Plc signal wireless transparent transmission method, device and equipment of industrial internet of things and medium

Abstract

The application relates to a PLC signal wireless transparent transmission method and device of an industrial Internet of Things, equipment and a medium, and relates to the technical field of industrial automation control and communication. In a sending end, a Modbus RTU signal of a PLC system is encapsulated into a TCP / IP data packet through a protocol conversion module, and is accessed into an industrial intranet for wireless transmission by a CPE device supporting multi-mode access. In a receiving end, the data packet is unpacked and signal reconstruction is performed through a reverse protocol conversion module, and is restored into a Modbus RTU frame and is output to a target PLC system. The application has high reliability, low delay and strong anti-interference capability, and effectively solves the problems of high cost, long period and easy electromagnetic interference of traditional wired wiring.

Description

Technical Field

[0001] This invention relates to the field of industrial automation control and communication technology, and in particular to a method, apparatus, equipment and medium for wireless transmission of PLC signals in the Industrial Internet of Things. Background Technology

[0002] With the increasing level of industrial automation, large factories often need to deploy multiple physically distributed programmable logic controller (PLC) systems to control complex production processes. These distributed PLC systems need to exchange control commands and synchronize status data in real time to ensure the coordinated and stable operation of the entire production line.

[0003] Currently, the main method for interconnecting signals between distributed PLC systems is to directly lay dedicated shielded cables. This method uses high-specification RS485 shielded twisted-pair cables as the physical transmission medium. Through complex civil engineering work such as trenching, pipe laying, and cable tray installation, the communication interfaces of each PLC station are physically connected one-to-one via cables, thereby enabling point-to-point or multi-point communication based on serial communication protocols such as Modbus RTU.

[0004] However, with the continuous expansion of factory scale and the increasing demand for flexible production line deployment, large-scale cable laying in large-area, long-distance industrial sites not only leads to high engineering material and labor costs, but also significantly prolongs project construction cycles due to complex construction processes. Furthermore, cables stretching for kilometers in industrial environments filled with strong electromagnetic interference sources such as frequency converters and large motors can easily become highly efficient antennas, causing signal distortion or loss, making it difficult to guarantee communication stability. When subsequent equipment relocation or production line upgrades are needed, the cumbersome rewiring work also greatly limits the system's flexibility and scalability. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method, device, equipment and medium for wireless transmission of PLC signals in the Industrial Internet of Things, aiming to solve at least one of the above-mentioned technical problems.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: Firstly, this application provides a method for wireless transparent transmission of PLC signals in the Industrial Internet of Things (IIoT), applied at the transmitting end, and adopting the following technical solution: A method for wireless transmission of PLC signals in an industrial Internet of Things (IIoT) is applied at the transmitting end, wherein the transmitting end communicates with the receiving end through an industrial intranet, and the method includes: Obtain the serial communication frame output by the source PLC system and input the serial communication frame to the protocol conversion module; The protocol conversion module parses the serial communication frame and encapsulates the parsed serial communication frame into a TCP / IP data packet based on a preset encapsulation rule; The TCP / IP data packets are input to the sending client terminal device, which monitors the monitoring information of each available wireless link in real time. The monitoring information includes signal strength, signal-to-noise ratio and network latency. Based on the monitoring information of each available wireless link, the primary link is determined. Priority identifiers are set for the TCP / IP data packets, and based on the priority queue scheduling strategy and the primary link, the TCP / IP data packets are transmitted to the receiving end in the industrial intranet via a wireless channel. The receiving end then decapsulates the TCP / IP data packets, strips the headers of each layer, and reconstructs them into Modbus RTU data frames based on pre-configured protocol mapping rules. These frames are then converted into serial communication signals and output to the target PLC system.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the protocol conversion module parses the serial communication frame and encapsulates the parsed serial communication frame into a TCP / IP data packet based on preset encapsulation rules, including: The protocol conversion module extracts the Modbus RTU message from the serial communication frame. The Modbus RTU message includes the device address, function code, and data field. The CRC checksum of the Modbus RTU message is stripped, and a Modbus application protocol header is added to the header of the device address, function code, and data fields to form Modbus TCP application layer data. The Modbus application protocol header includes a transaction identifier, a protocol identifier, a length, and a unit identifier. The Modbus TCP application layer data is embedded as a payload into the data segment of the TCP packet. A TCP header, an IP header, and an Ethernet frame header are added sequentially outside the data segment of the TCP packet to obtain the TCP / IP data packet.

[0009] Furthermore, determining the primary link based on monitoring information from each available wireless link includes: The wireless link with the lowest network latency and a signal strength higher than a preset strength threshold is identified as the primary link.

[0010] Furthermore, the transmission of TCP / IP data packets to the receiving end in the industrial intranet via a wireless channel based on the priority queue scheduling strategy and the primary link includes: Set the Differential Service Code Point (DSCP) flag in the IP header of the TCP / IP data packet; Mark data packets containing PLC control signals as having the highest priority; Configure a priority queue scheduling algorithm in the sending end client terminal equipment and industrial intranet switch; The sending client terminal device transmits TCP / IP data packets marked with the highest priority to the receiving end in the industrial intranet via a wireless channel based on the primary link.

[0011] Furthermore, the sending client terminal device is a client device with dual SIM card redundant network access, and the method further includes: The sending end client terminal equipment periodically sends probe messages to the target node to monitor the signal receiving power and signal-to-noise ratio of the primary link in real time; If no probe response message is received for a set number of consecutive times, or if the signal quality of the primary link is lower than a preset threshold for a duration exceeding a set time, the primary link is determined to be faulty and the route is switched to the network link corresponding to the backup SIM card.

[0012] Secondly, this application provides a method for wireless transmission of PLC signals in the Industrial Internet of Things (IIoT), applied at the receiving end, and adopts the following technical solution: A method for wireless transparent transmission of PLC signals in an industrial Internet of Things (IoT) includes: The receiving end client terminal equipment receives TCP / IP data packets transmitted from the sending end from the industrial intranet. The TCP / IP data packets are formed by the protocol conversion module of the sending end by encapsulating the serial communication frames output by the source PLC system according to the preset encapsulation rules. The TCP / IP data packets are forwarded to the reverse protocol conversion module; The reverse protocol conversion module decapsulates the TCP / IP data packets, stripping away the TCP / IP header information layer by layer, and reconstructs them into Modbus RTU data frames based on pre-configured protocol mapping rules. The Modbus RTU data frame is converted into a serial communication signal and output to the target PLC system, so that the target PLC system can execute the corresponding control logic based on the Modbus RTU data frame.

[0013] Furthermore, the reverse protocol conversion module strips the TCP / IP header information from the TCP / IP data packets layer by layer, and reconstructs them into Modbus RTU data frames based on pre-configured protocol mapping rules, including: The reverse protocol conversion module sequentially strips the Ethernet frame header, IP header, TCP header, and Modbus application protocol header of the TCP / IP data packet, and extracts the unit identifier, function code, and data field from the payload; Based on the pre-configured Modbus TCP to Modbus RTU mapping table, the unit identifier is used as the RTU device address. Combined with the function code and data field, the CRC checksum is recalculated and reconstructed into a standard Modbus RTU data frame.

[0014] Furthermore, the reverse protocol conversion module also performs multiple data integrity checks during the signal restoration process, including: During the protocol decapsulation phase, cyclic redundancy check is performed on TCP / IP packets to verify whether bit errors have occurred during the transmission of TCP / IP packets; After Modbus RTU data frame reconstruction, CRC check is performed on the restored serial data frame; If a valid data packet is not successfully received or the verification fails within the preset timeout window, a retransmission request is initiated to the sender, and the number of retransmissions is no less than the set number. When consecutive retransmissions fail or the number of verification errors reaches a preset threshold, a local alarm signal is triggered.

[0015] Furthermore, the reverse protocol conversion module incorporates built-in security logic, and the method further includes: If no valid data packet is received within the preset timeout period or if the verification fails continuously, the reverse protocol conversion module outputs a predefined security value to the target PLC system. When a temporary network outage occurs, the reverse protocol conversion module outputs the last valid and correctly verified signal value in the cache until the network is restored or the timeout period is reached.

[0016] Thirdly, this application provides a wireless transparent transmission system for PLC signals in the Industrial Internet of Things, which adopts the following technical solution: A PLC signal wireless transmission system for industrial Internet of Things includes a transmitter and a receiver; The sending end includes: The protocol conversion module is connected to the communication port of the source PLC system. It is used to obtain the serial communication frames output by the source PLC system, parse the serial communication frames, and encapsulate the parsed serial communication frames into TCP / IP data packets based on preset encapsulation rules. The transmitting client terminal device is connected to the protocol conversion module and is used to monitor the monitoring information of each available wireless link in real time. The monitoring information includes signal quality parameters and network latency. Based on the monitoring information of each available wireless link, the primary link is determined. Priority identifiers are set for the TCP / IP data packets, and based on the priority queue scheduling strategy and the primary link, the TCP / IP data packets are transmitted to the industrial intranet through the wireless channel. The receiving end includes: The receiving client terminal device is used to receive the TCP / IP data packets from the industrial intranet and send them to the reverse protocol conversion module; The reverse protocol conversion module is connected to the receiving end client terminal device and is used to decapsulate TCP / IP data packets, strip the TCP / IP header information layer by layer, and reconstruct them into Modbus RTU data frames based on pre-configured protocol mapping rules. The Modbus RTU data frames are then converted into serial communication signals and output to the target PLC system.

[0017] In summary, the beneficial effects of this application are: At the sending end, the serial communication frames output by the source PLC system are parsed and encapsulated into standard TCP / IP data packets through the protocol conversion module. Then, the client terminal equipment selects the optimal wireless link to access the industrial intranet for transmission based on real-time monitoring of signal strength, signal-to-noise ratio, and network latency. At the receiving end, the TCP / IP packet header is stripped layer by layer through the reverse protocol conversion module and the Modbus RTU data frame is accurately reconstructed based on the protocol mapping rules and output to the target PLC system. This eliminates the need for large-scale physical cable laying between distributed PLC systems, reduces engineering costs such as cable materials, pipeline laying, and construction labor, and significantly shortens the project implementation cycle. Meanwhile, by setting flag bits in the IP header and configuring a strict priority queue scheduling algorithm to ensure the real-time transmission of control signals, by using dual SIM card redundant network access and automatic link switching mechanisms to ensure communication continuity, by using multiple data integrity checks and timeout retransmission mechanisms to ensure high reliability of signal transmission, and by using the security logic built into the reverse protocol conversion module to output predefined security values ​​to prevent equipment malfunction when communication is interrupted, the entire solution meets the stringent requirements of industrial environments for end-to-end latency, jitter, and signal integrity, while achieving black-box transparent transmission to both PLC systems without modifying the original PLC program or communication configuration. The system also has good flexibility and scalability, and no rewiring is required when equipment is relocated or production line is upgraded. It can be widely used in remote monitoring and collaborative control of distributed PLC systems in scenarios such as thermal power plants, water plants, petrochemical plants, and discrete manufacturing plants. Attached Figure Description

[0018] Figure 1A flowchart illustrating a method for wireless transmission of PLC signals in an industrial Internet of Things (IoT) application at the transmitting end, provided as an embodiment of the present invention; Figure 2 This is a flowchart illustrating a method for wireless transmission of PLC signals in an industrial Internet of Things (IoT) application at the receiving end, as provided in one embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0021] Example 1 like Figure 1 As shown in the figure, this application provides a method for wireless transparent transmission of PLC signals in an industrial Internet of Things (IoT) application. The method is applied at the transmitting end, which communicates with the receiving end via an industrial intranet. The method includes: S101, Obtain the serial communication frame output by the source PLC system, and input the serial communication frame to the protocol conversion module; S102, the protocol conversion module parses the serial communication frame and encapsulates the parsed serial communication frame into a TCP / IP data packet based on a preset encapsulation rule; S103, the TCP / IP data packet is input to the sending client terminal device, the sending client terminal device monitors the monitoring information of each available wireless link in real time, the monitoring information includes signal strength, signal-to-noise ratio and network latency, and the primary link is determined based on the monitoring information of each available wireless link; S104, set a priority identifier for the TCP / IP data packet, and based on the priority queue scheduling strategy and the primary link, transmit the TCP / IP data packet to the receiving end in the industrial intranet through a wireless channel, so that the receiving end can decapsulate the TCP / IP data packet, strip the headers of each layer, and reconstruct it into a Modbus RTU data frame based on the pre-configured protocol mapping rules, and convert it into a serial communication signal for output to the target PLC system.

[0022] In this context, the source PLC system refers to the programmable logic controller system that acts as the signal sender, outputting serial communication frames based on the RS485 physical layer. These serial communication frames carry control signals in Modbus RTU protocol format. A serial communication frame is a data frame output by the source PLC system through its RS485 communication port according to the Modbus RTU protocol specification, containing the device address, function code, data field, and CRC checksum.

[0023] A protocol conversion module refers to an RS485-RJ45 protocol conversion device with electrical isolation, used to achieve bidirectional transparent conversion between Modbus RTU (serial) and Modbus TCP / IP (Ethernet) protocols. A customer premises equipment (CPE) is an industrial-grade intelligent gateway device that supports multi-mode wireless access, at least supporting 4G LTE, 5G NR, and IEEE 802.11 a / b / g / n / ac / ax (WiFi 6) wireless access technologies.

[0024] In this embodiment, in an industrial setting, when the source PLC system needs to send control commands or status data to a remote target PLC system, the transmitting end initiates a wireless signal transmission process. The source PLC system continuously outputs serial communication frames through its RS485 communication port, according to a preset baud rate and Modbus RTU protocol specification. These serial communication frames are connected to the RS485 A / B terminals of the protocol conversion module via shielded twisted-pair cables, completing the physical signal access. The protocol conversion module employs an industrial-grade isolation design, featuring 2500V DC optocoupler isolation, signal conditioning, surge protection, and electromagnetic interference immunity, ensuring reliable signal access in harsh industrial environments.

[0025] After receiving the serial communication frame, the protocol conversion module parses and processes it.

[0026] Specifically, the protocol conversion module parses the serial communication frame and encapsulates the parsed serial communication frame into a TCP / IP data packet based on preset encapsulation rules, including: The protocol conversion module extracts the Modbus RTU message from the serial communication frame. The Modbus RTU message includes the device address, function code, and data field. The CRC checksum of the Modbus RTU message is stripped, and a Modbus application protocol header is added to the header of the device address, function code, and data fields to form Modbus TCP application layer data. The Modbus application protocol header includes a transaction identifier, a protocol identifier, a length, and a unit identifier. The Modbus TCP application layer data is embedded as a payload into the data segment of the TCP packet. A TCP header, an IP header, and an Ethernet frame header are added sequentially outside the data segment of the TCP packet to obtain the TCP / IP data packet.

[0027] The transaction identifier is used to identify the request / response pairing, the protocol identifier is fixed at 0x0000 to indicate the Modbus protocol, the length field indicates the number of subsequent bytes, and the unit identifier corresponds to the device address in the original RTU frame.

[0028] The encapsulated TCP / IP data packets are output to the sending client terminal device via the RJ45 Ethernet interface. The sending client terminal device monitors the signal strength, signal-to-noise ratio, and network latency of all available wireless links in real time, and determines the wireless link with the lowest network latency and a signal strength higher than a preset strength threshold as the primary link.

[0029] Subsequently, the sending client terminal device sets the DSCP flag in the IP header of the TCP / IP data packet, marking the data packet containing PLC control signals as the highest priority (EF class, i.e., accelerated forwarding class), and transmits the TCP / IP data packet to the receiving end in the industrial intranet via the wireless channel through the primary link based on the internally configured strict priority queue scheduling algorithm.

[0030] After receiving the data, the receiving end performs a reverse operation, decapsulating the TCP / IP data packet layer by layer, stripping the Ethernet frame header, IP header, TCP header, and MBAP header, extracting the payload, and using the pre-configured Modbus TCP to Modbus RTU mapping table as the RTU device address. Combining the function code and data field, the CRC checksum is recalculated, and the data is reconstructed into a standard Modbus RTU data frame. This frame is then converted into a differential level signal by an RS485 transceiver chip and output to the target PLC system, where the target PLC parses and executes the corresponding control logic.

[0031] Furthermore, the sending client terminal device is a client device with dual-SIM card redundant network access, and the method also includes a network link redundancy guarantee step. The sending client terminal device periodically sends probe messages to the target node through a built-in Network Quality Analysis (NQA) or Bidirectional Forwarding Detection (BFD) protocol to monitor the received signal power (RSRP) and signal-to-noise ratio (SINR) of the primary link in real time. When no probe response message is received for a set number of consecutive times (3 times in this embodiment), or when the signal quality of the primary link is lower than a preset threshold for a set duration (e.g., more than 2 seconds), the primary link is determined to be faulty, and routing re-convergence is immediately triggered. Within 50ms, the service data stream is seamlessly switched to the network link corresponding to the backup SIM card, maintaining the underlying TCP connection and ensuring communication continuity. The dual SIM cards can access different operators' mobile networks (4G / 5G) respectively, achieving operator-level network redundancy.

[0032] Furthermore, in addition to the payload of the original RS485 signal, the application layer data domain of the TCP / IP data packet also embeds specific metadata identifiers. These metadata identifiers include: a unique device ID, used to accurately identify the signal source device at the receiving end, avoiding data confusion from multiple sources; a high-precision timestamp, recording the absolute or relative time when the signal was encapsulated, used by the receiving end for signal synchronization, timing analysis, and fault diagnosis; and a sequence number, used to detect packet loss and out-of-order delivery, and supporting reordering processing at the receiving end. Through this metadata identifier mechanism, lossless representation and precise cross-domain alignment of source PLC signals can be achieved in a distributed network environment.

[0033] Furthermore, the transmitting client terminal device has a built-in hardware watchdog timer to monitor the system's operating status and prevent crashes. Its working mechanism is as follows: the system main program periodically sends a reset signal (feeding the watchdog) to the hardware watchdog within a set time period. If the system freezes due to software malfunction or strong electromagnetic interference and fails to send the reset signal within the set period, the hardware watchdog will forcibly trigger a system-level reset and restart, thereby ensuring the device's continuous operation in unattended industrial environments.

[0034] Furthermore, an IPSec VPN tunnel or SSL / TLS encrypted channel is established between the sending client terminal equipment and the core equipment of the industrial intranet to perform end-to-end encryption on all transmitted PLC data, preventing data eavesdropping and tampering. In IPSec VPN mode, the IKEv2 protocol is used for two-way authentication and dynamic key negotiation, and the AES-256-GCM symmetric encryption algorithm is used during data transmission to ensure data confidentiality and integrity. In SSL / TLS mode, the TLS 1.3 protocol is used, and ECDHE (Elliptic Curve Diffie-Hellman Key Exchange) is used for forward-secure key exchange, and the AES-256-GCM algorithm is also used for high-strength encryption of the payload. At the same time, a strict whitelist policy based on IP / MAC addresses is implemented at the industrial intranet boundary firewall, allowing only authorized CPE device MAC addresses and predefined IP addresses to communicate.

[0035] Furthermore, the protocol conversion module supports a custom register mapping table, allowing specific registers of the source PLC (such as D100) to be directly mapped to specific TCP ports (such as 5001) and Modbus TCP register addresses of the target network, providing great configuration flexibility. The module supports flexible configuration of communication parameters, including baud rate (covering 9.6kbps to 115.2kbps), data bits, stop bits, and parity, to adapt to the communication parameter requirements of different PLC systems.

[0036] Example 2 like Figure 2 As shown, this embodiment provides a method for wireless transparent transmission of PLC signals in an industrial Internet of Things (IoT) system, applied at a receiving end. The receiving end communicates with the transmitting end through an industrial intranet. The method includes: S201, The receiving end client terminal device receives TCP / IP data packets transmitted from the sending end from the industrial intranet. The TCP / IP data packets are formed by the protocol conversion module of the sending end by encapsulating the serial communication frames output by the source PLC system according to the preset encapsulation rules. S202, forward the TCP / IP data packet to the reverse protocol conversion module; S203, the reverse protocol conversion module decapsulates the TCP / IP data packet, strips off the TCP / IP header information layer by layer, and reconstructs it into a Modbus RTU data frame based on the pre-configured protocol mapping rules; S204, the Modbus RTU data frame is converted into a serial communication signal and output to the target PLC system so that the target PLC system executes the corresponding control logic based on the Modbus RTU data frame.

[0037] The receiving end client terminal equipment refers to an industrial-grade multi-mode intelligent gateway device deployed on the signal receiving side. It adopts a symmetrical architecture with the sending end client terminal equipment and is used to continuously monitor the industrial intranet and capture specific TCP / IP data packets originating from the sending end. The reverse protocol conversion module refers to an industrial-grade device with RJ45-RS485 protocol conversion capabilities. It performs the opposite operation to the sending end protocol conversion module, that is, restoring TCP / IP data packets to RS485 serial communication signals.

[0038] In this embodiment, at the receiving end, the receiving client terminal device continuously listens to the industrial intranet. Upon capturing TCP / IP data packets from the sending end, it forwards the packets to the physically connected reverse protocol conversion module via the RJ45 Ethernet interface. After receiving the TCP / IP data packets, the reverse protocol conversion module performs a reverse protocol decapsulation operation.

[0039] Specifically, the reverse protocol conversion module strips the TCP / IP header information from the TCP / IP data packets layer by layer, and reconstructs them into Modbus RTU data frames based on pre-configured protocol mapping rules, including: The reverse protocol conversion module sequentially strips the Ethernet frame header, IP header, TCP header, and Modbus application protocol header of the TCP / IP data packet, and extracts the unit identifier, function code, and data field from the payload; Based on the pre-configured Modbus TCP to Modbus RTU mapping table, the unit identifier is used as the RTU device address. Combined with the function code and data field, the 16-bit CRC checksum is recalculated and reconstructed into a standard Modbus RTU data frame.

[0040] Finally, the reverse protocol conversion module uses its internal RS485 transceiver chip (such as MAX485) to convert the reconstructed Modbus RTU data frames into differential level signals conforming to RS485 electrical characteristics. The output RS485 signal is connected to the RS485 communication port (A / B terminal) of the target PLC system via a shielded twisted pair cable. The target PLC's communication module receives and parses the serial signal in real time according to the preset baud rate and station address, and then updates the internal register state to execute corresponding physical control actions, such as starting and stopping motors, switching valves, and adjusting frequency converter speed.

[0041] For the PLC systems at both ends, the entire wireless transmission process is as if they are directly connected through a virtual, infinitely long RS485 cable, achieving "black box" transmission without the need to modify the original PLC program or communication configuration.

[0042] Furthermore, the reverse protocol conversion module performs multiple data integrity checks during signal restoration to ensure high reliability of signal transmission. Specifically, this includes: during the protocol decapsulation phase, performing Cyclic Redundancy Check (CRC) or Frame Check Sequence (FCS) checks on the received TCP / IP data packets to verify whether bit errors occurred during wireless transmission; after Modbus RTU data frame reconstruction, performing the 16-bit CRC check specified by the Modbus RTU protocol again on the restored serial data frame to ensure data integrity of the reconstructed frame; if a valid data packet is not successfully received or the check fails within a preset timeout window (e.g., 300ms), a retransmission request is actively initiated to the sender, with the number of retransmissions not less than a set number (default not less than 3, adjustable via the configuration interface); when consecutive retransmission failures or check errors reach a preset threshold, a local alarm signal is triggered, with alarm methods including but not limited to dry contact output, SNMP Trap messages, or Syslog messages, notifying maintenance personnel to intervene promptly.

[0043] Furthermore, the reverse protocol conversion module incorporates safety logic to ensure the safe operation of the controlled device in the event of communication abnormalities. When the reverse protocol conversion module fails to receive any valid data packets or experiences consecutive verification failures within a preset timeout period (e.g., 300ms), it automatically outputs a predefined safety value (Fail-SafeValue) to the target PLC system. This safety value is typically set to a value that puts the controlled device into a safe state, such as a stop command, a stay-in-place command, or an output of zero, to prevent the controlled device from becoming uncontrollable or causing a safety accident due to communication interruption. Simultaneously, in the event of a temporary network interruption (before the interruption timeout period has elapsed), the reverse protocol conversion module continuously outputs its buffered last valid and correctly verified signal value, preventing the controlled device from malfunctioning or experiencing unplanned shutdowns due to momentary communication interruptions, thus providing buffer time for network recovery. Once normal network communication is restored, the reverse protocol conversion module automatically switches back to real-time data output mode.

[0044] Furthermore, the receiving client terminal device is also an industrial-grade client device with dual SIM card redundant network access, possessing the same automatic network selection and seamless switching capabilities as the sending client terminal device. The receiving client terminal device has a built-in hardware watchdog timer, employing the same periodic watchdog feeding mechanism as the sending end to monitor the system's operating status. When the system's main program abnormally freezes, the hardware watchdog forcibly triggers a system reset and restart, ensuring the continuous availability of the receiving device in unattended environments.

[0045] Furthermore, an IPSec VPN tunnel or SSL / TLS encrypted channel is also established between the receiving client terminal device and the industrial intranet to ensure the confidentiality, integrity, and source reliability of the received PLC control data. When receiving data packets, the receiving client terminal device first decrypts and authenticates the encrypted channel. Only legitimate data packets that pass authentication are forwarded to the reverse protocol conversion module for further processing, thereby effectively preventing malicious data injection attacks.

[0046] Example 3 This embodiment provides a PLC signal wireless transmission system for industrial Internet of Things, including a transmitter and a receiver.

[0047] The sending end includes: The protocol conversion module is connected to the communication port of the source PLC system. It is used to obtain the serial communication frames output by the source PLC system, parse the serial communication frames, and encapsulate the parsed serial communication frames into TCP / IP data packets based on preset encapsulation rules. The transmitting client terminal device is connected to the protocol conversion module and is used to monitor the monitoring information of each available wireless link in real time. The monitoring information includes signal quality parameters and network latency. Based on the monitoring information of each available wireless link, the primary link is determined. Priority identifiers are set for the TCP / IP data packets, and based on the priority queue scheduling strategy and the primary link, the TCP / IP data packets are transmitted to the industrial intranet through the wireless channel. The receiving end includes: The receiving client terminal device is used to receive the TCP / IP data packets from the industrial intranet and send them to the reverse protocol conversion module; The reverse protocol conversion module is connected to the receiving end client terminal device and is used to decapsulate TCP / IP data packets, strip the TCP / IP header information layer by layer, and reconstruct them into Modbus RTU data frames based on pre-configured protocol mapping rules. The Modbus RTU data frames are then converted into serial communication signals and output to the target PLC system.

[0048] The PLC signal wireless transmission system provided in this embodiment can be widely used for remote monitoring and collaborative control of distributed PLC systems in scenarios such as thermal power plants, water plants, petrochemical plants, and discrete manufacturing plants. By adopting a "wireless virtual channel" architecture instead of physical cables, the system reduces the manpower, material, and time costs of project implementation. Simultaneously, through multi-layered reliability assurance mechanisms and security protection measures, it ensures high real-time performance, high integrity, and high availability of control signals transmitted in the wireless channel, meeting the communication requirements of harsh industrial environments. The system's wireless deployment characteristics make subsequent equipment expansion, production line modification, and equipment migration extremely convenient, exhibiting excellent scalability and flexibility.

[0049] In one example, a module in any of the above systems may be one or more integrated circuits configured to implement the above methods, such as one or more application-specific integrated circuits (ASICs), or one or more digital signal processors (DSPs), or one or more field-programmable gate arrays (FPGAs), or a combination of at least two of these integrated circuit forms.

[0050] For example, when modules in a system can be implemented through a processing element scheduler, the processing element can be a general-purpose processor, such as a central processing unit (CPU) or other processor capable of calling programs. Alternatively, these modules can be integrated together to form a system-on-a-chip (SOC).

[0051] In this application, various objects such as messages / information / devices / network elements / systems / apparatus / actions / operations / processes / concepts may be named. It is understood that these specific names do not constitute a limitation on the relevant objects. The names may be changed depending on the scenario, context, or usage habits. The understanding of the technical meaning of the technical terms in this application should be mainly determined from their functions and technical effects embodied / performed in the technical solution.

[0052] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and modules described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0053] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0054] The terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0055] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the foregoing application concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions claimed in this application.

Claims

1. A method for wireless transmission of PLC signals in an industrial Internet of Things (IoT), characterized in that, Applied to a transmitting end, wherein the transmitting end communicates with the receiving end via an industrial intranet, the method includes: Obtain the serial communication frame output by the source PLC system and input the serial communication frame to the protocol conversion module; The protocol conversion module parses the serial communication frame and encapsulates the parsed serial communication frame into a TCP / IP data packet based on a preset encapsulation rule; The TCP / IP data packets are input to the sending client terminal device, which monitors the monitoring information of each available wireless link in real time. The monitoring information includes signal strength, signal-to-noise ratio and network latency. Based on the monitoring information of each available wireless link, the primary link is determined. Priority identifiers are set for the TCP / IP data packets, and based on the priority queue scheduling strategy and the primary link, the TCP / IP data packets are transmitted to the receiving end in the industrial intranet via a wireless channel. The receiving end then decapsulates the TCP / IP data packets, strips the headers of each layer, and reconstructs them into Modbus RTU data frames based on pre-configured protocol mapping rules. These frames are then converted into serial communication signals and output to the target PLC system.

2. The method for wireless transmission of PLC signals in an industrial Internet of Things according to claim 1, characterized in that, The protocol conversion module parses the serial communication frame and encapsulates the parsed serial communication frame into a TCP / IP data packet based on preset encapsulation rules, including: The protocol conversion module extracts the Modbus RTU message from the serial communication frame. The Modbus RTU message includes the device address, function code, and data field. The CRC checksum of the Modbus RTU message is stripped, and a Modbus application protocol header is added to the header of the device address, function code, and data fields to form Modbus TCP application layer data. The Modbus application protocol header includes a transaction identifier, a protocol identifier, a length, and a unit identifier. The Modbus TCP application layer data is embedded as a payload into the data segment of the TCP packet. A TCP header, an IP header, and an Ethernet frame header are added sequentially outside the data segment of the TCP packet to obtain the TCP / IP data packet.

3. The method for wireless transmission of PLC signals in an industrial Internet of Things according to claim 1, characterized in that, The process of determining the primary link based on monitoring information from each available wireless link includes: The wireless link with the lowest network latency and a signal strength higher than a preset strength threshold is identified as the primary link.

4. The method for wireless transmission of PLC signals in an industrial Internet of Things according to claim 1, characterized in that, The transmission of TCP / IP packets to the receiving end in the industrial intranet via a wireless channel, based on the priority queue scheduling strategy and the primary link, includes: Set the Differential Service Code Point (DSCP) flag in the IP header of the TCP / IP data packet; Mark data packets containing PLC control signals as having the highest priority; Configure a priority queue scheduling algorithm in the sending end client terminal equipment and industrial intranet switch; The sending client terminal device transmits TCP / IP data packets marked with the highest priority to the receiving end in the industrial intranet via a wireless channel based on the primary link.

5. The method for wireless transmission of PLC signals in an industrial Internet of Things according to claim 1, characterized in that, The sending end client terminal device is a client device with dual SIM card redundant network access, and the method further includes: The sending end client terminal equipment periodically sends probe messages to the target node to monitor the signal receiving power and signal-to-noise ratio of the primary link in real time; If no probe response message is received for a set number of consecutive times, or if the signal quality of the primary link is lower than a preset threshold for a duration exceeding a set time, the primary link is determined to be faulty and the route is switched to the network link corresponding to the backup SIM card.

6. A method for wireless transmission of PLC signals in an industrial Internet of Things (IoT), characterized in that, Applied to a receiving end, wherein the receiving end communicates with the sending end via an industrial intranet, the method includes: The receiving end client terminal equipment receives TCP / IP data packets transmitted from the sending end from the industrial intranet. The TCP / IP data packets are formed by the protocol conversion module of the sending end by encapsulating the serial communication frames output by the source PLC system according to the preset encapsulation rules. The TCP / IP data packets are forwarded to the reverse protocol conversion module; The reverse protocol conversion module decapsulates the TCP / IP data packets, stripping away the TCP / IP header information layer by layer, and reconstructs them into Modbus RTU data frames based on pre-configured protocol mapping rules. The Modbus RTU data frame is converted into a serial communication signal and output to the target PLC system, so that the target PLC system can execute the corresponding control logic based on the Modbus RTU data frame.

7. The method for wireless transmission of PLC signals in an industrial Internet of Things according to claim 6, characterized in that, The reverse protocol conversion module strips the TCP / IP header information from the TCP / IP data packets layer by layer, and reconstructs them into Modbus RTU data frames based on pre-configured protocol mapping rules, including: The reverse protocol conversion module sequentially strips the Ethernet frame header, IP header, TCP header, and Modbus application protocol header of the TCP / IP data packet, and extracts the unit identifier, function code, and data field from the payload; Based on the pre-configured Modbus TCP to Modbus RTU mapping table, the unit identifier is used as the RTU device address. Combined with the function code and data field, the CRC checksum is recalculated and reconstructed into a standard Modbus RTU data frame.

8. The method for wireless transmission of PLC signals in an industrial Internet of Things according to claim 6, characterized in that, The reverse protocol conversion module also performs multiple data integrity checks during the signal restoration process, including: During the protocol decapsulation phase, cyclic redundancy check is performed on TCP / IP packets to verify whether bit errors have occurred during the transmission of TCP / IP packets; After Modbus RTU data frame reconstruction, CRC check is performed on the restored serial data frame; If a valid data packet is not successfully received or the verification fails within the preset timeout window, a retransmission request is initiated to the sender, and the number of retransmissions is no less than the set number. When consecutive retransmissions fail or the number of verification errors reaches a preset threshold, a local alarm signal is triggered.

9. A method for wireless transmission of PLC signals in an industrial Internet of Things according to claim 6, characterized in that, The reverse protocol conversion module has built-in security logic, and the method further includes: If no valid data packet is received within the preset timeout period or if the verification fails continuously, the reverse protocol conversion module outputs a predefined security value to the target PLC system. When a temporary network outage occurs, the reverse protocol conversion module outputs the last valid and correctly verified signal value in the cache until the network is restored or the timeout period is reached.

10. A PLC signal wireless transmission system for industrial Internet of Things, characterized in that, Includes the sending end and the receiving end; The sending end includes: The protocol conversion module is connected to the communication port of the source PLC system. It is used to obtain the serial communication frames output by the source PLC system, parse the serial communication frames, and encapsulate the parsed serial communication frames into TCP / IP data packets based on preset encapsulation rules. The transmitting client terminal device is connected to the protocol conversion module and is used to monitor the monitoring information of each available wireless link in real time. The monitoring information includes signal quality parameters and network latency. Based on the monitoring information of each available wireless link, the primary link is determined. Priority identifiers are set for the TCP / IP data packets, and based on the priority queue scheduling strategy and the primary link, the TCP / IP data packets are transmitted to the industrial intranet through the wireless channel. The receiving end includes: The receiving client terminal device is used to receive the TCP / IP data packets from the industrial intranet and send them to the reverse protocol conversion module; The reverse protocol conversion module is connected to the receiving end client terminal device and is used to decapsulate TCP / IP data packets, strip the TCP / IP header information layer by layer, and reconstruct them into Modbus RTU data frames based on pre-configured protocol mapping rules. The Modbus RTU data frames are then converted into serial communication signals and output to the target PLC system.

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