SsangYong Rodius (2013 year). Manual — part 165
09-13
4891-01
2) Operation of ESP System
(1) Under steering
What is understeering?
▶
ESP controls during understeer
▶
Understeer is a term for a condition in which 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 understeer. It is because that the vehicle can return back to inside of cornering
line when the steering wheel is steered toward the inside even when the front wheels are 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.
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.
09-14
(2) Over steering
What is oversteering?
▶
ESP controls during oversteer
▶
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.
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.
09-15
4891-01
(3) ESP Control
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.
09-16
(4) 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.
Item
Understeer control
Oversteer control
Only ESP in
operation
No braking by
driver
ESP
+
Normal braking
(no ABS operation)
ESP
+
ABS brake
ESP + TCS
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