Esc (Electronic Stability Control): Overview Kia Optima II

DESCRIPTION

Optimum driving safety now has a name: ESC, the Electronic Stability Control.

ESC is based on the MGH 25 ABS Hydraulic System. ESC recognizes critical driving conditions, such as panic reactions in dangerous situations, and stabilizes the vehicle by wheel-individual braking and engine control intervention with no need for actuating the brake or the gas pedal.

ESC adds a further function known as Active Yaw Control (AYC) to the ABS, TCS, EBD and EDC functions. Whereas 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 wheel individual brake intervention and adaptation of the momentary engine torque with no need for any action to be taken by the driver.

ESC essentially consists of three assemblies: the sensors, the electronic control unit and the actuators.

The electronic control unit incorporates the technological experience accumulated in connection with the MGH 25 system, but has been substantially expanded in terms of capacity and monitoring concept in order to permit the additional sensor signals and arithmetic operations to be processed and converted into corresponding valve, pump and engine control commands. Two 16-bit processors and one 8-bit processor, which monitor each other, cooperate to handle these requirements.

Of course, the stability control feature works under all driving and operating conditions. Under certain driving conditions, the ABS/TCS function can be activated simultaneously with the ESC function in response to a command by the driver.

In the event of a failure of the stability control function, the basic safety function, ABS, is still maintained.

Scheme 85

DESCRIPTION OF ESC CONTROL

ESC system includes ABS/EBD, TCS and AYC function.

ABS/EBD function: The ECU changes the active sensor signal (current shift) coming from the four wheel sensors to the square wave. By using the input of above signals, the ECU calculates the vehicle speed and the acceleration & deceleration of the four wheels and, the ECU judges whether the ABS/EBD should be actuated or not.

TCS function prevents the wheel slip of drive direction by adding the brake pressure and engine torque reduction via CAN communication. TCS function uses the wheel speed sensor signal to determine the wheel slip as far as ABS function.

AYC function prevents unstable maneuver of the vehicle. To determine the vehicle maneuver, AYC function uses the maneuver sensor signals (Yaw Rate Sensor, Lateral Acceleration Sensor, Steering Wheel Angle Sensor). If vehicle maneuver is unstable (Over Steer or Under Steer), AYC function applies the brake pressure on certain wheel, and send engine torque reduction signal by CAN.

After the key-on, the ECU continually diagnoses the system failure. (self-diagnosis) If the system failure is detected, the ECU informs driver of the system failure through the BRAKE/ABS/ESC warning lamp. (fail-safe warning)

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1. ESC Non-operation: Normal braking. SOLENOID VALVE CONTINUITY SPECIFICATIONS Solenoid valve Continuity Valve Motor pump TC Valve IN (NO) OFF OPEN OFF OFF OUT (NC) OFF CLOSE
2. ESC operation SOLENOID VALVE CONTINUITY SPECIFICATIONS Solenoid valve Continuity Valve Motor pump TC Valve Understeering (Only inside of rear wheel) IN (NO) OFF OPEN ON ON OUT (NC) OFF CLOSE Oversteering (Only outside of front wheel) IN (NO) OFF OPEN OUT (NC) OFF CLOSE

Scheme 90

The active ABS warning lamp module indicates the self-test and failure status of the ABS. The ABS warning lamp shall be on

1. During the initialization phase after IGN ON. (continuously 3 seconds).
2. In the event of inhibition of ABS functions by failure.
3. During diagnostic mode.
4. When the ECU Connector is separated from ECU.

The pressure sensor (A) is connected to the master cylinder, when ESC is on operation, detecting the brake pressure in order to sense the user's braking intent. The pressure sensor (A) consists of two ceramic discs, one is fixed and the other movable, so that changes in pressure will modify the distance between the discs. (Max. measurable pressure is 200bar.)

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1. The ESC OFF switch is for the user to turn off the ESC system.
2. The ESC OFF lamp is on when ESC OFF switch is engaged.

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1. Remove the ESC OFF switch from the switch panel on the center cover of the floor console assembly.
2. Check the continuity between the switch terminals as the ESC OFF switch is engaged.

The steering angle speed sensor detects the angle of the steering wheel in order to which direction a user chooses. The sensor is detached on the MPS (Multifunction Switch) under the steering wheel.