Chapter 2: Establishment of system reliability model and redundancy design.
Chapter 2: Establishment of system reliability model and redundancy design.
2. 1 overview
2.2 Reliability model
2.3 Problems that should be paid attention to when establishing reliability model
2.4 Redundancy design
Chapter 2: Establishment of system reliability model and redundancy design.
2. 1 overview
System reliability model refers to system reliability structural model (also called reliability block diagram) and corresponding reliability mathematical model. The so-called reliability structure model refers to the functional logical relationship between the units of the system from the perspective of reliability, which is represented by block diagrams. This relationship is described by mathematics, which is the mathematical model of reliability.
Establishing system reliability model is one of the important work items of reliability engineering. It is an important basis and means for reliability index prediction, distribution, reliability analysis, evaluation, weighing and optimization design. The establishment of system reliability model should be carried out in the early stage of system development. With the development and design changes, the system reliability model should be improved and revised.
The reliability model of the system is divided into basic reliability model and task reliability model.
The basic reliability model includes reliability block diagram and corresponding reliability mathematical model. The basic reliability model is a series model, including those units with redundant or alternative working modes, which are processed in series to estimate the maintenance and logistics support requirements caused by products and their components. The detailed procedure of the basic reliability model should reach the analysis level specified by the product in order to obtain the available information. Moreover, the failure rate data can be used as the basis for considering the requirements of product design for maintenance and logistics support at this level.
Mission reliability model includes reliability block diagram and corresponding mathematical model. The task reliability model should be able to describe the expected use of each unit of the product in the process of completing the task. Units used for redundancy or replacement should be reflected in the model as parallel structures or similar structures suitable for specific task stages and task ranges. The mission reliability model has a complex structure, which is used to estimate the probability that the product will complete the specified function during the task execution. The product unit name symbols used in the mission reliability model should be consistent with those used in the basic reliability model.
Establishing the system reliability model has the following functions and significance:
1) Establishing the system reliability model is an important work item of reliability engineering, and it is also one of the necessary work items stipulated in the reliability assurance outline.
2) Establishing the system reliability model is the basic work for the allocation and prediction of reliability index and maintainability index.
3) Establishing the system reliability model is a tool for reliability analysis, estimation and evaluation.
4) The establishment of system reliability model is the primary task of weighing the best scheme and optimizing system design.
5) Establishing the system reliability model is one of the important measures of reliability design. Such as redundant design.
2.2 Reliability Model -548 Note: This section is mostly graphic, not posted, only posted;
2.2. The failure of1unit will lead to the failure of the whole system, and a series model should be established for this system.
Reliability parallel model
Only when all the units that make up the system fail, the system will fail. A reliability parallel model is established for this kind of system.
2.2.3 (m, n) parallel model
This model, also called voting system model, is a parallel structure composed of m subsystems with the same reliability. Only when n units work normally can the system work normally.
Reliability mixed model
Several series models and parallel models are combined to form a hybrid model.
2.2.5 Simple collateral model
Only one of several units that make up the product needs to work, and when this unit fails, it is connected to another unit through the fault monitoring conversion device, which is the bypass mode.
2.2.6 Establishment of complex reliability model
For a complex structural model, if it is a simple series-parallel or parallel-series hybrid structure, its modeling and mathematical model calculation are relatively simple. It is difficult to transform the series-parallel structure model into a simple model, and other methods are needed to analyze it. Commonly used methods include Brin truth method, probability expansion analysis method, Bayesian method and so on. The application of Bayesian method in complex structural model analysis is introduced with specific examples. As shown in figure 2.8.
2.3 Problems that should be paid attention to when establishing reliability model
2.3. 1 Each unit in the reliability model block diagram only represents one functional unit.
2.3.2 The reliability model block diagram should be different from the electrical chlorine wiring diagram. As shown in figure 2. 10a, it is an LC parallel oscillation circuit. Failure of the coil L or the capacitor C will lead to circuit failure. Therefore, although it is parallel, it should be a series model according to the reliability block diagram, as shown in Figure 2. 10b.
2.3.3 Establish a model according to the failure mode; For example, two capacitors are connected in parallel to complete the filtering function. If the open circuit failure of capacitor is the main mode, its reliability model is a parallel structure model. If the short-circuit failure of capacitor is the main mode, its reliability model is series structure model.
(a) Circuit (b) Open circuit fault structural model (c) Short circuit fault structural model
Figure 2. 1 1 shunt capacitor and its reliability block diagram
2.3.4 The block diagram and mathematical model of the reliability structure model should be coordinated with the system block diagram, schematic diagram and engineering drawing, and the input-output relationship is consistent and changes with it.
2.3.5 The block diagram of the model should be expanded layer by layer from top to bottom after the lowest layer is determined, and the mathematical model relationship should be determined layer by layer. Examples of establishing reliability structural model and mathematical model are given in the appendix, see Appendix A 1 and Appendix A2.
2.3.6 When establishing the reliability block diagram, the system function should be determined. The reliability block diagram of each unit in the same working schematic diagram is not necessarily the same, because the completed tasks and functions are different. A reliability structure model should be established for each function of the multiplex system. If the system requires that all tasks should be guaranteed, then the task reliability model of the system is the series structure of all task models.
2.4 Redundancy design
When the unit reliability of the system can't meet the requirements of the system, a design method is adopted, especially for the system that can't be maintained or needs non-stop maintenance, especially for the system that performs special tasks and has very high security requirements. It is one of the effective methods to improve the reliability of system tasks.
Redundant systems can be divided into working redundant systems and non-working redundant systems. The working redundancy system is that all units work in parallel on the same machine, such as the reliability parallel model in 2.2.2 and the (m, n) parallel model in 2.2.3 of this standard. In the non-working redundant system, only one unit is in the non-execution state, and the other units are in the standby state. When the working unit fails, the standby units are replaced one by one by the switch until all the units fail and the system fails. In addition, the non-working redundant system also has the standby of execution state, which is called hot standby, and its structural model is approximately equivalent to the parallel model in engineering.
In engineering, redundancy design should pay attention to the following issues:
2.4. 1 When carrying out redundant design, the reliability, volume, weight and cost should be weighed and optimized.
2.4.2 When carrying out redundant design, not all the units that make up the system need to be designed redundantly, but those units with weak reliability that have a vital impact on task execution and security should be selected for redundant design.
2.4.3 In order to improve the mission reliability of the system, we can make the following trade-offs: If we improve the reliability of the unit components, we can have the same reliability level as the redundant design. At the same time, it is easy to improve the level of components of the unit, and the cost is not high, so it is necessary to improve the reliability level of components of the unit, that is, to choose highly reliable components, which is especially important for long-term communication products, and often shows the superiority of selecting highly reliable components in a long working time.
2.4.4 In the design, the redundancy of alternative functions makes it possible to complete units with different functions. Once one unit fails, other units can switch functions and replace them. For mobile communication products, real-time dynamic reconfiguration redundancy design can also be adopted. For example, the transmission signal covers the stations through the respiratory throughput, so that users can receive uninterrupted signals, which is similar to the hardware redundancy design. The calculation formula is as follows
What is redundant system redundancy refers to the repeated configuration of some components of the system. When the system fails, redundant components intervene and undertake the work of the failed components, thus reducing the failure time of the system.
What is a PLC redundant system? PLC redundancy can be divided into software redundancy and hardware redundancy. Hardware redundancy requires hardware models and different connection methods, but there is no special requirement for software. Programmable logic controller (PLC) is a widely used controller in industrial automation system. With the development of technology, the establishment of redundant system further improves the reliability of the system. At present, there are many classification methods of redundancy, and there are two redundancy methods of PLC, namely soft redundancy and hard redundancy. Siemens provides soft redundancy and hard redundancy solutions. The reliability based on hard redundancy is high, but the cost of building the system is also high. Soft redundancy based on S7300 or S7400 is a low-cost and high-reliability scheme. At present, soft redundancy system has been widely used in industrial control projects such as metallurgy, transportation, electric power, chemical industry and sewage treatment. However, the efficiency of soft redundancy has not been systematically studied. The redundant structure of hard redundant system ensures the reliability of the system at any time, for example, all important components are redundant. This includes redundant CPU, power module and synchronization module for redundant CPU communication. According to the needs of specific automation control process, redundant client server, redundant communication medium, redundant interface module IM 153-2, etc. It can also be configured. Hard redundancy system can be: 1. Smooth master-slave switching II. Automatic event synchronization 3. Integrated error identification and error location function 4. The system can be modified during operation 5. Similar to the online programming of standard CPU 6. When downloading a program, only a single CPU is considered, and the program can be automatically copied to another CPU. 7.CPU automatically re-enters after repair. 8. During the execution, all parts can be replaced. Soft redundancy principle: when the system is executed, two CPUs start execution at the same time, but during normal execution, only the main CPU issues control commands, and the standby CPU detects the state of the main CPU and records the commands issued by the main CPU, so that when the main CPU fails, it can continue the actual state at that time and issue execution commands instead of the main CPU. When the IM 1532 module communicating with the main CPU is enabled, the main CPU can access the I/O module. When a specific fault occurs in the system, the system can switch between main and standby, and the standby station will take over the main station to continue execution.
Why does ABPLC need redundant system? For safety reasons, it is usually used in equipment with large downtime loss.
This kind of equipment needs redundant systems, one of which is broken, and the second system is eager to replace the broken parts without stopping the machine.
Which brands of plc can be used as redundant systems Siemens S400, Siemens Bo Tu 1500, AB Controllogic 5000 series, and large-scale PLCs generally have this function. It seems that the domestic Hollysys LK series also has it.
What memory card can be used for the CPU of S7 400 redundant system?
What is the redundancy of. DLL files in the system? Redundant files are system backup files. The formats are DLL and deb.
The dynamic link library DLL file is an executable file, which allows programs to enjoy the code and other resources necessary to perform special tasks. The DLL file provided by Windows contains many functions and resources that allow Windows-based programs to run in the Windows environment.
DLL file is a dynamic link library file, which is an executable file, allowing programs to use the code and other resources needed to perform special tasks. The DLL file provided by Windows contains many functions and resources that allow Windows-based programs to run in the Windows environment.
A DLL is usually a file with a DLL extension, but it can also be an EXE or other extension. They provide code, data or functions to programs running under the Windows operating system. The program can open, enable, query, disable and close the driver according to the instructions in the DLL file.
The full name of DLL is dynamic link library, which is called "dynamic link file" in Chinese. In the Windows operating system, DLL is very important for the execution of the program, because the program must be linked to the DLL file when it is executed, so that it can be executed correctly. And some DLL files can be used by many programs. So programmers can use DLL files to make the program not too big. But when more and more programs are installed, there will be more and more DLL files. If useless DLL files are not deleted when deleting programs, it will cause a burden to the system over time.
DLL is a dynamic link library. Some benefits of using dynamic link libraries are:
1. Multiple applications * * * share code and data: For example, each component of Office software has a similar appearance and function, which is realized by * * * sharing a dynamic link library.
2. When a hook program filters system messages, it must use a dynamic link library.
3. DLL divides a large application into several small modules in a natural way, which is beneficial to the division of labor and cooperation of team members. And each module can be upgraded independently. If a member of the team develops a set of practical routines, he can put them in a dynamic link library for other members of the team to use.
4. In order to realize the internationalization of applications, it is often necessary to use dynamic link libraries. Using dynamic link libraries, you can store information about specific countries and languages. Use different dynamic link libraries for different versions. When using AppWizard to generate applications, we can specify the language of source files, which is achieved by providing different dynamic link libraries.
VC++, C++ Builder and Delphi can all write DLL files. The above version of Visual basic can also write a special DLL, namely ActiveX DLL.
DLL is not an independent program, it is a part of the program and can only be called by the program to which it belongs. Users cannot and do not need to open it.
Whether Bo Tu software can configure Siemens redundancy system depends on which version. Bo Tu software is the trend of software after Siemens, that is, Siemens will use this software in the future (Siemens S- 1200, S7- 1500, S7-300, S7-400). Explain a little: Siemens 200 is a product acquired by Siemens and should not be integrated into Bo Tu software, and it seems that Siemens will be eliminated. Title: What SIMATIC Manager software can do and should do all Bo Tu software, emphasizing the latest version. TIA 10.5 is dedicated to 1200, which is a trial production. Others should be explained according to its software. I hope I can help you.
What is N+ 1 redundant power supply system? You mean the UPS system? It's an N+ 1 parallel machine, one is a redundant backup, and the other is broken and can be made up. Usually the load is shared equally.
How does Siemens 4 14 redundant system judge which cpu is executing and how does the controller communicate with the switch? You also need 443- 1, win redundancy requires redundancy authorization, and if win is a server, winserver authorization is required. If many files exceed 5 12, you need file authorization.