PREVOST LE MIRAGE XLII BUS SHELLS, Руководство по обслуживанию

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Section 12: BRAKE AND AIR SYSTEM
PA1564
31
30.2 6S/5M CONFIGURATION
Prévost vehicles utilize a 6S/5M configuration,
with the additional axle (rear tag axle) having
two sensors, but only one Pressure Modulator
Valve. In this case, the PMV controls both
wheels on the additional axle. The additional
axle wheels would receive equal brake
pressure, based on the wheel that is currently
experiencing the most wheel slip.
30.3 ADVANCED ABS WITH STABILITY
CONTROL
Overview
ESP stability system reduces the risk of
rollovers, jackknifing and other loss of control.
ESP features include Roll Stability Program
(RSP) and Yaw Control. During operation, the
ECU of the Bendix Advanced ABS system
constantly compares performance models to the
vehicle’s actual movement, using the wheel
speed sensors of the ABS system, as well as
lateral, yaw, and steering angle sensors. If the
vehicle shows a tendency to leave an
appropriate travel path, or if critical threshold
values are approached, the system will
intervene to assist the driver.
Roll Stability Program
Bendix RSP, an element of the overall ESP
system, addresses rollover conditions. In the
case of a potential roll event, the ECU will
override the throttle and quickly apply pressure
at all wheel ends to slow the vehicle combina-
tion. The level of braking application during an
RSP event will be proportional to roll risk.
Yaw Stability
Yaw stability counteracts the tendency of a
vehicle to spin about its vertical axis. During
operation, if the friction between the road
surface and the tires is not sufficient to oppose
lateral (side) forces, one or more of the tires can
slide, causing the vehicle to spin. These events
are referred to as either an “under-steer”
situation (where there is a lack of vehicle
response to steering input due to the slide on
the front axle) or an “over-steer” (where the
vehicle’s rear end slides out due to tire slide on
the rear axle) situation. Factors that influence
yaw stability are: wheelbase, suspension,
steering geometry, weight distribution front to
rear, and vehicle track width.
Yaw Control
Yaw Control corresponds to a wide range of low
to high friction surface scenarios including
rollover, jackknife and loss of control. It is the
recommended system for all power vehicles and
especially critical for vehicles pulling trailers. In
the case of vehicle slide (over-steer or under-
steer situations), the system will reduce the
throttle and then brake one or more of the “four
corners” of the vehicle (in addition to potentially
applying the trailer brakes), thus applying a
counter-force to better align the vehicle with an
appropriate path of travel.
For example, in an over-steer situation, the
system applies the “outside” front brake; while in
an under-steer condition, the “inside” rear brake
is applied.
DANGER
ESP may reduce the vehicle speed
automatically
.
ESP can make the vehicle decelerate
automatically. ESP can slow the vehicle with
or without the operator applying the brake,
and even when the throttle is being
applied.
30.4 BENDIX
®
SAS-60
TM
STEERING ANGLE
SENSOR
The Steering Angle Sensor (SAS) is used to
provide driver steering input to the controller. It
reports the steering wheel position to the
controller utilizing a dedicated serial communi-
cations link that is shared with the YAS-60
TM
sensor. The controller supplies the power and
ground inputs to the SAS-60
TM
sensor.
The SAS-60 TM sensor installed on Prevost
vehicles is the 90° connector.
30.4.1 Removal of the steering angle sensor
Service Checks:
1. Check all wiring and connectors. Some
installations also include an intermediate
connector from the steering angle sensor to
the main vehicle wire harness. Make sure all
connections are free from visible damage.
2. Examine the sensor. Make sure the sensor,
its mounting screws, and the interface
between the hub and the steering column
are not damaged.