The article describes a case study methodology that is applied in RAFAEL for the verification and validation (V&V) of complex and multi-disciplinary systems. Various methods of V&V are found within the nature and the type of the product. Some applications use methods that are prevalent in the electronics industry. There are other methods that are based on international standards such as V&V for airborne structures. Complex systems are characterized by a number of special issues which do not allow for a simple implementation of V&V mentioned above. The following issues are unique to complex systems: the design consists of multi-disciplinary subjects, the cost of the life cycle is high, it takes a long time for hardware production and for the completion of development, there is a demand for high reliability, the V&V process contains a multiplicity of parameters and the system has multiple interfaces. For systems of this nature there is no V&V process available in use and it is necessary to implement a tailored-made method. This method of V&V deals with the two main quantitative and qualitative questions of proof: (a) how does the system and sub-system behave under external environmental conditions?, (b) how does the system and sub-system functioning under the existence of differences between sub-systems and components which are supplied in the delivery stage of the life cycle (i.e. geometrical and performance tolerances, time depending parameters)? The new approach is to design a process of V&V in the early stages of the product life cycle. It is different from the conventional approach which performs the reliability tests at the completion of the product development via the approval examinations. The steps in building updated V&V process for complex system are: 1. Identification of the functionality specification of the system and deriving from it the V&V building blocks. 2. Breaking down the system into independent factors and connecting to each factor the relevant part of the physical structures. For each component in the structures it is necessary to identify its functionality and whether if the specification comply with demands. 3. Building computational, analytical and functional models which describe the system, sub-system and its components behavior and sensitivity analysis. 4. Experimental validation for individual sub-systems and components. The purposes are to verify reliability of the models, to validate the margin of safety needed and to find out the failure threshold. 5. Experimental validation at a higher level. The purposes of this stage are to examine the internal and external interfaces, to verify the approach of the separation of parameters and to validate the system functionality. This new approach will be demonstrated on an electromechanical system.

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