JP5190901B2 - COMMUNICATION DEVICE, COMMUNICATION SYSTEM, AND COMMUNICATION METHOD - Google Patents

Description

  The present invention relates to a communication system that transmits and receives data between a plurality of communication devices. In particular, the present invention relates to a communication device that can specify a generation point of received data with a simple configuration, a communication system including the communication device, and a communication method.

  In recent years, systems that connect a plurality of communication devices, assign functions to the communication devices, exchange data with each other, and perform various processes in cooperation have been used in various fields. For example, in the field of an in-vehicle LAN (Local Area Network) arranged in a vehicle, an ECU (Electronic Control Unit) is used as a communication device, and each ECU performs a specialized process to exchange data with each other. By exchanging, various functions are realized as a system.

  When processing is performed by exchanging data whose contents change from moment to moment among a plurality of communication apparatuses, each data has a valid period. When the control performed by the ECU in the field of in-vehicle LAN is related to safety, there is a possibility that a problem may occur if extremely old data is used.

  Patent Document 1 discloses a technique for minimizing data arriving after the arrival deadline time by a configuration in which each ECU controls transmission and reception of data in the order according to the priority based on the arrival deadline time of data. . In the technique disclosed in Patent Document 1, the arrival deadline time is an absolute time, and each ECU transmits data with a shorter time until the arrival deadline time using a time measurement unit that measures a synchronized reference time. I have to do it.

JP 2007-295081 A

  As shown in Patent Document 1, each ECU is configured to measure a synchronized reference time, so that each ECU receives data generation times measured by other communication devices, thereby generating data. Can be accurately recognized.

  There are various methods for synchronizing the time measured by time measuring means such as a timer provided in the communication devices connected to each other. However, in order to synchronize the time, a configuration in which each communication device performs a process of matching the time measured by its own clocking means with a reference time transmitted from one communication device, or each communication device has GPS (Global Positioning System) A configuration with a receiving function is required.

  The present invention has been made in view of such circumstances, and the generation time point of data received from another communication device can be determined with a simple configuration without synchronizing the time measured by the time measuring means included in each communication device. It is an object of the present invention to provide a communication device that can be specified accurately, a communication system including the communication device, and a communication method.

  The communication device according to the first invention is a timing device, a communication device that transmits and receives data via a communication line, and monitors the communication line, and other devices are not communicating via the communication line, When another device is about to start transmission, it is determined that the data can be transmitted by the communication means when it is possible to preferentially transmit data over the arbitration with the other device. And a means for obtaining a time difference between a generation time when the data is generated and a transmission start time at which transmission is determined by the transmission permission determination means and transmission of the data is started. Means for adding time difference information indicating a time difference to the data, means for specifying the reception start time based on the time measured by the time measuring means when the data with time difference information added is received by the communication means, and the time difference Based on the broadcast and the reception start time point, characterized by comprising a specifying means for specifying the time of generation of the data.

  In the communication device according to the second invention, when the transmission permission determination means determines that transmission is possible, the time measuring means acquires a data transmission start time, the acquired transmission start time, and the generation of the data Means for obtaining a time difference between time points, and time difference information indicating the obtained time difference is added to the data that has started transmission.

A communication device according to a third aspect of the present invention is a timekeeping means, a communication means for transmitting / receiving data via a communication line, and monitoring the communication line, and other devices are not communicating via the communication line, When another device is about to start transmission, it is determined that the data can be transmitted by the communication means when it is possible to preferentially transmit data over the arbitration with the other device. Means for determining whether to transmit, determining means for determining a transmission start time for transmitting data, means for determining a time difference between the determined transmission start time and the generation time at which the data is generated based on the time measuring means , Means for adding time difference information indicating the obtained time difference to the data; means for determining whether or not the transmission start time determined by the determination means has been reached; If it is determined that, means for attempting transmission time difference information added to the data and the data by the communication means, when received by the communication means additional data time difference information, the reception start time point the A means for specifying based on timekeeping by a time measuring means; a specifying means for specifying a data generation time based on the time difference information and the reception start time; and when the transmission availability determination means determines that the transmission is not possible, the determination means Then, the transmission start point at which transmission is started next is re-determined, the time difference is obtained again, and transmission is retried.

  When the communication device according to the fourth aspect of the invention receives the data to which the time difference information is added by the communication device, the communication device further transfers the data to another communication device by the communication device, and the data specified by the specifying device. Means for obtaining a time difference between the generation time of the data and the data transfer start time, and means for using the time difference information indicating the obtained time difference as time difference information added to the data to be transferred.

  A communication system according to a fifth aspect of the present invention is a communication system including a plurality of communication devices, wherein each communication device monitors a communication means for transmitting and receiving data via a communication line, and monitoring the communication line. If another device is not communicating via the line and the other device is about to start transmission, it is possible to preferentially transmit data over the arbitration with the other device. Sometimes, the transmission means for judging whether the data can be transmitted by the communication means, the generation time point when the data is generated, and the transmission is judged by the transmission possibility judgment means, and the transmission of the data is started. Means for obtaining a time difference between the transmission start time points, means for adding time difference information indicating the obtained time difference to the data, and when the data with time difference information added are received by the communication means, Serial communication system for the particular to means based on time measurement by the time measuring means, based on the time difference information and the reception start time point, comprising: a specifying means for specifying the time of generation of the data.

  A communication method according to a sixth aspect of the present invention is a method in which a communication device including a time measuring unit and a communication unit transmits and receives data via the communication line by the communication unit, the communication device monitors the communication line, and the communication line When other devices are not communicating via the network, and other devices are about to start transmission, when it is possible to preferentially transmit data over the arbitration with the other devices In addition, when it is determined that transmission of data by the communication unit is possible, and when it is determined that transmission is possible, the transmission of data is started, the transmission start point of the data is acquired by the timing unit, the acquired transmission start point, and A time difference between generation points at which the data is generated is obtained, and time difference information indicating the obtained time difference is added to the data that has been transmitted and transmitted.

  According to a seventh aspect of the present invention, there is provided a communication method in which a communication device including a timing unit and a communication unit transmits and receives data via a communication line by the communication unit. The communication device monitors the communication line, and the communication line When other devices are not communicating via the network, and other devices are about to start transmission, when it is possible to preferentially transmit data over the arbitration with the other devices In addition, it is determined that data transmission by the communication means is possible, a transmission start time point at which data is transmitted is determined, a time difference between the determined transmission start time point and a generation time point at which the data is generated is obtained, and the obtained time difference is indicated. The time difference information is added to the data, and it is determined whether or not the determined transmission start time has been reached. If it is determined that the transmission start time has been reached, the communication means adds the data and the data. Attempts to transmit time difference information, monitors the communication line to determine whether or not data transmission by the communication means is possible. It is characterized in that it is determined, the time difference is obtained again, and transmission is attempted again.

  In the first invention and the fifth invention, time difference information indicating a time difference between a generation time when data is generated and a transmission start time at which the transmission of the data is actually possible and transmission is started is added to the data. Is done. If the time difference from the start of transmission to the start of reception can be ignored, the time point past the time difference indicated by the time difference information from the reception start time point is the time point when the data is generated.

  In the second and sixth aspects of the invention, a transmission start time when data transmission is determined to be permitted and data transmission is started is obtained, and a time difference from the data generation time is obtained. As a result, a time difference is obtained based on information on the accurate transmission start time at which transmission is actually started, and is added to the data being transmitted and transmitted.

  In the third and seventh aspects of the invention, a data transmission start time is determined in advance, a time difference between the determined transmission start time and the data generation time is obtained in advance, and time difference information is added to the data. When transmission is attempted when transmission is reached and transmission is determined to be possible and transmission is started, the time difference represented by the time difference information already added to the data being transmitted is accurate. If it is determined that transmission is not possible and transmission is not started, the transmission start time is re-determined in accordance with the next transmission opportunity, time difference information is obtained again, and transmission is attempted. Thereby, even when it is difficult to add time difference information to the data being transmitted, it is possible to add time difference information that can specify an accurate generation time point with a simple configuration.

  In the fourth aspect of the invention, when transferring data received from another communication device, a time difference from the data generation time to the start of transfer is obtained and added based on the time measuring means in the communication device that performs the transfer. As a result, even when data is transferred via a plurality of communication devices, the communication device that has received the data determines the accurate data generation time based on the time measured by its own time measuring means based on the time difference information received together. It becomes possible to specify.

  According to the present invention, it is possible to accurately specify the generation time point of transmitted / received data with a simple configuration without synchronizing the time measured by the time measuring unit included in each communication device.

1 is a configuration diagram showing a configuration of an in-vehicle communication system in a first embodiment. 4 is a flowchart illustrating an example of a communication processing procedure in which the control unit of the ECU according to the first embodiment generates data and transmits the data together with time difference information. 6 is a flowchart illustrating an example of processing in which a control unit of an ECU or a control unit of a relay device in Embodiment 1 receives data and specifies a generation time point. 6 is a flowchart illustrating an example of a communication processing procedure when the control unit of the relay device in Embodiment 1 transfers data. It is explanatory drawing which shows the process in which the production | generation time of the data transmitted / received by ECU in Embodiment 1 and the relay apparatus is correctly specified by any ECU or relay apparatus. 6 is a flowchart illustrating an example of a communication processing procedure in which a control unit of an ECU according to Embodiment 2 generates data and transmits the data together with time difference information. 10 is a flowchart illustrating an example of a communication processing procedure when the control unit of the relay apparatus according to the second embodiment transfers data.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. In the following first and second embodiments, a case where the present invention is applied to an in-vehicle communication system including a plurality of ECUs arranged in a vehicle and transmitting / receiving data to / from each other will be described as an example.

(Embodiment 1)
FIG. 1 is a configuration diagram showing the configuration of the in-vehicle communication system in the first embodiment. The in-vehicle communication system according to the first embodiment includes ECUs 1, 1,... That are communication devices that transmit and receive data, relay devices 2a, 2b,. ,... And relay devices 2a, 2b,..., And communication lines 3a, 3b,.

  The ECUs 1, 1,... Are connected to different communication lines 3a, 3b,. The relay device 2a is connected to both the communication lines 3a and 3b, and relays data transmission / reception between the ECUs 1, 1,... Connected to the communication lines 3a and 3b, respectively. Similarly, the relay device 2b is connected to both the communication lines 3b and 3c, and relays data transmission / reception between the ECUs 1, 1,... Connected to the communication lines 3b and 3c, respectively.

  Each of the ECUs 1, 1,... Communicates via a control unit 10 that controls the operation of each component, a storage unit 11 that stores data necessary for control, a time measuring unit 12, and communication lines 3a, 3b,. The communication control part 13 which controls this is provided.

  The control unit 10 of the ECU 1 receives power supplied from a power supply device such as a vehicle battery and an alternator (not shown) to control the operation of each component.

  The storage unit 11 uses a volatile memory, and the control unit 10 is relayed by various information generated in the course of processing, measured values represented by signals input from sensors or relay devices 2a, 2b,. The stored data is temporarily stored in the storage unit 11.

  The timer 12 measures the passage of time by counting at a predetermined frequency. For example, the time measuring unit 12 measures an elapsed time from a predetermined reference time. The reference time point in the time measuring unit 12 may be a time point at which power is supplied, or an arbitrary time (for example, UTC; Coordinated Universal Time). The control unit 10 acquires time information at an arbitrary timing from the time measuring unit 12. Note that the time indicated by the time information acquired by the control unit 10 from the time measuring unit 12 is a local time in each of the ECUs 1, 1,... And does not need to be synchronized.

  The communication control unit 13 has a network controller chip and realizes communication via any one of the communication lines 3a, 3b,. .. And the relay devices 2a, 2b,... Transmit and receive data in accordance with a CAN (Controller Area Network) protocol. Therefore, the communication control unit 12 transmits and receives data via the communication lines 3a and 3b based on the CAN protocol. For example, the control unit 10 of the ECU 1 connected to the communication line 3a monitors the communication status on the communication line 3a by the communication control unit 12, determines whether or not it can transmit data, and can transmit it. Send data in case. Specifically, one ECU 1 connected to the communication line 3a communicates when other ECUs 1, 1,... Connected to the communication line 3a or the relay device 2a are not transmitting data. Data can be transmitted by the control unit 12. When any one of the ECUs 1, 1,... And the relay device 2a connected to the communication line 3a tries to start data transmission at the same time, any one can preferentially transmit data by arbitration. It is. Specifically, an arbitration field for arbitration is included in the header added to the head of data transmitted / received according to the CAN protocol, and arbitration is performed on the communication line 3a by a bit string in the arbitration field. Only one ECU 1 or relay device 2a that has won the arbitration can continue transmission. Further, when any of the ECUs 1, 1,... Connected to the communication line 3a and the relay device 2a transmit data via the communication line 3a, the other ECUs 1, 1 connected to the communication line 3a. ,... Or the relay apparatus 2a simultaneously receives data.

  The ECUs 1, 1,... Configured as described above are devices that can transmit data including numerical information of various physical quantities such as measured values, calculated values, and control values, or can be controlled by a microcomputer such as an engine and a brake. For example, one ECU 1 connected to the communication line 3a functions as an ABS (Antilock Brake System), and is connected to a sensor (not shown) that detects the rotational speed (wheel speed) of the wheel. The ECU 1 controls the brake based on the wheel speed detected via the sensor during braking of the vehicle, and also uses the measured value of the wheel speed as data to communicate with the other ECUs 1, 1,... And the relay device 2a via the communication line 3a. Send to.

  The ECUs 1, 1,... Transmit data including numerical information of various physical quantities such as measured values, calculated values, control values, etc., when data is generated, for example, when wheel speed measured values are detected via sensors. Information for identification is added after the data and transmitted. Specifically, the control unit 10 of the ECUs 1, 1,... Adds time difference information representing a time difference from the generation time point to the data transmission start time point. In addition, when it is necessary for the ECUs 1, 1,. It is specified as the generation time.

  The relay device 2a includes a control unit 20 that controls the operation of each component, a storage unit 21 that stores various types of information, a timing unit 22, and a communication unit 23 connected to the communication lines 3a and 3b. The internal configuration of the relay devices 2b, 2c,... Is the same as the internal configuration of the relay device 2a, and detailed description thereof is omitted.

  The control unit 20 uses an MPU (Micro Processing Unit), and is configured to receive power from a power supply device (not shown) such as an alternator of a vehicle or a battery to control the operation of each component.

  The memory | storage part 21 memorize | stores temporarily the data received from ECU1,1, ... using a volatile memory. Various kinds of information generated and used in the process of the control unit 20 are stored in the storage unit 21.

  The timer unit 22 measures the passage of time by counting at a predetermined frequency. For example, the timer unit 22 measures an elapsed time from a predetermined reference time. The reference time point may be a time point at which power is supplied, or may be an arbitrary time (for example, UTC), like the time measuring unit 12 in the ECUs 1, 1,. The control unit 20 acquires time information at an arbitrary timing from the time measuring unit 22. The time represented by the time information acquired from the timer unit 22 is the local time in the relay devices 2a, 2b,..., And the timer units 22 and timer units of the other relay devices 2a, 2b,. 12 need not be synchronized.

  The communication unit 23 realizes data transmission / reception with the ECUs 1, 1,... Connected via the communication lines 3a, 3b,. That is, data is transmitted and received according to the CAN protocol. The communication unit 23 has a plurality of ports and can connect to different communication lines 3a, 3b,... To transmit and receive data. The control unit 20 of the relay device 2a connected to the communication lines 3a and 3b monitors the communication status on the communication line 3a by the communication unit 23, determines whether or not it can transmit data, and can transmit the data. If so, data is transmitted via the communication line 3a. Similarly, the relay device 2a monitors the communication status on the communication line 3b by the communication unit 23, determines whether or not it can transmit data, and if it can transmit data, the data is transmitted via the communication line 3b. Send. Note that the communication unit 23 can simultaneously perform transmission and reception through different ports.

  The control unit 20 of the relay apparatuses 2a, 2b,... Configured as described above transfers data received from the ECUs 1, 1,... Via the communication unit 23 from other ports to the other ECUs 1, 1,. At the time of transfer, time difference information for specifying the generation time point of the data that is added to the data and transmitted is also transferred. However, the control unit 20 transfers the time difference information after changing it. Specifically, the control unit 20 adds the time difference from the reception start time to the transfer start time to the time difference indicated by the time difference information added to the received data to obtain the time difference from the generation time to the transfer start time, The time difference information added to the data to be transferred is changed to time difference information indicating the obtained time difference and then transferred.

  FIG. 2 is a flowchart illustrating an example of a communication processing procedure in which the control unit 10 of the ECUs 1, 1,... In Embodiment 1 generates data and transmits the data together with time difference information. In addition, the flowchart shown below shows the process by the control part 10 of one ECU1 connected to the communication line 3a. The processing by the control unit 10 of the other ECUs 1, 1,.

The control unit 10 detects a measurement value via a sensor, obtains a calculated value triggered by receiving other data, or obtains a control value to be controlled. Data including numerical information on the physical quantity is generated (step S11). At this time, the control unit 10 acquires the time point when the data is generated, that is, the data generation time point (Tc ⁽⁰⁾ ) by the time measuring unit 12 (step S12).

In the following description, a number is shown on the shoulder of the algebra representing each time point information, such as the data generation time point (Tc ⁽⁰⁾ ) in step S12 described above. The number is an arbitrary natural number (k) for explaining which device is the time information represented by the local time, and corresponds to the number of data relays. For example, “0 (zero)” at the data generation time point (Tc ⁽⁰⁾ ) in step S12 indicates that the time information is represented by the local time in the device in which the data is generated (the data starting device). Show. Note that the number shown on the shoulder does not have to be included in the transmitted / received time difference information.

  The control unit 10 attempts transmission of the data generated in step S11 by the communication control unit 13, and determines whether or not transmission has been successfully started (step S13). The control unit 10 has failed to start transmission because another ECU 1, 1,... Connected to the communication line 3a or the relay device 2a is communicating, or has started transmission of data but lost to arbitration. (S13: NO), the process returns to step S13 and waits until transmission can be started. In this case, the control unit 10 receives the data transmitted from the other ECUs 1, 1,... Or the relay device 2a by the communication control unit 13.

When the control unit 10 determines that the other ECUs 1, 1,... And the relay device 2a are not in communication and have started transmission by starting data transmission and winning arbitration (S13: YES), The transmission start time (Ts ⁽⁰⁾ ) is acquired by the time measuring unit 12 (step S14). Strictly speaking, the transmission start time (Ts ⁽⁰⁾ ) indicates the transmission time at the end of the arbitration field.

The control unit 10 calculates a time difference (Td ⁽⁰⁾ = Ts ⁽⁰⁾ −Tc ⁽⁰⁾ ) between the transmission start time (Ts ⁽⁰⁾ ) and the data generation time (Tc ⁽⁰⁾ ) ( In step S15), the time difference information indicating the time difference (Td ⁽⁰⁾ ) is added to the data being transmitted by the communication control unit 13 (step S16), the transmission is completed, and the process ends.

In this way, the control unit 10 obtains a time difference based on information on the accurate transmission start time (Ts ⁽⁰⁾ ) at which transmission is actually started, and is added to the data being transmitted and transmitted.

In addition, when the communication control part 13 performs a communication process according to a CAN protocol, addition of the time difference information in step S16 is implement | achieved by the following processes. When transmitting data, the communication control unit 13 adds header information including an arbitration field to the head of the data and adds trailer information indicating the end of data transmission to the end of the data. The header information includes the length from the header information to the end of the trailer information. Therefore, the time difference information is defined so as to be represented by a field having a predetermined length following the specific numerical information of the data. Arbitrary numerical information is entered in advance in the field representing the time difference information. The communication control unit 13 is configured to be able to rewrite the field representing the time difference information after the data transmission is started. Transmission start time controller 10 upon successful start of the transmission by the communication control unit 13 (Ts ⁽⁰⁾⁾ the time difference to get the (Td ⁽⁰⁾⁾ from the calculated, the communication control unit 13 for two hours difference information To rewrite. This makes it possible to add time difference information during transmission.

  3 is a flowchart illustrating an example of processing in which the control unit 10 of the ECUs 1, 1,... Or the control unit 20 of the relay apparatuses 2a, 2b,. The flowchart shown below shows processing by one ECU 10 connected to the communication line 3b. The processing by the control unit 20 of the other ECUs 1, 1,... And the relay devices 2a, 2b,.

  The control unit 10 determines whether or not data reception is started by the communication control unit 13 (communication unit 23 in the case of processing by the control unit 20 of the relay devices 2a and 2b) (step S21). When it is determined that the reception of data has not started (S21: NO), the control unit 10 returns the process to step S21.

When it is determined that the data reception has started (S21: YES), the control unit 10 acquires the reception start time (Tm ^(k) ) by the time measuring unit 12 (step S22). Then, the control unit 10 extracts time difference information indicating the time difference (Td ^(k−1) ) added to the data started to be received in step S21 (step S23), and the time difference (Td ⁽ Td ^{( k−1)} ) and the reception start time (Tm ^(k) ) acquired in step S22, the generation time of data represented by its own local time (Tc ^(k) = Tm ^(k) −Td ^(k−1) ) Is calculated (step S24), and the data generation time specifying process is terminated.

  Thereby, the control part 10 of ECU1 connected to the communication line 3b can specify the production | generation time point of the data produced | generated and transmitted, for example by ECU1 connected to the communication line 3a. Since the time difference information is a time difference from when data is actually generated to when transmission is actually started, the time point after the time difference from the reception start time is an accurate data generation time. Note that the numerical information k in the description of the flowchart of FIG. 3 corresponds to the number of relays from the device that generated the data.

  4 is a flowchart illustrating an example of a communication processing procedure when the control unit 20 of the relay apparatuses 2a, 2b,... In Embodiment 1 transfers data. In the flowchart shown below, the control unit 20 of one relay device 2a connected to the communication lines 3a and 3b receives data received from the ECU 1 connected to the communication line 3a and is connected to the communication line 3b. The processing when transferring to each device is shown. The processing when transmitting data transmitted from any of the devices connected to the communication line 3b to the ECUs 1, 1,... Connected to the communication line 3a is the same. The processing by the control unit 20 of the other relay apparatuses 2b, 2c,.

  The control unit 20 determines whether or not data reception is started by a port connected to the communication line 3a of the communication unit 23 (step S31). When it is determined that the data reception has not started (S31: NO), the control unit 20 returns the process to step S31, monitors the connected communication line 3a, and waits until the data reception starts. .

When it is determined that the data reception has started (S31: YES), the control unit 20 acquires the reception start time (Tm ^(k) ) by the time measuring unit 22 (step S32). The control unit 20 determines whether or not the reception of data has been completed (step S33). If it is determined that the data has not been completed (S33: NO), the process returns to step S33.

When the control unit 20 detects the trailer information by the communication unit 23 and determines that the reception of data is completed (S33: YES), the control unit 20 indicates the time difference (Td ^(k−1) ) added to the received data. Time difference information is extracted (step S34).

  When the received data is data to be transferred to the ECUs 1, 1,... And the relay device 3b connected to the communication line 3b through a port different from the received port, the control unit 20 communicates data transmission. The unit 23 tries to determine whether or not transmission has been successfully started (step S35). The control unit 20 fails to start transmission because another ECU 1, 1,... Connected to the communication line 3b or the relay device 2b is communicating, or has started transmission of data but lost to arbitration. If it is determined (S35: NO), the process returns to step S35 and waits until transmission can be started.

The control unit 20 has succeeded in starting the transmission because the other ECUs 1, 1,... Connected to the communication line 3b and the relay device 2b are not communicating and have started transmission of data and won arbitration. If it is determined (S35: YES), the transmission start time (Ts ^(k) ) is acquired by the time measuring unit 22 (step S36).

The control unit 20 adds a time difference (Td ^(k−1) ) indicated by the received time difference information to a time difference between the transmission start time (Ts ^(k) ) and the reception start time (Tm ^(k) ). ^(k) = Td ^(k-1) + (Ts ^(k) -Tm ^(k) )) is calculated (step S37), and the time difference information indicating the time difference (Td ^(k) ) is added to the data being transmitted. 23 (step S38), the transmission is completed, and the process is terminated.

The communication unit 23 performs a communication process according to the CAN protocol, and the process of adding time information in step S38 is performed as follows in the same manner as the communication control unit 13. The time difference information is represented by a field having a predetermined length following the specific numerical information of the data, and the control unit 20 puts arbitrary numerical information in advance in the field representing the time difference information. The communication unit 23 is configured to be able to rewrite the field representing the time difference information after starting transmission. The control unit 20 calculates the acquired by the time difference the transmission start time upon successful start of the transmission (Ts ^(k)) by the communication unit 23 (Td ^(k)), rewrite the communication unit 23 two hours difference information To instruct.

  FIG. 5 shows that the generation time point of data transmitted / received by the ECUs 1, 1,... And the relay devices 2a, 2b,. It is explanatory drawing which shows the process performed. FIG. 5 shows that time has passed downward. Note that the explanatory diagram of FIG. 5 shows an example in which data is generated by the ECU 1 connected to the communication line 3a and is transferred by the relay devices 2a, 2b,.

When data is generated by the ECU 1 connected to the communication line 3a, the generation time point acquired by the ECU 1 is Tc ⁽⁰⁾ . The data generated from the ECU 1 is transmitted at the time Ts ⁽⁰⁾ in the local time in the ECU 1, and the time difference indicated by the time difference information added at this time is Td ⁽⁰⁾ = Ts ⁽⁰⁾ −Tc ^{(0 )} .

The ECU 1 and the relay device 2a connected to the communication line 3a are connected in a bus shape, and transmit and receive data according to the CAN protocol. Therefore, if the ECU 1 has succeeded in starting data transmission at the time Ts ⁽⁰⁾ in its own local time, the relay device 2a simultaneously receives the data at the time Tm ⁽¹⁾ in the local time of the relay device 2a itself. Has started. Note that the control unit 20 of the relay apparatus 2a sets the data generation time in its own local time based on the time difference Td ⁽⁰⁾ indicated by the time difference information added to the received data as Tc ⁽¹⁾ = Tm ^(1). -Td ⁽⁰⁾ can be specified.

The relay device 2a transfers the data received from the ECU 1 to the ECUs 1, 1,... Connected to the communication line 3b and the relay device 2b. At this time, the control unit 20 of the relay device 2a as shown in the flowchart of FIG. 4 described above, it acquires the transmission start time Ts ⁽¹⁾ successful start of the transmission by the communication unit 23, a transmission start time Ts ^{(1 )} And the generation time Tc ⁽¹⁾ of the data, that is, the time difference Td ⁽⁰⁾ added to the received data, the reception start time Tm ⁽¹⁾ and the transmission start time Ts ⁽¹⁾ in itself. The time difference information indicating the time difference Td ⁽¹⁾ obtained by adding the time differences between the two is added and transmitted.

When the ECUs 1, 1,... Connected to the communication line 3b receive the data transferred by the relay device 2a, they start receiving the time difference Td ⁽¹⁾ indicated by the added time difference information and the data itself. Based on the time Tm ⁽²⁾ , the data generation time Tc ⁽²⁾ in the local time of the ECU 1 itself can be specified.

Similarly, the ECU 1 that has received the data relayed (transferred) k times also includes the time difference Td ^(k−1) indicated by the added time difference information and the time Tm ^(k) at which the data reception starts. Based on the above, it is possible to specify the data generation time Tc ^(k) in the local time of the ECU 1 itself. Regardless of how many times the data is relayed, the time difference indicated by the time difference information added to the received data is the time difference between the data generation time and the transmission (reception) start time represented by a predetermined frequency. is there. Therefore, even many times relayed data, the time difference Td than the reception start time point ^{Tm (k) (k-1} ) minute predated time Tc ^(k) is the data generation time.

As described above, the timekeeping unit 12 of the ECUs 1, 1,... And the timekeeping unit 22 of the relay devices 2a, 2b,... Are expressed in local time in each device even though they are not synchronized with reference to a predetermined absolute time. It is possible to specify the generation time. That is, as shown in FIG. 5, even if Tc ⁽⁰⁾ , Tc ^(1), and Tc ^(k) are represented by different numerical values, the generation times Tc ⁽⁰⁾ , Tc ^{( 1)} and Tc ^(k) correspond to simultaneous points as shown in FIG.

(Embodiment 2)
In the first embodiment, the control unit 10 of the ECUs 1, 1,... And the control unit 20 of the relay devices 2a, 2b,... Acquire the transmission start time and add it to the data being transmitted when the transmission is successfully started. The configuration is as follows. On the other hand, in the second embodiment, a transmission start time is determined in advance, and transmission is attempted after obtaining time difference information to be added to data.

  The configuration of the in-vehicle communication system in the second embodiment is the same as that in the first embodiment except for the details of the processing by the control unit 10 of the ECUs 1, 1,... And the details of the processing by the control unit 20 of the relay devices 2a, 2b,. It is the same. Hereinafter, the same reference numerals are assigned to components common to the first embodiment, and detailed description thereof is omitted, and details of processing by the control unit 10 of the ECUs 1, 1,..., Which are different points, and relay devices 2a, 2b, Details of the processing by the control unit 20 will be described with reference to a flowchart.

  FIG. 6 is a flowchart illustrating an example of a communication processing procedure in which the control unit 10 of the ECUs 1, 1,... In Embodiment 2 generates data and transmits the data together with time difference information. In addition, the flowchart shown below shows the process by the control part 10 of one ECU1 connected to the communication line 3a. The processing by the control unit 10 of the other ECUs 1, 1,. Of the processing procedures shown in the flowchart shown below, the same processing steps as those shown in the flowchart of FIG. 2 in the first embodiment are given the same step numbers, and detailed description thereof is omitted.

After acquiring the data generation time point (Tc ⁽⁰⁾ ) by the time measuring unit 12 (S12), the control unit 10 determines the scheduled time to start transmission, that is, the transmission start time point (Ts ⁽⁰⁾ ) (step S41). . Then, the control unit 10 calculates a time difference (Td ⁽⁰⁾ = Ts ⁽⁰⁾ −Tc ⁽⁰⁾ ) between the transmission start time (Ts ⁽⁰⁾ ) determined as a schedule and the data generation time (Tc ⁽⁰⁾ ). (Step S42).

The control unit 10 adds time difference information indicating the calculated time difference (Td ⁽⁰⁾ ) to the generated data (step S43), and compared with the time measurement by the time measurement unit 12, the transmission start time (Ts determined in step S41). ^It is determined whether or not ⁽⁰⁾ ) has been reached (step S44). If the control unit 10 determines that the transmission start time (Ts ⁽⁰⁾ ) has not been reached (S44: NO), the process returns to step S44.

If the control unit 10 determines that the transmission start time (Ts ⁽⁰⁾ ) has been reached (S44: YES), the communication control unit 13 attempts to transmit the data generated in S11, and whether or not the transmission start is successful. Is determined (step S45). The control unit 10 has failed to start transmission because another ECU 1, 1,... Connected to the communication line 3a or the relay device 2a is communicating, or has started transmission of data but lost to arbitration. (S45: NO), the process returns to step S41 to re-determine the transmission start time (Ts ⁽⁰⁾ ) for the next transmission attempt.

  When the control unit 10 determines that the other ECUs 1, 1,... And the relay device 2a are not communicating, start transmission of data, and have succeeded in arbitration, thereby successfully starting transmission (S45: YES). , The transmission is continued to complete the transmission, and the process is terminated.

In this case, the transmission start time added to the data is a predetermined time, but when the transmission is successfully started, the actual transmission start time is reached. Also in the second embodiment, specification of the generation time by the control unit 10 of the ECUs 1, 1,... That receives the data or the control unit 20 of the relay apparatuses 2, 2,... Is shown in the flowchart of FIG. This process is performed. Therefore, even when the data generation time point is specified based on the time difference information indicating the time difference (Td ⁽⁰⁾ ) in the processing procedure shown in the flowchart of FIG. 6, it is possible to correctly specify the data generation time point. is there.

  FIG. 7 is a flowchart illustrating an example of a communication processing procedure when the control unit 20 of the relay apparatuses 2a, 2b,... In the flowchart shown below, the control unit 20 of one relay device 2a connected to the communication lines 3a and 3b receives data received from the ECU 1 connected to the communication line 3a and is connected to the communication line 3b. The processing when transferring to each device is shown. The processing when transmitting data transmitted from any of the devices connected to the communication line 3b to the ECUs 1, 1,... Connected to the communication line 3a is the same. The processing by the control unit 20 of the other relay apparatuses 2b, 2c,.

  Of the processing procedures shown in the flowchart shown below, the same processing steps as those shown in the flowchart of FIG. 4 in the first embodiment are given the same step numbers, and detailed description thereof is omitted.

After extracting the time difference information indicating the time difference (Td ^(k−1) ) added from the received data (S34), the control unit 20 uses the communication line 3b by the port where the received data is different from the received port. When the data is to be transferred to the ECUs 1, 1,... Connected to the relay device 3b, the following processing is performed.

The control unit 20 determines a scheduled time for starting transmission (transfer), that is, a transmission start time (Ts ^(k) ) (step S51). Then, the control unit 10 adds the time difference (Td ^(k−1) ) indicated by the received time difference information to the time difference between the transmission start time (Ts ^(k) ) and the reception start time (Tm ^(k) ) determined as scheduled. The added time difference (Td ^(k) = Td ^(k-1) + (Ts ^(k) -Tm ^(k) )) is calculated (step S52).

The control unit 20 adds time difference information indicating the calculated time difference (Td ^(k) ) to the generated data (step S53), and compared with the time measurement by the time measurement unit 12, the transmission start time (Ts determined in step S51). ^(k) ) It is determined whether or not (step S54). When the control unit 20 determines that the transmission start time (Ts ^(k) ) has not been reached (S54: NO), the control unit 20 returns the process to step S54.

When it is determined that the transmission start time (Ts ^(k) ) has been reached (S54: YES), the control unit 20 attempts to transmit data by the communication unit 23, and determines whether the transmission has been successfully started (step S54). S55). The control unit 20 fails to start transmission because another ECU 1, 1,... Connected to the communication line 3b or the relay device 2b is communicating, or has started transmission of data but lost to arbitration. (S55: NO), the process returns to step S51 to re-determine the transmission start time (Ts ^(k) ) for the next transmission attempt.

  When the control unit 20 determines that the other ECUs 1, 1,... And the relay device 2b are not communicating, or have started transmission of data and have succeeded in arbitration, and thus have successfully started transmission (S55: YES) ), The transmission is continued to complete the transmission, and the process is terminated.

As a result, the transmission start time added to the data is a predetermined time, but when the transmission (transfer) is successfully started, the actual transmission start time is reached. Therefore, even when the data generation time point is specified based on the time difference information indicating the time difference (Td ^(k) ) calculated by the processing procedure shown in the flowchart of FIG. It is possible to specify.

  In the second embodiment, the transmission or transfer is attempted after data is generated including time difference information in advance. As a result, the communication control unit 13 and the communication unit 23 do not have to perform a process of rewriting the field representing the data time difference information during transmission.

  In the first and second embodiments, the time difference information indicating the time difference obtained from the time information acquired from the time measuring unit 12 of the ECUs 1, 1,... Or the time measuring unit 22 of the relay devices 2a, 2b,. did. However, the time difference information transmitted and received together with the data may be defined so as to indicate a time difference expressed in nanosecond units, for example. In this case, the timings in the timing units 12 of the ECUs 1, 1,... And the timing units 22 of the relay apparatuses 2a, 2b,. That is, even when the time measuring unit 12 in the ECU 1 connected to the communication line 3a measures time at 600 MHz and the time measuring unit 22 in the relay device 2a measures time at 3 GHz, the time difference information is transmitted and received in nanosecond units, and is controlled. The unit 10 or the control unit 20 can be converted into the same unit as the time information that can be acquired from the time measuring units 12 and 22.

  Further, the communication lines 3a, 3b,... In the first and second embodiments are configured to be communication lines conforming to the CAN protocol. However, the present invention does not limit communication via the communication lines 3a, 3b,... According to CAN. For example, if the present invention is applied to a communication device included in an in-vehicle communication system, a configuration capable of transmitting and receiving data based on a protocol such as LIN (Local Interconnect Network) or FlexRay (registered trademark) may be used.

  In the first and second embodiments, the ECUs 1, 1,... And the relay devices 2a, 2b,... Are connected to the communication lines 3a, 3b,. Thus, in communication via the communication lines 3a, 3b,..., A plurality of devices cannot transmit data at the same time, and when one device starts transmitting data, the other devices communicate with the communication lines 3a, 3b. ,... Were monitored simultaneously, and the time difference between the transmission start time and the reception start time could be ignored. However, the present invention is not limited to this, and a configuration in which the time difference between the transmission start time and the reception start time is not zero may be employed. This is not a problem when there is little influence on the accuracy required for the generation time point of data to be specified.

  The disclosed embodiments should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 ECU
DESCRIPTION OF SYMBOLS 10 Control part 12 Time measuring part 13 Communication control part 2a, 2b, ... Relay apparatus 20 Control part 22 Time measuring part 23 Communication part 3a, 3b, ... Communication line

Claims (7)

Timekeeping means,
A communication means for transmitting and receiving data via a communication line;
If the other device is not communicating via the communication line and the other device is about to start transmission, it prevails over the arbitration with the other device. When it is possible to transmit data to the transmission means for determining whether transmission of data by the communication means is possible,
Means for obtaining a time difference between a generation time when data is generated and a transmission start time at which transmission is determined by the transmission permission determination means and transmission of the data is started;
Means for adding time difference information indicating the obtained time difference to the data;
Means for specifying the reception start time based on the time measured by the time measuring means when the communication means receives the data with the time difference information added thereto;
And a specifying unit that specifies a data generation time based on the time difference information and the reception start time. Means for acquiring a transmission start time of data by the time measuring means when the transmission permission determination means determines that transmission is possible;
Means for obtaining a time difference between the acquired transmission start time and the data generation time;
The communication apparatus according to claim 1, wherein time difference information indicating the obtained time difference is added to the data that has started transmission. Timekeeping means,
A communication means for transmitting and receiving data via a communication line;
If the other device is not communicating via the communication line and the other device is about to start transmission, it prevails over the arbitration with the other device. When it is possible to transmit data to the transmission means for determining whether transmission of data by the communication means is possible,
Determining means for determining a transmission start time for transmitting data;
Means for obtaining a time difference between the determined transmission start time and the generation time when the data is generated based on the time measuring means ;
Means for adding time difference information indicating the obtained time difference to the data;
Means for determining whether or not the transmission start time determined by the determining means has been reached, based on the time measured by the time measuring means;
Means for attempting to transmit the data and the time difference information attached to the data by the communication means when it is determined that the transmission start time has been reached ;
Means for specifying the reception start time based on the time measured by the time measuring means when the communication means receives the data with the time difference information added thereto;
Based on the time difference information and the reception start time, comprising specifying means for specifying a data generation time ,
When said transmission determining means determines that impossible, to re-determine the transmission start time of starting the transmission to the next by said determining means, you said that you have to attempt again to send again seek time difference through Communication device. Means for transferring the data to the other communication device by the communication means when the communication means receives the data with the time difference information added thereto;
Means for obtaining a time difference between the generation time of the data specified by the specifying means and the transfer start time of the data;
4. A communication apparatus according to claim 1, further comprising means for setting time difference information indicating the obtained time difference to time difference information added to data to be transferred. In a communication system including a plurality of communication devices,
Each communication device
Timekeeping means,
A communication means for transmitting and receiving data via a communication line;
If the other device is not communicating via the communication line and the other device is about to start transmission, it prevails over the arbitration with the other device. When it is possible to transmit data to the transmission means for determining whether transmission of data by the communication means is possible,
Means for obtaining a time difference between a generation time when data is generated and a transmission start time at which transmission is determined by the transmission permission determination means and transmission of the data is started;
Means for adding time difference information indicating the obtained time difference to the data;
Means for specifying the reception start time based on the time measured by the time measuring means when the communication means receives the data with the time difference information added thereto;
And a specifying means for specifying a data generation time based on the time difference information and the reception start time. In a method in which a communication device comprising a time measuring means and a communication means transmits and receives data via a communication line by the communication means,
The communication device
If a communication line is monitored and another device is not communicating via the communication line, and another device is about to start transmission, it prevails over arbitration with the other device. When it is possible to transmit data, it is determined that transmission of data by the communication means is possible,
When it is determined that transmission is possible, transmission of data is started.
Obtain the transmission start time of the data by the time measuring means,
Find the time difference between the acquired transmission start time and the generation time when the data was generated,
A time difference information indicating the obtained time difference is added to the data that has been transmitted and transmitted. In a method in which a communication device comprising a time measuring means and a communication means transmits and receives data via a communication line by the communication means,
The communication device
If a communication line is monitored and another device is not communicating via the communication line, and another device is about to start transmission, it prevails over arbitration with the other device. When it is possible to transmit data, it is determined that transmission of data by the communication means is possible,
Decide when to start sending data,
Find the time difference between the determined transmission start time and the generation time when the data was generated,
Add time difference information indicating the obtained time difference to the data,
Determine whether the determined transmission start time has been reached,
If it is determined that the transmission start time has been reached, the communication means attempts to transmit the data and time difference information added to the data,
Monitoring the communication line to determine whether data can be transmitted by the communication means;
If it is determined that transmission of the data is impossible, re-determine the transmission start time to start transmission next,
A communication method characterized by re-determining the time difference and retrying transmission.

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