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ETAS Understanding INTECRIO
3.1
3.1.1
Challenges of the Electronic Control Unit Development
The electronic control unit development is a highly complex process: Partly because of the constantly increasing requirements of hardware and software, partly because of the development which is frequently spread across several manufacturers and suppliers.
Complexity Through System Requirements
Today, the complete description of an electronic control unit consists of the description of the software to be run on the electronic control unit and the description of the hardware. In most cases, control algorithms and electronic control unit software are closely linked with the target system on which they are executed.
ASCET introduced the first steps to dissolve this mutual dependency by describing the software (the control algorithm) independently of the hardware on which it is to run. ASCET accomplishes this by mapping the signals from the control algorithm onto the signals supplied by the hardware. If it is a rapid prototyping system, the hardware itself is described in a special editor. Different options exist for microcontroller targets.
In the future, this separation of the descriptions of the target hardware and the software will become increasingly more important for the successful implementation of a new electronic control unit.
On the one hand, it allows electronic control unit software and hardware to be
developed in parallel (see Fig. 3-2; the figure is based on the V model). This
shortens the total development time.
Development of electronic systems
Partitioning Integration
Electronic control unit software development
Electronic control unit hardware development
Setpoint encoder and sensor development
Actuator development
...
Fig. 3-2 Overview of the development of electronic systems
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ETAS Understanding INTECRIO
On the other hand, the systems themselves become increasingly more complex, and correlations between the different electronic control units are increasing. The number of electronic control units per vehicle as well as the number of functions per electronic control unit constantly increased during recent
Number
Number of functions per vehicle
ECUs per vehicle
Number of functions per electronic control unit
1970 1980 1990 2000 Time
Fig. 3-3 Functions and electronic control units per vehicle (in The Need for
Systems Engineering. An Automotive Project Perspective , Key Note at the 2 nd European Systems Engineering Conference, Munich, H.-
G. Frischkorn, H. Negele, J. Meisenzahl)
Car manufacturers and suppliers are faced with an enormous cost pressure; they are forced to reduce costs by means of reuse and variants. That is, a certain functionality is used for different vehicle types of a car manufacturer, and vehicle variants are created via software properties. The difference between two variants of a vehicle may consist only in the presence or absence of a certain software functionality and the corresponding sensors and actuators.
For this purpose, the hardware-independent development of the functionality is a great advantage since this allows the functionality to be used universally.
The costs can also be reduced by arranging the software components on the smallest possible hardware system. This limits the number of electronic control units in the vehicle, but it may require the distribution of the components of one functionality to several electronic control units.
In addition, new functionality can be added to a vehicle by means of so-called virtual sensors. These are sensors that do not measure their signals, but calculate them. This calculation can be performed by combining physical models with real sensor values. A good example is tire slip. Tire slip cannot be measured, but by combining the tire model with the current acceleration (measured by the electronic stability program ESP) and the current torque (from the engine control), it is possible to calculate the slip.
Today's vehicle can contain up to 120 microcontrollers that are mostly connected with each other via serial bus systems. The execution of a specific control algorithm depends not only on the electronic control unit on which it runs, but also on the inputs and outputs of other electronic control units.
An example of an already distributed control algorithm is the electronic stability program (ESP) and the engine control.
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