Communication systems and communication methods

Abstract

This technology provides the ability to continue in-vehicle communication regardless of the vehicle's power status. [Solution] The communication system 10 that performs in-vehicle communication based on the Ethernet standard comprises a communication bus 11 and a plurality of communication devices that transmit data via the communication bus 11. The plurality of communication devices include communication devices that do not participate in in-vehicle communication depending on the vehicle's power state, and depending on the vehicle's power state, the system takes a state in which the maximum number of participating communication devices communicates. The plurality of communication devices each have a holding unit that holds in advance their own transmission order according to the maximum number of participants, and a communication unit that transmits data when the number of times counted each time a predetermined period of no communication has elapsed reaches its own transmission order.

Description

Technical Field

[0001] The present invention relates to a technology in which a plurality of communication devices perform in-vehicle communication according to the Ethernet (registered trademark) standard.

Background Art

[0002] Patent Document 1 discloses a technology for providing a signal quality indicator of a signal received via a communication bus in a vehicle communication network using the 10BASE-T1S standard of Ethernet (registered trademark).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Depending on the power state of the vehicle, some communication devices stop operating, so the number of communication devices participating in in-vehicle communication changes depending on the power state. If the number of participating communication devices and the transmission order in in-vehicle communication are set according to the transition of the power state, there is a risk of synchronization deviation or communication stoppage every time the power state transitions.

[0005] An object of the present invention is to provide a technology that can continue in-vehicle communication regardless of the power state of the vehicle.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the present invention is a communication system that performs in-vehicle communication based on the Ethernet standard, comprising a communication bus and a plurality of communication devices that transmit data via the communication bus. The plurality of communication devices include communication devices that do not participate in in-vehicle communication depending on the vehicle's power state, and depending on the vehicle's power state, the communication devices that participate in in-vehicle communication will communicate with the maximum number of participants, and each of the plurality of communication devices has a holding unit that holds its own transmission order in advance according to the maximum number of participants, and a communication unit that transmits data when the number of times counted each time a predetermined period of no communication has elapsed has reached its own transmission order.

[0007] Another aspect of the present invention is a communication method in which multiple communication devices perform in-vehicle communication based on the Ethernet standard via a communication bus. This communication method includes the steps of: each of the multiple communication devices pre-maintaining its own transmission order corresponding to the maximum number of participating communication devices that have the most participants in the in-vehicle communication; and a communication device among the multiple communication devices that participates in the in-vehicle communication counting periods of no communication for a predetermined time each time a predetermined period has elapsed, and transmitting data when the number of no communication periods reaches its own transmission order. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technology that enables continuous in-vehicle communication regardless of the vehicle's power status. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows the functional configuration of the communication system in the embodiment. [Figure 2] This diagram shows the communication process in a communication system in chronological order. [Figure 3] This diagram illustrates the data transmission process according to the vehicle's power status. [Figure 4] This is a flowchart of the communication process performed by the communication system in the embodiment. [Modes for carrying out the invention]

[0010] Figure 1 shows the functional configuration of the communication system 10 in the embodiment. Each function of the communication system 10 can be configured in hardware terms with circuit blocks, memory, and other LSIs, and in software terms with system software and application programs loaded into memory. Therefore, it will be understood by those skilled in the art that each function of the communication system 10 can be implemented in various ways by hardware alone, software alone, or a combination thereof, and is not limited to any one of these. The communication system 10 is installed in a vehicle, and the vehicle may be capable of autonomous driving.

[0011] The communication system 10 includes a communication bus 11, a first communication device 12a, a second communication device 12b, and a third communication device 12c (referred to as "communication device 12" when not distinguished). The communication bus 11 implements in-vehicle communication using the Ethernet® standard, and in particular, implements communication based on the 10BASE-T1S standard. Multiple communication devices 12 are connected to the communication bus 11.

[0012] Although three communication devices 12 are shown in Figure 1, there are actually four or more, and these are sometimes referred to as nodes. The communication devices 12 are installed, for example, in an ECU (Electronic Control Unit) mounted in a vehicle, and transmit and receive data used by the ECU via the communication bus 11.

[0013] Here, the communication method of the communication system 10 will be explained with reference to a new drawing. Figure 2 is a diagram showing the communication in the communication system 10 in chronological order. In Figure 2, the processes are shown in chronological order from left to right. Node 0 corresponds to the first communication device 12a, node 1 corresponds to the second communication device 12b, node 2 corresponds to the third communication device 12c, and node 3 corresponds to the fourth communication device (not shown). Each node stores its own pre-set transmission order. The transmission order is an integer indicating the order from node 0 to node 3.

[0014] Node 0 transmits a beacon signal 40 indicating the starting point. Next, Node 0 waits for a predetermined period of no communication, known as TO42 (Transmit Opportunity), to elapse. The duration of TO42 is predetermined. TO42 is used to recognize the transmission order. Node 0 measures the time of no communication starting from the beacon signal 40, counts one TO42, and recognizes that it is its transmission order. Once Node 0 determines that it is its transmission order, it executes a data transmission process, sending a commit signal 44, data 46, and an end signal 48.

[0015] Next, node 1 waits until the second TO50 has elapsed. Node 1 determines that it is its turn to transmit after TO42 and TO50 have elapsed, and executes the data transmission process, sending the commit signal 52, data 54, and end signal 56.

[0016] Next, Node 2 is in an off state and does not participate in in-vehicle communication, so it does not perform any transmission processing. Since Node 2 does nothing, TO58 is passed in Node 2's transmission sequence.

[0017] Next, node 3 counts TO42, TO50, TO58, and TO60, and having counted four TOs, determines that it is the fourth node in the transmission order and executes the data transmission process. Node 0 counts four TOs, which is the total number of participating nodes, and transmits beacon signal 40. Beacon signal 40 indicates that the TO count has been reset and the transmission order starts again from zero. This repeats the data transmission process for each node. As shown in node 2 of Figure 2, the transmission order does not have to be in the order of participation from 1st to 5th.

[0018] The main battery and the auxiliary battery provided in the vehicle create three power supply states depending on whether the ignition switch is on or off. In the first power supply state, it is a parked state where the ignition switch is off and the accessory is also off, and the auxiliary battery supplies leakage current to only some ECUs. In the first power supply state, since the vehicle is parked, the communication device 12 participating in communication is the least. In the second power supply state, the engine is not running and the accessory is on, the auxiliary battery supplies power to some ECUs, and the communication device 12 participating in communication is more than in the first power supply state. In the third power supply state, both the main battery and the auxiliary battery are supplying power with the ignition switch on, and the communication device 12 participating is the most. The number of all communication devices 12 participating in in-vehicle communication in the third power supply state is called the maximum participation number.

[0019] In this way, in in-vehicle communication, the number of communication devices 12 participating in communication changes due to the transition of the power supply state. If the communication system 10 sets the participation number and the transmission order for the communication device 12 according to each power supply state, these settings will be implemented for the communication device 12 at the timing of the transition of the power supply state. However, there may be a deviation in the setting timing due to various factors, and there is a risk of instantaneously causing an inconsistency in the values set for the communication device 12. To prevent such a state, for example, there is a method of setting the communication device 12 in a state where the network is once stopped and then restarting it. However, a state where communication becomes impossible occurs by stopping the network.

[0020] Therefore, the communication system 10 sets, for each of the communication devices 12, the maximum participation number of the communication devices 12 participating in communication on the communication bus 11 and its own transmission order according to the maximum participation number, and executes in-vehicle communication assuming that the communication devices 12 with the maximum participation number are participating in any power supply state.

[0021] Return to FIG. 1. The first communication device 12a is set as the coordinator determined in the first transmission order. The first communication device 12a includes a holding unit 20, a determination unit 22, and a communication unit 24. The holding unit 20 preliminarily holds the maximum number of communication devices participating in communication on the communication bus 11 and its own transmission order corresponding to the maximum number of participants. The holding unit 20 holds the first transmission order.

[0022] Since the first communication device 12a is a coordinator, it serves as a starting point for starting the count of the transmission order. The first communication device 12a is connected to the auxiliary battery so as to be able to receive power, and is a control device operable in the first power state which is a parked state. For example, the ECU having the first communication device 12a may be an ECU having a function of monitoring the auxiliary battery, may be an ECU capable of releasing the door lock, and in any case, it is an ECU operable during parking and is an ECU that operates first at startup even if it shifts to the sleep state during parking.

[0023] The determination unit 22 determines the timing for transmitting a signal by the communication unit 24. The determination unit 22 determines that it is the timing for transmitting a beacon signal at the timing when the first communication device 12a starts up from the sleep state. Further, the determination unit 22 determines the timing for transmitting a beacon signal by the communication unit 24 based on the maximum number of participants. The communication unit 24 receives the determination result of the determination unit 22 and transmits a beacon signal. The communication unit 24 transmits the beacon signal 40 when the number of uncommunicated periods counted every time a predetermined time elapses reaches the maximum number of participants, or when the first communication device 12a is started up from the sleep state.

[0024] The determination unit 22 counts a predetermined period of no communication from the time the beacon signal is transmitted as one period of no communication. When the determination unit 22 counts the first period of no communication, it determines that it is time for the first communication device 12a to transmit data. The communication unit 24 receives the determination result from the determination unit 22 and executes the data transmission process. The communication unit 24 transmits data when the number of times it has counted the period of no communication reaches its transmission order after a predetermined time has elapsed. The data transmission process transmits a commit signal, data, and an end signal as a set.

[0025] The second communication device 12b is assigned the second transmission order. Communication devices 12 whose transmission order is second or later are sometimes called followers. The second communication device 12b has a holding unit 26, a determination unit 28, and a communication unit 30. The holding unit 26 has in advance the maximum number of communication devices participating in communication on the communication bus 11 and its own transmission order corresponding to that maximum number of participants. The holding unit 26 has the second transmission order.

[0026] The determination unit 28 counts the period of no communication twice from the time it receives the beacon signal, and determines that it is time to send data from the second communication device 12b. The communication unit 30 receives the determination result from the determination unit 28 and executes the data transmission process.

[0027] The third communication device 12c is assigned the third transmission order. The third communication device 12c has a holding unit 32, a determination unit 34, and a communication unit 36. The holding unit 32 stores in advance the maximum number of communication devices participating in communication on the communication bus 11 and its own transmission order corresponding to that maximum number of participants. The transmission order held by the holding unit 32 is third.

[0028] The determination unit 34 counts the period of no communication three times from the time it receives the beacon signal, and then determines that it is time to send data from the third communication device 12c. The communication unit 36 ​​receives the determination result from the determination unit 34 and executes the data transmission process.

[0029] Note that the fourth and subsequent communication devices 12, which are not shown, have the same configuration as the second communication device 12b and the third communication device 12c, except that they hold a different transmission order.

[0030] Figure 3 is a diagram illustrating the data transmission process according to the vehicle's power supply status. Figure 3(a) shows the data transmission process for the first power supply status, Figure 3(b) shows the data transmission process for the second power supply status, and Figure 3(c) shows the data transmission process for the third power supply status. Figures 3(a) to 3(c) show the processes arranged chronologically from left to right. In Figure 3, the maximum number of participants in the communication device 12 is 6, but in reality, it is not limited to 6.

[0031] In the first power state shown in Figure 3(a), the number of participants in communication device 12 is 2. Nodes 2 through 5 do not participate in the communication. Node 0, which corresponds to the first communication device 12a, transmits a beacon signal to start the TO count from zero. The transmission of the beacon signal is triggered when node 0, which is the coordinator, is woken from sleep mode, or when the number of TOs reaches the maximum number of participants.

[0032] Node 0 counts TO once and executes the data transmission process. Next, Node 1 receives the beacon signal, counts TO twice, and then executes the data transmission process. Nodes 2 through 5 do not participate in the communication, so four TOs pass. Node 0 counts TO six times, and since the number of TOs has reached the maximum number of participants, it transmits the beacon signal. By transmitting the beacon signal, Node 0 and Node 1 repeat the communication.

[0033] In the second power state shown in Figure 3(b), the number of participants in the communication device 12 is 4. Node 0 transmits a beacon signal and starts counting TOs from zero. Node 0 counts TO once and executes the data transmission process. Next, Nodes 1 to 3 each receive the beacon signal and count the number of TOs, and when the number of TOs reaches their transmission order, they execute the data transmission process. Nodes 2 and 3, which are newly joining the communication, can join the communication by starting to count TOs after receiving the beacon signal after being powered up, so they do not need to be aware of the power state.

[0034] Nodes 4 and 5 do not participate in the communication, so two TOs (Timeouts) are completed. Node 0 counts the TOs to six and sends a beacon signal because the number of TOs has reached the maximum number of participants. This causes communication from Node 0 to Node 3 to be repeated.

[0035] In the third power state shown in Figure 3(c), the number of participants in the communication device 12 is at its highest, with a maximum of 6 participants. Node 0 transmits a beacon signal to start the TO count from zero. Nodes 0 through 5 each count the number of TOs after a predetermined period of no communication has elapsed since the beacon signal was transmitted. When the number of TOs reaches their transmission order, they execute the data transmission process.

[0036] In this way, each communication device 12 maintains its own transmission order according to the maximum number of participants, allowing communication to continue regardless of the power state, assuming that the maximum number of communication devices 12 are participating in the communication, without requiring reconfiguration for each power state. Since the communication devices 12 can participate in the communication at any time regardless of the power state, they can freely transition between sleep and wake-up states.

[0037] Figure 4 is a flowchart of the communication process performed by the communication system 10 of the embodiment. The process shown in Figure 4 is repeated from the start when it reaches the end. The first communication device 12a, which is the coordinator, transmits a beacon signal (S10). Initially, the beacon signal is transmitted when the device is woken up from sleep mode.

[0038] Multiple communication devices 12 count periods of no communication for a predetermined time as periods of no communication (S12), and after receiving a beacon signal, determine if the number of periods of no communication has reached their transmission turn (S14). When the first communication device 12a counts one period of no communication, it determines that it is its transmission turn (Y in S14) and executes the data transmission process (S16). The first communication device 12a determines if the number of periods of no communication has reached the maximum number of participants (S18).

[0039] If the number of periods without communication has not reached the maximum number of participants (N in S18), the multiple communication devices 12 count the number of periods without communication (S12). If the multiple communication devices 12 determine that the number of periods without communication has not reached their transmission turn (N in S14), they continue to count the number of periods without communication (S12) and wait for their transmission turn.

[0040] When multiple communication devices 12 each execute their own data transmission process in their respective transmission order (S16), the first communication device 12a determines that the number of non-communication periods has reached the maximum number of participants (Y in S18), terminates this process, and the process is repeated from step 10.

[0041] The present disclosure has been explained above based on the examples described. The present disclosure is not limited to the examples described above, and various modifications such as design changes can be made based on the knowledge of those skilled in the art.

[0042] For example, in the embodiment, the holding units of the communication device 12 are shown to hold the maximum number of participants and the transmission order, respectively, but the embodiment is not limited to this. The holding unit of the communication device 12 acting as a coordinator may hold the maximum number of participants and the transmission order, while the holding unit of the communication device 12 acting as a follower may hold only the transmission order. [Explanation of Symbols]

[0043] 10 Communication system, 11 Communication bus, 12 Communication device, 12a First communication device, 12b Second communication device, 12c Third communication device, 20 Holding unit, 22 Determination unit, 24 Communication unit, 26 Holding unit, 28 Determination unit, 30 Communication unit, 32 Holding unit, 34 Determination unit, 36 Communication unit, 40 Beacon signal, 42 TO, 44 Commit signal, 46 Data, 48 End signal.

Claims

1. A communication system that performs in-vehicle communication based on the Ethernet standard, Communication bus and The system comprises a plurality of communication devices that transmit data via the aforementioned communication bus, The multiple communication devices include communication devices that do not participate in in-vehicle communication depending on the vehicle's power state, and depending on the vehicle's power state, the communication devices that do participate in in-vehicle communication will communicate with the maximum number of participants. Multiple communication devices, A holding unit that pre-stores its own transmission order according to the maximum number of participants, A communication system characterized by having a communication unit that transmits data when the number of times it counts each predetermined period of time during which it does not communicate reaches its own transmission order.

2. The communication system according to claim 1, characterized in that one of the plurality of communication devices is set as the coordinator designated for the first transmission order and transmits a beacon signal indicating that the count of the number of non-communication periods starts from zero.

3. The communication system according to claim 2, characterized in that the coordinator transmits the beacon signal when the number of non-communication periods reaches the maximum number of participants.

4. The communication system according to claim 2 or 3, characterized in that the coordinator is connected to an auxiliary power supply unit and is a control device that can operate in a parked state.

5. A communication method in which multiple communication devices perform in-vehicle communication based on the Ethernet standard via a communication bus, Each of the multiple communication devices pre-maintains its own transmission order corresponding to the maximum number of participants, which is the largest number of communication devices participating in the in-vehicle communication. A communication method characterized in that, among a plurality of communication devices, the communication device participating in in-vehicle communication counts each predetermined period of time during which no communication takes place, and transmits data when the number of such periods reaches its own transmission order.

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