Dynamic Stability Control (DSC) is a suspension control system which goes beyond the single components of Anti-lock Brake System
(ABS), Cornering Brake Control (CBC) and Automatic Stability Control +
Traction (ASC + T).
The steering wheel movement, vehicle speed, transverse acceleration and yaw are
all used by DSC to register imminent instability when cornering. DSC then intervenes via the
engine management system, reducing drive torque
and activating wheel brakes when necessary to keep the vehicle stable.
These events occur within milliseconds.
in fact, a further development of the ABS and ASC+T slip control systems.
While ASC + T analyzes the longitudinal forces occurring in straight-ahead
operation, DSC additionally registers and analyses lateral dynamic forces.
- When cornering at high speeds,
DSC counters unstable vehicle states such as oversteering (rear of car brakes into a slide towards the outside of the curve)
or understeering (front of car pushes towards the outside of the
DSC feature can provide maximum stability when cornering.
With DSC there is a significant reduction in the risk of skidding.
BMW's Dynamic Stability Control system has been
available on a variety of BMW models over the last three years. It is available on the new
3 Series sedan, the X5
and other models.
|Here's how it works:
DSC constantly compares
vehicle speed, wheel speed, steering angle, and yaw rate with a
benchmark of plausible and optimum driving conditions' data. In a fraction of a
second, DSC recognizes a threatening instability and a danger of skidding. The
DSC system can correct an unstable driving condition by applying precise
braking action to the individual wheels. As with ASC, DSC will if
necessary also cut back the engine speed to automatically stabilize the vehicle.
ASC + T system will reduce engine output until the vehicle can move or
acceleration can occur without the wheels spinning. If this reduction is
insufficient, each drive wheel is braked individually until both wheels have optimum traction.
This makes it possible to drive on snow, wet roads or other slippery grounds without the wheels spinning.
Even if the back wheels suddenly lose traction in a bend during
acceleration, ASC + T intervenes so quickly that the vehicle is stabilized before it can oversteer and swing out of the bend. The instrument console informs the driver of any control intervention and the relevant
The DSC computer constantly calculates an ideal driving condition that is compared with the current status. If the vehicle oversteers or
understeers, the calculated ideal deviates from the measured status,
and DSC will intervene within a few
milliseconds via the engine management system by reducing the engine torque and
applying the brakes on individual wheels where necessary.
DSC makes use of the ABS wheel-speed
sensors and the following additional components:
- steering angle sensor to detect the driver's chosen path.
- lateral-acceleration sensor to define the lateral forces which must be transmitted to the road by the tires.
- rate-of-turn sensor to define the vehicle's degree of rotary movement.
- brake-pressure sensor to define the longitudinal forces acting between tires and road surface under braking.
In the case of oversteer, DSC brakes the outer rear (and, if needed, the
outer front) wheel in order to correct the vehicle's stance by generating a counter-momentum to neutralize the
oversteer. The braking
effect is applied at both outer wheels.
- In the case of understeer, DSC acts upon the
inner rear (and, if needed, the inner front) wheel to regain vehicle stability.
The braking effect is applied at both inner wheels.
DSC's electronic and hydraulic systems are rapid and precise and they are hardly felt by the
ASC+T Explained also explains ABS.
ASC+T is a reprint from BMW
ASC+T Screensaver is a penguin trying to go up a hill. The penguin is unsuccessful at many tries and falls
on his back. He finally gives up and takes a BMW to go up the hill.