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TU Braunschweig

Gerald Stieglbauer : Model-based Development of Embedded Control Software with TDL and Simulink

In the last couple of years, embedded systems, a former sub-domain as many others within the broad field of computer science, have become major players. Today, 98 percent of all produced microprocessors are used in embedded systems instead of normal desktop computers (including laptops), workstations or high- performance computers. Embedded systems are going to change our daily life continuously. Nearly every day, new innovative products are presented to the market. They are found in cellular phones, other mobile devices like MP3 players and handhelds, washing machines and other modern household appliances, up to cars, airplanes and medical systems.

Although the requirements of embedded software significantly differ to those of traditional software, standard software engineering techniques are still applied to such software in many cases. However, the domain of embedded comes up with its own demands and challenges, which are no longer solvable by traditional approaches, even if they are adapted. In this thesis, the focus is thus a different one: Model-based software development is a promising concept, which currently revolutionizes the development of software in general but as well the design of embedded systems by the introduction of modeling abstractions. To find the right abstraction level for a certain application domain is - metaphorically speaking - the passport to success.

In this thesis, a promising model-based approach called the Timing Definition Language (TDL) is the basis for the design and evaluation of a graphical- oriented and simulation-based software development process for embedded control systems. What makes TDL a good software model is the fact that the developer has not to worry about platform details, for example: will the application be executed on a single node or on a distributed platform; which scheduling scheme ensures the timing behavior; which device drivers copy the values from sensors or to actuators. Therefore, TDL applications are platform independent. This platform independence is ensured by the use of a totally deterministic software model based on the so-called logical execution time (LET). With these characteristics, the software model emphasizes application-centric transparency (simplicity), improves reliability and enables reuse.

As its major contribution, an integration of TDL and the modeling tool Simulink is presented in my thesis. In the meantime, Simulink has been established as the de-facto standard modeling tool in many domains including the field of embedded systems. An integration of TDL and Simulink is thus intended to make TDL available for a broader community.

However, integrating TDL and Simulink is not a one-way street for several reasons. In the thesis, all integration methods known so far are clearly and systematically worked out. Moreover, TDL and the integration with Simulink are set in the context of the MDA and alternative integration approaches (such as an UML profile for TDL) are sketched as well. Regarding the Simulink integration approach, the quality and usefulness of each integration method is evaluated in detail either theoretically or by corresponding implementations. In that context, a tool called the TDL editor suite is developed. This tool is smoothly integrated to Simulink as well and supports a graphical-oriented development of TDL-based applications or even assists the adaptation of existing software projects to TDL paradigms. Moreover, model transformation is applied to generate simulation models for these applications in Simulink as well. Because of the deterministic software model, the functional and the timing behavior of the TDL- based applications do not differ, independently if they are simulated within a simulation environment or executed on a real hardware platform.