System Requirements Analysis & Modeling

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WHAT IS A MODEL?
*A model is a physical, mathematical, or logical representation of a system entity, phenomenon, or process. *A simulation is the implementation of a model over time.
*A simulation brings a model to life and shows how a particular object or phenomenon will behave. -Useful for testing, analysis or training where real-world systems or concepts can be represented by a model. *Modeling and simulation (M&S) provides virtual duplication of products and processes -Represents those products or processes in readily available and operationally valid environments. *Use of models and simulations can reduce the cost and risk of life cycle activities. WHY USE MODELING?

*Modeling and simulation have become very important tools across all acquisition-cycle phases and all applications: requirements definition; program management; design and engineering; efficient test planning; result prediction; supplement to actual test and evaluation; manufacturing; and logistics support. *Four major benefits; cost savings, accelerated schedule, improved product quality and cost avoidance. M&S is now capable of prototyping full systems, networks, interconnecting multiple systems and their simulators so that simulation technology is moving in every direction conceivable. CLASSES OF MODELS & SIMULATIONS

*Virtual simulations represent systems both physically and electronically. Examples are: - Aircraft trainers, the Navy’s Battle Force Tactical Trainer, Close Combat Tactical Trainer, and built-in training. *Constructive simulations represent a system and its employment. They include: - Computer models, analytic tools, mockups, IDEF, Flow Diagrams, and Computer-Aided Design/ Manufacturing (CAD/CAM). * Live simulations are simulated operations with real operators and real equipment. Examples are: -Fire drills, operational tests, and initial production run with soft tooling. VIRTUAL SIMULATION

*Virtual simulations put the human-in-the-loop.
*The operator’s physical interface with the system is duplicated, and the simulated system is made to perform as if it were the real system. *The operator environment looks, feels, and behaves like the real thing. *The more advanced version of this is the virtual prototype

-Allows the individual to interface with a virtual mockup operating in a realistic computer-generated environment. *A virtual prototype is a computer-based simulation of a system or subsystem with a degree of functional realism that is comparable to that of a physical prototype. CONSTRUCTIVE SIMULATIONS

* The purpose of systems engineering is to develop descriptions of system solutions. Accordingly, constructive simulations are important products in all key system engineering tasks and activities. * Of special interest to the systems engineer are Computer- Aided Engineering (CAE) tools. * Computer-aided tools can allow more in-depth and complete analysis of system requirements early in design. * Communication is improved because data can be disseminated rapidly and concurrently * Design changes can be incorporated and distributed expeditiously. * Key computer-aided engineering tools are CAD, CAE, CAM, Continuous Acquisition and Life Cycle Support, and Computer-Aided Systems Engineering. CAD

*CAD tools are used to describe the product digitally to facilitate and support design decisions. *Used to lay out systems or components for sizing, positioning, and space allocating using two or three dimensional displays. *Uses three-dimensional “solid” models to ensure assemblies, surfaces, intersections, interfaces, etc., are clearly defined. *Most CAD tools automatically generate isometric and exploded views of detailed dimensional and assembly drawings, and determine surface areas, volumes, weights, moments of inertia, centers of gravity, etc. *CAD tools can develop 3D models of facilities, operator consoles, maintenance workstations, etc., for evaluating man-machine interfaces. *CAD tools are available in...
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