Tesla’s autopilot update enhances role of radar
The radar sensor in Tesla’s self driving cars is not a new feature, but it will play a significantly more prominent role in the 8.0 version of autopilot. The carmaker now believes that radar can be used as a primary control sensor, without requiring the camera to confirm visual image recognition. Fleet learning has been crucial in arriving at this point in the development process.
Until now, the biggest problem in using radar for autopilot was avoiding false alarms. “Slamming on the brakes is critical if you are about to hit something large and solid, but not if you are merely about to run over a soda can. Having lots of unnecessary braking events would at best be very annoying and at worst cause injury. The first part of solving that problem is having a more detailed point cloud. Software 8.0 unlocks access to six times as many radar objects with the same hardware with a lot more information per object”, Tesla explains.
“The second part means assembling those radar snapshots, which take place every tenth of a second, into a 3D ‘picture’ of the world. By comparing several contiguous frames against vehicle velocity and expected path, the car can tell if something is real and assess the probability of collision.
Too late to brake
The third part of the problem was, according to Tesla, the hardest to solve. When the car approaches an overhead highway road sign positioned on a rise in the road, or a bridge where the road dips underneath, this often looks like a collision course. The navigation data and height accuracy of the GPS are not enough to know whether the car will pass under the object or not. By the time the car is close and the road pitch changes, it is too late to brake.
This is where fleet learning lends a helping hand. “Initially, the vehicle fleet will take no action except to note the position of road signs, bridges and other stationary objects, mapping the world according to radar. The car computer will then silently compare when it would have braked to the driver action and upload that to the Tesla database. If several cars drive safely past a given radar object, whether Autopilot is turned on or off, then that object is added to the geocoded whitelist.”
Confidence level rises
“When the data shows that false braking events would be rare, the car will begin mild braking using radar, even if the camera doesn’t notice the object ahead. As the system confidence level rises, the braking force will gradually increase to full strength when it is approximately 99.99 percent certain of a collision. This may not always prevent a collision entirely, but the impact speed will be dramatically reduced to the point where there are unlikely to be serious injuries to the vehicle occupants.” The car should almost always apply the brakes correctly, Tesla states.