Description and Operation

ESP Description

ESP recognizes critical driving conditions, such as panic reactions in hazardous situations, and stabilizes the vehicle by individual braking of the wheels and engine torque intervention. ESP adds an additional function known as Active Yaw Control (AYC) to the ABS, TCS, EBD and ESP 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. This is achieved by individual braking of the wheels and adapting the instantaneous engine torque without any action required by the driver. ESP essentially consists 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 ESP function in response to driver input. In the event of a stability control function failure, the basic safety function of the ABS remains available.

ESP Control Description: The ESP system includes the ABS/EBD, TCS and AYC functions. ABS/EBD function: The ECU converts the active sensor signal (current switching) from the four wheel sensors into a square wave. Using the above inputs, the ECU calculates vehicle speed and acceleration and deceleration from the four wheels, and decides whether to activate ABS/EBD or not. TCS function: Prevents wheel slip in the direction of travel by adding brake pressure reduction and reducing engine torque via the 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 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 ignition ON, the ECU continuously diagnoses system failures (self-diagnosis). If a system failure is detected, the ECU informs the driver through the BRAKE/ABS/ESP warning lamp (fail-safe warning).

Input and Output Diagram

ESP Operation Mode

1. 1
   STEP 1: ESP analyzes the driver's intention.

   

2. 2
   STEP 2: It analyzes the vehicle motion with ESP.

   

3. 3
   STEP 3: The HECU calculates the required strategy, then activates the appropriate valves and sends torque control requests via CAN to maintain vehicle stability.

   

ESP Hydraulic System Diagram

1. 1
   ESP Not Operating: Normal Braking.

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

2. 2
   ESP 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

   
   Warning Lamp Control

   

ABS Warning Lamp Module: The active ABS warning lamp module indicates the self-check and ABS fault status. The ABS warning lamp should 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.
• 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 self-check and EBD fault 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.
• The cluster lamp illuminates when communication with the CAN module is not possible.

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

• During the initialization phase after IGN ON (continuously for 3 seconds).
• When the ESP function is inhibited due to a system failure.
• When the ESP system 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.

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

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

ESP ON/OFF Switch (ESP System): The ESP ON/OFF switch is used to switch the ESP function between ON and OFF states based on driver input. The ON/OFF switch is a normally open momentary contact switch. When closed, the contacts switch the circuit to ignition. The initial state of the ESP function is ON, and the switch toggles the state.