Active Body Control
Active Body Control (ABC) is the brand name for a chassis technology from Mercedes -Benz.
- 2.2.1 suction throttle valve
- 2.2.2 Control Valves
- 2.2.3 Check valves
- 3.1 Starting
- 3.2 cornering
- 3.3 acceleration / braking
- 3.4 straight-ahead
- 3.5 Vertical vibrations
It describes a system based on a steel suspension electro - hydraulic active suspension system which allows not only the spring and damping function to balance the pitching and rolling movements of the vehicle. Due to the leveling of the vehicle by the hydraulic system ABC vehicles do not need conventional stabilizers, which is unique in the automotive industry. In order to fulfill the functions, a vertically adjustable unilaterally acting hydraulic cylinder ( plunger ) is provided in each shock absorber. It continuously adjusts the respective spring preload. Higher-frequency vibrations are damped by conventional vibration dampers ( shock absorbers ). The system pressure is provided by a belt-driven radial piston pump.
1994, there was however the first time with the Citroën Xantia Activa with " Active chassis stabilization " (AFS ) a vehicle that minimizes body roll of the body by means of an active hydropneumatic suspension. However, only controlled directly and actively the spring of each wheel at the Active Body Control suspension, which is why rolling motions are completely suppressed. ABC is thus the world's first suspension, are actively controlled in the suspension and body damping. To date, there is no other manufacturer has managed to develop an equivalent suspension.
Development
In the S-Class 220 series debuted from 1998 that technical system, as the first car from German production, with an active control of the suspension and damping ( S 600 and S 65 AMG standard, residual surcharge) was available, which then was also installed in the related CL coupes C 215 from 1999.
In 2007, the ABC suspension was extended by the pre -scan system in the Mercedes -Benz F 700. Through sensory sampling of the forward roadway by laser in the two headlights, the ABC control act with foresight and thus significantly improve the ride comfort.
In the S-Class 221 series, the ABC suspension was added a crosswind stabilization. Crosswind effects on the Karossiere be almost completely compensated. Serve as sensors, the yaw rate and lateral acceleration sensors of the Electronic Stability Programme (ESP, English: Electronic Stability Control).
Purpose and function of the sensors and actuators
In order to fulfill its tasks, the system obtains information of sensors and controls a series of actuators.
Sensors
Sensors convert information ( physical quantities ) such as temperature or the same into electrical signals and send them on.
Pressure sensor
The pressure sensor signals the control unit to the respective hydraulic pressure. This is controlled by the intake throttle valve to approximately 180-210 bar.
Oil temperature sensor
It measures the hydraulic oil temperature in the return.
Displacement sensors in the hydraulic cylinder ( plunger )
It conveys the respective actual position of the actuator cylinder in the strut to the control unit. These sensors have been replaced since the introduction of the W221 (current S-Class ) by pressure sensors on each plunger ( shock pressure).
Level sensors
They capture the current level of the vehicle body via the respective control arm position.
Structure and acceleration sensors
They are used to measure the vertical acceleration of the vehicle construction. They consist of electronic vibration modules that send their signals to the control unit. You will be able to detect required to stroke movements of the body.
Transverse and longitudinal acceleration sensors
To determine the transverse and longitudinal dynamics of the vehicle and to compensate for roll and pitch movements required.
Signal recording and actuation module (SAM )
It activates the control unit via remote, the door switch or the trunk light. The control device checks the vehicle level to it, where appropriate, to lower to the preselected level.
Actuators
Suction throttle valve
The suction throttle valve regulates the oil pump sucked in by the amount of oil, so an oil pressure of 180 bar can be set up and kept up to 210 bar in the ABC system. When de-energized, the valve is closed to keep the pressure in the system.
Control valves
By controlling the control valves, the actuator cylinder to be moved. This lowers or lifts the structure at the corresponding wheel This can be briefly increases the contact pressure of the wheels, that is cornering grip.
Check valves
They are closed to avoid with the engine, the vehicle is stopped and an error occurs to pressure loss. For a pulling apart of the actuating cylinder is also prevented, for example, when changing a wheel or when working on a hoist.
Control processes
Start
On opening the vehicle door, the ABC control unit is activated via the signal and control module. Via the level sensors, the actual level is compared with the target level. Where the actual not the target level, the appropriate control valves are actuated and brought the vehicle to the target level.
Cornering
The lateral acceleration sensor detects the centrifugal forces when cornering and transmits it to the control unit. From the front right and front left wheel speeds that are routed via the CAN bus to the control unit recognizes this, whether it is a left or right turn. In a curve, the control device controls the control valve in such a way that the plungers extend on the outside of the curve, and thus the springs are biased. At the same time, the plungers are retracted on the inside of the curve and thus relaxes the springs. A roll of the body can be almost completely eliminated. Via the level sensors, the actual level is compared with the target level.
Acceleration / braking
The longitudinal acceleration sensor detects acceleration forces in the vehicle longitudinal direction when accelerating / braking. The signal is sent to the control unit, which then activates the control valves so that pitching motions of the vehicle body can be prevented.
Straight ahead
When driving straight ahead, the control unit via the CAN bus receives the information of the vehicle speed. Automatically, the vehicle height is lowered by actuation of the control valves by the control device depending on the selective map. By driver's request ( operations of the level switch ), the vehicle can be increased by 25 mm or 50 mm.
Vertical oscillations
Swing the vehicle due to road bumps in the direction of the vertical axis, these movements are transmitted from the structure acceleration sensors to the control unit. The level sensors report the attack also to the controller, this controls the control valves then within the selected map ( eg sport, comfort) so that the vibrations of the structure to be damped and balanced.