1. Hydraulic unit with attached fect sensors). Both measure the
wheel speed in a contact-free
control unit
way via magnetic fields. NowThe hydraulic unit executes adays active sensors are mostthe commands from the con- ly employed. They can identify
trol unit and regulates, via so- both the direction of rotation
lenoid valves, the pressure in and the standstill of a wheel.
the wheel brakes. The hydraulic
modulator is the hydraulic con- 3. Steering-angle sensor
nection between the master
cylinder and the wheel cylin- The task of the steering-angle
ders. It is located in the engine sensor is to measure the pocompartment. The control unit sition of the steering wheel
takes over the electrical and by determining the steering
electronic tasks as well as all angle. From the steering ancontrol functions of the system. gle, the vehicle speed and the
desired braking pressure or
the position of the accelerator
2. Wheel-speed sensor
pedal, the driving intention of
The control unit uses the sig- the driver is calculated (desired
nals from the wheel-speed sen- state).
sors to compute the speed of
the wheels. Two different oper- 4. Yaw-rate and lateralating principles are used: pas- acceleration sensor
sive and active wheel-speed
sensors (Inductive and Hall-ef- A yaw-rate sensor registers all
The United States requiring ESC for all passenger
vehicles under 10,000
pounds (4536 kg), phasing
in the regulation starting
42 driverlifestyle.com
the movements of the vehicle
around its vertical axis. In combination with the integrated
lateral-acceleration sensor, the
status of the vehicle (actual
state) can be determined and
compared with the driver’s intention.
5. Communication with engine
management
Via the data bus, the ESP control unit is able to communicate
with the engine control unit. In
this way, the engine torque can
be reduced if the driver accelerates too much in certain driving
situations. Similarly, it can compensate for excessive slip of the
driven wheels provoked by the
engine drag torque.
with 55% of 2009 models
(effective 1 September
2008), 75% of 2010 models,
95% of 2011 models, and
all 2012 models.