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Anti-lock Braking Systems, Electronic Traction Control and Crash Sensors


The electronic components of modern automobiles are developing at an astonishing rate. One of the main foci of development in new car technology is safety systems. New developments in anti-lock braking are making cars stop faster and in a more controlled manner, electronic traction control systems are keeping drivers safe on the road in even the most adverse conditions, and in the event of a collision, advancements in collision sensors coupled with new airbag technologies are saving lives.

Anti-Lock Braking Systems

A wheel that is revolving on a surface with a low coefficient of friction will slide under hard braking. A wheel that is not turning has a much lower coefficient of friction than does a moving wheel. Therefore a wheel that is no longer turning will take significantly more distance to bring the vehicle to a stop. An anti-lock braking system, or ABS, takes input from two or four wheels on the vehicle and uses that information to detect a skid. When a skid is about to occur, i.e. the wheels will lock and stop rolling causing the vehicle to loss significant amounts of traction, the system begins to rapidly release and engage braking to avoid a lock up.

Very quickly these systems grew in complexity to where they now can avoid a skid in the most adverse conditions by taking information from and sending signals to each wheel independently. Since being introduced in the late 1970's the ABS in vehicles has become much "smarter", utilizing advances in microprocessor design to make vehicles stop sooner and keep drivers and passengers safer. Intel, one of the leading manufactures of ABS control hardware, has developed a better solution for braking using fuzzy logic. By using fuzzy logic the new systems that Intel is producing can not only detect a lockup, but realize its magnitude and adapt for the future. Instead of a cause and effect (if...then) design, the system can respond across a gradient of inputs and field adaptive responses. Instead of just realizing a skid and avoiding it the system will be able to improve overall braking performance leading to better handling and a safer ride.

The algorithms that control the ABS are growing in complexity. With faster processors able to do large numbers of calculations in the time frame necessary to be effective, ABS can now take into account such minute details as the viscosity of the brake fluid and the weight distribution of the vehicle relative to its center of gravity. The original systems installed in vehicles could only detect a skid, unable to differentiate between locking wheels. Automobiles, starting with the 1992 Mitsubishi Gallant, employed solutions using advanced fuzzy logic which are still being advanced today, over a decade later.

Electronic Traction Control Systems

The development of traction control coincides with the development of ABS. In the mid-eighties the Robert Bosch Company took its designs for ABS and added more control mechanisms and sensors to produce a full-featured traction control system. A traction control system is the opposite of ABS in that it keeps the wheels from freely spinning under acceleration. The system takes information from the four wheels and in the most advanced four wheel drive vehicles is able to distribute power to the wheels that are getting traction. When a wheel is slipping to the point where it would cause instability, the system restricts the power flow to that wheel keeping the vehicle planted on the road, going in the direction the driver indents the vehicle to go. In the past, the system was able to retard the power flow by restricting spark timing by interfacing with the electronic distributor. Now power can even be controlled by the differentials giving true independent traction control at each, individual wheel.

Before the advent of electronic traction control there was only a driver's own skill to get him out of poor weather conditions. Today, with these new systems, drivers can operate their vehicles without worrying about getting traction. Safety has been increased dramatically reduction injuries from accidents caused by loss of traction. The systems are now advancing to the point where vehicles can be driven where it was once perilous to venture. Where ABS allows motorists to stop in low traction conditions, the traction control systems of today enable them to keep control as they accelerate from that stop.

Advanced Airbag Safety Systems

After the large scale deployment of seat belts there was a drastic decrease in fatalities from automotive crashes. Still, the interior of a modern automobile has many sharp objects and hard surfaces to injure a passenger in a collision even when buckled up. Safety was brought to a new level with the large scale use of airbags, now standard in all new vehicles. New systems use more sensors and microprocessor controllers to detect crashes and protect the individuals inside the vehicles from injury.

Crash sensors are at the heart of the system. For an accident to be detected and the airbags deployed at least two sensors must be tripped. This avoids accidental deployment which could lead to passenger injury. The sensors work by closing a circuit when the front of the sensor is compressed. The computer that controls these systems decides whether the impact meets the requirements to deploy the airbags and if met, it does. Newer systems check the weight of the passenger to see if she is large enough so as the impact of the airbag will not be more dangerous than the crash. The systems are moving towards more sensors and better controls to keep passengers safer. Sensors check not only the weight of the passengers, but also the distance from the dashboard and if the seat is even occupied.

Conclusions

While theses three systems are not perfect, they have increased the level of safety in passenger vehicles unimaginably in the past decade alone. In the future they promise to provide safe road travel in any conditions and in the event of a collision keep the passengers safe. None of these systems can replace smart decisions made by passengers and drivers a like, but they make the road safer for everyone.

The ABS coupled with the advanced traction control systems is a giant leap forward in automotive technology. They do not replace a system, but invent a whole new system that was not present before their invention. They keep the wheels independently on the road getting the car moving when the accelerator is depressed and bringing the vehicle to a stop when the brakes are applied regardless of the conditions. No system on any automobile prior to their invention could provide the amount of reassurance that these two control mechanisms provide.

The use of fuzzy logic to control the braking systems on an automobile is fascinating. So much information is gathered and so many variables are taken into account to provide even, controlled braking. The distance the developers have come in such a short time is astounding and the future is looking even more promising. The integration between the software, the hardware and the physical systems is impressive however complex.

References:
Fuzzy Anti-Lock Brake System Solution
(http://www.intel.com/design/mcs96/designex/2351.htm)
Airbags
(http://www.lemurzone.com/airbag/crash.htm)
Supplemental Restraint Systems)
(http://www.edmunds.com/ownership/safety/articles/46352/article.html)

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