Electronic systems play a huge role in helping drivers avoid accidents and provide protection if one occurs. Here is a rundown of active and passive automotive safety systems.
The field of automotive safety was essentially born in 1911 when Henry Leland replaced the hand crank used to start the vehicle with a new electric starter after his wife's friend was killed trying to start the car. Since then safety glass, bumpers, safety belts, crumple zones, and airbags have all been introduced with the aim of keeping the occupants safe during and after a crash.
Recently, with advances in electronic technologies, automobile engineers are developing new ways to protect occupants and people outside the vehicle. This "safety cocoon" is becoming more effective and encompasses more features. This article and its follow-on will identify the types of technologies being developed, how these systems work, and the social forces pushing the drive for safer vehicles.
Automotive engineers speak of two types of safety—active and passive. Active safety describes any technology applied to avoid accidents. Passive safety refers to protecting vehicle occupants during and after an accident. Although the technology in these active and passive safety systems isn't totally electronic, much of the new developments are.
Active safety technology may be as simple as improving tires and suspension systems, or as complex as creating a complete vehicle dynamics and stability system combined with a by-wire system. The figure below illustrates the different classifications of active safety and their authority with respect to the level of driver control. The size of the circles indicates how relatively effective the technology is in avoiding accidents.
During normal operation, the driver is in almost complete control of the vehicle, and the safety systems remain in the background. The first classification of systems—audio and visual warnings—are intended to warn the driver that a potentially unsafe condition exists. The types of warnings that exist, and the complexity required to implement them can be ranked into three levels:
Simple: Warnings that are simple to implement include door and tailgate ajar, driver seatbelt unlatched, and outside air temperature decreasing (possible icing condition). Simple warnings are usually implemented with a switch or sensor. If failures of these systems occur, the failure may be annoying to car occupants but not life threatening—as long as occupants still remember to put on their seat belts. Although many of these warnings have been around for a while, the category is still expanding. For example, today the seat-belt reminder is for the front-seat passengers only. However, both European and U.S. regulatory agencies are actively adding requirements for rear-seat passenger warnings as well.
Moderate: These include low tire-pressure warnings and back-up aids that sound if something is behind the vehicle when backing up. Implementing these warnings requires slightly more complex electronics and usually multiple sensors. System diagnostics also become more complex, because a failure of the sensors may cause harm to the occupants of the vehicle or others outside the vehicle. These failures must be diagnosed and the driver immediately warned that the system is inoperable and requires immediate repair.
Complex: Intricate alerts include lane change and departure warnings, precrash detection and distance monitoring, blind-spot warnings, and real-time automatic route guidance (telematics on steroids). Implementing these warnings usually requires complex sensor systems working with other vehicle or external systems. Because they're constantly working to identify hazardous conditions that need either immediate or timely attention, these systems usually require complex computations using a microcontroller or DSP. Diagnostics become extremely complicated with these warnings, because failure to warn the driver can cause an accident.
When any of the above warnings occur, the driver is still in control of the vehicle. Many times, the driver will automatically take some action to respond to or correct the warning, such as stop the vehicle, slow down, or undertake evasive action to avoid the accident.