JP2007060400A - Method and system for controlling communication timing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a system for controlling communication timing for performing control so that pieces of data periodically output from a plurality of communication control units onto an on-vehicle LAN network are not mutually interfered in an on-vehicle LAN in which communication by an established time trigger protocol is not performed. <P>SOLUTION: In the on-vehicle LAN for connecting the plurality of communication control units via the on-vehicle LAN network, each communication control unit has a time counting means, one communication control unit connected to the on-vehicle LAN network is made to transmit synchronization data, each communication control unit is made to synchronize the time counting means in accordance with reception of the synchronization data and a transmission starting point of the data is adjusted so that the transmission starting point of the data becomes after transmission completion points of the data from other communication control units according to a value indicated by the time counting means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a communication timing control method and a communication timing control system for an in-vehicle LAN mounted on an automobile, and more specifically, a communication control unit (ECU: Electronic Control Unit) connected by an in-vehicle LAN such as a CAN bus. The present invention relates to a communication timing control method and a communication timing control system.

  FIG. 5 is a diagram illustrating a configuration of a basic in-vehicle LAN 90. The in-vehicle LAN 90 includes a plurality of ECUs 91A to 91D that comply with a standard such as CAN (Controller Area Network) (hereinafter referred to as a CAN bus). 92, and the loads 93A to 93C are controlled. In the CAN widely used as an in-vehicle LAN, the individual ECUs 91A to 91D operate asynchronously in time, and control an event trigger that operates in response to some event input from the outside.

  In addition, in the case of the ECUs 91A to 91D mounted on the automobile, the data Dpa and Dpb are often transmitted at a predetermined cycle, and the ECUs 93C and 91D receive these data to control the loads 93A to 93C. Can do.

  FIG. 6 shows an example of communication of each part in the in-vehicle LAN 90. As shown in FIG. 6, the ECU 91A outputs a transmission request Rpa for transmitting data Dpa to the CAN bus 92 at a data transmission cycle of, for example, every 5 ms, and the ECU 91B transfers data to the CAN bus 92, for example, at a data transmission cycle of every 10 ms. A transmission request Rpb for transmitting Dpb is output, and the data Dpa and Dpb are transmitted on the in-vehicle LAN 90. The ECUs 91 </ b> C and 91 </ b> D control the loads 93 </ b> A to 93 </ b> C by receiving data Dpa and Dpb transmitted via the CAN bus 92.

  By the way, in recent years, various protocols have been considered to prevent interference of transmission data by accurately controlling the communication timing in the in-vehicle LAN. FlexRay is specified to perform time-sharing control of communication within a communication cycle using a clock synchronized between nodes connected to the in-vehicle LAN. In Japanese translations of PCT publication No. 2004-536538 (Patent Document 1), in order to synchronize the clocks of the nodes connected by the LAN, the time based on the difference between the predicted reception time of the received message and the actual reception time is described. It is shown to correct the deviation.

Special table 2004-536538 gazette

  However, since the ECUs 91A and 91B are not synchronized with each other in CAN, depending on how the operation start timing is shifted after the power is turned on, data may be transmitted on the CAN in-vehicle LAN network 92 without interfering with each other. According to the operation timing of the ECUs 91A and 91B, interference may occur. In the case of the example in FIG. 6, the transmission timing of the data Dpa, Dpb,... Overlaps with the start of the transmission operation of the data Dpa2, Dpa4,. As a result, the data Dpa1, Dpa2,... From the ECU 91A are output at a timing deviating from a certain period.

  Further, since the data Dpa, Dpb,... May be transmitted from the ECUs 91A, 91B,... To the CAN in-vehicle LAN network even at non-periodic timing, there is a high possibility that the data transmission interference occurs. Therefore, a design is performed in which the number of ECUs 91A, 91B... Connected to the CAN in-vehicle LAN network 92 and the amount of data to be transmitted are limited so as not to interfere with each other for data transmission. That is, the communication load factor of the CAN in-vehicle LAN network 92 is limited so that communication is not disabled.

  Furthermore, it is also conceivable that the above-described data collision does not occur by using an in-vehicle LAN 90 that performs data communication by performing synchronized time management in each ECU 91A, 91B... Like FlexRay. .

  Further, what is described in Patent Document 1 is used in an in-vehicle LAN in which a time trigger protocol (TTP) such as FlexRay is defined, and is basically used in an in-vehicle LAN such as CAN that performs event trigger control. I could not. In the in-vehicle LAN in which the time trigger protocol is defined as in FlexRay, there is a problem that the design of the in-vehicle LAN becomes complicated because each connected ECU is registered in advance and the management becomes complicated.

  The present invention has been made in consideration of the above problems, and its purpose is to periodically output data from a plurality of communication control units to an in-vehicle LAN network in an in-vehicle LAN that does not perform communication using an established time trigger protocol. It is to provide a communication timing control method and a communication timing control system for controlling data to be transmitted so as not to interfere with each other.

In order to solve the above problems, the present invention provides:
In an in-vehicle LAN that connects a plurality of communication control units through an in-vehicle LAN network,
Each communication control unit has a time measuring means,
Send synchronization data to one communication control unit connected to the in-vehicle LAN network,
Each communication control unit is synchronized with the time measuring means along with the reception of the synchronization data,
According to the value indicated by the time measuring means, the data transmission start time is adjusted so that the data transmission start time is after the data transmission completion time from another communication control unit. Is provided.

  According to the above configuration, one communication control unit connected to the in-vehicle LAN network transmits synchronization data to a plurality of communication control units connected to the in-vehicle LAN network. The control unit can reliably synchronize the time measuring means with the reception of the synchronization data.

  In addition, when each communication control unit transmits data to the in-vehicle LAN network, the data transmission start time is adjusted so that the data transmission start time is after the data transmission end time from other communication control units. The communication control unit that transmits data at a constant cycle can intentionally shift the data transmission start time so that data that are periodically transmitted in subsequent communication do not interfere with each other.

  Therefore, since each communication control unit can transmit data in a predetermined cycle without receiving mutual interference, even if the communication load factor of the in-vehicle LAN network is increased, it is difficult for interference to occur. Become. In addition, the communication load factor in this specification has shown the average communication speed calculated | required from the data amount actually communicated with respect to the maximum communication speed of a vehicle-mounted LAN network.

  Basically, even in a CAN bus that performs event trigger control, communication control units that regularly transmit data can be synchronized with each other, whereby the in-vehicle LAN network can be used more efficiently. In addition, all communication control units connected to the in-vehicle LAN network have a high degree of freedom and can be used easily compared to an in-vehicle LAN such as FlexRay that manages communication start time.

  It is preferable that the synchronization data is periodically transmitted on the in-vehicle LAN network. As a result, the time measuring means of each communication control unit is periodically synchronized, and even if an error occurs in each time measuring means, synchronization can be achieved before the time is accumulated, resulting in errors in the time measuring means. Temporal inconsistency can be prevented in advance, and temporal inconsistency due to the error of the time measuring means can be prevented in advance. Further, it is preferable that the interval for transmitting the synchronization data is an integer multiple of the least common multiple of the data transmission cycle of data periodically transmitted in the communication timing control system.

  In the case where the communication control unit is an ECU and each of the plurality of ECUs transmits data on the in-vehicle LAN network at a predetermined data transmission cycle, and each ECU has a common divisor in the data transmission cycle, each ECU It is preferable to shift the transmission start time by a time different from the time that is the greatest common divisor of the data transmission cycle. In other words, if the transmission start time of data from each ECU is the greatest common divisor of the data transmission cycle, it is preferable to avoid this because interference occurs in the periodically transmitted data.

The present invention also provides:
In an in-vehicle LAN composed of a plurality of communication control units and an in-vehicle LAN network that connects each communication control unit so as to be able to transmit and receive
One communication control unit connected to the bus comprises synchronization time transmission means for transmitting synchronization data on the bus,
A time measuring means for each communication control unit to measure time;
Synchronization time setting means for synchronizing the time measurement means with reception of the synchronization data;
Transmission timing adjusting means for adjusting the data transmission start time so that the data transmission start time is after the data transmission completion time from another communication control unit according to the value indicated by the time measuring means. A communication timing control system is provided.

  Since the synchronization time transmitting means transmits synchronization data at a predetermined time using its own time measurement means, and the simultaneous time setting means synchronizes the time measurement means with the reception of the synchronization data, all the time The measuring means can be reliably synchronized at the same time. Also, since the data transmission start time is adjusted so that there is no interference using a synchronized time measuring means, delays due to interference can be eliminated periodically, and the communication load factor of the bus is increased. However, it is possible to make it difficult for communication to occur.

  The communication control unit that transmits the synchronization data may only transmit the synchronization data. However, the communication control unit that performs other signal processing may also transmit the synchronization data. preferable.

  In addition, even if the in-vehicle LAN basically performs event trigger control, the communication control unit that periodically transmits data includes the time measurement unit, the synchronization time setting unit, and the transmission timing adjustment unit. The communication control unit connected to the in-vehicle LAN can be provided with a synchronous time transmission means to prevent the data transmitted periodically from interfering with each other, thereby realizing an efficient use of the bus. .

  It is preferable that the synchronization time transmitting means transmits synchronization data periodically. That is, since the time measurement means in each communication control unit can be synchronized before the error of the time measurement means in each communication control unit accumulates, each communication control unit can more accurately determine the data transmission start time. Therefore, it is possible to prevent time mismatch caused by errors in the time measuring means. Further, it is preferable that the interval for transmitting the synchronization data is an integer multiple of the least common multiple of the data transmission cycle of data periodically transmitted in the communication timing control system.

  When the communication control unit is an ECU and each of the plurality of ECUs transmits data on the bus at a predetermined data transmission cycle, and when there is a common divisor in the data transmission cycle of these ECUs, the transmission timing adjustment Preferably, the means shifts the transmission start time of each ECU by a time different from the time that is the greatest common divisor of the data transmission cycle. In other words, if the transmission start time of data from each ECU is the greatest common divisor of the data transmission cycle, it is preferable to avoid this because interference occurs in the periodically transmitted data.

  As described above, according to the present invention, even in an in-vehicle LAN system that basically performs event trigger control, data can be transmitted and received using a bus efficiently. For this reason, even if the communication load factor of the bus is increased, interference does not easily occur, and it is possible to make it difficult for a communication disabled state due to data interference to occur.

  FIG. 1 is a diagram showing a configuration of a communication timing control system 1 according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of signals transmitted and received in the communication timing control system 1.

  A communication timing control system 1 according to the present embodiment is connected to a plurality of communication control units 2 (for example, ECUs, and hereinafter referred to as ECUs 2A, 2B,. The measured value data Da and Db obtained from the sensors 4A and 4B are periodically transmitted to the in-vehicle LAN network 3, and the load 5A is based on the measured value data Da and Db. , 5B, 5C are controlled.

  The ECU 2 includes, for example, a control unit 10 that controls the entire unit and performs load control, a CAN controller 11 that is connected to the control unit 10 and performs control based on the CAN communication protocol, and data for the in-vehicle LAN network 3. CAN driver 12 that performs transmission / reception, time measuring means (timer) 13 that measures time so as to measure the transmission timing for transmitting data to the in-vehicle LAN network 3, and objects to be monitored or controlled (sensors 4A and 4B, electrical load 5A) To 5C etc.). Further, the ECU 2C includes synchronization time transmission means 15 that monitors the value indicated by the timer 13 and periodically transmits the time adjustment data Ds at predetermined intervals.

  The in-vehicle LAN network 3 is a bus that conforms to the CAN standard as an example of an in-vehicle LAN that basically controls event triggers, and is referred to as a CAN bus in the following description. However, the present invention is not limited to the in-vehicle LAN network being a CAN bus, and may be an in-vehicle LAN such as LIN and FlexRay. In addition, the present invention can transmit a synchronized signal even in an in-vehicle LAN network such as LIN or CAN in which a time trigger protocol is not defined, so that a problem such as a collision does not occur. Can be controlled.

  The sensors 4A and 4B measure the physical quantity of each part of the automobile that changes from moment to moment, and the measured value data Da of the sensor 4A that measures a relatively fast change value is, for example, CAN every 5 ms. It is transmitted on the bus 3. On the other hand, the measurement value data Db of the sensor 4B is transmitted onto the CAN bus 3 every data transmission cycle of 10 ms, for example.

  The control means 10 includes, for example, a CPU and a basic program (not shown) executed by the CPU. The CPU constituting the control means 10 shown in the present embodiment is all adjusted by resetting the timer 13 in accordance with the timing of receiving the time adjustment data Ds transmitted on the CAN bus 3. Synchronization time setting program (synchronization time setting means) Pa for synchronizing the timer 13 in the ECU 2 and a transmission timing adjustment program for outputting the transmission requests Ra and Rb so as to adjust the data transmission start time according to the value indicated by the timer 13 (Transmission timing adjusting means) Pb can be executed.

  The CAN controller 11 performs control conforming to the CAN communication protocol to output data Da, Db, Ds inputted from the CAN bus 3 side to the control means 10 or measured value data Da, Db given from the control means 10. And the transmission request Ra, Rb... Of the synchronization data Ds from the synchronization time transmitting means 15 are input and the data Da, Db... Are output to the CAN bus 3 side. The CAN transceiver 12 is physically connected to the CAN bus 3 to input / output data.

  The timer 13 measures time and is configured to be able to set a value indicating time by a control signal from the control means 10. The timer 13 shown in the present embodiment outputs a count value c that counts so that the value is incremented by 1 every 1 ms. This count value c is at least an interval at which the synchronization data Ds is transmitted (this embodiment). In this case, 100 ms) or more has a number of digits that can be counted. Note that the count value c indicated by the timer 13 may be a more detailed time control with a short time interval of 1 ms or less as a minimum unit.

  The synchronization time transmission means 15 monitors the count value indicated by the timer 13 in the ECU 2C in which the synchronization time transmission means 15 is mounted, and when the count value reaches a value corresponding to 100 ms, the time adjustment data Ds. The transmission request Rs is output to the CAN controller 11. The transmission interval of the time adjustment data Ds is set to an integral multiple of the least common multiple (10 ms in this embodiment) of the data transmission cycle of all data Da and Db periodically transmitted on the CAN bus 3. Is preferred.

  The data D on the CAN bus 3 shown in FIG. 2 includes the synchronization data Ds transmitted when the count value c of the timer 13 is 0, and from the time when the count value is 2, 7, 12, 17. The measurement value data Da1, Da2,... Are output every predetermined data transmission interval of 5 ms, and the measurement value data Db1, Db2,... Are output every predetermined data transmission interval of 10 ms from the time when the count value is 4, 14, 24. The transmission start time points of the data Da1, Da2,... Db1, Db2,.

  FIG. 3 is a diagram for explaining an example of the operations of the synchronization time setting program Pa and the transmission timing adjustment program Pb. The synchronization time setting program Pa includes step S1 waiting for the time adjustment data Ds and step S2 for resetting the time of the timer 13 when the reception of the synchronization adjustment data Ds is confirmed.

  The process of step S1 is repeated until the synchronization data Ds is received. When the synchronization data Ds is received, the process jumps to step S1 after executing the process of step S2. That is, when the synchronization time setting program Pa is executed by the control means 10 in all ECUs 2 connected to the CAN bus 3, all the timers 13 are synchronized with the reception of the synchronization data Ds. Note that the synchronization time setting program Pa shown in FIG. 3 is illustrated for explaining the present invention, and does not limit the present invention.

  FIG. 4 is a diagram for explaining an example of the operation of the transmission timing adjustment program Pb. In FIG. 4, S10 is a step of determining whether or not the count value c indicated by the timer 13 is a value indicating the data transmission start time. The processing in step S10 is repeated until the count value c reaches the data transmission start time.

  Here, the data transmission start time will be described with reference to FIG. As shown in FIG. 2, the transmission start time of the measurement value data Da1 is set to a time 2 ms behind the time (count value c = 0) when the synchronization data Ds is received. This means that when the transmission of the synchronization data Ds takes 1 ms or more and less than 2 ms, it can be determined that the transmission of the synchronization data Ds is completed at the time when the count value c = 2.

  Similarly, if the transmission of each measured value data Da1, Da2,..., Db1, Db2,... Takes 1 ms or more and less than 2 ms, each measured value data Da1, Da2,. , Db1, Db2,... Can be considered to be after the transmission completion time of the previous data Ds, Da1, Da2,. It is important that the delay time t is not the greatest common divisor (5 ms in this embodiment) of the transmission period of each measurement value data Da1, Da2,..., Db1, Db2,. It is. Thereby, it is possible to prevent the measurement value data Da1, Da2,..., Db1, Db2.

  In the example shown in FIG. 2, the transmission start points of the measurement value data Da1, Da2,... Are 2, 7, 12,. Similarly, the transmission start points of the measured value data Db1, Db2,... Are 4, 14, 24,.

  Returning to FIG. 4 again, S11 is a step of outputting the transmission request Ra (or Rb) and the measured value data Da (or Db) when it is determined in step S10 that the transmission start time is reached. Here, the transmission request Ra (or Rb) is output to the control means 10 when other event trigger data is output on the CAN bus 3, the measured value data Da (or Db). This is because it is necessary to delay the transmission of.

  S12 is a step for obtaining the next transmission start time. In this embodiment, a calculation is performed to add a data transmission cycle of 5 ms (or 10 ms) to the current transmission start time. Then, the process jumps to step S10. As a result, the measured value data Da1, Da2,... (Or Db1, Db2,...) Can be transmitted on the CAN bus 3 every predetermined data transmission cycle.

  The transmission timing adjustment program Pb shown in FIG. 4 is shown for explaining the present invention, and does not limit the present invention.

  Further, in each of the above-described embodiments, for the sake of simplicity, an example in which the minimum unit of the count value c of the timer 13 is 1 ms is shown. However, in order to use the CAN bus 3 more efficiently, the timer Needless to say, it is preferable to set the minimum unit of the interval measurable by 13 to 1 ms or less and to set the delay time t in more detail.

  In particular, since the timers 13 mounted on the ECUs 2A, 2B,... Are frequently configured and kept synchronized with the reception of the synchronization data Ds, the time lag due to individual differences of the timers 13 is almost zero. This makes it possible to manage data transmission start time more strictly.

It is a figure which shows the structure of the communication timing control system which concerns on this invention. It is a figure explaining the transmission timing control method which concerns on this invention. It is a figure explaining a part of said communication timing control method. It is a figure which shows another part of the said communication timing control method. It is a figure explaining the structure of the conventional vehicle-mounted LAN. It is a figure explaining the control method of the communication timing in the said vehicle-mounted LAN.

Explanation of symbols

1 Communication Timing Control System 2 Communication Control Unit (ECU)
3 In-vehicle LAN network 13 Time measurement means 15 Synchronization time transmission means Pa Synchronization time setting program (same time setting means)
Pb transmission timing adjustment program (transmission timing adjustment means)
t Delay time

Claims (6)

In an in-vehicle LAN that connects a plurality of communication control units through an in-vehicle LAN network,
Each communication control unit has a time measuring means,
Send synchronization data to one communication control unit connected to the in-vehicle LAN network,
Each communication control unit is synchronized with the time measuring means along with the reception of the synchronization data,
According to the value indicated by the time measuring means, the data transmission start time is adjusted so that the data transmission start time is after the data transmission completion time from another communication control unit. .   The communication timing control method according to claim 1, wherein the synchronization data is periodically transmitted on the in-vehicle LAN network.   In the case where the communication control unit is an ECU and each of the plurality of ECUs transmits data on the in-vehicle LAN network at a predetermined data transmission cycle, and each ECU has a common divisor in the data transmission cycle, each ECU The communication timing control method according to claim 1, wherein the transmission start time is shifted by a time different from a time that is the greatest common divisor of the data transmission cycle. In an in-vehicle LAN composed of a plurality of communication control units and an in-vehicle LAN network that connects each communication control unit so as to be able to transmit and receive
One communication control unit connected to the in-vehicle LAN network includes synchronization time transmitting means for transmitting synchronization data on the in-vehicle LAN network,
A time measuring means for each communication control unit to measure time;
Synchronization time setting means for synchronizing the time measurement means with reception of the synchronization data;
Transmission timing adjusting means for adjusting the data transmission start time so that the data transmission start time is after the data transmission completion time from another communication control unit according to the value indicated by the time measuring means. Communication timing control system.   The communication timing control system according to claim 4, wherein the synchronization time transmitting unit periodically transmits synchronization data.   In the case where the communication control unit is an ECU and each of the plurality of ECUs transmits data on the in-vehicle LAN network at a predetermined data transmission cycle, and when there is a common divisor in the data transmission cycle of these ECUs, the transmission 6. The communication timing according to claim 4, wherein the timing adjusting means shifts a transmission start time of each ECU by a time different from a time that is the greatest common divisor of the data transmission cycle. Control system.

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