The software development is one of the most important activities of ThyssenKrupp Presta Hungary Kft. The embedded programs of the power-assisted steering systems, designed and manufactured by the company, are entirely produced in the development centre in Budapest including development, integration and testing as well. More than half of the specialists of the Budapest unit deal with these activities.

The software development on the one hand is a classical embedded development, since the program is built-in in a quite complex equipment and does not have a direct user interface. On the other hand it is much different from other embedded developments (e.g. from an ECG equipment or from a mobile phone), since it is part of an extremely safety-critical equipment.

The basic function – in other words, the car would turn to the right, when the steering wheel is turned to the right – is not too complicated. The following circumstances make the task very complex:

• The car manufacturers impose very high requirements for the system and its operation is coordinated with the operation of other control devices of the car.
• The system is manufactured in large numbers (million pieces per year), therefore the hardware must be designed as highly price-optimized. As a result of this, what is only possible should be solved by software functions in order to simplify the hardware, for instance, where it is possible we replace sensors by estimation algorithm.
• Since the system is safety-critical, it continuously shall be checked for proper functioning with redundant software- and hardware solutions.

Due to the above criteria, the originally simple task imposes a number of substantial demands on the developers:

• High level control technique in the steering algorithm;
• Motor control allowing optimal control and exact setpoint tracking;
• Complex measurement techniques and signal processing for the above algorithms and for the self-diagnostic;
• Real time modelling of different modules of the system for the purpose of control and parameter estimation;
• Highly reliable communication with further control units of the car;
• Providing real-time runtime environment for software modules implementing the above.

To develop a software that fully meets these requirements, the company must meet a very strict development process. This is partly required by International standards (SPICE, ISO-26262, etc.), and partly the effective development necessitates it. Since software development takes place within the ThyssenKrupp Presta group only in Budapest, the development of these processes are also the task of ours. Characteristics of the development processes are as follows:

• Model driven system- and software development using UML, SysML, Matlab Simulink and ARXML modelling environments;
• Structured software architecture design in conformity with AUTOSAR standard, using reusable software components;
• Software documentation that allows requirements traceability;
• Independent organisation structure for software development and -testing;
• Use of rapid prototyping development environment;
• Automatic generation of significant part of the code, basically written in C, from the modelling language;
• Use of strict coding- and modelling rules.

All of these methods allow steering systems designed by ThyssenKrupp Presta to be such highly reliable and high quality parts of the cars, that meet the high-level requirements of car manufacturers, and also can be produced economically.