Integrated Chassis Management
Integrated Chassis Management
Integrated chassis management
There were two main objectives in the development of Integrated Chassis Management (ICM):
- To increase the performance of the individual driving stability control
- To improve the interplay of the individual driving stability control systems
In every driving situation, the most suitable actuator can now be selected and activated to influence the driving dynamics as desired. Simultaneous deployment of several actuators can of course also make sense. An example of this could be brake intervention on individual wheels or a steering angle overridden by the Integral Active Steering. Another task of the ICM control unit is to provide the systems in the entire vehicle with the dynamic handling characteristics in the form of signals. This is why the DSC sensor, which used to be installed separately, is integrated in the ICM control unit. This enables all systems to access the same information provided by the ICM control unit. The consequence of this is that the causes of faults are reduced and the reliability of the systems is increased, especially in the case of networked systems.
A particular experience for the customer is the coherent driving characteristics due the new Dynamic Driving Control. The driving dynamic control switch is used to operate Dynamic Driving Control. There are 4 programs that can be selected for Dynamic Driving Control:
1. COMFORT
2. NORMAL
3. SPORT
4. SPORT+
Brief component description
The following components are described:
- ICM control unit
- Ride height sensor
- Centre console operating facility
- Servotronic valve
- ECO valve
ICM control unit
New: Sensors that used to be installed separately in the DSC sensor are now fitted in the ICM control unit. The ICM control unit uses these sensors to calculate variables that are important for the dynamic handling characteristics of the vehicle at that time:
- Longitudinal acceleration and vehicle inclination in longitudinal direction
- Lateral acceleration and vehicle inclination in transverse direction
- Yaw rate
Initially, the sensor signals are related to the sensor housing. However, the driving stability control needs these variables related to the coordinate system of the vehicle. The ICM control unit performs the necessary conversion. The correction values necessary for this are determined by an adjustment during commissioning of the ICM control unit.
An adjustment of the integrated sensors is necessary after replacement of the ICM control unit. The adjustment must take place while the vehicle is on a subsurface that is horizontal in longitudinal direction and transverse direction. Terminal 15 must be switched on.
The ICM control unit is available as a basic version and a high version. The high version differs in that it has:
- A larger micro-controller (required for calculation of the control operation of Integral Active Steering and Active Cruise Control)
- A redundant sensor system for lateral acceleration and yaw rate (safety requirement for Integral Active Steering).
The ICM control unit is located in the vicinity of the vehicle centre of gravity.
The control unit is mounted on the transmission tunnel using 4 bolts and spacer sleeves made of aluminium. This mounting must connect the control unit with the vehicle body without play. Otherwise, the control unit housing would vibrate, which would seriously diminish the operating principle of the integrated sensor system. A second task of this mounting is to dissipate heat from the control unit to the body.
Ride height sensor
Depending on the optional equipment, a maximum of 4 ride height sensors are connected to the ICM control unit (2 front axle, 2 rear axle). On vehicles with electronic ride height control (EHC), the rear ride height sensors are 2- channel: 1 connection to the ICM control unit and 1 connection to the EHC control unit.
2-channel ride height sensors discontinued from 09/2010 (bus message from ICM).
The ride height sensor is a non-contact sensor. 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 for each sensor is 70° (depending on installation posit ion, see characteristic curve). The signals are output as analogue electrical voltages.
Centre console operating facility
The driving dynamic control switch is used to operate Dynamic Driving Control. The new Dynamic Driving Control has the following innovations: 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). The driving dynamic control switch and the DTC button are electrically connected to the ICM.
The following systems are influenced by Dynamic Driving Control:
- Accelerator pedal module
- Automatic transmission
- Steering
- Vertical dynamics management (VDM) via shock absorbers as well as active roll stabilization
- Dynamic stability control (DSC)
Servotronic valve
NOTE: not in conjunction with EPS electromechanical power steering.
The Servotronic controls the degree of assistance provided by the hydraulic steering depending on the vehicle's speed. The flow of hydraulic fluid is restricted to a greater or lesser extent depending on how the Servotronic valve is actuated. Restriction of the flow depends on the current actuating the Servotronic valve.
The Servotronic valve is actuated by the ICM control unit. The signals and messages required for the Servotronic are as follows:
- Driving speed from the DSC control unit via the bus
- Status of the engine from the DME control unit
- Terminal status from the CAS control unit via bus
The Servotronic valve is only activated when terminal 15 is ON and the engine is running. When the speed signal is present, the setting of the nominal current is taken from the characteristic curve.
ECO valve
NOTE: not in conjunction with EPS electromechanical power steering.
The power steering pump is a vane-type compressor. The ECO valve (ECO = Electronically Controlled Orifice) is located at the power steering pump. The ECO valve regulates the volumetric flow of the hydraulic fluid, thus regulating the pump's hydraulic power.
A tandem pump is installed on vehicles with Dynamic Drive. The radial pistons supply the active roll stabilization (ARS). The vane-type compressor supplies the steering.
The ECO valve in the power steering pump regulates the volumetric flow depending on the requirement and lowers the ram pressure in the hydraulic system. In this way, the ECO valve affects the power consumption of the power steering pump. Fuel consumption and carbon dioxide emissions (CO2) from the vehicle's engine are reduced accordingly.
System functions
The following system functions are described:
- The Integrated Chassis Management system network
- Dynamic Driving Control
- Other functions
The Integrated Chassis Management system network
The following illustration shows the system network for the driving dynamics control
Dynamic Driving Control
The new Dynamic Driving Control has the following two new features:
- All of the drive and driving dynamics control systems installed in the vehicle are switched at once.
- There is a choice of 4 stages. The state of the dynamic stability control is also taken into account, which means that 2 more stages are possible.
Dynamic Driving Control is operates using a new driving dynamic control switch and the DTC button arranged directly in front of it. Dynamic Driving Control thus bundles the switching of many drive and driving dynamics functions. The entire vehicle behaves in exactly the way the driver expects due to the stage selected. This bundling means that the characteristics of the vehicle are considerably more distinctive and that there is less emphasis on compromises. On the other hand, a large number of individual combinations, some of which make no sense, are avoided (example: sporty steering and simultaneous comfort-oriented damping).
New display when DTC button is selected. "TRACTION" can be seen in the revolution counter of the instrument panel. The symbol of the indicator light has changed as a result of legal regulations: Skidding vehicle with the labelling "OFF".
Other functions
Integrated Chassis Management (ICM) assumes the following functions:
- Central signal plausibility check for longitudinal and lateral acceleration, and yaw rate
- Central signal provision for driving speed, road longitudinal and lateral inclination
- Activation and control function for control units of the active steering (AL) as well as rear axle slip angle control (HSR)
- Calculation for activation of the actuators for active steering, rear axle slip angle control and Dynamic Stability Control (DSC)
- Driver assistance function cruise control system: cruise control system with braking function as well as active cruise control with stop-and-go driving
- Calculation for activation of the lane departure warning (TLC) as well as lane change warning (SWW)
- Central co-ordination of the display of Check Control messages for the suspension control system
- Central co-ordination of the torque request for suspension control systems
NOTE: Other functional descriptions are important.
Observe the functional descriptions in the diagnosis system with regard to the driver aid functions.
Notes for Service department
General notes
After installation of the new ICM control unit, the diagnosis system must be used to start-up the unit. Here, the following steps are carried out (depending on vehicle equipment):
- Adjustment of the sensor system integrated in the ICM
- Adjustment of the ride height sensors
- Initialization of the Integral Active Steering.
Diagnosis instructions
NOTE: Use the service functions.
The diagnosis system contains the following service functions for the Integrated Chassis Management:
- Adjustment of ICM sensor system
- ACC sensor start-up (if present)
- Adjust long-range sensor (if present)
- Adjust short-range sensor (if present)
- Ride height adjustment
- Start-up, alignment of active steering
- Steering angle sensor adjustment
- Initialization of motor position sensor HSR (= rear axle slip angle control)
- Commissioning SWW sensor system (= lane change warning)
No liability can be accepted for printing or other faults. Subject to changes of a technical nature