Electronic stability control (ESC) has been compulsory on all passenger cars sold in Australia since 2013, but just what is ESC and how does it work?
ELECTRONIC STABILITY CONTROL goes by a number of different names, including electronic stability control (ESC), dynamic stability control (DSC) as well as Vehicle Stability Control (VSC) and many more.
The basic aim of ESP is to aid steering control rather than traction control which is a completely separate technology. That said, ESC grew out of both ABS and Traction Control and was developed, as the system we recognise today, by Bosch, and works in conjunction with both ABS and Traction Control.
According to legend Bosch worked to develop a system that was able to activate the ABS on individual wheels to maintain stability in ‘stability critical’ situations to ensure the driver was able to take evasive action via the steering wheel without overwhelming the tyres and either causing the vehicle to under- or oversteer.
Do all cars have ESC?
In 2013 it became mandatory for all passenger cars sold in Australia to have ESC or electronic stability control and in November last year (2015) it became compulsory for all light-commercial vehicles to have this life-saving technology.
Why should you care about ESC?
Well, if you’ve ever driven a car without ESC you’ll know just how valuable the system is. And especially so when you find you’ve got to brake and then steer around a car or an obstacle in front of you, or even make an emergency lane change without braking. In those situations, your car’s ESC or whatever the particular car maker chooses to call it, will do its best to ensure you don’t either plough straight ahead or flick the tail and tank-slap the obstacle when your yank on the wheel.
How does ESC work?
The primary aim of ESC is to monitor car motion “at any time”, according to the man credited with its development, Anton van Zanten who worked for Bosch in the 1970s, 80s and 90s – Bosch is credited with the mainstream development of ESC technology. “ABS works only during panic braking, not during coasting or partial braking or free rolling. And traction control usually works only if you have full acceleration,” van Zanten said. “But ESC controls car motion at any time.”
When van Zanten was developing ESC there was no way of measuring the yaw angle of the car when it was being turned hard. He suggested that the yaw sensor from a Cruise Missile at the time would have been perfect but cost thousands of dollars, so he built one for a few hundred bucks. Using that yaw sensor (which sits right in the middle of the car), and working in with ABS and traction control, ESC monitors wheel speed and yaw angle about 50 times a second. Using the ABS, ESC is able to brake an individual wheel or all four to maintain vehicle stability in a panic situation. By using ABS, the system is able to control the vehicle’s roll and slip, as well as wash off speed.
Anything else I need to know?
Many performance cars offer stages to their ESC systems which allow a little more slip, for driving on a racetrack, before the system cuts in. And some, allow for ESC to be completely disabled. The use of ESC on SUVs and 4x4s with their higher centre of gravity led to the development of roll mitigation and its incorporation into ESC, but that requires an explanation for another time.
Thanks – a useful explanation as always.
My motorbike has generation 9 of a Bosch system. Interestingly it was first released only with ABS and TC and a later software update provided Motorcycle Stability Control. It measures wheel speed, lean angle, pitch angle, acceleration, braking pressure and more.
Its TC is much quicker to kick in than that fitted to my 4WD. It can barely be felt. The bike has a lot of horses and these traction aids are literally a lifesaver esp when it’s ridden in the dirt. Loss of grip at either end can be catastrophic.