EMF control unit

As on the E70, the EMF control unit on the F01/F02 is integrated in the actuator unit casing and is also identical in design to the one on the E70. It is the actuation controller for the EMF functions. It therefore controls the electric motor and reads the signals from the force sensor.

The most important control signal from outside is that from the parking brake button. The parking brake button is directly wired to the EMF control unit.

The EMF control unit is connected to the PTCAN. Integrated in the EMF control unit is one of the two terminal resistors for the PT-CAN. The EMF control unit communicates via the PT-CAN with its most important partner, the DSC control unit. As the DSC control unit is only connected to the FlexRay, the central gateway module is required to transfer the signals between the PT-CAN and the FlexRay.

A special place among the input signals is occupied by the information relating to vehicle standstill. The EMF actuator unit must not be activated while the vehicle is moving but rather only when it is stationary. Otherwise, the vehicle handling would become unstable due to the rear wheels locking up. The EMF control unit detects vehicle standstill on the basis of the following three input signals:

• Road speed (provided by Integrated Chassis Management via bus systems)
• Rear axle speed (provided by engine management via PT-CAN)
• Wheel-speed signal "DFA_EMF" (calculated by Dynamic Stability Control and transmitted via direct wired link to EMF control unit).

Only when those three signals definitively indicate vehicle standstill does the EMF control unit allow operation of the actuator unit.

Fig 1: Overview Of Connections On EMF Actuator Unit

Courtesy of BMW OF NORTH AMERICA, INC.