A simulation is an imitation of some real device or state of affairs. Simulation attempts to represent certain features of the behavior of a physical or abstract system by the behavior of another system.
Simulation is used in many contexts, including the modeling of natural systems, and human systems to gain insight into the operation of those systems; and simulation in technology and safety engineering where the goal is to test some real-world practical scenario. Simulation, using a simulator or otherwise experimenting with a fictitious situation can show the eventual real effects of some possible conditions.
Physical and interactive simulation
Physical simulation refers to simulation in which physical objects are substituted for the real thing, these physical objects are often chosen because they are smaller or cheaper, than the actual object or system.
Interactive simulation, which is a special kind of physical simulation, and often referred to as human in the loop simulations, are physical simulations that include humans, such as the model used in a flight simulator.
Simulation in training
Simulation is often used in the training of civilian and military personnel. This usually occurs when it is prohibitively expensive or simply too dangerous to allow trainees to use the real equipment in the real world. In such situations they will spend time learning valuable lessons in a "safe" virtual environment. Often the convenience is to permit mistakes during training for a safety-critical system.
Training simulations typically come in one of four categories:
- "live" simulation (where real people use simulated (or "dummy") equipment in the real world);
- "virtual" simulation (where real people use simulated equipment in a simulated world (or "virtual environment")), or
- "constructive" simulation (where simulated people use simulated equipment in a simulated environment). Constructive simulation is often referred to as "wargaming" since it bears some resemblance to table-top war games in which players command armies of soldiers and equipment which move around a board.
- Role play simulation (where real people take on the persona of a virtual work)
Medical simulators are increasingly being developed and deployed to teach therapeutic and diagnostic procedures to people in the health professions. Simulators have been developed for training procedures ranging from the basics such as blood draw, to laparoscopic surgery and trauma care. Many medical simulators involve a computer connected to a plastic simulation of the relevant anatomy. In others, computer graphics reproduces all visual components and tool handles reproduce haptic aspects of the task. Some contain computer graphics simulations of imagery such as X-ray or other medical images. Some simuluators used in anesthesia training employ a life size mannequin which responds to injected drugs and can be programmed to create simulations of life-threatening emergencies.
A City Simulator is a simulation game of a city.
Main article: Flight simulator
A flight simulator is used to train pilots on the ground. It permits a pilot to crash his simulated "aircraft" without being hurt. Flight simulators are often used to train pilots to operate aircraft in extremely hazardous situations, such as landings with no engines, or complete electrical or hydraulic failures. The most advanced simulators have high-fidelity visual systems and hydraulic motion systems. The simulator is normally cheaper to operate than a real trainer aircraft.
Simulation and games
Main article: Simulation game
Many video games are also simulators, implemented inexpensively. These are sometimes called "sim games". Such games can simulate various aspects of reality, from economics to piloting vehicles, such as flight simulators (described above).
Simulation is an important feature when engineering systems. For example in electrical engineering, delay lines may be used to simulate propagation delay and phase shift caused by an actual transmission line. Similarly, dummy loads may be used to simulate impedance without simulating propagation, and is used in situations where propagation is unwanted. A simulator may imitate only a few of the operations and functions of the unit it simulates. Contrast with: emulate. (Source: Federal Standard 1037C)
Most engineering simulations entail mathematical modeling and computer assisted investigation. There are many cases, however, where mathematical modeling is not reliable. Simulation of fluid dynamics problems often require both mathematical and physical simulations. In these cases the physical models require dynamic similitude.
Computer simulation, has become a useful part of modeling many natural systems in physics, chemistry and biology, and human systems in economics and social science (the computational sociology) as well as in engineering to gain insight into the operation of those systems. A good example of the usefulness of using computers to simulate can be found in the field of network traffic simulation. In such simulations the model behaviour will change each simulation according to the set of initial parameters assumed for the environment. Computer simulations are often considered to be human out of the loop simulations.
Traditionally, the formal modeling of systems has been via a mathematical model, which attempts to find analytical solutions to problems which enables the prediction of the behaviour of the system from a set of parameters and initial conditions. Computer simulation is often used as an adjunct to, or substitution for, modeling systems for which simple closed form analytic solutions are not possible. There are many different types of computer simulation, the common feature they all share is the attempt to generate a sample of representative scenarios for a model in which a complete enumeration of all possible states of the model would be prohibitive or impossible.
It is increasingly common to hear simulations of many kinds referred to as "synthetic environments". This label has been adopted to broaden the definition of "simulation" to encompass virtually any computer-based representation.
Simulation in computer science
In computer science, simulation has an even more a specialized meaning: Alan Turing uses the term "simulation" to refer to what happens when a digital computer runs a state transition table (runs a program) that describes the state transitions, inputs and outputs of a subject discrete-state machine. The computer simulates the subject machine.
In computer programming, a simulator is often used to execute a program that has to run on some inconvenient type of computer. For example, simulators are usually used to debug a microprogram. Since the operation of the computer is simulated, all of the information about the computer's operation is directly available to the programmer, and the speed and execution of the simulation can be varied at will.
Simulators may also be used to interpret fault trees, or test VLSI logic designs before they are constructed. In theoretical computer science the term simulation represents a relation between state transition systems. This is useful in the study of operational semantics.
Simulation in education
Simulations in education are somewhat like training simulations. They focus on specific tasks. In the past,video has been used for teachers and education students to observe, problem solve and role play; however, a more recent use of simulations in education include animated narrative vignettes (ANV). ANVs are cartoon-like video narratives of hypothetical and reality based stories involving classroom teaching and learning. ANVs have been used to assess knowledge, problem solving skills and dispositions of children, pre-service and in-service teachers.
Another form of simulation has been finding favour in business education in recent years. Business simulations that incorporate a dynamic model enables experimentation with business strategies in a risk free environment and provide a useful extension to case study discussions.
- Roger D. Smith: Simulation Article, Encyclopedia of Computer Science, Nature Publishing Group, ISBN 0-333-77879-0.
- Roger D. Smith: "Simulation: The Engine Behind the Virtual World", eMatter, December, 1999.
- Institute for Simulation and Training, University of Central Florida
- Mastering Simulation: Online Course
- Simulation Interoperability Standards Organization
- United States Defense Modeling and Simulation Office
- Bookmarks of Open Source Scientific Codes
- Simulation-An Enabling Technology in Software Engineering
- Imtek Mathematica Supplement (IMS) for open source simulation lectures and packages.ar:محاكاة