BENDIX BW2842 Leaflet
electronics
TECHNICAL SPOTLIGHT - BENDIX
®
ESP
®
The Bendix
®
ESP
®
stability system, available on select coach
models, helps drivers maintain control of their vehicles during loss
of control, jackknife and rollover events by applying select brakes
and reducing throttle, slowing the vehicle down, and helping to
keep the driver in control. While much of the system utilizes
standard ABS brake components, such as wheel speed sensors,
modulators and an electronic control unit (ECU), there are a few
additional considerations technicians should keep in mind when
performing service on Bendix
®
ESP
®
-equipped vehicles.
How the Bendix
®
ESP
®
Stability System works.
Before a vehicle is delivered to a customer, a parameter set
tuned for the specific vehicle configuration is loaded into the ECU
along with the VIN at the OE factory. This “performance-tuning”
ensures optimal performance of the Bendix
®
ESP
®
system for
the specific vehicle configuration. It also means that the ECU
for that specific vehicle cannot be used in any other vehicle,
even if the configuration is the same. (Note: If the Bendix
®
ESP
®
ECU needs replacement, an ECU with the parameter set for that
specific vehicle identified by VIN needs to be ordered from the OE
factory. It is not possible to replace an EC-60
™
Advanced ECU
with one from another vehicle. The VIN on the ECU must match
the specific vehicle.)
Out on the road, the Bendix
®
ESP
®
ECU constantly compares
these known parameters to the vehicle’s actual movement, using
the wheel speed sensors of the ABS system, as well as lateral
acceleration, yaw rate, 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
automatically to assist the driver.
System intervention can vary, depending on the type of event.
In the case of a potential roll event, the system will override the
throttle and quickly apply brake pressure to slow the vehicle below
a critical threshold.
The Bendix
®
ESP
®
system goes further than roll stability-only
systems to help maintain vehicle control. The addition of the yaw
and steering angle sensors provide enhanced performance of the
system on slippery surfaces, such as rain-slicked, snow-covered
or icy pavement. In the case of vehicle slide, skid or spin (“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, thus applying a counter-force to better align the vehicle
with an appropriate path of travel. The system typically reacts
sooner than the driver could, but the driver always remains in
control and is able to apply additional braking pressure as needed.
Is the Bendix
®
ESP
®
stability system harder to repair or
maintain than standard ABS?
By utilizing the ABS brake system as a base, the core components
of the Bendix
®
ESP
®
system (wheel speed sensors, modulators,
traction, relays and ECUs) remain essentially the same. Your
current service procedures will be similar. The additional
components (yaw rate / lateral accelerometer, steering angle and
pressure sensors) are based on proven technology with millions
of miles in use. Repair to these sensors is limited to direct part
replacement and reconfiguration via Bendix
®
ACom
®
diagnostic
software.
If there is an issue with the stability system, the automatic traction
control (ATC) lamp or stability system lamp (ESP or ESC) will
remain lit. If the vehicle ABS system is also affected, both the
ABS warning lamp and the ATC or stability lamp will illuminate.
In these situations, the vehicle will have partial or no stability
function, but is still drivable and should be scheduled for service
as soon as possible.
Above image shows a vehicle on a test track in a potential
out-of-control scenario – on a slick surface (note the cones!)
With the Bendix
®
ESP
®
activated, the vehicle repeats the course
navigating the same manuever safely. (Note: In production, the
Bendix
®
ESP
®
system can not be turned off by the driver).