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ABSTRACT: Increasingly intelligent energy-management and safety systems are developed to realize safe and economic automobiles. The realization of these systems is only possible with complex and distributed software. This development poses a challenge for verification and validation. Upcoming standards like ISO 26262 provide requirements for verification and validation during development phases. Advanced test methods are requested for safety critical functions. Formal specification of requirements and appropriate testing strategies in different stages of the development cycle are part of it. In this paper we present our approach to formalize the requirements specification by test models. These models serve as basis for the following testing activities, including the automated derivation of executable test cases from it. Test cases can be derived statistically, randomly on the basis of operational profiles, and deterministically in order to perform different testing strategies. We have applied our approach with a large German OEM in different development stages of active safety and energy management functionalities. The test cases were executed in model-in-the-loop and in hardware-in-the-loop simulation. Errors were identified with our approach both in the requirement specification and in the implementation that were not discovered before.
Design, Automation & Test in Europe Conference & Exhibition (DATE), 2011; 04/2011
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ABSTRACT: Model-driven testing based on Markov chain usage models (MCUM) is an established method to address testing issues. It is not possible, however, to describe by means of MCUMs the timing of stimuli and time dependencies between inputs and outputs of a system. Additional concepts and information is needed. In this paper it is presented how Timed Usage Models (TUM) can be used to solve this issue. Concepts for stimuli and responses are introduced, that comprise that something must happen before a time interval, after a time interval or within a time interval. It is presented how this can be described by TUMs. TUMs are enhanced MCUMs that allow the usage of distributions of time. The computations for TUMs are based on semi-Markov processes and are therefore not restricted to discrete steps in time. Therefore, indicators and metrics for the test planning and management can be derived that take into account time. Test cases can be derived that reflect variability in inputs and, additionally, variability in timing of inputs. Complex real time systems require a test method that provides the possibility to handle the effect of timing and variability in timing of inputs to the system.
Systems Conference, 2010 4th Annual IEEE; 05/2010
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ABSTRACT: Modern cars comprise a multitude of electronic features which are implemented in tens of communicating control units. To connect these in-car embedded systems, the CAN bus offers a sustainable performance, hence it is used as a widespread communication infrastructure, even for safety critical applications. However, CAN media access is priority based and performed competitive and non-preemptive. Thus, assessing the worst case end-to-end delay is inevitable in order to provide safe and efficient operation of functions with hard real-time properties. In this paper, we use the analytical method of network calculus to determine guaranteed upper bounds for transmission delays of all CAN priorities. We demonstrate the applicability of our approach by investigating current real-life CAN communication data from the German car manufacturer Audi.
Vehicular Technology Conference, 2008. VTC Spring 2008. IEEE; 06/2008
