The CMU front axle broke because they high-centered on a berm while taking a switch-back too tightly, their front wheels were off the ground and started spinning enough to set the tires on fire, and so DARPA hit their e-stop, which was a system which clamped down on their front axle - and the sudden force snapped it.
CMU failed not because of their rollover (and the fatigue on their mechanical parts) but because their software relied more on pre-planned maps than on obstacle avoidance, and they hit crap and high-centered on stuff.
As someone who worked on a vehicle last year, I can tell you what we did (and that DARPA approved it just fine):
Just the brake won't cut it. What they want are big red buttons on the side of the vehicle that, when you hit them, immediately bring the vehicle to a stop. If the big red buttons trigger an actuator/wire/lever whatever that hits the brake, that works dandy for them. As for labeling, if the sign is right next to the lever, that works fine for them too.
Of course, these aren't official DARPA answers - just what seemed to work for them last year.
Actually, the CMU team didn't stop because they broke an axle - they broke an axle because they stopped.
What happened was that they took a hairpin turn too sharply, got high-centered on a berm on the side of the road, and started spinning their front wheels extremely fast. Apparently, this caused their front wheels to catch on fire, throwing flaming rubber everywhere. The chase vehicle saw this and hit the e-stop, but their e-stop was a little too good - it clamped down on their front axle to stop the wheels from spinning, and the sudden force snapped it.
Slashdot Mirror
The CMU front axle broke because they high-centered on a berm while taking a switch-back too tightly, their front wheels were off the ground and started spinning enough to set the tires on fire, and so DARPA hit their e-stop, which was a system which clamped down on their front axle - and the sudden force snapped it. CMU failed not because of their rollover (and the fatigue on their mechanical parts) but because their software relied more on pre-planned maps than on obstacle avoidance, and they hit crap and high-centered on stuff.
As someone who worked on a vehicle last year, I can tell you what we did (and that DARPA approved it just fine): Just the brake won't cut it. What they want are big red buttons on the side of the vehicle that, when you hit them, immediately bring the vehicle to a stop. If the big red buttons trigger an actuator/wire/lever whatever that hits the brake, that works dandy for them. As for labeling, if the sign is right next to the lever, that works fine for them too. Of course, these aren't official DARPA answers - just what seemed to work for them last year.
Actually, the CMU team didn't stop because they broke an axle - they broke an axle because they stopped. What happened was that they took a hairpin turn too sharply, got high-centered on a berm on the side of the road, and started spinning their front wheels extremely fast. Apparently, this caused their front wheels to catch on fire, throwing flaming rubber everywhere. The chase vehicle saw this and hit the e-stop, but their e-stop was a little too good - it clamped down on their front axle to stop the wheels from spinning, and the sudden force snapped it.
Actually, that's not true. Several teams made it through the qualifying round, including CMU, Caltech, and SciAutonics II.