The ESC-system uses several sensors in order to determine the state the driver wants the vehicle to be in (driver demand). Other sensors indicate the actual state of the vehicle (vehicle response). The control-algorithm compares both states and decides, when necessary, to adjust the dynamic state of the vehicle.
The sensors used for ESC have to send data at all time in order to detect possible defects as soon as possible. They have to be resistant to possible forms of interference (rain, holes in the road, etc.). Most important sensors are :
- Steering wheel sensor : determines the angle the driver wanted to take. This kind of sensor is often based on AMR-elements.
- Lateral acceleration sensor : often based on the Hall effect. Measures the lateral acceleration of the vehicle.
- Yaw sensor : measures the yaw angle (rotation) of the car. The achieved data of the yaw sensor can be compared with the data from the steering wheel sensor in order to take a regulating action.
- Wheel speed sensor : measures the wheel speed.
ESC uses an hydraulic modulator to assure that each wheel receives the correct brake force. A similar modulator is used in ABS. ABS needs to reduce pressure during braking, only. ESP additionally needs to increase pressure in certain situations.
The heart of the ESC-system is the ECU or Electronic Control Unit. The diverse control techniques are embedded in it. Often, the same ECU is used for diverse systems at the same time (ABS, Traction control, climate control, etc.). The input signals are sent through the input-circuit to the digital controller. The wanted vehicle state is determined based on the steering wheel angle,its gradient and the wheel speed. Simultaneously, the yaw sensor measures the actual state. The controller computes the needed brake or acceleration force for each wheel and directs via the driver circuits the valves of the hydraulic modulator. Via a CAN-interface the ECU is connected with other systems (ABS, etc.) in order to avoid giving contradictory commands.
Posted by: Raja Babu Dwivedy.
ID:4810750499.
Reference: http://en.wikipedia.org/wiki/Electronic_stability_control
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