JP2003264567A - Can communication method and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To synchronize data communication between particular nodes among a plurality of nodes about CAN communication method and system. <P>SOLUTION: Control units such as a revolutionary ECU (electronic control unit) 10, etc., respectively having a CAN controller 30 and sensors such as a G sensor 18, a yaw rate sensor 22 are connected to one another through a CAN bus 26. The revolutionary ECU 10 needed to perform VSC control and sensors 18 to 24 are set as a node having a high priority over data transmission on the CAN bus 26. The revolutionary ECU 10 is made to transmit a trigger frame for requesting the transmission of a control parameter of VSC control to the CAN bus 26 every fixed cycle. The respective sensors 18 to 24 are made to perform A/D conversion processing of their own physical quantity whenever a trigger frame is received and to transmit data obtained as a result of the A/D conversion processing to the CAN bus 26. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention allows communication between a plurality of nodes connected to each other via a CAN bus.
The present invention relates to an AN communication method and system, and more particularly to a CAN communication method and system suitable for synchronizing data communication between specific nodes.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-2001-142
As disclosed in Japanese Patent Publication No. 794, a CAN that is connected to each other via a CAN bus and performs data communication between a plurality of nodes each having a CAN controller unit.
Communication systems are known. CAN communication is a protocol for performing bidirectional serial communication via a differential serial bus.

In such a CAN communication system, each node sends out the data with the identification ID code of its own node to the CAN bus. If the CAN bus is not occupied by the data from another node when the data is transmitted, the data sent from the node is CAN.
It flows on the bus and is received by another node. On the other hand, when the CAN bus is occupied by the data from another node, the data to be sent out from the node is waited by the CAN controller unit. When there is only one node on which data waits, the data flows on the CAN bus when the CAN bus becomes empty. On the other hand, when there are a plurality of nodes for waiting data, the data of the node having the highest priority order based on the ID code among these nodes flows through the CAN bus before other waiting data.

[0004]

By the way, among the plurality of nodes connected to each other via the CAN bus, there is a node that wants to receive data from another node at a desired timing. For example, in order to appropriately control the turning behavior of the vehicle, it is necessary to detect the yaw rate, acceleration, and vehicle steering angle that are actually occurring in the vehicle at each point in a short cycle. In a vehicle in which various control units that control wheel locks and various sensors such as yaw rate, acceleration, and steering angle are configured by a CAN communication system, a control unit that controls turning behavior can control the yaw rate of the vehicle at desired timing. Become the node you want to receive.

However, in CAN communication, C
Of the nodes connected to the AN bus, the data of the node having a high priority based on the ID code easily flows through the CAN bus,
Since it is difficult for the data of the node having the low priority to flow through the CAN bus, even if the data of one node is received by another node, the received data may not be the latest. In this respect, the data communication between the nodes in the CAN communication is asynchronous. Therefore, even if one node wants to receive the latest data by another node at a desired timing, such data may not be received. Therefore, the control response of the one node may be deteriorated.

The present invention has been made in view of the above points, and an object thereof is to provide a CAN communication method and system capable of synchronizing data communication between specific nodes among a plurality of nodes. And

[0007]

The above-mentioned object is defined in claim 1.
, Connected to each other via a CAN bus,
A CAN communication method for performing communication between a plurality of nodes each having a CAN controller, wherein the trigger is to transmit data when the first node requires data from at least one second node. A first step of transmitting a frame toward the CAN bus; and, when the second node receives the trigger frame from the first node, transmits data to be transmitted by the C
The second step of transmitting towards the AN bus is achieved.

Further, the above-mentioned objects are connected to each other via a CAN bus as described in claim 3, and C
CAN with multiple nodes having AN controller
In the communication system, the first node transmits a trigger frame to transmit the data toward the CAN bus when the data is required by the at least one second node, and the first node transmits the trigger frame. The second node CA, when receiving the trigger frame from the first node, transmits data to be transmitted to the CAN bus.
N communication system.

In the invention described in claims 1 and 3, the first
Node sends a trigger frame towards the CAN bus when it needs data by at least one second node, and the second node receives the trigger frame from the first node. In this case, the data to be transmitted is transmitted to the CAN bus. According to this configuration,
Since the second node transmits data by using the frame transmission by the first node as a trigger, data communication between those specific nodes can be synchronized.

In this case, as described in claim 2, in the CAN communication method according to claim 1, each of the first node and the second node has a priority on the CAN bus among all nodes. If it is a relatively high node, and as described in claim 4, in the CAN communication system according to claim 3, each of the first node and the second node is the node among all the nodes. Given that the nodes on the CAN bus have a relatively high priority, the data from those nodes is C
Since it becomes easy to flow through the AN bus, it is possible to reliably ensure the synchronization of data communication between the first node and the second node.

According to a fifth aspect of the present invention, in the CAN communication system according to the third or fourth aspect, the second node samples data at the time of receiving the trigger frame from the first node. Then, the data obtained as a result may be transmitted to the CAN bus as data to be transmitted.

If the second node transmits data only when the trigger frame from the first node is received, the second node transmits the data when the trigger frame is not received. Since it will not be transmitted, a situation will occur in which a node including the first node that needs the data cannot receive the data by the second node, which adversely affects the system.

Therefore, as described in claim 6, in the CAN communication system according to any one of claims 3 to 5, the first node transmits the trigger frame at a predetermined cycle, and If the second node transmits the data to be transmitted toward the CAN bus even when the state in which the trigger frame is not received continues beyond the predetermined period, the second node is the second node. Since the data is surely transmitted without receiving the trigger frame by the first node, the node that needs the data by the second node never receives the data, and the control based on the data does not occur. It can be executed reliably.

In this case, as described in claim 7, in the CAN communication system according to claim 6, the second node distinguishes between the case where the trigger frame is received and the case where the trigger frame is not received. If the data to which the trigger is added is transmitted to the CAN bus, it is possible to cause the node that requires the data from the second node to execute fine-grained control according to the reception state of the second node. it can.

Further, although the data communication is synchronized between the first node and the second node as described above, the second node responds to the transmission of the trigger frame by the first node. If no data is received by the node for a long time, it can be determined that a failure has occurred in the second node or the communication system between them.

Therefore, as described in claim 8, in the CAN communication system according to any one of claims 3 to 7, the first node transmits the trigger frame to the C
After transmitting to the AN bus, when the state in which data from the second node is not received continues for a predetermined time,
It may be determined that a failure has occurred in the second node or the communication system.

As described in claim 9, in the CAN communication system according to any one of claims 3 to 8,
If the first node is a control unit that controls the turning behavior of the vehicle, and the second node is a sensor that outputs a parameter necessary for controlling the turning behavior of the vehicle. , Because the data communication between the control unit of the turning behavior and the sensor is synchronized, CA
Even in N communication, it is possible to reliably prevent the responsiveness of the turning behavior control from being deteriorated.

[0018]

1 is a block diagram of a CAN communication system according to an embodiment of the present invention. CAN of this embodiment
The communication system is a system installed in a vehicle. Various types of vehicle control are performed in the vehicle. Specifically, control for stabilizing the turning behavior of the vehicle (hereinafter,
This control is called VSC (Vehicle Stability Control) control (turning behavior control), and control for ensuring vehicle acceleration, straightness, and turning stability (hereinafter, this control is referred to as TRC (Tr
action control) and control for preventing wheel lock (hereinafter this control is ABS (Antilock B)
rake system) called control)) is performed.

As shown in FIG. 1, the vehicle has a VSC electronic control unit (hereinafter referred to as a turning behavior EC) for executing VSC control.
U) 10, a TRC electronic control unit (hereinafter referred to as a traction ECU) 12 that executes TRC control,
Further, it has an ABS electronic control unit (hereinafter referred to as a lock ECU) 14 that executes ABS control. Further, the vehicle is a sensor for realizing various vehicle controls, specifically, a G sensor 18 that outputs a signal according to an acceleration generated in the vehicle front-rear direction and a vehicle width direction, and a signal according to a wheel steering angle. A steering angle sensor 20 for outputting, a yaw rate sensor 22 for outputting a signal according to a yaw rate generated around a vertical axis of the center of gravity of the vehicle, a wheel speed sensor 24 provided for each wheel and outputting a signal according to a wheel speed, and the like. Have

The turning behavior ECU 10 includes a G sensor 18, a steering angle sensor 20, a yaw rate sensor 22, and a wheel speed sensor 2.
The running state of the vehicle is detected based on the output signals of various sensors such as 4 and the like, and as a result, when the vehicle has a tendency to skid, a braking force is applied to the front wheels or the rear wheels so that the tendency is mitigated. Control the yawing of the vehicle. Such VS
According to the C control, the turning behavior of the vehicle is stabilized.
The traction ECU 12 detects the throttle opening degree, etc., and as a result, when there is a possibility that excessive torque is generated at the time of starting or accelerating, the traction ECU 12 applies a braking force to the drive wheels so as not to generate the torque or outputs the engine output. Or suppress the generator output. According to such TRC control, a driving force corresponding to the road surface condition is secured even on a low μ road or the like. Further, the lock ECU 14 detects the wheel speed, the presence / absence of a brake operation, and the like, and as a result, when the wheels tend to lock during braking, controls the braking force that can be generated on each wheel so that the wheel does not lock. . According to such ABS control, the wheels are prevented from being locked and the braking performance is sufficiently ensured, so that the steering wheel operability and the vehicle stability are reliably maintained.

The turning behavior ECU 10, the traction ECU 12, the lock ECU 14, and other control units of the vehicle, the G sensor 18, the steering angle sensor 20, the yaw rate sensor 22, and the wheel speed sensor 24 are used for the communication bus 2.
They are connected to each other via 6. Communication bus 26 is 2
This bus has a book communication line and is used for differential serial communication. The various control units incorporate a controller area network (hereinafter, referred to as CAN) controller 30 together with a controller for executing corresponding vehicle control, a RAM, and a ROM. Further, various sensors also incorporate a CAN controller 30 together with a detection unit that outputs analog data corresponding to a corresponding physical quantity and the like, and a circuit for converting a signal from the detection unit into digital data.

Hereinafter, the communication bus 26 will be referred to as the CAN bus 26, and various control units and various sensors connected to each other via the CAN bus 26 will be collectively referred to as nodes. When communicating with other nodes, each node transmits the transmission data via the driver of the CAN controller 30. That is, in such a configuration, the node is
Data is bidirectionally exchanged with other nodes via the CAN controller 30 and the CAN bus 26.

FIG. 2 is a diagram showing the data contents of one frame transmitted by each node constituting the CAN communication system of this embodiment. One frame transmitted as data by each node is, for example, as shown in FIG. 2, an ID field storing the identification number of its own node, a control field storing the data length of the data field, and 0 to 8
It is composed of a data field that stores data to be transmitted that is variable in bytes, and a CRC field that stores data for performing a cyclic code redundancy check. Each node has a transmission rate of, for example, 500 kbps, and when the data length of the data field is 8 bytes, one frame data of about 120 bits is 250 μs.
It is possible to send and receive with a degree.

The ID field of 1-frame data is provided in the higher order of the data to be transmitted, and the higher order bit (eg 11 bits) is the identification number of its own node (eg 3 digit hexadecimal number) (11 digit). It is represented by being converted into binary data. The identification number in the ID field of each node is different from the identification numbers of other nodes.

FIG. 3 is a diagram showing the transmission principle of the CAN communication system. In CAN communication, data communication between a plurality of nodes is performed via the serial CAN bus 26. Therefore, the data that can flow in the CAN bus 26 at a time is the same as the data of only one of the plurality of nodes. Become. Therefore, in the CAN communication, when a plurality of nodes should each perform data transmission, the data sent to the CAN bus 26 from each node at random do not overlap with each other and flow through the CAN bus 26, that is, Data of only one node is CAN bus 2
It is necessary to perform arbitration for the data flowing through the CAN bus 26 so that the data flows through 6.

As described above, the data transmitted by each node is given its own identification number. Therefore, in CAN communication, the data flowing through the CAN bus 26 is determined based on the identification number attached to the higher order of the data transmitted by each node. That is, the smaller the identification number, the greater the number of low levels “0” that appear from the upper bits of the ID field, while the larger the identification number, the more easily the high level “1” appears in the upper bits. Data from a small node has a low level “0” on the higher side. The CAN controller 30 of each node has a low level “0” via the CAN bus 26.
In addition to determining whether or not the data has been supplied, the own identification number is compared with the identification number from another node in the situation where the own data is to be transmitted. Then, if the identification number of the other node involved in reception is larger than that of its own, it continues its own data transmission, while if it is smaller, it executes a process of interrupting its own data transmission and waiting.

For example, as shown in FIG. 3, the data A transmitted from a certain node is transferred to the CAN bus 26 at time t1.
If another node is in a timing to send out the data B to the CAN bus 26 before the transmission of the data A is completed (time t2), the data B is transmitted to the CAN controller 30 of its own node. Waited in. Then, when the transmission of the data A is completed at the time t3, the data B, which has been waiting for the transmission from the other node, starts flowing through the CAN bus 26.

Under these circumstances, the data C and the data D are directed to the CAN bus 26 before the transmission of the data B is completed.
Is at the timing to be transmitted (time t4 and t5), the data C and D are CA of the respective nodes.
The N controller 30 waits. Then, when the transmission of the data B is completed at time t6, the data C and the data D start flowing through the CAN bus 26. However, among the nodes transmitting the data C and D, the node having the larger identification number is the node having the smaller identification number. When the data D or C is received, the transmission of its own data C or D is interrupted and made to wait. Therefore, when the identification number of the node transmitting the data D is smaller than that of the node transmitting the data C, after the transmission of the data B is completed, both data C,
Data D from a node having a smaller identification number among D starts to flow on the CAN bus 26 before data C and is received by each node. Then, at the time t7, when the transmission of the data D is completed, the waiting data C is transferred to the CAN bus 2
Start to flow 6.

As described above, according to the arbitration function of the CAN controller 30 included in each node, the C-number is based on the identification number of the node attached to the data transmitted by each node.
The data flowing on the AN bus 26 is determined. Specifically, when a plurality of data are to be transmitted via the CAN bus 26 almost at the same time, the data of the node having the smallest identification number among the data flows through the CAN bus 26. Therefore, according to the CAN communication system,
Even in situations where multiple data should be sent over the CAN bus 26 at approximately the same time, ensure that only one data is
It is possible to send the data to the AN bus 26 and have a plurality of nodes receive the data at the same time. Thereby, the communication load can be reduced and the communication efficiency can be improved.

By the way, in order to surely stabilize the turning behavior of the vehicle and properly perform the VSC control, the parameters such as the acceleration and the yaw rate which occur in the vehicle at each time point in a short cycle (for example, 12 ms) are set. It is necessary to detect and apply an appropriate braking force to the vehicle. That is, the turning behavior ECU 10 needs to receive the output signals of the G sensor 18, the yaw rate sensor 22 and the like at a desired timing.

However, in the CAN communication described above, the data with the smaller identification number is CAN
Easy to flow on the bus 26. That is, the data from the node having the smaller identification number has a higher priority than the data from the node having the larger identification number on the CAN bus 26. Therefore, if sensors used for VSC control, such as the G sensor 18 and the yaw rate sensor 22, transmit sensor outputs at random, even if the turning behavior ECU 10 receives output signals from these sensors, the received data is not received. It may not be the latest version. Therefore, in the CAN communication system according to the present exemplary embodiment, in the configuration in which each sensor randomly outputs an output, there may be a problem that proper VSC control cannot be performed.

FIG. 4 is a diagram schematically showing exchange of data communication between the turning behavior ECU 10 and each of the sensors 18 to 24 in the CAN communication system of this embodiment.
In order to avoid the above-mentioned inconvenience, the system of the present embodiment is
The identification numbers of the nodes (specifically, the turning behavior ECU 10, the G sensor 18, the steering angle sensor 20, the yaw rate sensor 22, and the wheel speed sensor 24) necessary for the VSC control of the vehicle are made smaller than the other nodes. , The priority on the CAN bus 26 is made relatively high. For example, CAN bus 26
Turning behavior E among all nodes connected to each other via
The CU 10 is set to the node having the highest priority, and the sensors 18 to 24 are set to the nodes having the second to fifth priority, respectively.

Then, as shown in FIG. 4, the turning behavior ECU
Reference numeral 10 sends a command requesting transmission of acceleration, yaw rate, steering angle, and wheel speed, which are control parameters of VSC control, to the CAN bus 26 at a constant cycle T1 (for example, 12 ms) as a trigger frame. In addition, each sensor 18-24
When it receives a trigger frame from the turning behavior ECU 10, it starts and executes the A / D conversion process for its own physical quantity, and the digital data obtained as a result is CAN.
Send to bus 26.

In such a system, the turning behavior ECU
10 has the highest priority on the CAN bus 26, the trigger frame transmitted by the turning behavior ECU 10 is
After the transmission is done, it can be received by each sensor 18-24 in a short time. Further, each of the sensors 18 to 24 does not A / D-convert the physical quantity at random, but A / D according to the trigger frame of the turning behavior ECU 10.
Perform D conversion processing. Furthermore, since the priority of each sensor 18-24 on the CAN bus 26 is the second highest next to the turning behavior ECU 10, the data transmitted by each sensor 18-24 will be transmitted in a short time after the transmission. Turning behavior EC
U10 can be received.

Therefore, according to this embodiment, even if the nodes for VSC control are connected to each other via the CAN bus 26, the turning behavior ECU 10 causes the G sensor 1 to operate.
It is possible to receive the latest output signal of each of the output signals of the steering angle sensor 20, the yaw rate sensor 22, and the wheel speed sensor 24 at a desired timing. Therefore, according to the system of the present embodiment, since the data communication between the turning behavior ECU 10 and the respective sensors 18 to 24 can be synchronized, it is possible to surely prevent the responsiveness of the VSC control from being deteriorated. Therefore, the turning behavior can be appropriately performed.

FIG. 5 shows a flow chart of a control routine executed in the turning behavior ECU 10 of the present embodiment in order to realize the above function. The routine shown in FIG. 5 is a routine that is started each time the processing is completed. When the routine shown in FIG. 5 is started, first, step 100
The process of is executed.

In step 100, a trigger frame for requesting the G sensor 18, the steering angle sensor 20, the yaw rate sensor 22, and the wheel speed sensor 24 to transmit the acceleration, the steering angle, the yaw rate, and the wheel speed is sent to the CAN bus 26. The process of transmitting the data is executed. As described above, the turning behavior E
Since the priority of the CU 10 on the CAN bus 26 is the highest, when the processing of this step 100 is executed, at most 250 μs later, that is, at the present time, CA
Immediately after the transmission of the data flowing through the N bus 26 is completed,
The trigger frame by the turning behavior ECU 10 starts flowing on the CAN bus 26 and is received by each node.

At step 102, it is judged whether or not each data is returned from all the sensors 18 to 24.
Since the CAN bus 26 is a serial bus and only data from only one node among all the nodes flows at one time, the turning behavior ECU 10 transmits the trigger frame and then receives all the data from the sensors 18 to 24. Takes about several ms. As a result, sensor 1
When it is determined that all the data of 8 to 24 have not been returned, the processing of step 104 is executed next.

In step 104, the above step 100
At, it is determined whether or not a predetermined time T2 (<T1) has elapsed after the transmission of the trigger frame was started. still,
The fixed time T2 is set to, for example, 2 ms, which is longer than the time to receive all the respective data of the sensors 18 to 24 after the transmission of the trigger frame is started and shorter than the period T1 of the trigger frame. . As a result, if it is determined that the fixed time T2 has not elapsed, then the process of step 102 is executed. On the other hand, when it is determined that the fixed time T2 has elapsed, a failure occurs in which data cannot be transmitted to the sensors 18 to 24 even though the trigger frame is transmitted, or
Although the sensors 18 to 24 transmit data to the trigger frame, the communication system fails, or the turning behavior of the turning behavior ECU 10 or the sensors 18 to 24.
It can be determined that there is an abnormality in the data according to 24. Therefore, if such a determination is made, the next step 10
The process of 6 is executed. In step 106, the sensor 1
8-24 or turning behavior ECU10 and each sensor 18-24
It is determined that a failure has occurred in the communication system or the like connecting with.
In this case, the warning lamp may be turned on and a warning may be given to alert the vehicle driver to that effect.

On the other hand, if it is determined in step 102 that all the data from the sensors 18 to 24 have been returned, and if the process of step 106 has ended, then the process of step 108 is executed. In step 108, the acceleration by the G sensor 18 and the steering angle sensor 2
Based on the wheel steering angle of 0, the yaw rate of the yaw rate sensor 22, and the wheel speed of the wheel speed sensor 24,
A process for executing VSC control for stabilizing the turning behavior of the vehicle is executed. When the processing of step 108 is executed, if the vehicle has a tendency to skid thereafter, braking force is applied to the front wheels or the rear wheels of the vehicle so that yawing that alleviates the tendency is generated.

In step 110, the above step 100 is performed.
After the transmission of the trigger frame is started, it is determined whether or not the above-mentioned constant period T1 has elapsed. This step 11
The process of 0 is repeatedly executed until the fixed period T1 elapses. As a result, if it is determined that the fixed period T1 has elapsed, the routine of this time is ended, and the trigger frame is transmitted again in step 100.

According to the routine shown in FIG. 5, the turning behavior ECU 10 can send the trigger frame 26 to the CAN bus 26 at regular intervals T1 (12 ms), and all the data is returned from the sensors 18-24. If so, VSC control can be executed based on those data.

Since the turning behavior ECU 10 is the node having the highest priority of data transmission on the CAN bus 26 among all the nodes as described above, the turning behavior ECU 10 is
When the transmission to the CAN bus 26 is performed, the trigger frame to be transmitted is transmitted in a relatively short time, specifically, at the longest transmission time, immediately after the transmission of the data flowing through the CAN bus 26 is completed. Start flowing on the bus 26. That is, the trigger frame by the turning behavior ECU 10 is C
The data is the data that is most likely to flow through the AN bus 26. Therefore, the trigger frame by the turning behavior ECU 10 is C
After the transmission to the AN bus 26 is started, it is received by the sensors 18 to 24 in a relatively short time.

FIG. 6 shows a flow chart of a control routine executed in each of the sensors 18 to 24 of this embodiment. The routine shown in FIG. 6 is a routine that is started each time the processing is completed. When the routine shown in FIG. 6 is started, the process of step 120 is first executed.

In step 120, the turning behavior ECU 10
It is determined whether or not the transmitted trigger frame has been received. As a result, when it is determined that the trigger frame has not been received, the process of step 122 is executed next.

In step 122, whether or not the time (T1 + α) obtained by adding the predetermined time α to the above-mentioned constant period T1 has elapsed since the last trigger frame was received, or
After A / D conversion of the physical quantity such as acceleration is performed, it is determined whether or not a predetermined time T3 has elapsed. The predetermined time α
Indicates that the turning behavior ECU 10 has a transmission abnormality, a reception abnormality of the sensor, or the like.
Is the minimum time during which a trigger frame transmitted at a constant period T1 should be received but should not be received, and is set to, for example, 8 ms. Further, the predetermined time T3 is a transmission time interval of data to be transmitted by the sensor even if a transmission abnormality of the turning behavior ECU 10 or a reception abnormality of the sensor occurs, and is, for example, 2
It is set to 0 ms. As a result, if a negative determination is made, the process of step 120 is repeated.

If it is determined in step 120 that the trigger frame has been received, and if an affirmative determination is made in step 122, then the process of step 124 is executed.

At step 124, A / D conversion processing for converting analog data such as acceleration, steering angle, yaw rate, and wheel speed into digital data is executed. Then, in step 126, the data including the digital data obtained as a result of the A / D conversion processing in step 124 is converted into C
The process of transmitting to the AN bus 26 is executed. When the processing of this step 126 is executed, the sensor 18
The data from 24 to 24 flow through the CAN bus 26 and are received by the turning behavior ECU 10. When the processing of step 126 is completed, the routine of this time is ended.

According to the routine shown in FIG. 6, each time the sensors 18 to 24 receive the trigger frame from the turning behavior ECU 10, the physical quantity is A / D converted and the result is stored in the CAN bus 26 as digital data. Can be sent out. In such a configuration, each sensor 18-2
4 sends data to the CAN bus 26 for turning behavior EC
This is the data that is generated in the vehicle after the data transmission is requested by U10 and is relatively latest.

As described above, since the sensors 18 to 24 are the nodes having the second highest priority of data communication on the CAN bus 26 among all the nodes as described above, the data transmitted by the sensors 18 to 24. When transmission to the CAN bus 26 is performed, unless the turning behavior ECU 10 has to transmit data, immediately after the transmission of the data flowing through the CAN bus 26 is completed, the CAN bus 26 is transmitted at the longest transmission time. Start flowing. That is, each data from the sensors 18 to 24 is data that easily flows through the CAN bus 26. Therefore, each sensor 18-2
The data of 4 is received by the turning behavior ECU 10 in a relatively short time after the transmission to the CAN bus 26 is started.

Therefore, according to the present embodiment, the turning behavior ECU 10 and the sensors 18 to 2 for performing the VSC control.
Even if each node of No. 4 is connected to each other via the CAN bus 26, the turning behavior ECU 10 uses the sensors 18 to
For each of the 24 output signals, the latest one can be received at a predetermined timing. Therefore, according to the system of the present embodiment, the turning behavior ECU 10 and the sensors 18 can be used even when various in-vehicle systems are configured by CAN communication.
To 24, it is possible to synchronize the data communication with each other, thereby reliably avoiding deterioration of the responsiveness of VSC control, and appropriately controlling the turning behavior of the vehicle. Has become.

Further, since only the data from one node flows to the CAN bus 26, the turning behavior ECU 10
Receives each data from the sensors 18 to 24 with a time difference. However, since the trigger frame transmitted by the turning behavior ECU 10 is supplied to the respective sensors 18 to 24 via the CAN bus 26 at substantially the same time,
The data subjected to A / D conversion processing by ˜24 becomes the physical quantity that has occurred in the vehicle at substantially the same time. Therefore, the turning behavior E
Even if the CU 10 receives each data from the sensors 18 to 24 with a time difference, it can detect each vehicle data at substantially the same time based on the data. Therefore, according to the present embodiment, the vehicle state necessary for executing the VSC control can be accurately grasped, and the VSC control can be accurately performed.

Further, in the routine shown in FIG. 6, even if the sensors 18 to 24 do not receive the trigger frame from the turning behavior ECU 10, the predetermined time (T1 + α) is reached.
When a predetermined time T3 has elapsed or when a predetermined time T3 has elapsed, the physical quantity can be A / D converted, and the result can be sent to the CAN bus 26. That is, each sensor 18-24
Can voluntarily send data to the CAN bus 26 without receiving a trigger frame. Therefore, according to the system of the present embodiment, the turning behavior ECU 10 has a failure that the trigger frame cannot be received, or the sensor 18-
The turning behavior EC that requires the data from the sensors 18 to 24 even when the reception abnormality of 24 is occurring.
It is possible to avoid a situation in which the node such as the U10, the traction ECU 12, the lock ECU 14 and the like cannot receive the data, and it is possible to reliably perform control based on the data. Therefore, according to this embodiment, each sensor 18-2
It is possible to prevent the system from being adversely affected by the fact that 4 does not receive the trigger frame by the turning behavior ECU 10.

Since each of the sensors 18 to 24 can transmit data at a constant time T3, unlike the system of this embodiment, even a system that does not perform highly urgent control such as VSC control. The sensors 18 to 24 can be used. That is, such sensors 18-2
According to the configuration of 4, the CAN communication system can be adapted to both the system with urgency and the system without urgency, and the number of sensor types can be reduced.

In this embodiment, the turning behavior EC
When U10 does not receive the return of data from all the sensors 18 to 24 even after the lapse of the predetermined time T2 after transmitting the trigger frame, the sensors 18 to 24 have a failure or each of the sensors 18 to 24. And turning behavior ECU 10
It is determined that a failure has occurred in the communication system between and and data abnormality has occurred. Therefore, according to the present embodiment, it is possible to execute VSC control corresponding to such a failure,
It is possible to take appropriate measures.

In the above embodiment, the CAN controller 30 is included in the “CAN controller unit” described in the claims, and the turning behavior ECU 10 is included in the “first node” described in the claims. Sensor 18,
The steering angle sensor 20, the yaw rate sensor 22, and the wheel speed sensor 24 are the "second node" described in the claims.
, Respectively.

Further, in the above-described embodiment, the turning behavior ECU 10 executes the routine shown in FIG. 5 so that the "first step" described in the scope of claims is shown in FIG. By executing the routine shown, the "second step" described in the claims is
Each has been realized.

By the way, in the above embodiment, it is necessary to distinguish between the case where data is transmitted to each of the sensors 18 to 24 in response to the trigger frame from the turning behavior ECU 10 and the case where data is transmitted spontaneously. Instead of transmitting the same data, it is also possible to transmit data to which a trigger for distinguishing the two is added. In such a configuration, it becomes possible to cause the turning behavior ECU 10, the traction ECU 12, and the like to execute fine control according to the reception state of the sensors 18 to 24.

In the above embodiment, the turning behavior ECU 10 transmits the trigger frame when the turning behavior ECU 10 requests the data transmission by the sensors 18 to 24, but the vehicle speed information and the vehicle state information are added to the trigger frame. It may be added. In such a configuration, the sensors 18 to 24 can perform signal processing by using such information, so that the self-diagnosis function of the sensors 18 to 24 is improved.

Further, in the above embodiment, in order to properly perform the VSC control in the CAN communication system, the data between the turning behavior ECU 10 and the G sensor 18, the steering angle sensor 20, the yaw rate sensor 22 and the wheel speed sensor 24 are used. Although the communication is supposed to be synchronized, the data communication between the control unit and the sensor may be synchronized in order to appropriately perform other controls (for example, traction control, ABS control, etc.).

[0061]

As described above, according to the first to fifth aspects of the present invention, it is possible to synchronize data communication between specific nodes among a plurality of nodes connected to each other via the CAN bus.

According to the invention described in claim 6, since the data is transmitted from the second node even if the trigger frame by the first node is not received by the second node, the node requiring the data is transmitted. There is no case where the data is not received by the second node, and the control based on the data can be surely executed.

According to the seventh aspect of the present invention, it is possible to cause a node that requires data from the second node to perform fine control according to the reception state of the second node.

According to the invention described in claim 8, it is possible to determine whether or not there is a failure in the second node or the communication system in the first node.

According to the invention of claim 9, since the data communication between the control unit of the turning behavior and the sensor is synchronized, the response of the turning behavior control is deteriorated even by the CAN communication. Can be reliably prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a CAN communication system that is an embodiment of the present invention.

FIG. 2 is a diagram showing the data content of one frame transmitted by each node that constitutes the CAN communication system of the present embodiment.

FIG. 3 is a diagram showing a transmission principle of a CAN communication system.

FIG. 4 is a diagram schematically showing exchange of data communication between a turning behavior ECU and each sensor in the CAN communication system of the present embodiment.

FIG. 5 is a flowchart of a control routine executed in the turning behavior ECU of the present embodiment.

FIG. 6 is a flowchart of a control routine executed in each sensor of this embodiment.

[Explanation of symbols]

10 Turning behavior ECU 18 G sensor 20 Rudder angle sensor 22 Yaw rate sensor 24 wheel speed sensor 26 Communication Bus (CAN Bus) 30 CAN controller

Claims (9)

[Claims] 1. A CAN communication method for performing communication between a plurality of nodes, each having a CAN controller unit, connected to each other via a CAN bus, wherein the first node is at least one second node. A first step of transmitting a trigger frame for transmitting data to the CAN bus when data is required, the second node receiving the trigger frame from the first node And a second step of transmitting data to be transmitted to the CAN bus in the case of performing the CAN communication method. 2. The CAN communication method according to claim 1, wherein each of the first node and the second node is a node having a relatively high priority on the CAN bus among all the nodes. . 3. A CAN communication system comprising a plurality of nodes, each having a CAN controller, connected to each other via a CAN bus, the first node requiring data by at least one second node. In this case, the trigger frame for transmitting the data is transmitted toward the CAN bus, and the second node is the data to be transmitted when the trigger frame is received from the first node. Is transmitted to the CAN bus. 4. The CAN communication system according to claim 3, wherein each of the first node and the second node is a node having a relatively high priority on the CAN bus among all the nodes. . 5. The second node samples data when it receives the trigger frame from the first node, and outputs the resulting data to the CAN bus as data to be transmitted. The CAN communication system according to claim 3, wherein the CAN communication system transmits. 6. The first node transmits the trigger frame at a predetermined cycle, and the second node also when the state in which the trigger frame is not received continues beyond the predetermined cycle. 6. The CAN communication system according to claim 3, wherein data to be transmitted is transmitted toward the CAN bus. 7. The second node transmits, to the CAN bus, data to which a trigger for discriminating the trigger frame is added depending on whether the trigger frame is received or not. The CAN communication system according to claim 6. 8. The first node transmits the trigger frame to the CAN bus, and when the state in which data from the second node is not received continues for a predetermined time, the second node transmits the second frame. 8. The CAN communication system according to claim 3, wherein it is determined that a node or a communication system has a failure. 9. The first node is a control unit for controlling a turning behavior of a vehicle, and the second node is a sensor for outputting a parameter necessary for controlling a turning behavior of a vehicle. The CAN communication system according to claim 3, wherein the CAN communication system is provided.