Self-driving golf carts tested in Singapore

Scientists have successfully tested self-driving golf carts at a large public garden in Singapore that ferried 500 tourists around winding paths trafficked by pedestrians and cyclists.
The experiments conducted over six days also tested an online booking system that enabled visitors to schedule pickups and drop-offs at any of 10 distinct stations scattered around the garden, automatically routing and redeploying the vehicles to accommodate all the requests.
"We would like to use robot cars to make transportation available to everyone," said Daniela Rus, from Massachusetts Institute of Technology (MIT)'s Department of Electrical Engineering and Computer Science.
"The idea is, if you need a ride, you make a booking, maybe using your smartphone or maybe on the Internet, and the car just comes," said Rus.

The researchers asked participants in the experiment to fill out a brief questionnaire after their rides. Some 98 per cent said that they would use the autonomous golf carts again, and 95 per cent said that they would be more likely to visit the gardens if the golf carts were a permanent fixture.
What distinguishes the Singapore-MIT Alliance for Research and Technology (SMART) programme's autonomous vehicles is that "we are taking a minimalist solution to the self-driving-car problem," Rus said.

SMART is a collaboration between MIT and the National Research Foundation of Singapore.
"The vehicles are instrumented, but they are not as heavily instrumented as the DARPA vehicles were, nor as heavily instrumented as, say, the Google car," said Rus.

The golf carts' sensors consist entirely of off-the-shelf laser range-finders mounted at different heights - since unlike the more sophisticated range-finders deployed in some other autonomous vehicles, they measure distance only in a plane - and a camera.
Algorithmically, one of the keys to the system is what the researchers call the "dynamic virtual bumper," which can be thought of as a cylinder surrounding the vehicle's planned trajectory, researchers said.
The width and length of the cylinder are a function of the vehicle's velocity. When an obstacle enters the cylinder, the vehicle's onboard computer redraws the cylinder to exclude it. That could mean changing the trajectory, reducing the velocity, or both.

In the experiments, the golf carts received no special treatment; they jockeyed for position on the garden's paths along with everyone else.
The golf carts had the advantage of moving relatively slowly - a top speed of only about 24 kph - which gave their algorithms more time to process sensor data and recalculate trajectories.