Online Extra: Grand Challenge Wrapup

"No one said this was going to be easy," said Philip Koon the morning of the Defense Department's first autonomous vehicle race, called the Grand Challenge, held March 13.

An engineer for Boeing Co.'s Phantom Works division, Koon was a volunteer for one of the teams that participating in the event, and he had learned that his vehicle, a modified Hummer, had just been disqualified.

"It ran into a fence post, and just pushed it over and kept going," Koon said. That wasn't what disqualified the vehicle, however. The fence post knocked out some sensors, leaving the vehicle less able to find its way around. It soon wedged itself on a berm and caught fire.

Such are the lessons to be learned about teaching vehicles how to drive themselves. Each team in this race equipped a vehicle with the hardware needed to navigate itself across the desert. Koon's team, called the Red Team was an effort led by Carnegie-Mellon University professor William "Red" Whittaker.

For integrators, this media-hyped event had more significance than just the novelty factor of being the first long distance robot race. It also is addressing some of the problems they will shortly see with their own platforms and computer systems.

So, not suprisingly a few of the large defense platform integrators, such as Boeing, Northrop Grumman Corp., of Los Angeles, and Science Applications International Corp., of San Diego, lended support to some of the team efforts.

What made this event different from the usual off-road race is that once the robotic vehicles were set loose, they were entirely on their own. No remote-controlled operations were allowed. Each vehicle had to find its own way across 142 miles of desert to the finish line, outside Primm, Nevada.

"It didn't matter to us if anybody completed the course," Tether said. "We wanted to spark the interest in science and engineering in this area."


The grand start

The race began at 6:30 a.m. at the Slash X Café, a tavern favored by off-roaders eight miles outside Barstow, Calif. Over the next few hours, a total of 12 more self-directing, or autonomous, vehicles would set off on a journey to Primm. The first vehicle to finish, DARPA promised, would win a $1 million prize.

It was no surprise that the red Carnegie-Mellon's Hummer, provided a solid start to the race. Of all the teams, the Red Team appeared to put the largest investment into its vehicle, an estimated $3 million worth of parts and labor. Its driverless vehicle ran so well that one might have thought that it could actually get all the way to the finish line.

As a small crowd cheered on from the bleachers, the fire engine-red vehicle smoothly bounded from a starting chute?fashioned from a pair of concrete bunkers?and guided itself down a dirt road and around the series of curves that doubled back along the path behind the staging area. Within an hour, it was a few miles from the starting line.

Needless to say, most of the launches that followed the Hummer's were not as smoothly executed.

Starts were staggered in five-minute intervals. DARPA officials had ordered the starting line-up based on the probability each vehicle had of completing the race, the strongest contenders departing first.

Team Caltech's white sport utility vehicle lurched out of the starting gate far more tentatively and stopped every 30 seconds or so to recalculate its course. "I wanted to keep the truck in one piece," said team leader Richard Warren. As a result, the team programmed the vehicle to move ahead cautiously.

Team CajunBot's all terrain vehicle, painted the color of green hot pepper sauce, ran about 20 yards before sideswiping a concrete bunker, a jam it tried to extricate itself from by attempting to roll over a bush.

Team member Chris Meaux later said that they had programmed the vehicle to understeer in order to compensate for the dirt road.

Team ENSCO's six-wheeled vehicle speedily jumped out of the starting gate and took off down the straightaway. It soon jumped up into bushes alongside the road itself and continued on its mad drive. When it attempted to get back on the road after a few hundred yards, it flipped over.

Other vehicles didn't even get out of the starting coral. The brakes of Virginia Tech's golf cart-like vehicle locked up at the start of its run. Axion Racing's sport utility vehicle got only a few feet out of the starting gate before losing its way. It wandered around seemingly at random until it was disqualified by the judges.

Truck Smart

As the long-term research arm of the Defense Department, DARPA has a vested interest in getting people to think about autonomous navigation. Congress has set a goal for the Defense Department to make one-third of all its ground vehicles unmanned by 2015.

Autonomous vehicles are nothing new. Some are already in commercial production?think robotic lawn mowers and farm tractors. But none of those are designed to navigate through a course as complicated as the Grand Challenge, a rock-strewn route punctuated with steep slopes, dry lake beds, water, mud, cattle guards and, of course, lots of sand.

The teams themselves ranged from highly organized consortiums of companies and academia to southern California gearhead shops specializing in high performance racing automobiles. A few high school- and university-student teams even participated.

The prior Monday, DARPA started a week's worth of qualification runs?mostly to insure that the vehicles were safe?at a speedway in Fontana, Calif., cutting the number of contestants to 15. Two teams backed out in the last minute, citing technical difficulties.

The vehicles that made the final cut largely all had the same basic design. Most of the teams used commercial vehicles, ranging from four-wheel-drive pickups to the modified all-terrain-vehicles favored by off-road enthusiasts. Various commercially available actuators, hydraulic pumps and servers were rigged to operating the steering, acceleration and braking.

The hardware the teams used also was largely commercial. Commercial Global Positioning System receivers provided coordinates of the vehicles in relation to their chosen route. Off-the-shelf-radar was used to provide long-range vision for the vehicles, while stereo cameras or light-detection and ranging devices, called lidar, provided more detailed information of closer objects.

What was unique about each vehicle?and the ingredient that DARPA was interested in?was the software that would process the sensors' information and make decisions on how to move forward.

"The secret sauce is in interpreting these sensors and figuring out what to make the vehicle do," Tether said during the wrap-up press conference. "Not only to be able to say, yes, that is path over there, but to transform that to the vehicle?to go fast, put a brake on, turn left."

For the participating teams, creating such software proved to be quite a task. Most vehicles were equipped with computers, which would plot out in real-time a course using input data not only from radar, stereo cameras and other sensors, but also from readings for a global positioning system receiver and an internal map of the route. It also had to send signals to the control functions of the vehicle?the jerrybuilt devices that controlled steering and braking?and factor in feedback from those elements as well.

"We had to get to the current position of the vehicle into the computer somehow, and we had to determine where we wanted it to go. And we had to have feedback on all the different parts of the control, like the steering, velocity and the brakes," said David Caldwell, head programmer for the Golem Group, one of the teams with a vehicle in the race.

The Golem Group vehicle's control software was written from scratch and ran on an onboard Linux laptop computer, Caldwell said. Most of the code was written in the C programming language, with some microcontroller interfaces written in the Fourth Generation programming language. The team also borrowed some publicly available imaging libraries to identify the input coming in from the sensors.

The bitter end

By 11:30 a.m., the race was declared over. By then, even the best vehicles rendered themselves useless.

The day's favorite, Carnegie Mellon's Hummer, drove for 7.4 miles before dying a smoky death. The vehicle experienced "what is known in robotics as a system failure," said Red Team technical advisor Jay Gowdy, meaning it experienced a series of minor failures that cascaded into entire system inoperability.

The chain of problems started with the truck knocking out its front fender, losing its sensors. That left only the less-accurate global positioning satellite coordinate to navigate by. As a result, the Hummer soon veered off course, tearing up its underside and eventually wedging itself on top of a large rock. Trying to free itself, it then tore the rubber off its tires, which landed near the engine and caught fire, Gowdy said.

Another favorite that came to a grinding halt was TerraMax. Here was a vehicle for which difficult terrain would certainly be no challenge: a 5-ton tactical military truck manufactured by Oshkosh Truck Corp., of Oshkosh, Wis. OshKosh had teamed with Ohio State University to enter the competition. Observers at the qualifications remarked on how easily the lime green vehicle could push entire concrete bunkers out of its way.

Nonetheless, information overload brought the beast to a halt a mere 1.2 miles from the starting line, said TerraMax team member Don Verhoff. When the vehicle veered slightly off the path, the information from its sensors overwhelmed the operating system.

The truck stopped to reboot its computer, but when it reawakened, it couldn't place where it was on the route map. So it backed up to find its bearings. Even when it backed across the pathway, it still couldn't place itself.

Caltech's vehicle fared slightly better. It lurchingly made its way through the first mile before coming to a stop off in the far distance, barely within eyesight.

Caltech's team leader Richard Warren, who was standing along the course just outside the starting gates with other spectators, was trying to figure out why his vehicle wasn't moving. He talked by cell phone and walkie-talkie with other team members, who were equally at a loss.

Each vehicle was closely followed by a control vehicle manned with DARPA personnel, who, through remote control, could pause or shut off the autonomous vehicle if it endangered the safety of humans or wildlife.

But none of the vehicle's team members accompanied the DARPA control vehicles, so information teams could get about their vehicles was scanty at best.

"You just want to find out what is wrong and then go out there and fix it," Warren said, squinting in the distance. Slowly word came back that the vehicle had jumped over a fence, wrapping barbed wire around its rear axle.

The tenacious machine slowly kept on, plowing through a number of bushes before jumping back over the fence and onto the road again. Then it stopped. And for the remainder of the race, the vehicle sat in distance, not moving.

Despite the fact that no vehicle completed more than a twentieth of the course, DARPA was happy with the results. The performances were "extremely impressive," Thomas Strat, DARPA deputy program manager for the event.

He noted that after the first five miles the course got considerably more difficult, with steep narrow slopes and a switchback to navigate through. A total of four teams' vehicles made it into this rough terrain?The Red Team, SciAutonics, Digital Auto Drive and the Golem Group.

One day, promised Tether, entire military conveys of trucks filled with supplies will find their way to the front, perhaps using some of the technologies pioneered by this event.

Judging from today's race however, it might be a while before the machines run the military supply lines by themselves.

The event was "a good day for the tow-truck drivers," as one spectator said.