Wednesday, September 15, 2010

Human joysticks and autonomous quadcopters

Aerospace engineering sophomore Duncan Miller spent his summer playing with mini quadcopters (helicopters with four rotors) at NASA Langley Research Center. In this video, he demonstrates the "sense-and-avoid" programming he and his fellow interns wrote and tested. That's Miller with the helmet on.

"In the video," Miller says, "I am acting like a human joystick. The quadrotor is matching my helmet's orientation and altitude. When I look left, the quadrotor yaws to the left. When I look to the right, it follows suit. If I get on my knees, it will lower itself to my eye level again."

How does it do this? Tracking cameras around the room have been programmed to recognize certain reflector dots as objects. In the first part of the video, the students had placed the reflector dots on another quadcopter. In the second part, they're on the helmet. The cameras send a signal to a computer, which sends a signal to the quadcopter about what it needs to avoid.

This was actually quite serious work. In addition to his stint in the helmet, Miller focused on hardware and loop simulations and testing decision algorithms. He and his colleagues set up a functioning autonomous vehicle laboratory. Researchers can now use it to study things like swarming autonomous vehicles and aircraft sense-and-avoid issues, says NASA systems engineer Garry Qualls.

The quadcopters the students used are prototype models of the Parrot AR.Drone "flying video game" that hit the market in early September. (The drones don't come with this autonomous mode, though.)

Wednesday, September 1, 2010

Chasing dust storms and measuring their electrical charges

Understanding how bouncing grains of sand and dust become electrified has applications in climate prediction, electronics manufacturing and Mars exploration.

"You can see clouds forming on the updraft from several miles away and as the gust front moves closer, the world seems to shrink. The horizon gets a little fuzzy. The light dims. And the whole sky turns a very dramatic red.

"In the midst of it, it's essentially a blizzard, except getting sandblasted hurts a whole lot more. Your eyes burn. It's hard to breathe. And you can barely stand against the wind. It's dark enough that if you're driving you'll need to turn your headlights on. After 15 or 20 minutes, the rain starts and the dust falls out of the sky like the drop of a curtain."
That’s atmospheric science Ph.D. student Harvey Elliott’s description of a Haboob---an intense sand storm that kicks up in arid places like the African Sahel. Elliott spent a month in Niamey, Niger this summer---one of two field trips to study the electrostatics of airborne dust and sand. The other trip was to Boulder City, Nevada, where he studied dust devils, ran into their vortices with a video camera and then spent a day cleaning their remains out of his rented Chevy Malibu.

The video above has some of Elliott's footage, plus some from other students who have worked on this project with Professor Nilton Renno over the past five years.

With his colleagues in 2008, Renno demonstrated that dust and sand grains get electrified as they bounce along a surface. They also developed a unique electric field sensor to measure this. Now Elliott is working with Renno to use this sensor to better understand the phenomenon. The research has practical applications on Earth and on Mars.

Understanding the physics of dust- and sand-lifting could help scientists come up with more precise climate change models, as these aerosol particles and their effects on global warming are still uncertain.

And in the semiconductor and electronics industries, unpredictable electrostatic “shock” discharges (exacerbated by dust and human handling of parts) cause billions of dollars in damage per year, Renno says. Right now, there’s no reliable way to measure electric fields and charged particles in manufacturing plants on an ongoing basis. Renno’s sensor can do this. It would allow mitigating measures to go into action before a shock discharge occurred, preventing damage.

Electrostatics in Martian dust storms could affect our instruments on landers there, and could also have major implications for future human explorers.

The sensor is being commercialized through the U-M spin-out company EngXT. Renno is giving a keynote talk about it Oct. 5, 2010 in Reno, Nevada, at the Electrostatic Discharge Association's Annual Meeting.