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Experiència: Review of driver assistance systems

Experiència: Review of driver assistance systems

mié, 08 oct 2008 09:50:00 +0200

Temps aproximat de lectura: 15 min.
Driver assistance systems use a combination of warnings and some degree of active intervention to help steer the driver away from trouble. Although the accent is on giving assistance to the driver rather than take control away, motorists are still wary about cars that supposedly drive themselves. While active intervention clearly holds many possibilities, it is also fraught with difficulty. Matthew Beecham considers some recent innovations and the issues they create.

It's a grim thought but, on average, someone dies every minute somewhere in the world as a result of a traffic accident. A number of manufacturers are pursuing the aim of reducing the frequency and severity of accidents by developing active and passive driving assistance systems. According to Bosch, driver assistance systems aim to make the vehicle capable of perceiving its surroundings, interpret them, identify critical situations, and assist the driver in performing driving maneuvers. The object is, at best, to prevent accidents completely and, at worst, to minimize the consequences of an accident for those concerned.

The continuous development of driver assistance systems is accompanied by the European Union's eSafety action programme for road safety which aims to halve the number of road fatalities by 2010. Driver assistance systems on the detection and analysis of the vehicle's surroundings will make a major contribution to the achievement of this aim. Investigations carried out by the German ministry of transport have shown that such systems can have a preventive influence on more than 50% of all accidents.

The most common suite of driver assistance technologies available today includes adaptive cruise control (ACC), lane departure warning systems, and parking assistance systems.

Adaptive cruise control

ACC has been under development in the EU since the Prometheus (Programme for European Transport with Highest Efficiency and Unprecedented Safety) programme began in 1986. However, the first commercially available system was not launched until 1998 in the Mercedes-Benz S-class. Known as the Distronic system (DTR) it was the first of a new generation of advanced driver that partially automates the driving task assistance devices to reach the market. The decision made by Mercedes-Benz to develop DTR was taken in 1995 following research activities that commenced from 1992. While DaimlerChrysler was the first to market with its ACC, other manufacturers were busy developing their own systems. Delphi's Forewarn system was applied to the Jaguar XKR in late 1999.

Today's ACC relies on radar or laser technology to track a vehicle ahead and maintain a safe gap. It lets the car hold a speed but adjusts to changing traffic conditions with automatic braking and acceleration. ACC is currently available on a wide range of vehicle models from the Renault Megane to BMW 7 Series.

Among those investing huge sums in developing driver assistance technology is Continental. "The recent merger with SiemensVDO complemented the vision of Continental to achieve a 360° perception of the environment," said Ms Amrei Drechsler, vice president, Advanced Driver Assistance Systems, Division Chassis & Safety, Business Unit Passive Safety & ADAS, Continental. "Thus we are able to offer almost every driver assistance system (i.e. ACC+Stop&Go, emergency brake assist, collision warning, lane departure warning, lane keeping, blind spot warning, lane change assist, enhanced night vision by camera controlled headlamps, speed limit monitoring, etc) all embedded in our ContiGuard strategy for greater driving comfort and safety. All these systems are already in or very close to series production. In 2008 we are going to launch completely new radar and infrared sensors as well as new camera systems, which are capable to run multiple driver assistance function (lane departure warning, speed limit monitoring, enhanced night vision by camera controlled headlamps) at the same time."

In a short space of time, Hella has also taken up a leading position in the still relatively young but very competitive market for driver assistance systems. The company has a very powerful technology portfolio which is being developed systematically with a special focus on camera sensor technology. During the past two years, the company launched production of a number of new products, including a lane change assistant on the basis of a 24 GHz radar sensor, a newly-developed rearview camera, and an ACC system with infrared lidar sensor technology. Further systems, such as the electronic parking assistant, alertness assistant as well as light-based and camera-based systems are in series development. More specifically, Hella's light-based driver assistance system includes adaptive and assistive light control on the basis of camera-based pedestrian and object detection. Hella's alertness assistant detects whether or not the driver is about to fall into a micro-sleep and warns him or her immediately. The camera-based driver assistance system detects the blink of the eyelid by means of a camera frontally placed in the steering wheel area and calculates, among other things, the eyelid blink frequency as well as the eyelid blink duration. If the eye stays closed for longer than a second when driving, the system warns the driver. Winfried Menge, director, marketing electronics, Hella KGaA Hueck & Co, said: "Our Alertness Assistant involves a camera mounted inside the car which monitors the driver. Although we do not yet a have a fixed date for its introduction, there is a very high level of interest from truck and carmakers. We are currently fine-tuning its functionality. As a camera can undertake a number of valuable and interesting features, the question becomes: what features must be in the first generation technology? We need to strike a balance between not adding too many yet just enough to justify the additional costs involved. We hope to bring the system into the market in 2010."

Lane departure warning

Lane departure warning alerts the driver when the car begins to leave its lane without obvious input from the driver (for instance, when the driver is distracted or is very tired). Currently available lane departure warning systems are forward-looking, vision-based systems that use algorithms to interpret video images to estimate vehicle state (lateral position, lateral velocity, heading) and roadway alignment (lane width, road curvature). A video camera in the rear view mirror (possibly integrated with the rain/light sensors) allows the electronics to track the lane markings on the road ahead. Using this video image, image processing software determines the car's position in the lane and then compares this position with additional inputs taken from the steering angle, brake and accelerator position sensors - and whether or not the indicators are in use. If the car begins to drift off track for no apparent reason, the driver is alerted by an audio or haptic warning such as a vibrating steering wheel.

Citroën was the first European carmaker to offer a lane departure warning system, using a Valeo-developed system on its C4 and C5 models. The so-called LaneVue system uses infra-red sensors to monitor white lines on the road. If the car begins to cross the lines without the indicators being used, the system vibrates the driver's seat strongly, mimicking the 'rumble strips' at the edge of some motorways. Today, a number of vehicle models have lane departure warning systems, ranging from the Citroën C4 to the Mercedes-Benz S-Class.

Among those developing lane departure warning systems is Hella. "We have the first contract for our front camera system and LDW will be one of the functions," said Menge. "An interesting focus today is on the fusion between functionality of the driver monitoring system and LDW system. So now we have a situation where we have two cameras in the car - one is looking at the driver and the other is looking at the road ahead. There is currently a focus in the industry on technology- and sensor fusion. One of the discussed applications is the fusion of Lane Departure Warning and Adaptive Cruise Control where both functions provide added value to the other and also enable new features. While the car now has a lot of information about its surroundings, there is a danger of over-loading the driver with too many warnings. As a consequence, he or she may over-react in certain driving situations. So another focus is to develop concepts how to match all the different available information and then decide on the most suitable HMI [Human Machine Interface] function to apply."

Last December, Schefenacker Plc was renamed Visiocorp Plc. The company designs and manufactures rearview mirrors and camera-based environmental sensor technologies. "Visiocorp's camera-based blind spot detection system on Volvo cars has been well received in the market," said Alf Liesener, marketing manager, Visiocorp plc. "The most significant advantage of our system compared to today's radar-based systems is that ours provides a warning at a speed of only 10 Km/h whereas radar-based systems typically start at 50-60 Km/h, which means they do not react in urban areas. Looking ahead, Visiocorp see a number of advantages of camera-based technology. Images allow interpretation and classification of any kind of object and road marking in the field of view. Combined with the latest development in intelligent image processing technology, this opens a number of potential new applications around the vehicle! As semiconductor technologies are being continuously improved, Visiocorp's engineers are investigating the advantages and opportunities for additional applications of a new generation of camera modules using latest technologies and components."

Parking assistance

Citroën C4 Picasso's is the world's first car to feature integrated parking space management. The parking space measurement system is based on the supplier's parking assistant, which helps drivers avoid shunting other cars and obstacles while parking. Besides the standard four ultrasound sensors on the vehicle front and rear, two extra sensors have been added for parking space management, one on either side of the front bumper. Parking space management is activated by a button on the steering wheel. The system establishes which side the space is on by identifying which turn signal is in use. While driving past - at a speed of up to 20 km/h - the sensor then gauges the space. The assistant indicates to the driver via the central display whether the gap is big enough for the car, a tight squeeze, or simply too small. The same visual and acoustic signals that feature in the parking assistant then warn the driver of any obstacles. The system also works for parking spaces on a slight curve. The system is being supplied by Bosch.

Hella's electronic parking assistant is planned to be rolled out next year. "The roll-out phase will start next year. Given that we already have some 6 - 8 sensors embedded around the car that can identify at low vehicle speed the vehicle's immediate scenery, we can use that technology to move beyond thoughts of simple 'parking' to 'maneuvering'," added Menge. "The question then becomes: how can we add functionality without adding more sensors? How can we add functionality to support the driver when he or she is maneuvering the car? These and other questions form an important focus of our current research."

Tomorrow's car

All these driver assistance technologies are at various stages of development but their adoption will depend on acceptance by both consumers and governments. Is there a danger that some drivers will actually drive faster or pay less attention to the possibility of a hazard ahead if they have faith that a gadget will alert them if needed? Liesener points out that there have been always discussions about gadgets that offer more safety. "Seat belts, for example, are clearly regarded as safety systems as they can save lives in the event of an accident. But some people might feel safer wearing seat belts and, for this reason, drive faster. We think these discussions are very important to better understand the consequences of introducing new features and identify solutions to avoid negative side effects. For example, by locating the warning lights of the blind spot detection system at certain spots nearby or on the exterior mirrors, our system prompts the drivers to turn and actually pay attention to the mirrors. We have received feedback that our blind spot detection systems even trained people to pay more attention to the blind spot zones, because the systems continuously indicated hazardous situations which they would not have been aware of without such as system."

Could car navigation systems play an important role in detecting vehicle-surrounding conditions?

"Not only could they, but they probably should, and the sooner the better," said Ido Amir, marketing manager, Mobileye Vision Technologies. "No in-vehicle sensor can see what is not in their line of sight! For example, driving around the bend and straight into a line of cars that have rear ended each other is not going to be solved by anything that is not able to see what's happening beyond the next curve you are approaching. For this, intelligent traffic systems that have 'eyes from above', are a feasible, and an excellent solution. Naturally, a better-connected road scene (WiFi, Bluetooth, or some other type of wireless communication) would make a huge difference in road safety. Terrible accidents that occur in tunnels, sometimes involving tens of vehicles, and always deadly, can be prevented altogether, if all cars 'know' that one car is now stuck in the tunnel ahead." For some time, Mobileye has been pushing back the technical boundaries of vision systems for intelligent transportation. Its technologies are sourced by a number of automakers, including BMW, GM and Volvo.

Predicting which electronic systems will we consider common in five, 10 or 15 years, Yasuo Yoshikawa, project leader of Technology Planning Department, Denso Corp, said: "We think that parking assist system in five years, full speed range adaptive cruise control system in ten years, and road-to-vehicle and vehicle-to-vehicle communication systems in 15 years will become common."

Liesener believes that rearview cameras and other camera applications for commercial vehicles and trucks, distance control/pre crash systems for upper price segments, and lane change assist in upper price segments will become commonplace. He said: "Sensor fusions or better sensor data fusion will happen which results in a reduction of electronic units but an increase of safety and performance."

For retrofit applications, Amir reports that Mobileye's future pedestrian detection technology, blind spot detection and lane change assistance, automatic high-beam control, side-looking and rear-looking cameras are all in store as next generation aftermarket products.

Drechsler reckons that in five years, emergency brake assist and lane departure warning in trucks will be commonplace while in the 10 - 15 year timeframe, emergency brake assist in passenger cars will be typical.

For many years, industrialists and academics have discussed the possibility of 'accident-free driving'. While we are still some way off from achieving this state, could assistance functions result from the close networking of both active and passive safety systems with predictive driver assistance systems? "We believe that accidents will gradually be reduced with the introduction of driver assistance systems," said Yoshikawa. "However, to realize an accident-free driving, improvement in driving manners and traffic environment will also be needed."
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