WO2018121349A1

WO2018121349A1 - Can bus control method and communication system using can bus

Info

Publication number: WO2018121349A1
Application number: PCT/CN2017/117204
Authority: WO
Inventors: 吕玉华
Original assignee: 蔚来汽车有限公司
Priority date: 2016-12-30
Filing date: 2017-12-19
Publication date: 2018-07-05
Also published as: CN106921546A

Abstract

The present invention provides a CAN bus control method, comprising: configuring all nodes connected to a CAN bus to use a unified clock; and making all the nodes send packets on the CAN bus according to a unified plan after all the nodes are powered on and initialized. In addition, the present invention also provides a communication system using a CAN bus, comprising: a CAN bus; and a plurality of nodes connected to the CAN bus, wherein each of the plurality of nodes is configured to use a unified clock, and each of the plurality of nodes sends a packet on the CAN bus according to a unified plan after all of the plurality of nodes are powered on and initialized.

Description

CAN bus control method and communication system using CAN bus

Technical field

The present invention generally relates to the field of controller area network CAN bus communication technology, and in particular, to a CAN bus communication method and a communication system using the CAN bus.

Background technique

CAN is an abbreviation of Controller Area Network (CAN). The CAN bus is a digital signal communication protocol designed by Bosch in Germany to solve complex technical problems in automotive monitoring systems. It is a bus serial communication network. The CAN bus is a car LAN that is extremely suitable for automotive environments, and it has the advantages of reliability, real-time and flexibility in data transmission.

As the degree of electronic electronics is getting higher and higher, the amount of communication data is getting larger and larger, and the load carrying capacity of the CAN bus is also getting higher and higher. However, due to hardware constraints, the CAN bus communication quality may not be ideal under high load ratio conditions, such as signal delay or even frame loss.

Therefore, what is desired is to design a solution that can increase the CAN bus communication load rate under current hardware conditions while ensuring communication quality.

Summary of the invention

In view of this, the present invention provides a CAN bus control method, which includes: setting all nodes connected to a CAN bus to adopt a unified clock; and making all nodes follow a unified plan after all nodes are powered on and initialized. A message is sent on the CAN bus.

The method as described above, wherein the unified planning comprises: setting a different packet start time delay length for each node.

The method as described above, wherein the packet start transmission delay time length is set according to the priority of each message.

The method as described above, wherein the unified planning further comprises: setting, for each node, a different start transmission delay length according to a type of the message.

The method as described above, wherein the unified planning further comprises: setting a minimum transmission time interval for the event message.

The method as described above, wherein the unified planning further comprises: dynamically changing a transmission time period of the message according to the importance degree of the message.

The method as described above, wherein the importance of the message is determined according to the function of the message.

The method as described above, wherein the message comprises an event message and a periodic message.

In another aspect, the present invention also provides a communication system employing a CAN bus, comprising: a CAN bus; and a plurality of nodes connected to the CAN bus, wherein each of the plurality of nodes is set to A unified clock is employed, and each of the plurality of nodes transmits a message on the CAN bus in accordance with a unified plan after all of the plurality of nodes are powered up and initialization is completed.

DRAWINGS

The foregoing and other objects, features, and advantages of the invention will be apparent from

1 is a flow chart of a CAN bus control method in accordance with one example of the present invention.

2 is a schematic diagram of a CAN bus message transmission situation according to an example of the present invention.

3a-3b are diagrams showing the transmission of a CAN bus message in accordance with another example of the present invention.

4 is a communication system employing a CAN bus in accordance with one example of the present invention.

detailed description

BRIEF DESCRIPTION OF THE DRAWINGS Exemplary embodiments of the present invention will now be described with reference to the drawings, wherein like reference numerals refer to the like. The examples described below are provided to enable those skilled in the art to understand the invention, and the examples are intended to be illustrative and not limiting. The illustrations of the various elements, components, modules, devices and device bodies in the figures are only illustrative of the existence of such elements, components, modules, devices, and device bodies, and also indicate the relative relationship between them, but are not intended to limit their specificity. Shape; the relationship of the steps in the flowchart is not limited to the order given, and can be adjusted according to the actual application without departing from the scope of protection of the present application.

In this context, by way of example and not limitation, the CAN bus control method will be described in the vehicle as an example, and more specifically, the vehicle is an electric vehicle. The term "node" refers to a component, component, part, device, or system in a vehicle that uses the CAN bus to transmit message data.

1 is a flow chart of a CAN bus control method in accordance with one example of the present invention. As shown in FIG. 1, first all the nodes connected to the CAN bus are set to adopt a unified clock in step 11; and in step 13, after all nodes are powered on and initialized, all nodes are uniformly planned on the CAN bus. Send a message.

In practice, a unified plan as described above may be pre-set for each node, and the set clock and the planned message transmission scheme may be pre-loaded to each node to power on all nodes connected to the CAN bus. The CAN message can then be sent according to the above unified plan.

Simply put, according to the conventional CAN bus message transmission mode, each message has a certain priority according to its ID (in conventional applications, the smaller the ID value is, the higher the priority), but because each node follows The respective timings are transmitted on the CAN bus, and many messages with high priority still have to wait for idle on the bus to be successfully transmitted. In this way, most high-priority messages are delayed for a long time to be sent.

The communication of the various nodes on the CAN bus, especially for in-vehicle communication, is often predictable. Therefore, according to the CAN bus control method exemplified by the present invention, according to the function of each node, planning for message transmission in advance can preferentially avoid many unnecessary conflicts on the bus.

In some examples, the unified plan includes setting a different packet start delay length for each node. Since all nodes on the same CAN bus use the same clock, this makes it possible for each node to start transmitting messages at the specified time. By enabling each node on the CAN bus to start message transmission with different delay times after all power-on, it avoids the situation that multiple messages are simultaneously transmitted at the same time, thereby greatly alleviating packet congestion on the bus.

In some examples, the length of time the message is sent is set according to the priority of the message. In this case, in the case where a plurality of high-priority messages are to be transmitted, they may also be transmitted in a pre-planned time sequence. In other words, different priorities of the messages are staggered from each other in advance planning to avoid A burst condition existing when an existing CAN bus message is transmitted.

For example, the message containing the brake information during the running of the vehicle and the message containing the throttle information have high priority. According to the conventional CAN bus transmission mode, they may require simultaneous transmission, thereby causing a conflict situation. In the case that the subsequent transmission of the message through the CAN bus, the two messages will always conflict. However, according to the present invention, it is pre-planned at which time point the message containing the brake information is sent, and at what time point the message containing the throttle information is sent. Specifically, the message including the brake information is scheduled to be transmitted at time t0. And the message containing the throttle signal is transmitted at time t0 + σ1, thereby avoiding the conflict between the two. It should be noted that the pre-planned t0 and t0+σ1 refer to the time when the two messages are sent for the first time after the CAN bus is powered on. Because each message has a certain transmission period, conflicts can be avoided in subsequent transmissions.

For each node, different start transmission delay lengths can be further set according to the type of the message. For example, an event message (eg, a message including brake information, collision information, and the like that is not always occurring) may be determined to have a higher priority than a periodic message (eg, a message including a round speed). Therefore, the length of the start transmission delay of the event message is set smaller than the periodic message. That is to say, each node starts to send a delay time for different messages for different first-to-be-sent messages after power-on. Thereby, it is possible to avoid a delay set in advance so that a message having a high priority itself is unreasonably delayed to be transmitted.

For example, for a periodic message, when the time is planned for it, its transmission period may be T1, and for an event message, its transmission period may be smaller than T1.

After the node starts to send packets, it can further change the sending time period of the packets according to the importance of the packets. Figure 2 is a schematic diagram of CAN bus message transmission in such cases. For example, for some periodic messages, they are predetermined to be transmitted in a period of time length T1. However, during the communication process, the importance of these messages may change, for example, the importance is increased, resulting in an increase in the priority of these messages. In this case, the nodes transmitting these messages can be configured to transmit these messages in a shorter period of time T2. For example, the message including the brake information mentioned above has an extremely high priority during the running of the vehicle, but when the vehicle is in a state of charging or the like, the message has a low priority, correspondingly The transmission cycle for it will be adjusted longer.

The variable period transmission of the message can also be pre-configured or planned in the node, that is, each node can adjust the message transmission based on the pre-configuration or planning of the packet transmission plan in the node based on the form state, mode, and the like of the vehicle. The cycle and so on. In other words, for example, the importance level can be sorted according to the functions implemented by the message on the CAN bus, and the transmission period of the message is determined accordingly. This can for example be stored on the node in the form of a list. Each node can adjust the corresponding transmission period according to the importance of the message on the bus. This can significantly reduce the load rate, thereby further improving the communication quality.

Further, a minimum transmission time interval can also be set for the event message. Figures 3a and 3b show schematic diagrams of CAN bus message transmission without this setting and with this setting. Typically, event messages are typically sent on the CAN bus as quickly as possible, thereby causing the cycle of other messages on the bus to be affected. FIG. 3a is a message sequence in which the event message does not set a minimum time interval from the previous message. As shown in FIG. 3a, when the event message is continuously transmitted at a very short time interval T2, the periodic message originally transmitted in the time period T2 cannot maintain the previous transmission timing due to the continuous transmission of the event report. The interval between the two messages is extended to T3, causing a delay in the cycle and the communication quality is lowered.

Figure 3b is a message sequence after setting a minimum transmission time interval for an event message, wherein the event message is set to be transmitted at least at time interval T2 between each message, thereby ensuring a period of T1 The periodic message is not delayed in the period during which the event message is sent, thereby improving the communication quality.

4 is a communication system employing a CAN bus in accordance with one example of the present invention. The CAN bus communication system according to the present invention can be used in a typical network topology. In such a network topology, multiple CAN buses can be included, and communication between different CANs is reproduced through the gateway. On each CAN, each of a plurality of nodes (A, B, C, ...) connected to the CAN bus can be set to use a unified clock, and each of the nodes is on the CAN bus. After all nodes are powered on and initialized, the packets are sent on the same CAN bus according to the unified plan. All of the other settings described above also apply to the example shown in FIG.

It should be noted that the above specific embodiments are merely illustrative of the technical solutions of the present invention and are not limited thereto. While the invention has been described in detail herein with reference to the preferred embodiments of the embodiments of the invention All are covered by the scope of the claimed invention.

Claims

A CAN bus control method includes:

Set all nodes connected to the CAN bus to use a unified clock;

After all the nodes are powered on and the initialization is completed, all the nodes are sent on the CAN bus according to a unified plan.
The CAN bus control method according to claim 1, wherein said unified planning comprises: setting a different packet start delay length for each node.
The CAN bus control method according to claim 1, wherein the message transmission delay time length is set according to the priority of each node message.
The CAN bus control method according to claim 2, wherein said unified planning further comprises: setting, for each node, a different start transmission delay time length according to a type of the message.
The CAN bus control method according to claim 2, wherein the unified planning further comprises: setting a minimum transmission time interval for the event message.
The CAN bus control method according to claim 2, wherein the unified planning further comprises: dynamically changing a transmission time period of the message according to an importance degree of the message.
The CAN bus control method according to claim 6, wherein the importance of the message is determined according to the function of the message.
The CAN bus control method according to claim 2, wherein the message comprises an event message and a periodic message.
A communication system using a CAN bus, comprising:

CAN bus; and

Connected to multiple nodes of the CAN bus,

Wherein each of the plurality of nodes is configured to adopt a unified clock, and each of the plurality of nodes is in accordance with a unified plan on the CAN bus after all of the plurality of nodes are powered on and initialized Send a message on.