W32.34>1016>09
Shown on model 963.403
1 Left front axle shock absorber 2 Right front axle shock absorber 3 Left rear axle shock absorber 4 Right rear axle shock absorber A26 Level control (CLCS) control unit B20 Left drive axle pressure sensor
Y13 Right 1st front axle proportional valve
Y16 Left 1st rear axle proportional valve Y17 Right 1st rear axle proportional valve B21 Right drive axle pressure sensor
B24 Left drive axle position sensor B25 Right drive axle position sensor B27 Front axle position sensor
i This description is based on a 2>axle vehicle of model 963.403 (wheel configuration 4x2) with code (A1A) Front axle air suspension. All functions and control situations/control states are identical on the other vehicle models. Only the number of controlled shock absorbers differs depending on vehicle model and equipment.
General information
Roll control (WR) is an electronic shock absorber control system that is used to precisely adapt the damping characteristics to the respective load, current driving situation and road surface conditions.
The roll control (WR) function is integrated in the level control (CLCS) control unit (A26). This means that the existing sensors of and information from the level control system (CLCS) can also be used for roll control (WR).
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i On vehicles with roll control (WR), the full version of the level control (CLCS) control unit (A26) is always installed.
The control logic of the roll control (WR) function collects the variables occurring during the current driving operation, uses them to calculate the optimum damping requirements and adjusts the shock absorber characteristics on the basis of this information.
The functions of the roll control (WR) are enabled using parameters for each individual axle. Up to four axles can be actuated.
Two shock absorbers, each with an electrically actuated proportional valve, are always fitted at each axle. They are actuated steplessly at each axle. On vehicles with roll control but without code (A1A) Front axle air suspension, shock absorbers with proportional damping valves are also fitted at the steel> sprung front axles.
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Function
The level control (CLCS) control unit (A26) receives signals: f from the left drive axle position sensor (B24) regarding the
left rear spring travel,
f from the right drive axle position sensor (B25) regarding the right rear spring travel,
f from the front axle position sensor (B27) regarding the left and right front spring travel,
f from the left drive axle pressure sensor (B20) regarding the left rear bellows pressure,
f from the right drive axle pressure sensor (B21) regarding the right rear bellows pressure,
f from the tachograph (TCO) (P1) regarding the vehicle speed, f from the Electronic Brake Control (EBS) control unit (A10b,
A10c) regarding vehicle speed, deceleration values, front wheel rotational speed and possible ABS/ASR intervention, f from the Electronic Stability Program (ESP“) control unit
(A25, A25a) regarding the steering wheel angle and possible ESP intervention,
f and from the transmission control unit (TCM) (A5) regarding the clutch status.
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From these signals, the level control (CLCS) control unit (A26) calculates the damping requirements of the shock absorbers within a few milliseconds.
The left 1st front axle proportional valve (Y12), right 1st front axle proportional valve (Y13), left 1st rear axle proportional valve (Y16) and right 1st rear axle proportional valve (Y17) are actuated at the appropriate shock absorbers, taking handling
characteristics, vehicle condition, outside interference and vehicle response into consideration.
i Depending on actuation, the proportional valves steplessly adjust the oil flow rate for the rebound and compression stage in the shock absorbers.
In order to actuate, the proportional valves must first be
energized with their maximum current of 2 A (pushing). There will be no adjustment of the shock absorber behavior if energization occurs without prior pushing.
Control situations/control states
f Load condition
The load condition is detected using the bellows pressures at the rear axle. Damping is increased as the load increases. f Vehicle speed
Damping is increased as the vehicle speed increases. f Level control
If level control occurs while the vehicle is stationary, the shock absorbers are set to the lowest level in order to reduce friction during the raising and lowering procedure. f Change in roll angle
Roll behavior is assessed using the left and right rear jounce and rebound travel. Appropriate adjustment is performed especially when vehicles with a high center of gravity perform lane>changing maneuvers, .
f Pitch angle
The pitch angle is determined by means of the rear position sensors. Sprung mass vibrations, especially when braking and driving off and also on uneven road surfaces, are reduced by increasing damping.
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f Lateral acceleration
Lateral acceleration is determined using the difference in rotational speed and the average speed of the front wheels. If lateral acceleration is detected, damping is increased slightly.
f Change in lateral acceleration
Examples of this criterion are lane changes and sudden evasive maneuvers. The greater the change in acceleration is, the higher the damping requirement will be. This is intended to harden the shock absorbers even more quickly in the case of rapid steering movements than is possible by only changing the roll angle.
f Longitudinal acceleration
If the engine specified torque increases, damping is increased in order to counter a squatting motion of the vehicle.
f Deceleration
When the service brake is actuated, damping is increased in order to counter the expected pitching of the front axle. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
f Deviation from pitching response time
If the vehicle is subjected to the natural pitching frequency (e.g. resulting from surface undulations), increasing damping will counter jerking of the body.
f Road surface conditions
The frequency and travel of axle motion are detected by the position sensors. If a "poor road surface" is detected, damping is reduced in order to improve ride comfort. Here, it is the high>frequency axle vibrations that are taken into consideration in particular.
i Usually, several criteria occur simultaneously when the vehicle is in motion. The highest calculated damping requirement is output as the damping value for the shock absorbers.
f Fail>safe condition
If the proportional valves are not energized (if the vehicle is stationary or there is a system failure) or if the current drops below the minimum current of 700 mA, damping
corresponding to the series ID is applied (fail>safe condition). i If a shock absorber fails, only the shock absorbers of the axle concerned are switched to the fail>safe condition.
Roll control > overall network
Page 84
Level control (CLCS) control unit, component description
Page 358
Proportional valve, component description
Page 480
Position sensor, component description
Page 410
Level control pressure sensor, component description
GF32.34>W>0006>01H Roll control > overall network
W32.34>1024>79
A2 Central gateway (CGW) control unit
A3 Drive control (CPC) control unit A5 Transmission control (TCM)
control unit
A10 Antilock brake system (ABS) control unit, 4>channel A10b Electronic Brake Control (EBS)
control unit (Wabco) A10c Electronic Brake Control (EBS)
control unit (Knorr)
A20 Front axle modulator (Wabco)
A26 Level control (CLCS) control unit CAN 1 Exterior CAN
CAN 3 Frame CAN CAN 4 Drive train CAN CAN 6a Front axle brakes CAN CAN 6b Rear axle brakes CAN CAN 6c Redundant brakes CAN CAN 6d ESP“ brakes CAN P1 Tachograph (TCO) Z3 Frame CAN bus star point Z4 Drive CAN bus star point A20a Front axle modulator (Knorr)
A21 Rear axle modulator (Wabco) A21a Rear axle modulator (Knorr) A25 Electronic Stability Program (ESP“) control unit (Wabco) A25a Electronic Stability Program (ESP“) control unit (Knorr)