Auto Electronics

Making the Active and Passive Safety Connection

Among the new frontiers being enabled by rapid advancements in electronics is the ability to link onboard active and passive vehicle safety systems. This important evolution is already under way and will continue to accelerate resulting in enhanced safety, comfort and convenience for drivers and passengers.

While an active system assists drivers in potentially avoiding or mitigating the effects of an accident, passive safety systems help to protect drivers and passengers when an event is unavoidable.

Until recently, these safety paths have rarely crossed, being pursued as advancements in separate chassis or occupant safety systems. But as a profusion of sensors, accelerometers, transmitters and electronic control units are placed within the vehicle dedicated to separate systems, TRW researchers and engineers are exploring the opportunities to integrate active and passive safety processing units and share the ever-increasing data available by using common network architectures. A primary example of the integration of active and passive safety technologies is TRW’s Active Control Retractor (ACR) seat belt system, a featured component of the Mercedes “Pre-Safe” system on the S-Class. This system uses inputs from the active safety systems such as the yaw rate sensor in the electronic stability control system to sense when the vehicle is sliding or skidding sideways at the limits of vehicle control. It can also sense panic braking inputs monitored by the vehicles brake assist system to sense the potential for an impending collision. If a threshold is crossed, an electric motor in the seat belt system helps remove the slack from the belt, and helps position the occupant in relation to the onboard safety systems before the event occurs. If the event is avoided, the ACR simply resets itself after five seconds.

Another important area of functionality being enabled by electronics are active systems based on video and radar, referred to as driver assist systems (DAS) such as the adaptive cruise control systems now available on a number of higher-end luxury cars. While mostly convenience-based today, these systems will expand into the safety arena and enable systems such as lane departure warning, lane keeping, blind spot detection, automatic emergency braking and more. One possible active/passive combination is using the onboard radar system to detect a vehicle or object approaching too quickly and activate the active control retractor seat belts to help better position the occupant for a potential collision.

In the passive safety arena, developments in vision-based occupant sensing offer truly exciting advancements and possibilities. These systems can achieve what passive systems such as weight-based systems cannot—the ability to know what is truly in the vehicle cabin and seats, and moreover, the position of body parts like the head in relation to an airbag enclosure. Thus, an airbag deployment can be customized to the occupant, and avoided altogether in the case of small children or out-of-position adult passengers.

Beyond this ability, the camera systems could be used for a myriad of possibilities such as child passenger abandonment, security from intrusion, recording of accidents and more. One active passive safety integration opportunity is detection of drowsy drivers whereby the interior camera can monitor the driver’s eyes and head position while the active safety systems can monitor steering and gas pedal inputs. If the driver is exhibiting drowsy behavior, a haptic signal such as a steering wheel vibration, tightening of the seat belt through the ACR, or a loud warning through the stereo system could be activated. This is only the beginning, but the future is closer than you might think. Automakers like Toyota already sell highly advanced models like the Crown Majesta, which feature some of these advancements. By the end of the decade, the integration of active and passive safety systems enabled by electronics systems will be helping to create a “safety umbrella” dedicated to assisting the avoidance of accidents and to enhancing occupant protection if the accident is unavoidable.

ABOUT THE AUTHOR As executive vice president for Sales and Business Development at TRW Automotive, Peter Lake is responsible for sales, product strategy, business development and marketing on a global basis. Lake is a 25-year veteran of the company.

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