Control method based on PLC redundancy control device

Abstract

The invention relates to the field of PLC control, in particular to a control method based on a PLC redundancy control device. The method comprises the following steps: determining a main PLC (Programmable Logic Controller) and a standby PLC; interaction with a remote unit is carried out based on the main PLC controller; the monitoring device monitors the main PLC controller and obtains configuration information output by a communication interface in the main PLC controller at a preset time interval; when the main PLC controller breaks down, the standby PLC controller is switched to a new main PLC controller, the monitoring equipment is switched to monitor the new main PLC controller, and configuration information acquired from the main PLC controller which breaks down is synchronously sent to the new main PLC controller; after completing configuration based on the received configuration information, the new main PLC interacts with the remote unit; the method is used for realizing automatic switching of low-cost main and standby PLCs, and the hardware cost and the implementation complexity of the PLC redundancy control method are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of PLC control, and more specifically, to a control method based on a PLC redundant control device. Background Technology

[0002] Currently, a Programmable Logic Controller (PLC) is a digital control device that receives sensor signals and executes preset logic programs to automate the control of equipment such as fans, pumps, and valves, undertaking core functions such as equipment start-up and shutdown, frequency regulation, and status monitoring. However, when a control device is equipped with only a single PLC controller, its failure can lead to a single point of failure in the control system, causing unplanned downtime of the controlled equipment. This can result in economic losses or equipment malfunctions, especially in critical scenarios requiring high reliability. Therefore, implementing redundant PLC controllers is an important means to improve the fault tolerance of control devices.

[0003] Existing redundancy control methods often employ high-end industrial PLC controllers, achieving millisecond-level switching between primary and backup PLCs through dedicated redundancy modules, hardware-level fault detection modules, and data synchronization protocol modules. While these high-end industrial PLCs offer high-precision synchronization and strong stability, their high hardware procurement costs, complex parameter configuration processes, and redundancy architecture supporting complex processes at multiple sites far exceed the actual needs of simple scenarios that only require handling basic logic such as start / stop commands and frequency settings. In such simple scenarios, a switching time of seconds is acceptable for PLC switching. This performance-overkill design significantly raises the deployment threshold for small and medium-sized projects or scenarios, forcing some setups to adopt a compromise approach of using ordinary non-redundant PLCs and manual switching. However, this method has significant drawbacks: relying on manual PLC switching can lead to a response delay of minutes when a single PLC fails, during which control link interruptions can easily cause fluctuations in operating conditions; relying on manual switching also presents the problem of wiring errors, and the lack of real-time synchronization of configuration information between multiple PLCs in existing technologies may also trigger abnormal equipment actions or even hardware damage. Summary of the Invention

[0004] This invention provides a control method based on a PLC redundancy control device, which enables automatic switching between low-cost primary and backup PLCs, significantly reducing the hardware cost and implementation complexity of PLC redundancy control methods.

[0005] According to a first aspect of this application, a control method based on a PLC redundant control device is provided, wherein the PLC redundant control device includes a first PLC controller, a second PLC controller, a first intermediate relay, a second intermediate relay, a remote unit, a network interconnection device, and a monitoring device; The digital output interface of the first PLC controller is connected to the digital input interface of the second PLC controller through the first intermediate relay; The digital output interface of the second PLC controller is connected to the digital input interface of the first PLC controller through the second intermediate relay; The communication interface of the first PLC controller is connected to the remote unit through the first intermediate relay; the communication interface of the second PLC controller is connected to the remote unit through the second intermediate relay. The Ethernet interface of the first PLC controller is connected to the network interconnection device via a network cable, and the Ethernet interface of the second PLC controller is connected to the network interconnection device via a network cable. The network interconnection device is connected to the monitoring device; The method includes: The primary PLC controller and the backup PLC controller are determined, wherein the primary PLC controller is either the first PLC controller or the second PLC controller, and the backup PLC controller is either the second PLC controller or the first PLC controller. The main PLC controller interacts with the remote unit; the monitoring device monitors the main PLC controller and acquires the configuration information output by the communication interface of the main PLC controller at preset time intervals. When the primary PLC controller fails, the backup PLC controller switches to the new primary PLC controller, the monitoring device switches to monitor the new primary PLC controller, and synchronously sends the configuration information obtained from the failed primary PLC controller to the new primary PLC controller. After the new master PLC controller completes its configuration based on the received configuration information, it interacts with the remote unit.

[0006] Understandably, based on the hardware collaborative architecture of dual PLC controllers and intermediate relays, combined with the networked design of network interconnection devices and monitoring devices, low-cost redundant control of the main and backup PLC controllers is achieved; through the signal interaction logic of digital input / output interfaces, the main and backup PLC controllers can automatically switch within seconds after a fault occurs, ensuring uninterrupted operation of remote unit communication and monitoring links.

[0007] Optionally, determining the primary PLC controller and the backup PLC controller includes: The first PLC controller receives input signals from its digital input interface, while the second PLC controller receives input signals from its digital input interface. If the first PLC controller does not receive an input signal from its digital input interface within a preset time, the first PLC controller outputs a high-level output signal through its digital output interface, the first intermediate relay closes, and the first PLC controller becomes the master PLC controller; if the second PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, the second intermediate relay opens, and the second PLC controller becomes the backup PLC controller. If the second PLC controller does not receive an input signal from its digital input interface within a preset time, the second PLC controller outputs a high-level output signal through its digital output interface, the second intermediate relay closes, and the second PLC controller becomes the master PLC controller; if the first PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, the first intermediate relay opens, and the first PLC controller becomes the backup PLC controller.

[0008] Understandably, through the collaborative logic of digital input / output interfaces and intermediate relays, automatic identification and primary / backup allocation of PLC controllers are achieved. When the PLC is powered on for the first time, if the first or second PLC controller detects that it cannot receive an input signal, it immediately outputs a high-level output signal through the digital output interface to drive the corresponding intermediate relay to close, thereby activating the primary PLC controller. At the same time, after receiving the high-level input signal, the other PLC controller automatically stops outputting and disconnects its corresponding intermediate relay to switch to standby mode. This ensures conflict-free switching between primary and standby PLC controllers, avoids control logic conflicts caused by the simultaneous operation of two PLC controllers, significantly improves the reliability of the device, and completes the primary / backup switch within seconds without the need for complex protocols, laying a stable foundation for subsequent fault switching.

[0009] Optionally, when the primary PLC controller fails, the backup PLC controller switches to a new primary PLC controller, including: If the main PLC controller is the first PLC controller and when the main PLC controller fails, the digital output interface of the main PLC controller stops outputting signals, and the first intermediate relay is disconnected. After the backup PLC controller fails to receive an input signal from its digital input interface within a preset time, it outputs a high-level output signal through its digital output interface, the second intermediate relay closes, and the backup PLC controller switches to the new master PLC controller. After the primary PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, and the primary PLC controller switches to a new backup PLC controller. And / or, if the primary PLC controller is a secondary PLC controller and when the primary PLC controller malfunctions, the digital output interface of the primary PLC controller stops outputting signals, and the second intermediate relay is disconnected; After the backup PLC controller fails to receive an input signal from its digital input interface within a preset time, it outputs a high-level output signal through its digital output interface, the first intermediate relay closes, and the backup PLC controller switches to the new master PLC controller. After the primary PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, and the primary PLC controller switches to a new backup PLC controller.

[0010] Understandably, through the intelligent linkage mechanism between the digital input / output interface and the intermediate relay, when the primary PLC controller fails, the backup PLC controller, after confirming the interruption of the input signal within a preset time, immediately outputs a high-level output signal to seamlessly take over the remote unit. At the same time, the original primary PLC controller automatically stops outputting and switches to standby mode after receiving the corresponding high-level input signal. This achieves conflict-free switching between primary and backup PLC controllers with delays strictly controlled within seconds, ensuring the continuity of the control link and the stability of the device, and significantly improving the real-time response capability and operational reliability of the device.

[0011] Optionally, the remote unit includes a remote input / output unit and a remote interaction unit; The communication interface of the first PLC controller is connected to the remote input / output unit through the first intermediate relay; the communication interface of the second PLC controller is connected to the remote input / output unit through the second intermediate relay. The communication interface of the first PLC controller is also connected to the remote interaction unit through the first intermediate relay; the communication interface of the second PLC controller is also connected to the remote interaction unit through the second intermediate relay.

[0012] Understandably, by bidirectionally interconnecting the communication interfaces of the first and second PLC controllers with the remote input / output unit and the remote interaction unit via the first and second intermediate relays respectively, a redundant communication architecture is constructed. This ensures seamless real-time data acquisition and interaction of the remote unit during the switching of the primary and backup PLC controllers, avoiding communication interruptions caused by the failure of the primary PLC controller and significantly improving the continuous operation capability of the device. At the same time, relying on the intermediate relays to achieve physical isolation and signal routing, communication resources can be dynamically allocated without complex protocols. This reduces the difficulty of hardware implementation and ensures the stability of remote monitoring and operation, perfectly adapting to the high reliability requirements of low-cost redundancy in simple control scenarios.

[0013] Optionally, the interaction between the primary PLC controller and the remote unit includes: If the main PLC controller is the first PLC controller, then the communication interface of the main PLC controller outputs a high-level output signal, the first intermediate relay closes, the second intermediate relay opens, the main PLC controller connects to the remote unit, and the main PLC controller interacts with the remote unit. If the primary PLC controller is a secondary PLC controller, then the communication interface of the primary PLC controller outputs a high-level output signal, the first intermediate relay is disconnected, the second intermediate relay is closed, the primary PLC controller is connected to the remote unit, and the primary PLC controller interacts with the remote unit.

[0014] Understandably, by dynamically adjusting the intermediate relay status based on the master PLC controller, when the first PLC controller acts as the master PLC controller, it outputs a high level to close the first relay and open the second relay to connect the remote unit, or when the second PLC controller acts as the master PLC controller, it performs the reverse operation. This precisely ensures that only the current master PLC controller establishes a stable communication link with the remote unit, effectively preventing signal conflicts caused by the simultaneous access of two controllers. It also maintains zero-interruption continuity of data acquisition and command interaction during master-slave switching, significantly improving the real-time control accuracy and operational robustness of the device.

[0015] Optionally, the new master PLC controller interacts with the remote unit, including: If the new master PLC controller is the second PLC controller, then the communication interface of the new master PLC controller outputs a high-level output signal, the first intermediate relay is opened, the second intermediate relay is closed, the new master PLC controller is connected to the remote unit, and the new master PLC controller interacts with the remote unit. If the new master PLC controller is the first PLC controller, then the communication interface of the new master PLC controller outputs a high-level output signal, the first intermediate relay closes, the second intermediate relay opens, the new master PLC controller connects to the remote unit, and the new master PLC controller interacts with the remote unit.

[0016] Understandably, by dynamically controlling the state of the intermediate relays through the high-level output signal of the new master PLC controller, the second relay is closed and the first relay is opened when the second PLC controller acts as the new master PLC controller, or the reverse operation is performed when the first PLC acts as the new master PLC controller. This accurately achieves real-time communication between a single controller and the remote unit, completely eliminates signal interference caused by the parallel access of two PLCs, and maintains complete continuity of data acquisition and command transmission at the moment of switching, significantly enhancing the real-time response capability and operational stability of the device.

[0017] Optionally, the monitoring device is pre-installed with a network address switching script; When the primary PLC controller fails, the monitoring device switches to monitoring the new primary PLC controller, including: When the main PLC controller malfunctions, the main PLC controller stops sending communication signals to the monitoring device; If the monitoring device fails to receive a communication signal from the primary PLC controller within a preset time, it will monitor the new primary PLC controller after establishing a connection with it based on the network address switching script.

[0018] Understandably, by pre-setting a network address switching script in the monitoring equipment, when the primary PLC controller fails and stops sending communication signals, the monitoring equipment can automatically detect the signal interruption within a preset time and quickly establish a stable connection with the new primary PLC controller based on the network address switching script. This achieves seamless switching of the monitoring link within seconds, completely eliminating the risk of monitoring disconnection caused by controller failure, significantly improving the real-time monitoring continuity and operational reliability of the device. At the same time, relying on the network address switching script greatly reduces the need for manual intervention and effectively simplifies the operation and maintenance process.

[0019] Optionally, the monitoring device is pre-loaded with a configuration information synchronization script; The step of synchronously sending the configuration information obtained from the faulty primary PLC controller to the new primary PLC controller also includes: The monitoring device, based on the configuration information synchronization script, synchronously sends the configuration information obtained from the faulty primary PLC controller to the new primary PLC controller, and at the same time intervals, obtains the configuration information output by the communication interface of the new primary PLC controller.

[0020] Understandably, by pre-setting configuration information synchronization scripts in the monitoring equipment, dynamic configuration management is achieved when the primary PLC controller fails. The monitoring equipment automatically obtains configuration information from the failed PLC controller and synchronizes it to the new primary PLC controller in real time. At the same time, it continuously collects configuration information of the communication interface of the new primary PLC controller at preset time intervals, ensuring seamless continuation of control logic without conflicts. This completely eliminates the risk of device control interruption caused by configuration loss and significantly improves the continuity and consistency of control. Relying on configuration information scripts, complex information migration can be completed without manual intervention, greatly reducing the complexity of operation and maintenance and the error rate, and providing efficient, reliable, and low-cost redundancy protection for simple control scenarios.

[0021] Optionally, the network interconnection device is an industrial switch; And / or, the monitoring device is a monitoring host computer; And / or, the remote input / output unit includes a plurality of remote input / output sub-units connected in parallel.

[0022] Understandably, a highly reliable network architecture is built using industrial switches to ensure zero-packet-loss data transmission between the main and backup PLC controllers and the monitoring host computer; the monitoring host computer integrates pre-set scripts to achieve automatic fault diagnosis and parameter synchronization, simplifying manual intervention; the remote input / output unit adopts a parallel sub-unit design, supporting dynamic expansion and configuration, significantly improving the scalability of the device.

[0023] Optionally, both the first PLC controller and the second PLC controller are S7-200 PLC controllers; And / or, the remote interaction unit is a human-computer interaction touchscreen.

[0024] Understandably, using the low-cost S7-200 PLC as the primary and backup controllers allows for rapid deployment with only a conventional programming environment, significantly reducing implementation complexity. Meanwhile, the remote interaction unit is a human-machine interface touchscreen, providing an intuitive and visual operating interface and real-time status feedback, which significantly improves the convenience of on-site operation and maintenance.

[0025] Based on any of the above aspects, the control method, system, electronic device, and storage medium based on a PLC redundant control device provided in this application can achieve the following effects: Meeting the low-cost requirements of simple control scenarios, this system achieves second-level switching between primary and backup PLC controllers: By employing a low-cost S7-200 PLC as both the primary and backup PLC controllers, combined with intermediate relays and industrial switches, it eliminates the need for dedicated redundancy modules or high-performance functions of high-end PLC controllers, significantly reducing hardware costs. Simultaneously, based on the signal interaction logic of digital input / output interfaces and the relay switching mechanism, the primary and backup PLC controllers automatically switch within 3 seconds of a primary controller failure, ensuring the continuity of remote unit data acquisition and monitoring equipment. This avoids control interruptions caused by single-point failures of the PLC controller, perfectly adapting to the low-cost and real-time switching requirements of simple control redundancy scenarios.

[0026] It boasts strong scalability and reduces maintenance complexity: Utilizing standardized relay and industrial switch hardware architecture and a universal programming environment, it eliminates the need for complex redundant protocol configurations. Maintenance personnel only need basic PLC maintenance skills to troubleshoot and maintain the device. The primary and backup PLC controllers can synchronize configuration information during switching, ensuring identical control logic after the switch and significantly reducing subsequent debugging workload. Furthermore, the device can connect several remote input / output sub-units in parallel without adjusting the redundant architecture, flexibly adapting to centralized control scenarios of different scales, combining high scalability with a low maintenance threshold.

[0027] Seamless switching and configuration information synchronization between primary and backup PLC controllers are achieved: By using pre-set network address switching and configuration information synchronization scripts, the monitoring equipment can automatically detect communication interruptions after a primary PLC controller failure and seamlessly switch to the backup PLC controller's network connection within a preset time, ensuring continuous monitoring. Simultaneously, the monitoring equipment actively acquires the configuration information output from the primary PLC's digital interface at preset time intervals and synchronizes the pre-failure configuration information to the new primary PLC controller in real time during the switching process, enabling rapid recovery of control logic. This not only achieves zero disconnection in the monitoring link but also ensures the consistency of configuration information between the primary and backup PLC controllers, completely eliminating control logic conflicts after the switch. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a circuit diagram of a PLC redundant control device provided in this embodiment.

[0030] Figure 2 This is a flowchart of a control method based on a PLC redundant control device provided in this embodiment.

[0031] Figure 3 The process for determining the switching between primary and backup PLC controllers provided in this embodiment Figure 1 .

[0032] Figure 4 The process for determining the switching between primary and backup PLC controllers provided in this embodiment Figure 2 .

[0033] Figure 5 This embodiment provides a flowchart for monitoring the new primary PLC controller during the switching of monitoring equipment.

[0034] Icons: 110 - First PLC Controller, 120 - Second PLC Controller, 210 - First Intermediate Relay, 220 - Second Intermediate Relay, 300 - Remote Unit, 301 - Remote Input / Output Unit, 3011 - First Remote Input / Output Subunit, E - Positive Communication Interface of First Remote Input / Output Subunit, F - Negative Communication Interface of First Remote Input / Output Subunit, 3012 - Second Remote Input / Output Subunit, G - Positive Communication Interface of Second Remote Input / Output Subunit, H - Negative Communication Interface of Second Remote Input / Output Subunit, 3013 - Third Remote Input / Output Subunit, J - Positive Communication Interface of Third Remote Input / Output Subunit, K - Negative Communication Interface of Third Remote Input / Output Subunit, 302 - Remote Interaction Unit, M - Positive Communication Interface of Remote Interaction Unit, N - Negative Communication Interface of Remote Interaction Unit. 401 - Network interconnection device, 402 - Monitoring device, 111 - Digital output interface of the first PLC controller, 112 - Digital input interface of the first PLC controller, 121 - Digital output interface of the second PLC controller, 122 - Digital input interface of the first PLC controller, 113 - Communication interface of the first PLC controller, 1131 - First communication interface of the first PLC controller, A1 - First positive communication interface of the first PLC controller, B1 - First negative communication interface of the first PLC controller, 1132 - Second communication interface of the first PLC controller, A2 - Second positive communication interface of the first PLC controller, B2 - Second negative communication interface of the first PLC controller, 123 - ... The communication interfaces of the two PLC controllers are as follows: 1231 - First communication interface of the second PLC controller; C1 - First positive communication interface of the second PLC controller; D1 - First negative communication interface of the second PLC controller; 1232 - Second communication interface of the second PLC controller; C2 - Second positive communication interface of the second PLC controller; D2 - Second negative communication interface of the second PLC controller; 114 - Ethernet interface of the first PLC controller; 124 - Ethernet interface of the second PLC controller; 115 - Negative voltage interface of the first PLC controller; 116 - Positive voltage interface of the first PLC controller; 125 - Negative voltage interface of the second PLC controller; 126 - Positive voltage interface of the second PLC controller. Detailed Implementation

[0035] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this application. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product; it is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0036] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0037] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0038] Existing redundancy methods for high-end PLC controllers are difficult to apply to simple scenarios requiring only second-level switching due to their high cost and complex configuration. On the other hand, redundancy methods that rely on manual switching result in response delays of up to minutes, a high risk of misoperation, and a lack of a real-time configuration information synchronization mechanism, which can easily lead to equipment malfunctions or hardware damage.

[0039] This embodiment provides a technical solution that can solve the above problems. The specific implementation of this application will be described in detail below with reference to the accompanying drawings.

[0040] like Figure 1 As shown in the figure, this embodiment provides a circuit diagram of a PLC redundancy control device, which includes a first PLC controller 110, a second PLC controller 120, a first intermediate relay 210, a second intermediate relay 220, a remote unit 300, a network interconnection device 401, and a monitoring device 402. The digital output interface 111 of the first PLC controller 110 is connected to the digital input interface 122 of the second PLC controller 120 through the first intermediate relay 210; The digital output interface 121 of the second PLC controller 120 is connected to the digital input interface 112 of the first PLC controller 120 through the second intermediate relay 220; The communication interface 113 of the first PLC controller 120 is connected to the remote unit 300 through the first intermediate relay 210; the communication interface 123 of the second PLC controller 120 is connected to the remote unit 300 through the second intermediate relay 120. The Ethernet interface 114 of the first PLC controller 110 is connected to the network interconnection device 401 via a network cable, and the Ethernet interface 124 of the second PLC controller 120 is connected to the network interconnection device 401 via a network cable; Preferably, the Ethernet interface 114 of the first PLC controller 110 and the Ethernet interface 124 of the second PLC controller 120 can be RJ45 Ethernet interfaces, and the network cable can be an RJ45 Ethernet cable.

[0041] The network interconnection device 401 is connected to the monitoring device 402.

[0042] Specifically, the remote unit 300 includes a remote input / output unit 301 and a remote interaction unit 302; The communication interface 113 of the first PLC controller 110 is connected to the remote input / output unit 301 through the first intermediate relay 210; the communication interface 123 of the second PLC controller 120 is connected to the remote input / output unit 301 through the second intermediate relay 220. The communication interface 113 of the first PLC controller 110 is also connected to the remote interaction unit 302 through the first intermediate relay 210; the communication interface 123 of the second PLC controller 120 is also connected to the remote interaction unit 320 through the second intermediate relay 220.

[0043] Understandably, in this embodiment, the first intermediate relay 210 has three contacts, namely three input terminals and three output terminals. The digital output interface 111 of the first PLC controller 110 is connected to the first input terminal of the first intermediate relay 210, and the first output terminal of the first intermediate relay 210 is connected to the digital input interface 122 of the second PLC controller 120. The communication interface 113 of the first PLC controller 110 is connected to the second input terminal of the first intermediate relay 210, and the second output terminal of the first intermediate relay 210 is connected to the remote input / output unit 301. The communication interface 113 of the first PLC controller 110 is connected to the third input terminal of the first intermediate relay 210, and the third output terminal of the first intermediate relay 210 is connected to the remote interaction unit 302. Similarly, the second intermediate relay 220 has three contacts, namely three input terminals and three output terminals. The digital output interface 121 of the second PLC controller 120 is connected to the first input terminal of the second intermediate relay 220, and the first output terminal of the second intermediate relay 220 is connected to the digital input interface 112 of the first PLC controller 110. The communication interface 123 of the second PLC controller 120 is connected to the second input terminal of the second intermediate relay 220, and the second output terminal of the second intermediate relay 220 is connected to the remote input / output unit 301. The communication interface 123 of the second PLC controller 120 is connected to the third input terminal of the second intermediate relay 220, and the third output terminal of the second intermediate relay 220 is connected to the remote interaction unit 302.

[0044] Specifically, the remote input / output unit includes several remote input / output sub-units connected in parallel.

[0045] It is understood that, in this embodiment, the remote input / output unit includes a first remote input / output subunit 3011, a second remote input / output subunit 3012, and a third remote input / output subunit 3013 connected in parallel. The first remote input / output subunit 3011 further includes a positive communication interface E and a negative communication interface F, the second remote input / output subunit 3012 further includes a positive communication interface G and a negative communication interface H, and the third remote input / output subunit 3013 further includes a positive communication interface J and a negative communication interface K.

[0046] The communication interface 113 of the first PLC controller 110 includes a first communication interface 1131 and a second communication interface 1132. The first communication interface 1131 includes a positive communication interface A1 and a negative communication interface B1, and the second communication interface 1132 includes a positive communication interface A2 and a negative communication interface B2. The positive communication interface A1 of the first communication interface 1131 of the first PLC controller 110 is connected to the second input terminal of the first intermediate relay 210, and the second output terminal of the first intermediate relay 210 is connected to the parallel positive communication interfaces E, G, and J of the first remote input / output unit. The negative communication interface B1 of the first communication interface 1131 of the first PLC controller 110 is connected to the third input terminal of the first intermediate relay 210, and the third output terminal of the first intermediate relay 210 is connected to the parallel negative communication interfaces F, H, and K of the first remote input / output unit. Similarly, the communication interface 123 of the second PLC controller 120 includes a first communication interface 1231 and a second communication interface 1232. The first communication interface 1231 includes a positive communication interface C1 and a negative communication interface D1, and the second communication interface 1232 includes a positive communication interface C2 and a negative communication interface D2. The positive communication interface C1 of the first communication interface 1231 of the second PLC controller 120 is connected to the second input terminal of the second intermediate relay 220, and the second output terminal of the second intermediate relay 220 is connected to the parallel positive communication interfaces E, G, and J of the first remote input / output unit. The negative communication interface D1 of the first communication interface 1231 of the second PLC controller 120 is connected to the third input terminal of the second intermediate relay 220, and the third output terminal of the second intermediate relay 220 is connected to the parallel negative communication interfaces F, H, and K of the first remote input / output unit.

[0047] It is understood that, in this embodiment, the remote interaction unit includes a positive communication interface M and a negative communication interface N.

[0048] The positive communication interface A2 of the second communication interface 1132 of the first PLC controller 110 is connected to the third input terminal of the first intermediate relay 210, and the third output terminal of the first intermediate relay 210 is connected to the positive communication interface M of the remote interaction unit 302; the negative communication interface B2 of the second communication interface 1132 of the first PLC controller 110 is connected to the third input terminal of the first intermediate relay 210, and the third output terminal of the first intermediate relay 210 is connected to the negative communication interface N of the remote interaction unit. Similarly, the positive communication interface C2 of the second communication interface 1232 of the second PLC controller 120 is connected to the third input terminal of the second intermediate relay 220, and the third output terminal of the second intermediate relay 220 is connected to the positive communication interface M of the remote interaction unit 302; the negative communication interface D2 of the second communication interface 1232 of the second PLC controller 120 is connected to the third input terminal of the second intermediate relay 220, and the third output terminal of the second intermediate relay 220 is connected to the negative communication interface N of the remote interaction unit.

[0049] Preferably, in this embodiment, the communication interface can be an RS485 communication interface, and an RS485 communication cable is used to complete the connection.

[0050] In this embodiment, the remote input / output subunit can be a device that needs to be controlled, such as a fan, water pump, water valve, air valve, sensor, or instrument. The remote input / output subunit can receive control commands from the first PLC controller or the second PLC controller and operate based on the control commands.

[0051] Specifically, the network interconnection device is an industrial switch; In this embodiment, the industrial switch can transmit relevant data of the first PLC controller 110 or the second PLC controller 120 to the monitoring device in accordance with a common communication protocol, so that the monitoring device can obtain the operating status of the first PLC controller 110 or the second PLC controller 120 in a timely manner and complete the monitoring.

[0052] Specifically, the monitoring device is a monitoring host computer; In this embodiment, the monitoring host computer can be a monitoring computer, which can monitor the operating status of the first PLC controller 110 or the second PLC controller 120 from the operating information of the first PLC controller 110 or the second PLC controller 120.

[0053] Specifically, both the first PLC controller and the second PLC controller are S7-200 PLC controllers.

[0054] In this embodiment, the S7-200 PLC controller is a lower-cost controller compared to high-end controllers such as the Siemens S7-1500 series or the Schneider Modicon M340 / M580 redundant series, thereby reducing the overall cost of building a redundant control device and making it more suitable for simple control scenarios.

[0055] Preferably, the first PLC controller 110 further includes a positive voltage interface 115 and a negative voltage interface 116, and the second PLC controller 120 further includes a positive voltage interface 125 and a negative voltage interface 126, so that the first PLC controller 110 and the second PLC controller 120 can be powered through the positive and negative voltage interfaces.

[0056] Specifically, the remote interaction unit is a human-computer interaction touchscreen.

[0057] In this embodiment, the human-machine interface touchscreen is an HMI (Human Machine Interface) touchscreen, which can obtain the operating status of the remote input / output unit from the first PLC controller or the second PLC controller. The operator can output relevant control commands on the HMI touchscreen, and the control commands can be sent to the first PLC controller or the second PLC controller, which then transmits them to the remote input / output unit to control the operating status of the remote input / output unit.

[0058] like Figure 2 As shown, a control method based on a PLC redundant control device is provided, which can be further divided into the following steps: S100. Determine the primary PLC controller and the backup PLC controller, wherein the primary PLC controller is the first PLC controller or the second PLC controller, and the backup PLC controller is the second PLC controller or the first PLC controller. In this embodiment, the primary PLC controller is responsible for executing control commands in real time and processing the received input / output unit operating status. The backup PLC controller monitors the operating health of the primary PLC controller in real time and seamlessly takes over control when the primary PLC controller fails, ensuring uninterrupted continuous operation of the redundant control device.

[0059] Specifically, determining the primary PLC controller and the backup PLC controller includes: The first PLC controller receives input signals from its digital input interface, while the second PLC controller receives input signals from its digital input interface. If the first PLC controller does not receive an input signal from its digital input interface within a preset time, the first PLC controller outputs a high-level output signal through its digital output interface, the first intermediate relay closes, and the first PLC controller becomes the master PLC controller; if the second PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, the second intermediate relay opens, and the second PLC controller becomes the backup PLC controller. If the second PLC controller does not receive an input signal from its digital input interface within a preset time, the second PLC controller outputs a high-level output signal through its digital output interface, the second intermediate relay closes, and the second PLC controller becomes the master PLC controller; if the first PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, the first intermediate relay opens, and the first PLC controller becomes the backup PLC controller.

[0060] In this embodiment, the determination of the primary PLC controller and the backup PLC controller occurs when the first and second PLC controllers are first synchronously connected to power. When the first and second PLC controllers are first connected to power, they need to compete to become the primary PLC controller. During the preparation phase, the first and second PLC controllers first check whether their digital input interfaces can receive input signals. Because the digital input interface of the first PLC controller is connected to the digital output interface of the second PLC controller, and the digital input interface of the second PLC controller is connected to the digital output interface of the first PLC controller, and neither the first nor the second digital input interface outputs signals during the preparation phase, neither the first nor the second PLC controller can receive input signals from their digital input interfaces.

[0061] Therefore, if the first and second PLC controllers do not receive input signals from their digital input interfaces within a preset time, they will generate high-level output signals from their digital output interfaces. Preferably, in the initial preemption process of the master PLC controller, this preset time can be 0 seconds, or it can be preset according to the actual situation. If the first PLC controller generates a high-level output signal from its digital output interface, the first intermediate relay will cause its first output terminal to be energized due to the high level at its first input terminal. Thus, the high-level output signal can be transmitted to the second PLC controller through the first intermediate relay. After the second PLC controller receives the high-level input signal in its digital input interface, it indicates that the first PLC controller has successfully preempted the master PLC controller. According to the preset setting, there is only one master PLC controller, so the second PLC controller will immediately stop signal output. The second intermediate relay will then be deactivated due to the low level at its first input terminal, thus the second PLC controller becomes the backup PLC controller, thereby completing the determination of the master and backup PLC controllers.

[0062] Similarly, if the second PLC controller can preemptively become the primary PLC controller, the first PLC controller will become the backup PLC controller. The preemption process for the second PLC controller is similar to that for the first PLC controller, and will not be described in detail here.

[0063] S200. The main PLC controller interacts with the remote unit; the monitoring device monitors the main PLC controller and acquires the configuration information output by the communication interface of the main PLC controller at preset time intervals. In this embodiment, the primary PLC controller interacts with the remote unit through its communication interface, including sending control commands to the remote unit to control the remote unit, and the remote unit uploading its operating status to the primary PLC controller so that the primary PLC controller can monitor the remote unit in real time.

[0064] In this embodiment, the primary PLC controller sends a communication signal to the monitoring device, enabling the monitoring device to establish a network connection with the primary PLC controller. The primary PLC controller, having established a network connection with the monitoring device, can cyclically send its own operating status and configuration information to the monitoring device at preset time intervals. This allows the monitoring device to monitor the primary PLC controller in real time and prepares the data foundation for configuration information synchronization for subsequent switching.

[0065] Specifically, the interaction between the main PLC controller and the remote unit includes: If the main PLC controller is the first PLC controller, then the communication interface of the main PLC controller outputs a high-level output signal, the first intermediate relay closes, the second intermediate relay opens, the main PLC controller connects to the remote unit, and the main PLC controller interacts with the remote unit. If the primary PLC controller is a secondary PLC controller, then the communication interface of the primary PLC controller outputs a high-level output signal, the first intermediate relay is disconnected, the second intermediate relay is closed, the primary PLC controller is connected to the remote unit, and the primary PLC controller interacts with the remote unit.

[0066] In this embodiment, if the primary PLC controller is a first PLC controller, then the communication interface of the primary PLC controller outputs a high-level output signal. Upon receiving the high-level signal, the second input terminal of the first intermediate relay activates its second output terminal, enabling the high-level output signal of the primary PLC controller to be sent to the remote input / output unit. This high-level output signal carries control commands, allowing the remote input / output unit to operate based on these commands. The remote input / output unit can then transmit its operating status back to the primary PLC controller via this communication link, thus enabling interaction between the primary PLC controller and the remote unit.

[0067] Similarly, when the communication interface of the main PLC controller outputs a high-level output signal, the third input terminal of the first intermediate relay receives the high-level signal, causing the third output terminal of the first intermediate relay to engage. This enables the main PLC controller to communicate with the remote interaction unit. The remote interaction unit can then send control commands set by the operator in the remote interaction unit to the main PLC controller. The main PLC controller then sends the control commands to the remote input / output unit via the communication interface and the second output terminal of the first intermediate relay, allowing the remote input / output unit to operate based on the control commands. The remote input / output unit can also transmit its operating status back to the main PLC controller via this communication link. The main PLC controller also sends the operating status of the remote input / output unit to the remote interaction unit via the communication interface and the third output terminal of the first intermediate relay, enabling the remote interaction unit to monitor the operating status of the remote input / output unit.

[0068] Similarly, if the primary PLC controller is the second PLC controller, its interaction process with the remote unit is similar to that of the primary PLC controller, and will not be described again here.

[0069] S300. When the primary PLC controller fails, the backup PLC controller is switched to a new primary PLC controller, the monitoring device is switched to monitor the new primary PLC controller, and the configuration information obtained from the failed primary PLC controller is synchronously sent to the new primary PLC controller. In this embodiment, when the primary PLC controller fails, it cannot perform operations such as sending control commands and monitoring remote units. Therefore, it is necessary to switch the backup PLC controller to a new primary PLC controller to complete the above tasks, ensuring normal control and monitoring of the remote units. Simultaneously, the monitoring equipment also needs to switch to monitoring the new primary PLC controller to enable real-time monitoring of its operation.

[0070] Specifically, such as Figure 3 As shown, when the primary PLC controller fails, the backup PLC controller switches to the new primary PLC controller, which may include the following steps: S311. If the main PLC controller is the first PLC controller and the main PLC controller fails, the digital output interface of the main PLC controller stops outputting signals, and the first intermediate relay is disconnected. In this embodiment, when the main PLC controller malfunctions, it can no longer output control commands and high-level output signals. Therefore, the first input terminal of the first intermediate relay is at a low level, causing the first output terminal of the first intermediate relay to disconnect.

[0071] S312. After the backup PLC controller fails to receive an input signal from its digital input interface within a preset time, it outputs a high-level output signal through its digital output interface, the second intermediate relay closes, and the backup PLC controller switches to a new master PLC controller. In this embodiment, after the first output terminal of the first intermediate relay is disconnected, a high-level input signal cannot be received at the digital input interface of the backup PLC controller. After a preset time, the backup PLC controller, having investigated for accidental electrical connection errors, determines that the primary PLC controller has failed and needs to switch over to become the primary PLC controller, taking over the control of the remote unit. Preferably, the time can be preset according to the actual situation.

[0072] The standby PLC controller outputs a high-level output signal through its digital output interface. The first input terminal of the second intermediate relay is at a high level, and the first output terminal of the second intermediate relay is set to be energized, so that the high-level output signal is input to the main PLC controller, thereby switching the standby PLC controller to the new main PLC controller.

[0073] S313. After the main PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, and the main PLC controller switches to a new standby PLC controller.

[0074] In this embodiment, after the primary PLC controller receives the corresponding high-level input signal through its digital input interface, it knows that the backup PLC controller has become the new primary PLC controller. Then, it stops outputting signals through its own digital output interface to avoid conflict in the transmission of control commands. The faulty primary PLC controller is switched to the new backup PLC controller.

[0075] In another implementation, such as Figure 4 As shown, when the primary PLC controller fails, the backup PLC controller switches to the new primary PLC controller, which may include the following steps: S321. If the main PLC controller is a second PLC controller and the main PLC controller malfunctions, the digital output interface of the main PLC controller stops outputting signals, and the second intermediate relay is disconnected. S322. After the backup PLC controller fails to receive an input signal from its digital input interface within a preset time, it outputs a high-level output signal through its digital output interface, the first intermediate relay closes, and the backup PLC controller switches to a new master PLC controller. S323. After the main PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, and the main PLC controller switches to a new standby PLC controller.

[0076] In this embodiment, when the primary PLC controller is the second PLC controller, the switching between the primary and backup PLC controllers is similar to the switching when the primary PLC controller is the first PLC controller, so it will not be described again here.

[0077] Specifically, the monitoring device is pre-installed with a network address switching script; In this embodiment, corresponding network addresses can be preset for the first PLC controller and the second PLC controller. The monitoring device connects to the first PLC controller and the second PLC controller via its corresponding network address. The network address switching script can detect when the primary PLC controller fails and switch the monitoring device to the new primary PLC controller, enabling continuous monitoring of the primary PLC controller.

[0078] like Figure 5 As shown, when the primary PLC controller fails, the monitoring device switches to monitoring the new primary PLC controller, which may include the following steps: S331. When the main PLC controller malfunctions, the main PLC controller stops sending communication signals to the monitoring device. In this embodiment, when the primary PLC controller fails, the primary PLC controller is unable to send communication signals to the monitoring device through its Ethernet interface, and the monitoring device is also unable to receive the communication signals and configuration information of the failed primary PLC controller.

[0079] S332. If the monitoring device fails to receive the communication signal from the primary PLC controller within a preset time, it will monitor the new primary PLC controller after completing the connection with the new primary PLC controller based on the network address switching script.

[0080] In this embodiment, if the monitoring device still cannot receive the communication signal from the primary PLC controller within a preset time, accidental errors in the electrical connection can be ruled out, and the primary PLC controller can be determined to have malfunctioned. Preferably, the time can be preset to a corresponding duration according to the actual situation. Therefore, based on the network address switching script, the network connection with the malfunctioning primary PLC controller is disconnected, and a network connection is established with the new primary PLC controller based on the new primary PLC controller's network address, thereby enabling monitoring of the new primary PLC controller.

[0081] Specifically, the monitoring device has a pre-installed configuration information synchronization script; In this embodiment, the configuration information synchronization script can transmit the latest configuration information of the master PLC controller obtained earlier to the new master PLC controller to complete the synchronization configuration when the master PLC controller fails. This ensures that there is no information gap in configuration when the new master PLC controller takes over the interaction with the remote unit, thereby achieving seamless interaction with the remote unit.

[0082] The step of synchronously sending the configuration information obtained from the faulty primary PLC controller to the new primary PLC controller also includes: The monitoring device, based on the configuration information synchronization script, synchronously sends the configuration information obtained from the faulty primary PLC controller to the new primary PLC controller, and at the same time intervals, obtains the configuration information output by the communication interface of the new primary PLC controller.

[0083] In this embodiment, after the monitoring device sends the configuration information to the new master PLC controller based on the configuration information synchronization script, it also needs to repeatedly obtain the configuration information output by the communication interface of the new master PLC controller at intervals of the specified time intervals. This enables the acquisition of the real-time configuration information of the new master PLC controller, thus preparing the data foundation for configuration information synchronization for subsequent switching.

[0084] S400: After the new master PLC controller completes its configuration based on the received configuration information, it interacts with the remote unit.

[0085] Specifically, the new master PLC controller interacts with the remote unit, including: If the new master PLC controller is the second PLC controller, then the communication interface of the new master PLC controller outputs a high-level output signal, the first intermediate relay is opened, the second intermediate relay is closed, the new master PLC controller is connected to the remote unit, and the new master PLC controller interacts with the remote unit. If the new master PLC controller is the first PLC controller, then the communication interface of the new master PLC controller outputs a high-level output signal, the first intermediate relay closes, the second intermediate relay opens, the new master PLC controller connects to the remote unit, and the new master PLC controller interacts with the remote unit.

[0086] In this embodiment, the interaction process between the new primary PLC controller and the remote unit is similar to that between the primary PLC controller and the remote unit, and will not be described again here.

[0087] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A control method based on a PLC redundant control device, characterized in that, The PLC redundancy control device includes a first PLC controller, a second PLC controller, a first intermediate relay, a second intermediate relay, a remote unit, a network interconnection device, and a monitoring device; The digital output interface of the first PLC controller is connected to the digital input interface of the second PLC controller through the first intermediate relay; The digital output interface of the second PLC controller is connected to the digital input interface of the first PLC controller through the second intermediate relay; The communication interface of the first PLC controller is connected to the remote unit through the first intermediate relay; the communication interface of the second PLC controller is connected to the remote unit through the second intermediate relay. The Ethernet interface of the first PLC controller is connected to the network interconnection device via a network cable, and the Ethernet interface of the second PLC controller is connected to the network interconnection device via a network cable. The network interconnection device is connected to the monitoring device; The method includes: The primary PLC controller and the backup PLC controller are determined, wherein the primary PLC controller is either the first PLC controller or the second PLC controller, and the backup PLC controller is either the second PLC controller or the first PLC controller. The main PLC controller interacts with the remote unit; the monitoring device monitors the main PLC controller and acquires the configuration information output by the communication interface of the main PLC controller at preset time intervals. When the primary PLC controller fails, the backup PLC controller switches to the new primary PLC controller, the monitoring device switches to monitor the new primary PLC controller, and synchronously sends the configuration information obtained from the failed primary PLC controller to the new primary PLC controller. After the new master PLC controller completes its configuration based on the received configuration information, it interacts with the remote unit.

2. The method according to claim 1, characterized in that, The determination of the primary PLC controller and the backup PLC controller includes: The first PLC controller receives input signals from its digital input interface, while the second PLC controller receives input signals from its digital input interface. If the first PLC controller does not receive an input signal from its digital input interface within a preset time, the first PLC controller outputs a high-level output signal through its digital output interface, the first intermediate relay closes, and the first PLC controller becomes the master PLC controller; if the second PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, the second intermediate relay opens, and the second PLC controller becomes the backup PLC controller. If the second PLC controller does not receive an input signal from its digital input interface within a preset time, the second PLC controller outputs a high-level output signal through its digital output interface, the second intermediate relay closes, and the second PLC controller becomes the master PLC controller; if the first PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, the first intermediate relay opens, and the first PLC controller becomes the backup PLC controller.

3. The method according to claim 1, characterized in that, When the primary PLC controller fails, the backup PLC controller switches to the new primary PLC controller, including: If the main PLC controller is the first PLC controller and the main PLC controller fails, the digital output interface of the main PLC controller stops outputting signals, and the first intermediate relay is disconnected. After the backup PLC controller fails to receive an input signal from its digital input interface within a preset time, it outputs a high-level output signal through its digital output interface, the second intermediate relay closes, and the backup PLC controller switches to the new master PLC controller. After the primary PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, and the primary PLC controller switches to a new backup PLC controller. And / or, if the primary PLC controller is a secondary PLC controller and when the primary PLC controller malfunctions, the digital output interface of the primary PLC controller stops outputting signals, and the second intermediate relay is disconnected; After the backup PLC controller fails to receive an input signal from its digital input interface within a preset time, it outputs a high-level output signal through its digital output interface, the first intermediate relay closes, and the backup PLC controller switches to the new master PLC controller. After the primary PLC controller receives the corresponding high-level input signal through its digital input interface, its digital output interface stops outputting signals, and the primary PLC controller switches to a new backup PLC controller.

4. The method according to claim 1, characterized in that, The remote unit includes a remote input / output unit and a remote interaction unit; The communication interface of the first PLC controller is connected to the remote input / output unit through the first intermediate relay; the communication interface of the second PLC controller is connected to the remote input / output unit through the second intermediate relay. The communication interface of the first PLC controller is also connected to the remote interaction unit through the first intermediate relay; the communication interface of the second PLC controller is also connected to the remote interaction unit through the second intermediate relay.

5. The method according to claim 4, characterized in that, The interaction between the main PLC controller and the remote unit includes: If the main PLC controller is the first PLC controller, then the communication interface of the main PLC controller outputs a high-level output signal, the first intermediate relay closes, the second intermediate relay opens, the main PLC controller connects to the remote unit, and the main PLC controller interacts with the remote unit. If the primary PLC controller is a secondary PLC controller, then the communication interface of the primary PLC controller outputs a high-level output signal, the first intermediate relay is disconnected, the second intermediate relay is closed, the primary PLC controller is connected to the remote unit, and the primary PLC controller interacts with the remote unit.

6. The method according to claim 4, characterized in that, The new master PLC controller interacts with the remote unit, including: If the new master PLC controller is the second PLC controller, then the communication interface of the new master PLC controller outputs a high-level output signal, the first intermediate relay is opened, the second intermediate relay is closed, the new master PLC controller is connected to the remote unit, and the new master PLC controller interacts with the remote unit. If the new master PLC controller is the first PLC controller, then the communication interface of the new master PLC controller outputs a high-level output signal, the first intermediate relay closes, the second intermediate relay opens, the new master PLC controller connects to the remote unit, and the new master PLC controller interacts with the remote unit.

7. The method according to claim 1, characterized in that, The monitoring equipment is pre-installed with a network address switching script; When the primary PLC controller fails, the monitoring device switches to monitoring the new primary PLC controller, including: When the main PLC controller malfunctions, the main PLC controller stops sending communication signals to the monitoring device; If the monitoring device fails to receive a communication signal from the primary PLC controller within a preset time, it will monitor the new primary PLC controller after establishing a connection with it based on the network address switching script.

8. The method according to claim 1, characterized in that, The monitoring equipment is pre-loaded with a configuration information synchronization script; The step of synchronously sending the configuration information obtained from the faulty primary PLC controller to the new primary PLC controller also includes: The monitoring device, based on the configuration information synchronization script, synchronously sends the configuration information obtained from the faulty primary PLC controller to the new primary PLC controller, and at the same time intervals, obtains the configuration information output by the communication interface of the new primary PLC controller.

9. The method according to claim 1, characterized in that, The network interconnection device is an industrial switch; And / or, the monitoring device is a monitoring host computer; And / or, the remote input / output unit includes a plurality of remote input / output sub-units connected in parallel.

10. The method according to claim 1, characterized in that, Both the first PLC controller and the second PLC controller are S7-200 PLC controllers; And / or, the remote interaction unit is a human-computer interaction touchscreen.

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