GPS and perception sensors guide the Red Team's driverless desert racer.

by Lawrence Kren
Senior Editor

Navigate a race-prepped Humvee 250 miles across the desert from Barstow, Calif., to Las Vegas in 10 hr or less and collect $1 million in cash: Sounds reasonable, right?

Try it without the driver.

That's what Red Whittaker and his Red Team from Carnegie Mellon hope to do March 13 at the Darpa Grand Challenge. They aren't alone. The quirky race billed as "A Historic Demonstration of Autonomous Robotic Vehicles" has attracted some 40 teams, each with its own robot-piloted design. The entry quickest to complete the grueling desert course within the allotted time wins. Autonomous means exactly that: Race vehicles can receive no external communication or human control whatsoever. Just to make it more interesting, organizers will reveal the route just 2 hr before the start of the race.

Audacious? Perhaps. But "Dwelling on qualifying descriptions such as 'difficult' or 'unprecedented' doesn't get it done," says Whittaker. "People overdo the sensing/navigation aspect of the design. Robots have been navigating for two decades so there is plenty of information out there." Whittaker knows. It was his robots that scoped the fried nuclear reactor at Three Mile Island and more recently shimmied down abandoned coal mines.

What's probably less debatable is his choice of vehicle to make the trek: a 1986 military-issue Humvee. Humvee's off-road prowess is legend, and the battle-weary, high-mileage specimen that arrived at the University last spring is receiving a major overall. A larger-displacement, turbocharged powerplant will likely replace the original (and anemic) 6.2-liter diesel. Having more oomph helps offset imperfections in the computer control and coordination systems and, of course, may give it an edge over the competition.

Special attention was lavished on the vehicle's suspension. Here, Red Team took cues from off-road gurus Chad and Ron Hall at Team Hummer. "We traded-up to race-grade air suspension and springs to soften the ride," says Red Team Member Chris Urmson, a fourth-year engineering doctorial candidate at the University. "We're also running special B.F. Goodrich Baja tires and Hutchinson rims."

Whittaker explains all the fuss over ride quality:
"Human drivers on rough terrain do a great job of stabilizing their visual field. We take a three-step approach to stabilize perception sensors on the truck."

Red Team's Sandstorm Humvee undergoing trials at an undisclosed location.

First, the specialized suspension improves the overall ride. Next, an intermediate mechanical stage that occupies what would be the front seats holds the navigation equipment, computers, and electronics. Isolation mounts from Lord Corp., Cary N.C., protect it and the enclosed equipment from shock loads, though the motion would still make you seasick. That's the reason for step three.

Mounted on top the intermediate stage is an actively controlled three-axis gimbal fitted with a fiber-optic gyro and harmonic servoactuators from HD Systems, Hauppauge, N.Y. The gimbal holds a steady inertial gaze for key perception sensors that attach to it. In essence, the intermediate stage provides a stable platform from which the gimbal can operate. Otherwise, the gimbal would oscillate and servo wildly to compensate for bumps and jars, which is unacceptable. "A jitter-free, rock-solid gimbal is one of our Big 10 winning edges," says Whittaker.