Nissan Demos New Lane Keeping Products
IVsource.net
12 February 2001

In an exclusive demonstration for IVsource, engineers at Nissan's Oppama Research Center near Yokohama showed off  the lateral assist systems they recently introduced in Japan ... and that are now headed for the US market.

Nissan is aggressively taking on the challenge of preventing road departure collisions, with products geared for both Japanese and US markets.

Road departure collisions might be characterized as only a modest problem in Japan, but lateral driver assist systems are key to large safety improvements on US roads, where road departures account for about one-fourth of all crashes.  Last month, Hiroshi Tsuda, Nissan's US Director for ITS Research, and Hiroshi Kawazoe, Senior Engineer at Nissan's Vehicle Advanced Engineering Department, along with their colleagues, hosted your publisher at their Oppama Research Center for some exciting test ride demonstrations of the company's approach to these active safety systems.

The Nissan LKS Team, with Your Fearless Correspondent

Nissan expects to offer lane departure warning systems in the US in the next few years, in pace with the timing of other automakers.  In fact, they'll probably pick up on supplier systems, as this function is actually a relatively simple one that doesn't require exchange of vehicle control parameters with other vehicle subsystems.

However, if vehicle designers choose to employ active control to actually try to keep the vehicle safely on the road, the lane departure warning engineering challenge becomes that of effectively sensing the roadway environment to support lateral control decisions ... and then accurately providing that lateral control.  Liability and determination of driver responsibility are other issues that -- as those who have been watching the IV playing field know all too well -- come into play at that point.

All of these factors led Nissan to begin their in-house development program for both a Lane Keeping Support (LKS) system and a Lane Departure Avoidance (LDA) system.  Nissan's Research Department and Vehicle Development Department collaborated on the effort.

Reducing Fatigue Through Lane Keeping Assist

For the IVsource demo, the Nissan engineers showed off their Lane Keeping Support (LKS) system on their Oppama test track.  Seeking to strike a balance between system complexity and driver responsibility, the system is targeted at 'monotonous driving' situations such as are often found on the US interstate highway system and similar roads.  The system operates only on 'straight-ish' roads (a minimum radius will eventually be specified) and above a minimum defined speed.  Nissan's premise is that drivers feel tired after long hours of continuous expressway driving as a result of having to constantly steer their vehicles slightly to keep them in their lane.  The LKS attempts to reduce such fatigue by improving stability on the straight highway road.

The LKS, which has recently been introduced in Japan on Nissan's Cima model, offers automatic steering in parallel with the driver.  But the driver must remain engaged in actively steering the vehicle -- if he/she does not, the LKS gradually reduces its degree of assistance.  The practical result is that you can't "tune out" and expect the car to drive for you.  One could argue that this approach achieves the difficult balance between providing driver assistance while maintaining driver responsibility.

The system uses a single CCD camera to recognize the lane demarkation, a steering actuator to steer the front wheels, and an electronic control unit.  The camera estimates the road geometry and the host vehicle's position in the lane.  Based on the information, along with vehicle velocity and steering wheel angle, the control unit calculates the steering torque needed to keep within the lane.

Nissan representatives stress that steering control is merely for stability on the expressway, and not for autonomous driving.  The low level of steering force added by the control isn't enough to interfere with the driver's maneuvers.  The system is designed so that the driver never depends on this system to control the vehicle.  Also, because LKS only operates on basically straight roads, the steering angle is restricted within a few degrees. This value is set to enable driving straight against typical super-elevations or against a stiff lateral wind.

Aside from the fact that the maximum total steering wheel force applied by LKS control is set at a level which any driver would able to completely override, control is also suspended upon a driver's contrary maneuver.  The system is also interrupted when the driver operates the turn signal.

Lane Departure Avoidance Integrated

Nissan's LDA system, on the other hand, is being developed to reduce road departure crashes by actually delaying a driver's deviation from the lane via vibrating steering wheel and audible warnings.  Somewhat analogous to a co-pilot function, Nissan's LDA creates a lateral "buffer" for the driver, and kicks into action to automatically steer if the vehicle starts to depart the lane.  But, unlike a true co-pilot, the system won't continue to handle the steering job -- with haptic feedback in the steering wheel, the driver is alerted to the system activation and is expected to re-assert safe control by his or herself.  The automatic steering assist is steadily reduced over a period of several seconds.  So, a road departure crash is still possible, but would be much less likely unless the driver is seriously incapacitated.

LDA is accomplished using the same basic components of LKS: a camera, a steering actuator, an electronic control unit, and a buzzer or other warning annunciator.  When the host vehicle is going to deviate from the lane, the system warns the driver by vibrating the steering wheel and sounding the buzzer, and uses automatic steering to delay deviation from the lane.

In the demo, when the host vehicle deviates from the lane for any reason (due to lateral wind, cant of the road, or deliberate mis-steering), the vehicle is controlled to run along the lane markers.  After running along the lane markers, the control shuts off gradually.  At all times, as with the LKS system, the steering force added by the control doesn't interfere with driver's maneuvers, and control is suspended by the driver's action in re-taking control.

For both systems, the human-machine interface is fluidly integrated with the existing Adaptive Cruise Control displays.

Test Drive Proceeds Without Mishap -- Even with Bishop Behind the Wheel

Your publisher's most vividly experienced aspect of the test drive was getting used to a Japanese right-hand drive vehicle.  But, after a brief acclimation period, we made successful attempts to engage the respective systems in each of the two vehicles.

System operation was quite elegant for the LKS, very gradual.  True to its design for straight roads, it shut off automatically as the sharp curves at the ends of the test track were encountered.  The LDA system very clearly alerted the driver to lane excursions to both the right and left, and was quite willing to let us drive into the grass if we ignored the warnings.

Though the system's ability to combat fatigue and inattention couldn't really be tested -- the novelty-related excitement of the drive precluded that -- our sense was that the system has real potential as a 'faithful companion' on those lonely long-haul drives that are responsible for so many of the single-vehicle statistics. 

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For More Information ...

... contact Hiroshi Tsuda of Nissan at hiroshi.tsuda@nissan-usa.com.

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