Battery data transmission device, battery management device, battery data transmission method, battery data transmission system

Abstract

To allow information transmission to be maintained even in situations where transmission errors occur.SOLUTION: A battery data transmission device detects states of a plurality of battery cells and transmits battery data, which is data relating to the detected plurality of battery cells, via a transmission path. The battery data transmission device includes: an encoding unit that has a plurality of encoding modes and encodes the battery data into encoded data; a mode selection unit that selects any one encoding mode from the plurality of encoding modes; and a transmission control unit that transmits the encoded data of the encoding mode selected by the mode selection unit to a battery management device, and receives reception information on the transmitted data from the battery management device. The mode selection unit selects an encoding mode that does not use past battery data during decoding as an encoding mode for transmission this time when communication of previous transmission data is abnormal, according to the reception information from the battery management device.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a battery data transmission device, a battery management device, a battery data transmission method, and a battery data transmission system.

Background Art

[0002] In a battery system used in a hybrid vehicle, an electric vehicle, or the like, a battery pack configured by connecting a large number of single battery cells of a secondary battery in series is used. In such a battery pack, for the capacity calculation and protection management of each single battery cell, the single battery cell is managed using a monitoring IC that monitors the state of the single battery cell and a control IC that controls the charge and discharge state of the single battery cell. Although a wired connection is the mainstream between the monitoring IC and the control IC, for various reasons such as weight reduction, cost reduction, expansion of in-vehicle space, improvement of layout freedom, and reduction of short-circuit risk during a collision by reducing the connection cable (communication harness), the application of wireless communication has been studied. On the other hand, the monitoring and control of the battery cell are performed at very short intervals (tens of ms to 100 ms), and robust communication is required. However, the inside of the vehicle is subject to various disturbances such as various metals, high currents, wireless communication of passengers and the vicinity, and the communication quality deteriorates. Patent Document 1 discloses a method for compressing and decompressing battery data in which current values and voltage values at each time of a battery are paired and data is stored. When compressing the data, a predicted value of the current change amount this time is calculated using the change amount of the voltage value between the previous time and this time, a difference between the predicted value of the current change amount this time and the actual change amount of the current value this time is calculated, and this difference is stored as data. When decompressing the data, a predicted value of the current change amount this time is calculated using the change amount of the voltage value between the previous time and this time, and the difference between the predicted value of the current change amount this time and the actual current value this time is added to the predicted value of the current change amount this time to calculate the change amount of the current value this time.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the invention described in Patent Document 1, there is room for improvement in countermeasures against transmission errors.

Means for Solving the Problems

[0005] A battery data transmission device according to a first aspect of the present invention is a battery data transmission device that detects the states of a plurality of battery cells and transmits battery data, which is data regarding the plurality of detected battery cells, via a transmission line. The battery data transmission device includes a plurality of encoding modes, an encoding unit that encodes the battery data into encoded data, a mode selection unit that selects any one of the plurality of encoding modes, and a transmission control unit that transmits the encoded data of the encoding mode selected by the mode selection unit to a battery management device and receives reception information of the transmitted data from the battery management device. The mode selection unit selects, according to the reception information from the battery management device, an encoding mode that does not use past battery data at the time of decoding as the encoding mode to be transmitted this time when the communication of the previous transmission data is abnormal. A battery management device according to a second aspect of the present invention includes a transmission control unit that communicates with a battery data transmission device that wirelessly transmits encoded data obtained by encoding battery data, a decoding unit that decodes the encoded data to obtain the battery data, an abnormality detection unit that detects an abnormality in the encoded data received by the transmission control unit or an abnormality when decoding the encoded data by the decoding unit, and a command unit that outputs a command to select, as the encoding mode to be transmitted next time, an encoding mode that does not use past battery data at the time of decoding to the battery data transmission device when the abnormality detection unit detects an abnormality. The battery data transmission method according to the third aspect of the present invention is a battery data transmission method for detecting the states of a plurality of battery cells and transmitting battery data, which is data regarding the plurality of detected battery cells, via a transmission line. The method includes a data encoding process for encoding the battery data using any one of a plurality of encoding modes, an encoding mode selection process for selecting any one encoding mode from the plurality of encoding modes, and a data transmission / reception process for transmitting the encoded data of the encoding mode selected by the encoding mode selection process to a battery management device and receiving reception information of the transmitted data from the battery management device. In the encoding mode selection process, when the communication of the previous transmission data is abnormal according to the reception information from the battery management device, an encoding mode that does not use past battery data at the time of decoding is selected as the encoding mode to be transmitted this time. The battery data transmission system according to the fourth aspect of the present invention is a battery data transmission system including a battery data transmission device that transmits encoded data obtained by encoding battery data, which is data regarding a battery, via a transmission line, and a battery management device that receives the encoded data. The system includes an abnormality detection unit for detecting an abnormality in the encoded data. The battery data transmission device includes an encoding unit that generates the encoded data using the battery data and a transmission control unit that transmits the encoded data to the battery management device via the transmission line. The encoding unit has at least a first mode and a second mode as operation modes. The first mode is a mode for generating the encoded data using past battery data, and the second mode is a mode for generating the encoded data without using past battery data. When the abnormality detection unit detects an abnormality in the encoded data, the second mode is applied to the encoding unit at the time of the next encoding.

Advantages of the Invention

[0006] According to the present invention, in data encoding for transmitting battery information, the encoding method is changed between normal and abnormal times, and information transmission can be maintained even in a situation where a transmission error occurs.

Brief Description of the Drawings

[0007]

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Mode for Carrying Out the Invention

[0008] ―Embodiment― (Overview) When transmitting battery data, there is a method in which the battery data is compressed by encoding on the transmission side, transmitted wirelessly, and then the data received by the receiving device is decompressed by decoding. When transmitting data in this compressed manner, the wireless transmission band can be effectively utilized. Even if data errors, that is, errors occur due to the influence of transmission noise or the like, there is an advantage that the opportunity to retransmit the same data multiple times during the gap time increases. Also, compared with the case where data is not compressed, since the amount of data transmitted per unit time decreases, there is an advantage that the probability of data errors occurring can be relatively reduced. On the other hand, it is generally known that if there is an error in the received data, the data before compression may not be correctly decoded in some cases.

[0009] As will be described later, according to the driving patterns of an automobile, such as stopping, constant-speed driving, acceleration, deceleration, etc., characteristic time-series changes appear in the battery data, and the optimal data compression method is different. Therefore, in this embodiment, the data is compressed in advance by a plurality of data compression methods, and the data that can be compressed most efficiently is transmitted. Also, a method for preventing the influence of incorrect decoding due to data errors from propagating into the future will be described together.

[0010] Hereinafter, an embodiment of the battery data transmission system will be described with reference to FIGS. 1 to 13.

[0011] (Overall Configuration) FIG. 1 is an overall configuration diagram of a battery data transmission system S1 in an embodiment. The battery data transmission system S1 includes a motor 11, an inverter 12, a current sensor 13, a plurality of cell groups CG, a plurality of battery data transmission devices B, a battery management device M, and a host controller 20. The plurality of battery data transmission devices B are numbered to distinguish each of them. Hereinafter, the entire plurality of cell groups CG and the individual cells included in each cell group CG are also referred to as "batteries".

[0012] The battery data transmission device B includes a cell controller 14, a transmission control unit 15, and an encoding unit 16. The configurations and operations of the respective battery data transmission devices B are the same. Hereinafter, in order to explain the specific operations, the battery data transmission device B1 may be used for explanation. That is, hereinafter, the configuration of the battery data transmission device B1, namely, the cell controller 14-1, the transmission control unit 15-1, and the encoding unit 16-1 may be used for explanation.

[0013] The battery management device M includes a transmission control unit 15-z, a decoding unit 17, an abnormality detection unit 18, and a battery control instruction unit 19. The transmission control units 15-1, 15-n, etc., which are transmission control units included in the battery data transmission device B, and the transmission control unit 15-z included in the battery management device M are respectively connected by a transmission path T. The transmission path T is a space for wireless communication, and the transmission control unit 15 performs wireless communication.

[0014] The inverter 12 supplies the power stored in the cell group CG to the motor 11, or accumulates the power obtained from the motor 11 in the cell group CG. The current sensor 13 measures the current flowing between the inverter 12 and the cell group CG and transmits it to the battery control instruction unit 19.

[0015] The cell controller 14, the encoding unit 16, the decoding unit 17, the abnormality detection unit 18, and the battery control instruction unit 19 are, for example, any one of a computer, an FPGA (Field Programmable Gate Array), and an ASIC (Application Specific Integrated Circuit) which is an integrated circuit for specific use. The computer includes a CPU which is a central processing unit, a ROM which is a read-only storage device, and a RAM which is a readable and writable storage device, and the CPU expands and executes the program stored in the ROM in the RAM to perform various operations.

[0016] The cell controller 14 controls a cell group CG formed by a plurality of cells. The cell controller 14 performs the control specified by the battery management device M via the transmission line T. The cell controller 14 includes at least a voltmeter and measures the voltage of each cell. The cell controller 14 may include other sensors, for example, the temperature of each cell may also be measured. The cell controller 14 may calculate the state of charge (SoC) of each battery. When the cell controller 14 receives a request command described later from the battery management device M, it transmits the information of the connected cell group. The request command includes the designation of an encoding mode, and the cell controller 14 outputs the information of the designated encoding mode and the information of the cell group CG to the encoding unit 16.

[0017] The transmission control units 15-1 and 15-n included in the battery data transmission device B transmit the information encoded by the encoding unit 16 to the battery management device M. Also, the transmission control units 15-1 and 15-n output the information received from the battery management device M to the cell controller 14. The transmission control unit 15-z included in the battery management device M outputs the information received from the battery data transmission device B to the decoding unit 17. The transmission control unit 15 is a communication module.

[0018] The symbolization unit 16 encodes the information of the cell group CG output by the cell controller 14 in a specified encoding mode and outputs it to the transmission control unit 15. The encoding unit 16 has a plurality of encoding modes and operates in the encoding mode specified by the cell controller 14. The decoding unit 17 decodes the information of the cell group CG received from the battery data transmission device B and outputs it to the abnormality detection unit 18 and the battery control instruction unit 19. The details of the encoding unit 16 will be described later.

[0019] The abnormality detection unit 18 detects an abnormality occurring in the transmission path T. The details of the abnormality detection will be described later. The battery control instruction unit 19 controls the charging and discharging of the battery, that is, the cell group CG, according to the instructions of the upper controller 20. Also, the battery control instruction unit 19 transmits to the upper controller 20 whether the battery is in a normal state or not. The battery control instruction unit 19 transmits a request command for requesting the transmission of battery data to each cell controller 14 every time a predetermined time, for example, 20 ms, elapses. This request command includes information specifying the encoding mode. The cell controller 14 acquires the battery data and obtains encoded data by encoding the battery data in the specified mode. Then, the cell controller 14 transmits this encoded data to the battery management device M. The mode may be the same for all cell controllers or may be changed for each cell controller.

[0020] (Abnormality Detection Unit) The abnormality detection unit 18 detects an abnormality in the transmission path T using data errors or non-reception of data. As data errors, block codes such as existing error detection codes and Reed-Solomon codes, convolutional codes, concatenated codes, and other error correction codes, detection of undecodable data, etc. may be used. Also, non-reception of data detects that data transmitted periodically cannot be received within a predetermined time interval. Each will be described below.

[0021] When detecting an abnormality using an existing error detection method, for example, CRC error, the abnormality detection unit 18 calculates the CRC (Cyclic Redundancy Check) of the data received from the battery data transmission device B, and determines that an abnormality has occurred in the transmission path T when a CRC error occurs. Also, when an irreparable error that exceeds the error correction ability of an existing error correction method, for example, Reed - Solomon code, is detected, it is determined that an abnormality has occurred in the transmission path T. Further, when detecting undecodable data such as undefined symbols when decoding data encoded using an entropy code such as the Huffman code described later, it is determined that an abnormality has occurred in the transmission path T.

[0022] In the configuration shown in FIG. 1, the abnormality detection unit 18 is arranged after the decoding unit 17, but the abnormality detection unit 18 may be arranged before the decoding unit 17. In this case, for example, when an irreparable error is detected using the above - mentioned error detection method or error correction method, or when the received data does not reach a predetermined code length, etc., it is possible to detect that the data is undecodable before decoding.

[0023] (Encoding mode) The encoding mode includes two modes: a normal mode and an abnormal mode. The operations of each typical mode will be described below. The information of the cell transmitted by the cell controller 14 is not limited to voltage information, but for simplicity of description here, only the transmission of voltage will be described. Hereinafter, the normal mode may also be referred to as the "first mode", and the abnormal mode may be referred to as the "second mode".

[0024] In the normal mode, the encoding unit 16 of the cell controller 14 specified to operate may use, as encoded data, an enumeration of the latest values of the voltages of each cell, or the differences from past measurement values, or the differences from a reference cell within the cell group CG. Further, instead of using the numerical values as they are as encoded data, the cell controller 14 may use encoded data obtained by variable-length encoding using known entropy. Variable-length encoding is, for example, Huffman encoding or context-adaptive encoding (such as CAVLC or CABAC). When performing encoding based on a pre-created table such as Huffman encoding, it can be said that the encoding unit 16 performs a compression process of compressing the battery data into encoded data with a data length equal to or less than that of the original data. The details of the operation of the encoding unit 16 in this normal mode will be described later.

[0025] In the abnormal mode, the encoding unit 16 of the cell controller 14 specified to operate performs encoding excluding the encoding method that uses the differences from past measurement values as encoded data among the encoding methods in the normal mode described above. The reason for excluding the encoding method that uses the differences from past measurement values as encoded data and the details of the operation of the encoding unit 16 in the abnormal mode will be described later.

[0026] (Transmission data) FIG. 2 is a schematic diagram showing the transmission data transmitted by the transmission control unit 15 of the battery data transmission device B in the normal mode and the abnormal mode. In any mode, the communication header FH is included at the head of the transmission data. The communication header FH is information indicating the destination of the transmission data, such as an IP address or a CAN-ID. Following the communication header FH, there may be a case where uncompressed data FNC is stored, or a case where an encoding header FCH and compressed data FCD are included.

[0027] The uncompressed data FNC is the arrangement of battery data without compression. For example, the digital data (V1(t), V2(t), V3(t), …, Vn(t)) of the voltage values of n (where n is a positive integer) cells belonging to the cell group CG are described in order from cell #1 to cell #n as integer values in millivolts. Note that the "t" in this parentheses is a symbol representing the time series order of the battery data, and its details will be described later.

[0028] The encoded header FCH is information necessary to decode the compressed data FCD, and includes a flag FCF for distinguishing the encoded header FCH from the uncompressed data FNC, mode information FCM indicating the compression method, the code length FCL, and the like. The flag FCF is, for example, 1-bit information having a value of "1", and if the uncompressed data FNC always has a value of "0" as the leading bit, the encoded header FCH and the uncompressed data FNC can be distinguished. The mode information FCM is information for identifying which of the encoding methods described later was used for encoding.

[0029] The code length FCL is information indicating the length of the compressed data FCD, that is, the number of bits, the number of bytes, etc., and may include the length of the encoded header FCH. Note that instead of this code length FCL, a code indicating the end of the data may be added to the end of the compressed data FCD described below. Also, when decoding the compressed data FCD, if it is possible to identify the end of the compressed data FCD by comparing the number of cells belonging to the predetermined cell group CG (n) with the number of data (V1(t), V2(t), V3(t), …, Vn(t)) obtained in the decoding process, the code length FCL may be omitted.

[0030] The compressed data FCD is the encoded battery data and may be fixed-length data or variable-length data. The details of this compressed data FCD will be described later. However, the length of the data mentioned here is the size of the data in the application layer of the OSI reference model, and is not the size of each packet in the second and third layers of the OSI reference model.

[0031] (Flowchart) Figure 3 is a flowchart showing the operation of the battery management device M. The battery management device M executes the process shown in Figure 3 every time a predetermined time, for example, 20 ms, has elapsed. Note that Figure 3 explains the transmission and reception of data between the battery management device M and one battery data transmission device B. The battery management device M executes the process shown in Figure 3 for the number of battery data transmission devices B included in the battery data transmission system S1.

[0032] In step S301, the battery control instruction unit 19 generates a request command for a specific battery data transmission device B and transmits it using the transmission control unit 15. The battery data transmission device B that has received the request command transmits battery data to the battery control instruction unit 19 according to the flowchart of Figure 4 described later. In the subsequent step S302, the battery control instruction unit 19 receives encoded data from the battery data transmission device B.

[0033] In the subsequent step S303, the battery control instruction unit 19 determines in the above-mentioned abnormality detection unit 18 whether the received encoded data is normal. If it is normal, the process proceeds to step S304, and the encoded data is decoded using the decoding unit 17. On the other hand, if it is determined in step S303 that the encoded data is abnormal, the process proceeds to step S307. In this step S303, for example, when an irreparable data error is detected using the above-mentioned error detection method or error correction method, or when the code length FCL shown in Figure 2(b) does not match the code length of the actually received encoded data, it is determined as abnormal. Note that the details of the decoding method in step S304 will be described later.

[0034] In step S305, the above-described abnormality detection unit 18 determines whether the decoded data is normal. If it is normal, the process proceeds to step S306. On the other hand, if it is determined in step S305 that the decoded data is abnormal, the process proceeds to step S307. In this step S305, for example, when detecting undecodable data such as undefined symbols when decoding the data encoded using the entropy code in step S304, it is determined as abnormal.

[0035] In step S306, the battery control instruction unit 19 sets a normal response, so-called Ack, which is a response indicating normality, as a control command to be transmitted in step S309 described later or as part of the control command. In step S307, the battery control instruction unit 19 sets an abnormal response, so-called Nak, which is a response indicating abnormality, as a control command to be transmitted in step S309 described later or as part of the control command. In step S308, the battery control instruction unit 19 estimates the battery state.

[0036] In step S309 following step S308 and step S307, the battery control instruction unit 19 transmits a control command including a normal response or an abnormal response to the battery data transmission device B, and ends the process shown in FIG. 3. Note that the control command may include forced discharge control (balancing) for preventing overcharging of the battery, battery forced cut-off control when detecting an abnormal voltage or abnormal temperature of the battery, and the like.

[0037] As described above, in step S309, when the abnormality detection unit 18 immediately detects an abnormality in the transmission path T, the battery control instruction unit 19 transmits an abnormal response (Nak) including a command to set the next encoding mode to the abnormal mode to the battery data transmission device B. The command to set the next encoding mode to the abnormal mode can also be said to be a command to set the next encoding method to a mode that does not use past data for decoding. Therefore, it can also be said that the battery control instruction unit 19 has a role as a "command unit" that outputs a command to set the next encoding method to a mode that does not use past data for decoding.

[0038] Although not shown in FIG. 3, when sensor data cannot be obtained from the battery data transmission device B, the upper controller 20 may be notified that an abnormality has occurred in the battery of the battery data transmission system S1.

[0039] FIG. 4 is a flowchart showing the operation of the battery data transmission device B. When the battery data transmission device B is activated, it performs the operation shown in FIG. 4, and when the operation shown in FIG. 4 is completed, it performs the operation shown in FIG. 4 again. That is, the battery data transmission device B repeatedly executes the operation shown in FIG. 4.

[0040] In step S401, the battery data transmission device B waits for reception of a request command from the battery data transmission device B, and when received, proceeds to step S402. The request command received in this step is transmitted in step S301 of FIG. 3. In the subsequent step S402, the cell controller 14 performs battery data observation, that is, acquires battery information.

[0041] In the subsequent step S403, the cell controller 14 designates an encoding mode to the encoding unit 16 to cause it to encode the battery data. The encoding mode designated by the cell controller 14 in this step is the normal mode in the initial state such as immediately after power-on or immediately after system reset, and thereafter, it is either the normal mode or the abnormal mode designated in step S406 according to the control command received in step S405 described later.

[0042] In the subsequent step S404, the transmission control unit 15 transmits the encoded data, which is the battery data encoded by the encoding unit 16, to the battery management device M. This encoded data is received in step S302 of FIG. 3.

[0043] In the subsequent step S405, the transmission control unit 15 receives the control command transmitted from the battery management device M. The control command received in this step is transmitted in step S309 of FIG. 3. As described above, this control command includes a normal response when data can be normally decoded in the battery management device M, and includes an abnormal response when data cannot be normally decoded in the battery management device M. Further, if the control command cannot be received within a predetermined time due to an abnormality in the transmission line T or the like, it is determined as no response and the process proceeds to step S406.

[0044] In the subsequent step S406, when the control command received in step S405 includes a normal response (Ack), the transmission control unit 15 sets the encoding mode of the encoding unit 16 to the normal mode when executing step S403 next time. On the other hand, when the control command received in step S405 includes an abnormal response (Nak) or no response, the transmission control unit 15 sets the encoding mode of the encoding unit 16 to the abnormal mode when executing step S403 next time.

[0045] In the subsequent step S407, the cell controller 14 executes cell control according to the control command received in step S405 and ends the process shown in FIG. 4. This cell control may include forced discharge control for preventing overcharging of the battery, battery forced cut-off control when an abnormal voltage or abnormal temperature of the battery is detected, and the like. Note that the cell control may not include battery forced cut-off control, and the cell control may be controlled to transmit a battery cut-off request to the battery management device M.

[0046] FIG. 5 is a flowchart showing in time series the main steps related to the cooperation between the encoding operation in the battery data transmission device B and the decoding and abnormality detection operations in the battery management device M, extracted from the flowcharts of FIGS. 3 and 4. The main steps are step S403 shown in FIG. 4 for the battery data transmission device B, and steps S303, S304, and S305 shown in FIG. 3 for the battery management device M.

[0047] First, the battery management device M activates the battery data transmission device B. In the first step S501, since the battery data transmission device B has just been activated, it performs encoding in the normal mode and transmits the encoded data to the battery management device M. In step S502, the battery management device M performs decoding and anomaly detection, and here it returns a normal response to the battery data transmission device B. Upon receiving this normal response, the battery data transmission device B performs encoding again in the normal mode and transmits in step S503.

[0048] In the subsequent step S504, the battery management device M performs decoding and anomaly detection, and here it returns an abnormal response to the battery management device M or gives no response. In response to this, the battery data transmission device B performs encoding in the abnormal mode in step S505 and transmits the encoded data to the battery management device M. In step S506, the battery management device M performs decoding and anomaly detection, and here it returns a normal response to the battery data transmission device B. Upon receiving this normal response, the battery data transmission device B performs encoding again in the normal mode and transmits in step S507. Similarly hereinafter, the communication between the battery data transmission device B and the battery management device M continues.

[0049] (Battery data) FIG. 6 is a schematic diagram showing battery data. The cell group CG is composed of n cells, which are called cell numbers #1, #2, #3, ···, #n from the left side in the figure. These n pieces of battery data are called V1, V2, V3, ··· Vn. Hereinafter, an n-data group transmitted at one time is called a "frame". Also, the numerical value in parentheses attached after the name of each battery data represents the time-series order of the battery data. For example, "V1(1)" represents the first piece of battery data of cell number #1, and "V3(t - 2)" represents the (t - 2)-th piece of battery data of cell number #3.

[0050] In the following description, the latest time series number is denoted as "t", and V1(t) to Vn(t) are referred to as "data of the current frame" or "data of the latest frame". V1(t - 1) to Vn(t - 1) represent n data groups that have been transmitted one frame before the current time, and are hereinafter referred to as "data one frame before". Also, V1(t - 2) to Vn(t - 2) represent n data groups that have been transmitted two frames before, and are hereinafter referred to as "data two frames before". Further, hereinafter, the data of the frames before the current frame, including the data one frame before, are collectively referred to as "data of past frames" or "past data".

[0051] Figure 7 is a schematic diagram showing the time series change of battery data. Figure 7 is a three - dimensional graph, in which the voltage axis, the cell number axis, and the time axis are orthogonal to each other. The voltage axis is such that the higher the voltage, the higher in the upper part of the illustration. The cell number axis indicates that the front of the illustration is cell number #1 and the deepest part of the illustration is cell number #n. The time axis indicates that time elapses from left to right in the illustration. t0 to t3 marked on the time axis are times provided for convenience of explanation and do not show the correlation with the "t", which is the current time series number shown in Figure 6.

[0052] Looking at the whole of Figure 7, it can be seen that although there are changes in the left - right direction of the illustration, that is, in the time series, the difference in voltage between cells at the same time, that is, in the depth direction of the illustration, is small. The following will look at it in detail. In the example shown in Figure 7, from time t0 to t1, the vehicle is stopped or traveling at a constant speed, and the voltage of each cell is almost constant. From time t1 to t2, the vehicle is accelerating or decelerating, and the voltage of each cell fluctuates greatly in the time series. From time t2 to t3, the vehicle is stopped or traveling at a constant speed again, and the voltage of each cell is almost constant.

[0053] When the cell voltage is almost constant over time, the difference between the "data of the previous frame" and the "data of the current frame" is small and close to zero. By transmitting this difference, the number of bits when represented in binary, that is, the amount of data to be transmitted, can be reduced and data compression can be achieved. In this way, the encoding method that uses the "data of the previous frame" for data compression is called "inter-frame encoding". Note that as the "previous frame", not only the frame immediately before but also arbitrarily selectable frames such as two frames before or three frames before can be used.

[0054] On the other hand, when the cell voltage changes drastically over time, the "difference" between the "data of the previous frame" and the "data of the current frame" becomes a large value, that is, a value far from 0. Therefore, as shown in FIG. 6, by utilizing the fact that the individual batteries are connected in series and the voltage of each cell increases and decreases uniformly, a difference is taken only within the "data of the current frame" to make it a small value, that is, a value close to zero, thereby compressing the amount of data to be transmitted. In this way, the encoding method that compresses data only within the "data of the current frame" is called "intra-frame encoding".

[0055] (Encoding unit and decoding unit) FIG. 8 is a functional configuration diagram of the encoding unit 16 in the embodiment. The encoding unit 16 includes an inter-frame encoding unit 801, an intra-frame encoding unit 802, a non-compression encoding unit 803, a first header addition unit 806, a second header addition unit 807, a mode selection unit 808, and a switching unit 809. The encoding unit 805 for the normal mode includes the inter-frame encoding unit 801, the intra-frame encoding unit 802, and the non-compression encoding unit 803. The encoding unit 804 for the abnormal mode is composed of the intra-frame encoding unit 802 and the non-compression encoding unit 803. That is, it has a configuration obtained by excluding the inter-frame encoding unit 801 from the encoding unit 805 for the normal mode.

[0056] The inter-frame encoding unit 801 and the intra-frame encoding unit 802 output the compressed data FCD shown in Fig. 2(b). The non-compressed encoding unit 803 outputs the non-compressed data FNC shown in Fig. 2(a). The first header addition unit 806 and the second header addition unit 807 add the encoded header FCH shown in Fig. 2(b).

[0057] The mode selection unit 808 determines which of the encoded data output from the three encoding units, namely the inter-frame encoding unit 801, the intra-frame encoding unit 802, and the non-compressed encoding unit 803, should be selected, and instructs the switching unit 809. The mode selection unit 808 generally adopts the encoded data with the shortest data length, in other words, the smallest size, among the encoded data output by the three encoding units. However, the mode selection unit 808 does not select inter-frame encoding in the abnormal mode. In addition, when there are multiple shortest codes, they are selected according to the priority order of non-compressed encoding, intra-frame encoding, and inter-frame encoding.

[0058] The non-compressed encoding by the non-compressed encoding unit 803 is an encoding that converts a plurality of battery data represented by, for example, 14 bits per battery into a data sequence of consecutive 8 bits (1 byte). This can be realized with a small amount of calculation, but there is no data compression effect. The intra-frame encoding by the intra-frame encoding unit 802 has the advantage that data errors do not propagate to the future during decoding even if data errors occur during transmission, while the data compression effect is not large.

[0059] The inter-frame encoding by the inter-frame encoding unit 801 generally has the advantage of a large data compression effect. On the other hand, when data errors occur during transmission, there is a disadvantage that data errors propagate to the future during decoding. Therefore, if the code length is the same as that output by other encodings, it is desirable to select a mode other than inter-frame encoding. The switching unit 809 selects and outputs one of the encoded data according to the selection result of the mode selection unit 808.

[0060] FIG. 9 is a functional configuration diagram of the decoding unit 17 in the embodiment. The decoding unit 17 decodes the encoded data 810 to obtain decoded data 907. The decoding unit 17 includes a header extraction unit 901, a decoding mode selection unit 902, an inter-frame decoding unit 903, an intra-frame decoding unit 904, an uncompressed decoding unit 905, and an output selection unit 906.

[0061] The header extraction unit 901 extracts the header of the encoded data 810, determines which of the inter-frame decoding unit 903, the intra-frame decoding unit 904, and the uncompressed decoding unit 905 to select from the content of the header, and instructs the decoding mode selection unit 902 and the output selection unit 906. The decoding mode selection unit 902 outputs the encoded data 810 to the decoding unit instructed by the header extraction unit 901. The details of the operations of the inter-frame decoding unit 903 and the intra-frame decoding unit 904 will be described later. The uncompressed decoding unit 905 extracts, for example, battery data represented by 14 bits per battery from a data sequence of 8 consecutive bits (1 byte). The output selection unit 906 outputs the output of the decoding unit instructed by the header extraction unit 901 as the decoded data 907.

[0062] FIG. 10 is a configuration diagram of the inter-frame encoding unit 801 in the embodiment. The inter-frame encoding unit 801 includes a frame delay unit 1001 and a subtractor 1002. The inter-frame encoding unit 801 subtracts the data of one frame before (602-(t - 1)) from the data of the current frame (602-t) for each cell, and outputs inter-frame encoded data (1003-t). The frame delay unit 1001 is provided to store the data of one frame before, and the subtractor 1002 is provided for subtraction processing.

[0063] In FIG. 10, only one frame delay unit 1001 is used to output the difference from the data one frame before (602-(t-1)). However, if two frame delay units 1001 are connected in series, it may be configured to output the difference from the data two frames before (602-(t-2)). Also, the difference from the data one frame before (602-(t-1)) and the difference from the data two frames before (602-(t-2)) may be output in parallel, and the mode selection unit 808 may be configured to select either one of them. Furthermore, data three or more frames before may be used.

[0064] FIG. 11 is a configuration diagram of the inter-frame decoding unit 903 in the embodiment. The inter-frame decoding unit 903 includes a frame delay unit 1101 and an adder 1102. The adder 1102 adds the data of the current frame (1003-t) for each cell and the data one frame before output by the frame delay unit 1101 (1103-(t-1)), and outputs the decoded data (1103-t).

[0065] Here, it should be noted that the frame delay unit 1101 and the adder 1102 are in a feedback configuration. If data errors that cannot be corrected remain in the decoded data (1103-t), the errors will propagate successively over the future (t+1, t+2,...), increasing the influence of the data errors. For this reason, as shown in the flowchart of FIG. 5, when an abnormality is detected by the battery management device M, the next encoding in the battery data transmission device M is switched to the "abnormal mode". Thereby, the inter-frame encoding, which is an encoding using past battery data at the time of decoding, is made unselectable, preventing the errors from propagating over the future (t+1, t+2,...).

[0066] In addition, when there is one frame delay unit 1001 and the "frame difference" is set to "one frame difference" as in the configuration of the inter-frame encoding unit 801 shown in FIG. 10, the "abnormal mode" may be only for a period of one frame. However, when two frame delay units 1001 are used to create a "two-frame difference", the "abnormal mode" needs to continue for a period of two frames. Similarly, when the difference is three frames or more, it is necessary to increase the period of the "abnormal mode" to three frames or more.

[0067] FIG. 12 is a configuration diagram of the intra-frame encoding unit 802 in the embodiment. The intra-frame encoding unit 802 includes a plurality of subtractors 1201-2, 1201-3, ···, 1201-n. These subtractors calculate the differences between the battery data (V1(t)) of the reference cell #1 and the battery data (V2(t) to Vn(t)) of each of cells #2 to #n. Then, the intra-frame encoding unit 802 outputs the battery data (V1(t)) of cell #1 and these differences as intra-frame encoded data 1202-t. Although FIG. 12 is based on the battery data of cell #1, it may also be based on the battery data of cells other than cell #1 (cells #2 to #n).

[0068] FIG. 13 is a configuration diagram of the intra-frame decoding unit 904 in the embodiment. The intra-frame decoding unit 904 includes a plurality of adders 1301-2, 1301-3, ···, 1301-n. These adders add the battery data (V1(t)) of the reference cell #1 to each of the difference data included in the encoded data to obtain the battery data (V2(t) to Vn(t)) of each of cells #2 to #n.

[0069] According to the above-described embodiment, the following operational effects can be obtained. (1) The battery data transmission device B detects the states of a plurality of battery cells, and transmits battery data, which is data regarding the plurality of detected battery cells, to the battery management device M via the transmission path T. The battery data transmission device B includes an encoding unit 16 that encodes the battery data with a plurality of encoding modes, a mode selection unit 808 that selects any one of the plurality of encoding modes, and a transmission control unit 15 that transmits the encoded data of the encoding mode selected by the mode selection unit 808 to the battery management device M and receives reception information of the transmitted data from the battery management device M. The mode selection unit 808 selects, according to the reception information from the battery management device M, an encoding mode that does not use past battery data at the time of decoding as the encoding mode to be transmitted this time when the communication of the previous transmission data is abnormal. Therefore, the encoding method is changed between normal times and abnormal times, and information transmission can be maintained even in a situation where a transmission error occurs.

[0070] (2) The battery data transmission device B includes a first encoding unit, that is, an inter-frame encoding unit 801 that encodes using past battery data, and a second encoding unit, that is, an intra-frame encoding unit 802 and a non-compressed encoding unit 803 that encode without using past battery data.

[0071] (3) The mode selection unit 808 selects the encoding mode that generated the encoded data with the shortest code length among the plurality of encoded data calculated by the encoding unit 16. Therefore, among the plurality of encoding modes, the encoding mode that outputs the minimum data can be surely selected. Although it is not impossible to select an optimal encoding mode according to the driving mode of the vehicle, the relationship between the driving mode and the optimal encoding mode is not absolute, and it also takes some time to determine the driving mode. Therefore, although the amount of calculation increases slightly, calculating the encoded data in advance in a plurality of ways as in the present embodiment is a reliable method for obtaining the minimum data.

[0072] (4) The battery management device M includes a transmission control unit 15-z that communicates with a battery data transmission device that wirelessly transmits encoded data obtained by encoding battery data, a decoding unit 17 that decodes the encoded data to obtain battery data, an abnormality detection unit 18 that detects an abnormality in the encoded data received by the transmission control unit or an abnormality when decoding the encoded data by the decoding unit, and a command unit (steps S305 to S309 in FIG. 3, battery control instruction unit 19) that, when the abnormality detection unit 18 detects an abnormality, outputs a command to select, as the encoding mode for the next transmission, an encoding mode that does not use past battery data during decoding to the battery data transmission device. Therefore, the battery management device M can notify the battery data transmission device B of an abnormality in the received data and prevent an error from propagating into the future when an abnormality occurs.

[0073] (5) The battery data transmission system S1 includes a battery data transmission device B that transmits, via a transmission path, encoded data obtained by encoding battery data, which is data related to a battery, and a battery management device M that receives the encoded data. The battery data transmission system S1 includes an abnormality detection unit 18 that detects an abnormality in the encoded data. The battery data transmission device B includes an encoding unit 16 that generates encoded data using the battery data, and transmission control units 15-1 to 15-n that transmit the encoded data to the battery management device via the transmission path. The encoding unit 16 has at least a first mode and a second mode as operation modes. The first mode is a mode in which encoded data is generated using past battery data. The second mode is a mode in which encoded data is generated without using past battery data. When the abnormality detection unit 18 detects an abnormality in the encoded data, the abnormality detection unit 18 causes the encoding unit to apply the second mode during the next encoding. Therefore, the battery data transmission system S1 can change the encoding method between normal times and abnormal times and maintain information transmission even in a situation where a transmission error occurs.

[0074] (Modification Example 1) FIG. 14 is a configuration diagram of the encoding unit 16A in Modification 1. The encoding unit 16A has a first entropy encoding unit 1401 and a second entropy encoding unit 1402 added to the configuration of the encoding unit 16 in the embodiment. In this modification, as described below, by converting to a variable-length code, compression can be achieved with a smaller amount of data.

[0075] Entropy encoding is a reversible encoding technique that compresses data with the same information into a smaller amount of data by converting the original data into another code based on the occurrence frequency of the data. The first entropy encoding unit 1401 and the second entropy encoding unit 1402 perform this entropy encoding. The first entropy encoding unit 1401 performs entropy encoding on the output of the inter-frame encoding unit 801 and outputs it to the first header addition unit 806. The second entropy encoding unit 1402 performs entropy encoding on the output of the intra-frame encoding unit 802 and outputs it to the second header addition unit 807. The first entropy encoding unit 1401 and the second entropy encoding unit 1402 have different input sources and output destinations, but the operations are the same.

[0076] The differences between frames of battery data and the differences between cells within the same frame are mostly values close to "0". Therefore, in entropy encoding, relatively short codes are assigned to data with small absolute values. On the other hand, cases where the difference is a large value, for example, a case where the voltage value measured last time is also different by several hundred millivolts, are rare. Therefore, in entropy encoding, long codes are assigned to data with large absolute values. In this way, by assigning variable-length codes according to the occurrence frequency of each data value, it becomes possible to compress the overall transmission data into a smaller amount of data. Representative examples of entropy codes include Huffman codes, Shannon codes, arithmetic codes, range codes, etc., and any of them may be adopted in this embodiment. Hereinafter, an example in the case of using a Huffman code will be described.

[0077] FIG. 15 is a diagram showing an example of a Huffman table. The Huffman code prepares a conversion table called a Huffman table in advance, and encoding and decoding can be realized simply by referring to this conversion table, so the amount of calculation is relatively small and it operates at high speed. Encoding is performed by one-to-one converting the decimal input data shown in FIG. 15(a) into the binary output data shown in FIG. 15(b). Conversely, decoding is performed by one-to-one converting the binary input data shown in FIG. 15(b) into the decimal output data shown in FIG. 15(a).

[0078] For example, three consecutive decimal input data “-1, 0, 1” are encoded into the consecutive binary output data (symbols) “001110010”, and conversely, the consecutive binary input data (symbols) “001110010” are decoded into three consecutive decimal output data “-1, 0, 1”. This Huffman table is set in advance based on the occurrence frequency of the data using a large number of sample data. Therefore, if the sample data used for the setting is changed, the content of the Huffman table also changes.

[0079] The output of the inter-frame encoding unit 801, that is, the frame difference, and the output of the intra-frame encoding unit 802, that is, the difference between cells within the same frame, have different occurrence frequencies of data values. Therefore, it is desirable that the first entropy encoding unit 1401 and the second entropy encoding unit 1402 each create and hold a different Huffman table in advance.

[0080] FIG. 16 is a configuration diagram of the decoding unit 17A in the first modification. FIG. 16 is the configuration of the decoding unit 17 shown in FIG. 9 with the addition of a first entropy decoding unit 1601 and a second entropy decoding unit 1602. The first entropy decoding unit 1601 and the second entropy decoding unit 1602 perform entropy decoding using, for example, the Huffman table shown in FIG. 15, and decode the encoded data (1405) output by the encoding unit 16 in FIG. 14.

[0081] According to this Modification Example 1, entropy encoding is adopted for encoding, and the data length of the encoded data can be reduced regardless of the presence or absence of communication abnormalities. Note that the Huffman table may be updated as appropriate. For example, data may be accumulated while the vehicle is being driven, and the Huffman table may be updated when the vehicle stops.

[0082] (Modification Example 2) FIG. 17 is a configuration diagram of the encoding unit 16B in Modification Example 2. The encoding unit 16B in this modification example has a configuration in which the two entropy encoding units included in the encoding unit 16A shown in FIG. 14 in Modification Example 1 are combined into one and moved. In the mode selection unit 1701, the sum of the absolute values of the outputs of the inter-frame encoding unit 801 and the intra-frame encoding unit 802 is compared, and the output with the smaller sum value is selected by the selection unit 807. However, the mode selection unit 1701 may use the average value of the absolute values instead of the sum of the absolute values. That is, the mode selection unit 1701 may compare the average of the absolute values of the outputs of the inter-frame encoding unit 801 and the intra-frame encoding unit 802, and select the output with the smaller sum value by the selection unit 807.

[0083] The additional mode selection unit 1704 compares the code lengths of the output of the header addition unit 1703 and the output of the non-compression encoding unit 803, and causes the switching unit 809 to select the code with the shorter length. Note that the output of the header addition unit 1703 is the sum of the encoding header FCH and the compressed data FCD shown in FIG. 2(b). The output of the non-compression encoding unit 803 is the non-compressed data FNC shown in FIG. 2(a).

[0084] FIG. 18 is a configuration diagram of the decoding unit 17B in Modification Example 2. The decoding unit 17B in this modification example has a configuration in which the two entropy decoding units included in the decoding unit 17A shown in FIG. 16 in Modification Example 1 are combined into one and moved. The entropy decoding unit 1802 decodes the encoded data 1705 output by the encoding unit 16B.

[0085] According to this Modification Example 2, since the amount of calculation is reduced, even a weak CPU such as a microcomputer can operate at high speed.

[0086] (Modification Example 3) FIG. 19 is a schematic diagram showing a data recording method in Modification Example 3. Specifically, FIG. 19(a) shows the recording method in the embodiment, and FIG. 19(b) shows the data recording method in this modification example. FIG. 19(a) is a schematic diagram showing, for n pieces of battery data, the n pieces of data output by the inter-frame encoding unit 801 bit by bit from the MSB (most significant bit) to the LSB (least significant bit). In FIG. 19(a), the MSB is the positive / negative polarity flag. The positive / negative polarity flag is a flag indicating whether the data is a positive value or a negative value. FIG. 19(b) divides the same n pieces of data into a "positive / negative polarity flag" and an "absolute value", and further represents the "positive / negative polarity flag" collectively with 1 bit.

[0087] As shown in FIGS. 1 and 6, since all the battery cells are connected in series, the increasing and decreasing trends of the voltages of each battery cell generally coincide. Therefore, since the "positive / negative polarity flags" of the data of the frame differences are basically the same for all n of them, they can be summarized into 1 bit as shown in FIG. 19(b), and as a result, the data amount can be reduced by (n - 1) bits compared to the expression shown in FIG. 19(a).

[0088] FIG. 20 is a configuration diagram of the first inter-frame encoding unit 801A in Modification Example 3. The first inter-frame encoding unit 801A includes a plurality of subtractors 1002-1 to 1002-n, polarity extraction units 2002-1 to 2002-n, absolute value encoding units 2003-1 to 2003-n, and a coincidence confirmation unit 2004. The coincidence confirmation unit 2004 determines whether the positive / negative polarities of all the data, that is, "V1(t) - v1(t - 1)" to "Vn(t) - Vn(t - 1)", coincide. If all coincide, the coincidence confirmation unit 2004 outputs the converted data 2005-t.

[0089] The data 2005-t after this conversion corresponds to the data shown in FIG. 19(b). If there is any data that does not match, the matching confirmation unit 2004 outputs a non-matching detection result (2006) and instructs the mode selection unit 808 not to select this mode. Hereinafter, the polarity extraction units 2002-1 to 2002-n and the matching confirmation unit 2004 are collectively referred to as the "flag generation unit". This flag generation unit generates flag information representing the positive or negative of the difference between past battery data and current battery data. The absolute value encoding units 2003-1 to 2003-n encode the absolute value of the difference between the "data of the past frame" and the "data of the current frame" of each cell. The details of the encoding process are the same as those in the embodiment.

[0090] FIG. 21 is a configuration diagram of the inter-frame decoding unit 903A in the third modification. The inter-frame decoding unit 903A includes a plurality of multipliers 2103-1 to 2103-n and a conversion unit 2102.

[0091] In the conversion unit 2102, if the value of the positive / negative polarity flag included in the encoded data (1805-t) is "0", that is, a flag indicating a positive value, "+1" is output, and if the value of the positive / negative polarity flag is "1", a flag indicating a negative value, "-1" is output. Next, using the multipliers 2103-1 to 2103-n, the product of "+1" or "-1" corresponding to the flag and the absolute value included in the encoded data (2005-t) is calculated. Then, after returning to the frame difference data "V1(t)-V1(t-1)" to "Vn(t)-Vn(t-1)" (1003-t) before taking the absolute value, the data "V1(t) to Vn(t)" (2104-t) before encoding this time is obtained by adding it to the previously decoded "V1(t-1) to Vn(t-1)" (602-(t-1)).

[0092] According to this third modification, the following operational effects can be obtained. (6) The inter-frame encoding unit 801A includes a flag generation unit 2002Z that generates flag information indicating the positive or negative sign of the difference between past battery data and current battery data, and absolute value encoding units 2003-1 to 2003-n that perform encoding using data representing the absolute value of the difference. Therefore, the data length of the encoded data can be reduced.

[0093] (Modification Example 4) FIG. 22 is a configuration diagram of the second inter-frame encoding unit 801B in Modification Example 4. The second inter-frame encoding unit 801B in Modification Example 4 differs from Modification Example 3 in that it is effective even when the positive and negative polarity flags do not match. This will be described in detail below.

[0094] The second inter-frame encoding unit 801B includes a majority flag generation unit 2202, comparators 2203-1 to 2203-n, integrators 2204-1 to 2204-n, and subtractors 1002-1 to 1002-n. The majority flag generation unit 2202 takes the majority of the positive and negative polarities of each cell and determines the positive-negative conversion flag. Specifically, when there are more positive values or the number of positive values is the same as the number of negative values, that is, when the number of cells where "Vi(t) ≧ Vi(t-1)" ≥ the number of cells where "Vi(t) < Vi(t-1)", the majority flag generation unit 2202 sets "0" as the positive-negative conversion flag. Also, when there are more negative values, that is, when the number of cells where "Vi(t) ≧ Vi(t-1)" < the number of cells where "Vi(t) < Vi(t-1)", the majority flag generation unit 2202 sets "1" as the positive-negative conversion flag.

[0095] Furthermore, the inter-frame encoder 801B uses comparators 2203-1 to 2203-n to compare the positive and negative polarities of each cell with the positive and negative conversion flags. When they match, it outputs "+1" as the comparison result (S1 to Sn), and when they do not match, it outputs "-1". Then, integrators 2204-1 to 2204-n multiply this output by the outputs of subtractors 1002-1 to 1002-n respectively. The inter-frame encoder 801B outputs the frame difference after positive and negative conversion ((V1(t) - V1(t - 1))S1) to (Vn(t) - Vn(t - 1))Sn)) thus obtained, together with the positive and negative conversion flags, as encoded data (2205-t). Note that since the operation results by integrators 2204-1 to 2204-n are information excluding the positive and negative conversion flags of the encoded data (2205-t), comparators 2203-1 to 2203-n and integrators 2204-1 to 2204-n can also be called the "second absolute value encoder".

[0096] FIG. 23 is a configuration diagram of the inter-frame decoder 903B in Modification 4. Although the information stored as the encoded data (2205-t) is different from that in Modification 3, the configuration and processing of the inter-frame decoder 903B are the same as those of the inter-frame decoder 903A shown in FIG. 21.

[0097] According to this Modification 4, the following operational effects can be obtained. (7) The first encoding unit, i.e., the inter-frame encoding unit 801, includes a majority flag generation unit 2202 that generates flag information representing the majority decision result of the number of positive and negative differences between past battery data and current battery data, and a second absolute value encoding unit, i.e., comparators 2203-1 to 2203-n and integrators 2204-1 to 2204-n, that encode using the battery data converted based on the majority decision result. Therefore, the data length of the encoded data can be reduced in various cases. Specifically, it is as follows. That is, in Modification 3, it was assumed that the positive and negative polarity flags match, but there may be cases where not all "positive and negative polarity flags" match. For example, due to a deviation in the time (sampling time) for measuring the voltage of each battery cell, a forced discharge operation (balancing) of each individual battery cell to prevent overcharging, differences in the parasitic capacitance of each battery, etc., not all positive and negative polarity flags may match. Even in such cases, in this modification, the data length of the encoded data can be reduced.

[0098] (Modification 5) FIG. 24 is a configuration diagram of the encoding unit 16C in Modification 5. The encoding unit 16C includes an inter-frame encoding unit 801, a first inter-frame encoding unit 801A, a second inter-frame encoding unit 801B, an intra-frame encoding unit 802, a non-compression encoding unit 803, a first entropy encoding unit 1401, a fourth entropy encoding unit 2401, a third entropy encoding unit 2402, a second entropy encoding unit 1402, a first header addition unit 2405, a second header addition unit 2406, a third header addition unit 2407, a fourth header addition unit 2408, a mode selection unit 2409, and a selection unit 2410.

[0099] The operations of the inter-frame encoding unit 801, the intra-frame encoding unit 802, the non-compression encoding unit 803, the first entropy encoding unit 1401, and the second entropy encoding unit 1402 are as described in Modification 1. The operation of the first inter-frame encoding unit 801A is as described in Modification 3. The operation of the second inter-frame encoding unit 801B is as described in Modification 4.

[0100] The fourth entropy encoding unit 2401 performs entropy encoding processing on the output of the first inter-frame encoding unit 801A. The third entropy encoding unit 2402 performs entropy encoding processing on the output of the second inter-frame encoding unit 801B. The first header addition unit 2405 to the fourth header addition unit 2408 add headers corresponding to the outputs of the respective encoding units. The mode selection unit 2409 selects the encoded data with the shortest data length among the five encoded data and causes the selection unit 2410 to select it.

[0101] FIG. 25 is a configuration diagram of the decoding unit 17C in the fifth modification. The decoding unit 17C includes an inter-frame decoding unit 903, a first inter-frame decoding unit 903A, a second inter-frame decoding unit 903B, an intra-frame decoding unit 904, an uncompressed decoding unit 905, a first entropy decoding unit 1601, a fourth entropy decoding unit 2503, a third entropy decoding unit 2504, a second entropy decoding unit 1602, a header extraction unit 2501, a decoding mode selection unit 2502, and an output selection unit 2505.

[0102] The header extraction unit 2501 extracts the header of the encoded data 2411, determines which decoding unit to select from the content of the header, and instructs the decoding mode selection unit 902 and the output selection unit 906. The decoding mode selection unit 902 outputs the encoded data 810 to the entropy decoding unit connected to the decoding unit indicated by the header extraction unit 901.

[0103] The operations of the inter-frame decoder 903, the intra-frame decoder 904, the non-compressed decoder 905, the first entropy decoder 1601, and the second entropy decoder 1602 are as described in Modification 1. The operation of the first inter-frame decoder 903A is as described in Modification 3. The operation of the second inter-frame decoder 903B is as described in Modification 4. The fourth entropy decoder 2503 performs entropy decoding on the input encoded data 2411 and outputs it to the first inter-frame decoder 903A. The third entropy decoder 2504 performs entropy decoding on the input encoded data 2411 and outputs it to the second inter-frame decoder 903B.

[0104] (Modification 6) FIG. 26 is a flowchart showing the operation of the battery data transmission device in Modification 6. In this modification, the battery data transmission device B further includes a retransmission unit R. In FIG. 26, steps S2601 to S2604, which are processes for retransmitting data, are added to the flowchart showing the operation of the battery data transmission device B shown in FIG. 4 in the embodiment. Hereinafter, the processes of the added steps S2601 to S2604 will be mainly described. The processes of steps S2601 to S2604 are executed by the retransmission unit R. The retransmission unit R is realized, for example, by a CPU expanding a program stored in the ROM into the RAM and executing it, like the transmission control unit 15 and the encoding unit 16.

[0105] In step S2601, which is executed next to step S403, the retransmission unit R resets the number of retransmissions to zero and proceeds to step S404. When steps S404 and S405 are executed, the retransmission unit R executes step S2602. In step S2602, the retransmission unit R determines whether or not the control command received in step S405 includes a normal response (Ack). If the retransmission unit R determines that a normal response is included, it proceeds to step S406, and if it determines that a normal response is not included, it proceeds to step S2603.

[0106] In step S2603, the retransmission unit R determines whether the number of retransmissions is equal to or greater than a predetermined value. If the retransmission unit R determines that the number of retransmissions is equal to or greater than the predetermined value, it proceeds to step S406 without retransmitting. If it determines that the number of retransmissions is less than the predetermined value, it proceeds to step S2604. In step S2604, the retransmission unit R increments the number of transmissions, that is, increases it by "1", and returns to step S404.

[0107] According to this modification, the following operational effects can be obtained. (8) The battery data transmission device B further includes a retransmission unit R that retransmits the encoded data transmitted previously when the communication of the previous transmission data is abnormal. Therefore, even if a sudden data error occurs, the possibility of achieving error-free transmission can be increased while retransmitting the same encoded data several times. And only when a data error occurs even after retransmission, it enters the abnormal mode, so that the encoding in the normal mode that can be more compressed in terms of data volume can be used more frequently.

[0108] (Modification 7) In the above-described embodiment, after each encoding unit actually performs encoding, in principle, the mode selection unit 808 selects the data with the shortest data length. In case of an abnormality, it selects the data with the shortest data length excluding the output of the inter-frame encoding unit 801. However, an optimal encoding method may be selected in advance according to the operating mode of the vehicle. For example, taking the absolute value of the vehicle's acceleration as an evaluation index, when this value is less than or equal to a predetermined threshold, that is, when the speed change is small, the inter-frame encoding unit 801 is operated, and this output is used as the encoded data. Also, when this value is greater than the predetermined threshold, that is, when the speed change is large, the intra-frame encoding unit 802 is operated, and this output is used as the encoded data. However, it is the same as the embodiment that the inter-frame encoding unit 801 is not adopted in case of communication abnormality.

[0109] (Modification 8) In the above-described embodiments, the encoding unit 16 may include at least one of an intra-frame encoding unit 802 and an uncompressed encoding unit 803. In this case, the decoding unit 17 may include one of the intra-frame decoding unit 904 and the uncompressed decoding unit 905 that corresponds to the configuration included in the encoding unit 16.

[0110] In each of the above-described embodiments and modification examples, the configuration of the functional blocks is merely an example. Some of the functional configurations shown as separate functional blocks may be integrated, or the configuration represented by one functional block diagram may be divided into two or more functions. Also, a part of the functions of each functional block may be provided by another functional block.

[0111] Each of the above-described embodiments and modification examples may be combined. Although various embodiments and modification examples have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

Explanation of Signs

[0112] 15…Transmission control unit 16…Encoding unit 17…Decoding unit 18…Abnormality detection unit 801…Inter-frame encoding unit 802…Intra-frame encoding unit 803…Uncompressed encoding unit 808…Mode selection unit B…Battery data transmission device M…Battery management device

Claims

1. A battery data transmission device that detects the states of a plurality of battery cells and transmits battery data, which is data regarding the detected plurality of battery cells, via a transmission path, comprising: an encoding unit that has a plurality of encoding modes and encodes the battery data into encoded data; a mode selection unit that selects any one of the plurality of encoding modes; a transmission control unit that transmits the encoded data of the encoding mode selected by the mode selection unit to a battery management device and receives reception information of the transmitted data from the battery management device; wherein the mode selection unit selects, as the encoding mode to be transmitted this time, an encoding mode that does not use past battery data at the time of decoding when the communication of the previous transmission data is abnormal according to the reception information from the battery management device. A battery data transmission device.

2. The battery data transmission device according to claim 1, wherein the encoding unit comprises: a first encoding unit that encodes using past battery data; and a second encoding unit that encodes without using past battery data. A battery data transmission device.

3. The battery data transmission device according to claim 1, wherein when the communication of the previous transmission data is normal, the mode selection unit selects the encoding mode that generated the encoded data having the shortest code length among the plurality of encoded data calculated by the encoding unit. A battery data transmission device.

4. The battery data transmission device according to claim 2, wherein the first encoding unit comprises: a flag generation unit that generates flag information representing the positive or negative of the difference between past battery data and current battery data; and an absolute value encoding unit that encodes using data representing the absolute value of the difference. A battery data transmission device.

5. The battery data transmission device according to claim 2, wherein the first encoding unit comprises: a flag generation unit that generates flag information representing the majority decision result of the number of positives and negatives of the difference between past battery data and current battery data; and a second absolute value encoding unit that encodes using battery data converted based on the majority decision result. A battery data transmission device.

6. The battery data transmission device according to claim 1, further comprising a retransmission unit that retransmits the encoded data transmitted last time when the communication of the previous transmission data is abnormal. A battery data transmission device.

7. ​ A transmission control unit that communicates with a battery data transmission device that wirelessly transmits encoded data obtained by encoding battery data, A decoding unit that decodes the encoded data to obtain the battery data, An abnormality detection unit that detects an abnormality in the encoded data received by the transmission control unit or an abnormality when decoding the encoded data by the decoding unit, A battery management device comprising: a command unit that, when the abnormality detection unit detects an abnormality, outputs a command to select, as an encoding mode for the next transmission, an encoding mode that does not use past battery data during decoding, to the battery data transmission device.

8. A battery data transmission method for detecting the states of a plurality of battery cells and transmitting, via a transmission path, battery data that is data regarding the plurality of detected battery cells, A data encoding process for encoding the battery data using any one of a plurality of encoding modes, An encoding mode selection process for selecting any one encoding mode from among the plurality of encoding modes, A data transmission / reception process that includes transmitting, to a battery management device, the encoded data of the encoding mode selected by the encoding mode selection process and receiving reception information of the transmitted data from the battery management device, The encoding mode selection process selects, as the encoding mode for the current transmission, an encoding mode that does not use past battery data during decoding when the communication of the previous transmission data is abnormal, according to the reception information from the battery management device. A battery data transmission method.

9. A battery data transmission system including a battery data transmission device that transmits, via a transmission path, encoded data obtained by encoding battery data that is data regarding a battery, and a battery management device that receives the encoded data, Including an abnormality detection unit that detects an abnormality in the encoded data, The battery data transmission device, An encoding unit that generates the encoded data using the battery data, A transmission control unit that transmits the encoded data to the battery management device via the transmission path, The encoding unit has at least a first mode and a second mode as operation modes, The first mode is a mode in which the encoded data is generated using past battery data, The second mode is a mode in which the encoded data is generated without using past battery data, When the abnormality detection unit detects an abnormality in the encoded data, it causes the encoding unit to apply the second mode during the next encoding, in a battery data transmission system.

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