B.2. USE OF SIMULATION IN RESEARCH AND DESIGN OF COMPLEX SYSTEMS
One of the problems of modern science and technology is the development and implementation in the design practice of the newest methods for studying the characteristics of complex information-control and information-computing systems of various levels (for example, automated systems of scientific research and complex tests, design automation systems, process control systems , as well as integrated control systems, computer systems, complexes and networks, information systems, digital integrated services networks, etc.). When designing complex systems and their subsystems, numerous problems arise that require the evaluation of quantitative and qualitative regularities of the processes of the functioning of such systems, the carrying out of structural algorithmic and parametric synthesis [4, 11, 37, 45].
Features of system development
The systems of computer science and computer technology considered in this textbook, automated information processing and control systems, information systems belong to the class of large systems, the design, implementation, operation and evolution stages of which are currently impossible without the use of various types of modeling. At all the stages listed above, for complex types of different levels, it is necessary to take into account the following features: the complexity of the structure and the stochastic relationships between the elements, the ambiguity of the behavior algorithms under different conditions, the large number of parameters and variables, the incompleteness and indeterminacy of the initial information, the diversity and the probabilistic nature of environmental influences and etc. The limited possibilities for experimental research of large systems make it urgent to develop a methodology for their modeling , which would allow to present in a suitable form the processes of the functioning of systems, a description of the course of these processes using mathematical models, obtaining the results of experiments with models for assessing the characteristics of the objects under study. And at different stages of creation and use of the listed systems for the whole variety of subsystems included in them, applying the modeling method pursues specific goals, and the effectiveness of the method depends on how competently the developer uses the modeling capabilities .
Regardless of the partitioning of a particular complex system into subsystems, when designing each of them, it is necessary to perform external design (macro design) and internal design (microprojection). Since at these stages the developer pursues different goals, both the methods used and the modeling tools can differ significantly.
At the macroprojection stage, a generalized model of the process of functioning of a complex system should be developed, allowing the developer to receive answers to questions about the effectiveness of various control strategies for the object when it interacts with the external environment. The stage of external design can be broken down into analysis and synthesis. In the analysis, they study the control object, build a model of environmental influences, determine the criteria for assessing effectiveness, the available resources, the necessary restrictions. The ultimate goal of the analysis stage is the construction of a control object model to evaluate its characteristics. At synthesis at a stage of external designing problems of a choice of strategy of management are solved on the basis of model of object of modeling, that is the complex system.
At the microprojection stage, models are developed to create efficient subsystems. And the methods used and the modeling tools depend on what specific subsystems are being developed: information, mathematical, technical, software, etc.
Features of using models
The choice of the modeling method and the necessary detailing of the models essentially depend on the stage of development of the complex system [34, 37, 46]. At the inspection stage of a management object, for example, an industrial enterprise, and the development of a technical task for the design of an automated control system, the models are mainly descriptive and aim to provide the most complete information in a compact form about the object that the system developer needs.
At the stages of development of technical and working projects of systems, the models of individual subsystems are detailed, and the simulation serves to solve specific design problems, that is, the choice of the optimal variant for a given criterion under given constraints from the set of admissible ones. Therefore, mainly at these stages of designing complex systems, models are used for synthesis purposes [10, 18, 37].
The purpose of modeling at the stage of implementation and operation of complex systems is the playback of possible situations for making informed and forward-looking decisions on the management of the object. Simulation (simulation) is also widely used in the training and training of personnel of automated control systems, computer systems and networks, information systems in various fields. In this case, the simulation is business-like. The model, which is usually implemented on a computer, reproduces the behavior of the controlled object and the external environment, and people at certain points in time make decisions on the management of the object.
ASIOU are systems that evolve as the object of management evolves, new controls appear, etc. Therefore, when predicting the development of complex systems, the role of modeling is very high, since this is the only opportunity to answer numerous questions about the ways for the further effective development of the system and the choice of the most optimal.