BMW 7 Series: Introduction

Integrated Chassis Management (ICM)

History

A central, higher-level driving dynamics control system was first introduced in BMW vehicles several years ago.

The introduction of the longitudinal dynamics management system in the BMW 3 Series (E9x) was the first step in this direction. The longitudinal dynamics control functions, Dynamic Cruise Control and Active Cruise Control, were integrated into one control unit, the LDM control unit. These integrated functions considerably enhanced the harmony and coordination of drive and brake actuation.

The Vertical Dynamics Management made its debut in the BMW X5 (E70) with the VDM control unit: the integrated Vertical Dynamics Control (VDC) function controls the adjustable dampers. In contrast to the earlier system, not only ride-level heights and vertical acceleration are used as the input signals. Instead, the higherlevel control strategy of the Vertical Dynamics Control takes all signals relevant to driving dynamics into account, including, for example, road speed, and longitudinal and lateral acceleration.

The VDM control unit also coordinates the Vertical Dynamic Control and Active Roll Stabilization (ARS) functions. Overall, this meant that wheel contact with the road surface was improved and the vertical movement of the body reduced for a wider variety of road situations.

In addition to the VDM control unit, the BMW X6 (E71) was also equipped with an ICM control unit that for the first time incorporates both the longitudinal and lateral dynamics control functions. The longitudinal and lateral motion of the vehicle is evaluated centrally in the ICM control unit.

Following on from this development, the dynamic driving systems Active Steering and Dynamic Performance Control are now used and their interaction is of course also coordinated by the ICM control unit.

Significant at this stage is the definition of the ICM as the main control unit for the control functions. The actuators on the other hand are activated by control units specially intended for this purpose.

Fig. 10: Evolution Stages Of Integrated Chassis Management

INDEX REFERENCE CHART

The red triangles denote interaction between the control units and functions. This is not always purely be an exchange of sensor signals. Control signals and reference values may be also used (for example) to influence the driving dynamics control in the ICM control unit or the Active Roll Stabilization in the VDM control unit.

New Control Units

Two newly developed control units for dynamic driving systems will also be used in the F01/F02:

• Integrated Chassis Management (ICM) and
• Vertical Dynamics Management (VDM).

Although their names are already familiar from the E70/E71, they differ considerably in their functional range and design.

A multitude of driving dynamics functions is concentrated in these control units.

In addition to central signal provision, the essential functions of the ICM control unit are concerned with longitudinal and lateral dynamics. These include the control function for the new Integral Active Steering, for example.

The vertical dynamics functions on the other hand are incorporated in the VDM control unit: Vertical Dynamics Control in the 2nd generation and Active Roll Stabilization (also: Dynamic Drive).

Although both control units are standard equipment, two expansion stages are available in each case, depending on the options fitted to the vehicle.

ICM control unit expansion stages

The basic version of the ICM control unit is fitted as standard in the F01/F02. In this case, the vehicle is provided with the Servotronic steering system and cruise control driver assistance function with braking function.

The high-performance version of the ICM control unit is used if one or both of the following options are ordered by the customer:

• Integral Active Steering
• Active Cruise Control with Stop&Go function

Expansion stages of VDM control unit

The basic version of the VDM control unit contains the Vertical Dynamics Control function. This is included in the standard equipment of the F01/F02.

The high-performance version of the VDM control unit is fitted if the customer also orders the option Active Roll Stabilization (ARS). The high-performance version also incorporates the output stages required for activation of the hydraulic valves in the ARS.

New Evolution Stage in Driving Dynamics Control

The notion of "Integrated Chassis Management" is significantly developed further in the F01/F02. The two main objectives were to improve the performance and interaction of the individual dynamic driving systems. In order to achieve the desired dynamic effect in each road situation, the most suitable actuator can now be selected and activated. It may of course be useful to operate several actuators in tandem. Examples of this are activating the brakes for individual wheels or superimposing a steering angle using Integral Active Steering.

A further task of the ICM control unit is to make the driving dynamics condition available throughout the entire vehicle through in the form of signals. This is why the DSC sensor in the F01/F02, which was previously fitted separately, has now been integrated into the ICM control unit.

This means that all systems have access to the same information provided by the ICM control unit. As a consequence, the potential for errors, particularly in networked systems, is reduced and the system reliability of systems is increased. Further, this simplifies the diagnosis of the interconnected system as the fault code memory entries for the driving dynamics signals are now stored centrally in the ICM control unit and are no longer distributed between many control units.

Fig. 11: Identifying Driving Dynamics Signals By ICM Control Unit

INDEX REFERENCE CHART

The result for the customer is perfect harmony in terms of vehicle handling - irrespective of the equipment specification and road situation. This uses the possibilities for maximizing convenience, agility and stability to the full.

The customer's experience of this harmony in terms of vehicle handling is especially enhanced by the new Driving Dynamics Control function. This offers several particularly distinctive vehicle characteristics that determine how the vehicle handling as a whole is perceived by the driver and passengers. The driver can use the driving dynamics switch to select a characteristic that perfectly matches the specific driving requirement or section of road.

Standard Equipment and Options

The following table shows the standard equipment and options available for dynamic driving systems. A specific model (750i) has been selected in order to compare the functions and equipment levels of the E65 and F01.

DYNAMIC DRIVING SYSTEM FUNCTIONAL CHART

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