SsangYong Actyon Sports II. Manual — part 153

11-7

4890-10

HECU (Hydraulic & Electronic Control Unit)

▶

to FL wheel

to RR wheel

to RL wheel

to FR wheel

Hydraulic & Electronic Control Unit (HECU)

1.

to master cylinder

11-8

1. OVERVIEW

The ESP (Electronic Stability Program) has been developed to help a driver avoid danger of losing

control of the vehicle stability due to understeer or oversteer during cornering. The yaw rate sensor,

lateral sensor and longitudinal sensor in the sensor cluster and the steering wheel angle sensor under

the steering column detect the vehicle conditions when the inner or outer wheels are spinning during

oversteer, understeer or cornering. The ESP ECU controls against oversteer or understeer during

cornering by controlling the vehicle stability using input values from these sensors and applying the

braking force to the corresponding wheels independently. The system also controls the engine power

right before the wheel spin synchronized to decelerate the vehicle automatically in order to maintain the

vehicle stable during cornering.

11-9

4890-10

ESP OFF switch

Located on the left side of
instrument panel.

Rear wheel speed sensor

Located on the both ends of
rear axle.

Front wheel speed sensor

Located on the hub assembly.

Sensor cluster

Located at the bottom of center
fascia panel.

Steering wheel angle sensor

Located on column shaft with
contact coil.

HECU assembly

Located near the brake booster
in engine compartment and
contains the pressure sensor.

2. COMPONENTS

11-10

3. FUNCTION

1) Term Definition

ABS: Anti-Lock Brake System

▶

When the brake pedal is abruptly depressed, the HECU calculates the slip ratio of each wheel based on

information received from the wheel speed sensors and controls the hydraulic module data quickly and

precisely in order to maintain the friction between the road surface and tire optimal (static friction).

Therefore, by keeping the friction between the road surface and tire optimal, it is possible to obtain

following effects: Enhanced steering stability, improved direction stability, reduced stopping distance and

etc.

EBD: Electronic brake-Force Distribution

▶

This is to detect the tire speed from the wheel speed sensor in order to supply the braking pressure to

the rear tires individually. In other words, the HECU measures the tire deceleration speed continuously

and controls the rear inlet valve on the hydraulic modulator to obtain optimal braking force as much as

possible. Thereby, stopping distance, braking effect and straight stability are improved.

ESP: Electronic Stability Program

▶

This is used to make the vehicle stabilized to recognize the emergency driving conditions, and to control

the brake for each wheels and the engine power when the brake system or acceleration will not work

any more in dangerous circumstances.

TCS: Traction Control System

▶

When the wheel is slipping due to an excessive engine torque while starting off or driving, this controls

the driving force (braking force + engine torque) in order to prevent the wheel from slipping through the

engine or brake control.

AYC: Active Yaw Control

▶

This has been developed to help a driver avoid danger of losing control of the vehicle stability due to

understeer or oversteer during cornering, which is a part of the ESP function.

HBA: Hydraulic Brake Assistant

▶

Developed based on the fact that elderly drivers depress the brake pedal too soft even when hard

braking is necessary, this an assist system to operate the HECU drive motor immediately and apply high

braking force to the wheels when the brake pedal is depressed softly and the vehicle should be braked

in emergency.

ARP: Active Rollover Protection

▶

This is a supplementary device for safety in ESP system and can help minimize the rollover accidents by

detecting a potential rollover situation through the brake and engine control when making sudden lane

change or turning sharply by adding only the software, without any separate device or switch.