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.
DSC is, 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 curve).
- 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.
The ASC + T system will reduce engine output until the vehicle can move or or until 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 situation.
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.
Oversteer and Understeer:
- 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.
- The DSC's electronic and hydraulic systems are rapid and precise and they are hardly felt by the driver.
What is DSC?.....
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Originally Posted by Phil M
