Electronic Stability Program (ESP) is a closed-loop vehicle control system that prevents vehicle lateral instability. It is integrated with the vehicle’s brakes and drivetrain. In contrast to ABS, which prevents wheel lockup when braking, and TCS, which prevents spinning of the driven wheels, ESP prevents the vehicle from “pushing out” of the turn or spinning out when it is steered.
Aside from the benefits inherent in ABS and TCS, ESP improves active driving safety in the following ways:
- Provides active support for the driver, regardless of lateral dynamic challenges.
- Provides enhanced stability and tracking performance even in limited situations, such as full braking, partial braking, coasting, accelerating, engine drag, and load shifting.
- Stabilizes directional control even during extreme steering manoeuvres (panic reactions), reducing the danger of skidding dramatically.
- This improved handling behaviour applies even in limit situations. The drivers’ (or passengers’) experience allows them to predict the vehicle’s behaviour even in a critical traffic situation.
- If ABS and TCS intervene, there can be even better utilization of the friction potential between the tires and the road, resulting in improved traction and stopping distances as well as improved steering stability.
Electronic Stability Program (ESP) for passenger cars
ESP utilizes this tire characteristic to effect servo-control for vehicle handling. A safe track of the vehicle is essential for good vehicle handling since it corresponds as closely as possible to the course of the steering angle as shown in the figure below curve 2. During steering maneuvers, this is the case if the tire lateral forces stay significantly below the friction potential. With ESP, though, the yaw rate is simply controlled based on the steering angle, resulting in an unstabilized vehicle as shown in curve 3 below.
This means that the ESP controls both the yaw rate and the sideslip angle of the vehicle. This vehicle-handling control is not limited to ABS and TCS/MSR operations, but also extends to the area where the vehicle is free to roll and can also be used for partial braking if the vehicle is moving at the physical limits.