Self Study Program 960393 – Active suspension
VAG SSP 960393. The Audi active suspension is an electromechanically operated suspension system. It can increase or reduce the load on each wheel individually to adjust to the road as needed. This means the system can actively control the position of the vehicle body in every driving situation.
For each wheel there is one electric motor supplied by a 48-volt electrical system. The Driver Assistance Systems Control Module sends control signals to the active suspension every five milliseconds. A single Suspension Stabilization Control Module per axle processes the signals for the electric motors. A belt drive and compact gearing arrangement step up the torque of the electric motor and transfer it to a steel rotary tube. The tube houses and is rigidly joined to a titanium torsion bar. This bar is more than 15.7 in (40 cm) long, approximately 0.9 in (22 mm) thick and, despite its high strength, can be twisted more than 20 degrees. The force is transferred from the end of the torsion bar to the suspension via a lever and a coupling rod. This force is exerted at the front axle on the pneumatic strut of the adaptive air suspension and at the rear axle, on the transverse link.
The range of ride characteristics takes on a whole new dimension thanks to the flexibility of the active suspension. If the driver chooses “Dynamic” mode in the Audi drive select system, the car becomes a sports car. It turns firmly into corners and body roll angles are reduced by half compared with a conventional suspension. The body hardly dives at all during braking. In “Comfort” mode, however, it glides smoothly over any and all road surface irregularities. The active suspension settles the superstructure by continuously adding energy to or removing energy from the body depending on the respective driving situation.
The active suspension also enhances passive safety. The system uses the sensors networked in the Driver Assistance Systems Control Module (zFAS) to detect risks of a collision around the vehicle. In the event of an imminent side impact of more than 15.5 mph (25 km/h), the suspension actuators raise the body on the exposed side by up to 3.1 in (80 mm) within half a second. As a result, the collision is directed to the even stronger areas of the vehicle, such as side sills and floor structure. The load on occupants is reduced by up to 50 percent compared with a side impact when the body is not raised.
- Running gear concepts compared
- Basic principle
- Design of the system
- System components
- Actuators for running gear stabilization
- Harmonic drive gear
- Electric motor
- Suspension stabilization control modules
- Drivetrain Control Module J775
- System functions
- Additional preview function
- Additional crash lifting function
- Additional elevated entry function
- Additional corner tilting function
- Additional helicopter function
- Operation and servicing
- Operation and driver information
- System behavior in the event of a fault
- Service operations
- Knowledge assessment