SIMULATION BASED DESIGN CENTER (SBDC)
Primer on Virtual Prototyping

Introduction  •  Virtual Prototyping  •  Virtual Reality   •  Levels of Virtual Reality  • 
Benefits of Virtual Prototyping  •  Virtual Prototyping Considerations   • 
Uses of Virtual Prototyping within SBDC

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Introduction
Technology has advanced at an ever-increasing, almost exponential rate. In fact, technology development moves faster than the consumers understanding of the resulting product enhancements. With the widespread utilization of microprocessors, several new spin-off technologies have emerged; these include technologies for internetted nervous system communications, under sea and land fiber optic networks, and customized biological organisms used to eat ocean oil spills.

One of these spin-off technologies is virtual reality, defined as an artificial computer generated environment in which the user has the impression of being part of that environment with the ability to navigate and manipulate objects which have properties and behaviors that reflect real world objects.

Virtual reality technologies have propagated the concept and use of the "virtual prototype," which is a computer based simulation of systems with a degree of functional realism. As an example, virtual prototypes with properly modeled fluid dynamics can be used in designing aircraft, ships and missiles to replace wind tunnel testing, which is a costly and time consuming process. The advent of virtual prototyping has put on notice, the present techniques used in the creation of complex products.

Already, fundamental changes are underway in the development of new products and processes. Several companies have refocused their product development philosophy to incorporate the notion that products must demonstrate their value-added market capability prior to obtaining approval to expend significant resources on its development and production.

Where and how will this be accomplished? For starters, these industries are creating electronic environments that will become the site of future product evaluations. Virtual prototypes will become the means through which the marketing impact of each existing and proposed product will be assessed. Because the virtual prototype is a key ingredient in this new product development philosophy understanding its heritage and future potential is essential for all participants in this new product development paradigm.

Virtual Prototyping
A virtual prototype can be defined as a computer-based simulation of a system or subsystem with a degree of functional realism comparable to a physical prototype. Virtual prototyping is the process of using a virtual prototype, in lieu of a physical prototype, for test and evaluation of specific characteristics of a candidate design.

A virtual prototyping environment is a multi-disciplinary collection of models, simulations and simulators focused on guiding product design from idea to prototype, emphasizing subsystem optimization and integration rather than hardware. In the context of industrial acquisition, a virtual prototyping environment would address engineering design concerns of the developer, process concerns of the manufacturer, logistical concerns of the maintainer, and training and programmatic concerns of the operations.

A new generation of simulations are being developed that enable creation of a variety of realistic synthetic environments that bring operators, developers, scientists, engineers testers and manufacturers together. Virtual prototypes are tested in these simulated operational environments. Once a concept is approved, design and manufacturing tradeoffs will be conducted on the virtual prototype to enhance producibility and eliminate the need for a physical prototype.

Synthetic environments are the internetted simulations that represent activities at a high level of realism. These environments are fundamentally different from the traditional simulations and models known today. They are created by a confederation of computers connected by local and wide area networks and augmented by realistic special effects and accurate behavioral models that allow visualization of, and total immersion into, the environment being simulated. Virtual prototypes are inserted in synthetic environments; these consist of simulations of the components of an actual environment (air, land and/or sea) and are used to assess system capabilities during the new product development process. Once systems are fielded, simulations are used for training, indoctrination and organizational purposes.

The principal challenges of synthetic environments and virtual prototypes include creating environments that are meaningful and realistic to human participants where computers accurately represent human behavior, create environments that accurately describe real-world places, and in connecting globally located sites economically.

Virtual prototypes are an important ingredient to the success of new product development initiatives. Produced today with CAD/CAM tools, they offer tremendous potential for reducing costs, yielding more robust designs, and shortening manufacturing cycle times. Companies are reaping significant benefits from using virtual prototypes and achieving the capabilities desired of new product development. Users are finding physical prototypes are no longer necessary and simulation-based tools enable them to achieve competitive advantage. It is important to note these advantages are being accomplished using existing computer tools at current costs. As the capabilities of these tools grow and costs lessen, companies will have no choice but to use virtual prototypes to compete.

The concept of the "virtual factory" is also part of new product development. A simulated factory could be used to identify designs requiring modification to enhance producibility, determine which processes should be automated, assess the feasibility of dual-use technologies, and calculate surge capability. Research is taking place on the "virtual factory" where the concepts of rapid prototyping, flexible manufacturing, commercial vs. military requirements, and industrial base issues are being explored.

Virtual Reality
Virtual reality (VR) is a subject of enormous curiosity to government, industry and academia. The term is often used interchangeably with a number of related names such as virtual environment, telepresence, virtual prototyping, electronic environment, virtual factories, synthetic environments, scientific visualization, cyberspace, etc. Confusion over the definition stems from the vast array of potential customers eager to characterize their product as "virtual." Laying the hype aside, the technology, according to experts in the field, offers great potential in science and engineering research, education, entertainment, design, financial analysis and defense simulation. The operative word is "potential" because most applications are concentrated primarily in the entertainment field where Hollywood views visualization as a locomotive for the future of growth in digital technology and VR.

The term virtual reality is new but much of what we know about personal computing grew directly from Engelbart's Augmentation Research Center (ARC) at the Stanford Research Institute in the l960s where several VR taproots originated. Today, simulation technology has advanced to permit "sensory overload" through all human receptors simultaneously - visual, auditory, haptic and motion interfaces. The term "haptic" refers to any variety of manual interactions with the environment.

Today's systems are extremely complex and must rapidly interact in proper context with many disparate entities. A VR machine is intended to immerse humans into real-time interactions so they may learn, train, test, have fun or understand and optimize processes and systems. The virtual environment could also be selectively constrained by policies, resources, tactics, or strategies to correctly represent the customer issues.

Levels of Virtual Reality
Virtual reality consists of various levels of immersion. The level used in a particular application is determined by various factors. Some of the factors include the audience the virtual world has been developed for, the level of detail within the virtual environment, and the interaction between the user and the environment.

The most basic level of virtual reality is considered to be non-immersive reality. This level generally consists of a large projection system to provide a wide display for a large number of observers. Non-immersive virtual reality is typically used in the design environment for group design reviews. The ability to convey the highly technical information to non-technical personnel is a major advantage and is widely utilized by design firms. This level of virtual reality is currently also used as an excellent training tool for many areas including manufacturing and process control.

The intermediate level of virtual reality is known as semi-immersive reality. This type of virtual reality partially immerses the user within the environment. With this type of immersion the user remains aware of the surrounding real-world environment. The use of stereoscopic visualization devices such as Crystal Eyes 3D stereoscopic glasses, ImmersaDesk and Infinity Wall's are typical with this type of immersion. Semi-immersion is used as a tool to allow large groups to "become a part" of the virtual environment.

The highest level of virtual reality is a fully immersive environment. This type of immersion places the individual into the virtual environment by removing all reference to the surrounding real world. The user has no visual reference to the surrounding real world and becomes an active part of the virtual environment. Full interaction takes place between the user and the objects within the environment. Virtual objects retain the characteristics and behaviors of the real world objects they represent. This type of immersion is typically obtained through the use of a head-mounted display (HMD), BOOM device, or a virtual reality CAVE. The interaction with virtual objects is typically accomplished with a 3D mouse, gloves, or a wand.

Benefits of Virtual Prototyping
There are several benefits associated with the use of virtual prototyping.

• The use of rapid prototyping greatly accelerates the production of new products. Large U.S. manufacturers are using rapid prototyping techniques. Prototypes are a direct link to the production process and can be used to enhance communication with customers and vendors. They can be shown to customers to demonstrate the physical properties of the product and enables agreement on any desired design modifications before beginning tooling or production. Prototypes also can be sent to vendors of complex parts or subassemblies to assist them in developing an accurate quote. Successful implementation of rapid prototyping requires organizational commitment and the application of several key technologies.
• Virtual prototyping can provide a clear, competitive edge to companies who embrace and successfully implement its features. Reduced cycle times provide the opportunity to make new products available in less time and thus permit a company to become a market leader. In addition, companies usually can realize a positive return on their virtual prototyping investment in less than two years.
• Virtual prototypes can be a valuable tool for program managers to use in identifying and managing program risks. Program managers are required to develop new product development strategies and program plans that are event-driven and that explicitly link major contractual commitments and milestone decisions to demonstrated accomplishments in development, testing and initial production. At each milestone decision point, assessments are required of the status of program execution, plans for the next phase, and the rest of the program. Virtual prototypes can be used effectively to measure performance against milestone decision criteria. They can be used to test the system or certain high risk subsystems against certain simulated hazards scenarios, assess the effectiveness of the proposed technology and evaluate the feasibility of the design for producibility. Virtual prototypes can be used also to assess the risks inherent in the degree of concurrency being proposed for a program.
• Virtual prototypes enhance a company's competitiveness by giving it a perceptual edge. Virtual prototypes can assist both the contractor and the program manager in understanding new product concepts and operational impact of new products and systems. More importantly, it provides a means for the engineers to visualize, maybe for the first time, the interactive results of what previously has been represented by two-dimensional tables of data and thousands of complicated equations.
• Virtual prototypes can provide developmental and operational testers with the ability to conduct meaningful evaluations that can aid in the design of the tests performed during each phase of an product development. A virtual prototype that is developed as a scientific visualization in the "concept exploration and development" phase and is enhanced continuously throughout the development process, can provide the test community with the ability to optimize the number of tests that are conducted as well as reduce the time needed to collect required data. Because virtual prototypes exist in a digital world, the tester will have the opportunity to conduct numerous iterations of the same test scenario and aid in the design of tests performed during each phase of the product development process. Substituting a virtual prototype for a physical prototype in all or some portion of the tests which involve destructive testing and fatigue analysis, can allow the tester to "dry run" test scenarios, optimize tests for a physical prototype, determine practical test limitations and in many cases actually conduct additional tests that may not be affordable without virtual prototypes.

Virtual Prototyping Considerations
When the decision has been made to utilize virtual reality technology to assist with solving technical problems, various issues must be considered. One of the primary considerations that determines what and how much to model is the available computing resources. The amount of data to be modeled will directly effect the computer systems ability to generate acceptable frame rates for the virtual world generation. The next consideration that must be addressed is which portion of the environment is to be modeled in high detail. By only modeling in detail the most relevant components of the environment, the available computing power can be utilized to its fullest extent. The development time frame of the environment is directly proportional to the level of inter-activity that is desired. The development of a virtual environment with real world data is a very important component to the creation of a realistic virtual prototype. Typically, special interfaces must be constructed for this task.

Uses of Virtual Prototyping within the Simulation Based Design Center (SBDC)
The Simulation Based Design Center has been using virtual prototyping technologies and techniques in the maritime industry for approximately three years. The extent of this experience includes product model fly-thru visualizations to integrated virtual reality mechanical systems analysis. One application of virtual prototyping technology involved a project to study the feasibility of developing a proposed floating military installation. This installation, called a Mobile Offshore Base (MOB) consists of five separate self-propelled modules joined by a series of hinged connectors. Each of the modules of the MOB measures 300 meters long by 158 meters wide by 76 meters tall. When connected together, the MOB would be approximately one mile long with the ability to land various cargo aircraft. Operating in the open seas, it would partially submerge when on station, providing a stable platform for launching and logistical support of troop deployment, command and control operations, and humanitarian efforts such as disaster relief.

The study consisted of physics-based simulations, visualizations, and analysis of the results. Given its primary mission of logistical supply, operations of the MOB's cargo transfer systems were of particular interest, especially during the heavy wave action that could limit the ability to transfer cargo to and from adjacent supply ships. Cargo ships react to wave action differently than the comparably stable MOB, so knowing their relative motion is critical in determining if the cranes on the MOB can lift cargo containers from ships without the containers swaying too much causing damage, and if vehicles can be driven safely over ramps between ships and the MOB.

The technologies that were utilized on the project consist of the integration of various engineering tools. The CAD data defining the geometry of the MOB and cargo vessels were imported into the Silicon Graphics Onyx Supercomputer in the form of DXF and IGES files from a naval design and modeling system. Simplified forms of the geometry were used to create response amplitude operators (RAO's) in all six degrees of freedom within the WAMIT software program, a multiple wave-body interaction program. The motions and geometric data were both imported into the Advanced Dynamic Analysis of Mechanical Systems (ADAMS) software tool through custom interfaces developed at the SBD Center. This tool provided analysis of the displacements, forces, accelerations, and loads on various components and subsystems. The analysis of the motions generated from the mechanical simulation were then fed into the visual simulation package via a custom interface. The visual simulation of the analysis provided greater understanding of the overall motion and operation of the MOB, allowing viewers to discern details often not readily apparent in tabular printouts.

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