Civil Engineering Reference
In-Depth Information
2.5
Partial Networking
During the last years, the number of comfort function in a car is dramatically in-
creased. New functions like seat position and heating, window lift and so on were
added. These additional functions increase not only the comfort but also the cur-
rent consumption. Every function consumes typically 50 mA (without actuators)
independent of the fact that this function is used or not. During a start-up of a car,
all ECUs will be ramped up in parallel. This ends in a high current peak (up to 25 A
without actuators) but this is not necessary. Not all ECUs are required for the start of
the engine. A distributed ramp-up of the ECUs will be much more. A 100-ms delay
has no impact on the comfort but helps to reduce the load on the battery. To reduce
the current consumption and the CO2 emission, it must be possible to deactivate the
functions that are not needed during active CAN communication. An impact on the
comfort is not allowed. Two different concepts are available and established. One
concept based on a microcontroller modification is called pretended networking and
the other concept is based on a transceiver solution.
The microcontroller uses the internal CAN communication controller to moni-
tor the bus communication like established. However, all other functions in the
microcontroller are deactivated. Through the detection of the CAN communication
controller, an identifier, the rest of the micro will be awaked and the message can be
analysed. For this solution, a CAN transceiver with optimized current consumption
set into receive-only mode is recommended.
This technology requires a new generation of transceivers that can monitor the
CAN bus traffic to detect the well defined wake messages. To reduce the current
consumption of an ECU, voltage regulator and microcontroller are switched off.
The current consumption in this solution is much lower than in the microcontroller
solution. However, with this solution only one ID for wake-up is possible.
2.5.1
Motivation
In the last years, the requirements for eco-friendliness, drive engineering and CO
2
emissions have been drastically changed. In future, the vehicle manufacturer has
to pay penalties for its vehicles which exceed the maximum allowed carbon di-
oxide emissions. Driven by ecological sensibility of the consumer and the limited
reserves of conventional used fuel resources, the development of alternative drive
engineering and the optimization of well-established drive concepts increased
significantly. However, a second trend says that the vehicle manufacturers have
to face an increase in applications and comfort which leads to an increase in elec-
trification inside the car. An increment of electronic functions inside a car, and
with it an increment of ECUs per car, leads to a higher power consumption which
results also in a higher fuel consumption. An increase in functionality usually
implies an increase ofelectric power supply which usually must be compensated
with power from fuel. Therefore, optimizing the electrical power consumption is
