Description and Operation

ESC Description

ESC recognizes critical driving conditions, such as panic reaction in hazardous situations, and stabilizes the vehicle by braking and intervening in steering and engine control. ESC adds an additional function known as Active Yaw Control (AYC) to the ABS, TCS, EBD and ESC functions. 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. Stability is achieved by braking individual wheels and adapting 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 in 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 a stability control function failure, the basic safety function, ABS, continues to operate.

ESC Control Description: The ESC system includes ABS/EBD, TCS and AYC functions. ABS/EBD Function: The ECU converts the active sensor signal (current shift) received from the four wheel sensors into a square wave. Using the input signals above, the ECU calculates the vehicle speed and the acceleration and deceleration of the four wheels. The ECU then determines whether to activate ABS/EBD or not. The TCS function prevents wheel slip in the direction of travel by adding brake pressure and reducing engine torque via CAN communication. The TCS function uses the wheel speed sensor signal to determine wheel slip, together with the ABS function. The AYC function prevents unstable vehicle maneuvering. To determine the vehicle maneuver, the AYC function uses the maneuver sensor signals (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 the system for failures (self-diagnosis). If a system failure is detected, the ECU informs the driver of the system failure via the BRAKE/ABS/ESC warning lamp (fail-safe warning).

Input and Output Diagram

Cruise Control Operating Mode

ESC Hydraulic Circuit Diagram

1. 1
   ESC Does Not Operate: Normal Braking.

   Solenoid valve	Continuity	Valve	Motor Pump	TC Valve
   IN (NO)	OFF	OPEN	OFF	OFF
   OUT (NC)	OFF	CLOSE

2. 2
   Cruise Control Operation

   Solenoid valve		Continuity	Valve	Motor Pump	TC Valve
   Understeer (Inside Rear Wheel Only)	IN (NO)	OFF	OPEN	ON	ON
   	OUT (NC)	OFF	CLOSE
   Oversteer (Outside Front Wheel Only)	IN (NO)	OFF	OPEN
   	OUT (NC)	OFF	CLOSE

   
   

   

ABS Warning Lamp Module: The active ABS warning lamp module indicates the ABS self-check and fault status. The ABS warning lamp shall illuminate under the following conditions:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• In case of ABS operation failure during braking.
• In diagnostic mode.
• When the ECU connector is disconnected from the ECU.
• The cluster lamp illuminates when communication with the CAN module is not possible.

EBD/Parking Brake Warning Lamp Module: The active EBD warning lamp module indicates the EBD self-check and fault status. However, if the parking brake switch is ON, the EBD warning lamp always illuminates regardless of the EBD function. The EBD warning lamp shall illuminate under the following conditions:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• When the parking brake switch is on or the brake fluid level is low.
• When the EBD function has failed.
• In diagnostic mode.
• When the ECU connector is disconnected from the ECU.
• The cluster lamp illuminates when communication with the CAN module is not possible.

ESC Function / Warning Lamp: The ESC function/warning lamp indicates the ESC self-check and fault status. The ESC function/warning lamp illuminates under the following conditions:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• When the ESC function is inhibited due to a system failure.
• When ESC control is operating. (Flashing - 2 Hz)
• In diagnostic mode (other than standard mode).
• The cluster lamp illuminates when communication with the CAN module is not possible.

ESC Off Lamp: The ESC OFF lamp indicates the ESC self-check and operating status. The ESC OFF lamp operates under the following conditions:

• In the initialization mode after IGN ON (continuously for 3 seconds).
• The ESC OFF lamp illuminates when the driver presses the ESC OFF button.

ESC On/Off Switch: The ESC On/Off switch shall be used to switch the ESC function between ON and OFF states depending on driver action. The On/Off switch shall be a normally open momentary contact switch. Closed contacts switch the circuit to ignition. The initial state of the ESC function is ON, and the switch toggles between ON and OFF states.