JP4032779B2 - CAN communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a CAN communication method and system for performing communication between a plurality of nodes connected to each other via a CAN bus, and more particularly to a CAN communication method suitable for synchronizing data communication between specific nodes. And about the system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-142794, a CAN communication system is known that performs data communication between a plurality of nodes that are connected to each other via a CAN bus and each have a CAN controller unit. CAN communication is a protocol for performing bidirectional serial communication via a differential serial bus.
[0003]
In such a CAN communication system, each node sends out data with an identification ID code of its own node toward the CAN bus. If the CAN bus is not dedicated to data from other nodes when data is transmitted, the data sent from the node flows through the CAN bus and is received by the other nodes. On the other hand, when the CAN bus is exclusively used for data by other nodes, data to be sent from the nodes is waited for in the CAN controller unit. If there is only one node waiting for data, the data flows through the CAN bus when the CAN bus is free. On the other hand, when there are a plurality of nodes waiting for data, the data of the node having the highest priority based on the ID code among these nodes flows through the CAN bus before other standby data.
[0004]
[Problems to be solved by the invention]
By the way, among a plurality of nodes connected to each other via the CAN bus, there is a node that wants to receive data from other nodes at a desired timing. For example, in order to properly control the turning behavior of a vehicle, it is necessary to detect the yaw rate, acceleration, and vehicle steering angle that are actually generated in the vehicle at each point in a short cycle. In a vehicle in which various control units for controlling wheel locks and various sensors such as yaw rate, acceleration, and steering angle are configured by a CAN communication system, the control unit for controlling turning behavior controls the yaw rate of the vehicle at a desired timing. The node that you want to receive.
[0005]
However, in CAN communication, data of nodes with high priority based on the ID code among nodes connected to the CAN bus easily flows through the CAN bus, and data of nodes with low priority does not easily flow through the CAN bus. Even if data by another node is received by the node, the received data may not be the latest. In this regard, data communication between nodes in CAN communication is asynchronous. Therefore, even if one node wants to receive the latest data from another node at a desired timing, such data may not be received. For this reason, the control responsiveness in the one node may be deteriorated.
[0006]
The present invention has been made in view of the above points, and an object of the present invention is to provide a CAN communication method and system capable of synchronizing data communication between specific nodes among a plurality of nodes.
[0007]
[Means for Solving the Problems]
[0008]
  UpThe purpose of1A CAN communication system comprising a plurality of nodes connected to each other via a CAN bus, each having a CAN controller,
  If the first node needs data from at least one second node, it sends a trigger frame to which data should be sent towards the CAN bus; and
  When the second node receives the trigger frame from the first node,Data sampling is performed at the time of receiving the trigger frame, and the resulting data is transmitted as data to be transmitted.This is accomplished by a CAN communication system that transmits towards the CAN bus.
[0009]
  BookIn the invention, 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 When a trigger frame is received, Sample the data when the trigger frame is received, and send the data obtained as a result to be transmittedSend to the CAN bus. According to such a configuration, since the second node transmits data triggered by frame transmission by the first node, data communication between those specific nodes can be synchronized.
[0012]
By the way, if the second node transmits data only when a trigger frame is received by the first node, if the trigger frame is not received, the second node does not transmit data. Therefore, there occurs a situation in which a node including the first node that needs the data cannot receive the data from the second node, which adversely affects the system.
[0013]
  Therefore, the claims2As claimed in1In the described CAN communication system, the first node transmits the trigger frame at a predetermined period, and the second node does not receive the trigger frame for more than the predetermined period. In addition, if the data to be transmitted is transmitted to the CAN bus, the second node transmits the data reliably without receiving the trigger frame by the first node. A situation in which a node that requires data by the node cannot receive such data does not occur, and control based on the data can be reliably executed.
[0014]
  In this case, the claim3As claimed in2In the described CAN communication system, the second node transmits data to the CAN bus with a trigger added to distinguish between the case where the trigger frame is received and the case where the trigger frame is not received. For example, it is possible to cause a node that needs data from the second node to execute fine control according to the reception state of the second node.
[0015]
In addition, although the data communication is synchronized between the first node and the second node as described above, the transmission of the trigger frame at the first node is performed by the second node. If the state in which no data is received continues for a long period of time, it can be determined that a failure has occurred in the second node or the communication system between them.
[0016]
  Therefore, the claims4As claimed in1Thru35. The CAN communication system according to claim 1, wherein after the first node transmits the trigger frame to the CAN bus, a state in which data from the second node is not received continues for a predetermined time. In this case, it may be determined that a failure has occurred in the second node or communication system.
[0017]
  still,The CAN communication system according to any one of claims 1 to 4, wherein each of the first node and the second node is a priority order on the CAN bus among all nodes. If the nodes are relatively high, data from those nodes can easily flow through the CAN bus, so that synchronization of data communication between the first node and the second node can be reliably ensured. it can.
Also,Claim6As claimed in1Thru55. The CAN communication system according to claim 1, wherein the first node is a control unit that controls the turning behavior of the vehicle, and the second node is necessary for controlling the turning behavior of the vehicle. If it is a sensor that outputs various parameters, the data communication between the control unit of the turning behavior and the sensor is synchronized, so it is ensured that the response of the turning behavior control deteriorates even in CAN communication. Can be prevented.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a configuration diagram of a CAN communication system according to an embodiment of the present invention. The CAN communication system of a present Example is a system mounted in the vehicle. In the vehicle, various vehicle controls are performed. Specifically, control for stabilizing the turning behavior of the vehicle (hereinafter referred to as VSC (Vehicle Stability Control) control (turning behavior control)), ensuring acceleration, straightness, and turning stability of the vehicle. Control (hereinafter referred to as TRC (Traction Control) control), control for preventing wheel locking (hereinafter referred to as ABS (Antilock Brake System) control), and the like are performed.
[0019]
As shown in FIG. 1, the vehicle includes a VSC electronic control unit (hereinafter referred to as a turning behavior ECU) 10 that executes VSC control, a TRC electronic control unit (hereinafter referred to as traction ECU) 12 that performs TRC control, And, it has an ABS electronic control unit (hereinafter referred to as a lock ECU) 14 for executing ABS control. In addition, the vehicle has sensors for realizing various vehicle controls, specifically, a G sensor 18 that outputs a signal corresponding to the acceleration generated in the longitudinal direction and the vehicle width direction of the vehicle, and a signal corresponding to the wheel steering angle. A steering angle sensor 20 for output, a yaw rate sensor 22 for outputting a signal corresponding to the yaw rate generated around the vertical axis of the center of gravity of the vehicle, a wheel speed sensor 24 provided for each wheel and outputting a signal corresponding to the wheel speed, etc. Have.
[0020]
The turning behavior ECU 10 detects the running state of the vehicle based on the output signals of various sensors such as the G sensor 18, the steering angle sensor 20, the yaw rate sensor 22, and the wheel speed sensor 24. As a result, the vehicle tends to skid. When the vehicle is on, the braking force is applied to the front wheels or the rear wheels so that the tendency is alleviated, and the yawing of the vehicle is controlled. According to the VSC control, the turning behavior of the vehicle can be stabilized. The traction ECU 12 detects the throttle opening and the like, and as a result, when there is a possibility that an excessive torque may be generated at the time of start or acceleration, the traction ECU 12 applies a braking force to the drive wheels so that the torque is not generated or outputs the engine. Or suppress the generator output. According to such TRC control, a driving force corresponding to the road surface condition is ensured 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, controls the braking force that can be generated on each wheel so that the wheel does not lock when the wheel tends to lock during braking. . According to such ABS control, the lock of the wheel is prevented and the brake performance is sufficiently ensured, so that the steering wheel operability and the vehicle stability are reliably maintained.
[0021]
Control units such as a turning behavior ECU 10, a traction ECU 12, and a lock ECU 14 that the vehicle has, a G sensor 18, a steering angle sensor 20, a yaw rate sensor 22, and a wheel speed sensor 24 are connected to each other via a communication bus 26. Yes. The communication bus 26 has two communication lines and is a bus for performing differential serial communication. Various control units incorporate a controller area network (hereinafter referred to as CAN) controller 30 together with a controller, RAM, and ROM for executing corresponding vehicle control. Each sensor also includes a CAN controller 30 together with a detection unit that outputs analog data corresponding to a corresponding physical quantity and a circuit for converting a signal from the detection unit into digital data.
[0022]
Hereinafter, the communication bus 26 is referred to as a CAN bus 26, and various control units and various sensors connected to each other via the CAN bus 26 are collectively referred to as nodes. Each node transmits transmission data via a driver included in the CAN controller 30 when communicating with another node. That is, in such a configuration, the node exchanges data with other nodes via the CAN controller 30 and the CAN bus 26 in both directions.
[0023]
FIG. 2 is a diagram showing the data contents of one frame transmitted by each node constituting the CAN communication system of the present embodiment. For example, as shown in FIG. 2, one frame transmitted as data by each node varies in an ID field for storing the identification number of the node, a control field for storing the data length of the data field, and 0 to 8 bytes. A data field for storing data to be transmitted and a CRC field for storing data for performing cyclic code redundancy check. Each node has a transmission rate of, for example, 500 kbps. When the data length of the data field is 8 bytes, one frame data of about 120 bits can be transmitted and received in about 250 μs.
[0024]
The ID field of one frame data is provided in the upper part of the data to be transmitted, and the upper bit (for example, 11 bits) is the identification number of the own node (for example, a 3-digit hexadecimal number) 2 Converted to hexadecimal data. Note that the identification number in the ID field of each node is different from the identification numbers of the other nodes.
[0025]
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, data that can flow through the CAN bus 26 at a time is the data of only one node among the plurality of nodes. Become. Therefore, in the CAN communication, when a plurality of nodes should transmit data, the data sent from each node to the CAN bus 26 at random is not superimposed on the CAN bus 26, that is, It is necessary to arbitrate the data flowing through the CAN bus 26 so that the data of only one node flows through the CAN bus 26.
[0026]
As described above, the self-identification number is attached to the data transmitted by each node. Therefore, in CAN communication, data flowing through the CAN bus 26 is determined based on an identification number assigned to the higher rank of data transmitted by each node. That is, as the identification number is smaller, the number of low levels “0” appearing from the upper bits of the ID field increases. On the other hand, as the identification number is larger, high levels “1” are more likely to appear in the upper bits. The data from the smaller node has a low level “0” on the upper side. Each of the CAN controllers 30 of each node determines whether or not a low level “0” has been supplied via the CAN bus 26 and, in a situation where its own data is to be transmitted, Compare with identification numbers from other nodes. Then, when the identification number of another node related to reception is larger than its own, the data transmission is continued, while when it is smaller, the data transmission is suspended and waited.
[0027]
For example, as shown in FIG. 3, data A transmitted from a certain node starts to flow through the CAN bus 26 at time t1, and before the transmission of the data A is completed, another node transmits data B toward the CAN bus 26. Is at the timing to send out (time t2), the data B is waited in the CAN controller 30 of its own node. When transmission of data A is completed at time t3, data B that has been waiting for transmission from the other node starts to flow through the CAN bus 26.
[0028]
Under such circumstances, when the data C and the data D are to be transmitted toward the CAN bus 26 before the transmission of the data B is completed (time t4 and t5), the data C and D are stored in the respective nodes. In the CAN controller 30 of the system. When transmission of data B is completed at time t6, data C and data D begin to flow through CAN bus 26. Among nodes transmitting data C and D, a node with a large identification number is due to a node with a small identification number. When the data D or C is received, the transmission of the data C or D is interrupted and waited. For this reason, when the identification number of the node that transmits data D is smaller than that of the node that transmits data C, after the transmission of data B is completed, the identification number of both data C and D is smaller. The data D by the node starts to flow through the CAN bus 26 before the data C and is received by each node. When the transmission of the data D is completed at time t7, the standby data C starts flowing through the CAN bus 26.
[0029]
As described above, according to the arbitration function of the CAN controller 30 included in each node, data flowing through the CAN bus 26 is determined based on the identification number of the node attached to the data transmitted by each node. Specifically, when a plurality of data is to be transmitted through the CAN bus 26 almost simultaneously, the data of the node having the smallest identification number flows through the CAN bus 26. Therefore, according to the CAN communication system, even in a situation where a plurality of data is to be transmitted through the CAN bus 26 almost simultaneously, it is possible to reliably send out only one data to the CAN bus 26 and allow a plurality of nodes to receive it simultaneously. It becomes possible. Thereby, the communication load can be reduced and the communication efficiency can be improved.
[0030]
By the way, in order to reliably stabilize the turning behavior of the vehicle and perform VSC control appropriately, each parameter such as acceleration and yaw rate generated in the vehicle at each time point is detected in a short period (for example, 12 ms), It is necessary to apply an appropriate braking force to the vehicle. That is, the turning behavior ECU 10 needs to receive output signals from the G sensor 18 and the yaw rate sensor 22 at a desired timing.
[0031]
However, in the above-described CAN communication, data from a node having a smaller identification number flows through the CAN bus 26 more easily. That is, the priority of data flowing through the CAN bus 26 is higher in the data by the node having the smaller identification number than the data by the node having the larger identification number. For this reason, 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 output signals of these sensors are received by the turning behavior ECU 10, the received data is May not be up to date. Therefore, in the CAN communication system according to the present embodiment, in a configuration in which each sensor transmits an output at random, there may be a problem that appropriate VSC control cannot be performed.
[0032]
FIG. 4 is a diagram schematically showing exchange of data communication between the turning behavior ECU 10 and the sensors 18 to 24 in the CAN communication system of the present embodiment. In order to avoid the above-described inconveniences, the system according to the present embodiment includes nodes (specifically, turning behavior ECU 10, G sensor 18, rudder angle sensor 20, yaw rate sensor 22, and wheel speed sensor required for VSC control of the vehicle. The identification number of 24) is made smaller than those of other nodes, and the priority on the CAN bus 26 is made relatively high. For example, among all nodes connected to each other via the CAN bus 26, the turning behavior ECU 10 is a node having the highest priority, and the sensors 18 to 24 are nodes having the second priority to the fifth priority. Set.
[0033]
Then, as shown in FIG. 4, the turning behavior ECU 10 uses a CAN bus every predetermined cycle T1 (for example, 12 ms) using a command requesting transmission of acceleration, yaw rate, steering angle, and wheel speed as control parameters for VSC control as a trigger frame. 26. Further, when each of the sensors 18 to 24 receives a trigger frame from the turning behavior ECU 10, it starts and executes A / D conversion processing for its own physical quantity, and sends the resulting digital data to the CAN bus 26. .
[0034]
In such a system, since the priority order of the turning behavior ECU 10 on the CAN bus 26 is the highest, the trigger frame transmitted by the turning behavior ECU 10 is received by each of the sensors 18 to 24 in a short time after the transmission. be able to. Further, each of the sensors 18 to 24 does not perform A / D conversion on the physical quantity at random, but performs A / D conversion processing according to the trigger frame of the turning behavior ECU 10. Furthermore, since the priority order of the sensors 18 to 24 on the CAN bus 26 is the next highest after the turning behavior ECU 10, the data transmitted by the sensors 18 to 24 is transmitted in a short time after the transmission is performed. It can be received by the turning behavior ECU 10.
[0035]
For this reason, 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 includes the G sensor 18, the steering angle sensor 20, the yaw rate sensor 22, In addition, it is possible to receive the latest output signals of the wheel speed sensor 24 at a desired timing. Therefore, according to the system of the present embodiment, data communication between the turning behavior ECU 10 and each of the sensors 18 to 24 can be synchronized, so that it is reliably avoided that the responsiveness of VSC control deteriorates. Thus, it is possible to appropriately perform the turning behavior.
[0036]
FIG. 5 shows a flowchart of a control routine executed in the turning behavior ECU 10 of this embodiment in order to realize the above function. The routine shown in FIG. 5 is started every time the process is completed. When the routine shown in FIG. 5 is started, first, the process of step 100 is executed.
[0037]
In step 100, a trigger frame requesting transmission of acceleration, rudder angle, yaw rate, and wheel speed to the G sensor 18, rudder angle sensor 20, yaw rate sensor 22, and wheel speed sensor 24 is transmitted to the CAN bus 26. Is executed. As described above, since the priority order of the turning behavior ECU 10 on the CAN bus 26 is the highest, when the processing of this step 100 is executed, the data flowing through the CAN bus 26 at most 250 μs later, that is, at the present time. Immediately after the transmission of is completed, a trigger frame by the turning behavior ECU 10 starts to flow through the CAN bus 26 and is received by each node.
[0038]
In step 102, it is determined whether each data has been returned from all of the sensors 18-24. Since the CAN bus 26 is a serial bus and only data from only one node flows at a time, the turning behavior ECU 10 transmits a trigger frame and then receives all the data of the sensors 18 to 24. Takes about several ms. As a result, when it is determined that all the data of the sensors 18 to 24 are not returned, the process of step 104 is executed next.
[0039]
In step 104, it is determined whether or not a predetermined time T2 (<T1) has elapsed after the trigger frame transmission is started in step 100. The fixed time T2 is set to, for example, 2 ms, which is longer than the time when all the data of the sensors 18 to 24 should be received and shorter than the trigger frame period T1, after the transmission of the trigger frame is started. ing. As a result, if it is determined that the predetermined time T2 has not elapsed, the process of step 102 is executed next. On the other hand, if it is determined that the predetermined time T2 has elapsed, a failure has occurred in which data cannot be transmitted to the sensors 18 to 24 even though the trigger frame has been transmitted. Even though the sensors 18 to 24 are transmitting data, it can be determined that the communication system has failed, or that the trigger frame by the turning behavior ECU 10 or the data by the sensors 18 to 24 is abnormal. Therefore, if such a determination is made, the process of step 106 is executed next. In step 106, it is determined that a failure has occurred in the communication system or the like that connects the sensors 18 to 24 or the turning behavior ECU 10 and the sensors 18 to 24. In this case, a warning lamp may be turned on and a warning may be given to alert the vehicle driver to that effect.
[0040]
On the other hand, when it is determined in step 102 that all the data of the sensors 18 to 24 have been returned, and when the process of step 106 is completed, the process of step 108 is executed next. In step 108, based on the acceleration by the G sensor 18, the wheel steering angle by the steering angle sensor 20, the yaw rate by the yaw rate sensor 22, and the wheel speed by the wheel speed sensor 24, VSC control for stabilizing the turning behavior of the vehicle is executed. Processing is executed. When the process of this step 108 is executed, if a skid tendency is generated in the vehicle thereafter, a braking force is applied to the front wheels or the rear wheels of the vehicle so that yawing that reduces the tendency occurs.
[0041]
In step 110, it is determined whether or not the predetermined period T1 has elapsed after transmission of the trigger frame is started in step 100. The processing of this step 110 is repeatedly executed until a certain period T1 has elapsed. As a result, if it is determined that the fixed period T1 has elapsed, the current routine is terminated, and the trigger frame is transmitted again in step 100.
[0042]
According to the routine shown in FIG. 5 above, the turning behavior ECU 10 can send the trigger frame 26 to the CAN bus 26 at a constant period T1 (12 ms), and when all data are returned from the sensors 18-24. VSC control can be executed based on these data.
[0043]
As described above, the turning behavior ECU 10 is the node having the highest priority for data transmission on the CAN bus 26 among all the nodes. Therefore, the trigger frame transmitted by the turning behavior ECU 10 is transmitted to the CAN bus 26. In a relatively short time, specifically, at the longest transmission time, immediately after the transmission of data flowing through the CAN bus 26 is completed, the CAN bus 26 starts flowing. That is, the trigger frame by the turning behavior ECU 10 is data that is most likely to flow through the CAN bus 26. For this reason, the trigger frame by the turning behavior ECU 10 is received by the sensors 18 to 24 quickly in a relatively short time after the transmission to the CAN bus 26 is started.
[0044]
FIG. 6 shows a flowchart of a control routine executed in each of the sensors 18 to 24 of the present embodiment. The routine shown in FIG. 6 is started every time the process is completed. When the routine shown in FIG. 6 is started, the process of step 120 is first executed.
[0045]
In step 120, it is determined whether or not the trigger frame transmitted from the turning behavior ECU 10 has been received. As a result, if it is determined that the trigger frame has not been received, the process of step 122 is executed next.
[0046]
In step 122, it is determined whether or not a time (T1 + α) obtained by adding the predetermined time α to the fixed period T1 has elapsed since the previous trigger frame was received, or A / D conversion of physical quantities such as acceleration is performed. After that, it is determined whether or not a predetermined time T3 has elapsed. It should be noted that a trigger frame transmitted by the turning behavior ECU 10 at a constant period T1 should be received during the predetermined time α, which can be determined that a transmission abnormality of the turning behavior ECU 10 or a reception abnormality of the sensor has occurred. Regardless, it is the minimum time for which a state in which no signal is received continues, and is set to 8 ms, for example. 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 set to 20 ms, for example. As a result, when a negative determination is made, the process of step 120 is repeated.
[0047]
If it is determined in step 120 that a trigger frame has been received, and if an affirmative determination is made in step 122, then the process of step 124 is executed.
[0048]
In step 124, A / D conversion processing for converting analog data such as acceleration, steering angle, yaw rate, wheel speed, etc. into digital data is executed. In step 126, a process of transmitting data including the digital data obtained as a result of the A / D conversion process in step 124 to the CAN bus 26 is executed. When the processing of this step 126 is executed, data from the sensors 18 to 24 thereafter flows through the CAN bus 26 and is received by the turning behavior ECU 10. When the process of step 126 is completed, the current routine is terminated.
[0049]
According to the routine shown in FIG. 6, each time the sensors 18 to 24 receive a trigger frame from the turning behavior ECU 10, the physical quantity is A / D converted, and the result is sent as digital data to the CAN bus 26. it can. In such a configuration, the data sent from the sensors 18 to 24 to the CAN bus 26 is data generated in the vehicle after the turning behavior ECU 10 requests data transmission, and is relatively up-to-date.
[0050]
As described above, each of the sensors 18 to 24 has the next highest priority for data communication on the CAN bus 26 among the nodes, as described above. Therefore, the data transmitted from the sensors 18 to 24 is CAN. When transmission to the bus 26 is performed, if the turning behavior ECU 10 is not in a state where data should be transmitted, it starts flowing through the CAN bus 26 immediately after transmission of data flowing through the CAN bus 26 is completed at the time of transmission at the longest. . That is, each data by the sensors 18 to 24 is easy to flow through the CAN bus 26. For this reason, after the transmission to the CAN bus 26 is started, the data from the sensors 18 to 24 is received by the turning behavior ECU 10 in a relatively short time.
[0051]
For this reason, according to the present embodiment, even if the nodes of the turning behavior ECU 10 and the sensors 18 to 24 for performing the VSC control are connected to each other via the CAN bus 26, the turning behavior ECU 10 is connected to the sensor 18. The latest output signals can be received at a predetermined timing for each of the output signals of ˜24. Therefore, according to the system of the present embodiment, even when various in-vehicle systems are configured by CAN communication, data communication between the turning behavior ECU 10 and the sensors 18 to 24 can be synchronized. As a result, it is possible to reliably avoid the deterioration of the responsiveness of the VSC control, and to appropriately control the turning behavior of the vehicle.
[0052]
Further, since only data from one node flows through the CAN bus 26, the turning behavior ECU 10 receives the 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 sensors 18 to 24 almost simultaneously via the CAN bus 26, the data subjected to A / D conversion processing by the sensors 18 to 24 is almost the same time. This is the physical quantity generated in the vehicle. Therefore, even if the turning behavior ECU 10 receives the data from the sensors 18 to 24 with a time difference, the turning behavior ECU 10 can detect the vehicle data at substantially the same time based on the data. For this reason, according to the present embodiment, the vehicle state necessary for executing the VSC control can be accurately grasped, and the VSC control can be performed accurately.
[0053]
In the routine shown in FIG. 6, each sensor 18 to 24 does not receive a trigger frame from the turning behavior ECU 10, but when the predetermined time (T1 + α) elapses or every time the predetermined time T3 elapses. The physical quantity can be A / D converted, and the result can be sent to the CAN bus 26. That is, each of the sensors 18 to 24 can spontaneously send data to the CAN bus 26 without receiving a trigger frame. For this reason, according to the system of the present embodiment, even when a failure in which the turning behavior ECU 10 cannot receive the trigger frame or a reception abnormality of the sensors 18 to 24 occurs, data from the sensors 18 to 24 is required. A situation in which nodes such as the turning behavior ECU 10, the traction ECU 12, and the lock ECU 14 cannot receive the data can be avoided, and the control based on the data can be reliably performed. Therefore, according to the present embodiment, it is possible to prevent the system from being adversely affected by the sensors 18 to 24 not receiving the trigger frame from the turning behavior ECU 10.
[0054]
In addition, since each sensor 18-24 can transmit data for every fixed time T3, unlike the system of a present Example, even if it is a system which does not perform highly urgent control, such as VSC control, this sensor 18-24 can be used. That is, according to the configuration of the sensors 18 to 24, in the CAN communication system, it is possible to cope with both a system with urgency and a system without urgency, and the number of sensor types can be reduced. .
[0055]
Further, in this embodiment, after the turning behavior ECU 10 transmits the trigger frame, if the return of data is not received from all the sensors 18 to 24 even after the predetermined time T2 has elapsed, the sensors 18 to 24 are broken. Or the communication system between each of the sensors 18 to 24 and the turning behavior ECU 10 is determined to have failed or data abnormality has occurred. For this reason, according to the present embodiment, VSC control corresponding to such a failure can be executed, and appropriate measures can be taken.
[0056]
In the above embodiment, the CAN controller 30 is connected to the “CAN controller unit” described in the claims, the turning behavior ECU 10 is connected to the “first node” described in the claims, the G sensor 18, The steering angle sensor 20, the yaw rate sensor 22, and the wheel speed sensor 24 correspond to the “second node” recited in the claims.
[0057]
Moreover, in said Example, turning behavior ECU10 performs the routine shown in FIG. 5, and the "1st step" described in the claim performs the routine which each sensor 18-24 shows in FIG. By executing, the “second step” described in the claims is realized.
[0058]
By the way, in said Example, it is the same, without distinguishing the case where data is transmitted to each sensor 18-24 in response to the trigger frame from turning behavior ECU10, and the case where data are transmitted spontaneously. Although data is transmitted, it is also possible to transmit data to which a trigger for distinguishing both is added. In such a configuration, it is possible to cause the turning behavior ECU 10 and the traction ECU 12 to execute fine control according to the reception state of the sensors 18 to 24.
[0059]
In the above embodiment, the turning behavior ECU 10 transmits a trigger frame when requesting transmission of data by the sensors 18 to 24. However, vehicle speed information and vehicle state information are added to the trigger frame. It is good. In such a configuration, since the sensors 18 to 24 can perform signal processing using such information, the self-diagnosis function of the sensors 18 to 24 is improved.
[0060]
Further, in the above embodiment, data communication 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 is synchronized in order to appropriately perform VSC control in the CAN communication system. However, in order to appropriately perform other control (for example, traction control, ABS control, etc.), data communication between the control unit and the sensor may be synchronized.
[0061]
【The invention's effect】
  As described above, claims 1 to6According to the described invention, data communication between specific nodes among a plurality of nodes connected to each other via a CAN bus can be synchronized.
[0062]
  Claim2According to the described invention, the data is transmitted from the second node even if the trigger frame by the first node is not received by the second node. A situation in which no data is received does not occur, and control based on the data can be surely executed.
[0063]
  Claim3According to the described invention, it is possible to cause a node that requires data from the second node to execute fine control according to the reception state of the second node.
[0064]
  Claim4According to the described invention, it is possible to determine whether or not there is a failure in the second node or the communication system in the first node.
[0065]
  Claims6According to the described invention, since the data communication between the control unit and the sensor for the turning behavior is synchronized, it is possible to reliably prevent the response of the turning behavior control from being deteriorated even in the CAN communication. .
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a CAN communication system according to an embodiment of the present invention.
FIG. 2 is a diagram showing data contents of one frame transmitted by each node constituting the CAN communication system of the present embodiment.
FIG. 3 is a diagram illustrating a transmission principle of a CAN communication system.
FIG. 4 is a diagram schematically showing exchange of data communication between the 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 the present 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 (6)

A CAN communication system comprising a plurality of nodes connected to each other via a CAN bus, each having a CAN controller,
If the first node needs data from at least one second node, it sends a trigger frame to which data should be sent towards the CAN bus; and
When the second node receives the trigger frame from the first node, the second node samples data at the time when the trigger frame is received, and the data obtained as a result is to be transmitted as the data to be transmitted. The CAN communication system characterized by transmitting to. The first node transmits the trigger frame at a predetermined period; and
2. The data transmission device according to claim 1, wherein the second node transmits data to be transmitted toward the CAN bus even when the state where the trigger frame is not received continues beyond the predetermined period . CAN communication system . The said 2nd node transmits the data which added the trigger which distinguishes both with the case where the said trigger frame is received, and the case where it is not received toward the said CAN bus | bath . CAN communication system. When the first node transmits a trigger frame toward the CAN bus and the state in which data from the second node is not received continues for a predetermined time, the first node communicates with the second node or communication system. The CAN communication system according to any one of claims 1 to 3, wherein it is determined that a failure has occurred . Wherein each of the first is the node and the second node, the CAN of any one of claims 1 to 4, wherein the priority on the CAN bus is relatively high node among all the nodes Communications system. The first node is a control unit for controlling the turning behavior of the vehicle; and
The CAN communication system according to any one of claims 1 to 5, wherein the second node is a sensor that outputs a parameter necessary for controlling the turning behavior of the vehicle .

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