While it’s true that the mechanical engineering field is full of talented designers, more often than not, nature trumps our best efforts. Consider the tuna fish.
A tuna can cruise at about 60 mph, turn 180°, and then accelerate to about 22 mph in less than two lengths of its own body.
That’s why the developers at Boston Engineering started with a tuna when they designed an underwater robot for the US Navy. The company’s GhostSwimmer is modeled on a 40-inch catch pulled from waters off the coast of Gloucester, Mass. The team brought the specimen into the lab, scanned it, and replicated its shape in their CAD system.
The resulting robot retained the seaworthy profile of the tuna, and boasts a propulsion system, a single oscillating foil, appropriately placed fins, and a finely tuned muscular and sensory control system.
The technology makes the robotic tuna (technically called an “autonomous unmanned underwater vehicle”) efficient at a variety of speeds, unlike a traditional thruster propulsion system, which is usually optimized to work at just a single velocity.
How might the US Navy use the GhostSwimmer? One example might involve seeking out mines in shallow waters, like those found in harbors or along shorelines or in rivers.
Surfacing: Sometimes, nature doesn’t follow easy geometric formulas – and PTC Creo can help with that.
“If you think of a simple surface as a arc of constant radius, a tuna profile changes along the length as it does along the width,” says Will Ober, mechanical engineer. “If you took a cross section, you’d see it doesn’t produce an easily and mathematically predictable profile.”
So designers on the GhostSwimmer project use PTC Creo Interactive Surface Design Extension (ISDX). Often, PTC Creo ISDX is used to build attractive consumer products that look and feel good. But for biomimicry, it’s for much more than aesthetics. The software combines parametric modeling with the flexibility of freeform surfaces. It allows designers to build curves in multiple planes simultaneously. Then, they can easily add surfaces between curves and modify them until they get just the right shape.
Simulation: As you might guess, robot motion needs to be simulated to ensure the model can handle friction, loads, etc. At Boston Engineering, Ober says that the PTC tools provide the exact level of simulation they need.
Unlike other analysis tools, which need to have the model loaded and often simplified before testing, PTC simulation tools are easily available in the CAD system. In fact, Ober says he saves an hour every time he runs a simulation because he doesn’t have to set it up in another app.
“We don’t need an ANSYS-level tool, and simulation tools in other CAD packages weren’t adequate” says Ober. “In PTC Creo, we can run the simulation as we design and make modifications in the same place.”
Data management: The GhostSwimmer is packed with parts. Despite its compact size, it’s a large assembly. With PTC Windchill, CAD and other product data are managed in a repository that connects with PTC Creo. By controlling and automating product development processes, the software prevents confusion about designs, where they’re used, when they were last updated, etc.
For example, PTC Windchill noticeably helps the team at Boston Engineering during the beginning of the design cycle.
“When we start a new project, we pick up and build on an old project,” says Ober. “Before we used PTC Windchill, when we were managing data in the file system, we would risk losing work all the time. Nobody could keep track of it all. The result is that a new project might take weeks to assemble. Now it takes a few minutes.”
PTC solutions are there from project proposal to testing. Here are just a few more benefits and results for Boston Engineering:
And of course, the best benefit of all: Safer rivers and harbors with fewer human casualties. It’s all thanks to Boston Engineering, PTC, and that a 40-inch marvel of nature caught near Gloucester.