CN105182847A - High-reliability dual-redundant CAN bus communication method applied in motion control system - Google Patents

Abstract

Provided is a high-reliability dual-redundant CAN bus communication method applied in a motion control system. The method comprises: (1) using two CAN buses A and B for communication between a main controller and each joint controller; (2) initializing the two CAN buses; (3) the main controller sending joint position instructions of the joint controllers to each joint controller through the A bus and the B bus in an instruction sending period of a control period in a time sharing manner, and after sending, sending broadcast instructions to the A bus and the B bus; (4) each joint controller receiving the joint position instruction message through inquiring the A bus and the B bus, and analyzing and storing the instruction message which is received first; (5) each joint controller receiving broadcast instructions through inquiring the A bus and the B bus, after broadcast instructions are received, moving according to the analytic instruction message, and acquiring current state information, sending the respective state information to the main controller in timer interruption in a time sharing manner; and the next control period starting to execute from the step (3).

Description

A Highly Reliable Dual Redundant CAN Bus Communication Method Applied to Motion Control System

technical field

The invention relates to a CAN bus communication method, in particular to a highly reliable dual redundant CAN bus communication method applied to a motion control system.

Background technique

The distributed motion control system includes a main controller and several joint controllers. The main controller mainly completes the planning of the motion path, sends the planned position instructions to each joint controller, and collects the position information of each joint at the same time for the follow-up The trajectory of the movement is prepared. A fast and reliable communication method needs to be established between the main controller and the joint controller. Most of the previous communication methods choose to establish point-to-point serial communication or analog communication between the main controller and each joint controller. Each joint controller is independent of each other and lacks a highly reliable high-speed communication link.

Contents of the invention

The technical problem of the present invention is to overcome the deficiencies of the prior art and provide a highly reliable dual-redundancy CAN bus communication method applied to a motion control system.

The technical solution of the present invention is: a highly reliable dual redundant CAN bus communication method applied to a motion control system, wherein the motion control system includes a main controller and at least two joint controllers; the steps are as follows:

(1) Two CAN buses are used for communication between the main controller and each joint controller. The two CAN buses are recorded as A bus and B bus as backups for each other and the hardware circuits are independent of each other. Each CAN bus can receive data , can also send data;

(2) Initialize two CAN buses, and set the communication protocol of the CAN buses;

(3) The main controller sends the joint position commands of each joint controller to each joint controller through the A bus and the B bus in time-sharing during the command sending period of the control cycle, and sends broadcast commands to the A bus and the B bus after the transmission is completed ; The control cycle includes a command sending period and a joint state information return period, wherein the joint state information return period adopts a timing interruption method for communication;

(4) Each joint controller receives the joint position instruction message of the main controller by querying the A and B buses, and parses the first received instruction message and saves it in the memory;

(5) Each joint controller receives the broadcast command by querying the A and B buses. After receiving the broadcast command, each joint controller moves according to the parsed command message at the same time, and collects the current status information. The respective state information is sent to the main controller; the next control cycle starts from step (3) and executes cyclically.

Monitor the data receiving status of A bus and B bus in real time during the timing interrupt. When a bus does not receive an instruction message from the master controller for t consecutive times, it will initialize the bus immediately, switch the communication to another bus, and wait to enter In the next control cycle, the redundant mode of two buses is restored, and the t is at least two control cycles.

Monitor the state of bus A and bus B in real time during the timing interrupt, read the CAN bus error flag every certain time t, when the error flag is set, initialize the bus immediately, switch the communication to another bus, After entering the next control cycle, restore the redundant mode of two buses, and the said t is at least two control cycles.

Compared with the prior art, the present invention has beneficial effects as follows:

(1) The present invention proposes a communication method using dual redundant CAN bus as a physical link, and establishes a digital communication highway between a main controller and multiple joint controllers by customizing the CAN bus communication protocol , which solves the problems of low reliability, slow communication rate, poor synchronization of multiple joint movements, and limited transmitted information in the distributed motion control system.

(2) Two independent CAN buses are used to realize hardware dual-redundancy hot backup, real-time monitoring of data information and real-time detection of CAN bus hardware status are used to realize the stripping of faulty CAN buses, and online switching is used to realize quick reset of faulty CAN buses , providing a guarantee for the reliability of dual redundant CAN bus communication;

(3) For multiple joint sites, the method of time-sharing transmission of command data and synchronous start of broadcast messages is adopted to improve the real-time performance of the bus, which solves the disadvantage of poor synchronization of multiple joint motions, improves the real-time performance of the motion system, and greatly enhances the connection between multiple joints. Coordinated movement between.

Description of drawings

Fig. 1 is the topological structure diagram of the dual redundant CAN bus of the present invention;

Fig. 2 is a schematic diagram of the control cycle of the motion control system of the present invention;

Fig. 3 is the flow chart of real-time monitoring of CAN bus data information of the present invention;

Fig. 4 is a flow chart of the real-time monitoring of CAN bus hardware status in the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments. The present invention relates to a highly reliable dual redundant CAN bus communication method applied to a motion control system. The motion control system includes a main controller and at least two joints Controller; this example takes seven joint controllers as an example for illustration. Specific steps are as follows:

(1) Two CAN buses are used for communication between the main controller and each joint controller (the topology structure of the dual redundant CAN bus is shown in Figure 1), and the two CAN buses are marked as A bus and B bus as mutual Backup and hardware circuits are independent of each other, each CAN bus can receive data and send data, that is, form independent dual redundant CAN bus communication;

(2) Initialize two CAN buses, and set the communication protocol of the CAN buses;

The main controller and each joint controller carry out digital communication through two identical CAN buses, and the instruction messages sent by the main controller to the joint controllers are divided into two types: control instructions and broadcast instructions. The role of the broadcast command is to synchronize the movement of each joint and determine the return frame information. There is only one kind of message returned by each joint controller to the main controller: status return message. The status return message returns information such as the joint position information collected by the joint controller to the main controller, which is used for the main controller to adjust the motion trajectory at any time.

In the present invention, the definitions of the communication protocols of CAN bus A and B can be selected to be completely the same, and the definitions of messages are shown in the following table.

Considering the high real-time requirements of the motion control system, the communication rate of CAN bus A and B can be selected as 1Mbit/s, and the total time for the main controller to send 7 position messages to the 7 joint controllers is about 0.7ms , the time to send a broadcast message is about 0.1ms.

Theoretical calculations and test results show that the time difference between the main controller completing one path planning and sending the seven joint position command signals to the seven joint controllers, and starting the simultaneous motion of the joints is about 0.8ms, which is shorter than the previous serial data such as RS232. Transmission has been greatly improved. It meets the strong requirements of the distributed motion control system on the communication rate.

(3) The main controller sends the joint position commands of each joint controller to each joint controller through the A bus and the B bus during the command sending period of the control cycle, and sends broadcast commands to the A bus and the B bus after the sending is completed; The control period described above includes the command sending period and the joint state information return period, wherein the joint state information return period adopts the method of timing interruption for communication; for example, as shown in Figure 2, the control period of the motion control system is 20ms, and the command sending period The duration is 2ms. During the 2ms period, the main controller distributes control instructions (joint position instructions) to each joint controller. After completing the distribution of each joint control instruction, the main controller finally sends a broadcast frame instruction to synchronize the movement of each joint. .

(4) Each joint controller receives the joint position instruction message of the main controller by querying the A and B buses, and parses the first received instruction message and saves it in the memory;

(5) Each joint controller receives the broadcast command by querying the A and B buses. After receiving the broadcast command, each joint controller moves according to the parsed command message at the same time, and collects the current status information. The respective state information is sent to the main controller; the next control cycle starts from step (3) and executes cyclically.

The joint status information returned by the joint controller is not at the same time, but in time-sharing, so as to reduce the load rate of the communication bus. For example, the No. 1 joint controller will give feedback immediately after receiving the broadcast frame. If multiple frames of data are fed back, the frame There is a delay of two PWM cycles between the frame and the frame; the No. 2 joint controller delays 40 timing cycles after receiving the broadcast frame for feedback. If multiple frames of data are fed back, the delay between frames is two PWM cycles; 3 After receiving the broadcast frame, the No. joint controller delays 80 timing cycles for feedback. If multiple frames of data are fed back, the frame-to-frame delay is two PWM cycles, and so on. Therefore, the bus load rate of the system can be reduced by sending data in time division, and the reliability of the system can be improved.

In order to improve the reliability, real-time monitoring of data information and real-time monitoring of CAN bus hardware status are used in the timing interrupt to realize the stripping of faulty CAN bus. The real-time monitoring of data information means that when a certain CAN bus does not receive an instruction message from the main controller for 50ms, it indicates that there is an error in the communication, and the CAN bus is initialized immediately, and the communication is switched to another CAN bus at the same time. Control cycle, the way to restore the redundancy of the two buses. The real-time monitoring of the CAN bus hardware status is to read the CAN bus error flag at regular intervals during the timing interrupt (this is the error flag that comes with the DSP chip, and it is mainly used to represent the communication status of the CAN bus, such as whether there is a format on the CAN bus Error, whether there is a filling error), if the error flag is set, the CAN bus will be initialized immediately, and the communication will be switched to another CAN bus at the same time. After entering the next control cycle, the redundant mode of the two buses will be restored . Therefore, the double redundant CAN bus fault monitoring and real-time switching method solves the low reliability in the past communication process and improves the security of the system. The flowchart of real-time monitoring of CAN bus data information is shown in Figure 3, and the flowchart of real-time monitoring of hardware status is shown in Figure 4.

Parts not described in detail in the present invention belong to the common knowledge of those skilled in the art.

Claims (3)

1. A highly reliable dual redundant CAN bus communication method applied to a motion control system, wherein the motion control system includes a master controller and at least two joint controllers; it is characterized in that the steps are as follows: (1) Two CAN buses are used for communication between the main controller and each joint controller. The two CAN buses are recorded as A bus and B bus as backups for each other and the hardware circuits are independent of each other. Each CAN bus can receive data , can also send data; (2) Initialize two CAN buses, and set the communication protocol of the CAN buses; (3) The main controller sends the joint position commands of each joint controller to each joint controller through the A bus and the B bus in time-sharing during the command sending period of the control cycle, and sends broadcast commands to the A bus and the B bus after the transmission is completed ; The control cycle includes a command sending period and a joint state information return period, wherein the joint state information return period adopts a timing interruption method for communication; (4) Each joint controller receives the joint position instruction message of the main controller by querying the A and B buses, and parses the first received instruction message and saves it in the memory; (5) Each joint controller receives the broadcast command by querying the A and B buses. After receiving the broadcast command, each joint controller moves according to the parsed command message at the same time, and collects the current status information. The respective state information is sent to the main controller; the next control cycle starts from step (3) and executes cyclically. 2. A kind of highly reliable dual-redundant CAN bus communication method applied to motion control system according to claim 1, is characterized in that: monitor the data receiving status of A bus and B bus in real time in timing interruption, when a certain When the bus does not receive an instruction message from the master controller for t consecutive times, the bus is initialized immediately, the communication is switched to another bus, and after entering the next control cycle, the redundancy mode of the two buses is restored, and the t is at least two control cycles. 3. according to claim 1 and 2 described a kind of highly reliable double redundant CAN bus communication method that is applied to motion control system, it is characterized in that: monitor the state of A bus, B bus in real time in timing interruption, every certain Time t reads the CAN bus error flag. When the error flag is set, the bus is initialized immediately, and the communication is switched to another bus. After entering the next control cycle, the redundant mode of the two buses is restored. Said t is at least two control cycles.