Vertical Dynamics Management
Vertical Dynamics Management
Vertical dynamics management (VDM)
Vertical Dynamics Management is standard equipment. The following functions can be installed in the vertical dynamics management control unit (VDM) as optional equipment:
- Vertical dynamics management
- active roll stabilization (marketing designation: Dynamic Drive)
This document describes the vertical dynamics management.
The VDM control unit is activated via terminal 15N by the CAS control unit. At the same time, the VDM control unit is supplied with terminal 30.
EDC means: Electronic Damper Control
Vertical dynamics management offers the following advantages:
- greater on-road comfort
- greater vehicle agility
- Improved self-steering response and response to changing loads
Vertical dynamics management (VDM) is an enhancement from the X5. VDM is composed of a central control unit and 4 intelligent damper satellites that are firmly connected to the shock absorbers. These 5 control units are networked via FlexRay. A new feature is the incorporation of 1 EDC valve for the rebound and compression stage respectively. This means that the control operation no longer has to be clocked so quickly.
Brief component description
The following components are described for vertical dynamics management:
VDM: Vertical Dynamics Management
The VDM control unit is located in the passenger footwell at the A-pillar.
The VDM enhances on-road comfort. Greater on-road comfort is achieved when the vehicle body moves vertically as little as possible: whether this is due to agitation of the vehicle by the roadway surface (unevenness, joints) or on curves. The VDM controls the damper satellites in the activation of the shock absorbers (impact force for individual wheel). To this end, the VDM control unit is connected to the damper satellites via the very fast FlexRay data bus.
With a data transfer rate of 10 MBit/s, FlexRay is significantly faster than the data buses deployed nowadays in motor vehicles (in the area of body and drive or chassis). FlexRay supports not only the greater bandwidth but also data interchange with real-time capability. FlexRay can be configured as error-tolerant.
Damper satellites
There are 4 damper satellites:
- Damper satellite, front left (EDCSVL)
- Damper satellite, front right (EDCSVR)
- Damper satellite, rear left (EDCSHL)
- Damper satellite, rear right (EDCSHR)
The damper satellites electronically control the damping forces. The damper satellites and the EDC valves are inseparably connected to the shock absorbers. The damper satellites each have one EDC valve for the rebound stage and one for the discharge stage. Each damper satellite contains its own vertical-acceleration sensor.
The damper satellites have the following tasks (among others):
- activating the EDC valves on the shock absorbers (characteristic map for damping)
- measuring the internal current (actual value) of the EDC valves and regulating to the setpoint value.
- measuring the vertical acceleration of a wheel
, ride height sensors
There are the following 4 height-level sensors:
- Height-level sensor, front left (single)
- Height-level sensor, front right (single)
- Height-level sensor, rear left (single, double only with single-axle level control)
- Height-level sensor, rear right (double, double only with single-axle level control)
The 4 height-level sensors are-series standard. Depending on the options fitted, there are 1 channel and 2- channel sensors on the rear axle. 2 channel sensors deliver the signal to the:
- Integrated chassis management (ICM)
- Control unit for the electronic ride height control (EHC = ride height control)
The height-level sensors are electrically connected to the Integrated Chassis Management (ICM). The implements the signal on the FlexRay.
The height-level sensors deliver dynamic information on the height of the vehicle body. This is used by the Vertical Dynamics Management to calculate the body movements and wheel accelerations. In addition, the sensors deliver the information to the automatic headlight beam throw adjustment.
The ride height sensor proportionally converts distances into an analogue voltage signal using an angle of rotation.
The sensor can be rotated by 360°. The measuring range is 70° (depending on the installation position) . The signals are output as analogue electrical voltages.
Drive dynamic control switch
The driving dynamic control switch and the gear selector switch are used to operate Dynamic Driving Control. The new Dynamic Driving Control has the following innovations:
1. All of the drive and driving stability control systems installed in the vehicle are activated. The central control unit for this is the Integrated Chassis Management (ICM).
2. A choice of 4 programs is available:
- COMFORT
- NORMAL
- SPORT
- SPORT+
Driving Dynamics Control influences vertical dynamics management as well as other systems.
The following other control units deliver signals for the vertical dynamics management:
ICM: Integrated chassis management
Integrated Chassis Management (ICM) assumes the following functions in vertical dynamics management:
- Central signal plausibility check for longitudinal and lateral acceleration, and yaw rate
- Central signal provision for driving speed, road longitudinal and lateral inclination
- Central co-ordination of the display of Check Control messages for the suspension control system
DSC: Dynamic Stability Control
The DSC control unit delivers the brake pressure on the FlexRay to the VDM.
SZL: Steering column switch cluster
The SZL delivers the steering-angle-sensor signal on the FlexRay to the VDM (advance detection of cornering).
DME or DDE: Digital Motor Electronics or Digital Diesel Electronics
The engine control system delivers the signal "Engine running". The signal is transferred across the FlexRay.
System function
The following system functions are described for vertical dynamics management:
- Functional networking
- Damping of the wheel accelerations as well as body movements
- Fail safe
Functional networking
A complex composite system with distributed functions in other control units is necessary for the implementation of vertical dynamics management. The following graphic shows the system network.
NOTICE: Measure introduced.
In the next generation of Integrated Chassis Management (ICM), only the centre console operating facility is connected to the ICM.Observe wiring diagrams in diagnosis system.
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:
- Height and wheel acceleration
- Steering angle and driving speed
- Lateral and longitudinal acceleration
The signals are used to calculate the current driving situation.
Control of the damping action for the vehicle vertical axis is subdivided into comfort and safety. Vertical Dynamics Management damps body movements to enhance ride comfort. Vertical Dynamics Management damps wheel acceleration to enhance safety. At the same time, it must be ensured that the wheels do not lose contact with the roadway surface. Depending on the situation, optimized vertical force must be transferred.
The vertical dynamics management 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 VDM control unit concludes that cornering is about to begin. This means that the shock absorbers can be activated accordingly in advance. In doing so, the vertical dynamics management supports active roll stabilization (ARS). This means that the VDM contributes to reducing the rolling motion of the vehicle.
The vertical dynamics management also detects braking and acceleration. 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 VDM counteracts this pitching motion with a harder setting of the front shock absorbers. This also counteracts the pitching motion of the vehicle on accelerating.
Depending on the selected damping characteristics (driving dynamics switch), the level of the damping force is adapted by the VDM control unit. Independently of this, there is maximum driving safety in critical driving situations despite the selected comfort program.
Fail safe
Depending on the type of fault that has occurred, the fail safe takes effect in 3 stages:
- Stage 1: substitute values
If, for example, the steering-angle-sensor signal is unavailable, other variables are used as substitute values for the detection of cornering. The driver does not receive a Check Control message: no fault entry.
- Stage 2: constant voltage supply
The VDM control unit specifies a constant damping force that is the same for all 4 wheels (medium hard damping). The damper satellites set a constant voltage supply for the EDC valves. A defective height-level sensor, for example, can be the cause. A Check Control message is output to the driver. A fault is entered in the fault memory.
- Stage 3: no voltage supply
If a fault has occurred in activation of an EDC valve:
The VDM control unit indicates to the damper satellites that the EDC valves may no longer be supplied with current. This causes the valve to move to a position that corresponds more to medium to harder damping. A Check Control message is output to the driver. A fault is entered in the fault memory.
Notes for Service department
General notes
IMPORTANT: Specify the installation location when replacing the shock absorber.
The shock absorbers, the damper satellites and the 2 EDC valves form a single unit. When ordering a new component, the type of vehicle and installation position (e.g. front left) must be specified. There are dependencies e.g. with regard to: engine version, suspension.
Diagnosis instructions
NOTICE: There are several fault memories in the Vertical Dynamics Management.
The VDM control unit only its own faults in its own fault memory. Faults in the damper satellites are stored in their own fault memory. This is why not only the fault memory of the VDM control unit, but also that of the damper satellites, must be read out in the event of a fault.
IMPORTANT: Adjust the ride height sensors.
After replacement of the ICM control unit as well as of a height-level sensor, the adjustment values of the height level sensors must be relearned. The service function "ride height adjustment" on the diagnosis system must be used.
Information on encoding and programming
After replacement, the VDM control unit must be recoded.
Switch-on conditions
The vertical dynamics management is activated under the following conditions:
- Ignition ON (terminal 15 and wake-up line)
- Speed greater than 0.1 km/h
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.