JP7031478B2 - Wireless communication system - Google Patents

Description

The present disclosure relates to a wireless communication system including a transmitter, a repeater and a receiver.

In International Publication No. 2015/063945 (Patent Document 1), a plurality of transmitters (cell management devices) for transmitting radio wave signals indicating the states of a plurality of battery cells, and radio wave signals from the plurality of transmitters are received. A battery control system including a receiver (assembled battery management device) is disclosed. In this battery control system, when wireless communication is not possible between the receiver and some transmitters, another transmitter is used as a repeater, and the radio signal from some transmitters is another. It is transmitted to the receiver by relaying the transmitter of.

International Publication No. 2015/063945

As described above, in the battery control system disclosed in Patent Document 1, another transmitter is used as a repeater, and radio signals from some transmitters pass through the repeater (other transmitter). May be sent to the receiver.

However, when the distance between the repeater and the receiver is short, a phenomenon in which multiple transmission waves arriving at the receiver from the repeater via multiple paths interfere with each other and cancel each other out (so-called multipath fading). There is a concern that the signal strength received by the receiver will decrease due to the effect.

As a countermeasure against multipath fading, it is effective to perform a process (so-called frequency hopping) in which the frequency of radio waves transmitted by a transmitter or a repeater (hereinafter, also referred to as "transmission frequency") is randomly changed within a predetermined range. It has been known. However, when the distance between the repeater and the receiver is short, even if the repeater performs frequency hopping, the effect is small and there is a possibility that the decrease in signal strength cannot be appropriately suppressed.

The present disclosure has been made to solve the above-mentioned problems, and an object thereof is to be received by a receiver in a wireless communication system in which a radio signal from a transmitter is transmitted to a receiver via a repeater. It is to appropriately suppress the decrease in signal strength.

The wireless communication system according to the present disclosure includes a transmitter, a repeater, and a receiver. The transmitter transmits a radio signal to the repeater. The repeater receives the radio signal from the transmitter and transmits it to the receiver. The receiver receives a composite wave in which a plurality of transmission waves transmitted from each of the radio wave signals transmitted from the repeater via a plurality of paths are combined. The repeater is arranged at a position farther from the receiver than the transmitter and at a position where the frequency of the radio signal having the amplitude of the combined wave equal to or higher than the amplitude of each of the plurality of transmitted waves exists.

According to the above system, the repeater is located at a position farther from the receiver than the transmitter and at a position where the frequency of the radio signal having the amplitude of the combined wave equal to or higher than the amplitude of each of the plurality of transmitted waves exists. Be placed. Therefore, the signal strength received by the receiver can be amplified at at least one or more transmission frequencies by the repeater performing frequency hopping to change the transmission frequency. As a result, the information from the transmitter can be transmitted to the receiver while suppressing the decrease in the signal strength received by the receiver.

According to the present disclosure, in a wireless communication system in which a radio wave signal from a transmitter is transmitted to a receiver via a repeater, it is possible to appropriately suppress a decrease in signal strength received by the receiver.

It is a figure (the 1) which shows typically an example of the structure of the battery control system including a wireless communication system. It is a figure which showed an example of the path and the waveform of the radio wave transmitted from a transmitter to a receiver schematically. It is a figure which shows an example of the waveform of a transmitted wave, a reflected wave, and a synthetic wave. It is a figure which shows the amplitude change of the synthetic wave when the transmission path difference is small. It is a figure which shows the amplitude change of the synthetic wave when the transmission path difference is large. It is a figure which shows an example of the correspondence relation with the transmission path difference and the amplitude change amount of a synthetic wave. It is a figure which showed an example of the path and the waveform of the radio wave transmitted from a repeater to a receiver schematically. It is a flowchart which shows an example of the processing procedure at the time of transmitting a signal from a transmitter to a receiver via a repeater. It is a figure (2) which shows typically an example of the structure of the battery control system including a wireless communication system. It is a figure which shows the comparative example of transmission timing. It is a figure which shows an example of transmission timing.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

FIG. 1 is a diagram schematically showing an example of a configuration of a battery control system 1 including a wireless communication system according to the present embodiment. The battery control system 1 is mounted on an electric vehicle such as a hybrid vehicle or an electric vehicle. The wireless communication system according to the present disclosure is not necessarily limited to application to a battery control system for a vehicle, and can also be applied to a wireless communication system used for applications other than vehicles or applications other than battery control.

The battery control system 1 includes a plurality of battery units 2, an ECU (Electronic Control Unit) 4, a plurality of transmitters 10, a receiver 20, and a repeater 30.

The plurality of battery units 2 are regularly arranged inside the battery pack. In the example shown in FIG. 1, eight battery units 2 are arranged in two rows of four each.

Each of the plurality of battery units 2 includes a battery (battery cell or assembled battery) for storing electric power for driving a traveling motor, a sensor for detecting the voltage of the battery, and the like.

The plurality of transmitters 10, the repeater 30, and the receiver 20 are configured to be capable of wireless communication with each other. Each of the transmitter 10a, the repeater 30, and the receiver 20 includes a register for temporarily storing data. Each transmitter 10a and repeater 30 can transmit the data stored in the register according to a predetermined communication schedule. The receiver 20 can receive a signal from each transmitter 10a or a repeater 30 according to a predetermined communication schedule.

The plurality of transmitters 10 are provided corresponding to the plurality of battery units 2, respectively. Each transmitter 10 can transmit a radio wave signal indicating the voltage of the battery contained in the corresponding battery unit 2 to the receiver 20 directly or by relaying the repeater 30.

The repeater 30 can receive the radio wave signal transmitted from the transmitter 10 and transmit the received signal to the receiver 20.

The receiver 20 is wiredly connected to the ECU 4. The receiver 20 receives the radio wave signal transmitted from each transmitter 10 or the repeater 30, and outputs the information to the ECU 4. The ECU 4 monitors the state of the plurality of battery units 2 and controls charging / discharging based on the information from the receiver 20.

The repeater 30 is arranged at a position farther from the receiver 20 than any of the plurality of transmitters 10. In other words, the distance D3 between the repeater 30 and the receiver 20 is set to a value larger than any of the distances between the transmitter 10 and the receiver 20.

In the present disclosure, the number of transmitters 10 is not necessarily limited to a plurality, and may be one. Hereinafter, among the plurality of transmitters 10, the transmitter 10a having a short distance from the receiver 20 (the second transmitter 10 from the right in the lower row in FIG. 1) will be described. The distance D1 between the transmitter 10a and the receiver 20 is less than half the distance D3 between the repeater 30 and the receiver 20, and is shorter than the distance D2 between the transmitter 10a and the repeater 30.

In such a transmitter 10a, since the distance D1 from the receiver 20 is short, when a radio wave is directly transmitted from the transmitter 10a to the receiver 20, the signal received by the receiver 20 due to the influence of so-called multipath fading. There is concern that the strength will decrease.

FIG. 2 is a diagram schematically showing an example of a radio wave path and waveform transmitted from the transmitter 10a to the receiver 20. FIG. 2 shows an example in which the transmitter 10a and the receiver 20 are provided between the resin member 6 and the metal member 8. In this example, as shown in FIG. 2, the radio wave signal transmitted from the transmitter 10a is directly transmitted without being reflected by the metal member 8, and is reflected and transmitted by the metal member 8. It reaches the receiver 20 via each of the routes B.

Here, the phase of the transmission wave passing through the path B is inverted when reflected by the metal member 8. Therefore, the transmission wave that reaches the receiver 20 via the path A (hereinafter, also referred to as “transmitted wave”) and the transmission wave that reaches the receiver 20 via the path B (hereinafter, also referred to as “reflected wave”). A phenomenon (multipath fading) occurs in which and the like interfere with each other and cancel each other out. As a result, the intensity level (amplitude) of the synthetic wave received by the receiver 20 is lower than the intensity level (amplitude) of the transmitted wave and the reflected wave.

FIG. 3 is a diagram showing an example of waveforms of a transmitted wave, a reflected wave, and a synthesized wave when the transmission frequency is fixed to a predetermined value f1. In FIG. 3, the horizontal axis indicates the phase of each radio wave, and the vertical axis indicates the amplitude of each radio wave. In FIG. 3 and the figure described later, the amplitude is “1” for the amplitude of the transmitted wave.

In the example shown in FIG. 3, the amplitudes of the transmitted wave and the reflected wave are both 1, and the phases are inverted (180 ° out of phase). Therefore, the signal strength of the combined wave obtained by combining the transmitted wave and the reflected wave is (Amplitude) is almost 0.

It is known that it is effective to perform "frequency hopping" in which the transmission frequency is randomly changed within a predetermined range as a countermeasure against such a decrease in intensity due to multipath fading. However, when the distance D1 between the transmitter 10a and the receiver 20 is short, the difference between the length of the path A and the length of the path B (hereinafter, also referred to as “transmission path difference”) is small, so that the effect of frequency hopping is small. It is not possible to properly suppress the decrease in reception intensity due to multipath fading.

FIG. 4 shows a composite wave when the transmission frequency is changed in the range from the minimum value fmin to the maximum value fmax by performing frequency hopping when the transmission path difference is a predetermined value DS (for example, about several centimeters). It is a figure which shows the amplitude change of. As shown in FIG. 4, when the transmission path difference is small, the amplitude (signal intensity) of the combined wave does not change much even if the transmission frequency is changed, and both are less than "1". Therefore, even if frequency hopping is performed, the effect is small, and the decrease in reception intensity due to multipath fading cannot be appropriately suppressed.

FIG. 5 shows a composite wave when the transmission frequency is changed in the range from the minimum value fmin to the maximum value fmax by performing frequency hopping when the transmission path difference is a predetermined value DL (for example, about several meters). It is a figure which shows the amplitude change. As shown in FIG. 5, when the transmission path difference is large, the amplitude (signal intensity) of the combined wave changes greatly by changing the transmission frequency, and may exceed "1". That is, when the transmission path difference is large, the effect of frequency hopping is large, and the decrease in reception intensity due to multipath fading can be appropriately suppressed.

FIG. 6 is a diagram showing an example of the correspondence between the transmission path difference and the amount of change in the amplitude of the synthetic wave. The correspondence shown in FIG. 6 is obtained by an experiment in which the amount of change in the amplitude of the combined wave when the transmission frequency is changed in the range from the minimum value fmin to the maximum value fmax by frequency hopping is measured for each transmission path difference. Is the result. From this experimental result, it can be understood that the amount of change in the amplitude of the combined wave generally exceeds "1" when the transmission path difference exceeds the reference value dth.

Since the distance D1 from the receiver 20 of the transmitter 10a according to the present embodiment is small, the transmission path difference is less than the reference value dth. Therefore, when the radio wave is directly transmitted from the transmitter 10a to the receiver 20, the amount of change in the amplitude of the combined wave is less than "1" even if frequency hopping is performed.

Therefore, in the present embodiment, a repeater 30 is provided which relays the signal from the transmitter 10a and transmits the signal to the receiver 20.

FIG. 7 is a diagram schematically showing an example of a radio wave path and waveform transmitted from the repeater 30 to the receiver 20. The repeater 30 transmits the radio wave signal received from the transmitter 10a to the receiver 20. The radio wave signal transmitted from the repeater 30 passes through the path A which is directly transmitted without being reflected by the metal member 8 and the path B which is reflected and transmitted by the metal member 8, respectively, to the receiver 20. To reach.

Here, the repeater 30 is located at a position farther from the receiver 20 than the transmitter 10a and at a position where a transmission frequency in which the amplitude of the synthetic wave received by the receiver 20 is equal to or higher than the amplitude of the transmission wave exists. Be placed. Specifically, the distance D3 between the repeater 30 and the receiver 20 is set to a value larger than the distance D1 between the transmitter 10a and the receiver 20 and exceeds the "reference distance Dth". There is. Here, the "reference distance Dth" is a distance at which the amount of change in the amplitude of the synthetic wave when the transmission frequency is changed by frequency hopping becomes the amplitude "1" of the transmission wave, that is, the reference value whose transmission path difference is shown in FIG. It is a distance that becomes dth.

Since the distance D3 between the repeater 30 and the receiver 20 is set to a value exceeding the reference distance Dth, the repeater 30 performs frequency hopping to change the transmission frequency, so that at least one transmission frequency is used. , The signal strength received by the receiver 20 can be amplified. As a result, the data from the transmitter 10a can be transmitted to the receiver 20 while suppressing the decrease in the signal strength received by the receiver 20.

Further, when the distance D2 between the repeater 30 and the transmitter 10a is short, there may be a problem that the reception strength is lowered when the repeater 30 receives the signal from the transmitter 10a. In view of this point, in the present embodiment, not only the distance D3 between the repeater 30 and the receiver 20 but also the distance D2 between the repeater 30 and the transmitter 10a exceeds the above-mentioned reference distance Dth. The arrangement of 30 is decided. Therefore, when the transmitter 10a transmits a signal to the repeater 30, frequency hopping is performed to change the transmission frequency, so that the signal strength received by the repeater 30 is amplified at at least one transmission frequency. .. As a result, the decrease in signal strength received by the repeater 30 from the transmitter 10a can be appropriately suppressed.

FIG. 8 is a flowchart showing an example of a processing procedure when a signal from the transmitter 10a is transmitted to the receiver 20 via the repeater 30. In FIG. 8, the processing of the transmitter 10a is shown in the center, the processing of the repeater 30 is shown on the right side, and the processing of the receiver 20 is shown on the left side.

First, the processing of the transmitter 10a will be described. The transmitter 10a acquires the measured value of the battery voltage detected by the sensor included in the corresponding battery unit 2 (step S10). The transmitter 10a stores the acquired measured value data of the battery voltage in the register (step S11).

Next, the transmitter 10a determines whether or not there is a vacancy in the packet (Queue) scheduled to be transmitted to the repeater 30 next time (step S12). If there is no free packet (NO in step S12), the transmitter 10a rejects the data stored in the register (step S16).

When there is a vacancy in the packet (YES in step S12), the transmitter 10a stores the data (measured value of the battery voltage) stored in the register in the packet (step S13), and the packet is in the communication timing with the repeater 30. A radio signal representing the data is transmitted to the repeater 30 (step S14). At this time, the transmitter 10a changes the transmission frequency in the range from the minimum value fmin to the maximum value fmax by frequency hopping. As a result, the data from the transmitter 10a is received by the repeater 30.

The transmitter 10a does not transmit the radio wave signal at the communication timing with the receiver 20. That is, the transmitter 10a does not directly transmit the radio wave signal to the receiver 20.

After that, the transmitter 10a determines whether or not the reply signal Ack from the repeater 30 has been received (step S15). When the reply signal Ac is received (YES in step S15), the transmitter 10a rejects the data stored in the register (step S16).

Next, the processing of the repeater 30 will be described. The repeater 30 determines whether or not the data from the transmitter 10a has been received at the communication timing with the transmitter 10a (step S20). When the data from the transmitter 10a is received (YES in step S20), the reply signal Ac is transmitted to the transmitter 10a (step S21). After that, the repeater 30 stores the data received from the transmitter 10a in the register (step S22).

Next, the repeater 30 determines whether or not there is a vacancy in the packet scheduled to be transmitted to the receiver 20 next time (step S23). If there is no free packet (NO in step S23), the repeater 30 rejects the data stored in the register (step S27).

When there is a vacancy in the packet (YES in step S23), the repeater 30 stores the data stored in the register (measured value of the battery voltage received from the transmitter 10a) in the packet (step S24), and the receiver 20. A radio wave signal representing packet data is transmitted to the receiver 20 at the communication timing with (step S25). At this time, the repeater 30 changes the frequency of the radio wave signal in the range from the minimum value fmin to the maximum value fmax by frequency hopping. As a result, the radio signal from the repeater 30 is received by the receiver 20.

After that, the repeater 30 determines whether or not the reply signal Ack from the receiver 20 has been received (step S26). When the reply signal Ac is received (YES in step S26), the repeater 30 rejects the data stored in the register (step S27).

Next, the processing of the receiver 20 will be described. The receiver 20 determines whether or not the data from the repeater 30 has been received at the reception timing from the repeater 30 (step S30). When the data from the repeater 30 is received (YES in step S30), the reply signal Ac is transmitted to the transmitter 10a (step S31). After that, the receiver 20 stores the data received from the repeater 30 in the register (step S32). The data stored in the register of the receiver 20 is output to the ECU 4 and used in the ECU 4 for monitoring and charge / discharge control of the battery unit 2.

As described above, in the present embodiment, the repeater 30 that relays the signal from the transmitter 10a and transmits it to the receiver 20 is provided. The repeater 30 is arranged at a position farther from the receiver 20 than the transmitter 10a and at a position where a transmission frequency in which the amplitude of the synthetic wave received by the receiver 20 is equal to or higher than the amplitude of the transmission wave exists. To. As a result, when the repeater 30 transmits the signal received from the transmitter 10a to the receiver 20, frequency hopping is performed to change the transmission frequency, so that the receiver 20 receives at at least one transmission frequency. The signal strength to be used can be amplified. As a result, the data from the transmitter 10a can be transmitted to the receiver 20 while suppressing the decrease in the signal strength received by the receiver 20.

<Modification 1>
In the above-described embodiment, an example is shown in which a dedicated repeater 30 that relays a signal from the transmitter 10a and transmits it to the receiver 20 is provided separately from the plurality of transmitters 10.

However, the distance from the receiver 20 is the above-mentioned reference distance Dth (the distance at which the amplitude change amount of the synthetic wave when the transmission frequency is changed by frequency hopping becomes the transmission wave amplitude "1", that is, the transmission path difference is shown in the figure. If there is a transmitter 10 that exceeds the reference value dth shown in 6, the transmitter 10 may be used as a repeater. As a result, the dedicated repeater 30 can be omitted, and an increase in cost and an increase in installation space can be suppressed.

FIG. 9 is a diagram schematically showing an example of the configuration of the battery control system 1A including the wireless communication system according to the modified example 1. In this battery control system 1A, 10 battery units 2 are arranged in two rows of 5 each. 110 transmitters 10 are provided corresponding to each of the 10 battery units 2.

Of the 10 transmitters 10, the leftmost transmitter 10b (hereinafter, also referred to as “second transmitter 10b”) is from the receiver 20 rather than the transmitter 10a (hereinafter, also referred to as “first transmitter 10a”). It is arranged at a distant position and at a position where there is a transmission frequency in which the amplitude of the synthetic wave received by the receiver 20 is equal to or higher than the amplitude of the transmitter wave.

Then, in the battery control system 1A, the dedicated repeater 30 is omitted, and the second transmitter 10b is used as the repeater. That is, the second transmitter 10b transmits the measured value of the battery voltage included in the battery unit 2 corresponding to itself to the receiver 20, and also receives the signal from the first transmitter 10a and transmits it to the receiver 20. do. At this time, the second transmitter 10b can amplify the signal strength received by the receiver 20 at at least one or more transmission frequencies by performing frequency hopping to change the transmission frequency.

Therefore, the signal from the first transmitter 10a is relayed by the second transmitter 10b and transmitted to the receiver 20 without providing a dedicated repeater, thereby suppressing a decrease in the signal strength received by the receiver 20. While doing so, the data from the first transmitter 10a can be transmitted to the receiver 20.

<Modification 2>
When the second transmitter 10b is used as a repeater as in the above-mentioned modification 1, the second transmitter 10b includes data received from the first transmitter 10a (hereinafter, also referred to as "first data DA1"). Both the data of the battery voltage included in the battery unit 2 corresponding to the second transmitter 10b (hereinafter, also referred to as "second data DA2") will be held. Therefore, if the transmission frequency to the receiver 20 is the same for all transmitters 10, the transmission chance between the first data DA1 and the second data DA2 is half that of the other data, and the communication reliability is reduced. There is a concern that it will decrease.

FIG. 10 is a diagram showing an example of transmission timing when the transmission frequency to the receiver 20 is the same for all transmitters 10 as a comparative example with respect to the present modification 1. FIG. 10 shows an example in which three data transmission timings are prepared for each data acquisition cycle (a period from one data acquisition timing to the next data acquisition timing) as the transmission frequency. In this case, the first transmitter 10a and the second transmitter 10b have three data transmission chances in one data acquisition cycle.

The first transmitter 10a may transmit one data (first data DA1) out of three data transmission opportunities to the second transmitter 10b. However, the second transmitter 10b transmits two data (first data DA1 and second data DA2) to the second transmitter 10b out of the three data transmission opportunities. Therefore, there is a concern that the transmission chance per data will be halved and the communication reliability will be lowered.

Therefore, in the present modification 2, the transmission frequency of the second transmitter 10b is increased more than the transmission frequency of the other transmitters 10.

FIG. 11 is a diagram showing an example of transmission timing according to the present modification 2. In the example shown in FIG. 10, an example in which the transmission frequency of the second transmitter 10b is double the transmission frequency of the other transmitter 10 is shown. More specifically, the transmission chance of the first transmitter 10a is prepared three times in each data acquisition cycle, while the transmission chance of the second transmitter 10b is prepared six times in each data acquisition cycle. .. Therefore, the first transmitter 10a may transmit one data (first data DA1) out of three data transmission opportunities to the second transmitter 10b. On the other hand, the second transmitter 10b may transmit two data (first data DA1 and second data DA2) to the second transmitter 10b out of the six data transmission opportunities. As a result, the transmission chances for each piece of data become uniform, and it is possible to suppress a decrease in communication reliability.

<Modification 3>
When the transmission frequency of the second transmitter 10b is increased more than the transmission frequency of the other transmitter 10 as in the above-mentioned modification 2, the communication schedule provided by the receiver 20 increases, and the communication of all data is completed. There is a concern that the time required to do so (hereinafter also referred to as "update time") will be extended. In order to prevent overcharging of the battery, prompt communication of battery information is indispensable, so it is required to shorten the update time as much as possible.

Therefore, in the present modification 3, the transmission of the first transmitter 10a to the receiver 20 is eliminated, and the communication with the first transmitter 10a is excluded from the communication schedule on the receiver 20 side. As a result, it is possible to prevent the update time from becoming long due to the increase in the transmission frequency of the second transmitter 10b.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present disclosure is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1,1A Battery control system, 2 Battery unit, 4 ECU, 6 Resin member, 8 Metal member, 10 Transmitter, 10a 1st transmitter (transmitter), 10b 2nd transmitter, 20 receiver, 30 repeater.

Claims (1)

A wireless communication system equipped with a transmitter, a repeater, and a receiver.
The transmitter transmits a radio signal to the repeater,
The repeater receives the radio wave signal from the transmitter and transmits it to the receiver.
The receiver receives a composite wave in which a plurality of transmission waves transmitted by the radio wave signal transmitted from the repeater via a plurality of routes are combined.
When transmitting the radio wave signal received from the transmitter to the receiver, the repeater changes the frequency of the radio wave signal within a predetermined range by frequency hopping.
The frequency of the radio wave signal in which the repeater is located farther from the receiver than the transmitter and the amplitude of the combined wave is equal to or higher than the amplitude of each of the plurality of transmitted waves is predetermined. A wireless communication system that is located within the range of the radio wave.

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