CONFIDENTIAL
Bendix Commercial Vehicle Systems LLC
Elyria, OH 44036
PRODUCT SPECIFICATION - BW-283-PR
SPEC. BW-283-PR
73 SHEETS
SHEET NO. 9
2 General Product Description
2.1 Trailer Antilock Braking System (TABS)
The Bendix
®
TABS is an electronic system that prevents wheel lock-up during braking to
maintain optimal vehicle steer-ability and stability, as well as minimizing stopping
distance.
The TABS intervenes during braking whenever the available friction between the road
and the tire of a monitored wheel is less than the braking force applied to the wheel
causing the wheel to decelerate (impending wheel lock) quickly.
The system consists of the following components:
• Electronic Control Unit (ECU)
monitors the speed sensor signals and determines
when ABS intervention is required. It then actuates the appropriate pressure
modulator valves to optimize the brake pressure. The ECU continually monitors the
system to detect and warn the driver of any malfunctions. Diagnostic Troubleshooting
Codes (DTC) are stored in the ECU and can be recalled to diagnose a failure.
• Wheel Speed Sensors (WSS)
located at the wheels to sense the instantaneous
movement of individual wheels and to send an electrical signal directly proportional to
the rotational velocity of the sensed wheel to the electronic control unit.
• Modulator Relay Valves (MRV)
located near the brake chambers and are controlled
electrically by the ECU to decrease, hold or allow the full applied brake pressure into
the brake chamber to control the braking torque at the wheels.
• Trailer ABS Warning Lamp
is controlled by the ECU as required to indicate ABS
status. The trailer ABS warning lamp will illuminate when ignition power is applied to
the ECU, and extinguish after a lamp check is performed if there are no ABS faults
present.
2.2 ABS Control Modes
Several ABS control modes can be utilized for monitoring and controlling the individual
wheels of the trailer. The possible modes are:
• Axle Control:
TABS axle control will utilize a single ABS modulator-valve to control
wheels from both sides of a given axle or axles. In the case of an unbalanced
braking surface, axle control will control the high coefficient wheel just under the lock
limit. Temporary periods of wheel lock are permitted on the low coefficient wheel.
Axle control should not be used on fifth wheel dollies or steerable axles. When
braking on even surfaces, an axle-control system will perform similar to a side
control, two-modulator system. Axle control is available in 2S/1M, 2S/2M and 4S/2M
installations.
• Dolly-Axle Control (Select Low):
TABS dolly-axle control will utilize a single ABS
modulator-valve to control wheels from both sides of a given axle or axles. In the
case of an unbalanced braking surface, dolly-axle control will control the low
coefficient wheel just under the lock limit. Optimal vehicle stability is achieved by not
allowing the high coefficient wheel to sustain wheel lock. When braking on even
surfaces, a dolly axle control system will perform similar to side control or axle control
system. Dolly axle control is only available in 2S/1M installations.
DOCUMENTO CONTROLADO DE FORMATO ELECTRÓNICO: Antes de utilizarlo se requiere verificar el nivel de revision o la suficiencia.
CONTROLLED ELECTRONIC MEDIA DOCUMENT: Verification of revision level or adequacy is required prior to use.
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