In developing the body architecture and active safety-systems array in the 2013 Cadillac ATS, General Motors engineers used new approaches to measuring and evaluating driver visibility beyond the typical subjective metrics, revealed Raj Mehta, Vehicle Architecture Engineering Group Manager.
“Conducting clinics in Europe as well as the U.S. provided invaluable insight into the needs of drivers who use demanding roads like the Autobahn,” said Mehta.
From the customer-visibility input, his team focused on optimizing exterior mirror and A-pillar area size, seat height, and forward and side vision distance. They also worked to minimize or eliminate intrusive objects in windows such as rear headrests and the interior rearview mirror.
GM engineers have been keen to find new methodologies in this key safety area, given the evolution of vehicle structures—including thicker-section roof pillars needed to accommodate airbags and support new rollover requirements; lower roof heights required to decrease frontal area for improved aerodynamics; and raised decklid heights aimed at increased cargo capacity—that create visibility challenges.
Mehta’s team used a new GM visibility evaluation technique to help characterize the 3-D aspect of A-pillar sightlines. The technique, which involves “hedgehog” visualization (familiar to design engineers and so nicknamed by its spikey computer plots), enables designers to quickly study how changes in windshield angle or pillar cross-section affect the driver’s ability to see targeted areas. These areas are derived from careful evaluation of performance driving scenarios, such as those regularly used at GM’s Milford Proving Ground.
These findings were validated and used to create a Driver Visibility Calculator. The ATS development team used the data to keep the car’s hood low and A-pillars relatively slender through the use of high-strength steel. The resulting body architecture achieved a “very good” internal score for forward visibility. The A-pillars are positioned wide to allow a broad field of view, and they are angled toward the driver to require minimal head movement to peer around.
The designers also created a narrow support structure for the ATS’s exterior mirrors, which resulted in a “very good” internal score on cornering visibility through turns.
Aiding the car’s basic structural geometries is the available rear-vision camera with dynamic guidelines. The camera provides a natural view of objects directly behind the ATS in the center stack display. Dynamic guidelines laid over the video image assist in parking maneuvers by showing the vehicle’s path and available space. Onboard radar and ultrasonic sensors also are used in conjunction with the camera to help enhance driver vision.
Executive Chief Engineer Dave Leone noted: “Our ability to execute good visibility based on robust scientific methods will be an important tool in the development of Cadillacs to come.”