SsangYong Stavic / SsangYong Rodius (2005 year). Manual - part 410

ABS/ESP SYSTEM

STAVIC - 2004.09

CHANGED BY

EFFECTIVE DATE

AFFECTED VIN

Understeering

Understeering is when the steering wheel is steered to a
certain angle during driving and the front tires slip toward
the reverse direction of the desired direction. Generally,
vehicles are designed to have under steering. The vehicle
can return back to inside of cornering line when the steer-
ing wheel is steered toward the inside even when the ve-
hicle front is slipped outward. As the centrifugal force
increases, the tires can easily lose the traction and the
vehicle tends to slip outward when the curve angle gets
bigger and the speed increases.

Oversteering

Oversteering is when the steering wheel is steered to a
certain angle during driving and the rear tires slip outward
losing traction. When compared with under steering
vehicles, the controlling of the vehicle is difficult during
cornering and the vehicle can spin due to rear wheel mo-
ment when the rear tires lose traction and the vehicle speed
increases.

Under steering

Over steering

ESP SYSTEM

1. GENERAL INFORMATION

Principle of ESP

ESP (Electronic Stability Program) 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. This system is developed to help the driver avoid the danger of losing the control of the vehicle stability due to
under-steering or over-steering 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 spin present at any wheels during over-steering, under-steering or cornering. The
ESP ECU controls against over-steering or under-steering during cornering by controlling the vehicle stability using the
input values from the sensors and applying the brakes independently to the corresponding wheels.

The system also controls during cornering by detecting the moment right before the spin and automatically limiting the
engine output (coupled with the ASR system).

Without

ESP

Braking force

Desired

course

Compen-

sating yaw

moment

Braked

wheel

With ESP

Braking force

Without

ESP

Desired

course

Braked

wheel

Compen-

sating yaw

moment

With ESP

ABS/ESP SYSTEM

STAVIC - 2004.09

CHANGED BY

EFFECTIVE DATE

AFFECTED VIN

ESP controls during under steering

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 direc-
tion during understeering with the yaw rate sensor and the
lateral sensor. Then the ESP system applies the brake at
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 driver intends.

ESP controls during oversteering

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 oversteering with the yaw rate sensor and the lat-
eral sensor. Then the ESP system applies the brake at
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 he or she intends.

ESP Control

The ESP system includes the ABS/EBD and ASR systems allowing the system to be able to operate depending to the
vehicle driving conditions. For example, when the brakes are applied during cornering at the speed of 100 km/h, the ABS
system will operate at the same time the ASR or ABD systems operate to reduce the power from the slipping wheel. And
when yaw rate sensor detects the rate exceeding 4¡Æ/seconds, the ESP system is activated to apply the brake force
to the corresponding wheel to compensate the yaw moment with the vehicle stability control function. When various
systems operate simultaneously under a certain situation, there may be vehicle control problems due to internal mal-
function of a system or simultaneous operations. In order to compensate to this problem, the ESP system sets the
priority among systems. The system operates in the order of TCS (ASR or ABD), ESP and ABS. The order may be
changed depending on the vehicle driving situations and driving conditions. As the single-track vehicle model used for
the calculations is only valid for a vehicle moving forward, ESP intervention never takes place during backup.

Turning

Operating

range

ESP

ABS/ESP SYSTEM

STAVIC - 2004.09

CHANGED BY

EFFECTIVE DATE

AFFECTED VIN

Vehicle Control During Cornering

The figure below shows the vehicle controls by ESP system under various situations such as when the brake pedal is
pressed (or not pressed) during cornering and when the ABS is operating or when just the conventional brake is operat-
ing during braking. It also includes the vehicle conditions when the TCS that is included in the ESP system is operating.

Only ESP operating

No braking by driver

Understeering Control

Oversteering Control

ESP

Conventional

brake

(ABS not operating)

ESP

ABS brake

ESP

ASR

ESP auto brake

Engine

control

Engine

control

: Service brake

ESP auto brake

2 : ABS operation

1 : The slip occurs

under ESP
operation

1 : The slip occurs

under ESP
operation

2 : ASR operation

ESP auto brake

: Service brake

2 : ASR operation

2 : ABS operation

1 : The slip occurs

under ESP operation

ESP auto brake

(none ABS)

Operations

1 : The slip occurs

under ESP operation

ABS/ESP SYSTEM

STAVIC - 2004.09

CHANGED BY

EFFECTIVE DATE

AFFECTED VIN

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 emer-
gency 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.

Deceleration

Time (s)

Elderly and physically

weak drivers

Experienced drivers

Inexperienced drivers

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