Communication method of multi-axis linkage equipment control system based on CAN protocol

Abstract

According to the communication method of the multi-axis linkage equipment control system based on the CAN protocol, the technical problems that in the prior art, response is not timely and transmission efficiency is low in CAN bus extension frame communication are solved. According to the communication method of the multi-axis linkage equipment control system based on the CAN protocol provided by the invention, the value of the priority segment P in the CAN extension frame to be generated is determined according to the priority of the CAN message to be sent, and the value of the priority segment P in the CAN extension frame to be generated is determined according to the transmission form of the parameters in the CAN message to be sent. The value of the protocol data unit format PF in the CAN extension frame to be generated is determined, and finally the generated CAN extension frame is determined according to the value of the priority segment P and the value of the protocol data unit format PF.

Description

Technical Field

[0001] This invention relates to a multi-axis linkage equipment control system, and more specifically to a communication method for a multi-axis linkage equipment control system based on the CAN protocol. Background Technology

[0002] Internal communication in multi-axis linkage equipment control systems is one of the foundations for ensuring their coordinated operation and stable functioning. When coordinating and communicating with large-scale nodes in real time, CAN bus extended frame communication is often used.

[0003] In CAN bus extended frame communication, the communication priority mechanism plays an important role. CAN bus extended frame communication uses a non-destructive bit-by-bit arbitration mechanism to control the communication priority, thereby ensuring that critical CAN messages are arbitrated and transmitted within microseconds. However, the existing communication priority mechanism relies entirely on fixed ID values ​​to divide priorities, and cannot be dynamically adjusted according to the CAN message type. Furthermore, it only considers the priority represented by the ID value itself, ignoring the semantic attributes of the CAN message. For example, an emergency CAN message (safe stop command) requires an immediate response, but it can only be responded to after the current frame transmission is completed, which can easily lead to untimely response problems.

[0004] In addition, the CAN bus extended frame communication adopts a single-parameter single-frame transmission mechanism to ensure the reliability of parameter transmission. However, the existing single-parameter single-frame transmission mechanism has low bandwidth utilization, high bus load rate and poor synchronization, resulting in low transmission efficiency. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems of untimely response and low transmission efficiency in existing CAN bus extended frame communication, and to provide a communication method for a multi-axis linkage device control system based on the CAN protocol.

[0006] To achieve the above objectives, the technical solution provided by this invention is as follows: A communication method for a multi-axis linkage equipment control system based on the CAN protocol, characterized by the following steps: S1. The device sending CAN messages determines the value of the priority segment P in the CAN extended frame to be generated based on the priority of the CAN messages to be sent. The priority segment P is used to identify the priority of the CAN messages. The CAN messages are divided into urgent CAN messages, non-urgent CAN messages, and synchronous CAN messages according to their priority from high to low. The non-urgent CAN messages are divided into periodic non-urgent CAN messages and non-periodic non-urgent CAN messages according to their priority from high to low. The device sending CAN messages is a transmitting device within a multi-axis linkage equipment control system. S2. The device sending the CAN message determines the value of the Protocol Data Unit Format PF in the CAN extended frame to be generated based on the parameter transmission format of the CAN message to be sent; the Protocol Data Unit Format PF is used to identify the parameter transmission format of the CAN message, and the parameter transmission format includes multi-parameter transmission. S3. The device sending the CAN message determines the generated CAN extended frame based on the value of the priority segment P and the value of the protocol data unit format PF, and sends it to the device receiving the CAN message to complete the communication of the multi-axis linkage device control system based on the CAN protocol; the device receiving the CAN message is the receiving device in the multi-axis linkage device control system.

[0007] Furthermore, in step S1, the device that sends the CAN message includes a master device and a slave device; The device that sends the emergency CAN message is the master device, and the value of the corresponding priority segment P is 000, with a priority of 0. The device that sends the non-periodic, non-urgent CAN message is the master device, with a priority segment P value of 010 and a priority of 2; or, the device that sends the non-periodic, non-urgent CAN message is the slave device, with a priority segment P value of 011 and a priority of 3. The device that sends the periodic non-urgent CAN message is the master device, with a priority segment P value of 100 and a priority of 4; or, the device that sends the periodic non-urgent CAN message is the slave device, with a priority segment P value of 101 and a priority of 5. The device that sends the synchronous CAN message is the master device, and the value of the corresponding priority segment P is 111, with a priority of 7. The lower the priority, the higher the priority.

[0008] Furthermore, in step S2, the parameter transmission format is multi-parameter transmission; When the transmission parameters are the target positions of any two drive shafts, the value of the protocol data unit format PF is 00001010; When the transmission parameters are the target rotational speeds of any two drive shafts, the value of the protocol data unit format PF is 00001011; When the transmission parameters are the target torques of any two drive shafts, the value of the protocol data unit format PF is 00001100; When the transmission parameters are the target position and target speed of a single drive shaft, the value of the protocol data unit format PF is 00001101; When the transmission parameters are the actual position, status word, and fault code of a single drive shaft, the value of the protocol data unit format PF is 00101001; When the transmission parameters are the actual speed, current, voltage, and temperature of a single drive shaft, the value of the protocol data unit format PF is 00101010.

[0009] Furthermore, in step S2, the parameter transmission format also includes single-parameter transmission and synchronization signal transmission; When the parameter transmission form is single-parameter transmission, the transmitted parameter is a single parameter of a single drive shaft, and the value of the protocol data unit format PF is 00000001. When the parameter transmission form is synchronous signal transmission, the value of the protocol data unit format PF is 01010000.

[0010] Furthermore, in step S1, the priority segment P is also reserved with values ​​of 001 and 100, which represent the first reserved identifier and the second reserved identifier, respectively.

[0011] Furthermore, in step S2, the value of the protocol data unit format PF is also reserved for values ​​from 01010001 to 11101111, which respectively represent the reserved identifiers from 01010001 to 11101111.

[0012] Further, in step S3, the device receiving the CAN message parses the received CAN extended frame according to a preset parsing rule, determines the priority processing order of the corresponding CAN message by extracting the value of the priority segment P, and determines the parameter transmission format of the corresponding CAN message by extracting the value of the protocol data unit format PF.

[0013] The beneficial effects of this invention are: 1. This invention provides a communication method for a multi-axis linkage equipment control system based on the CAN protocol. By classifying CAN messages according to priority and combining it with a communication priority mechanism, it achieves rapid response to sudden emergencies and solves the problem of untimely response in multi-axis linkage equipment control systems. 2. The present invention provides a communication method for a multi-axis linkage equipment control system based on the CAN protocol. By using a single protocol data unit to control multiple physical parameters, it avoids data conflicts in emergency situations, improves bandwidth utilization, and reduces the total load rate of the bus, thereby solving the problem of low transmission efficiency in multi-axis linkage equipment control systems. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the CAN extended frame structure of an embodiment of a communication method for a multi-axis linkage device control system based on the CAN protocol according to the present invention. Figure 2This is a schematic diagram of the parameter group numbering structure of an embodiment of a communication method for a multi-axis linkage equipment control system based on the CAN protocol according to the present invention. Figure 3 This is a schematic diagram of a CAN communication model, representing an embodiment of a communication method for a multi-axis linkage equipment control system based on the CAN protocol according to the present invention. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] This embodiment discloses a communication method for a multi-axis linkage equipment control system based on the CAN protocol, comprising the following steps: S1. The device sending the CAN message determines the value of the priority segment P in the CAN extended frame to be generated according to the priority of the CAN message to be sent; the priority segment P is used to identify the priority of the CAN message; the CAN messages are divided into urgent CAN messages, non-urgent CAN messages, and synchronous CAN messages according to their priority from high to low; the non-urgent CAN messages are divided into periodic non-urgent CAN messages and non-periodic non-urgent CAN messages according to their priority from high to low. Users can apply the messages to be transmitted to the corresponding CAN messages as needed. Data transmission messages should use a lookup table method to establish logical connections between nodes, ensuring the data content is understandable to both parties. Each CAN message carries the address information of the data producer and the address information of the CAN message to be received.

[0017] For emergency CAN messages, when a serious fault occurs inside a device, an emergency object is triggered and sent from one device to other devices with high priority. It can be transmitted in the form of broadcast or one-to-one transmission. The transmitted content is a safe stop command or fault code feedback.

[0018] For non-urgent CAN messages, the data generating device sends them to one or more receiving devices. These CAN messages can be transmitted periodically or aperiodically. Parameters can be sent or fed back periodically, or parameters can be read or written aperiodically.

[0019] For synchronous CAN messages, the master device, i.e., the controller, should be configured in the CAN bus as the producer node for the synchronous message, providing synchronization signals to the slave devices, i.e., the drivers. When the slave device receives this signal, it should perform the synchronization task according to the predefined execution process.

[0020] The priority allocation of CAN messages is shown in Table 1. Priority segment P occupies 3 bits, dividing all CAN message priorities into 8 levels, with priority 0 being the highest and priority 7 the lowest. The CAN message priorities from highest to lowest are: urgent messages, non-urgent messages, and synchronization messages. The priority setting for the same type of message should be based on the message's importance, transmission frequency, data length, and real-time requirements. As shown in Table 1, the sending device for urgent CAN messages is the master device, with a priority segment P value of 000 (binary to decimal 0) and a priority of 0. The sending device for non-periodic, non-urgent CAN messages is the master device, with a priority segment P value of 010 (binary to decimal 2) and a priority of 2. The sending device for non-periodic, non-urgent CAN messages is the slave device, with a priority segment P value of 011 (binary to decimal 3) and a priority of 3. The sending device for periodic, non-urgent CAN messages is the master device, with a priority segment P value of 011 (binary to decimal 3) and a priority of 3. 100, decimal is 4, priority is 4; the sending device of the periodic non-urgent CAN message is the slave device, the corresponding priority segment P value is binary 101, decimal is 5, priority is 5; the sending device of the synchronous CAN message is the master device, the corresponding priority segment P value is binary 111, decimal is 7, priority is 7; when the priority segment P value is binary 001, decimal is 1, it represents the first reserved identifier; when the priority segment P value is binary 100, decimal is 6, it represents the second reserved identifier; the smaller the priority, the higher the priority.

[0021] Table 1 S2. The device sending the CAN message determines the value of the Protocol Data Unit Format PF in the CAN extended frame to be generated based on the parameter transmission format in the CAN message to be sent. The Protocol Data Unit Format PF is used to identify the parameter transmission format of the CAN message, which includes single-parameter transmission, multi-parameter transmission, and synchronization signal transmission. In this embodiment, the Protocol Data Unit (PF) format adopts the PDU1 format for messages, and the parameter group number range corresponding to its data field is binary 00000000~11101111, decimal 0~ 239 is used to send data to a specific or global address. The parameter group numbers used are shown in Table 2, which is a protocol data unit number allocation table. As shown in Table 2, when the binary value of the protocol data unit format PF is 00001010 (decimal 10), it indicates multi-parameter transmission, transmitting the target positions of any two drive shafts; when the binary value of the protocol data unit format PF is 00001011 (decimal 11), it indicates multi-parameter transmission, transmitting the target speeds of any two drive shafts; when the binary value of the protocol data unit format PF is 00001100 (decimal 12), it indicates multi-parameter transmission, transmitting the target torques of any two drive shafts; when the binary value of the protocol data unit format PF is 00001101 (decimal 13), it indicates multi-parameter transmission, transmitting the target position and target speed of a single drive shaft. Transmission is performed as follows: When the value of the protocol data unit format PF is 00101001 in binary and 41 in decimal, it is a multi-parameter transmission, transmitting the actual position, status word, and fault code of a single drive shaft; when the value of the protocol data unit format PF is 00101010 in binary and 42 in decimal, it is a multi-parameter transmission, transmitting the actual speed, current, voltage, and temperature of a single drive shaft; when the value of the protocol data unit format PF is 00000001 in binary and 1 in decimal, it is a single-parameter transmission, transmitting a single parameter of a single drive shaft; when the value of the protocol data unit format PF is 01010000 in binary and 80 in decimal, it is a synchronization signal transmission; when the value of the protocol data unit format PF is 01010001~11101111 in binary and 81~239 in decimal, it represents a reserved identifier.

[0022] Table 2 S3. The device sending the CAN message determines the generated CAN extended frame based on the value of the priority segment P and the value of the protocol data unit format PF, and sends it to the device receiving the CAN message. The device receiving the CAN message parses the received CAN extended frame according to the preset parsing rules, determines the processing order of the corresponding CAN message by extracting the value of the priority segment P, and determines the parameter transmission format and transmission content of the corresponding CAN message by extracting the value of the protocol data unit format PF.

[0023] This embodiment uses the CAN2.0B bus to communicate between the motion controller and its connected driver. The specified content is as follows: 1) Normative references SAE J1939.21 Data Link Layer, SAE J1939.31 Network Layer, SAE J1939.31 Vehicle Application Layer, CiA 301 CANopen Application Layer and Communication Profile, CiA402 Device Profile Drives and Motion Control.

[0024] 2) Standardized terminology and definitions 2.1) Frame: A series of data units that make up a complete message.

[0025] 2.2) CAN Data Frame: The ordered bit fields necessary for the CAN protocol to transmit data, starting with Start of Frame (SOF) and ending with End of Frame (EOF).

[0026] 2.3) CAN standard frame: CAN data frame with an 11-bit identifier.

[0027] 2.4) CAN Extended Frame: CAN data frame with a 29-bit identifier.

[0028] like Figure 1 The diagram shows the CAN extended frame structure used in this embodiment. The specific bit allocation conforms to the SAE J1939-21 specification, and the extended data frame consists of 128 bits. A data frame generally comprises the following seven areas: Start of Frame, Arbitration Field, Control Field, Data Field, Check Field, Acknowledgment Field, and End of Frame. The Reserved Bit (R), Data Page Bit (DP), and Protocol Specific Data Unit Bit (PS) in the Arbitration Field together form the Parameter Group Number (PGN), which identifies the parameter number of the data transmitted in this frame.

[0029] 2.5) CAN message: One or more "CAN data frames" with the same parameter group number.

[0030] 2.6) Identifier: The identifier portion of the CAN arbitration field.

[0031] 2.7) Protocol Data Unit (PDU): A specific CAN data frame format.

[0032] 2.8) Parameter Group Number (PGN): A 24-bit value used to uniquely identify a parameter group. The parameter group number includes: reserved bits, data page bits, PDU format field (8 bits), and group extension field (8 bits).

[0033] The Parameter Group Number (PGN) is a 24-bit number. Bits 2-7 of byte 1 are 0, bit 1 corresponds to the reserved bit R of the extended frame, bit 0 corresponds to the data page bit DP of the extended frame, and bytes 2 and 3 correspond to the Protocol Data Unit Format (PF) and Protocol Specific Data Unit (PS) (data destination address DA in this standard), respectively. The PGN format is as follows: Figure 2 As shown in Table 3, the value range can support a total of 480 sets of parameters across the two pages.

[0034] Table 3 2.9) Start of Frame (SOF): Occupies 1 bit space. The start of frame marks the beginning of data frames and remote frames. It is a marker that data frames have started being sent and consists of a "dominant (logic 0)" bit.

[0035] 2.10) Priority segment (P): Occupies 3 bits and is used to set the arbitration priority during transmission. The highest priority is level 0 and the lowest priority is level 7.

[0036] 2.11) Reserved bit (R): Occupies 1 bit space and is a bit reserved by the relevant standard (such as SAE J1939). These reserved bits are usually set to specific values ​​(such as 0 or 1) so that they can be used to implement new functions or features in future extensions or revisions of the protocol.

[0037] The reserved bit structure is: 1 bit, recessive level, logic 1.

[0038] 2.12) Data Page Bit (DP): Occupies 1 bit space and serves as an auxiliary page for the selection parameter group description. All parameter group numbers should fill the zeroth page before the first page is assigned.

[0039] The data page bit (DP) structure is as follows: 1 bit, which is 0 when it represents the first page parameter group and 1 when it represents the second page parameter group.

[0040] 2.13) Protocol Data Unit Format (PF): Occupies 8 bits and is one of the fields that determines the Parameter Group Number (PGN) corresponding to the data field. The Parameter Group Number is used to identify or identify commands, data, requests, acknowledgments, and denials.

[0041] 2.14) Protocol Specific Data Unit (PS): Occupies 8 bits. The content of the PS field is determined according to the PDU format (PF). When the PF value is 0~239, the PDU format is PDU1, and PS represents the destination address (DA), i.e., the destination address to which the message is to be sent. When the PF value is 240~255, the PDU format is PDU2, and PS represents group extension (GE). The lowest four significant bits of PS and PF together determine 4096 PDU2 format parameter groups.

[0042] 2.15) Source Address (SA): Occupies 8 bits and is used to identify the address of the node or device that sent the message.

[0043] The source address (SA) is the source address of the device that sent this message. The source address field ranges from 0 to 255, where 0x00 represents the master device address (i.e., the controller), 0x02 to 0xFF represents the slave device address (i.e., the driver), and the address value 0x01 is not used. The source address definition is shown in Table 4.

[0044] Table 4 2.16) Substitute Remote Request Bit (SRR): Occupies 1 bit. In the extended frame format, the SRR bit is recessive. Its main function is to ensure that the standard data frame has a higher priority than the extended data frame.

[0045] 2.17) Identifier Extension Bit (IDE): Occupies 1 bit space and is used to identify whether the data frame is a standard frame or an extended frame. When the IDE bit is dominant (0), it indicates that the data frame is a standard frame and its identifier (ID) length is 11 bits; when the IDE bit is recessive (1), it indicates that the data frame is an extended frame and its ID length is 29 bits.

[0046] 2.18) Remote Transmission Request (RTR) bit: Occupies 1 bit space. The RTR bit is used to distinguish between data frames and remote frames. When the RTR bit is dominant (logic 0), it indicates that the frame is a data frame, that is, the frame contains actual data content; while when the RTR bit is recessive (logic 1), it indicates that the frame is a remote frame, used to request other nodes to send data.

[0047] 2.19) Data Length Code (DLC): Occupies 4 bits and is used to indicate the length of a data field in a data frame or remote frame.

[0048] The Data Length Code (DLC) occupies 4 bits and has a value range of 0 to 8, representing the length of the data field. The definition of DLC is shown in Table 5.

[0049] Table 5 2.20) Data Field: The part used to transmit the actual data content. It is located in the data frame, immediately following the arbitration field and control field. The length of the data field can be set from 0 to 8 bytes as needed, with each byte containing 8 bits. When sending data, the data in the send buffer is sent according to the length indicated by the length code; when receiving data, the receiving node also parses and receives data of the corresponding length according to the length code.

[0050] The data domain structure includes the Service Data Object (SDO) data domain structure. The SDO data structure is divided into two forms: read / write operation and read / write feedback. The read / write data structure is shown in Table 6, and the feedback data structure is shown in Table 7.

[0051] Table 6 Table 7 The data field structure also includes the process data object (PDO) data field structure. PDO data is used for real-time one-way transmission. Its structure depends on the combination of transmission parameters. Unused bits or bytes are filled with binary 0s. Its data structure is shown in Table 8.

[0052] Table 8 2.21) Cyclic Redundancy Check (CRC): Occupying 16 bits, it is a check algorithm used to detect errors in data transmission. It is appended to the end of the data frame and calculated and compared at the receiving end to determine whether the data has been transmitted correctly.

[0053] 2.22) Acknowledgment bit (ACK): Occupies 2 bits and is a mechanism used to confirm whether a frame has been received normally. When the receiving unit receives the frame correctly, it sends a dominant bit in the ACK segment (usually during the acknowledgment interval) to indicate normal reception. This dominant bit will cover the recessive bit output by the sending node, thus appearing dominant on the bus. By monitoring this bit on the bus, the sending node can confirm whether the data frame or remote frame it sent has been received correctly.

[0054] 2.23) End of Frame (EOF) bit: Occupies 7 bits and is used to indicate the end of a data frame, informing the receiving device that the data frame has been transmitted and that the receiving device can begin processing the data. It consists of 7 bits, all of which are recessive. If any of these 7 bits are dominant, it will cause a stuffing error.

[0055] 2.24) Data Target Address (DA): Occupies 8 bits and is used to identify the target node number to which the data frame should be sent.

[0056] The Data Destination Address (DA) defines the node address of the data frame receiver. If the local address of a device on the bus is the same as the destination address of the received message, the message is received and processed. In this standard, the destination address bit of the controller (master device) is defined as 0x00, and the destination address of the driver (slave device) is 0x02~0xFF. If broadcast communication is used, the destination address value is set to 0x01, as shown in Table 9, the Data Destination Address Definition Table.

[0057] Table 9 2.25) Object Dictionary (OD): A dictionary containing all function blocks, resource blocks, and conversion block parameters of a device, through which the fieldbus network can access the blocks.

[0058] 2.26) Process Data Object (PDO): a one-way transmission type that does not require the receiving node to respond with a CAN message for confirmation, belonging to the "production-consumption" model.

[0059] 2.27) Service Data Object (SDO): It has a specified address of the receiving node and requires the specified receiving node to respond to the CAN message to confirm that it has been received. If no confirmation is received within the timeout period, the sending node will resend the original message. It belongs to the "server client" communication model.

[0060] The remaining components, such as Start of Frame (SOF), End of Frame (EOF), Cyclic Redundancy Check (CRC), and Acknowledgment (ACK), adopt fixed values ​​or calculation methods, and their structures are shown in Table 10.

[0061] Table 10 General requirements 3.1) General Rules 3.1.1) Message format: The CAN protocol should use a 29-bit identifier extended frame format message.

[0062] 3.1.2) Baud rate: The communication baud rate should preferably be 250kbit / s or 500kbit / s. The selection of baud rate is limited by the bus length. The relationship between baud rate and bus length is shown in Table 11.

[0063] Table 11 3.1.3) Interface Model: The signal lines adopt a two-wire serial bus structure. The typical transmission method is that there is one master device, i.e., the controller, and multiple slave devices, i.e., the drivers, on the bus. Each device has a unique address, and the devices communicate with each other through standardized messages, achieving uniformity in the application layer structure.

[0064] 3.1.4) CAN Communication Model: This model consists of three parts: communication interface, data transmission, and data processing. Figure 3 As shown, the communication interface is responsible for data exchange between the device and the CAN bus. Data transmission takes three forms: single-parameter transmission, multi-parameter transmission, and synchronous signal transmission. Single-parameter transmission is accomplished by reading and writing a single object, multi-parameter transmission is accomplished by sending a custom parameter group, and synchronous signal transmission uses a specific extended frame ID. The CAN bus communication interface determines the actual transmission method of the CAN signal through its physical layer, and uses a filter to accept the message identifier to decide whether to accept the message. Subsequently, received messages are classified into urgent messages, non-urgent messages, and synchronous messages through their own structure fields. The CAN bus sends and receives messages through the communication interface, and transmits the information to be expressed to the controller and other devices for data processing. The data processing method is determined by the device itself, and this standard does not provide a specific definition.

Claims

1. A communication method for a multi-axis linkage equipment control system based on the CAN protocol, characterized in that, Includes the following steps: S1. The device sending CAN messages determines the value of the priority segment P in the CAN extended frame to be generated based on the priority of the CAN messages to be sent. The priority segment P is used to identify the priority of the CAN messages. The CAN messages are divided into urgent CAN messages, non-urgent CAN messages, and synchronous CAN messages according to their priority from high to low. The non-urgent CAN messages are divided into periodic non-urgent CAN messages and non-periodic non-urgent CAN messages according to their priority from high to low. The device sending CAN messages is a transmitting device within a multi-axis linkage equipment control system. S2. The device sending the CAN message determines the value of the Protocol Data Unit Format PF in the CAN extended frame to be generated based on the parameter transmission format of the CAN message to be sent; the Protocol Data Unit Format PF is used to identify the parameter transmission format of the CAN message, and the parameter transmission format includes multi-parameter transmission. S3. The device sending the CAN message determines the generated CAN extended frame based on the value of the priority segment P and the value of the protocol data unit format PF, and sends it to the device receiving the CAN message to complete the communication of the multi-axis linkage device control system based on the CAN protocol; the device receiving the CAN message is the receiving device in the multi-axis linkage device control system.

2. The communication method for a multi-axis linkage equipment control system based on the CAN protocol according to claim 1, characterized in that: In step S1, the device that sends the CAN message includes a master device and a slave device; The device that sends the emergency CAN message is the master device, and the value of the corresponding priority segment P is 000, with a priority of 0. The device that sends the non-periodic, non-urgent CAN message is the master device, with a priority segment P value of 010 and a priority of 2; or, the device that sends the non-periodic, non-urgent CAN message is the slave device, with a priority segment P value of 011 and a priority of 3. The device that sends the periodic non-urgent CAN message is the master device, with a priority segment P value of 100 and a priority of 4; or, the device that sends the periodic non-urgent CAN message is the slave device, with a priority segment P value of 101 and a priority of 5. The device that sends the synchronous CAN message is the master device, and the value of the corresponding priority segment P is 111, with a priority of 7. The lower the priority, the higher the priority.

3. The communication method for a multi-axis linkage equipment control system based on the CAN protocol according to claim 2, characterized in that: In step S2, the parameter transmission format is multi-parameter transmission; When the transmission parameters are the target positions of any two drive shafts, the value of the protocol data unit format PF is 00001010; When the transmission parameters are the target rotational speeds of any two drive shafts, the value of the protocol data unit format PF is 00001011; When the transmission parameters are the target torques of any two drive shafts, the value of the protocol data unit format PF is 00001100; When the transmission parameters are the target position and target speed of a single drive shaft, the value of the protocol data unit format PF is 00001101; When the transmission parameters are the actual position, status word, and fault code of a single drive shaft, the value of the protocol data unit format PF is 00101001; When the transmission parameters are the actual speed, current, voltage, and temperature of a single drive shaft, the value of the protocol data unit format PF is 00101010.

4. The communication method for a multi-axis linkage equipment control system based on the CAN protocol according to claim 3, characterized in that: In step S2, the parameter transmission method also includes single-parameter transmission and synchronization signal transmission; When the parameter transmission form is single-parameter transmission, the transmitted parameter is a single parameter of a single drive shaft, and the value of the protocol data unit format PF is 00000001; When the parameter transmission form is synchronous signal transmission, the value of the protocol data unit format PF is 01010000.

5. The communication method for a multi-axis linkage equipment control system based on the CAN protocol according to claim 2, characterized in that: In step S1, the priority segment P also has reserved values ​​of 001 and 100, which represent the first reserved identifier and the second reserved identifier, respectively.

6. The communication method for a multi-axis linkage equipment control system based on the CAN protocol according to claim 3, characterized in that: In step S2, the value of the protocol data unit format PF is also reserved for values ​​from 01010001 to 11101111, which represent the reserved identifiers from 01010001 to 11101111 respectively.

7. The communication method for a multi-axis linkage equipment control system based on the CAN protocol according to claim 3, characterized in that: In step S3, the device receiving the CAN message parses the received CAN extended frame according to the preset parsing rules, determines the priority processing order of the corresponding CAN message by extracting the value of the priority segment P, and determines the parameter transmission format of the corresponding CAN message by extracting the value of the protocol data unit format PF.

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