A digital control system

Abstract

The present application discloses a digital control system, which solves the problem of long loop control cycle of digital control system under large-scale configuration. The digital control system includes: a main control module, n communication modules and multiple I / O modules of the same type; n is an integer greater than 1; the main control module is connected to the n communication modules through serial communication; the serial communication between the main control module and each communication module is realized through each built-in field programmable gate array FPGA, and the serial communication is realized based on gigabit serializer / deserializer Serdes technology; each communication module is connected to multiple links working in parallel, each link is connected to multiple I / O modules, and each communication module uses polling to manage the communication of each I / O module connected to it.

Description

Technical Field

[0001] The present application relates to the field of automation control technology, and in particular to a digital control system. Background Art

[0002] DCS (Digital Control System) is an automation control system widely used in the industrial field. With its highly integrated digital technology, it realizes the precise monitoring and control of various industrial equipment in large industrial facilities such as nuclear power plants.

[0003] Loop control is a key link in DCS, which covers the complete control process from data (including analog and switch quantities) acquisition, logical operation to command output. The length of the loop control cycle directly reflects the sensitivity and accuracy of DCS control of industrial equipment.

[0004] With the surge in the number of I / O modules, the loop control cycle is forced to be extended, which reduces the real-time performance and control accuracy of DCS. Summary of the invention

[0005] In view of the above problems, the present application provides a DCS to solve the problem of long loop control cycle in large-scale DCS configuration. The specific solution is as follows:

[0006] The present application provides a DCS, comprising: a main control module, n communication modules and a plurality of I / O modules of the same type; n is an integer greater than 1;

[0007] The main control module is connected to n communication modules via serial communication; the serial communication between the main control module and each communication module is realized via their respective built-in field programmable gate arrays FPGA, and the serial communication is realized based on gigabit serializer / deserializer Serdes technology;

[0008] Each communication module is connected to a plurality of links working in parallel, each link is connected to a plurality of the I / O modules, and each communication module manages the communication of the I / O modules connected thereto in a polling manner.

[0009] In a possible implementation, the Gigabit serializer / deserializer (Serdes) technology is implemented by converting electrical signals into optical signals through a small pluggable SFP module and then using optical fiber as a transmission medium.

[0010] In a possible implementation, the main control module and each communication module are both equipped with a built-in error checking and correction ECC module.

[0011] In a possible implementation, the polling mode is an ECC polling mode.

[0012] In a possible implementation, the main control module combines a central processing unit (CPU) with an FPGA, wherein the data acquisition task is executed by the FPGA and the logic operation task is executed by the CPU.

[0013] In a possible implementation, the communication between the communication module and the I / O module is implemented based on the RS485 protocol.

[0014] In a possible implementation, the multiple I / O modules of the same type are n×m×x I / O modules of the same type, each communication module is connected to m links working in parallel, each link is connected to x I / O modules, and m and x are both integers greater than 1.

[0015] In a possible implementation, the n×m×x I / O modules of the same type are n×m×x switch I / O modules, the number of channels of the switch I / O modules is 16 channels, n=8, m=6, x=10;

[0016] Alternatively, the n×m×x I / O modules of the same type are n×m×x analog I / O modules, the analog I / O modules have 8 channels, n=8, m=6, x=10.

[0017] In a possible implementation, the longest communication time of each communication module does not exceed 1 millisecond, the processing cycle of the main control module for logic operations is set to 10 milliseconds, and the communication time of each I / O module is limited to no more than 2 milliseconds.

[0018] In a possible implementation, the DCS is a DCS for a nuclear power plant.

[0019] By means of the above technical solution, the DCS provided by the present application adopts a two-layer network structure to optimize the communication between the main control module and the I / O module. In the first layer, the main control module uses the built-in FPGA and the Gigabit SerDes technology to realize serial communication with n communication modules, ensuring fast and stable communication; in the second layer, the communication module manages the I / O module communication on the parallel link connected to it in a polling manner, effectively avoiding frame conflicts. Thus, the ideal loop control cycle is maintained, and efficient operation can be maintained even in the face of a large number of I / O modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the originals and elements are not necessarily drawn to scale.

[0021] Figure 1A schematic diagram of a DCS loop control flow provided in this application;

[0022] Figure 2 A schematic diagram of the structure of a DCS provided for this application;

[0023] Figure 3 A schematic diagram of the structure of a DCS based on 480 switch I / O modules provided in this application;

[0024] Figure 4 A schematic diagram of the time distribution of a loop control cycle provided in this application;

[0025] Figure 5 A schematic diagram of the structure of a DCS based on 480 analog I / O modules provided in this application. DETAILED DESCRIPTION

[0026] In the following description, in order to ensure the accuracy of the citation and the fluency of reading, the key technical terms, abbreviations or abbreviations involved in the text are summarized and explained as follows:

[0027] DCS: Digital Control System, digital control system;

[0028] I / O: Input / Output, input / output;

[0029] Serdes: Serializer / Deserializer, serializer / deserializer;

[0030] SFP: Small Form-factor Pluggable;

[0031] FPGA: Field-Programmable Gate Array, field programmable gate array;

[0032] CPU: Central Processing Unit, central processing unit;

[0033] ECC: Error Checking and Correcting, error checking and correction;

[0034] RS485: Electronic Industry Association (EIA) Standard RS-485;

[0035] A / D: Analog to Digital, analog / digital conversion;

[0036] AI: Analog Input, analog input;

[0037] TC:Temperature Controller, temperature controller;

[0038] RTD: Resistance Temperature Detector, resistance temperature detector;

[0039] DI: Digital Input, digital input.

[0040] As an automated control system widely used in the industrial field, DCS plays a vital role in large industrial facilities such as nuclear power plants. With highly integrated digital technology, it realizes accurate monitoring and control of various industrial equipment in large industrial facilities, providing a solid foundation for the safe and efficient operation of large industrial facilities.

[0041] Loop control is a key link in DCS, which covers the complete control process from data (including analog and switch quantities) acquisition, logical operation to command output, such as Figure 1 In this control process, DCS can quickly respond to various state changes of industrial equipment and perform fast and accurate calculations and judgments based on preset logic algorithms. Subsequently, DCS will generate corresponding control instructions and accurately control industrial equipment through actuators.

[0042] The length of the loop control cycle directly reflects the sensitivity and accuracy of DCS control over industrial equipment. An efficient DCS can significantly shorten the loop control cycle, thereby ensuring that industrial equipment can maintain optimal operating conditions under various operating conditions, which is of great significance for improving the safety, stability and economy of large industrial facilities such as nuclear power plants. Especially in the face of various emergencies that may occur in nuclear power plants, the sensitive response and accurate control of DCS are particularly important. For example, in emergency situations such as abnormal increase in reactor power or failure of the cooling system, DCS can quickly identify and take corresponding control measures to effectively prevent further deterioration of the situation. This capability not only protects nuclear power plant equipment from damage, but also ensures the safety of nuclear power plant workers and the surrounding public.

[0043] The loop control adopts the mode of cooperation between the main control module and the I / O module, in which the I / O module is responsible for data collection and output, while the main control module is responsible for logical operation. In the traditional DCS, the communication between the main control module and the I / O module adopts a single-layer network structure, that is, all I / O modules share the same bus network, and the main control module obtains data from the I / O module through a polling mechanism. The bus rate is usually maintained in the range of several megabytes per second; the main control module will perform logical operations after obtaining the I / O data, and the processing cycle of this logical operation (referred to as the operation cycle) is generally set to 50 milliseconds. However, with the surge in the number of I / O modules, the main control module will spend a lot of time in the process of polling each I / O module and obtaining data. At this time, the polling cycle of the main control module becomes a key factor restricting the length of the loop control cycle; moreover, with the surge in the number of I / O modules, the originally set 50 millisecond operation cycle may not be guaranteed, which further leads to the extension of the loop control cycle and reduces the real-time performance and control accuracy of the DCS.

[0044] Taking the DCS for nuclear power plants as an example, the typical scale configuration of the DCS for nuclear power plants is about 700 physical points, of which about 500 points are for switching quantities and about 200 points are for analog quantities. The switching quantity I / O modules and analog quantity I / O modules are polled separately. After actual measurement, it is found that the loop control cycle of the analog quantity in the DCS for nuclear power plants can be up to about 500 milliseconds (that is, the loop control cycle of the last analog quantity I / O module polled can be up to about 500 milliseconds), and the loop control cycle of the switching quantity can be up to about 400 milliseconds (that is, the loop control cycle of the last switching quantity I / O module polled can be up to about 400 milliseconds).

[0045] However, when the scale of the DCS for the nuclear power plant is expanded, for example, when its switching quantity is expanded to 7680 points, assuming that the number of channels of the switching quantity I / O module is 16 channels, then the DCS for the nuclear power plant requires a total of 480 switching quantity I / O modules (7680 points / 16 channels=480), and the main control module must obtain data from 480 switching quantity I / O modules in each polling cycle; assuming that the polling cycle of the main control module is 1 millisecond, then the data acquisition part will take up 480 milliseconds (480 modules×1 millisecond / module=480 milliseconds), plus the time occupied by the two parts of logical operation and instruction output, the loop control cycle of the switching quantity will inevitably exceed 500 milliseconds, resulting in a longer loop control cycle of the switching quantity.

[0046] In order to solve the problem of long loop control cycle of traditional DCS under large-scale configuration, an embodiment of the present application provides a DCS. The DCS adopts a two-layer network structure to optimize the communication between the main control module and the I / O module. In the first layer of the network structure, the main control module uses the built-in FPGA and the Gigabit SerDes technology to realize serial communication with n communication modules to ensure fast and stable communication; in the second layer of the network structure, the communication module manages the I / O module communication on the parallel link connected to it in a polling manner to effectively avoid frame conflicts. Thus, the ideal loop control cycle is maintained, and efficient operation can be maintained even in the face of a large number of I / O modules.

[0047] A DCS provided by an embodiment of the present application is described in detail below in conjunction with the accompanying drawings. A person skilled in the art will appreciate that, with the development of technology and the emergence of new scenarios, the technical solution provided by the embodiment of the present application is also applicable to similar technical problems.

[0048] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and need not be used to describe a specific order or sequential order. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, which is only to describe the distinction mode adopted by the objects of the same attributes when describing in the embodiments of the present application. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or equipment comprising a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0049] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and appended claims of the present application, the singular expressions "one", "a kind", "said", "above", "the" and "this" are intended to also include expressions such as "one or more", unless there is a clear contrary indication in the context. It should also be understood that in the embodiments of the present application, "one or more" refers to one, two or more; "and / or" describes the association relationship of associated objects, indicating that three relationships may exist; for example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship.

[0050] See also Figure 2A DCS provided in an embodiment of the present application includes: a main control module, n (n≥2) communication modules, and n×m×x (m≥2, x≥2) I / O modules of the same type (for example, the same are switch I / O modules or the same are analog I / O modules), Figure 2 Just take n=8, m=6, x=10 as an example;

[0051] The main control module is connected to n communication modules via serial communication; the serial communication between the main control module and each communication module is realized through a built-in FPGA, and the serial communication is realized based on Gigabit SerDes technology;

[0052] Each communication module is connected to m links working in parallel, each link is connected to x I / O modules, and each communication module manages the communication of each I / O module connected thereto by polling.

[0053] Next, Figure 2 The working principle of DCS shown is described in detail:

[0054] The communication module is a bridge connecting the main control module and the I / O module, and is responsible for receiving, processing and forwarding data. The main control module exchanges data with n communication modules in sequence through a serial communication link. Serial communication is a data communication method in which data is transmitted in a serial (i.e., one bit after another) manner. It is widely used in digital communication systems due to its advantages such as reducing the number of connecting lines, reducing electromagnetic interference and saving power consumption. In the serial communication link, the main control module, as the initiator and controller of communication, uses the serial communication protocol to send and receive data with each communication module one by one according to a specific timing and format. Each communication module occupies a unique, sequentially arranged position in the serial communication link, ensuring that data can be accurately transmitted between the main control module and each communication module in a predetermined order.

[0055] In terms of the type of communication technology, the network connection between the main control module and each communication module is based on Gigabit Serdes technology. Serdes is the abbreviation of Serializer and Deserializer. It is a high-speed serial communication technology that can convert multiple low-speed parallel signals into high-speed serial signals for transmission, and restore high-speed serial signals to low-speed parallel signals at the receiving end. Gigabit Serdes refers to its support for high-speed serial communication at gigabit rates, ensuring high-speed and low-latency data transmission.

[0056] In a possible implementation, Gigabit SerDes can be implemented by converting electrical signals into optical signals through SFP modules, and then using optical fibers as transmission media. SFP modules are an interface standard for high-speed data transmission. In the embodiment of the present application, SFP modules are used to convert electrical signals generated by Gigabit SerDes into optical signals for long-distance, low-loss transmission through optical fibers, ensuring high speed and stability of data transmission.

[0057] On the hardware platform of communication, both the main controller and the communication module contain FPGA, and both the main controller and the communication module realize serial communication through the built-in FPGA. FPGA is a highly flexible digital circuit that can realize various complex logic functions through programming. It has significant advantages in high parallel computing capability and low latency. Specifically:

[0058] 1) FPGA contains a large number of logic units and programmable connections, allowing multiple computing tasks to be executed simultaneously. It has high parallel computing capabilities, which makes FPGA have significant speed advantages when processing computing-intensive tasks such as image processing and signal processing.

[0059] 2) FPGA's hardware-based architecture allows signals to be transmitted directly in the hardware circuit, greatly reducing processing delays. Compared with software-based processors (such as CPUs), FPGAs can complete data processing within nanoseconds with almost no software-level delays. This low-latency feature gives FPGAs a significant advantage in applications that require high real-time performance.

[0060] Based on this, in the embodiment of the present application, FPGA is used to implement the logic functions of both ends of the communication (i.e., the main control module and the communication module), thereby ensuring the high speed and stability of the communication.

[0061] In summary, the DCS provided in the embodiment of the present application adopts a two-layer network structure to optimize the communication between the main control module and the I / O module. The first layer of the network structure is the communication between the main control module and the communication module, and the second layer of the network structure is the communication between the communication module and the I / O module. In the first layer of the network structure, due to the use of advanced technologies such as Gigabit Serdes and FPGA, the response time of the communication module is relatively short, and the communication process is stable and reliable.

[0062] In a possible implementation, both the main control module and the communication module are built with an ECC module. The ECC module is used to detect and correct errors that may occur during data transmission. The ECC module has a strong error correction capability and can detect and correct errors during data transmission, thereby ensuring the integrity and stability of the data, which is essential for reliable communication between the main control module and the communication module. Moreover, by reducing the number of retransmissions caused by data transmission errors, ECC can indirectly improve communication efficiency.

[0063] It should be noted that the larger the total number n of communication modules is, the larger the DCS scale is. However, the upper limit of the total number n of communication modules is subject to the following factors:

[0064] 1) In serial communication, the signal may be attenuated and interfered during transmission. As the number of communication modules increases, the signal quality may gradually decrease, resulting in an increase in the communication error rate. In order to ensure the reliability and stability of communication, the system needs to set a reasonable upper limit on the number of communication modules to avoid excessive deterioration of signal quality;

[0065] 2) In serial communication, clock synchronization is a key factor in ensuring correct data transmission. As the number of communication modules increases, the difficulty and delay of clock synchronization will also increase accordingly. In order to maintain clock synchronization and reduce delays, the system also needs to limit the number of communication modules.

[0066] Still taking the example that the switching quantity of the DCS for nuclear power plants is 7680 points, the number of channels of the switching quantity I / O module is 16 channels, and the DCS for this nuclear power plant requires a total of 480 switching quantity I / O modules, the total number of communication modules n can be set to 8. At this time: assuming that the longest communication time of each communication module does not exceed 1ms (when both the main control module and the communication module have built-in ECC modules, it means that the time required from the start of data transmission at the sender to the receipt of data at the receiver and the ECC check does not exceed 1ms, which is determined by the processing power of the ECC module and the bandwidth of the communication network). When the data is sent from the main control module and passes through 8 communication modules in sequence, each communication module will introduce a certain communication delay. In the worst case (that is, each communication module reaches its longest communication time), the total time from the data being sent from the main control module to the last communication module receiving the data and returning a response will be the sum of 8 1ms, that is, 8ms. This is the acquisition response time of the last communication module.

[0067] In a possible implementation, the main control module uses a high-performance CPU combined with an FPGA, so that the data acquisition task is run by the FPGA, and the logic operation task is performed by the CPU, and the two do not affect each other, thereby improving the overall performance and stability of the system. Therefore, the processing cycle of the logic operation can be set to 10 milliseconds. When the CPU load is calculated at 50%, the maximum calculation time of the main control module is 15 milliseconds. The calculation process of 15 milliseconds is as follows:

[0068] Since signal transmission and computation are performed in parallel, if the signal arrives just in time to miss the current computation cycle, it is necessary to wait for the next computation cycle to start. Assuming that each computation cycle is 10 milliseconds, and that the system runs at 50% load during this computation cycle, the computation can be completed within 5 milliseconds. Therefore, the maximum time from the arrival of the signal to its participation in the computation and completion is: 10 milliseconds to wait for the next computation cycle plus 5 milliseconds to process within the computation cycle, a total of 15 milliseconds. "

[0069] In the second layer network structure, each communication module is designed with m links, which work in parallel, and x I / O modules are connected to each link. The communication between the communication module and these I / O modules can be realized based on the RS485 protocol, and further, the RS485 communication baud rate can be set to support up to 5Mbps. In order to ensure the high efficiency and accuracy of the communication between the communication module and the I / O module, the communication module adopts a polling method to manage the communication with the I / O module, avoid the occurrence of frame conflicts, and help ensure that each I / O module can communicate with the main control module in a timely and effective manner. This design of parallel link + polling improves the bandwidth and parallel processing capability of data transmission, so that the system can process more I / O requests at the same time. When the communication module has a built-in ECC module, the polling method is specifically ECC polling, which is a data communication polling method combined with ECC technology.

[0070] Still taking the DCS for nuclear power plants with 7680 switching points and 16 channels of switching I / O modules as an example, the DCS for the nuclear power plant requires a total of 480 switching I / O modules, n=8, then m=6, x=10 (8×6×10=480 switching I / O modules) can be set; assuming that the communication time of each I / O module is strictly controlled within the range of no more than 2 milliseconds, then on the same link, the acquisition response time of the last polled I / O module is no more than 20 milliseconds (specifically 2 milliseconds multiplied by the number of I / O modules on the link).

[0071] See also Figure 3 , take the DCS for nuclear power plant with 7680 switching points, the number of channels of the switching I / O module is 16 channels, the DCS for nuclear power plant needs a total of 480 switching I / O modules, n=8, m=6, x=10, the acquisition response time of the last communication module is 8ms, the maximum calculation time of the main control module is 15 milliseconds, and the acquisition response time of the last polled I / O module is no more than 20 milliseconds as an example, then refer to Figure 4 , the loop control cycle consists of the following 7 parts:

[0072] T1: Collection I / O module processing time;

[0073] T2: Transmission time between communication module and acquisition I / O module;

[0074] T3: Transmission time between the main control module and the communication module;

[0075] T4: main control module algorithm operation processing cycle;

[0076] T5: transmission time between main control module and communication module;

[0077] T6: Transmission time between communication module and output I / O module;

[0078] T7: Output I / O module processing time.

[0079] Among them, T1 time includes A / D conversion time, hardware filtering time and firmware operation cycle. The time for collecting different types of signals is shown in Table 1:

[0080] Table 1 - Timetable for different types of signal collection

[0081] Signal Type time Current AI (4-20mA) 120ms TC / RTD 120ms Switching quantity DI 0.5ms

[0082] The maximum T2 time is 20 milliseconds;

[0083] The maximum T3 time is 8 milliseconds × 2 = 16 milliseconds, considering the redundancy of dual communication modules;

[0084] The maximum T4 time is 15 milliseconds;

[0085] The T5 time is the same as the T3 time, with a maximum of 16 milliseconds;

[0086] The T6 time is the same as the T2 time, with a maximum of 20 milliseconds;

[0087] T7 time is the processing time of output I / O modules, 21 milliseconds for analog output and 6 milliseconds for switch output.

[0088] Therefore, the loop control cycle of the switching quantity is:

[0089] T = T1 + T2 + T3 + T4 + T5 + T6 + T7 = 0.5 + 20 + 16 + 15 + 16 + 20 + 6 = 93.5 milliseconds;

[0090] Similarly, see Figure 5, take the analog quantity of the DCS for nuclear power plants as 3840 points, the number of channels of analog I / O modules as 8 channels, the DCS for nuclear power plants requires a total of 480 (3840 points / 8 channels=480) analog I / O modules, n=8, m=6, x=10, the acquisition response time of the last communication module is 8ms, the maximum calculation time of the main control module is 15 milliseconds, and the acquisition response time of the last polled I / O module is no more than 20 milliseconds. For example, the loop control cycle of the analog quantity is:

[0091] T=T1+T2+T3+T4+T5+T6+T7=120+20+16+15+16+20+21=228 milliseconds;

[0092] It can be seen that compared with the traditional single-layer network structure of DCS, the embodiment of the present application can support a larger scale of analog quantities and switch quantities (7680 switch quantities + 3840 analog quantities), and in the case of large-scale, the loop control cycle of the analog quantity is no more than 300 milliseconds, and the loop control cycle of the switch quantity is no more than 100 milliseconds, ensuring that the DCS can still maintain an ideal loop control cycle when facing a large number of I / O modules, and ensuring the accuracy of automatic control.

[0093] When the number of links connected to each communication module is equal and the number of I / O modules connected to each link is also equal, the DCS scale can be maximized under the same loop control cycle. Of course, according to actual design requirements, in any of the above-disclosed DCSs, the number of links connected to each communication module may not be completely equal, and the number of I / O modules connected to each link may not be completely equal.

[0094] In a possible implementation, any one of the DCSs provided above is a DCS for a nuclear power plant.

[0095] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other and will not be described in detail.

[0096] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the embodiments of the present application. Therefore, the embodiments of the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A digital control system, characterized in that: include: A main control module, n communication modules and multiple I / O modules of the same type; n is an integer greater than 1; The main control module is connected to n communication modules via serial communication; the serial communication between the main control module and each communication module is realized through their respective built-in field programmable gate arrays FPGA, each communication module occupies a unique, sequentially arranged position in the serial communication link, and the serial communication is realized based on gigabit serializer / deserializer Serdes technology; Each communication module is connected to a plurality of links working in parallel, each link is connected to a plurality of the I / O modules, and each communication module manages the communication of the I / O modules connected thereto in a polling manner.

2. The digital control system according to claim 1, characterized in that: The Gigabit Serializer / Deserializer (Serdes) technology converts electrical signals into optical signals through a small pluggable SFP module and then uses optical fiber as a transmission medium.

3. The digital control system according to claim 1, characterized in that: The main control module and each communication module have built-in error checking and correction ECC modules.

4. The digital control system according to claim 3, characterized in that: The polling mode is an ECC polling mode.

5. The digital control system according to claim 1, characterized in that: The main control module combines the central processing unit CPU with FPGA, where the data acquisition task is run by FPGA and the logical operation task is executed by CPU.

6. The digital control system according to claim 1, characterized in that: The communication between the communication module and the I / O module is implemented based on the RS485 protocol.

7. The digital control system according to claim 1, characterized in that: The multiple I / O modules of the same type are n×m×x I / O modules of the same type, each communication module is connected to m links working in parallel, each link is connected to x I / O modules, and m and x are both integers greater than 1.

8. The digital control system according to claim 7, characterized in that: The n×m×x I / O modules of the same type are n×m×x switch I / O modules, the number of channels of the switch I / O modules is 16 channels, n=8, m=6, x=10; Alternatively, the n×m×x I / O modules of the same type are n×m×x analog I / O modules, the number of channels of the analog I / O modules is 8, n=8, m=6, x=10.

9. The digital control system according to claim 8, characterized in that: The longest communication time of each communication module does not exceed 1 millisecond, the processing cycle of the main control module for logical operations is set to 10 milliseconds, and the communication time of each I / O module is limited to no more than 2 milliseconds.

10. The digital control system according to any one of claims 1 to 9, characterized in that: The digital control system is a digital control system for nuclear power plants.

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