ブックタイトルマツダ技報　2012 No.30

概要

マツダ技報　2012 No.30

マツダ技報No.30(2012)3.3 Detection and classification of issues preventinglane changeNot every vehicle being in the closing or blind spotarea is a thread to the safety of the ego vehicle. It isnecessary to further classify the target vehicles to judge,if a potential danger is existing. E.g. vehicles that areentering the closing area from rear with a very lowdifferential speed (10km/h) need nearly 20s to progressfrom border of closing area to the blind spot area. Here anotification should be given to the driver of the egovehicle, when a Time-To-Collision (TTC) of 5.5s isreached. This value has been developed based onextensive driver tests, considering reaction times,perception of urgency and its latency. However avehicle entering the blind spot area of the ego-vehicleshould always be notified from wherever it enters. Onlyif the vehicle has completely left this area, thenotification can be cancelled.analyze their location and relative speed very precisely.Weather influences the performance only very minor, sothat a continuous operation can be achieved. The pictureon the right shows the beam shapes of the radar sensorsof the blue Mazda and the detected vehicles in the blindspot and approach zone.4. The Human-Machine-Interface (HMI) Concept4.1 Warning the driverThe HMI should not make the driver give up hischecking of mirrors. (Misuse avoidance) Therefore theindication of a vehicle in blind spot area or closing withTTC<5.5s is notified by a LED light in both side mirrorareas. This is far out of the primary area of vision so thatthe driver still needs to look into the mirror direction. Incase the driver neglects the notification and sets turnsignal for changing lane, an audible warning is given, toprevent action. Mazda followed by this a two stepwarning procedure using a warning indication based onSAE J 2802 with fast blinking lights for the imminentdanger warning.Fig.3 Indication of Car in Blindspot Area or Approaching to itFig.2 Radar Beam Forms and Vehicle Detection3.4 Technical solutionIn principle a detection of vehicles in the blind spotzone can be done by different sensor types such ascamera systems. This has been shown already by someOEMs. Such technical solution shows insufficiencies interms of weather robustness and especially the detectionof vehicles in the closing area. A very robust sensor is a24GHz short range radar. Mounted well protectedbehind the bumper fascia at the two rear vehicle cornersallows to detect vehicles in the closing and blind spotarea. The classification allows to distinguish stationaryobjects like road signs from moving objects and to4.2 The HMI dilemmaAny lane change support device suffers one key issue:the knowledge about the actual driver intention. Driversshow their intention to change lane differently:? drivers set the turn indicator to show their will tochange lane and await a suitable“gap”on the targetlane,? others set the turn indicator, when the“gap”ispresent and notify the instant following lane changeaction,? finally some drivers do not indicate lane change atall.Mazda decided to change from notification to warning assoon as the driver sets the turn indicator. This leads to asafe warning of the majority of drivers. To assure thatthe driver recognizes the warning Mazda introduced astrong blinking of the notification LED and an audiblebuzzer. The later one (if notification LED and audiblebuzzer turn on at the same time) can be reduced involume or switched off to avoid driver annoyance.―172―