Understanding Advanced System Integration Labs: Simulation-Centric System Integration

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“This paper examines how successful aerospace and defense organizations are changing their processes to apply simulation-based testing, evaluation, and system integration in a manner that changes the competitive playing field within the industry. ”

Understanding Advanced System Integration Labs: Simulation-Centric System Integration

Modeling and simulation have become key tools for the development of advanced aerospace and defense vehicles. Simulation techniques and tools have been adopted at numerous stages in an advanced development process and enable design teams to develop their products faster, cheaper, and better.

As the use of simulation has gained momentum and become a necessary core competency for any serious aerospace and defense organization, proliferation of the use of electronic systems has also emerged in parallel. An estimated 80% of new system capability and complexity is inserted through the use and expanded role of electronic systems. Advanced embedded electronic systems collect and share more data to obtain greater operational awareness. This operational awareness provides greater power efficiency, higher performance (using various measures), improved safety, and much more. In order to efficiently implement a vehicle electronic system architecture able to collect and share this massive amount of operational data, the system makes increasing use of vehicle networks. The resulting vehicle design includes tightly networked electronic systems dependent on time and event synchronous interoperability.

In order to meet the challenges of these complex and highly interoperable systems, the System Integration Lab (SIL) has become a key component in the development process. The SIL is a risk reduction facility where the complete vehicle, including software and hardware, can be integrated, tested and evaluated for both stand alone functionality and interoperability prior to building the first production prototype. The SIL provides a vehicle test facility that is a cross between a pure simulation and the final system.

The SIL is a simulation-based tool with a proven track record of providing immense cost savings. Performing system integration on a highly complex aerospace or defense vehicle is a very costly activity with great potential for schedule delays and cost overruns.

Applied Dynamics has worked closely over the past several decades with leading aerospace and defense companies to define and implement a highly effective simulation-centric development pro-cess. Simulation-centric development is a rapidly emerging approach for collaborative simulation-based design, testing, and integration that provides greater control over the development program, reduces program risk, and has enabled those who embrace the concepts to obtain competitive advantage in the aerospace and defense market.

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Executive SummaryIn order to meet the

challenges of these complex and highly interoperable

systems, the System Integration Lab (SIL) has

become a key component in the development process.

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“Prior to the use of simulation and modeling, the “build and

break” approach to system design was very slow and

costly.”

Adding Simulation to the Design Process

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In a traditional system development approach the development process begins by defining require-ments contained in a requirements document. The requirements document provides a tool for managing the design of a complex system. From the requirements document, a textual design specification is created. Ideally, the design specification provides complete documentation of all aspects of the system design. The system design will evolve over the duration of the design phase of the project. As the design specification becomes increasingly detailed, the design of each subsystem begins to impose requirements for how that subsystem interfaces with other subsystems in the vehicle. These imposed interface requirements are fed back and folded into the requirements document.

Requirements Definition Design Specification Prototyping & Integration

A Traditional System Development Approach

Prior to the use of simulation and modeling the development of a vehicle required prototypes be iteratively designed, built, tested, and re-designed. This “build and break” approach to system design was very slow and costly.

In an effort to achieve more cost effective development programs, modeling and simulation emerged as a method to reduce the number of iterations. Simulation provided a way to math-ematically model each subsystem, or component within each subsystem, and iterate the math-ematical representation to produce a superior design. Simulation became the preferred technique for finding an optimal design for each subsystem. Upon completing the simulation and modeling

IntroductionThis paper examines how successful aerospace and defense organizations are changing their pro-cesses to apply simulation-based testing, evaluation, and system integration in a manner that changes the competitive playing field within the industry. Historically, aerospace and defense companies have been organized with “stovepipes” between different functional groups. These stovepipes are being eliminated and cross organizational processes are driving competitive ad-vantage. Although space-technology-oriented illustrations are used throughout this paper, these techniques are being applied in all areas of the aerospace and defense industry including military modernization, and commercial aerospace.

“The resulting vehicle design includes tightly networked

electronic systems, depen-dent on time and event syn-

chronous interoperability, and providing an immense level of

system complexity.

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As simulation repeatedly demonstrated value through its ability to reduce development cost and provide superior design, simulation tools became more capable and more widely used. The vari-ous segments of the simulation tool industry became increasingly competitive as aerospace and defense companies made the shift away from in-house developed simulation tools toward best-in-class commercial tools. As the use of simulation gained momentum and became a necessary core competency for any serious aerospace and defense organization, proliferation of the use of electronic systems also emerged in parallel.

An estimated 80% of new system capability and complexity is now inserted through the use and expanded role of electronic systems. Advanced embedded electronic systems collect and share more data to obtain greater operational awareness. This operational awareness is used to provide greater power efficiency, higher performance (using various measures), improved safety, and much more. In order to efficiently implement a vehicle electronic system architecture able to collection and share this massive amount of operational data, the system makes increasing use of vehicle networks. The resulting vehicle design includes tightly networked electronic systems, de-pendent on time and event synchronous interoperability, and providing an immense level of system complexity. This increased complexity has resulted in two trends.

The first trend is the move away from the textual design specification. Simulation is now used to obtain an optimal design using a range of mathematical techniques. Today simulation models and solid models provide a digital design specification for the vehicle. Feeding the design back into a textual requirements document is a needless and onerous task. Efficient development programs are abandoning the textual design specification in areas where the design is well-specified through the use of simulation or solid models. The second trend is the increased use of the system integra-tion lab.

Prototyping & Integration

Subsystem Design Spec.

SimulationModel

Requirements Definition

Simulation in the Design Stage

activities the design was documented in the design specification. Although the design continued to be largely textual, the use of simulation and modeling resulted in a better design and enabled the development program to reduce the number of prototypes required to reach the final product.

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The System Integration LabIt is only in recent years that aerospace & defense programs and companies have shown across the board recognition of the importance of the System Integration Lab (SIL) and its role in the success of a vehicle or weapon system program. The SIL has become a required component of any serious defense program. As a result, defense contractors including Northrop Grumman, BAE Systems, Raytheon, General Dynamics, and Lockheed Martin have made recent SIL facility investments.

A SIL is a risk reduction facility where software and hardware can be integrated, tested and evalu-ated for both stand alone functionality and interoperability prior to being fielded or flight tested. The SIL is used to create a vehicle or weapon system test facility that is a cross between a pure simulation and the final system. The SIL uses as many real vehicle subsystems as is technically and economically feasible. Real control units, avionics, navigation systems, mission computers, flight controls, and environmental control systems are connected in the SIL. Real-time simulation is used to provide the functionality of those components of vehicle or weapon system operation that are difficult or costly to bring into a lab such as aerodynamics, six degrees-of-freedom motion, extreme temperatures, and low-gravity conditions.

Electrical Interfaces & Databuses

TCP/IP-basedSimulation Control

PC-basedTest Interface

The System Integration Lab

SimulationModel

SimulationModel

SimulationModel

The SIL enables the vehicle to be tested around the clock, through a range of normal and extreme operating conditions in a very cost effective manner. By connecting real electronic systems across representative electrical and electronic interfaces to realistic representations of the vehicle, nearly all aspects of the vehicle complexity can be tested and exercised using production vehicle elec-tronic systems.

A well-designed SIL also provides a platform for future technology insertion. New technology can be fully tested and certified in the SIL before it is ever installed in the vehicle for flight test.

The SIL is a simulation-based tool with a proven track record of providing immense cost savings. However, performing system integration on a highly complex system is a very costly activity with great potential for schedule delays and cost overruns. In order to reduce the risk and cost of sys-tem integration those most experienced in the use of a SIL are taking a collaborative approach that starts well before the SIL.

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Efficient, Collaborative IntegrationEarly examples of system integration took the approach of tasking a team to prepare the SIL for production prototype delivery. This job included the development of all simulation models required in the SIL, implementation of those models on real-time simulation computers, and readying the simulation computers to have production electronic system prototypes plugged into the lab. This approach had numerous pitfalls.

The integration team is rarely in a position where they are best qualified to develop the SIL simula-tion models. For example, if Pratt & Whitney Rocketdyne is supplying the rocket engine and the engine controller then Pratt & Whitney Rocketdyne is in the best position to deliver an accurate simulation model for the rocket engine. Historically it was very difficult to convince suppliers and contractors to deliver simulation models to the SIL. The position of the contractors and suppliers was that simulation models were part of their intellectual property and by supplying these models they were at risk of having this intellectual property made available to competitors.

Program managers and lead system integrators have learned through years of experience that in order to have a successful system integration phase of the program, all simulation models required in the SIL must be included in the supply contract deliverables list. There are numerous approaches to ensure supplier intellectual property is protected but if simulation models are not included in the deliverables list then suppliers will resist. The most successful programs have taken things one step further.

“There are numerous approaches to ensure sup-plier intellectual property is

protected”

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As a means of further reducing program risk and enabling the system integration activity to be parallelized, suppliers and design groups are required to deliver a real-time simulation “virtual pro-totype” and any necessary simulation models well-ahead of the production prototype integration activity. These virtual prototypes are intended to behave identically to the final production proto-type but:

• virtual prototypes do NOT need to be built using flight-worthy electronics• virtual prototypes do NOT need to meet the final physical requirements (size, dimensions,

weight)• virtual prototypes do NOT need to meet requirements such as power consumption, noise,

vibration, EMI, etc

Virtual prototypes are delivered for the purpose of spiraling incrementally toward the final fully-integrated SIL. Virtual prototypes enable interoperability issues to be discovered very early in the program at a point where the program cost implications can be minimized. Virtual prototypes are typically built using commercial computer equipment such as PCI-based systems. As stated above, virtual prototypes are “intended to behave identically to the final prototype”. However, it must be recognized that various versions of the virtual prototype will be delivered as the design is finalized, the performance is improved, and interoperability issues are resolved.

By requiring suppliers and design teams to deliver virtual prototypes and simulation models at one or more stages of maturity, the SIL commissioning activity can begin very early in the program. As the program progresses, early virtual prototypes are replaced with increasingly accurate virtual prototypes and finally with production prototypes. This incremental approach to system integra-tion ultimately results in shorter development schedules and reduced program cost.

System Integration LabSimulation Models &

Virtual Prototypes

SimulationModel

Electrical Interfaces & Databuses

TCP/IP-basedSimulation Control

PC-basedTest Interface

SimulationModel

SimulationModel

SimulationModel

Design Groups& Suppliers Collaborative System Integration

“By requiring suppliers and design teams to deliver

simulation models at one or more stages of maturity, the

SIL commissioning activity can begin very early in the

program”

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Virtual System IntegrationWhen the SIL is first commissioned with a collection of virtual prototypes and simulation models the lab is made up of numerous computers executing a collection of simulation models and embed-ded code. The most successful system integration projects have raised the questions:

• “Could I take this collection of simulation models and code, connect them appropriately, and simulate the complete vehicle in non-real-time?”

• “If I could, what benefits would this provide to the system integration project?”

The answer to the first question is yes. The process of building this non-real-time simulation using the simulation models and code from the SIL is referred to as building a “Virtual System Integration Lab (VSIL)” and the use of a VSIL can provide numerous benefits to a development program.

Virtual System Integration Lab

SimulationModel

Developing a VSIL enables the vehicle integrator and suppliers to work in a manner far more effi-cient than the traditional approach to system integration. The VSIL allows program management to place a virtual vehicle on the computer of every development team member early in the program. The VSIL improves the communication of technical requirements and subsystem interfaces and enables suppliers to assess the interoperability of their supplied subsystem earlier in the develop-ment program. In order to successfully implement a VSIL the integrator must take special care to ensure that each supplier’s intellectual property is protected.

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Simulation Centric DevelopmentCombining formal requirements management, simulation-based design, the use of a virtual system integration lab, and virtual prototypes all feeding into a system integration lab creates a highly efficient, collaborative development process known as simulation-centric development. Simula-tion-centric development minimizes the duplication of effort and minimizes overall program risk by enabling design teams and suppliers to test their vehicle subsystem in-context with the rest of the vehicle at various stages of development. As each development group increments the maturity of their design the maturity and complexity of the associated simulation models is incremented. System simulations are shared amongst design teams to provide each team or team member with a VSIL version of the vehicle. The VSIL vehicle can be used to exhaustively test and evaluate each subsystem for stand-alone functionality and interoperability early in the program.

The VSIL provides an ideal tool for training new members of the development team on vehicle architecture, system behavior, and the SIL test language. In addition, the VSIL provides a powerful tool for performing embedded software functional test.

The VSIL also provides a powerful tool for program management. The VSIL can be used to evaluate supplier designs and adherence to system requirements. The VSIL allows program management to assess a supplier’s simulation-based design capability early in the development program. Most critically, the VSIL provides a tool to substantially reduce the load on the SIL facilities. Real-time simulation projects and the complete suite of test cases can be developed away from the expen-sive SIL facilities. The VSIL provides substantial program cost savings and greatly reduces program risk. For a more in-depth discussion on VSIL techniques and technology refer to the whitepaper “System Integration Labs – Dramatic Cost Reduction using a VSIL”.

System Integration Lab

Electrical Interfaces & Databuses

TCP/IP-basedSimulation Control

PC-basedTest Interface

SimulationModel

SimulationModel

SimulationModel

Design Groups& Suppliers

VSIL

SimulationModel

Requirements Definition

Efficient Simulation-Centric Development

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Simulation-centric development is a collaborative approach for aerospace and defense vehicle development that is highly dependent on the ability to move simulation models between vari-ous stages of the development program, amongst various suppliers and development program participants, and to various simulation computers platforms. A common, standardized simulation model interface will increase the ease of working with potentially hundreds of simulation models developed by disparate design teams. Although battlefield simulation model standards such as HLA have been successfully developed and adopted industry-wide, to date there is no simulation model portability standard that is appropriate for system integration.

In the early 1990’s the European Space Agency (ESA) recognized the need for a standard to ensure portability between simulation platforms. This initial effort was called SMP1. SMP1 was ultimately limited by the lowest common denominator of the simulation platforms for which it was required to support.

Later the ESA launched the SMP2 initiative with the goal to move beyond the limitations of SMP1 and to define a standard that could be embraced by system integration labs of today and tomor-row. Unfortunately, SMP2 has not been widely embraced. A significant shortcoming of SMP2 is that it only offers an object-oriented interface standard. The object-oriented restriction poses a problem because of the predominance of procedural embedded code and procedural code-based simulation modeling tools such as The MathWorks Simulink. As a result, SMP2 is not actively used in the aerospace and defense industry.

The Rise of a Simulation Model Portability Standard

As designs mature, the VSIL simulation models are transferred to real-time simulation computers and become virtual prototypes. Identical models are used during VSIL testing and virtual prototype development. This approach eliminates duplication of effort, reduces the risk of finding interoper-ability problems in the SIL, and reduces the cost of implementing virtual prototypes.

Once the virtual prototype version of the SIL is integrated, the integration team can begin taking the real-time simulated vehicle through a range of test scenarios. Stand-alone or interoperability problems found during virtual prototype testing are fed back to the appropriate design team(s) al-lowing design changes to be made in a cost-effective manner.

Next, production prototypes are inserted in the SIL as they become available. Because the lab is first commissioned using virtual prototypes, integrating the production prototypes is a simple mat-ter of unplugging the virtual prototype and replacing it with the production prototype.

Simulation-centric development is an approach that minimizes the effort and risk associated with the complete system integration exercise and provides the only cost-effective approach for tack-ling a highly advanced vehicle program.

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Applied Dynamics has work closely with major aerospace and defense companies and organiza-tions including Boeing, Pratt & Whitney Rocketdyne, Raytheon, NASA, U.S. Navy, U.S. Air Force, U.S. Army, General Dynamics, BAE Systems, Rolls-Royce, Honeywell, Gulfstream, and many more to support system integration activities and real-time simulation. Over the past ten years vehicles have become more complex and system integration has become more costly. In an effort to help our customers become increasingly efficient we’ve developed and evolved the ADvantage Frame-work set of tools for simulation-centric development.

The ADvantage Framework supports popular commercial simulation modeling packages (Simulink, SystemBuild, etc), various operating systems & compilers, and commercial-off-the-shelf computer hardware to provide a software toolset that reduces the cost of implementing simulation-centric development. ADvantage enables various simulation model types and embedded software coding languages to be brought together to build a VSIL. As development progresses, ADvantage enables the non-real-time VSIL to be quickly converted to real-time virtual prototypes, and later virtual prototypes to be swapped out with production prototypes. The ADvantage Framework includes a full test environment, a complete suite of test interaction capability, and sophisticated data logging and analysis services.

Tools for Simulation-Centric Development

A simulation model portability standard that meets the needs of the commercial aircraft, military vehicles and weapons systems, and space programs could trigger significant advancements with regard to the industry’s ability to work collaboratively.

Defining a Simulation Model Portability Standard

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The ADvantage Framework has been field-proven on many of the most demanding aerospace & defense programs including Boeing’s 787 Trent jet engine and aircraft braking projects, the Verti-cal Motion Simulator (VMS) at NASA Ames, the Army’s new FCS NLOS-C military ground vehicle development, and Gulfstream’s G550 luxury aircraft integration lab, and has been used to develop subsystems within NASA’s Space Shuttle Program and the International Space Station Program.

For more information on the ADvantage Framework refer to: http://www.adi.com/products_sim.htm