Electronic Stability Program (ESP)

What is Electronic Stability Program (ESP)?
It is an active safety system in the early year vehicles and a lot more effective then ABS and TCS. This uses an extra electronic control to operate the brakes, in conjunction with ABS just to provide vehicle stability this is applied during the cornering. ABS has the illigibilty to sense the need of brake to be applied or to release the brake on each wheel and this is where the ESP makes use of this facility. In the simple terms the comparison of an electronic stability program (ESP) with the other ssytems is that the anti-lock braking system (ABS) prevents the wheels from locking and skidding and the traction control system (TCS) prevents the wheels from spinning during the snowy and dry road conditions whereby the electronic stability control (ESP)provides steering stability and also it can stabilise steering by intervention in two diferent ways firstly by braking selected wheels, or by acclerating the driving wheels which helps the vehicle to be stable on the road.

The parts and sensors Electronic Stability Program (ESP) has and there Functions:

1. Yaw sensor - this detects any tendency for the vehicle to rotate about its axis. It also detects any sideways movement (lateral acceleration) of the vehicle.


2. Steering wheel angle sensor - this registers the turning angle of the steering wheel. It provides an input from the driver that indicates the direction in which the vehicle is intended to be steered.


3. Pressure sensor - this sensor monitors the brake pressure in the system as applied by the driver.


4. Wheel sensors - these signals the wheels speed.
   
5. Hydraulic modulator - this is responsible for applying the brakes and controlling the brake pressure.


6. Brakes - these are selectively applied by the hydraulic modulator.


7. PCM - this engine control module is directed to control the engine functions.


8. Ignition timing - controlled by the PCM the ignition timing is retarded to reduce engine torque.


9. Fuel injection - also controlled by the PCM, injection is reduced to decrease engine torque.


10. Throttle valve - this is closed to reduce engine torque, also controlled by the PCM.

Vehicle Stability

It is the direction in which the vehicle is travelling and therefore controlled as far as possible by the ESP. Mostly the vehicle's travel in the direction at which the driver controls the steering. Sometimes the other forces can also be taken over and the direction may change compared to the desired direction. There are three types of axes vertical axis, transverse axis and the longitudinal axis at which the movement can occur.

Conditions that Influence Vehicle Operation

1. Centrifugal force - this is an outward force on curves that increase with speed. It can cause lateral instability and produce an overturning force.
2. Weather conditions - poor conditions reduce visibility and create slippery road surfaces. Side winds can cause lateral in stability.
3. Road surfaces - various types of road surfaces have the different frictional affect on the tyres. This can be affect the braking, tarction, side slip while cornering.
4. Driver fatigue - causes drowsiness and slow reactions.
5. Load conditions - force and vehicle stability will be different with light and heavy load.

Understeer and Oversteer

Understeer relates to the vehicle's tendency to steer wide on corners. The front of the vehicle tends to slip more than rear therefore to be in the control the driver have to steer more into the curve for the vehicle to maintain its desired track whereas the oversteer the vehicle's rear end tends to swing wide on the corners and so the driver have to steer to a lesser degree on a curve for the vehicle to remain on track.

Vehicle's with and without ESP.

With the ESP the brakes are automatically applied to help in steering in the right direction. The right-front brake is applied on a left bend so that the vehicle is in the centre of the lane then the left-front brake is a applied on right bend so that the vehicle is in the right direction and keeps the vehicle in regular track whereas without ESP if you driving fast at the corners the vehicle maybe out off the road because the front of the car is steered into curve and rear tends to follow up therefore correction might fail and loose track of the road.