X Series E83 X3 3.0d (M57TU) OFFRD
[more ...]
-
DSC control unit (Dynamic Stability Control)
The DSC control unit delivers the car's road speed signal. The DSC control unit and SVT control unit are
connected by the PT-CAN.
-
DME or DDE (Digital Engine Electronics or Digital Diesel Electronics DDE)
The Servotronic receives the signal of whether the engine is running from the DME or DDE over the PT-CAN.
The Servotronic only activates the Servotronic valve when the engine is running.
-
Instrument cluster (KOMBI)
The instrument cluster delivers the terminal status (e.g. terminal 15 ON) and the kilometer reading.
The following actuators are controlled by the Servotronic:
-
Servotronic valve
The Servotronic valve is an electro-hydraulic converter located in the power-assisted steering oil circuit. The
Servotronic valve restricts the hydraulic current and consequently reduces the hydraulic pressure.
The Servotronic valve is activated by a characteristic curve delivered by the SVT control unit.
[more ...]
System functions
The Servotronic is based upon the following system functions:
-
Initialisation of the Servotronic
-
Recording of the speed
-
Supplying the Servotronic valve with power
-
Undervoltage detection and overvoltage detection
Initialisation of the Servotronic
The Servotronic is active from terminal 15 ON.
A short initialisation phase for the Servotronic (under 1 second) is necessary when the engine starts in order to
reach the characteristic curve for a low road speed as fast as possible.
A plausibility check for supplying the Servotronic valve is performed during the initialisation phase.
Recording of the speed
The road-speed signal is calculated by the DSC and supplied to the PT-CAN. The Servotronic specifies an
acceleration value for plausibility of the road-speed signal. A road speed is calculated from the acceleration
value.
At a low acceleration the road-speed signal supplied by the DSC is used.
At a higher acceleration the Servotronic control unit calculates the road speed internally. The road speed is
stored in the Servotronic control unit.
Supplying the Servotronic valve with power
The Servotronic valve is supplied with power in response to the car's road speed. The power-assisted steering
characteristic is memorised in a characteristic curve. The characteristic curve specifies the power based on the
car's road speed.
The characteristic curve is written using 16 reference points.
The Servotronic valve is no longer supplied with power when the engine is OFF (over the PT-CAN). Minimum
steering force support is set (high road speed) when the Servotronic valve is no longer supplied with power.
Equally, the Servotronic valve is also no longer supplied with power if there is a fault-memory entry.
SBT Servotronic E83
BMW AG - TIS
16.02.2013 00:56
Issue status (12/2007) Valid only until next DVD is issued
Copyright
Page - 2 -