| VERACRUZ(EN) >2008 > G 3.8 DOHC > Brake System > ESP(Electronic Stability Program) System>Description and Operation |
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Optimum driving safety
now has a name : ESC, the Electronic Stability Control.
ESC is based on the
MGH 40 ABS Hydraulic System. ESC 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 or the gas pedal.
ESC adds a further
function known as Active Yaw Control (AYC) to the ABS, TCS, EBD and EDC
functions. Whereas the ABS/TCS function controls wheel slip during braking
and acceleration and, thus, mainly intervenes in the longitudinal dynamics
of the vehicle, active yaw control stabilizes the vehicle about its
vertical axis.
This is achieved by
wheel individual brake intervention and adaptation of the momentary engine
torque with no need for any action to be taken by the driver.
ESC essentially
consists of three assemblies : the sensors, the electronic control unit
and the actuators.
The electronic control
unit incorporates the technological experience accumulated in connection
with the MGH 40 system, but has been substantially expanded in terms of
capacity and monitoring concept in order to permit the additional sensor
signals and arithmetic operations to be processed and converted into
corresponding valve, pump and engine control commands. Two 16-bit
processors and one 8-bit processor, which monitor each other, cooperate to
handle these requirements.
Of course, the
stability control feature works under all driving and operating
conditions. Under certain driving conditions, the ABS/TCS function can be
activated simultaneously with the ESC function in response to a command by
the driver.
In the event of a
failure of the stability control function, the basic safety function, ABS,
is still maintained.
DESCRIPTION
OF ESC CONTROL
ESC system includes
ABS/EBD, TCS and AYC function.
ABS/EBD function : The
ECU changes the active sensor signal (current shift) coming from the four
wheel sensors to the square wave.By using the input of above signals, the
ECU calculates the vehicle speed and the acceleration & deceleration
of the four wheels.And, the ECU judges whether the ABS/EBD should be
actuated or not.
TCS function prevents
the wheel slip of drive direction by adding the brake pressure and engine
torque reduction via CAN communication.TCS function uses the wheel speed
sensor signal to determine the wheel slip as far as ABS
function.
AYC function prevents
unstable maneuver of the vehicle. To determine the vehicle maneuver, AYC
function uses the maneuver sensor signals(Yaw Rate Sensor, Lateral
Acceleration Sensor, Steering Wheel Angle Sensor).If vehicle maneuver is
unstable (Over Steer or Under Steer), AYC function applies the brake
pressure on certain wheel, and send engine torque reduction signal by
CAN.
After the key-on, the
ECU continually diagnoses the system failure. (self-diagnosis)If the
system failure is detected, the ECU informs driver of the system failure
through the BRAKE/ABS/ESC warning lamp. (fail-safe warning)
INPUT
AND OUTPUT DIAGRAM
EBD
(ELECTRONIC BRAKE-FORCE DISTRIBUTION) OPERATION
The EBD system
(Electronic Brake force Distribution) as a sub-system of the ABS system is
to control the effective adhesion utilization by the rear
wheels.
It further utilizes
the efficiency of highly developed ABS equipment by controlling the slip
of the rear wheels in the partial braking range.
The brake force is
moved even closer to the optimum and controlled electronically, thus
dispensing with the need for the proportioning valve.
The proportioning
valve, because of a mechanical device, has limitations to achieve an ideal
brake force distribution tothe rear wheels as well as to carry out the
flexible brake force distribution proportioning to the vehicle load or
weight increasing. And in the event of malfunctioning, driver cannot
notice whether it fails or not.
EBD controlled by the
ABS Control Module, calculates the slip ratio of each wheel at all times
and controls the brake pressure of the rear wheels not to exceed that of
the front wheels.
If the EBD fails, the
EBD warning lamp (Parking brake lamp) lights up.
ADVANTAGES
Comparison
between Proportioning valve and EBD
ABS
CONTROL
ABS
HECU EXTERNAL DIAGRAM
HYDRAULIC
SYSTEM DIAGRAM
ABS
Warning Lamp module
The active ABS warning
lamp module indicates the self-test and failure status of the ABS .The ABS
warning lamp shall be on:
EBD/PARKING
BRAKE WARNING LAMP MODULE
The active EBD warning
lamp module indicates the self-test and failure status of the EBD.
However, in case the Parking Brake Switch is turned on, the EBD warning
lamp is always turned on regardless of EBD functions. The EBD warning lamp
shallbe on:
ESC
Warning Lamp (ESC system)
The ESC warning lamp
indicates the self-test and failure status of the ESC.
The ESC warning lamp
is turned on under the following conditions :
ESC
Function Lamp (ESC system)
The ESC function lamp
indicates the self-test and operating status of the ESC.
The ESC Function lamp
operates under the following conditions :
ESC
On/Off Switch (ESC system)
The ESC On/Off Switch
shall be used to toggle the ESC function between On/Off states based upon
driver input.
The On/Off switch
shall be a normally open, momentary contact switch.Closed contacts switch
the circuit to ignition.
Initial status of the
ESC function is on and switch toggle the
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