google自动驾驶报告-201610

ON T HE R OAD

MASTERING T HE T HREE-POINT T URN

For m any d rivers, t he t hree-point t urn i s o ne o f t he l ast h urdles s tanding b etween a l earner’s p ermit and t he o pen r oad. A nd f or g ood r eason. T his i s o ne o f t he t rickiest m aneuvers t o m aster, a s d rivers attempt t o m ove a t wo-ton m achine a f ull 180 d egrees. O ften, d rivers a re f orced t o t entatively i nch forward a nd b ackward, i n t ight s paces, w ithout a f ull v iew o f t he r oad. O ur g oal i s t o a d evelop a f ully self-driving c ar t hat c an h andle e very p art o f d riving, a nd t hat m eans t eaching o ur c ar t o h andle advanced m aneuvers l ike t hese m ulti-point t urns.

Human d rivers d o t heir b est t o e stimate t he i deal a ngle a nd d istance t o m ove i n o rder t o s olve t his geometric p uzzle. B ut a ll t oo o ften, t hese t hree-point t urns b ecome t en-point t urns a s d rivers awkwardly s hu e a round t he r oad. O ur s elf-driving c ars, o n t he o ther h and, c an s ee a f ull 360 degrees, m easure d istance d own t o a f ew c entimeters, a nd p recisely c alculate t he q uickest p ath f or the c ar. O ur c ars d on’t j ust f ollow a f ew s tandard t urns e ither. W e’ve t aught t hem t o a dapt t o a ll kinds o f v ariables —i ncluding d ead e nd s treets s tacked w ith p arked c ars, t rash b ins l ittered o n t he curbs, a nd n arrow b ottlenecks.

There a re a n i n nite n umber o f p ossible w ays t o t urn a c ar a round. B oth h uman d rivers a nd

self-driving c ars h ave t o c alculate t radeo s —h ow w ide d o w e m ove? h ow c lose d o w e g et t o t he curb? h ow m any t imes d o w e c hange d irection? O ur c hallenge i s t o t each o ur s elf-driving c ars t o choose t he o ption t hat’s n ot o nly t he q uickest ,b ut o ne t hat f eels n atural t o p assengers. F or e xample, our c ars c ould s pend m ost o f t he t hree-point t urn d riving i n r everse (after a ll, o ur s ensors d on’t h ave to t wist i nto a y oga p ose t o g et a f ull 360 d egree v iew o f t he r oad b ehind). B ut t hat’s n ot h ow p eople drive —t hey’d m uch r ather d rive f orward w here t hey h ave b etter v isibility o f t he r oad a nd c an m ore easily m aneuver t he c ar. S o w e’ve t aught o ur c ars t o m imic t hese h uman p atterns, f avoring w ider forward a rcs, r ather t han a s eries o f s hort m ovements b ack a nd f orth.

In t he q uest t o p erfect t he t hree-point t urn, o ur c ars p ractice a bout 1,000 m ulti-point t urns e very week o n r eal c ity s treets. T he a bility t o n avigate e legantly a round t ight s pots i s e ssential t o b uilding a driver t hat c an g et y ou f rom d oor-to-door, w hether i t’s t aking y ou f rom y our h ome i n a s uburban cul-de-sac o r d ropping y ou o a t a d owntown b ar h idden d own a d ead-end s treet.