“There is no way to know how a complex system works until you build it. We need new approaches to design and modeling that enable us to predict those interactions,” he says. AVM aims to capture the interactions and understand how a system works before it is built. “We are building tools to enable a designer to create a 'correct-by-construction' system, meaning that when we build it, it works the way the design predicts, first time.”
Darpa is following the lead of the semiconductor industry, which broke through the complexity barrier decades ago. “The integrated-circuit industry went through this same transformation 30 years ago by building a set of tools called electronic design automation,” Wiedenman says. Using automated tools, “integrated-circuit designers are able to create correct-by-construction designs, to maintain the 24-36-month product cycle that has helped them sustain massive growth.”
AVM begins with the Meta automated tools, which raise the level of abstraction in the design process, in the same way high-level programming languages have for computers. As a software engineer works with applications and not electronic circuits, so the aerospace designer can work with systems and not individual parts.
Meta is “a design flow for cyber-physical systems where hardware and software components are interlinked,” says Janos Sztipanovits, Meta principal investigator at Vanderbilt University. “Physical and computational systems can be co-designed, with trade-offs between hardware and software.”
Using Meta tools, a designer takes component models from a library and assembles them into a system. “A model is a full representation of that component with its surrounding environment: other components, inputs/outputs, heat, vibration, behaviors, etc. It's a meta-model, not just a drawing.”
Capturing every part down to the screws and modeling how they interact would take decades of computation. “We are looking at ways we can intelligently use levels of abstraction so I'm not dealing with every bolt, I'm just looking at how this engine couples to this transmission, couples to this final drive, to this suspension,” he says.
Meta allows designers to evaluate rapidly hundreds of thousands of concepts to meet a requirement. “Traditionally we start out with what we think a vehicle should look like, then iterate around that one particular design, so we're only exploring a very small region of the design space,” says Wiedenman. “We're providing tools that allow you instead to explore the entire design space, without taking decades of computation.”
Models can be parametric, “so we can vary things to create a design,” and progress through different refinement layers as the design becomes more detailed. “I've defined at a high level how these things interact, so I populate a design trade space based on the component options I have,” he says. “Then I use fairly low computationally intensive analysis tools to cull that trade space down to a few designs that need highly complex analysis.”
Using context models to simulate the operating environment, an entire family of concepts can be tested against the requirements. “This allows them to refine their design and further explore the trade space to find where an unusual design might better satisfy the requirements,” Wiedenman says.
Manufacturability feedback during design is a function of the Instant Foundry Adaptive Through Bits (iFAB), which will “receive the design, determine if it can be made, how long it will take and what it will cost,” says Mike Yukish, iFAB principal investigator at Penn State University. “Even for a simple widget there are lots of ways to make it, each with a different cost versus schedule.”