KR20110035247A - Method for id transformation in can-based network - Google Patents

Abstract

PURPOSE: An ID dynamic allocating method of a CAN based system is provided to perform a different operation by using a time stamp function of CAN without using a timer. CONSTITUTION: A changing area value of an ID is read out(S401). The transmission delay of a message is compared with a deadline value(S402). An order of a deadline is calculated(S403). The order is assigned based on the deadline of a changing area(S404). The initialization of the order is identified(S406). The current weight is compared with an initial weight(S408). An ID message of a transmission frame is recorded in a changing area(S405).

Description

ID dynamic allocation method in a CAN-based system {Method for ID transformation in CAN-based network}

The present invention relates to an ID dynamic allocation method in a CAN based system. More specifically, the present invention relates to an ID dynamic allocation method for dynamically converting a transmission authority of a message in a CAN-based vehicle network.

Recently produced and sold automobiles include Anti-Break System (ABS) system, Air-bag system, Attitude Control System (TCS), Headlight Control System (AFS), Cruise Control System (VCC), Advanced High Safety Many electronic control devices are being applied, including automotive electronics, telematics, and intelligent transportation systems (ITS). Such advanced systems will be increasingly required for the safety and convenience of automobiles, and the related electronic equipment will grow exponentially.

In addition, hybrid vehicles, which are being released in combination with existing engines and batteries / fuel cells, are expected to replace conventional fossil fuel vehicles due to environmental regulations. Such hybrid vehicles require much more electronic equipment. Shall be. The advent of hybrid cars is expected to accelerate the number of related electronic devices associated with the implementation of advanced systems in cars.

The above electronic control devices in the vehicle are one-way or two-way communication between the sensing unit, the sensor and the operating unit such as sensors, etc. Currently, most of the electronic control units (ECUs) are CAN network protocols for vehicles. (Controller Area Network) Messages connected to the communication network are required for various control.

CAN is a serial network communication scheme designed to be applied to the automotive industry in the early days. Recently, CAN is widely applied not only to the automobile field but also to all industries, and the basic CAN network system configuration applied to the automobile field is shown in FIG. 1. CAN is a bus for communication between microcontrollers and performs data communication with an electronic control unit (ECU) of a vehicle, a transmission control unit (TCU), and a microcontroller of ABS. The CAN may exchange information between devices by connecting a plurality of devices having unique IDs through a single bus. The CAN uses a physical layer, a data link layer, and an application layer among the OSI 7 layers.

As shown in FIG. 1, the CAN network system includes a plurality of nodes, and message transmission and reception between each node 2 is performed through the CAN bus 1. Here, each node 2 becomes a plurality of electronic devices (ECUs) that perform a corresponding operation by transmitting and receiving a message.

 The message used in the network system does not include the address of the sender or the receiver, but includes only identifier (ID) information of the receiver. The CAN bus 1 assigns a unique identifier (ID) to each of the plurality of nodes 2 or the plurality of electronic devices 2 in accordance with the CAN protocol. Since this is in accordance with known techniques, a detailed description thereof will be omitted. An electronic device (ECU) connected to each node of the CAN bus 1 obtains a message transmitted via the CAN bus 1. If the identifier of the message is the same as its identifier, the acquired message is accepted as an input message, and the operation is performed accordingly.

In the case of CAN, various error detection mechanisms and retransmission capabilities ensure high reliability and availability of data, and are currently widely used in vehicles worldwide. In addition, there is an advantage that can effectively mediate message collisions in a network system under relatively low traffic conditions. However, in a high traffic condition system in which a plurality of sensors and actuators are generated and a large number of periodic messages are generated, such as the chassis network of an intelligent vehicle, which is being actively developed in recent years, the average transmission delay is suddenly shown in FIG. It is showing increasing characteristics.

The present invention is designed to solve the above problems,

An object of the present invention is to provide an ID dynamic allocation method that can reduce the maximum transmission delay time of a message generated by each control device in a CAN-based system.

Another object of the present invention is to provide an ID dynamic allocation method in which the system is not overloaded.

It is still another object of the present invention to provide an ID dynamic allocation method that can guarantee different transmission delay limits required by messages generated by each control device in a CAN-based system.

It is still another object of the present invention to provide an ID dynamic allocation method for changing the priority of messages generated by each control device to give a minimum transmission opportunity to messages having a relatively low priority.

It is still another object of the present invention to provide an ID dynamic allocation method with a short transmission delay measurement process.

In the CAN-based system of the present invention, the ID dynamic allocation method includes: measuring a transmission delay of a message by monitoring a transmission time of the message; And assigning priorities of messages occurring in the system based on the deadline time.

In particular, the transmission delay measurement step, the time from the time the message is stored in the buffer using the CAN time-stamp function to the time when the end of file (EOF) of the message transmitted on the CAN bus appears It is characterized in that for calculating the transmission delay of the message using.

In addition, the ID dynamic allocation method in the CAN-based system is characterized in that it follows the standard of CAN 2.0 B having an ID of 29 bits.

In addition, the ID dynamic allocation method in the CAN-based system is characterized by dividing a data frame into three regions of an arbiter field having an ID of 29 bits.

The moderator field may include a 2 bit message type zone for distinguishing classes of different message types; A changing zone comprising a count portion of which the transmission delay exceeds the deadline and a weight portion based on the deadline; And an area to which the initial ID given in the network design is applied.

In addition, in the CAN-based system, the ID dynamic allocation method may reduce the number of changing zones of each ID by 1 when the transmission delay of the message is greater than or equal to the deadline, and the deadline in the transmitted order. It is reduced by the order exceeding, and assigned to the weight of the current changing zone. If the transmission delay does not exceed the deadline, the count is maintained to maintain the initial value of the changing zone of each ID. Substituting the initially set value, the weight is characterized by increasing one by one.

The ID dynamic allocation method according to the present invention can expect the following effects.

First, the exact priority of messages occurring at each node can be determined, reducing the transmission delay time.

Second, it only determines the deadline of each message, so there is no need to change the time axis as the network changes.

Third, by using the time-stamp function of CAN without using a timer, the system is not overloaded, allowing the system to perform other operations.

Hereinafter, the most preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. First, in adding reference numerals to the components of each drawing, the same components have the same reference numerals as much as possible even though they are displayed on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, a detailed operation of an ID dynamic allocation method in a CAN system according to the present invention will be described with reference to the accompanying drawings.

3 shows a data frame structure of the ID conversion algorithm according to the present invention.

It is composed based on the data frame defined in the CAN 2.0 B standard and only the Arbitration Field, which can have an ID of 29 bits, is divided into three areas. Therefore, it is basically compatible with the basic protocol of CAN which is widely used, and it is possible to adjust ID dynamically.

Like hard real time messages or soft real time messages, messages generated by the system have different requirements. In particular, there is an urgent message in which transmission should be given priority over any message type. A message type area of 2 bits for distinguishing classes of different message types is allocated to the first area of the Arbitration Field to classify the message types. The changing zone that determines the priority of the messages actually sent is the part that uses the ID translation algorithm. It is divided into a count part and a weight part and allocated to the second area. The last area is the area that applies the initial ID given in the network design. This section has the function of identifying the original message and guaranteeing the existing priority of the message even if the ID of the changing zone of the ID is the same during the operation of the dynamic ID allocation scheme.

Transmission delay measurement of the ID conversion algorithm needs to measure the transmission delay of the message. This process uses the CAN Time-stamp function to automatically record the time from the moment the message is stored in the buffer to the time the EOF of the message sent on the CAN bus appears. This time is used to calculate the transmission delay of the message, and then the procedure for converting the ID is performed.

The ID conversion algorithm logically deals with the number of times the transmission delay exceeds the deadline and the number of weights based on the deadline in the changing zone of each ID. To deal with this part, you must know the order in which messages are sent. To know the transmission order, the frame can be calculated based on the CAN 2.0 B standard. Considering the transmission speed of 500k bps, the maximum data size and the stuff bit size, the time taken for the message to come out of the buffer to the bus line can be calculated as in Equation 1 below.

Here, 67 is the total number of bits of the fields excluding the data field in the extended data frame (CAN 2.0B), and 8 * D is the total number of bits of the length of the data. And (55 + 8 * D) / 5 represents the maximum stuff bit size that a data frame can have. Where τbit is the time taken to transmit 1 bit and is the inverse of the transmission rate. Since the transmission speed is 500k bps, the inverse number is 2㎲, and when the length of data is 8 bytes, it takes about 310㎲ for a message to come out on the bus line. That is, it takes up to 310 ms when a message is sent.

Once you have calculated the transmission time of the message, you know the order in which it was sent. Equation 2 calculates the order in which the messages are transmitted.

Here, TO is the order of transmission and RT is the actual transmission delay. PT is a constant that is a fixed processing time for sending a message in each MCU. C is calculated as shown in Equation 1 as the maximum time of one message. Round [x] returns an 8-bit value to ignore the decimal places because it is an ordered value.

In order to check in which order the deadline must be transmitted, it can be calculated as in Equation 3.

Here, MO indicates the order of the deadline after the deadline, MT is the deadline time, PT is a constant fixed as the processing time for sending a message from each MCU. C is calculated as shown in Equation 1 as the maximum time of one message. Round [x] returns an 8-bit value to ignore the decimal places because it is an ordered value.

Next, a method of substituting a weight in a changing zone is represented by Equation 4.

Next weight = Present weight-(TO-MO)

In this case, the transmission order is reduced by the order of crossing the deadline, and substituted into the weight of the changing zone of the current ID.

4 is a flowchart illustrating an ID conversion algorithm in the process of ID allocation method according to the present invention. The ID conversion algorithm operates after being transmitted according to the period of each message.

The changing area value (count, weight) of the current ID is read (S401).

If the transmission delay of the message is greater than or equal to the deadline (S402), the current order and the order of the deadline are calculated (S403), and the number of times beyond the deadline of the changing zone portion of each ID is counted by one. Decrease and weight convert the deadline order from the current order to the subtracted value. The part that checks the number of weights based on the deadline of the changing zone part is substituted as shown in Equation 4 above (S404).

If the transmission delay does not exceed the deadline, the count substitutes the initially set value and the weight is increased by one in order to maintain the initial value of the changing zone portion of each ID.

Check whether the number of times is initialized (S406), if not initialized is performed (S407).

It is determined whether the weight is smaller than the initial weight value (S408), and if it is a small value, the weight value is increased (S409).

The ID message of the transmission frame, which has undergone such an algorithm, is recorded in the changing area (S405).

5 is an exemplary view showing an embodiment of the operation of such an algorithm. The algorithm is transmitted according to the priority of the message in the order of transmission, like a virtual queue according to the priority of the ID.

As shown in FIG. 5, one message is simultaneously transmitted to each node, and the message is assumed to be the same deadline. Send two hard real-time messages (unique ID: 1, 2) and four soft real-time messages (unique ID 11, 12, 21, 22).

In the first cycle, the IDs 1, 2, 11, 12, 21, and 22 are transmitted in the order of the moderator initial ID according to the priority of the unique ID. Since the delay of sending ID 21, ID 22 message exceeds the deadline, ID 21, 22 message is added with -1 in the count, and ID 21 is the first -1 in the order of deadline. ID 22 is -2 the second time.

In the second cycle, the hard real-time messages ID 1 and 2 are ordered forward by the count and weight changed by the algorithm, and soft real-time. ) The ID 22 message with the lowest ID among the messages is third, and ID 21 is fourth.

If this operation cycle continues, the messages are listed in the same form as the initial priority every eight cycles.

As described above, the exact priorities of the messages generated in each node can be determined to reduce the transmission delay time, and since only the deadline of each message is determined, there is no need to change the time axis as the network changes. In addition, by using the time-stamp function of CAN without using a timer, the system is not overloaded, allowing the system to perform other operations.

As mentioned above, although embodiment of this invention was shown and demonstrated, this invention is not limited to the specific embodiment mentioned above, Comprising: It is common in the art to which this invention pertains without deviating from the summary of this invention claimed in the Claim. Various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the scope of the present invention.

1 is an exemplary view schematically showing a configuration of a CAN network system.

2 is a graph showing the relationship between bus traffic and average transmission delay time.

3 is an exemplary diagram illustrating a functional area of an ID.

4 is a flowchart illustrating an operation procedure of an ID conversion algorithm according to the present invention.

5 is an exemplary view showing an embodiment of the operation of the ID conversion algorithm according to the present invention.

Claims (6)

Monitoring a transmission time of the message to measure a transmission delay of the message; And A method for dynamically assigning IDs in a CAN-based system comprising assigning priorities of messages occurring in the system based on deadline time. The method according to claim 1, The transmission delay measuring step, Using the CAN time-stamp function, the transmission delay of a message is calculated using the time from when the message is stored in the buffer until the end of file (EOF) of the message sent on the CAN bus. Dynamic ID allocation method in a CAN-based system, characterized in that. The method according to claim 1, A method for dynamically assigning IDs in a CAN-based system, characterized by the standard of CAN 2.0 B with an ID of 29 bits. The method of claim 3, An ID dynamic allocation method in a CAN-based system, characterized by dividing a data frame into three regions of an arbiter field having an ID of 29 bits. The method according to claim 4, The moderator field is A 2 bit message type zone for distinguishing classes of different message types; A changing zone comprising a count portion of which the transmission delay exceeds the deadline and a weight portion based on the deadline; And ID dynamic allocation method in a CAN-based system, characterized in that divided into the area to apply the initial ID given in the network design. The method according to claim 5, If the transmission delay of the message is greater than or equal to the deadline, the number of changing zones of each ID is reduced by 1, and the current switching zone is decreased by the order of crossing the deadline in the order of transmission. Is substituted into the weight of If the transmission delay does not exceed the deadline, the CAN-based method is characterized in that the count is substituted for the initial value and the weight is increased by one to maintain the initial value of the changing area of each ID. How to assign IDs dynamically in the system.

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