User's Manual

13
Bendix
®
Roll Stability Program (RSP
®
)
Bendix RSP — an element of the overall Bendix
®
ESP
®
system with the EC‑80
™
Controller — addresses rollover
conditions. In the case of a potential roll event, the ECU
will override the throttle and quickly apply brake pressure
at all wheel ends to slow the vehicle combination. The
level of braking application during an RSP event will be
proportional to roll risk. See Figure 12.
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 sufcient
to oppose lateral (side) forces — one or more of the tires
can slide, causing the truck/tractor 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
tire slide on the steer axle), or an "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 inuence 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. It is the recommended system for all
power vehicles and especially critical for tractors 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. (See Figure 13)
IMPORTANT SAFETY INFORMATION
ABOUT THE BENDIX
®
ESP
®
SYSTEM
The Bendix ESP EC-80 Controller may reduce
the vehicle speed automatically.
The Bendix
®
ESP
®
system can make the
vehicle decelerate automatically and can
slow the vehicle with or without the operator
applying the brake — and even when the
throttle is being applied.
To minimize unexpected deceleration and reduce the
risk of a collision, the operator must:
• Avoid aggressive driving maneuvers, such as sharp
turns or abrupt lane changes at high speeds, which
might trigger the stability system; and
• Always operate the vehicle safely, drive defensively,
anticipate obstacles and pay attention to road,
weather and trafc conditions. Bendix ABS, ATC
and ESP systems are no substitute for prudent,
careful driving.
Towing Doubles Or Triples May Reduce The
Effectiveness Of Stability Systems
The Bendix ESP system with the EC-80 Controller is
designed and optimized for trucks and for tractors that
tow single trailers. If a tractor equipped with Bendix
ESP is used to power multiple trailer combinations
(known as “doubles” or “triples”) the effectiveness
of the Bendix ESP system may be greatly reduced.
Extremely careful driving is always required when
towing doubles or triples. Excessive speed and
aggressive maneuvers — such as sharp turns, sudden
steering inputs, or abrupt lane changes — should be
avoided.
Limitations Of Stability Systems
The effectiveness of the Bendix ESP system with the
EC‑80 Controller may be greatly reduced if:
• The load shifts due to improper retention, accident
damage, or the inherently mobile nature of some loads
(for example, hanging meat, live animals or partially
laden tankers),
• The vehicle has an unusually high — or off‑set — center
of gravity (CG),
• One side of the vehicle drops off the pavement at an
angle that is too large to be counteracted by a reduction
in speed,
• The vehicle is used to haul double or triple trailer
combinations,
• If very rapid steering changes are attempted at high
speeds,
• There are mechanical problems with suspension
leveling of the tractor or trailer resulting in uneven loads,
• The vehicle is maneuvering on a high banked road
creating either additional side forces due to the weight
(mass) of the vehicle, or a deviation between expected
& actual yaw rates,
• Gusty winds are strong enough to cause signicant
side forces on the vehicle and any towed vehicles.