The team at the Center for Automotive Research at Stanford (CARS) are aiming to send a specially-equipped robotic Audi at break-neck speed up the tight bends that lead to Pikes Peak without a driver … something that hasn’t been done before.
Pikes Peak, Colorado Springs, sits atop a 12.4-mile Rocky Mountain road - a combination of paved and gravel track that has 156 turns and a climb of 4,720ft. An official contest for human drivers will take place in June, but the Audi nicknamed “Shelley” (after the first female driver to win the event, Michele Mouton) will attempt a timed race in September, when she will be alone on the track.
When the Pikes Peak race began in 1916, drivers brave enough to negotiate the dusty switchbacks and massive climb hoped their cars would not overheat or fall apart before reaching the 14,000-foot summit.
Though not afraid of the engine overheating, Shelley's team, like the racers of the early 1900s, hopes this autonomous car will make it around the turns and up the mountain in one piece.
"Our first goal is to go up Pikes Peak at speeds resembling race speeds, keep the car stable around the corners and have everything work the way we want it to," said Chris Gerdes, program director of CARS and leader of the graduate research team.
"We're not going to put it on the mountain until we can do it safely,” he said.
The team at CARS has filled the trunk of the Audi TTS with computers and GPS receivers, transforming it into a vehicle that drives itself.
Following on from past impressive results - winning its first autonomous race in 2005 with Stanley, a car developed for the Grand Challenge held in the Mojave Desert by the Defense Advanced Research Projects Agency (DARPA); and a second car, Junior, runner-up in DARPA'S 2007 Urban Challenge - the team is hoping to be the fastest up the mountain with Shelley. Other autonomous vehicles have reached the summit but only at speeds of around 25mph, say the team.
Unlike Stanley and Junior, who sense the road with radars and cameras, Shelley will follow a GPS trail from start to finish. The trick will be to stay on the road at race speeds while sliding around the corners.
Shelley has reached speeds of 130mph without a driver on testing grounds at the Bonneville Salt Flats in Utah (see video below). At first glance, the car seems like a normal Audi, but a closer look reveals advanced computers, GPS antennae and nobody in the driver's seat.
Shelley, or rather the team, knows exactly where she is on the road by using a differential GPS, which is much more accurate than a standard GPS system. Hers corrects for interference in the atmosphere, showing the car's position on the Earth with an accuracy of less than one inch (around 2cm). Shelley measures her speed and acceleration with wheel-speed sensors and an accelerometer, and gets her bearings from gyroscopes, which control equilibrium and direction.
"The computer puts all this information together and then compares it to a digital map to figure out how close the car is to the path that we want it to take up Pikes Peak," said Gerdes.
The team says that the computers in Shelley's trunk will plug into the car's existing electric steering system and the car will move into action with stock automatic gear shifting and brakes with an active vacuum booster, a feature that normal cars use for emergency braking.
Using complex algorithms, the researchers have programmed Shelley to handle like a racecar. For example, as the car approaches a turn, it calculates a best guess on steering and acceleration. Audi's steering system normally responds to the steering wheel, but since there is no driver, it responds to algorithms that combine information such as the GPS path and inertial movement picked up from its sensors.
As the car approaches a corner, another set of calculations corrects the handling through the turn and prepares for what might happen next.
While other autonomous cars have crossed the finish line of the Pikes Peak course, the CARS team’s goal is to do it at race speed, or even faster.
"There are some sheer drops at Pikes Peak in which any sort of self-preservation kicks in and you slow down a bit. We want to go up at the speed that few normal drivers would ever think of attempting."
In addition to high-tech racing, the team is hopeful that its research may lead to safer cars that respond to human error. "We hope this project demonstrates that the technologies of stabilizing the car and helping the car stay in its lane will work with each other all the way up to the very limits of the vehicle."
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