Connecting the Safety Dots

Feb. 22, 2005
This article explores active-passive integration approach (APIA) as a smart vehicle technology to avoid accidents and prevent injuries. By networking active and passive safety systems and integrating environmental sensors, this technology detects traffic hazards and determines the probability of an accident for the current traffic situation and, if necessary, initiates a staged hazard response to protect the occupants and other road users. In essence, it applies proactive vehicle intervention technology to prevent accidents from happening.

The best way to diminish injuries and fatalities is to avoid the crash in the first place. The technology to help avoid crashes exists today. In 2003 alone there were 6.3 million passenger vehicle crashes accounting for 2.9 million injuries and 42,643 fatalities according to the National Highway Transportation Safety Administration (NHTSA). Of these six million-plus crashes, 253,000 were rollovers causing almost 60,000 serious injuries. Keep in mind that 20% of all fatalities involve rollovers.

The U.S. Department of Transportation has set a goal to reduce the number of fatalities from 1.5 per million vehicle miles traveled to one million vehicle miles traveled by 2008. But if nothing changes in the way we view automotive safety, fatalities will actually increase by 50,000 per year according to the Department of Transportation. We must shift the paradigm to attain the goal.

Studies show that driver behavior remains the most critical challenge to enhancing road safety and is one of the roadblocks to reducing the number of driving fatalities. This is an important goal since society always benefits when our population stays healthy and productive. And an array of products have been developed that can help prevent many of these crashes from happening or mitigate serious injuries if a crash is unavoidable.

Preventive safety features Today, many leading automotive manufacturers recognize the importance of a new breed of safety features—features that prevent crashes and rollovers by anticipating a dangerous situation. Continental Automotive Systems has developed some of the most advanced active safety systems available today. These systems can intervene to keep a vehicle from sliding out of control, to stop more quickly in an unstable situation and keep the vehicle following the driver’s intended path. These systems include electronic stability control, traction control and anti-lock brakes. So, our engineers thought, “Why not use some teamwork to get even more out of these systems?”

Out of this thinking came a project that will change the way our industry looks at safety. The company is now developing a unique “central brain” that can monitor and connect a number of active and passive safety innovations under a single system, keeping all of these advanced technologies working in unison.

The project is known as active passive integration approach (APIA). You might say it totals more than the sum of its parts when working as a single system.

APIA approach The heart of the APIA system is the danger control module. This module is constantly fed information from environmental sensors and computes a hazard potential that reflects the current accident risk. APIA features the following elements: • integration of active and passive safety systems; • staged safety strategy in response to detected hazards; and • environmental sensing system to improve road safety and facilitate parking. Continental’s APIA system constantly receives input from multiple vehicle environment sensors, measuring a vehicle’s lateral, yaw, longitudinal and roll movements as it travels down the road (Figure 1). It can quickly determine if the vehicle is out of line with the driver’s intended direction. These vehicle environment sensors play a key role in the APIA system. APIA also reacts differently depending on the threat level. This could be compared to our Homeland Security warning levels. As the threat of a crash gets greater, APIA rapidly increases the response level of how it will help handle the impending event. For instance, it can trigger airbags just before an impact, allowing a fast, but softer and safer deployment. Normally, an airbag is deployed as the impact is happening.

If APIA detects a dangerous situation about to happen, it will initiate an appropriate staged hazard response to protect the vehicle’s occupants and other road users. Pre-crash sensors are constantly monitored and APIA can recognize and evaluate a dangerous situation or potential collision before it occurs. Then, passive restraint systems, such as airbags and seat belt tensioners, will activate according to need based on information from sensors. APIA is an intelligent umbrella system to help avoid injury through networking of active and passive safety systems.

The company engineers have succeeded in networking active and passive safety systems in an intelligent manner. This is achieved by linking the subsystems such as anti-lock brakes, occupant safety, environmental sensors and the steering. The overall idea is to avoid crashes and to prevent injury. The environmental sensors constantly analyze the traffic situation. If an impending hazard is detected, a finely staged response of safety measures will be initiated and adapted to the current crash risk. While safety features such as seat belts and airbags will continue to play an important role in keeping occupants safe, the number of crashes and injuries could be greatly reduced by the APIA system.

Safety features in today’s vehicles can be divided into two major categories—active and passive safety. APIA constantly monitors both areas. Active safety can be described as all measures to prevent a crash. Examples would include anti-lock braking, traction control and electronic stability control systems.

Passive safety can be described as all measures to protect occupants and other traffic participants against injuries caused by a crash. This could include structural crashworthiness, an energy-absorbent steering column, seat belts and airbags.

Continental’s APIA program links these and other systems electronically and uses environmental sensors to trigger one or more of them in to action. Both active and passive systems can work in tandem as needed.

For example, if your vehicle is closing too quickly on the car ahead, the APIA system would identify this as a dangerous situation and start preparing the vehicle in a number of ways to help you avoid a collision or, if necessary, prepare for one: • First, APIA provides force feedback in the accelerator pedal to let the driver know there is a potential safety issue ahead. This would also include a visual cockpit warning. • Then all windows and the sunroof are automatically closed. • It then would proceed to pre-fill the braking system for possible maximum use of the brakes. • The seat belts are tightened to reduce all slack. • Next, seat belt tensioners are activated to hold occupants firmly in their seats. • Power seats are then adjusted to an optimal safety position for the occupants. • APIA starts to brake automatically with up to a 0.3g deceleration. By this time, the driver has had time to apply heavy pressure to the brakes and the ABS system provides maximum anti-lock braking. Stability control is also activated when APIA determines it is necessary. APIA relies on environmental sensors, which are also used in adaptive cruise control in this situation, using radar or infrared solutions to measure the distance and closing rate between the two vehicles. It then chooses the appropriate level of actions and initiates them much faster and more accurately than could the vehicle’s driver. Currently, the company is also working on a pre-crash sensor called closing velocity (CV) (Figure 2). This highly dynamic sensor features a wide short-distance detection range and is ideal for detecting events in the vicinity of the vehicle. Its precise predictions of the severity and direction of an impending impact can also be used in combination with additional contact sensors in pedestrian protection systems. Image-processing camera systems will allow an even more dramatic improvement in safety. These systems will not only detect objects near to a vehicle but classify them as well. Safety systems can then be activated as appropriate for a given situation, providing even more effective protection for vehicle occupants and making active pedestrian protection systems a realistic prospect.

Electronic stability control APIA can also monitor a vehicle’s relationship with the road and identify an unstable or abnormal situation. If a vehicle enters a turn too quickly, APIA would prepare the occupants and vehicle for possible danger while taking pre-emptive action to avoid the loss of vehicle control. In this case, it would initiate the electronic stability control system to stabilize the vehicle plus other necessary systems, depending on the threat level.

Continental’s electronic stability control is an active safety system that identifies unstable driving situations quickly and applies automatic corrective action (Figure 3). It uses a combination of anti-lock brakes, electronic brake force distribution, traction control and active yaw control, applying braking pressure to individual wheels to help stabilize the vehicle and keep it from leaving the road.

ESC constantly evaluates measured data from numerous sensors and compares the driver’s input with the actual behavior of the vehicle. If it decides the driver is about to lose control of the vehicle, ESC intervenes by using engine electronics and the braking system to bring the car back under control.

Sensors For the best performance of electronic vehicle control systems, it is essential that movements and speeds, as well as physical forces acting on the vehicle, are monitored quickly and accurately. Our engineers have developed a full line of environmental sensors to keep the APIA module informed and, when necessary, direct one or more systems to take action. The sensors monitor movements including possible unwanted lane changes, blind spot detection and the closing rate between two vehicles. Sensors that recognize and evaluate a potential collision or crash make APIA possible. The lane departure warning system (LDW) will give an audio or visual warning to let a driver know that the vehicle is straying from a traffic lane (Figure 4). It uses a CMOS camera and an image-processing algorithm. The lane keeping system (LKS) actually takes an active role and when sensing a lane departure, provides a gentle steering deflection, suggesting a possible problem. The driver can easily override the system at any time.

Distance control is a system that helps to keep a safe distance between your vehicle and the one in front of you. Known as adaptive cruise control (ACC), this radar-based or infrared-based system was introduced into production by Continental in 1999. It uses the Pulse-Doppler principle for independent measurement of speed and distance and sharp beam focusing to separate objects. The system works equally well on open roads or in city traffic.

Pre-crash sensors recognize and evaluate a potential collision and immediately prepare the passive restraint systems including airbags and seat-belt tensioners. These will be activated according to need based on data from the sensors. Other interior sensors include seat occupation, weight sensors, airbag sensors, rollover sensing and sensing for pedestrian protection.

A fully functional APIA vehicle is currently being tested at Continental. After being test driven by customers and the press, the APIA–equipped vehicle has shown in real-world terms just how advanced and important this system can be to crash avoidance.

Future APIA The engineers are in the testing stages of ESC II, or Electronic Stability Control II. This next-generation system takes APIA and ESC a step further by monitoring active steering control and can be used with an active suspension to provide even more effective vehicle stability. This system is based on near-future products being produced by Continental and will begin showing up in next-generation vehicles.

The overall importance of APIA goes beyond just providing another stage in automotive safety. APIA provides a unique way of looking at how we approach vehicle safety, an approach that can help save lives by preventing crashes, or lessening the severity of a crash. This can mean improving the quality of life when a crash is avoided and ultimately helping to reduce insurance and medical costs to society. APIA shifts the paradigm and will change the way we look at all future automotive safety. Giving the driver the tools to avoid a crash altogether can improve everyone’s lives.

ABOUT THE AUTHOR Robert Arguelles is a chief engineer for electronic brake and safety systems at Continental Automotive Safety Systems in Auburn Hills, Mich.

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