Description and Operation

ESP Description

Optimal driving safety now has a name: ESP, Electronic Stability Program. ESP recognizes critical driving conditions, such as panic reactions in dangerous situations, and stabilizes the vehicle by individually braking the wheels and intervening in engine torque without the driver needing to operate the brake or accelerator pedal. 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 individually braking the wheels and adapting the instantaneous engine torque without any action required from the driver. ESP essentially consists of three units: sensors, electronic control unit and actuators. The stability control function operates under all driving modes and operating conditions. Under certain driving conditions, the ABS/TCS function may be activated simultaneously with the ESP function at the driver's command. 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 ABS/EBD, TCS and AYC (Active Yaw Control) functions. ABS/EBD function: The ECU converts the active sensor signals (current switching) received from the four wheel sensors into a square wave form. Using the input of the above signals, the ECU calculates the vehicle speed and the acceleration and deceleration of the four wheels. The ECU determines whether the ABS/EBD system should operate or not. The TCS function prevents wheel slip in the direction of travel by reducing brake pressure and engine torque via CAN communication. The TCS function uses the wheel speed sensor signal to determine wheel slip before the ABS function. The 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 the ignition is turned ON, the ECU continuously diagnoses system malfunctions (self-diagnosis). If a system malfunction 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.

   

4. 4
   ESP Not Operating: Normal Braking

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

5. 5
   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

ESP Operation Mode

[Supervision]

[General]

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

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

• 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.

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

• During the initialization phase after IGN ON (continuously for 3 seconds).
• When ESP function is suppressed due to a failure.
• In diagnostic mode.
• When the ESP system is operating (flashing - 2 Hz).

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

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

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 must be a normally open momentary contact switch. The initial state of the ESP function is On, and the switch is used to request a change in ESP status.