Method and system for measuring current based on fusion of multiple measurement unit

Abstract

The present invention relates to a method for measuring a current by fusion based on multiple measuring units. The method includes: measuring, by a first measuring unit, a first sampled current value with respect to a current at a first sampling frequency, and measuring, by a second measuring unit, a second sampled current value with respect to the current at a second sampling frequency, the second sampling frequency being greater than or equal to the first sampling frequency (S1); and obtaining a measured current by fusing the first sampled current value and the second sampled current value in such a manner of: acquiring a base value of the measured current on the basis of the first sampled current value, and acquiring a dynamic response characteristic of the measured current on the basis of the second sampled current value (S2). The present invention further relates to a system for measuring a current by fusion based on multiple measuring units and a computer program product. According to the present invention, by fusing the high-accuracy measurement capability of the first measuring unit and the high dynamic responsiveness capability of the second measuring unit, highly demanding current measurements can be achieved with significantly reduced hardware costs of the measuring device.

Description

SPECIFICATIONMETHOD AND SYSTEM FOR MEASURING CURRENT BASED ON FUSION OF MULTIPLE MEASUREMENT UNITTECHNICAL FIELD

[0001] The present invention relates to the field of current measurement, and relates in particular to a method for measuring a current by fusion based on multiple measuring units, a system for measuring a current by fusion based on multiple measuring units, and a computer program product for at least assisting in implementing the steps of the method according to the present invention.BACKGROUND

[0002] During operation and maintenance of an electric vehicle, it is necessary to accurately measure a charging current or a discharging current of a power battery. In measuring the current of the battery by a measuring device, it is necessary to satisfy not only the accuracy requirement of each piece of sampled data but also the dynamic response speed requirement of battery current sampling. However, it is unlikely for a measuring device with a limited hardware budget to satisfy the requirements in both aspects at the same time. For example, the dynamic response capability of current measurement of a Hall sensor is strong, but the measurement accuracy thereof is unlikely to satisfy the requirement. The measurement accuracy of a shunt resistor is high, but the dynamic response capability of a shunt resistor having a low sampling frequency is unlikely to satisfy the requirement, and the hardware cost of a shunt resistor having a high sampling frequency is too high.

[0003] Therefore, how to accurately measure the current of the battery with a limited hardware budget has become a technical problem that needs to be solved currently.SUMMARY

[0004] An objective of the present invention is to provide a method for measuring a current by fusion based on multiple measuring units, a system for measuring a current by fusion based on multiple measuring units, and a computer program product, so as to at least partially solve the problems in the prior art.

[0005] According to a first aspect of the present invention, there is provided a method for measuring a current by fusion based on multiple measuring units. The method may comprise:- measuring, by a first measuring unit, a first sampled current value with respect to a current at a first sampling frequency fi, and measuring, by a second measuring unit, a second sampled current value with respect to the current at a second sampling frequency f2, wherein the second sampling frequency f2 is greater than or equal to the first sampling frequency fi; and- obtaining a measured current Im by fusing the first sampled current value and the second sampled current value in such a manner of: acquiring a base value of the measured current Im on the basis of the first sampled current value, and acquiring a dynamic response characteristic of the measured current lmon the basis of the second sampled current value.

[0006] The core concept of the present invention is as follows: By fusing the high-accuracy measurement capability of the first measuring unit and the high dynamic responsiveness capability of the second measuring unit, highly demanding current measurements can be achieved with significantly reduced hardware costs of the measuring device.

[0007] In an optional embodiment of the present invention, the current comprises a charging current or a discharging current of a battery, in particular, a charging current or a discharging current of a vehicle battery.

[0008] In another optional embodiment of the present invention, the first measuring unit may comprise a first shunt resistor and a first integrated chip sampling the current at the first sampling frequency fi ; and the second measuring unit may comprise a Hall sensor and a second integrated chip sampling the current at the second sampling frequency f2.

[0009] In another optional embodiment of the present invention, the first measuring unit may comprise a first shunt resistor and a first integrated chip sampling the current at the first sampling frequency fi , and the second measuring unit may comprise the first shunt resistor and a second integrated chip sampling the current at the second sampling frequency f2.

[0010] In another optional embodiment of the present invention, the first measuring unit may comprise a first shunt resistor and a first integrated chip sampling the current at the first sampling frequency fi ; and the second measuring unit may comprise a second shunt resistor and a second integrated chip sampling the current at the second sampling frequency f2.

[0011] In another optional embodiment of the present invention, first sampled current values in each fusion cycle may be averaged to obtain a first average current value in the corresponding fusion cycle, the first average current value being used as a base value of the measured current Im assigned to the corresponding fusion cycle.

[0012] In another optional embodiment of the present invention, the method may further comprise:- transmitting a measured current value from sampling the measured current Im obtained by fusion at a third sampling frequency fs.

[0013] In another optional embodiment of the present invention, the second sampling frequency f2 may in particular be an integer multiple of the first sampling frequency fi.

[0014] According to a second aspect of the present invention, there is provided a system for measuring a current by fusion based on multiple measuring units. The system is used to perform the method according to the present invention. The system may comprise the following components:- a first measuring unit configured to measure a first sampled current value with respect to a current at a first sampling frequency fi;- a second measuring unit configured to measure a second sampled current value with respect to the current at a second sampling frequency f2, wherein the second sampling frequency f2 is greater than or equal to the first sampling frequency fi; and- a fusion unit 13 configured to obtain a measured current by fusing the first sampled current value and the second sampled current value in such a manner of: acquiring a base value of the measured current on the basis of the first sampled current value, and acquiring a dynamic response characteristic of the measured current on the basis of the second sampled current value.

[0015] According to a third aspect of the present invention, there is provided a computer program product, such as a computer-readable program carrier, comprising or storing computer program instructions that, when executed by a processor, at least assist in implementing the steps of the method according to the present invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The principles, features, and advantages of the present invention can be better understood via further detailed description of the present invention provided with reference to the accompanying drawings. The accompanying drawings show:FIG. 1 shows a flowchart of a method for measuring a current by fusion based on multiple measuring units according to an exemplary embodiment of the present invention;FIG. 2 shows a schematic diagram of a system for measuring a current by fusion based on multiple measuring units according to an exemplary embodiment of the present invention;FIG. 3 shows a schematic diagram of a system for measuring a current by fusion based on multiple measuring units according to another exemplary embodiment of the present invention;FIG. 4 shows a schematic diagram of a system for measuring a current by fusion based on multiple measuring units according to another exemplary embodiment of the present invention;FIG. 5 shows a schematic diagram of a process of fusing current measurements according to an exemplary embodiment of the present invention; andFIG. 6 shows a flowchart of a method for measuring a current by fusion based on multiple measuring units according to another exemplary embodiment of the present invention.DETAILED DESCRIPTION

[0017] In order to make the technical problems to be solved by the present invention, the technical solutions, and the beneficial technical effects clearer, the present invention will be described below in further detail with reference to the accompanying drawings and a plurality of exemplary embodiments. It should be understood that the specific embodiments described herein are merely used to explain the present invention, but are not used to limit the scope of protection of the present invention.

[0018] FIG. 1 shows a flowchart of a method for measuring a current by fusion based on multiple measuring units according to an exemplary embodiment ofthe present invention. The following exemplary embodiments describe in further detail the method according to the present invention.

[0019] As shown in FIG. 1 , the method may include steps S1 and S2. In step S1 , a first sampled current value with respect to a current is measured at a first sampling frequency by a first measuring unit, and a second sampled current value with respect to the current is measured at a second sampling frequency by a second measuring unit, wherein the second sampling frequency is greater than or equal to the first sampling frequency. In the present embodiment of the present invention, the measured current may include a charging current or a discharging current of a battery, in particular, a charging current or a discharging current of a vehicle battery, and may optionally also include any other current in a measurement circuit. The current measured by the first measuring unit and the current measured by the second measuring unit are currents in the same current circuit. In view of the propagation speed of a current signal being close to the speed of light, it can be considered that the current measured by the first measuring unit and the current measured by the second measuring unit have equal amplitude and phase, with a negligible deviation.

[0020] In the schematic diagram of a system 1 for measuring a current by fusion based on multiple measuring units according to an exemplary embodiment of the present invention shown in FIG. 2, a charging current or a discharging current of a battery 10 flows in a current measurement circuit. The first measuring unit 11 includes, for example, a first shunt resistor 111 and a first integrated chip 112 sampling the current at a first sampling frequency fi . The first shunt resistor 111 is connected in series with the battery measurement circuit, and the resistance of the first shunt resistor 111 is accurately known. In the sampling process of the shunt resistor, a voltage generated on the first shunt resistor 111 by the current of the battery is measured every preset time period. Thus, the current of the battery flowing through the shunt resistor can be determined according to Ohm's law, thereby obtaining a first sampledcurrent value for the current of the battery. It should be noted that, although the measurement accuracy of a shunt resistor is high, the dynamic response capability of a shunt resistor performing current sampling at a low sampling frequency is poor, and the hardware cost of equipping a shunt resistor with an integrated chip having a high sampling frequency is extremely high.

[0021] The second measuring unit 12 includes, for example, a Hall sensor 121 and a second integrated chip 122 sampling the current at a second sampling frequency f2. By measuring a change in magnetic field on the basis of the Hall effect, the Hall sensor 121 can determine a current causing the change in magnetic field. Compared with the shunt resistor, the Hall sensor has a lower hardware cost and a smaller footprint, while also having a stronger dynamic response capability, i.e. , it is capable of responding quickly to current changes and performing following measurement, but its measurement accuracy is poorer. It should be noted that the second integrated chip 122 adapted to the Hall sensor 121 may generally be integrated into a fusion unit 13 of the system 1 , and the fusion unit 13 may in particular be integrated into a control module of a battery management system, rather than being present as a separate hardware module.

[0022] In the schematic diagram of the system 1 according to another exemplary embodiment of the present invention shown in FIG. 3, the first measuring unit 11 includes, for example, a first shunt resistor 111 and a first integrated chip 112 sampling the current at the first sampling frequency fi, and the second measuring unit 12 includes, for example, a second shunt resistor 123 and a second integrated chip 122 sampling the current at the second sampling frequency f2. Here, the first measuring unit 11 and the second measuring unit 12 may measure currents in the same measurement circuit using different shunt resistors, and perform current sampling at different sampling frequencies using different integrated chips, respectively. Likewise, the second sampling frequency f2 may in particular be an integer multiple of the first sampling frequency fi.

[0023] In the schematic diagram of the system 1 according to an exemplary embodiment of the present invention shown in FIG. 4, the first measuring unit 11 includes, for example, a first shunt resistor 111 and a first integrated chip 112 sampling the current at the first sampling frequency fi, and the second measuring unit 12 includes the first shunt resistor 111 and a second integrated chip 122 sampling the current at the second sampling frequency f2. Here, the first measuring unit 11 and the second measuring unit 12 may measure exactly the same current using the same shunt resistor, thus further saving the hardware cost of the measuring device, but perform current sampling at different sampling frequencies using different integrated chips, respectively. The second sampling frequency f2 may in particular be an integer multiple of the first sampling frequency fi. Since the same shunt resistor is used, the first measuring unit 11 and the second measuring unit 12 are not labeled in FIG. 4 for clarity.

[0024] In step S2, a measured current is obtained by fusing the first sampled current value and the second sampled current value in such a manner of: acquiring a base value of the measured current on the basis of the first sampled current value, and acquiring a dynamic response characteristic of the measured current on the basis of the second sampled current value. A measured current fusion process based on multiple measuring units will be set forth in detail below in connection with different embodiments.

[0025] For example, in the embodiments of the current measurement circuits shown in FIGS. 2 to 4, the first sampled current value is sent by the first integrated chip 112 to the fusion unit 13, and the second sampled current value is sent by the second integrated chip 122 to the fusion unit 13. In consideration of the limitations with respect to the data transfer rate and / or the data reliability between the integrated chips and the fusion unit 13, the sampled current values need to be internally integrated in the integrated chips before being transmitted to the fusion unit 13. It should be noted that the integrated chipadapted to the Hall sensor may in particular be integrated into the fusion unit 13. Therefore, the internal integration of the sampled current values of the Hall sensor may also be performed in the fusion unit 13.

[0026] In the schematic diagram of a process of fusing current measurements according to an exemplary embodiment of the present invention shown in FIG. 5, the current labeled with a solid line schematically represents a change process of an actual current IR in the measurement circuit over time T. The first measuring unit 11 includes, for example, a first shunt resistor 111 and an adapted first integrated chip 112, and samples the actual current IR at the first sampling frequency fi by means of the first integrated chip 112. For example, the actual current IR may be sampled every 1 ms by the first integrated chip 112 having a measurement frequency of 1 kHz, but due to the limitation of the data transmission rate of the integrated chip (the cost of the chip increases greatly as the data transmission rate increases), all sampled data in a time interval are usually internally integrated before being sent as the first sampled current value. For example, 100 pieces of sampled data in a time interval of 100 ms are averaged to obtain the first sampled current value assigned to the time interval and sent, that is, one sampled current value is sent every 100 ms. Therefore, the first sampling frequency fi of the first integrated chip 112 is 10 Hz. For example, in the lower half of FIG. 5, the first sampled current values in a first fusion cycle Ti may be averaged to obtain a first average current value T of the first fusion cycle Ti. The first average current value 1 i is usedas abase value of the measured current assigned to the first fusion cycle Ti. The first sampled current values in a second fusion cycle T2 may be averaged to obtain a first average current value T 7 of the second fusion cycle T2. For simplification, a fusion cycle of 100 ms is set, for example, and the first sampled current value of the first integrated chip 112 having the first sampling frequency fi of 10 Hz in one fusion cycle is the first average current value in the fusion cycle. It can be understood that the sampling frequency of the first measuring unit 11 is low but the measurement accuracy is high, that is, the first sampled current values are subject to less interference factors and themeasurement result is accurate. Therefore, the obtained first average current value is suitable as a base value of the measured current.

[0027] In the upper half of FIG. 5, the current labeled with a solid line likewise schematically represents a change process of the actual current IR in the measurement circuit over time T. Here, the actual current IR is sampled by the second measuring unit 12 at the second sampling frequency f2, wherein the second sampling frequency f2 is greater than or equal to the first sampling frequency fi . The second sampling frequency f2 may in particular be an integer multiple of the first sampling frequency fi . The second measuring unit 12 may include a Hall sensor 121 and an adapted second integrated chip 122, and may also include a shunt resistor and an adapted second integrated chip. It should be noted that, likewise, due to the limitation of the data transmission rate of the integrated chip, all sampled data in a time interval also needs to be internally integrated before the second sampled current value is sent. However, since the second sampling frequency f2 is greater than or equal to the first sampling frequency fi , the frequency of sending the second sampled current value by the second integrated chip may be higher than that of sending the first sampled current value by the first integrated chip. For example, for the second integrated chip having the second sampling frequency f2 of 50 Hz, sampled data in a time interval of 20 ms is averaged to obtain the second sampled current value assigned to the time interval and sent, that is, one second sampled current value is sent every 20 ms. As shown in the upper half of FIG. 5, 5 second sampled current values, which are indicated by solid circles, may be sent by the measuring unit 12 in one fusion cycle of 100 ms.

[0028] It should be noted that, in the case where the second sampling frequency f2 is an integer multiple of the first sampling frequency fi, the fusion cycle may be determined to be an integer multiple of the second sampling cycle of the second integrated chip, so as to save the computing power for performing data fusion. In the case where the second sampling frequency f2 is not an integer multiple of the first sampling frequency fi, the fusion cycle mayalso be determined to be the least common multiple of the first sampling cycle of the first integrated chip and the second sampling cycle of the second integrated chip.

[0029] Here, the second sampled current values in the first fusion cycle Ti are averaged to obtain a second average current valuein the first fusion cycle Ti . In addition, a difference current AI22between a second sampled current value I22 in a second fusion cycle T2 following the first fusion cycle Ti and the second average current valueis obtained. The obtained difference current is used as a dynamic response characteristic of the measured current Im assigned to the second fusion cycle T2. For example, for the first sampled current value I221 acquired by the second measuring unit 12 in the second fusion cycle T2, a difference current AI22I between the first sampled current value I221 and the second average current valueof the first fusion cycle Ti may be obtained; for the second sampled current value I222 acquired by the second measuring unit 12 in the second fusion cycle T2, a difference current AI222between the second sampled current value I222 and the second average current valueof the first fusion cycle Ti may be obtained; and so on. It can be understood that, since the sampling frequency of the second measuring unit 12 is high, the difference current can more accurately reflect the change process of the measured current Im over time. However, the measurement accuracy of the second measuring unit 12 is low. As shown in the upper half of FIG. 5, the second sampled current values have a large deviation from the actual current IR, and thus is suitable for characterizing the dynamic response characteristic of the measured current lm.

[0030] In the sense of the present invention, the base value may be understood as a current starting value or a current average value of the measured current in the corresponding fusion cycle, and a fused measured current value can be obtained by superimposing the dynamic response characteristic value of the measured current on the base value. For example, in the lower half of FIG. 5,for the second fusion cycle T2, the first average current value IX1of the first fusion cycle T1 is used as the base value of the measured current Im assigned to the second fusion cycle T2. In the embodiment of FIG. 5, the base value is used, for example, as the current starting value of the measured current in the second fusion cycle T2. On the base value, the obtained difference current AI22between the second sampled current value I22 in the second fusion cycle T2 and the second average current valueis superimposed as the dynamic response characteristic of the measured current Im assigned to the second fusion cycle T2, thus obtaining a fusion result of the measured current lm(schematically shown here by a dash-double-dot line) in the second fusion cycle T2. For example, in the second fusion cycle T2, a first fusion current value Im2i of the second fusion cycle T2 may be obtained by superimposing the difference current AI22I on the first average current valueasecond fusion current value Im22 of the second fusion cycle T2 may be obtained by superimposing the difference current AI222on the first average current value T 7, and so on, thus obtaining fusion current values of the second fusion cycle T2, which are labeled with hollow circles in the lower half of FIG. 5. The measured current lmmay be obtained by fitting these hollow circles. It can be seen from the lower half of FIG. 5 that the measured current lmand the actual current IR have a certain deviation since the first average current value of the previous fusion cycle, instead of the instantaneous current value at the end of the previous fusion cycle, is used as the current starting value of the current fusion cycle for superimposition in the fusion process. In view of high uncertainty of the measurement result of the instantaneous current value at the end of the fusion cycle, the fusion method according to the present invention is intended to eliminate such uncertainty, while the deviation is limited to an acceptable range in the actual measurement process. It should be noted that, in the fusion process, other current values may be superimposed to obtain the fusion current, as long as it conforms to the basic concept of the present invention.

[0031] According to the embodiments of the present invention, by fusing the high-accuracy measurement capability of the first measuring unit and the high dynamic responsiveness capability of the second measuring unit, highly demanding current measurements can be achieved with significantly reduced hardware costs of the measuring device.

[0032] FIG. 6 shows a flowchart according to another exemplary embodiment of the present invention. Only differences from the embodiment shown in FIG. 1 are described below, and for brevity, the same steps will not be described again.

[0033] The method may further include step S3. In step S3, a measured current value from sampling the measured current Im obtained by fusion at a third sampling frequency fs is transmitted. Here, the fusion unit 13 may in particular be integrated into a control module of a battery management system and transmit the measured current value obtained by fusion to a vehicle control unit by means of a vehicle data transmission protocol (e.g., a CAN bus protocol). In consideration of the limitations of the vehicle data transmission protocol with respect to the data transmission rate and / or the data reliability, here, the measured current Im obtained by fusion may be sampled in the fusion unit 13 at a third sampling frequency fs (e.g., 50 Hz), and the sampled measured current value may be transmitted via the vehicle data transmission protocol.

[0034] In addition, it should be noted that the step number described herein does not necessarily represent an order, but is merely a reference numeral. The order may be changed according to a specific situation, so long as the technical objective of the present invention can be achieved.

[0035] It should be understood that the expressions "first", "second", "third", etc. are used herein for descriptive purposes only, and are not to be understood as indicating or implying relative importance, nor as implicitly indicating the number of technical features indicated. A feature defined by"first", "second", or "third" may explicitly or implicitly mean that at least one such feature is included.

[0036] Although particular embodiments of the present invention are described in detail herein, the particular embodiments are merely for the purpose of explanation, and should not be considered to limit the scope of the present invention. Various replacement schemes and modification schemes may be provided without departing from the core and scope of the present invention.

Claims

CLAIMS1. A method for measuring a current by fusion based on multiple measuring units, the method comprising: measuring, by a first measuring unit (11 ), a first sampled current value with respect to a current at a first sampling frequency (fi), and measuring, by a second measuring unit (12), a second sampled current value with respect to the current at a second sampling frequency (f2), wherein the second sampling frequency (f2) is greater than or equal to the first sampling frequency (fi); and obtaining a measured current (Im) by fusing the first sampled current value and the second sampled current value in such a manner of: acquiring a base value of the measured current (Im) on the basis of the first sampled current value, and acquiring a dynamic response characteristic of the measured current (lm) on the basis of the second sampled current value.

2. The method according to claim 1 , wherein the current comprises a charging current or a discharging current of a battery, in particular, a charging current or a discharging current of a vehicle battery.

3. The method according to any one of the preceding claims, wherein the first measuring unit (11 ) comprises a first shunt resistor (111 ) and a first integrated chip (112) sampling the current at the first sampling frequency (fi), and the second measuring unit (12) comprises a Hall sensor (121 ) and a second integrated chip (122) sampling the current at the second sampling frequency (f2).

4. The method according to any one of the preceding claims, wherein the first measuring unit (11 ) comprises a first shunt resistor (111 ) and a first integrated chip (112) sampling the current at the first sampling frequency (fi), and the second measuring unit (12) comprises the first shunt resistor (111 ) and a second integrated chip (122) sampling the current at the second sampling frequency (f2).

5. The method according to any one of the preceding claims, wherein the first measuring unit (11 ) comprises a first shunt resistor (111 ) and a first integrated chip (112) sampling the current at the first sampling frequency (fi ), and the second measuring unit (12) comprises a second shunt resistor (123) and a second integrated chip (122) sampling the current at the second sampling frequency (f2).

6. The method according to any one of the preceding claims, wherein first sampled current values in each fusion cycle (Ti , T2) are averaged to obtain a first average current value (T 7, W in the corresponding fusion cycle (T1 , T2), the first average current value (T 7, kJ) being used as a base value of the measured current (Im) assigned to the corresponding fusion cycle (T1 , T2).

7. The method according to any one of the preceding claims, further comprising: transmitting a measured current value from sampling the measured current (Im) obtained by fusion at a third sampling frequency (fs).

8. The method according to any one of the preceding claims, wherein the second sampling frequency (f2) is an integer multiple of the first sampling frequency (fi).

9. A system (1 ) for measuring a current by fusion based on multiple measuring units, the system (1 ) being used to perform the method according to any one of the preceding claims, wherein the system (1 ) comprises the following components: a first measuring unit (11 ) configured to measure a first sampled current value with respect to a current at a first sampling frequency (fi); a second measuring unit (12) configured to measure a second sampled current value with respect to the current at a second sampling frequency (f2),wherein the second sampling frequency (f2) is greater than or equal to the first sampling frequency (fi); and a fusion unit (13) configured to obtain a measured current by fusing the first sampled current value and the second sampled current value in such a manner of: acquiring a base value of the measured current on the basis of the first sampled current value, and acquiring a dynamic response characteristic of the measured current on the basis of the second sampled current value.

10. A computer program product, such as a computer-readable program carrier, comprising or storing computer program instructions that, when executed by a processor, at least assist in implementing the steps of the method according to any one of claims 1 to 8.

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