ESP SSANGYONG NEW ACTYON SPORTS 2012 Repair Manual

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ESP controls during understeer ▶
The ESP system recognizes the directional angle with the steering wheel angle sensor and senses
the slipping route that occurs reversely against the vehicle cornering direction during understeer
with the yaw rate sensor and lateral sensor. Then, the ESP system applies the braking force to the
rear inner wheel to compensate the yaw moment value. In this way, the vehicle does not lose its
driving direction and the driver can steer the vehicle as intended.
(2) Over steering
What is oversteering? ▶
Oversteer is a term of a condition in which the steering wheel is steered to a certain angle during
driving and the rear tires slip outward losing traction.
Compared to understeering vehicles, it is hard to control the vehicle during cornering and the
vehicle can spin due to rear wheel moment when the rear tires lose traction and the vehicle speed
increases.
ESP controls during oversteer ▶
The ESP system recognizes the directional angle with the steering wheel angle sensor and
senses the slipping route that occurs towards the vehicle cornering direction during oversteer
with the yaw rate sensor and lateral sensor. Then the ESP system applies the braking force to the
front outer wheel to compensate the yaw moment value. In this way, the vehicle does not lose its
driving direction and the driver can steer the vehicle as intended.

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3) Vehicle Control During Cornering
The figure below shows the vehicle controls by the ESP system under various situations such as
when the brake pedal is depressed or not depressed during cornering, when the ABS is operating
and when braking without the ABS. It also includes the vehicle conditions when the TCS, a part of
the ESP system, is operating.
Condition Understeer control Oversteer control
Only ESP in
operation
No braking by driver
ESP
+
Normal braking
(no ABS operation)
ESP
+
ABS brake
ESP + ASR

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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 speedBrake 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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6. 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 ▶
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 ▶
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 ▶
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 ▶
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.

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2) DUMP (ESP is working) Mode
The pressure decreases just before the wheel speed drops and the wheels are locked.
The inlet valve closes and the outlet valve opens as in the ABS HECU and the oil is gathered at
the low pressure chamber while no additional oil is being supplied. Then the pump operates to
allow fast oil drainage. The shuttle valve and the separation valve do not operate while
decompression.

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3) HOLD (ESP is working) Mode
The Inlet valve and outlet valve will be closed to maintain the pressure in the hydraulic circuit
applied at the wheels. By closing the valves, the hydraulic pressure at the wheels will not be lost
or supplied any more. During ESP operation, the separation valve closes and only the shuttle valve
at the pump opens.

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4) RISE (ESP is working) Mode
The shuttle valve and inlet valve will be open and the separation valve and outlet valve will be
closed. Then, the pump is operated. When ESP operates while the ABS is operating, the
pressure will be increased continuously until just before the corresponding wheel gets locked.

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5) Hydraulic Circuit of HBA
The above figure shows one front and one rear wheel and the same hydraulic circuit forms as in
the ESP operation. When HECU recognizes that it is an emergency and it is required for hard
braking, depending on the pressure value of the brake pressure sensor and pressure changes
caused by the pressure sensor timing, it operates the pump immediately to apply the brake
pressure at the wheels. Then, the pressure in the pump increases until just before the
corresponding wheel gets locked. The motor still keeps rotating and the outlet valve and the
separation valve will stay closed. When the wheel starts to lock, the HBA function cancels and
switches to ABS operation.