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The Mechatronics Challenge of Big Things That Move

The Mechatronics Challenge of Big Things That Move

Every so often you run into someone whose childhood dreams of a particular avocation have come true, and you think that the universe at least has the potential to be a pretty cool place.

For Craig Breckenridge, the idea of the universe being a pretty cool place holds a double meaning. Not only did the kid who fell in love with astronomy grow up to study structural and mechanical design, but he got to work at a company that designs the world's largest telescopes.

Breckenridge's company Dynamic Structures of Coquitlam, B.C., Canada has a diverse list of projects encompassing scientific items like large-scale telescopes to amusement park thrill rides, and other steel structures. As drawing office manager for the company, supervising the production of models and drawings for the company's clients, he's happy. (The company also works on bridges, mills and any industrial structure made of steel.)

That's not to say designing such huge steel structures or "big things that move," as he and his co-workers often refer to them, doesn't have its challenges. In fact, the challenges are as big as the projects themselves. "We're used to complex geometry and working with machinery within structures," he says.

The latest project, for which Dynamic Structures was awarded Autodesk's Inventor of the Month award in March, is destined to be the world's largest telescope. The company is responsible for designing and building everything except the optics and instrumentation.

The telescope is expected to go online in either Armazones, Chile, or Mauna Kea, Hawaii in 2018. The telescope will be 50m (164 ft) tall and have an on-ground diameter of 63.5m (208 ft). The dome expected to house the telescope will have an outside radius of 33m (108 ft). The enclosure's weight: 1,700 tons. The project was designed for Dynamic Structure's client, Thirty Meter Telescope (TMT), an organization based at the California Institute of Technology, which is sharing funding along with the National Science Foundation and the Association of Canadian Universities for Research in Astronomy.

If there is a general design philosophy within Dynamic Structures, Breckenridge says, "It's the KISS principle (Keep It Simple, Stupid). We try to be thorough and practical, not just in engineering but in fabrication and construction as well. When someone comes up with a new idea, we shouldn't have to struggle to figure out how to make it work. It shouldn't be complicated."

In order to design such a structure, Breckenridge says the company starts by designing the overall structure and then working all the way down to the holes the bolts fit into. "That's the great thing about a digital model - it will have all that information. There are more than structural concerns. The actuators and the motors for everything within the telescope have to be in the right place. It's basic geometry."

While there are only three major moving pieces - the base, the shutter and the cap - that doesn't even begin to cover the design elements. The whole shebang is broken down into what Breckenridge describes as 40 "codes," or areas. Those are in turn broken down further into "sub-codes," or substructures, and there are subassemblies within those. "You can isolate the codes and look at the ribs, the insulation, the walkways or even the azimuth bogey, the wheels that support the building," he says. In Inventor, separate codes can be checked out for work by different design engineers. Breckenridge's professional responsibilities are the scheduling to ensure there are no conflicts.

In any mechatronics project, small or large, the design challenges revolve around making sure important elements don't conflict or collide with one another. The same stands true here as well. "There will be four cranes inside the telescope, one of which is 20 tons, to pick up instruments and place them on the telescope," Breckenridge says. "Some have adaptive optics that correct for atmospheric interface, or detect different wavelengths of radiation, such as ultraviolet or infrared."

There are more mundane considerations as well. "Some guy has to do maintenance throughout the building. How does he get his tools up there to repair something? And everything has to be designed to be shipped in traditional 40-foot containers," says Breckenridge, estimating it'll take some 270 containers to ship everything.

The TMT is not the first Dynamic Structures has designed using Inventor, Breckenridge says. The company used Inventor 9 version in their design of the Atacama Cosmology Telescope (ACT), at a 17,000-ft elevation in northern Chile. "We use several simulation and analysis tools, such as Adams and Ansys," says Breckenridge. "But as Autodesk has improved the analysis within Inventor, and added other plug-ins, we're starting to use those tools more."

Before the ACT project, Dynamic Structures designed the Keck telescope on Mauna Kea using manual drafting tools. The advantage of using digital prototyping tools was clear. "We had between 40 and 60 percent fewer rebuilds when we moved to the computerized systems. With the Atacama telescope, we were able to fully assemble it, test it and then dismantle it and ship it to Chile. There is a much higher comfort level with digital prototyping that you just can't get from drafting," says Breckenridge. Sound advice from someone who seems to know how the universe works.


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