Chassis Dynamics -- Overview (F01/F02): Adjustments BMW 7 series F01/F02

Control and Adjustment of Steering

The Servotronic function in the F01/F02 is included in the basic steering and Integral Active Steering (option). This speed-dependent power steering assistance function is implemented by the Servotronic valve at the steering gear.

The Servotronic valve is always activated from the ICM control unit irrespective of the equipment specification. It follows that the ICM control unit also incorporates the logic of the Servotronic function.

Again, regardless of the options fitted, the steering system also contains a proportional valve that is also controlled by the ICM control unit. The volumetric flow in the steering hydraulic circuit can be adjusted electronically assisted by this valve which is why it is also referred to as an "electronic volumetric flow adjustment" valve, or EVV valve for short.

This valve is also controlled by the ICM control unit. The volumetric flow generated by the power steering pump is distributed between a circuit to the steering valve and a bypass circuit according to the level of power steering assistance required. This distribution is infinitely variable. The less power steering assistance is required, the more hydraulic oil is diverted to the bypass circuit. Because the hydraulic oil in the bypass circuit has no task to perform, this means that the power steering pump consumes less power. In this way, the EVV valve contributes to reducing fuel consumption and CO 2 emissions.

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INDEX REFERENCE CHART

Calibration of the sensors integrated into the ICM

The signals from the acceleration and yaw rate sensors integrated into the ICM are referenced to their housing. However, in order to be useful to the dynamic driving systems, these variables must be referenced to the vehicle coordinate system. In order for the ICM control unit to be able to carry out the necessary conversion, it requires corresponding correction values. These are determined during the one-off calibration procedure and stored in the ICM control unit.

Note. The instructions of the diagnostic system must be followed precisely during calibration of the sensors integrated into the ICM. It is particularly important for the vehicle to be standing on a surface that is level in both the longitudinal and lateral directions. If this is not the case, incorrect correction values will be determined that may cause the dynamic driving system to malfunction.

Calibration of the ride-height sensors

The measurement signals from the ride-height sensors are evaluated by means of voltage measurement in the ICM control unit. The ICM control unit cannot calculate the actual ride-level heights in millimeters on the basis of this information alone. To perform this calculation, the ICM control unit must be able to map the voltage signals it receives to reference values. This is the only way to establish a relationship between the measurement signals and the actual ride-level heights at the wheels. These reference values are determined during a synchronization procedure.

Note. The ride-height signals in the ICM must be synchronized in the following cases following replacement of the ICM control unit, following replacement of a ride-height sensor or if prompted to do so by the test schedule of the diagnostic system (due to a fault code memory entry in the ICM). The synchronization does not have to be carried out if a wheel has been changed.

Note. The following points must be observed in order to perform the synchronization using the diagnostic system the air suspension control operations must be blocked (remove fuse for EHC control unit) the ride-level heights must be measured using a tape measure and the rim size must be determined.

The diagnostic system also refers to the ride-level height reference values (design position). These values are used by the diagnostic system and ICM to calculate the reference values for the conversion that are ultimately saved in the ICM control unit.

The ride-height signals in the EHC control unit (if installed) and the ride-height signals in the ICM control unit must be synchronized together.

Calibration of the steering angle sensor in the steering column switch cluster

In addition to the signals from the motor-position sensors of the Integral Active Steering, the ICM control unit also imports the signal from the steering angle sensor in the steering column switch cluster. This is used by the ICM to determine the effective steering angle ("see FUNCTIONS " section).

This is why it is important that the ICM receives a correctly mapped value from the steering angle sensor.

Note. The steering angle sensor must be calibrated if the steering column switch cluster is replaced or reprogrammed. A calibration must also be performed if this is requested in the test schedule of the diagnostic system as the result of a fault code memory entry. The steering angle sensor must be calibrated before the ICM can calculate a correct effective steering angle and make this available via the bus system.

Note. Once the steering angle sensor has been calibrated, the instructions of the diagnostic system must be precisely followed. The vehicle must be standing on even ground during calibration. The steering wheel must be in the straight-ahead position (visually).

Damping Force Adjustment

1. Stored on each EDC satellite control module is the actual individual damper characteristic, making it possible to minimize differences from the specified characteristic arising from manufacturing tolerances
2. From the specified damping force and the damper characteristic data map, the EDC satellite control units calculate the required current to be applied to the damper extension valve and compression valve

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The location of the VDM control unit is dependent on the country in which the vehicle is sold.

1. On left-hand drive vehicles the control unit is fitted inside the passenger compartment near the right A-pillar (as illustrated)
2. On right-hand drive vehicles the control unit is fitted inside the passenger compartment near the left A-pillar

There are two different versions of the VDM control unit according to the equipment options fitted on the vehicle.

1. The basic version of the VDM control unit is used if the vehicle has only the standard VDC equipment
2. The high-speed version of the VDM control unit is used if, as well as the standard VDC system, the vehicle also has ARS Active Roll Stabilization (Dynamic Drive). In that case, the output stages for controlling the ARS valve manifold are also integrated in the VDM control unit.