Graphic representations of lane departures are just one way in which the RDCW unit warns drivers that trouble is just around the corner, so to speak. Sensitivity to lateral drift and corner speed are adjustable in the test system, but production units would learn the capabilities and habits of the driver in order to pre-select the sensitivity level. It could even adjust warnings based on whether the driver hugged the left or right side of his lane.
Delphi's active rear steering system offers better maneuverability in a compact package designed to fit into existing suspension packages.
"Lane departure warning systems are the first level in what will become a comprehensive system that looks around the car, evaluates the situation, conducts a threat assessment and warns the driver," says Scott Bogard, senior research engineer, Engineering Research Div., University of Michigan Transportation Research Institute (UMTRI). UMTRI is the prime contractor for the program (funded by the U.S. Department of Transportation under its Intelligent Vehicle Initiative) to evaluate just such a system. Developed and built by Visteon with the help of AssistWare Technology (Wexford, PA), the Road Departure Crash Warning (RDCW) system is fitted to a fleet of 11 Nissan Altima sedans that will be loaned to a total of 78 people for one month each. (See "Field Testing RDCW.")
"We are in the quote process for stand-alone systems that will provide the building blocks for a RDCW system," says Tim Tiernan, senior manager, Driver Awareness Systems at Visteon, "and they could hit the market in the 2007 or 2008 model year." But Tiernan says an integrated RDCW system will be available just two years later, making it feasible for the maker of a high-end vehicle to include it on the option list for its 2009 or 2010 models. "It's an aggressive timetable," Tiernan admits, "but one we think is well within reach."
The building blocks for the system are relatively simple: a 24 GHz radar unit on each side of the vehicle to provide blind spot warnings, a longer range forward-looking radar unit, a camera mounted near the rearview mirror to detect lane markings, and a navigation system that uses the latest high-definition digital maps. To this is added a set of "likely path" algorithms that determine the probability that the driver will follow a certain path given the choices available to him. This does two things: (1) it lets the system concentrate the bulk of its detection efforts on probable primary threats, and (2) enhances the lane departure function to include a lateral drift warning (to alert the driver if he is drifting off the intended path and into a situation that could result in a collision or rollover).
For all of its Buck Rogers connotations, Tiernan says the electronics necessary to integrate these systems into a cohesive unit are known quantities. "The basic threat assessment analysis could be done in the sensors themselves," he says, "which recognize the object and its location, and send this information through the high-speed CAN bus." Pre-processed information flowing from up to six radar units operating at 10 Hz each (Tiernan eventually envisions pairs of front and rear pre-crash warnings joining the side object detection units) could be handled by a 16-bit processor on the CAN bus, though the video system would need more silicon firepower. "An imaging chip won't give you processed information. It gives you an image," he says. "Which means there would be a need for digital signal processors and greater processing power to do the analysis." This 32-bit chip would decipher the information contained in the image and pass this along the CAN bus.
Placement of the units around the car is a problem that Tiernan is working on both with OEMs and Visteon's business units. Though forward-looking cameras have gravitated toward placement in the inside rearview mirror housing, and side-looking radar units are a natural for outside mirror housings, the question of where the front or rear units reside is still up in the air. "Radar has no trouble looking 'through' plastic fascias, but this places them in a vulnerable position," says Tiernan, "and mounting them behind metal destroys their effectiveness." As designated safety systems that must be protected in collisions up to 5 mph, lighting units offer a package space that eliminates these worries. Currently, a 24-GHz radar sensor is slightly smaller than a standard 3x5 card, and likely would have to shrink in order to minimize their effect on the size of the lighting package.
And while OEMs haven't asked for the exact RDCW system currently undergoing field operation tests (they are awaiting the results from the UMTRI test to see how the technology works on the road, and how consumers will respond to it), the drive to add greater value and profit to a technology is leading them in this direction. "Already, vision systems are being used to determine road curvature so headlight beams can be adjusted before you get to a curve, or to do rudimentary threat assessment," says Tiernan. "When the entire suite of technologies is added to a vehicle, RDCW will be one of the added-value capabilities available to OEMs."
Field Testing RDCW
What will the 78 test subjects see when they borrow one of UMTRI's Nissan Altimas? If they don't open the trunk (the computer hardware is mounted back there), nothing. There are no decals or other visible signs that this Altima is any different than the thousands of others on the road. Even the camera mounted to the driver's side A-pillar that records facial reactions in order to match them with warnings is relatively subtle.
During the first week of driving, the system collects data in order to establish a baseline, and its warning function is not active. Once this familiarization period is over, the RDCW becomes fully active, and provides levels of warning equivalent to whether the vehicle begins to drift off path, or is traveling too fast to negotiate an upcoming curve. Sensitivity can be altered in five distinct steps from "Mario Andretti" to "Your Mother." For example, if the car drifts over a dashed lane marker with no oncoming traffic, a yellow light on the instrument panel display illuminates at the same time the left side of the driver's seat begins to vibrate. Do the same with oncoming traffic or over a solid line, and the light turns to red, and a rumble strip sound appears on the side of the vehicle nearest the threat. This system disengages if the turn signal is engaged, the road is unpaved or has poor markings/badly defined edges, or speeds fall below 25 mph.
The curve warning system uses GPS data and high-resolution digital maps to determine current vehicle position, the most likely path, and the geometry of the road. A cautionary alert–one that suggests only slight braking is needed–also illuminates a yellow warning light, but vibrates the front of the driver's seat. An imminent alert (a high level of braking is needed) lights a large red icon and initiates a "Curve! Curve!" audio warning that will probably scare some passengers silly.
Three-hundred channels of data are collected every 1/10 of a second throughout the test period including: vehicle speed, lane position, lane and road edge location, objects around the vehicle, signals indicating the driver's actions, and the state of the vehicle. A data sample is sent by the on-board data acquisition system to the UMTRI facility in Ann Arbor, MI, via cellular modem each time the ignition is turned off so researchers can assess the system's operational state, and ensure that the vehicle isn't being abused. Driving subjects are equally divided male and female, and among the 20, 40, and 60 year-old age groups.
Delphi's Active Rear Steering
How do you achieve the couch-like comfort of a soft suspension setting and still maintain some ability to carve turns? Interestingly enough, the answer may be through active rear steering (ARS). Delphi Corp. has developed an ARS system that uses dynamic control algorithms to dial in desired handling characteristics by adjusting rear wheel angle independent of the suspension setting. John Martens, Delphi's project manager for ARS, says the system uses a yaw plane reference model similar to those of electronic stability control setups but adds a dynamic function that effectively reduces both understeer and oversteer at all speeds. The key component of the system is a low-cost, lightweight, electronically controlled modular actuator designed to work with a variety of existing suspension configurations. The actuator can adjust the angle of the rear wheels up to 3º, which doesn't sound like much, especially when compared to the 12º movement available with Delphi's QuadraSteer, but it has a marked effect on a vehicle's ability to successfully execute maneuvers like sudden high-speed lane changes. "There is a huge handling difference between cars with ARS and those without," says Dr. Jean Botti, chief technologist at Delphi's Innovation Center. And when linked with an existing brake-based stability control unit, Botti says that ARS can help reduce stopping distances on slippery surfaces, since drivers can maintain better control over the vehicle. Botti credits improvements in electronic controls and more sophisticated algorithms for Delphi's ability to bring ARS to market at a reasonable cost. "Progress in electronics have given this technology a quantum leap," he says. Delphi expects the system to be ready for the road beginning with model year 2009 vehicles.—KEW