ESC Description

The Electronic Stability Control (ESC) system recognizes critical driving conditions, such as panic reactions in hazardous situations, and stabilizes the vehicle by applying individual wheel braking and intervening in engine control. ESC adds an additional function to ABS known as Active Yaw Control (AYC). The ESC system includes the functions of TCS, EBD and ESC. While the ABS/TCS function controls wheel slip during braking and acceleration and thus mainly intervenes in the longitudinal dynamics of the vehicle, Active Yaw Control stabilizes the vehicle about its vertical axis. This is achieved by individually intervening in and adapting the wheel brakes and the instantaneous engine torque without any action required by the driver. ESC mainly consists of three components: sensors, electronic control unit, and actuators. The stability control function operates under all driving and operating conditions. Under certain driving conditions, the ABS/TCS function may be activated simultaneously with the ESC function in response to driver input. In the event of an ESC function failure, the basic safety function, ABS, is still maintained.

ESC Operation Description. The ESC system includes the ABS/EBD, TCS and AYC functions. ABS/EBD function: The ECU converts the active sensor signal (current switching) received from the four wheel sensors into a square wave. Using the above inputs, the ECU calculates the vehicle speed, acceleration and deceleration of the four wheels, and decides whether to activate ABS/EBD or not. TCS function: Prevents wheel slip in the driving direction by adding brake pressure and reducing engine torque via CAN bus. The TCS function uses the wheel speed sensor signal to detect wheel slip before the ABS function. AYC function: Prevents unstable vehicle maneuvering. To determine the vehicle maneuver, the AYC function uses signals from the maneuver sensors (yaw rate sensor, lateral acceleration sensor, steering wheel angle sensor). If the vehicle maneuver is unstable (oversteer or understeer), the AYC function applies brake pressure to a specific wheel and sends an engine torque reduction signal via CAN. After the ignition is turned on, the ECU continuously diagnoses system failures (self-diagnosis). If a system failure is detected, the ECU informs the driver of the system failure through the BRAKE/ABS/ESC warning lamp (fail-safe warning).

Input and Output Diagram