Thread Content
1 Overview Generally speaking, system simulation can be understood as an integrated science for studying the characteristics of a system that already exists or does not yet exist but is under development. In cases where the actual system does not exist, or exists but cannot be studied directly on the existing system, it is necessary to develop a system model that reflects the characteristics of the system while meeting the requirements for its study. Research on the issues of interest is then carried out using this system model, in order to uncover the inherent properties, operating patterns, and relationships between subsystems of both existing and future systems, as well as to make predictions about the future. System simulation is an interdisciplinary science that is based on modeling theory, computational methods, and evaluation theory as its fundamental principles, and is supported by related technologies such as computer technology, network technology, graphic and image technology, multimedia technology, software engineering, information processing, automatic control, and systems engineering. The application of simulation technology is generally manifested in the form of a simulation system. 2 Development of simulation technology. Over more than half a century, simulation technology has evolved from being used to study simple systems to becoming a powerful tool for analyzing complex systems. It has gone through roughly three stages: 1) The development stage. At the end of World War II, research on artillery control and flight control dynamics contributed to the advancement of simulation technology, and the first general-purpose electronic analog computer was developed in the 1940s. From the late 1950s to the 1960s, research on the attitude and orbital dynamics of missiles and spacecraft, the widespread use of simulation technology in the Apollo moon landing program and nuclear power plants, as well as the use of the first hybrid computer system in the late 1950s for simulating intercontinental missiles, all contributed to the development of simulation technology. This is the development stage of simulation technology. 2) Mature stage: Driven by demand, in the mid-1970s, simulation technology not only developed rapidly in ** certain fields but also expanded to many other areas. During this period, products such as flight training simulators for training pilots of civil airliners and military aircraft, as well as simulation systems for training operators of complex industrial systems, came into existence. Successively, some specialized companies engaged in the production of simulation equipment and simulation systems emerged. Companies such as the GSEs in the United States, E&S, ABB, and Dynetics have brought simulation technology to the industrial stage. This marks the entry of simulation technology into a mature stage. At the end of the 1970s, changes in the international political landscape created new opportunities for the development of simulation technology. On the one hand, as the Cold War situation eased around the world, countries **shifted their investment focus to their own economic development and began to drastically reduce their conventional military forces. Large-scale military exercises are constrained not only by the political environment but also by economic conditions. In contrast, modern warfare places increasing emphasis on training troops in joint operations capabilities as well as the use of strategic and tactical methods ； On the other hand, modern weapon systems are becoming increasingly complex, the cost of developing them is rising, the development cycle is getting longer, and the time required to train operators to use them is also increasing. It is therefore necessary to find more effective ways and methods for developing new weapon systems, and to establish a system in which decision-makers, developers, and users work together in coordination to develop weapons. This will help to reduce the development time and costs associated with weapon systems, and this is an issue that military forces around the world are striving to address. Simulation technology provides an effective technical approach to solving these problems. Similarly, as technology advances, industrial production equipment becomes increasingly complex, and higher levels of skill are required to operate it, facing the same problems as weapon systems. Such technical demands have driven the rapid development of simulation technology. 3) Advanced stage: The early 1980s marked a new advanced stage in the development of simulation technology, characterized by the SIMNET (Simulators Network) research program developed and implemented jointly by the U.S. Defense Advanced Research Projects Agency (DARPA) and the U.S. Army, as well as the establishment of advanced semi-physical simulation laboratories by the U.S. military services. The SIMNET project was the prototype and beginning of distributed interactive simulation. By the 1990s, various departments successively developed distributed interactive simulation systems, parallel distributed interactive simulation systems, and aggregate-level simulation systems. The vast majority of these simulation systems are developed to meet the specific needs of a particular field; they are not interoperable with one another, and their applications as well as their components cannot be reused in new simulation projects or developments. With the development of the defense industry and industrial systems, the systems to be simulated are becoming increasingly complex and larger in scale. If various application departments develop large-scale simulation systems from scratch based on their own needs, it results in low efficiency, significant waste of financial and human resources, and it is difficult to ensure the accuracy and reliability of the models and simulation results. To achieve better sharing of information and resources and to promote interoperability and reusability of simulation systems, by the 1990s, developed countries led by the United States began to develop simulation technology toward a high-level architecture for simulation (HLA), building on foundations such as distributed interactive simulation, advanced parallel distributed interactive simulation, and aggregate-level simulation. HLA is an advanced protocol that facilitates interoperability among all types of simulations and the reuse of simulation model components. 3 Applications of simulation technology: With the development of simulation technology, its applications have become more diverse and comprehensive. Initially, simulation technology was applied as an auxiliary tool for testing actual systems, and later it was used for training purposes. Today, the applications of simulation systems include various aspects such as system concept research, feasibility studies of systems, system analysis and design, system development, system testing and evaluation, training for system operators, system forecasting, as well as the use and maintenance of systems. Its application areas have expanded to the military as well as various important sectors related to the national economy. 3.1 **Field 3.1.1 Development of weapons and equipment** Simulation technology, in the process of developing weapons and equipment, enables the use of simulation systems to assess the rationality of the design concepts as well as the tactical and technical performance of weapon systems before the start of any new development project. This helps to avoid issues with inappropriate design choices during the actual development process, reduces the development timeline, and supports technical evaluations, system upgrades, and the creation of prototypes, thereby allowing for an improvement in the tactical performance of weapons and equipment at a lower cost. Various users (including the departments responsible for weapon development, procurement, training, and **operation) can utilize a variety of simulation techniques in a synthetic environment as needed to conduct exercises, training, and tests, in order to assess the performance, tactical deployment, and logistical support of existing and under-development weapons and equipment. Now, in the process of developing and producing weapons and equipment, simulation systems are required as essential components. 3.1.2 **Training: The distributed simulation system uses networking technology to connect simulators, computer-generated forces, and other devices located in various places into a single entity, creating a virtual battlefield environment that can be integrated in terms of time and space. Participants can interact with each other freely. In this way, tasks that were previously mainly carried out through field exercises can now be performed using computers, simulators, and artificially created virtual environments. Further development of technology will also connect units conducting field exercises with such simulators for training purposes. Simulators are used to create dynamic and intuitive environments, along with simulated terrain, smoke, and the weapons of \"enemies,\" enabling troops to conduct highly realistic **drills**. 3.1.3 Advanced Concepts and **Requirement Analysis: In terms of advanced concepts and **requirement analysis (such as experiments using new concepts and advanced technologies), the impact of integrated technology can be assessed for future **actions regarding aspects such as regulations, training, command personnel development, organization, equipment, and soldier development, through simulation and the use of experiences from real troops. 3.2 Industrial Sector Just as in other sectors, driven by corresponding demands, and due to the complexity and large scale of industrial systems, simulation technology is widely used across various industries for safety and economic reasons. It plays an increasingly important role in the conceptual research and system requirement analysis phases prior to the construction of large and complex engineering systems (projects). In the power industry, as the capacity of individual generator sets increases and systems become more complex, higher demands are placed on their economic operation and safe production. Simulation systems represent the best way to achieve these objectives. The simulation system can optimize the operation process and train operators. The power plant simulation system has become essential equipment for the construction and operation of power plants. The operation of nuclear power plants must be safe, and the technical competence and skills of operators are prerequisites for ensuring safe operation. Simulation training systems are effective means for improving the competence and skills of operators. In today’s world of economic globalization, trade liberalization, and social informatization, and amid the accelerating pace of technological innovation, the business strategies of the manufacturing industry have undergone significant changes. How to develop products that users will accept in the shortest possible time and at the lowest cost has become the focus of competition in today’s market. Virtual manufacturing is an effective technical approach to solving this key issue. Virtual manufacturing is a simulated product manufacturing process that utilizes modeling techniques, supported by computers and high-speed networks, as well as collaborative work among computer clusters. It enables product design, process planning, manufacturing, performance analysis, quality inspection, and the management and control of various processes within a company, all through 3D models and animations. Virtual manufacturing is a process of simulating existing or future manufacturing activities; the processes carried out are simulated, and the products produced are also simulated. Simulation technology will play an important role in manufacturing enterprises. 3.3 Other Application Areas While being used to develop combat training systems and support industrial processes for weapon systems, the application of simulation technology is continuously expanding into various fields such as transportation, education, communications, society, economics, and entertainment. In recent years, domestic software platforms for traffic simulation have been developed that can describe the characteristics and quality of traffic flows, enabling preliminary evaluations of traffic planning, traffic control design, and traffic infrastructure construction plans. In the project of diverting water from the Yellow River to Shanxi, a system-wide operation simulation system was established. The engineering design was verified using a simulation system; significant issues affecting operation in the existing design were identified, and the optimal mode for scheduling operations was sought. In the field of medical simulation, biological models and 3D visual models of the human body have been developed, providing powerful tools for in-depth research on the mechanisms of human life and for telemedicine applications. To meet the needs of research on large-capacity, high-speed communication networks, extensive research has been conducted on communication simulation methods and software, providing important analysis and validation tools for improving the performance of communication networks and optimizing network designs. Furthermore, simulation technology and virtual reality technology also show great prospects for development in the entertainment industry. 4 Current Situation at Home and Abroad and Prospects 4.1 Current Situation Abroad Developed countries, represented by the United States, attach great importance to the development and application of simulation technology. For over a decade, the U.S. Department of Defense has listed simulation and modeling technologies as key defense technologies. The 1997 \"U.S. Defense Technology Program\" listed modeling and simulation as an important technology among the four pillars for enhancing **capabilities (combat readiness, modernization, force structure, and support capabilities). The U.S. armed forces have successively developed an infrared guidance semi-physical simulation system to meet the needs of simulating infrared imaging-guided weapons. To meet the needs of radar homing guidance, the millimeter-wave semi-physical simulation system MSS-2 is the largest and most advanced RF simulation system in the world today. It can meet the requirements for millimeter-wave precision guidance simulation of surface-to-air missiles. Currently, it is used for semi-physical simulation of the guidance heads for the Patriot PAC-2 and PAC-3 systems. Composite guidance represents a significant advancement in precision strike weapons and equipment, and the simulation technologies used to support such weapons have become one of the most challenging areas in simulation today. In 1995, the United States developed a co-aperture millimeter-wave and infrared dual-mode guidance semi-physical simulation system. In 1983, the Defense Advanced Research Projects Agency (DARPA) of the U.S. Department of Defense and the U.S. Army jointly developed the SIMNET research program. This program aimed to connect simulators of ground vehicles located in various sites – such as tanks and armored vehicles – through computer networks, in order to plan and train for various complex missions. It was designed to demonstrate and verify the feasibility of real-time networked human-in-the-loop combat simulation and exercises, with the ultimate goal of reducing training costs, implementing combat scenarios, enhancing training safety, and minimizing negative impacts on the environment. By 1989, when SIMNET was finally handed over to the U.S. Army, it had connected 9 operational simulation nodes (5 in the United States and 4 in Europe) and 2 development simulation nodes, as well as approximately 250 sets of ground vehicle simulators and aircraft flight simulators. As a training system, SIMNET is still in use today. The completion of the SIMNET project marked the entry of simulation technology into the stage of distributed interactive simulation, laying the foundation for its further development. Thereafter, in the 1990s, the United States developed systems based on HLA, such as JADS (Joint Advanced Distributed Simulation), JWARS (Joint Warfare System), HLA-based application systems, JSIMS (Joint Simulation System), and ALSP application systems. Europe also attaches great importance to research in simulation technology. The North Atlantic Treaty Organization (NATO) established corresponding research institutions to conduct follow-up studies, in line with the Distributed Interactive Simulation Working Group in the United States, and formulated plans for modeling and simulation. In industries other than specific applications, such as in the United States and other Western countries, simulation technology and its applications are at the world’s leading level, including aircraft simulators, vehicle transportation simulation, power systems, and simulation systems for the petrochemical industry. 4.2 Domestic Situation Through the efforts of several five-year plans, simulation technology in our country has developed rapidly and achieved breakthrough results. In the defense industry, various types of semi-physical simulation systems have been developed. The application of half-realistic simulation systems has played a significant role in the development, production, use, and maintenance of products in the defense industry. Simulation systems for command, operations, and training, as well as semi-physical simulation laboratories, have been established in **this field. The application of simulation technology provides effective tools for the command, combat, and training of our military forces, making significant contributions to the modernization of our army. In the field of advanced distributed interactive simulation technology, China has initially developed a comprehensive distributed interactive simulation system 14J. This system is an open support environment that incorporates virtual reality technology and enables distributed interactive simulation; it supports the design, operation, and evaluation of complex systems, and is already being applied in the development of actual systems. In the civil industry, our country has independently developed and produced U51 systems such as simulation systems for large power plants in the electric power sector (200MW, 300MW, 600MW), transportation simulation systems, and petrochemical process simulation systems. Thanks to the efforts made during the \"Seventh Five-Year Plan\", \"Eighth Five-Year Plan\" and \"Ninth Five-Year Plan\" periods, simulation technology in our country has made great progress. It has reached an internationally advanced level in certain aspects. However, the overall technical level, especially at the application level, still lags behind that of developed countries; further efforts are needed to accelerate the development of simulation technology in order to narrow this gap. The excellent properties and significant benefits of system simulation technology may make it a comprehensive technology that will receive special attention and vigorous development in the future. The simulation system will be applied throughout the entire process of human production practices, which helps to avoid decision-making mistakes, predict potential problems, and thus achieve the goals of preventing failures and ensuring safe control. 4.3 Outlook Modeling theories and methods remain key research areas driving the advancement of simulation technology. It is the foundation for the sustainable development of system simulation. Developed countries such as the United States have always given top priority to research on modeling theories and methods in the field of simulation. Furthermore, both weapon systems and industrial systems are moving toward larger scale and greater complexity, which necessitates research on theories and methods to support the modeling of such complex large-scale systems. Simulation systems will be an essential tool for supporting the study of the entire life cycle of various complex large-scale systems. For large and complex industrial systems, it is necessary to assess their safety and design and implement them with safety in mind. Simulation systems are effective tools for assessing their safety, so the credibility of the simulation systems themselves becomes very important. Theoretically establishing an evaluation system for simulation systems, along with the corresponding methods and tools, is an important research direction for promoting the application of simulation technology. The development of advanced distributed simulation technology may, in the 21st century, integrate personnel and resources from various application fields into a large-scale simulation environment. It will break down the boundaries between various fields, enabling people to study and analyze proposed ideas and tasks in a simulated environment. The development of modern modeling techniques, computer technology, network technology, virtual reality technology, and other similar technologies provides strong technical support for creating such cross-industry simulation systems with virtual environments. The creation of such a simulation system will help people solve more complex problems, having a greater impact on the economy or society. Efforts should be made to achieve this goal. The key technology supporting this development is distributed collaboration technology. It can help people in different geographical locations to share and exchange data, information, knowledge, and behavioral status, carry out specific tasks, and facilitate interdisciplinary information sharing as well as decision-support services. The conversion technologies required for virtual worlds represent another challenging research direction for developing cross-industry virtual environment simulation systems. Simulation technology is one of the highly challenging emerging technologies, and it will be widely applied in **, industry, biology, medicine, human behavior, ecological environment, agriculture and forestry, animal husbandry, urban planning, space exploration, and other fields. In the 21st century, its development will have a profound impact on the economy, society, and people’s attitudes. 5 Conclusion As a comprehensive science, simulation will continue to develop rapidly as technologies in related fields advance, while also expanding the scope of its applications and playing a greater role in national defense and economic development. However, as a comprehensive technical discipline, simulation technology still has many theoretical and technical issues that require further in-depth research and exploration. Our country should vigorously carry out theoretical research and applied technical research on simulation technology, in order to narrow the technological gap with advanced developed countries as soon as possible. The development of system simulation technology will surely further enhance the level of science and technology in our country.