation step (S33) of calculating a circle that approximates the shape (Rr) of the frequency characteristics of the AC impedance extracted in step S32 in the Nyquist diagram, and a resistance estimation step (S34 and S35) of estimating the value of the real part of the AC impedance X whose imaginary part value is zero among the AC impedances having a frequency lower than the peak frequency Fp of the circle Ca calculated in step S33 as the DC resistance (DCR) of the measurement target 9.

[0093] Furthermore, the program stored in the storage unit 10 in the first embodiment is a program for executing each step (S31 to S35) included in the above measurement method.

[0094] According to these resistance measuring devices 1, measuring methods, and program configurations, by approximating the shape of the frequency characteristics of the AC impedance at frequencies lower than the peak frequency Fp in the Nyquist diagram to a circular shape, the value of the real part where the imaginary part on the approximated circle Ca becomes zero can be estimated as the DC resistance of the measurement target 9. Such processing can reduce the processing load required for calculating the DC resistance compared to general processing that performs equivalent circuit analysis to calculate the DC resistance.

[0095] Also, the arc data extraction unit 22 in the first embodiment extracts only the frequency characteristics of the AC impedance with a frequency lower than the peak frequency Fp or only the frequency characteristics of the AC impedance with a frequency less than or equal to the peak frequency Fp from the measurement data. According to this configuration, the accuracy of estimating the DC resistance of the measurement target 9 can be improved.

[0096] Further, the resistance measuring device 1 in the first embodiment may further include a compression device 3 that functions as a compression means for compressing the measurement target 9, and an AC measuring device 2 that functions as a measuring means for measuring the frequency characteristics of the AC impedance regarding the measurement target 9 in a state where the measurement target 9 is compressed by the compression device 3.

[0097] According to this configuration, when the measurement target 9 is an object with a high molding pressure as a product and has a capacitance component, it becomes possible to measure the AC impedance of the measurement target 9 in a state that conforms to the actual product state. Therefore, the electrical characteristics of the measurement target 9 can be measured in a state that conforms to the product state. In addition to this, since the DC resistance of the measurement target 9 can also be obtained by measuring the AC impedance, the DC resistance of the measurement target 9 can be measured with a simple configuration without separately preparing a DC resistor.

[0098] Thus, according to the above configuration, the DC resistance of the measurement target 9 can be measured in a state that conforms to the product state by measuring the AC impedance with simple processing and a simple configuration.

[0099] Also, in the first embodiment, the estimated DC resistance is the resistance of the entire bulk portion of the measurement object 9. Therefore, the estimated DC resistance suppresses the influence of the resistance components of the pair of electrode portions 31a and 31b for compressing the measurement object 9, and the DC resistance of the measurement object 9 with high measurement accuracy can be obtained.

[0100] Also, the measurement object 9 in the first embodiment is a powder containing a solid electrolyte. According to this configuration, the DC resistance of a battery such as an all-solid-state battery made of a powder containing a solid electrolyte can be accurately measured with simple processing.

[0101] (Second Embodiment) In the first embodiment, an example in which an object with a single arc R on the Nyquist diagram is used as the measurement object 9 has been described. However, there are also objects having electrical characteristics in which a plurality of arcs R are formed on the Nyquist diagram. It is also possible to measure the DCR even when such an object is used as the measurement object 9. Therefore, an estimation method for the DCR of a measurement object in which a plurality of arcs are formed on the Nyquist diagram will be briefly described with reference to FIG. 7.

[0102] FIG. 7 is a diagram for explaining an estimation method for the DCR of the measurement object 9 using circle fitting in the second embodiment. The measurement system of the second embodiment has the same configuration as the measurement system 100 of the first embodiment, and the same components will be described with the same reference numerals as in the first embodiment.

[0103] As shown in FIG. 7, unlike the first embodiment, the measurement object 9 of the second embodiment has electrical characteristics in which two arcs are drawn in the Cole-Cole plot diagram. Examples of objects having electrical characteristics in which a plurality of arcs are drawn include, for example, a mixture such as a slurry for manufacturing an electrode of a battery or a powder of an all-solid-state battery.

[0104] Specifically, in the call call plot diagram shown in FIG. 7, two arcs R drawn based on the measurement data acquired by the measurement data acquisition unit 21 are indicated by dotted lines. Among the two arcs R, the arc to be subjected to circle fitting is the arc R in the lowest frequency region FRmin1.

[0105] Further, in FIG. 7, the frequency of the AC impedance P1 whose tangent is parallel to the real axis among a group of AC impedances included in the measurement data is shown as the peak frequency Fp1. In the second embodiment, the peak frequency Fp1 of the AC impedance P1 is the upper limit of the arc data to be subjected to circle fitting. And the frequency of the AC impedance B1 is the lower limit of the arc data, and is the frequency of the AC impedance among a group of AC impedances having a lower frequency than the peak frequency Fp1 where the absolute value of the imaginary part is the minimum.

[0106] As shown in FIG. 7, first, the measurement data acquired by the measurement data acquisition unit 21 is displayed as two arcs R on the display unit 40 in the call call plot diagram. Then, the measurer designates a group of AC impedances on the low-frequency side among the two arcs R as the object of circle fitting.

[0107] Specifically, the measurer designates, on the operation unit 30, the frequency range from the peak frequency Fp1 of the AC impedance P1 to the lower limit frequency of the AC impedance B1 from among the measurement data displayed on the display unit 40. As a result, the arc data extraction unit 22 extracts, from the measurement data, the arc data indicating a group of AC impedances in the frequency range designated on the operation unit 30. Then, the circle fitting calculation unit 23A performs circle fitting on the shape of the arc Rr1 drawn by the extracted arc data, and as a result, an approximate circle Ca1 is calculated.

[0108] Subsequently, in the DC resistance estimation unit 23B, the real part value of the intersection point (X1) of the approximate circle Ca1 and the real axis is estimated as the DCR of the measurement target 9. That is, in the approximate circle Ca1 calculated by the circle fitting calculation unit 23A, the real part value of the AC impedance X1 with a zero imaginary part value among the AC impedances having a frequency lower than the vertex frequency Fp1 of the AC impedance P1 is estimated as the DC resistance of the measurement target 9.

[0109] Thus, when there are a plurality of circular arcs R, the inventors have found that by performing circle fitting on a group of AC impedances with a frequency lower than the vertex frequency Fp1 of the circular arc R in the lowest frequency region FRmin1, the real part value of the intersection point (X1) of the approximate circle Ca1 and the real axis can be regarded as the DCR of the measurement target 9.

[0110] Subsequently, the operation and effect according to the second embodiment will be briefly described.

[0111] In the second embodiment, even for the measurement target 9 having electrical characteristics in which a plurality of circular arcs R are drawn in the Nyquist diagram, the DC resistance of the measurement target 9 can be estimated by performing circle fitting on the circular arc R in the lowest frequency region FRmin1 among the plurality of circular arcs R in the same manner as in the first embodiment.

[0112] (Third Embodiment) In the first embodiment, the arc data extraction unit 22 generates arc data according to the input operation of the measurer. However, the present invention is not limited to this, and the arc data extraction unit 22 may automatically extract arc data. Therefore, an embodiment in which the arc data extraction unit 22 extracts arc data without the measurer performing an input operation will be described with reference to FIG. 8.

[0113] FIG. 8 is a flowchart showing a method for extracting arc data by the arc data extraction unit 22 according to the third embodiment. The measurement system according to the third embodiment is the same as or equivalent to the configuration of the measurement system 100 shown in FIG. 1, and the same or equivalent configurations will be described with the same reference numerals as those in the first embodiment.

[0114] FIG. 8 shows an example of the processing procedure of the extraction method according to the third embodiment in the arc data extraction process of step S32 shown in FIG. 6. Since other processes are the same as those described in FIGS. 4 to 6, the description of the same processes is omitted.

[0115] In step S321, the arc data extraction unit 22 identifies the upper limit frequency of the AC impedance Zmax at which the absolute value of the imaginary part is maximum from the measurement data indicating the arc R in the lowest frequency region FRmin on the Nyquist diagram. In FIG. 3, the peak frequency Fp of the AC impedance P corresponds to the upper limit frequency of the AC impedance Zmax.

[0116] In addition, as shown in FIG. 7, when a plurality of arcs R are drawn on the Nyquist diagram, the arc data extraction unit 22 may, for example, search for the AC impedance that becomes the minimum point from the measurement data and identify the AC impedance from the minimum point of the lowest frequency to the second lowest frequency minimum point as the arc R in the lowest frequency region FRmin on the Nyquist diagram.

[0117] In addition to this, the arc data extraction unit 22 may determine whether the arc R in the lowest frequency region FRmin is suitable as an arc to be subjected to circle fitting calculation by the circle fitting calculation unit 23A. As a specific example, the arc data extraction unit 22 determines whether the slope of the tangent line at the pole on the low frequency side of the arc is positive among a group of AC impedances included in the arc, and determines that it is not suitable as an object of circle fitting when the slope of the tangent line is positive. When it is determined that it is not suitable as an object of circle fitting, the processing unit 20 ends the processing procedure of the measurement method shown in FIG. 4.

[0118] In step S322, the arc data extraction unit 22 identifies the peak frequency Fp of the AC impedance P whose tangent line is parallel to the real axis from the measurement data indicating the arc R in the lowest frequency region FRmin on the Nyquist diagram.

[0119] Then, the arc data extraction unit 22 identifies the lower limit frequency of the AC impedance Zmin with the minimum absolute value of the imaginary part among a group of AC impedances at frequencies lower than the specified vertex frequency Fp, that is, a group of AC impedances on the lower frequency side of the arc R. In FIG. 3, the frequency of the AC impedance B corresponds to the lower limit frequency of the AC impedance Zmin.

[0120] In this way, in steps S321 and S322, the arc data extraction unit 22 identifies, from the measurement data, the upper limit frequency of the AC impedance Zmax and the lower limit frequency of the AC impedance Zmin among the arcs R in the lowest frequency region FRmin in the Nyquist diagram.

[0121] In step S323, the arc data extraction unit 22 outputs a group of AC impedances from the lower limit frequency of the AC impedance Zmin to the upper limit frequency of the AC impedance Zmax as arc data to the circular fitting calculation unit 23A.

[0122] Subsequently, the operation and effect according to the third embodiment will be described.

[0123] According to the configuration of the third embodiment, since it has the same configuration as the first embodiment, the same operation and effect as the first embodiment can be achieved.

[0124] Also, in the third embodiment, the arc data extraction unit 22 identifies the upper limit frequency of the AC impedance Zmax with the maximum imaginary part among the arcs R in the Nyquist diagram from the measurement data acquired by the measurement data acquisition unit 21. Further, the arc data extraction unit 22 identifies the lower limit frequency of the AC impedance Zmin with the minimum imaginary part on the lower frequency side of the arc R from the measurement data. Then, the arc data extraction unit 22 extracts a group of AC impedances from the specified upper limit frequency to the lower limit frequency as frequency characteristics.

[0125] According to this configuration, the frequency characteristics of the AC impedance to be subjected to circular fitting can be extracted without the measurer performing an input operation. As a result, while reducing the work load of the measurer, the DC resistance of the measurement target 9 can be estimated by simple processing.

[0126] As described above, the embodiments of the present invention have been explained. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0127] For example, in the above embodiment, an example in which powder is adopted as the measurement target 9 has been described. However, the measurement target 9 only needs to have electrical characteristics in which the arc in the lowest frequency region extends to the lower frequency side than the apex, and may be a liquid or a mixed liquid having a capacitance component. In this case, the AC measuring device 2 measures the frequency characteristics of the AC impedance of the measurement target 9 in a state where the container containing the pair of electrode portions is filled with the liquid or the mixed liquid. It is possible to apply the DCR estimation process of the above embodiment to such a measurement target 9.

[0128] Also, in the above embodiment, in order to measure the AC impedance of the measurement target 9, an AC constant voltage is applied to the measurement target 9 and the response current generated in the measurement target 9 is detected. However, the present invention is not limited to this. For example, even a measuring device that measures the AC impedance of the measurement target 9 by supplying an AC constant current to the measurement target 9 and detecting the response voltage generated in the measurement target 9 in this state can apply the configuration of the above embodiment.

Explanation of Reference Numerals

[0129] 100 Measurement system 1 Resistance measuring device 2 AC measuring device 3 Compression device 20 Processing unit 21 Measurement data acquisition unit (acquisition means) 22 Arc data extraction unit (extraction means) 23A Circular fitting calculation unit (calculation means) 23B DC Resistance Estimation Unit (Resistance Estimation Means) FRmin, FRmin1 Lowest Frequency Region R Arc Rr Arc to be Fitted by a Circle Fp, Fp1 Peak Frequency Ca, Ca1 Approximate Circle A, B(Zmin), B1, P(Zmax) AC Impedance of the Arc X AC Impedance of the Approximate Circle S31~S33 (Acquisition Step, Extraction Step, Calculation Step) S34~S35 (Resistance Estimation Step)

Claims

1. An acquisition means for acquiring measurement data indicating frequency characteristics of an AC impedance obtained based on a response signal generated in the measurement target in a state where a signal having an AC component is supplied to the measurement target; An extraction means for extracting at least frequency characteristics of the AC impedance lower than a vertex frequency of the AC impedance where a tangent line is parallel to an axis representing a real part among arcs in the lowest frequency region in a Nyquist diagram from the measurement data; A calculation means for calculating a circle approximating the shape of the frequency characteristics of the AC impedance extracted by the extraction means in the Nyquist diagram; A resistance estimation means for estimating, as a DC resistance of the measurement target, a value of a real part of the AC impedance having a zero value of an imaginary part among the AC impedances having a frequency lower than the vertex frequency in the circle calculated by the calculation means; A measuring device comprising:

2. The measuring device according to claim 1, wherein the extraction means extracts only frequency characteristics of the AC impedance having a frequency lower than the vertex frequency from the measurement data. A measuring device.

3. The measuring device according to claim 1, wherein the extraction means identifies an upper limit frequency of the AC impedance where an imaginary part becomes maximum and a lower limit frequency of the AC impedance where the imaginary part becomes minimum among the arcs in the Nyquist diagram from the measurement data, and extracts a group of AC impedances from the identified upper limit frequency to the lower limit frequency as the frequency characteristics. A measuring device.

4. The measuring device according to claim 1, further comprising a compression means for compressing the measurement target, and a measurement means for measuring frequency characteristics of the AC impedance related to the measurement target in a state where the measurement target is compressed by the compression means. A measuring device.

5. The measuring device according to claim 4, wherein the DC resistance is a resistance of the entire bulk portion of the measurement target. A measuring device.

6. The measuring device according to claim 5, wherein the measurement target is a powder containing a solid electrolyte. A measuring device.

7. An acquisition step of acquiring measurement data indicating frequency characteristics of an AC impedance obtained based on a response signal generated in the measurement target in a state where a signal having an AC component is supplied to the measurement target; An extraction step of extracting at least the frequency characteristics of the AC impedance that is lower than the apex frequency of the AC impedance at which the tangent becomes parallel to the axis representing the real part among the arcs in the lowest frequency region in the Nyquist diagram from among the measurement data; A calculation step of calculating a circle that approximates the shape of the frequency characteristics of the AC impedance extracted by the extraction step in the Nyquist diagram; A resistance estimation step of estimating the value of the real part of the AC impedance whose imaginary part value is zero among the AC impedances having a frequency lower than the apex frequency of the circle calculated by the calculation step as the DC resistance of the measurement target; A measurement method including the above.

8. A computer that acquires measurement data indicating the frequency characteristics of the AC impedance obtained based on the response signal generated in the measurement target in a state where a signal having an AC component is supplied to the measurement target, An extraction step of extracting at least the frequency characteristics of the AC impedance that is lower than the apex frequency of the AC impedance at which the tangent becomes parallel to the axis representing the real part among the arcs in the lowest frequency region in the Nyquist diagram from among the measurement data; A calculation step of calculating a circle that approximates the shape of the frequency characteristics of the AC impedance extracted by the extraction step in the Nyquist diagram; A resistance estimation step of estimating the value of the real part of the AC impedance whose imaginary part value is zero among the AC impedances having a frequency lower than the apex frequency of the circle calculated by the calculation step as the DC resistance of the measurement target; A program for causing the above to be executed.

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