0-7
ESP SYSTEM
RODIUS 2006.09
4892-01
Over steeringOversteering 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 moment when the
rear tires lose traction and the vehicle speed
increases.
ESP controls during oversteering
The ESP system recognizes the directional
angle with the steering wheel angle senso
r
and senses the slipping route that occurs
towards the vehicle cornering direction
during oversteering with the yaw rate senso
r
and the lateral 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.
2) 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 malfunction of a system o
r
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.
0-5
POWER STEERING SYSTEM
RODIUS 2006.09
4610-00
4. OVERVIEW
The power steering system consists of pump, oil reservoir, rack and pinion gear. The power
steering pump is a vane type and delivers hydraulic pressure to operate the power steering
system. The pressure relief valve in pump controls the discharging pressure.
The rotary valve in rack and pinion gear directs the oil from the power steering pump to one
side of rack piston.
The integrated rack piston converts the hydraulic pressure to linear movement.
The operating force of rack moves the wheels through tie rod, tie rod end and steering knuckle.
Even though the hydraulic pressure cannot be generated, a driver can steer the vehicle without
power assist but it needs very high steering force.
In this case, the operating force of steering wheel is conveyed to pinion, and the movement o
f
pinion moves the rack through pinion gear combined to rack gear.
5. COMPONENTS
