operators_manual

A Real World Example of How the
System Operates
Excessive speed for road conditions
creates forces that exceed the threshold at
which a vehicle is likely to roll over on a
higher-friction surface. The system
automatically reduces engine torque and
applies the service brakes (based on the
projected rollover risk) to reduce the
vehicle speed, thereby reducing the
tendency to roll over
.
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 truck/
tractor to spin. These yaw events are
referred to as either "under-steer" (where
there is a lack of vehicle response to
steering input due to tire slide on the steer
axle) or "over-steer" (where the tractor's
rear end slides out due to tire slide on the
rear axle) situation. Generally, shorter
wheelbase vehicles (tractors, for instance)
have less natural yaw stability, while longer
wheelbase vehicles (straight trucks, for
instance) have greater natural yaw stability.
Factors that influence yaw stability are:
wheelbase, suspension, steering geometry,
weight distribution front to rear
, and vehicle
track width.
Yaw Control
Yaw Control responds to a wide range of
low- to high-friction surface scenarios
including rollover, jackknife and loss of
control. In the case of vehicle slide (over-
steer or understeer 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.
A Real World Example of How Yaw
Control Operates
Excessive speed exceeds the threshold,
creating a situation where a vehicle is likely
to spin and, where applicable, jackknife.
The system reduces engine throttle and
selectively applies brakes to reduce the
vehicle speed, thereby reducing the
tendency to jackknife.
Automatic Traction Control
Your truck/tractor ABS has an automatic
traction control (A
TC) feature. This feature
is controlled by a switch. This feature is
monitored by a warning lamp located on
the switch. The Traction Control warning
lamp will briefly illuminate and then go out
when the ignition switch is first turned on.
The traction control warning lamp will
illuminate whenever the ATC system
detects drive wheel spin. The lamp will
remain illuminated as long as wheel spin is
detected and the ATC system is applying
the drive wheel brakes or reducing engine
torque. Engine torque or vehicle speed
should be reduced to eliminate wheel spin
and prevent excessive application of the
ATC system.
Except for checking for proper illumination
of the ABS and traction control warning
lamps when first starting the vehicle, and
for monitoring these lamps while driving,
no special operating procedures are
required. For detailed system description,
see literature for your specific ABS that
was provided with your vehicle.
DRIVING - Brakes
118 Y53-6096-1C1 (09/20)
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