Model-based design passes muster for defense system
The development of aerospace and defense systems presents unique challenges. The first challenge is managing their extraordinary scale and complexity. Frequently, these projects are systems of systems, requiring integration of disparate dedicated elements.
Next, low production volume means that nonrecurring engineering costs are carefully scrutinized. One-time costs for research, design and development cannot be distributed over thousands or millions of units.
Finally, testing these systems can be difficult, costly and unsafe. For example, commercial and military satellites cannot be fully tested on the ground, and conducting flight tests on new aircraft is both expensive and hazardous.
Aerospace and defense organizations have long used modeling and simulation to address these challenges. Simulation technologies, including commercial tools such as Simulink, have evolved to support engineers throughout the design, development and test cycles.
Early in the design cycle, simulations are used to understand and analyze system behavior. As the functional and performance requirements of systems have evolved, so too have simulation and analysis capabilities.
Many organizations still use custom Fortran-based models in their design processes. Custom environments, while effective for their original task, can be difficult platforms on which to add modeling capabilities.
That dynamic has prompted the Organizations are looking to model-based techniques to ease the burden of standards compliance industry to turn to commercial-off-the-shelf (COTS) simulation pack-ages. An example of this evolution is the addition of discrete event simulation to Simulink. NASA and TriVector Services recently used the capabilities to analyze the impact of communication latencies on the Ares I rocket.
Having benefited from model-based design’s utility in simulation, verification and production implementation, organizations are looking to model-based techniques to ease the burden of compliance with industry standards and enable integration testing via simulation on multi-organizational programs.
High-integrity programs requiring compliance with industry standards such as DO-178B (guidelines for determining whether software will perform safely in an airborne environment) present unique challenges. The increased burdens of testing and artifact generation significantly increase cost.
Model-based design helps engineers achieve certification to safety standards by supporting requirement traceability, verification and documentation. Those capabilities span multiple design stages. For example, requirements linked to models are inserted as comments in generated code. Qualification kits, available for several verification tools, can reduce the amount of manual review needed.
It is also increasingly common for organizations to adopt model-based design on large programs spanning multiple organizations. Doing so allows system-level performance to be assessed and integration issues to be uncovered much earlier in the design process. When detailed models from multiple organizations are combined, resulting models can contain hundreds of thousands of blocks. Modeling tools, such as Simulink, have evolved to meet such challenges with improved support for large-scale modeling, including support for composite models from other model files and support for signal buses.
Modeling standards are also becoming important for multi-organizational programs. Much as coding standards were adopted to facilitate team development and sharing of source code, modeling standards are being developed to support collaboration at the model level.
For example, the “Orion Guidance, Navigation and Control [GN&C] Matlab and Simulink Standards” document describes the modeling standards and guidelines that the Orion Crew Exploration Vehicle flight dynamics team used for GN&C algorithm development. The standards provide guidelines for aspects of the GN&C models—including stylistic rules, modeling tool selection and configuration settings—that affect model readability as well as the generated code.
As model-based design evolves, it is enabling a diverse and expanding group of organizations to improve efficiency, increase reuse and meet the challenges of developing aerospace and defense systems.
About the author
Matt Behr is aerospace and defense industry marketing manager at MathWorks.
This article was originally published in EE Times’ special digital issue entitled: “Military/Aerospace, Electronics enables reliable systems”.
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