JP6287125B2 - Function creation program, function creation method, function creation device, and charging rate estimation program - Google Patents

Description

  The present invention relates to a function creation program, a function creation method, a function creation device, and a charging rate estimation program.

  Conventionally, a secondary battery that can be repeatedly used by charging is known. Examples of the secondary battery include a lithium ion secondary battery. In order to grasp how much the remaining power is stored in the secondary battery, it is important in operating to obtain a state of charge (SoC) accurately. Therefore, for example, a technique for estimating the charging rate of the secondary battery from the terminal voltage of the secondary battery is known.

JP 2005-189028 A JP 2007-187638 A

  By the way, the secondary battery is an electrochemical component that chemically accumulates electricity, and has various characteristics such as non-linear formation, temperature dependence, and transient characteristics. For this reason, for example, the secondary battery is modeled by an equivalent circuit in which a plurality of circuit components such as a resistor R and a capacitor C are combined, and the charging rate is estimated using a Kalman filter based on the equivalent circuit. The electrical characteristic values of the circuit components, such as the resistance value of the resistor R and the capacitance of the capacitor C, are set by performing regression analysis based on measurement data obtained through experiments or the like, for example.

  However, since the secondary battery has various characteristics as described above, the characteristic values of the circuit components vary greatly. For this reason, the characteristic value of the circuit component obtained by the regression analysis is optimal for the measurement data, but the estimation accuracy of the charging rate may be reduced under conditions different from the conditions under which the measurement data was measured.

  In one aspect, an object of the present invention is to provide a function creation program, a function creation method, a function creation device, and a charge rate estimation program that can suppress a decrease in charging rate estimation accuracy.

  The function creation program according to one aspect of the present invention indicates a change in the electrical characteristic value of a circuit component that constitutes the internal resistance in an equivalent circuit that equivalently shows a secondary battery to a computer by calculating a current value and a parameter. Execute the process to get the function. The function creation program switches the current flowing through the terminal used for charging and discharging the power of the secondary battery and analyzes the function using the measurement data obtained by measuring the current and the terminal voltage every predetermined time. A process for specifying the parameter value is executed. The function creation program causes the computer to execute a process of outputting information related to the specific result.

  A decrease in the estimation accuracy of the charging rate can be suppressed.

FIG. 1 is a diagram schematically illustrating an example of a flow in which a lithium ion battery is used. FIG. 2 is a diagram illustrating the overall configuration of the function creation device. FIG. 3 is a diagram illustrating an example of an equivalent circuit of a lithium ion battery. FIG. 4 is a diagram illustrating an example of a data configuration of measurement data. FIG. 5 is a diagram illustrating an example of a characteristic curve. FIG. 6 is a diagram illustrating an example of the data structure of the correction data. FIG. 7 is a flowchart showing the procedure of the function creation process. FIG. 8 is a diagram illustrating an example of a computer that executes a function creation program.

  A function creation program, a function creation method, a function creation device, and a charge rate estimation program according to the present application will be described below with reference to the accompanying drawings. Note that this embodiment does not limit the disclosed technology. Each embodiment can be appropriately combined within a range in which processing contents are not contradictory.

[Secondary battery]
First, the secondary battery will be briefly described. Examples of the secondary battery include a lithium ion secondary battery. Hereinafter, a lithium ion secondary battery will be described as an example of the secondary battery. Hereinafter, the lithium ion secondary battery is also referred to as a lithium ion battery.

  Lithium ion batteries are used in various devices such as personal computers, mobile phones, electric cars, and electric motorcycles. For example, in an electric vehicle, an electric motorcycle, or the like, it is known to replace a secondary battery such as a lithium ion battery together with a module so as to eliminate a loss of usage time due to charging time. As described above, since lithium ion batteries are used in various devices, it is important to obtain a charging rate with high accuracy.

  FIG. 1 is a diagram schematically illustrating an example of a flow in which a lithium ion battery is used. In the example of FIG. 1, a schematic configuration of the lithium ion battery 10 is shown. The lithium ion battery 10 includes a cell 11 and a control chip 12. The cell 11 is a component capable of storing and discharging electric power by a chemical change. The control chip 12 is a control IC (Integrated Circuit) that controls the lithium ion battery 10. The control chip 12 includes a storage unit 12A such as a nonvolatile memory. The storage unit 12A stores various programs and various information used for controlling the lithium ion battery 10. For example, the storage unit 12A stores a charging rate estimation program for estimating the charging rate. Further, for example, various kinds of information used for estimating the charging rate is stored in the storage unit 12A. As an example, the storage unit 12A stores information on an approximate function that approximates a characteristic curve. Information about the approximate function is created by the function creation device 20 based on, for example, measurement data obtained by measuring the electrical characteristics of the cell 11 through experiments or the like. The characteristics of the lithium ion battery 10 are different for each type such as a model number. Further, the lithium ion battery 10 may have different characteristics for each manufactured unit or individual. The approximate function information may be created by obtaining measurement data for each type of lithium ion battery 10 or may be created by obtaining measurement data for each unit or individual. The lithium ion battery 10 is mounted and used in various devices 21. The control chip 12 functions as a processing unit that performs various controls by operating various programs. For example, the control chip 12 has an estimation unit 12B as a processing unit by operating a charging rate estimation program. The estimation unit 12B estimates the charging rate based on various information such as the terminal voltage of the lithium ion battery 10 and information on the approximate function stored in the storage unit 12A. For example, the control chip 12 estimates the charging rate using a Kalman filter. The control chip 12 performs various controls. For example, when the charge rate of the cell 11 is estimated and the cell 11 is overcharged or overdischarged, the control chip 12 performs control to cut off the current from the terminal used for charging and discharging power.

  Note that characteristics of the secondary battery such as the lithium ion battery 10 may change over time. For this reason, the information stored in the storage unit 12A may be updatable. For example, a program capable of creating function information is stored in the storage unit 12A of the control chip 12, the control chip 12 measures the electrical characteristics of the cell 11, and creates function information based on the measured measurement data. May be. In this case, the control chip 12 or the lithium ion battery 10 functions as the function creation device 20. The function information may be updated via the network 23. For example, the device 21 transmits measurement data obtained by measuring the electrical characteristics of the cell 11 to the function creation device 20 via the network 23. The function creation device 20 may return information on the function created based on the measurement data via the network 23 to update the information stored in the storage unit 12A.

  Next, the function creation device 20 according to the first embodiment will be described. FIG. 2 is a diagram illustrating the overall configuration of the function creation device. As illustrated in FIG. 2, the function creation device 20 includes an external I / F (interface) unit 30, a display unit 31, an input unit 32, a storage unit 33, and a control unit 34. Note that the function creation device 20 may include various functional units included in a known computer in addition to the functional units illustrated in FIG.

  The external I / F unit 30 is an interface that inputs and outputs information with other devices. For example, the external I / F unit 30 is an interface that performs communication control with other devices. As an aspect of the external I / F unit 30, a network interface card such as a LAN card can be employed. For example, the external I / F unit 30 receives measurement data 41 and function information 40 indicating the electrical characteristics of the cell 11 measured by an experiment or the like from another device. The external I / F unit 30 may be an interface such as a USB (Universal Serial Bus) port.

  The display unit 31 is a display device that displays various types of information. Examples of the display unit 31 include display devices such as an LCD (Liquid Crystal Display) and a CRT (Cathode Ray Tube). The display unit 31 displays various information.

  The input unit 32 is an input device that inputs various types of information. For example, examples of the input unit 32 include input devices such as a mouse and a keyboard. The input unit 32 receives an operation input from an administrator or the like, and inputs operation information indicating the received operation content to the control unit 34.

  The storage unit 33 is a storage device that stores various data. For example, the storage unit 33 is a storage device such as a hard disk, an SSD (Solid State Drive), or an optical disk. Note that the storage unit 33 may be a semiconductor memory that can rewrite data, such as a random access memory (RAM), a flash memory, and a non-volatile static random access memory (NVSRAM).

  The storage unit 33 stores an OS (Operating System) executed by the control unit 34 and various programs. For example, the storage unit 33 stores various programs used for creating a function to be described later. Furthermore, the storage unit 33 stores various data used in the program executed by the control unit 34. For example, the storage unit 33 stores function information 40, measurement data 41, characteristic data 42, and correction data 43. The storage unit 33 can also store other electronic data in addition to the information exemplified above.

  The function information 40 is data storing function information indicating changes in the electrical characteristic values of the lithium ion battery 10.

  Here, the lithium ion battery 10 is an electrochemical component, but can be modeled by an equivalent circuit in which a plurality of circuit components such as a resistor R and a capacitor C are combined. By thus modeling the lithium ion battery 10 with an equivalent circuit, a standard design using a circuit including the lithium ion battery 10 can be performed.

FIG. 3 is a diagram illustrating an example of an equivalent circuit of a lithium ion battery. In the equivalent circuit 60 shown in FIG. 3, a power source 61, a resistor 62, and two RC circuits 63 and 64 are connected in series. In the equivalent circuit 60, the resistor 62 and the RC circuits 63 and 64 function as internal resistors. The RC circuit 63 is configured by connecting a resistor 65 and a capacitor 66 in parallel. The RC circuit 64 is configured by connecting a resistor 67 and a capacitor 68 in parallel. In the power supply 61, a voltage is generated by the accumulated power. The voltage generated by the power supply 61 is an open circuit voltage (OCV). The power supply 61 has an OCV that varies depending on the charging rate (SoC). In addition, the power supply 61 has an OCV that varies between charging and discharging even when the charging rate is the same. For this reason, in the example of FIG. 3, the power source 61 is divided into two paths for charging and discharging. When the potential difference between both ends of the resistor 62 is v ₀ , the potential difference between both ends of the RC circuit 63 is v _1, and the potential difference between both ends of the RC circuit 64 is v ₂ , the terminal voltage v of the terminal 69 is expressed by the following equation (1). It can be expressed as

v = OCV + v ₀ + v ₁ + v ₂ (1)

In this embodiment, the resistance value of the resistor 62 is R0, the resistance value of the resistor 65 is R1, the resistance value of the resistor 67 is R2, the capacitance of the capacitor 66 is C1, and the capacitance of the capacitor 68 is C2. In the equivalent circuit 60, when the resistance values R0, R1, R2, and the capacitors C1, C2 are determined, the potential differences v ₀ , v ₁ , v ₂ can be obtained from the flowing current I. Further, in the equivalent circuit 60, when the potential differences v ₀ , v ₁ , and v ₂ are obtained, the OCV is obtained, and the charging rate can be obtained from the OCV. For example, when the resistance values R0, R1, R2, and the capacitances C1, C2 are obtained by performing regression analysis based on the measurement data obtained through experiments, the resistance values R0, R1, R2, and the capacitances C1, C2 are negative. In some cases, the value may logically fail. In addition, the resistance values R0, R1, R2, and the capacitors C1, C2 are optimal for the measurement data, but the accuracy is low under conditions different from the conditions under which the measurement data is measured, and the estimation accuracy of the charging rate is reduced. There is. Therefore, the change in the electrical characteristic value of the circuit component constituting the internal resistance is represented by a function indicated by the calculation of the current value and the parameter. This function is determined by, for example, an administrator or a designer of the lithium ion battery 10. Then, the parameter value of the function is obtained by regression analysis, and the electrical characteristic value of the circuit component is specified using the function in which the obtained value is set.

  For example, the resistance values R0, R1, R2, and the capacitors C1, C2 are expressed as a function of the current I as shown in the following equations (2) to (6). | I | represents the absolute value of the current I.

1 / R0 = a × | I | + b (2)
1 / R1 = a ₁ × | I | + b ₁ (3)
1 / R2 = a ₂ × | I | + b ₂ (4)
C1 = m ₁ × | I | + n ₁ (5)
C2 = m ₂ × | I | + n ₂ (6)

a, a ₁ , a ₂ , b, b ₁ , b ₂ , m ₁ , m ₂ , n ₁ , n ₂ represent parameters.

  In the present embodiment, the equivalent circuit 60 is configured such that the power supply 61, one resistor, and two RC circuits are connected in series, but is not limited thereto. The equivalent circuit 60 may be any as long as it shows the characteristics of the lithium ion battery 10 equivalently. For example, in the equivalent circuit 60, one or more resistors may be connected, two or more RC circuits may be connected, and a coil may be further connected.

  Returning to FIG. 2, the function information 40 stores function information indicating changes in electrical characteristic values of the resistance values R0, R1, and R2, and the capacitors C1 and C2. For example, the function information 40 stores function information shown in equations (2) to (6). The function information 40 may be registered from the input unit 32. Also, the function information 40 may be registered from an external device via the external I / F unit 30.

The measurement data 41 is data obtained by, for example, experiments or the like regarding the electrical characteristics of the lithium ion battery 10. For example, the measurement data 41 is data obtained by switching the current I flowing through the terminal 69 used for charging and discharging the power of the lithium ion battery 10 and measuring the current I, the voltage v of the terminal 69, and the charging rate every predetermined time. . For example, the current I flowing through the terminal 69 of the lithium ion battery 10 is changed from + I ₁ A to -I ₁ A in a range where the current has the same absolute value and a different sign, and the voltage v and the charging rate of the terminal 69 are changed every second. measure. The sign of the current I indicates a charged state in which a current flows to the lithium ion battery 10 when positive, and a discharged state where a current flows from the lithium ion battery 10 when negative. A plurality of pieces of measurement data 41 having different ranges in which the current flowing through the terminal 69 is switched are prepared. For example, three types of measurements with different current switching ranges are performed, and measurement data 41 is stored in the storage unit 33 together with information on the switched current range. In addition, in order to suppress the influence by switching of the previous current, measurement is started after a sufficient time has passed before switching the current I. Further, even after the current I is switched, measurement is performed until the voltage becomes stable. For example, it is assumed that the measurement is performed until the change in voltage over time is within a range where the voltage can be considered stable.

FIG. 4 is a diagram illustrating an example of a data configuration of measurement data. The example of FIG. 4 is an example of measurement data measured by switching the current from + I ₁ A to −I ₁ A. The measurement data 41 can employ a table in which items such as time, measurement voltage, and SoC are associated. The item of time is an area for storing an elapsed time from a predetermined time. In the time item, time may be stored. In the time item, an elapsed time after the start of measurement may be stored. The measurement voltage item is an area for storing the measured voltage value of the terminal 69. The item of SoC is an area for storing the measured charging rate. In the example of FIG. 4, when the time is 234 seconds, the voltage value of the terminal 69 is 2480 mV, and the charging rate is 0.41.

  The characteristic data 42 is data obtained by, for example, an experiment or the like, for example, a characteristic curve showing a correlation between the OCV of the lithium ion battery 10 and the charging rate. For example, the characteristic data 42 stores an OCV for each charging rate.

  FIG. 5 is a diagram illustrating an example of a characteristic curve. The example of FIG. 5 shows the correlation between the OCV of the lithium ion battery 10 and the charging rate. As shown in FIG. 5, there is a correlation between the OCV and the charging rate of the lithium ion battery 10. In the characteristic curve, the change in OCV with respect to the change in the charge rate is large in the range where the charge rate is high and the range where the charge rate is low.

  The correction data 43 among the information stored in the storage unit 33 will be described later in conjunction with the description of the functional unit that generates, acquires, or uses the information.

  The control unit 34 has an internal memory for storing programs defining various processing procedures and control data, and executes various processes using these. As shown in FIG. 2, the control unit 34 includes an acquisition unit 50, a calculation unit 51, a first specification unit 52, a second specification unit 53, a third specification unit 54, and an output unit 55.

  The acquisition unit 50 is a processing unit that acquires various types of information. For example, the acquisition unit 50 acquires a function indicating a change in the electrical characteristic value of a circuit component constituting the internal resistance in the equivalent circuit 60. For example, the acquisition unit 50 acquires function data by reading out function data indicating changes in electrical characteristic values of the resistance values R0, R1, and R2, and the capacitors C1 and C2 stored in the function information 40. . In this embodiment, since the function information 40 is stored in the storage unit 33, the acquisition unit 50 acquires the function information 40 from the storage unit 33. However, the present invention is not limited to this. When the function information 40 is stored in another device, the acquisition unit 50 may acquire the function information 40 from the other device via the network 23.

  The calculation unit 51 is a processing unit that performs various calculations. For example, the calculation unit 51 obtains the OCV at each time from the charging rate at each time of the measurement data 41 based on the characteristic data 42. The calculation unit 51 then subtracts the OCV of the corresponding time from the voltage of the terminal 69 of each time of the measurement data 41 to calculate the voltage due to the internal resistance of each time. The calculation unit 51 stores the calculated voltage at each time as the correction data 43. That is, the calculation unit 51 generates correction data 43 by performing correction by removing the OCV of the power supply 61 from the measurement voltage of the measurement data 41. In addition, the calculation unit 51 corrects each time of the measurement data 41 to an elapsed time from the start of measurement, with the first time as the start time of measurement.

  Here, an example of the correction data 43 stored in the storage unit 33 will be described. FIG. 6 is a diagram illustrating an example of the data structure of the correction data. As the correction data 43, a table in which items such as time and correction voltage are associated can be adopted. The time item is an area for storing the elapsed time from the start of measurement. The item of the correction voltage is an area for storing a corrected voltage value obtained by correcting the measured voltage excluding the OCV. In the example of FIG. 6, when the time is 0 second, the correction voltage is 2480-OCV (0.41) mV. This OCV (0.41) is an OCV when the charging rate of the characteristic curve shown in FIG. 5 is 0.41.

By the way, in the equivalent circuit 60 shown in FIG. 3, the resistor 62 changes its potential difference v ₀ following the change of current, and does not cause a transient change. In this case, the resistance value R0 of the resistor 62 can be obtained from the current change ΔI and the voltage change ΔV due to current switching.

The first identification unit 52 is a processing unit that performs various types of identification regarding a resistance that does not cause a transient change among circuit components included in the equivalent circuit 60. For example, the first specifying unit 52 specifies a parameter value of a function indicating a change in the resistance value R0 of the resistor 62 that does not cause a transient change. For example, the first specifying unit 52 calculates a current change ΔI and a voltage change ΔV due to current switching for each measurement data 41. For example, when the current is switched from + I ₁ A to −I ₁ A, the first specifying unit 52 calculates the current change ΔI as 2I ₁ . The first specifying unit 52 calculates the voltage change ΔV from the difference between the voltage at which the correction data 43 starts measurement and the voltage at which the voltage change with respect to time has reached a stable state that is equal to or less than a predetermined allowable value. The first specifying unit 52 specifies the value of voltage change ΔV / current change ΔI as the resistance value R0 for each measurement data 41. When the lithium ion battery 10 has hysteresis in the characteristic curves during charging and discharging, it is preferable to perform correction by obtaining the voltage error H due to the hysteresis of the characteristic curve during charging and the characteristic curve during discharging. When the measurement data 41 is data for charging and discharging, the first specifying unit 52 divides the value (ΔV−H) obtained by subtracting the error H from the voltage change ΔV by the current change ΔI to obtain the resistance value R0. Identify the value. And the 1st specific | specification part 52 performs the linear regression analysis using the value of resistance value R0 for every measurement data 41, and the electric current value after switching about (2) Formula, and specifies the value of parameters a and b.

  The second identification unit 53 is a processing unit that performs various types of identification regarding circuit components that cause a transient change among circuit components included in the equivalent circuit 60. For example, the second specifying unit 53 specifies parameters related to resistors 65 and 67 and capacitors 66 and 68 constituting the two RC circuits 63 and 64 that cause a transient change.

  Here, from the equivalent circuit 60, the time change regarding the transient change of the voltage V can be expressed by the following equation (7).

Here, v ₁ ⁰ and v ₂ ⁰ are initial values of voltages of the RC circuits 63 and 64, respectively.

By the way, when the values of the parameters a ₁ , a ₂ , b ₁ , b ₂ , m ₁ , m ₂ , n ₁ , n ₂ shown in the above equations (3) to (6) are determined, the resistance values R1, R2 , Capacitances C1 and C2 can be calculated. Using the calculated resistance values R1 and R2, capacitances C1 and C2, and the resistance value R0 specified by the first specifying unit 52, the voltage of v ₀ + v ₁ + v ₂ shown in FIG. 3 can be calculated. Thereby, an error between this voltage and the correction voltage of the correction data can be measured. The second specifying unit 53 specifies the value of the parameter that minimizes this error by analysis.

The second specifying unit 53 defines resistance values R1> 0, R2> 0, capacitances C1> 0, and C2> 0 as constraints, and uses an optimization algorithm such as a genetic algorithm or a particle swarm optimization algorithm, for example. The analysis used is performed, and the parameter value of the function is specified for each measurement data 41. For example, the second specifying unit 53 assumes values of a ₁ , a ₂ , b ₁ , b ₂ , m ₁ , m ₂ , n ₁ , and n ₂ , respectively. And the 2nd specific | specification part 53 calculates resistance value R0, R1, R2, capacitance C1, C2 of each time of the correction data 43, and calculates the voltage V of the transient change of each time from Formula (7). And the 2nd specific | specification part 53 calculates | requires the difference | error of the voltage estimated from the equivalent circuit 60, and the measured voltage for every time. For example, the second specifying unit 53 obtains an error between the correction voltage and the voltage obtained by adding the voltage obtained by multiplying the current and the resistance value R0 and the voltage V of the transient change for each time. The second specifying unit 53 uses the mean square error of each time of the correction data 43 as an error index value, and a ₁ , a ₂ , b ₁ , b ₂ , m ₁ , m ₂ , Analyzing repeatedly changing the values of n ₁ and n _{2 is performed, and} the values of a ₁ , a ₂ , b ₁ , b ₂ , m ₁ , m ₂ , n ₁ , n _{2 with} the smallest error are specified. .

Here, v ₁ ⁰ and v ₂ ⁰ shown in the equation (7) are not specified by the optimization algorithm.

The third specifying unit 54 is a processing unit that specifies the initial value of the voltage of the circuit component. For example, the third specifying unit 54 specifies v ₁ ⁰ and v ₂ ⁰ . When the measurement data 41 is symmetric data, the third specifying unit 54 averages the voltage V1 of the terminal 69 immediately after switching the current and the voltage V2 of the terminal 69 when the current is switched to the stable state. The correction voltage of the correction data 43 is translated so that ((V1 + V2) / 2) becomes zero. As a result, the voltage at the terminal 69 immediately after switching the current can be set to V ′, and the voltage at the terminal 69 when the current becomes stable after switching the current can be set to −V ′. Thereby, the following formulas (8) to (10) are established.

V ′ = v ₁ ⁰ + v ₂ ⁰ (8)
v ₁ ⁰ = I × R1 = (V ′ × R1) / (R1 + R2) (9)
v ₂ ⁰ = I × R2 = (V ′ × R2) / (R1 + R2) (10)

Thus, v ₁ ^0, v ₂ ⁰ can be determined by only the resistance value R1, R 2. The third specifying unit 54 obtains v ₁ ⁰ and v ₂ ⁰ from the voltage V ′ as equations of the resistance values R1 and R2, and substitutes them into the above-described equation (7).

On the other hand, when the measurement data 41 is not symmetrical data, the third specifying unit 54 calculates the resistance value R0 from the current I after switching the current using the equation (2). Then, the third specifying unit 54 subtracts I × R0 from the correction voltage of the correction data 43 and performs translation. As a result, the following equation (11) is established for the initial voltage V ₀ ′ before switching the current of the correction data 43.

V ₀ ′ = v ₁ ⁰ + v ₂ ⁰ (11)

Further, assuming that the resistance value R1 for the current Ip before switching is R ^P 1 and the resistance value R2 is R ^P 2, the following equations (12) and (13) are established.

v ₁ ⁰ = Ip × R ^P 1 = (V ₀ ′ × R ^P 1) / (R ^P 1 + R ^P 2) (12)
v ₂ ⁰ = Ip × R ^P 2 = (V ₀ ′ × R ^P 2) / (R ^P 1 + R ^P 2) (13)

Thus, v ₁ ^0, v ₂ ⁰ can be determined by only the resistance value R1, R 2.

The second specifying unit 53 assigns v ₁ ⁰ and v ₂ ⁰ determined by the third specifying unit 54 to the equation (7), performs analysis for each measurement data 41, and specifies the value of the parameter of the function. The second specifying unit 53 specifies the value of each parameter by averaging the parameter values obtained for each measurement data 41 or performing regression analysis for each parameter.

  The output unit 55 is a processing unit that performs various outputs. For example, the output unit 55 outputs information related to the specific result. For example, the output unit 55 outputs a function in which the specified parameter value is set as a parameter. The output unit 55 may output the value of the specified parameter. The output by the output unit 55 may display information on the display unit 31. The output by the output unit 55 may output information to an external device via the external I / F unit 30.

  Information on the function in which the output parameter value is set as a parameter is stored in the storage unit 12 </ b> A of the control chip 12 of the lithium ion battery 10. The estimation unit 12B of the control chip 12 obtains the function information by reading it from the storage unit 12A. And the estimation part 12B estimates the charging rate of the lithium ion battery 10 using the information of the acquired function. For example, the estimation unit 12B measures the current and terminal voltage of the lithium ion battery 10. Further, the estimation unit 12B calculates the electrical characteristic value of the circuit component of the equivalent circuit of the lithium ion battery 10 using the function information from the current, and uses the Kalman filter or the like to calculate the charging rate of the cell 11 from the calculation result. presume. Here, the function information can predict a change in characteristics of the circuit components of the equivalent circuit of the lithium ion battery 10 with respect to the current. For this reason, the control chip 12 can estimate the charging rate with high accuracy using the information of the approximate function.

  Note that various integrated circuits and electronic circuits can be employed for the control unit 34. Further, a part of the functional unit included in the control unit 34 may be another integrated circuit or an electronic circuit. For example, an ASIC (Application Specific Integrated Circuit) is an example of the integrated circuit. Examples of the electronic circuit include a central processing unit (CPU) and a micro processing unit (MPU).

[Process flow]
Next, a function creation process flow in which the function creation device 20 according to the present embodiment creates a function of a circuit component constituting the internal resistance of the equivalent circuit 60 will be described. FIG. 7 is a flowchart showing the procedure of the function creation process. The function creation processing is started at a predetermined timing, for example, at a timing when a function creation is instructed from another device via the input unit 32 or the external I / F unit 30.

  As illustrated in FIG. 7, the acquisition unit 50 reads out function data indicating changes in the electrical characteristic values of the resistance values R0, R1, R2, and the capacitors C1, C2 stored in the function information 40 of the storage unit 33. Thus, function data is acquired (S10). Moreover, the acquisition part 50 acquires the measurement data 41 by reading the measurement data 41 of the memory | storage part 33 (S11). Based on the characteristic data 42, the calculation unit 51 performs correction by excluding the OCV of the power supply 61 from the measurement voltage of the measurement data 41 to generate correction data 43 (S12). For each measurement data 41, the first specifying unit 52 calculates the current change ΔI and the voltage change ΔV, and specifies the value of voltage change ΔV / current change ΔI as the resistance value R0 (S13).

The third specifying unit 54 specifies v ₁ ⁰ and v ₂ ⁰ for each measurement data 41 (S14). For example, when the measurement data 41 is symmetric data, the third specifying unit 54 determines the voltage V1 of the terminal 69 immediately after switching the current and the voltage V2 of the terminal 69 when the current becomes stable after switching the current. The correction voltage of the correction data 43 is moved in parallel so that the average of is zero. The third identifying unit 54, the voltage (9) from V'the immediately following terminal 69 of switching the current, the equation (10), v ₁ ^0, v ₂ ⁰ the resistance values R1, R2, capacitor C1, It is specified as an expression of C2. On the other hand, when the measurement data 41 is not symmetric data, the third specifying unit 54 subtracts I × R0 from the correction voltage of the correction data 43 and translates it. Then, the third specifying unit 54 calculates the initial voltage V ₀ ′ of the correction data 43 and the resistance values R ^P 1 and R ^P 2 for the current Ip before conversion. Then, the third specifying unit 54 calculates the v ₁ ⁰ and v ₂ ⁰ from the initial voltage V ₀ ′ and the resistance values R ^P 1 and R ^P 2 to the resistance values R 1, R 2, It is specified as an expression of capacitances C1 and C2.

  The 2nd specific | specification part 53 performs the analysis using an optimization algorithm using the correction data 43 of each measurement data 41, and specifies the value of each parameter of a function (S15). The output unit 55 outputs information on the specific result (S16), and ends the process.

[Effect of Example 1]
As described above, the function creation device 20 calculates the change in the electrical characteristic value of the circuit component that constitutes the internal resistance by the equivalent circuit 60 that equivalently shows the lithium ion battery 10 and calculates the current value and the parameter. Get the function indicated by. The function creation device 20 switches the current flowing through the terminal 69 used for charging and discharging the power of the lithium ion battery 10 and performs analysis using the measurement data 41 in which the current and the voltage of the terminal 69 are measured every predetermined time. Identify function parameter values. And the function production apparatus 20 outputs the information regarding a specific result. Thereby, since the function creation apparatus 20 can specify the function for obtaining the electrical characteristics of the internal resistance from the information on the identification result and can obtain the electrical characteristics of the internal resistance from the current value, the charging rate estimation accuracy Can be suppressed.

Further, the function creation device 20 obtains an open circuit voltage at each time from the charging rate at each time of the measurement data 41 based on the characteristic data 42, and calculates the corresponding time from the voltage at the terminal 69 at each time in the measurement data 41. The voltage due to the internal resistance at each time is calculated by subtracting the open circuit voltage . The function creation device 20 then calculates each time obtained from the calculated voltage due to the internal resistance at each time and the electrical characteristic value of the circuit component calculated by setting the current value of each time of the measurement data 41 as a function. The value of the parameter that minimizes the error from the voltage of the internal resistance is identified by analysis. As described above, by removing the influence of the open circuit voltage , the function creation device 20 according to the present embodiment accurately specifies the parameter of the function indicating the change in the electrical characteristic value of the circuit component constituting the internal resistance. be able to.

  Further, the function creation device 20 obtains the ratio of the current change with respect to the voltage change of the terminal 69 due to the switching of the current from the measurement data 41, and the resistance value of the resistor 62 that does not cause a transient change among the circuit components from the current change ratio. The value of the parameter of the function indicating the change in R0 is specified. Thereby, the function creation apparatus 20 according to the present embodiment can specify a function for obtaining the resistance value R0.

  In addition, when the measurement data 41 is measured by changing the range of the current having the same absolute value and different signs, the function creating device 20 uses the first voltage at the terminal 69 immediately after switching the current, or After the current is switched, the initial value of the voltage of the circuit component is specified using a value obtained by converting the second voltage of the terminal 69 when the stable state is obtained with the average of the first voltage and the second voltage being zero. . If the measurement data 41 is not measured by changing the range of the current with the same absolute value and different sign, the function creation device 20 calculates the transient change from the first voltage at the terminal 69 immediately after switching the current. The initial value of the voltage of the circuit component is specified using a value obtained by dividing the voltage drop due to the resistor that does not occur. Thereby, the function creation apparatus 20 according to the present embodiment can specify the initial value of the voltage of the circuit component.

  Although the embodiments related to the disclosed apparatus have been described above, the present invention may be implemented in various different forms other than the above-described embodiments. Therefore, another embodiment included in the present invention will be described below.

  For example, in the above-described embodiment, the case where a lithium ion battery is used as the secondary battery has been described, but the disclosed apparatus is not limited thereto. The secondary battery may be a lithium ion polymer secondary battery, a calcium ion secondary battery, a nanowire battery, a nickel metal hydride secondary battery, or a lead storage battery. Moreover, as a lithium ion battery, it is applicable also to a lithium cobalt ion battery, a lithium iron phosphate battery, etc. Thereby, the charge rate of various batteries can be measured.

  In the above embodiment, the case where the resistance value R of the resistor constituting the internal resistance in the equivalent circuit is a linear function with respect to 1 / R has been described, but the function is not limited to this. For example, the resistance value R monotonously decreases with current, and the decrease rate tends to decrease as the current increases. Any function having such a tendency may be used. For example, the functions shown in the following equations (14) to (18) may be used.

  In the above-described embodiment, the case where the function is a linear function with respect to the capacitance C of the capacitor constituting the internal resistance in the equivalent circuit has been described. However, the function is not limited to this. For example, the capacitance C increases monotonously with the magnitude of the current, and the increase rate tends to decrease as the current increases. Any function having such a tendency may be used. For example, the functions shown in the following equations (19) to (23) may be used.

[Distribution and integration]
In addition, each component of each illustrated apparatus does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to that shown in the figure, and all or a part thereof may be functionally or physically distributed or arbitrarily distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. For example, the acquisition unit 50, the calculation unit 51, the first specification unit 52, the second specification unit 53, the third specification unit 54, and the output unit 55 may be connected as an external device of the function creation device 20 via a network. . In addition, the acquisition unit 50, the calculation unit 51, the first specification unit 52, the second specification unit 53, the third specification unit 54, and the output unit 55 are provided in different devices, and are connected via a network to cooperate. You may make it implement | achieve the function of said function production apparatus 20. FIG.

[Function creation program]
The various processes described in the above embodiments can be realized by executing a prepared program on a computer such as a personal computer or a workstation. In the following, an example of a computer that executes a function creation program having the same function as that of the above embodiment will be described with reference to FIG. FIG. 8 is a diagram illustrating an example of a computer that executes a function creation program.

  As illustrated in FIG. 8, the computer 300 includes a central processing unit (CPU) 310, a read only memory (ROM) 320, a hard disk drive (HDD) 330, and a random access memory (RAM) 340. These units 310 to 340 are connected via a bus 400.

  The ROM 320 stores in advance a function creation program 320a that exhibits the same function as each processing unit of the above embodiment. For example, the function creation program 320a that performs the same functions as those of the acquisition unit 50, the calculation unit 51, the first specification unit 52, the second specification unit 53, the third specification unit 54, and the output unit 55 of the above embodiment is stored. Note that the function creation program 320a may be separated as appropriate.

  Then, the CPU 310 reads the function creation program 320a from the ROM 320 and executes it, thereby executing the same operation as in the above embodiment. That is, the function creation program 320a performs the same operations as the acquisition unit 50, the calculation unit 51, the first specification unit 52, the second specification unit 53, the third specification unit 54, and the output unit 55.

  The function creation program 320a described above does not necessarily need to be stored in the ROM 320 from the beginning. The function creation program 320a may be stored in the HDD 330.

  The ROM 320 may store a charging rate estimation program for estimating the charging rate. In this case, a charging rate estimation program that exhibits the same function as the estimation unit 12B of the above embodiment is stored. Note that the charging rate estimation program may be appropriately separated.

  In this case, the CPU 310 reads the charge rate estimation program from the ROM 320 and executes it, thereby executing the same operation as in the above embodiment. That is, the charging rate estimation program performs the same operation as that of the estimation unit 12B.

  Note that the above-described charging rate estimation program is not necessarily stored in the ROM 320 from the beginning. The charging rate estimation program may be stored in the HDD 330.

  Further, for example, the program is stored in a “portable physical medium” such as a flexible disk (FD), a CD-ROM, a DVD disk, a magneto-optical disk, an IC card or the like inserted into the computer 300. Then, the computer 300 may read and execute the program from these.

  Furthermore, the program is stored in “another computer (or server)” connected to the computer 300 via a public line, the Internet, a LAN, a WAN, or the like. Then, the computer 300 may read and execute the program from these.

DESCRIPTION OF SYMBOLS 10 Lithium ion battery 20 Function preparation apparatus 33 Memory | storage part 34 Control part 40 Function information 41 Measurement data 42 Characteristic data 43 Correction data 50 Acquisition part 51 Calculation part 52 1st specific part 53 2nd specific part 54 3rd specific part 55 Output part 60 Equivalent circuit 61 Power supply 62, 65, 67 Resistor 63, 64 RC circuit 66, 68 Capacitor 69 Terminal

Claims (7)

Obtain a function that shows the change in the electrical characteristic value of the circuit components that make up the internal resistance in an equivalent circuit that shows the secondary battery equivalent to the computer, by calculating the current value and the parameter,
Based on the characteristic data indicating the relationship between the open circuit voltage of the secondary battery and the charging rate, the current flowing through the terminal used for charging and discharging the power of the secondary battery is switched, the current, the voltage of the terminal, and An open circuit voltage of each time is obtained from a charge rate of each time of measurement data in which the charge rate of the secondary battery is measured every predetermined time, and an open circuit of a corresponding time is obtained from the voltage of the terminal of each time of the measurement data Subtract the voltage to calculate the voltage due to the internal resistance at each time,
The voltage of the internal resistance at each time calculated and the current value at each time of the measurement data set as the function to calculate the internal resistance at each time obtained from the electrical characteristic value of the circuit component. The value of the parameter that minimizes the error from the voltage is identified by analysis,
A function creation program characterized by causing a process to output information about a specific result to be executed. On the computer,
From the measurement data, the ratio of the voltage change with respect to the current change of the terminal by switching the current is obtained, and the parameter of the function indicating the change in the resistance value of the resistor that does not cause a transient change among the circuit components is obtained from the voltage change ratio. The function creating program according to claim 1 , further comprising executing a process of specifying a value. On the computer,
When the measurement data is measured by changing the current in a range where the absolute value is the same and the sign is different, the first terminal of the terminal immediately after switching the current from the calculated voltage due to the internal resistance at each time . after switching the voltage, the current, using an average of the subtracted value of the second voltage terminal at the time of a stable state to identify the initial value of the voltage of the circuit portion transient change occurs among the circuit components If the measurement data is not measured by changing the current in the range, a value obtained by subtracting the voltage drop due to the resistor that does not cause the transient change from the first voltage immediately after switching the current is used. And further executing a process of specifying an initial value of a voltage of a circuit part in which a transient change occurs among the circuit components ,
The process of specifying the parameter value specifies the parameter value by an analysis in which the specified initial value is set to an initial voltage value of a circuit portion in which a transient change occurs in the equivalent circuit. Item 3. The function creation program according to Item 2 . The measurement data is a plurality, different ranges of switching the current through each said terminal, any one of claims 1 to 3 in which the voltage of the terminal is characterized in that with those measured to stabilize Function creation program described in the section. Computer
Obtain the function that shows the change in the electrical characteristic value of the circuit component that constitutes the internal resistance in the equivalent circuit that equivalently shows the secondary battery, by calculating the current value and the parameter,
Based on the characteristic data indicating the relationship between the open circuit voltage of the secondary battery and the charging rate, the current flowing through the terminal used for charging and discharging the power of the secondary battery is switched, the current, the voltage of the terminal, and An open circuit voltage of each time is obtained from a charge rate of each time of measurement data in which the charge rate of the secondary battery is measured every predetermined time, and an open circuit of a corresponding time is obtained from the voltage of the terminal of each time of the measurement data Subtract the voltage to calculate the voltage due to the internal resistance at each time,
The voltage of the internal resistance at each time calculated and the current value at each time of the measurement data set as the function to calculate the internal resistance at each time obtained from the electrical characteristic value of the circuit component. The value of the parameter that minimizes the error from the voltage is identified by analysis,
A function creation method characterized by executing a process for outputting information on a specific result. An acquisition unit for acquiring a function indicating a change in an electrical characteristic value of a circuit component constituting an internal resistance in an equivalent circuit equivalently showing a secondary battery by calculating a current value and a parameter;
Based on the characteristic data indicating the relationship between the open circuit voltage of the secondary battery and the charging rate, the current flowing through the terminal used for charging and discharging the power of the secondary battery is switched, the current, the voltage of the terminal, and An open circuit voltage of each time is obtained from a charge rate of each time of measurement data in which the charge rate of the secondary battery is measured every predetermined time, and an open circuit of a corresponding time is obtained from the voltage of the terminal of each time of the measurement data A calculation unit that subtracts the voltage to calculate the voltage due to the internal resistance at each time;
For each time obtained from the electrical characteristic value of the circuit component calculated by setting the voltage of the internal resistance for each time calculated by the calculation unit and the current value for each time of the measurement data set to the function. A specifying unit that specifies by analysis the value of the parameter that minimizes an error from the voltage of the internal resistance ;
An output unit for outputting information on a specific result by the specific unit;
A function creation device characterized by comprising: On the computer
A function that shows a change in the electrical characteristic value of a circuit component that constitutes the internal resistance in an equivalent circuit that shows the secondary battery in an equivalent manner by calculating a current value and a parameter, and Based on the characteristic data indicating the relationship between the circuit voltage and the charging rate, the current flowing through the terminal used for charging and discharging the power of the secondary battery is switched to change the current, the voltage of the terminal, and the charging of the secondary battery. The open circuit voltage at each time is obtained from the charging rate at each time of the measurement data measured at predetermined time intervals, and the open circuit voltage at the corresponding time is subtracted from the voltage at each time terminal of the measurement data. Electrical characteristics of the circuit components calculated by calculating the voltage due to the internal resistance of time and setting the calculated voltage due to the internal resistance of each time and the current value of each time of the measurement data as the function Each calculated from the value Acquires the information of the function error of the voltage of the internal resistance is set is identified by analyzing the value of the parameter is minimized between,
A charge rate estimation program for executing a process of estimating a charge rate of the secondary battery using information of the acquired function.

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