Electronic Damper Control

Electronic Damper Control

Electronic Damper Control
On the E89, Electronic Damper Control is used for vertical dynamics management. Electronic Damper Control is integrated as a function in the EDC control unit.
On the E89, the sales code is "Adaptive M running gear" (option 2VF). The Adaptive M running gear includes a chassis lowered by 10 mm.
Electronic Damper Control (EDC) provides the following advantages:
- greater on-road comfort
- greater vehicle agility
- improved self-steering characteristics and load-change characteristics







Electronic Damper Control senses the road surface condition, vehicle load and driving dynamics. The EDC control unit adapts the damping force of the shock absorbers to these input variables. The damping force is varied continuously. The driver also has the possibility to choose a shock absorber setting using the driving dynamics switch. After an engine start, the EDC is always in the "NORMAL" program.

Brief description of components
The following components are described for vertical dynamics management:

EDC: Electronic Damper Control
The EDC control unit is installed in the engine compartment behind the left-hand wheel arch.







Vertical dynamics management increases on-road comfort. Greater on-road comfort is achieved when the vehicle body moves vertically as little as possible: whether due to agitation of the vehicle by the road surface (unevenness, joints) or cornering or driving off or braking

Shock absorber with EDC valve
Twin-tube gas-filled shock absorbers are fitted on the front and rear axle. The shock absorbers used for EDC are map-controlled. They no longer have fixed damping levels. A proportional valve that can be regulated is fitted to each shock absorber. As the suspension travels up and down, gas[?] flows back and forth through that valve. The control valve specifies the pressure drop between the bottom and top side of the piston. That pressure drop alters the force acting on the piston rod. The current to the control valves is limited to 2 amperes. In addition to the control valve there is also a base valve integrated in the shock absorber. The base valve implements a minimum compression damping.







At a standstill, the shock absorbers are de-energized. As of approx. 5 km/h, the shock absorbers are supplied with current.

Vertical-acceleration sensors
There are a total of 3 vertical-acceleration sensors:
- Vertical-acceleration sensor, front left
- Vertical-acceleration sensor, front right
- Vertical acceleration sensor, rear right

The vertical-acceleration sensor measures the up and down motion (vertical motion) of the body with a spring-mass vibration system. The three vertical-acceleration sensors that are deployed have a measuring range of ±2.5 g.







The EDC control unit supplies the vertical-acceleration sensors with 5 Volts. The sensor earth in each case is also connected to the EDC control unit.

Driving dynamics switch
The driving dynamics switch for Driving Dynamics Control is in the centre console beside the gear selector switch (GWS). The driving dynamics switch can be used to select 3 programs:
- NORMAL
- SPORT
- SPORT+

With SPORT+, the DTC function is switched on.
The selected program is displayed in the instrument cluster.
The driving dynamics switch affects the following systems:
- Electronic Damper Control
- Response characteristics of the engine (characteristic curve of accelerator pedal module)
- Shifting times for automatic gearbox
- Steering power assistance
- Driving stabilization by means of DSC







The driving dynamics switch is connected to the junction box electronics (JBE). The footwell module supplies the driving dynamics switch additionally with terminal 58g (locating lights).
The following other control units deliver signals for the Electronic Damper Control (EDC):

DSC: Dynamic stability control
The DSC control unit delivers the driving speed as well as brake pressure on the PT-CAN to the EDC control unit (bus signal). In addition, a processed wheel-speed signal (front left and right) is sent to the EDC control unit. The signal form used is digital wheel impulses.

SZL: Steering column switch cluster
The SZL delivers the steering-angle-sensor signal on the F-CAN to the DSC (advance detection of cornering). The signal is transferred from the DSC across the PT-CAN.

DME: Digital Motor Electronics
The engine management system delivers the signal Engine running . The signal is transferred across the PT-CAN.

FRM: Footwell module
The footwell module supplies the driving dynamics switch additionally with terminal 58g (locating lights).

JBE: Junction Box electronics
The JBE delivers the terminal status. The JBE is also the gateway between the PT CAN and K CAN.
The driving dynamics switch is also connected to the junction box electronics (JBE).







System function
The following system functions worthy of the customer are described for the Electronic Damper Control (EDC):
- Damping of the wheel accelerations as well as body movements
- Fail safe

Damping of the wheel movements as well as body movements
To dampen the wheel movements and body movements, the motion of the vehicle is monitored. Here, the following axes are included:
- Vehicle vertical axis
- Vehicle lateral axis
- Vehicle longitudinal axis

The following signals, e.g., are used for monitoring:
- Vertical acceleration
- Steering angle and driving speed
- Longitudinal acceleration and deceleration

The signals are used to calculate the current driving situation.
For the vehicle vertical axis, control of the damping action is aligned with regard to comfort and safety. The Electronic Damper Control dampens the body movements to enhance comfort. The Electronic Damper Control dampens the wheel accelerations to enhance safety. At the same time, it must be ensured that the wheels have optimal contact with the road surface. Depending on the situation, optimized vertical force must be transferred.
The Electronic Damper Control also takes account of steering angles (e.g. transition from straight-ahead driving into a curve). If a rapid enlargement of the steering angle is detected, the EDC control unit concludes that cornering is about to begin. This means that the shock absorbers can be activated accordingly in advance.
The Electronic Damper Control also detects braking and driving off. To achieve this, the DSC provides the brake pressure and longitudinal acceleration signals. Excessive brake pressure normally leads to a pitching motion of the vehicle. The EDC counteracts this pitching motion with a harder setting of the front shock absorbers. This also counteracts the pitching motion of the vehicle on driving off.

Fail safe
When de-energized, the EDC valves are in the position "hard". The EDC control unit activates the EDC valves and adjusts them to "soft". The EDC control unit has 2 output stages (switched in series). Here, the 4 EDC valves are activated at the shock absorber axle by axle.
In the event of a fault, the EDC control unit supplies the EDC valves in the first stage with minimum current. This corresponds to medium damping. Only in the 2nd stage are the EDC valves no longer supplied with current. This causes the valve to move to a position that corresponds to harder damping. A Check Control message is output to the driver. A fault is entered in the fault memory.







Notes for Service department

Diagnosis instructions
The following service functions are available for the EDC:
- Commissioning after control unit replacement

Notes on coding / programming
After replacement, the EDC control unit must be recoded.
No liability can be accepted for printing or other errors. Subject to changes of a technical nature