Technical data

7
7
Functions
DME S85B50
Functional Principle of the Digital Motor Electronics
Engine torque control
The EDR satellite serves the purpose of
controlling the engine torque. The main
control variable is the quantity of fresh air (air/
fuel mixture) supplied to the engine that can
be varied by the position of the ten individual
throttle valves and the two idle speed throttle
valves.
For the control system, the V 10 engine is
divided into two identical blocks (cylinder
banks) each with five cylinders. Each cylinder
bank has an idle speed throttle valve and five
individual throttle valves.
The five individual throttle valves are
mechanically coupled with each other per
cylinder bank.
The position of the idle throttle valve and the
position of the five individual throttle valves are
controlled by two actuators per cylinder bank
an idle speed actuator (LLS) and an electric
throttle valve actuator (EDR).
The entire intake air control system therefore
consists of four actuator motors for the throttle
valves.
For safety reasons, each throttle valve is
equipped with a return spring that closes the
throttle valves in the event of the respective
actuator failing.
All four actuator motors are controlled by the
central engine management (DME).
The DME calculates the target load signal for
both cylinder banks from the input variables
such as driver's load choice via the pedal value
sensor, coolant temperature and from
interventions of other control units (DSC,
ACC, ...). The DME then determines a set
position for the throttle valves (set angle) from
this target load signal. Initially, the potential of
the idle throttle valves is exhausted before the
individual throttle valves are opened to allow a
substantially greater volume of air to be drawn
in.
Communication with the actuator motors
takes place via the CAN busses. The two EDR
are addressed via a separate CAN-bus and the
two LLS via a common LLS-SMG CAN-bus.
In order to set the engine power output
corresponding to the input variables, the DME
specifies for the actuators a target value
relating to the throttle valve angle which the
actuators then assume.
One of the two Hall sensors of the throttle
valve sensor 1 (DKG 1) is made available to the
electric throttle valve actuator 1 (EDR 1) for
the purpose of controlling the individual
throttle valves.
The second Hall sensor of DKG 1 is powered
and read directly by the DME and only serves
the purpose of monitoring the control of the
EDR 1. (the same applies to actuator 2
(EDR 2)).
The two idle actuators feature an internal
incremental angle transducer for controlling
the throttle valve angle of the idle speed
throttle valves. The sensor value is sent back
to the DME via the CAN-bus.
The DME determines the current actual load
signal from the directly read throttle valve
sensors and the feedback signals of the LLS in
order to check the setting of the throttle
valves. The plausibility of this load signal is
checked against the signals of the two hot-film
air mass meters (HFM) that measure the
intake air masses per cylinder bank.
If the deviations between the target and actual
load signal are too great, the plausibility is
additionally checked against the signal from
the oxygen sensor. The DME responds with a
corresponding fault reaction.