Description and Operation

ESC Description

Optimum driving safety now has a name: ESC, Electronic Stability Program. ESC recognizes critical driving conditions, such as panic reactions in dangerous situations, and stabilizes the vehicle by individual wheel braking and intervention in engine control without the need to press the brake or accelerator pedal. ESC adds an additional function known as Active Yaw Control (AYC) to the functions of ABS, 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 individual wheel braking and adaptation of the instantaneous engine torque, without any action required by the driver. ESC consists mainly of three units: 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 commands. In the event of a failure of the stability control function, the basic safety function, ABS, continues to operate.

ESC Control Description The ESC system includes the ABS/EBD, TCS and AYC (Active Yaw Control) functions. ABS/EBD function: The ECU converts the active sensor signal (current offset) received from the four wheel sensors into a square waveform. Using the input of these signals, the ECU calculates vehicle speed and the acceleration and deceleration of the four wheels. The ECU determines whether the ABS/EBD system should be activated or not. TCS function prevents wheel slip in the direction of travel by adding brake pressure and reducing engine torque via CAN communication. TCS uses the wheel speed sensor signal to determine wheel slip, as with the ABS function. 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 the specific wheel and sends an engine torque reduction signal via CAN. After the ignition is turned on, the ECU continuously diagnoses the system for malfunctions (self-diagnosis). If a system malfunction 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

Cruise Control Operating Mode

1. 1
   STEP 1 ESC analyzes the driver's intentions.

   

2. 2
   STEP 2 ESC analyzes the vehicle's movement.

   

3. 3
   STEP 3: The HECU calculates the required strategy, then activates the corresponding valves and sends torque control requests via CAN to maintain vehicle stability.
4. 4
   ESC not operating - normal braking.

   	Inlet Valve (IV)	Outlet Valve (OV)	Traction Control Valve (TCV)	High Pressure Switching Valve (HSV)	Return Pump
   Normal Braking	Open	Close	Open	Close	OFF

   
   

   

   IV: Inlet Valve OV: Outlet Valve RL: Rear Left Wheel FR: Front Right Wheel FL: Front Left Wheel RR: Rear Right Wheel RP: Return Pump TCV: Traction Control Valve HSV: High Pressure Switching Valve

5. 5
   ESC Pressure Increase Mode

   	Inlet Valve (IV)	Outlet Valve (OV)	Traction Control Valve (TCV)	High Pressure Switching Valve (HSV)	Return Pump
   Normal Braking	Open	Close	Closed (Partially)	Open	ON (engine speed control)

   
   

   

   IV: Inlet Valve OV: Outlet Valve RL: Rear Left Wheel FR: Front Right Wheel FL: Front Left Wheel RR: Rear Right Wheel RP: Return Pump TCV: Traction Control Valve HSV: High Pressure Switching Valve

6. 6
   ESC Pressure Hold Mode (controlled only for FR)

   	Inlet Valve (IV)	Outlet Valve (OV)	Traction Control Valve (TCV)	High Pressure Switching Valve (HSV)	Return Pump
   Normal Braking	Close	Close	Closed (Partially)	Open	OFF

   
   

   

   IV: Inlet Valve OV: Outlet Valve RL: Rear Left Wheel FR: Front Right Wheel FL: Front Left Wheel RR: Rear Right Wheel RP: Return Pump TCV: Traction Control Valve HSV: High Pressure Switching Valve

7. 7
   ESC Pressure Decrease Mode (controlled only for FR)

   	Inlet Valve (IV)	Outlet Valve (OV)	Traction Control Valve (TCV)	High Pressure Switching Valve (HSV)	Return Pump
   Normal Braking	Close	Open	Closed (Partially)	Open	ON (low engine speed control)

   
   

   

   IV: Inlet Valve OV: Outlet Valve RL: Rear Left Wheel FR: Front Right Wheel FL: Front Left Wheel RR: Rear Right Wheel RP: Return Pump TCV: Traction Control Valve HSV: High Pressure Switching Valve

Cruise Control Operating Mode

[Supervision]

[General]

ABS Warning Lamp: The active ABS warning lamp indicates the self-check and fault status of the ABS. The ABS warning lamp shall illuminate:

• 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.

EBD/Parking Brake Warning Lamp The EBD warning lamp indicates the EBD self-check and malfunction status. However, if the parking brake switch is ON, the EBD warning lamp always illuminates regardless of EBD function. The EBD warning lamp should illuminate:

• 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.

ESC Function/Warning Lamp (ESC System) The ESC function/warning lamp indicates the ESC self-check and malfunction status. The ESC function/warning lamp operates under the following conditions:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• In case of ESC function failure during braking.
• In diagnostic mode.
• When ESC control is operating. (Flashing - 2 Hz)

ESC OFF Lamp (ESC System) The ESC OFF lamp indicates the ESC self-check and operating status. The ESC OFF lamp illuminates under the following conditions:

• During the initialization phase after IGN ON (continuously for 3 seconds).
• When the driver turns the ESC function off using the switch.

ESC On/Off Switch (ESC System) The ESC On/Off switch is used to switch the ESC function between On and Off states according to the driver's actions. The On/Off switch must be a normally open momentary contact switch. The initial state of the ESC function is On, and the switch is used to request a change of the ESC state.