Nissan Goes to Level 2

With the ProPILOT Assist system, Nissan is combining intelligent cruise control and 
a steering assistance system to help facilitate driving on limited-access expressways.

Several years ago at the Ford test facility in Romeo, Michigan, I had the opportunity to drive with Sir Jackie Stewart in the right seat. For those of you who may not be familiar with Stewart, know that he is one of the greatest racing drivers of all time, having won the World Drivers’ Championship three times during the nine years that he raced in the Formula One series (and came in second twice).

But when I was driving with Stewart it wasn’t on a racing circuit, nor were we driving at speed. Rather, we were on a straight, flat surface. He had me get to 50 mph and hold it there (which, incidentally, is harder than you might imagine, especially given who was sitting next to me).
The objective of the exercise was to notice all of the little steering wheel inputs that were required to hold the car along the straight and narrow. And the number of inputs were astonishing. 

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One of the things that cause fatigue in driving is just that: holding a car in the center of a line due to the multiple minor inputs performed over an extended period of time. I related the story of Jackie Stewart to Andy Christensen as I am behind the wheel of a 2017 Nissan Rogue driving east bound on I-696 in Detroit. An enhanced version of Nissan’s intelligent cruise control system was activated, so I didn’t need to worry about holding a steady speed. As 
the post-morning rush hour traffic sped and slowed, sped and slowed in its usual maddening lack-of-pattern, the Rogue adjusted its speed accordingly.

But there is one thing that Christensen—senior manager, Intelligent Transportation Systems Research, Nissan Technical Center North America—and his colleagues had added to the vehicle that would have probably made my ride with Stewart even better: steering assist.

The Rogue was able to maintain its position in the lane without my having to nudge the steering wheel—and it should be noted that while the system was adjusting the steering without my input, my hands had to be on the wheel because otherwise, the system was going to let me know in no uncertain way that I was responsible for piloting the vehicle.

Which may be why the name of the system, which will debut on the next-generation, 2018 Nissan LEAF electric vehicle, is named “ProPILOT Assist.” It is a driver assistance system, not some sort of self-driving functionality. Christensen, who is on the SAE committee that has created the self-driving taxonomy for automated vehicles, said that ProPILOT Assist is at Level 2. That is defined (by SAE J3016) as: “Partial Automation: The driving mode-specific execution by one or more driver assistance systems of both steering and acceleration/deceleration using information about the driving environment and with the expectation that the human driver performs all remaining aspects of the dynamic driving task.”

The driver is in the loop and needs to remain that way.

From the point of view of the system elements, there are a front camera mounted near the rear-view mirror, a forward radar (with a range of approximately 150 meters) in the front fascia, electronic power steering for steering control, an electronic control unit for throttle control, a vehicle dynamic control unit for brake control, an electronic parking brake to hold the vehicle and an ADAS (advanced driver assistance system) electronic control unit for overall control logic.

Once the system is activated, the intelligent cruise control operates essentially like that in other vehicles equipped with such systems with the primary difference being that there is what Christensen described as a “stop-and-hold system.” He explained, “Most systems today may bring a car to a stop, then hold it for a second or two. But then the system disengages and the driver has to manually press the brake pedal to hold the vehicle at a stop.” That isn’t useful in stop-and-go situations. “We’ve added a feature that holds for an extended period of time; the system doesn’t disengage.” If the stop is less than three seconds in duration, then the vehicle will automatically start moving. If longer, then it is simply a matter of hitting the resume button on the steering wheel or tapping the accelerator to start moving.

The other portion is the steering assistance. While many vehicles offer “lane-keeping assists,” Christensen said, “in layman’s terms, we call them ‘ping-pong’ systems.” That is, they work when the vehicle is about to depart the lane, so the vehicle, conceptually, bounces back and forth between the lane markings.

The difference here: “This system is sustained control.” It is a lane-centering system.
(For those interested in the levels of automated driving systems, know that Christensen said that both intelligent cruise control and lane-keeping assist are Level 1. Even having both of them does not bring a vehicle to Level 2.)

But this lane centering is predicated on the need for the camera to detect consistent lane markings, so Nissan positions the product as being a feature that provides assistance on limited-access expressways, as that’s where there are generally visible lane markings. Which also explains why the driver has to maintain control of the steering wheel because should the markings disappear, then the system will audibly and visually notify the driver. 

Will it work during the winter? Yes, if the lane markings are visible. No, if they aren’t. “It is an optical system,” Christensen said. “If you can’t see the lane marks, it can’t see them.”

One of the things that Christensen seems to be most proud of is the fact that the ProPILOT Assist system has been developed for deployment on mainstream vehicles. He pointed out, for example, that it is debuting on a Nissan car, not an Infiniti. “We want this to be an attainable product for a wide variety of customers.”