Bendix Commercial Vehicle Systems EC-60 ESP CONTROLLERS ADV - Manual (Page 10)

10
Steer Axle Control
Although both wheels of the steer axle have their own wheel
speed sensor and pressure modulator valve, the Bendix
EC-60 controller blends the applied braking force between
the two steering axle brakes. This Bendix patented brake
application control, called Modified Individual Regulation
(MIR), is designed to help reduce steering wheel pull
during an ABS event on road surfaces with poor traction
(or areas of poor traction, e.g. asphalt road surfaces with
patches of ice).
Single Drive Axle Control (4x2 Vehicle)
For vehicles with a single rear drive axle (4x2), the brakes
are operated independently by the Bendix EC-60 controller,
based on the individual wheel behavior.
Dual Drive Axle Control (4S/4M Configuration)
For vehicles with dual drive axles (6x4) using a 4S/4M
configuration, one ABS modulator controls both right-side
rear wheels and the other modulator controls both left-side
rear wheels. Both wheels on each side receive equal
brake pressure during an ABS stop. The rear wheel speed
sensors must be installed on the axle with the lightest load.
Dual Rear Axle Control (6S/6M Configuration)
For vehicles with dual rear axles (6x4, 6x2) using a 6S/6M
configuration, the rear wheels are controlled independently.
Therefore, brake application pressure at each wheel is
adjusted according to the individual wheel behavior on
the road surface.
6x2 Vehicles with 6S/5M Configuration
6x2 vehicles can utilize a 6S/5M configuration, with the
additional axle (a non-driven rear 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.
Normal Braking
During normal braking, brake pressure is delivered through
the ABS PMV and into the brake chamber. If the ECU
does not detect excessive wheel slip, it will not activate
ABS control, and normal vehicle service braking is applied.
Retarder Brake System Control
On surfaces with low traction, application of the retarder can
lead to high levels of wheel slip at the drive axle wheels,
which can adversely affect vehicle stability.
To prevent this, the Bendix
® EC-60 ™ controller switches
off the retarder as soon as a lock-up is detected at one (or
more) of the drive axle wheels.
When the ECU is placed in the ABS off-road mode (on
vehicles equipped with this optional feature), it will switch
off the retarder only when ABS is active on a steer axle
wheel and a drive axle wheel.
Optional ABS Off-Road Mode
On some road conditions, particularly when the driving
surface is soft, the stopping distance with conventional
ABS may be longer than without ABS. This can occur
when a locked wheel on soft ground or loose gravel plows
up the road surface in front of the tire, changing the rolling
friction value. Although vehicle stopping distance with a
locked wheel (in the absence of ABS) may be shorter than
corresponding stopping distance with conventional ABS
control, vehicle steerability and stability would be reduced.
Advanced Bendix EC-60 controllers have an optional dash
switch that initiates a modified ABS control mode (know
as "off-road ABS") that more effectively accommodates
these soft road conditions to shorten stopping distance
while maintaining optimal vehicle steerability and stability.
Note: Off-road mode is not available if the vehicle is
equipped with Hill Start Assist (HSA).
WARNING
: The ABS off-road mode should not
be used on normal, paved road surfaces because
vehicle stability and steerability may be reduced . The
ABS Indicator Lamp will flash slowly to indicate to the
driver that the ABS off-road mode is engaged .
CAUTION : When ABS off-road mode is engaged,
stability functions are disabled at speeds below
approximately 25 mph . The ATC/ESP dash lamp will
illuminate to indicate to the driver that the stability
system is disabled .
The vehicle manufacturer should provide the optional ABS
off-road function only for vehicles that operate on unpaved
surfaces or that are used in off-road applications, and is
responsible for ensuring that vehicles equipped with the
ABS off-road function meet all FMVSS-121 requirements
and have adequate operator indicators and instructions.
The vehicle operator activates the off-road function with a
switch on the dash panel. A flashing ABS Indicator Lamp
indicates to the driver that the ABS off-road function is
engaged. To exit the ABS off-road mode, depress and
release the switch. A new ignition cycle will also cause
the ECU to exit the ABS off-road mode.
All-Wheel Drive (AWD) Vehicles
AWD vehicles with an engaged interaxle differential (steer
axle to rear axle)/AWD transfer case may have negative
effects on ABS performance. Optimum ABS performance
is achieved when the lockable differentials are disengaged,
allowing individual wheel control.
Advanced Bendix EC-60 controllers can be programmed
specifically for this configuration to control the differential
lock/unlock solenoid in the AWD transfer case. When
programmed to do so, the ECU will disengage the locked
interaxle/AWD transfer case during an ABS event and
reengage it once the ABS event has ended.