SsangYong Actyon Sports II. Manual - part 156

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4890-10

4) HBA (Hydraulic Brake Assist System)

(1)  Purpose  

HBA (Hydraulic Brake Assist) system helps in an emergency braking situation when the driver applies 

the brake fast, but not with sufficient pressure, which leads to dangerously long braking distance. ECU 

recognizes the attempt at full braking and transmits the signal calling for full brake pressure from the 

hydraulic booster. An inexperienced, elderly or physically weak driver may suffer from the accident by not 

fully pressing the brake pedal when hard braking is required under emergency. The HBA System 

increases the braking force under urgent situations to enhance the inputted braking force from the driver. 

Based on the fact that some drivers depress the brake pedal too soft even under when hard braking is 

necessary, the HECU system is a safety supplementary system that builds high braking force during 

initial braking according to pressure value of the brake pressure sensor and the pressure changes of the 

pressure sensor intervals. When the system is designed to apply high braking force when brake pedal is 

depressed softly by an elderly or physically weak driver, the vehicle will make abrupt stopping under 

normal braking situation due to high braking pressure at each wheels.

(2) Operation

The brake pressure value and the changed value of the pressure sensor are the conditions in which the 

HBA System operates. There are 2 pressure sensors under the master cylinder. When the ESP ECU 

system determines that emergency braking is present, the pump operates, the brake fluid in the master 

cylinder is sent to the pump and the braking pressure is delivered to the wheels via the inlet valves . If the 

drive depress the brake pedal slowly, the pressure change is not high. In this case, only the conventional 

brake system with booster is activated.

(3) Operating conditions

Sensor pressure: over 40 bar

Pressure changes: over 850 bar/sec

Vehicle speed: over 30 km/h

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5) ARP (Active Roll-Over Protection

The ARP (Active Roll-over Protection) system is a safety assistant device that minimizes, by controlling 

brakes and the engine, the physical tendency of the vehicle rollover during sharp lane changes or U-

turns. For the system, software is added to the existing ESP system and no additional device or switch is 

needed. One must note that the ARP system, just as general assistant devices including the ABS, is only 

a safety assistant device using the ESP system and its function is useless when the situation overcomes 

the physical power. Following picture shows how the ARP compensates the vehicle position by varying 

each wheel's braking power to overcome the physical tendency of the vehicle rollover during sharp turns.

Lateral sensor

(In sensor cluster)

Vehicle speed

Brake force

Radius

The vehicle driving condition is controlled by the internally programmed logic according to the input 

signals from wheel speed sensor, steering angle sensor and lateral sensor.

During the ARP operation, vehicle safety (rollover prevention) takes the first priority and thus, stronger 

engine control is in effect. Consequently, the vehicle speed decreases rapidly, so the driver must take 

caution for the vehicle may drift away from the lane.

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4890-10

7. HYDRAULIC CIRCUIT OF ESP

MCP: Master Cylinder Primary

MCS: Master Cylinder Secondary

ESV: Electric Shuttle Valve

NO: Normal Open

NC: Normal Close

LPA: Low Pressure Accumulator

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Circuit description

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When compared to the vehicle equipped with ABS/EBD only, the internal hydraulic circuit has a 

normally-open separation valve and a shuttle valve in primary circuit and in secondary circuit. 

When the vehicle brakes are not applied during engine running or when applying the non-ABS operating 

brakes, the normally-open separation valve and the inlet valve are open, whereas the normally-closed 

shuttle valve and the outlet valve are closed. 

When the ESP system is operating, the normally-open separation valve will be closed by the solenoid 

valve operation and the hydraulic circuit will be established by the shuttle valve. Then, the inlet and outlet 

valves will be closed or open depending on the braking pressure RISE, HOLD or DUMP conditions.

Flashing warning lamp and warning sound during ESP operation

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When the ESP operates while the vehicle is moving, the ESP warning lamp on the instrument panel 

flickers and the buzzer sounds at every 0.1 second. The ESP lamp operation is to inform a driver that the 

vehicle is extremely unstable. 

The ESP system is just a supplementary system for the vehicle and it cannot control the vehicle over the 

physical limit. Do not solely rely on the system but be advised to drive the vehicle safely.

Drive feeling during ESP operation

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When the ESP system activates, the driving feeling can be different depending on vehicle driving 

conditions. For example, it will feel different when the ESP system is activated while the ABS is operated 

by depressing the brake pedal and when the ESP system is in control without the brake pedal 

depressed on the same curve. 

If the ESP system operates with the brake applied, the brake pressure will be increased on the 

corresponding wheel which already has braking pressure for the ESP controls. In other words, the ESP 

system would make the driver feel more abruptly braked compared to the situation that the braking 

pressure is applied to wheel which had no braking force.

Noise and vibration that driver senses during ESP operation

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The ESP system may transfer noise and vibration to a driver due to the pressure changes caused by the 

motor and valve operations in a very short period of time. 

Extreme cornering will trigger the ESP operation and this will make the driver sense noise and vibration 

due to sudden brake application. 

Also, the ESP system controls the engine power. Therefore, the driver may notice the engine power 

decreases even when the accelerator pedal is depressed.