Concept of an active access for a minimally invasive robotic system for the inspection of aircraft kerosene tanks

The aim of this thesis was to develop a pool of solution concepts for the design of an active access for a minimally invasive robotic system for the inspection of aircraft kerosene tanks. First a short overview of the overall topic of aircraft fuel tank maintenance and aircraft wing fuel tanks was given. An introduction into the parent project FuTaMa and the motivation of the Access Mechanism followed. The theoretical background given in chapter 2 provides fundamental information about the design methodologies, that were used within this Thesis. According to the conceptual design methods the design process was started with the first step ’Clarification and specification of the problem’ establishing a detailed understanding of the problem and the requirements of the system to be designed. Therefore the aircraft wing fuel tank and the Eeloscope , as well as the process of the visual inspection were analysed by researching literature and by discussing the initial conditions in a group session. Several access ports were analysed in terms of the suitability as an entry port for the Eeloscope . After the analysis the access panel was chosen by elimination as the entry point for the Eeloscope . Then the scope of the system was set according to the task description including the aircraft fuel tank, the Eeloscope , the access and the feeder functionality. Based on the results of the problem analysis the problem description was defined in one short and precise sentence namely: ’Design of a system that establishes a leak tight access of the endoscopic diving robot Eeloscope to an aircraft wing fuel, entering the fuel tank at an access panel and generates a bidirectional feeding motion of the Eeloscope ’. As this problem description did not cover all the requirements and restrictions derived in the problem analysis, a list of requirements was created including requirements and restrictions like explosion proofness, leakage integrity etc.. In the next step of the design process, the different required functions of the Access Mechanism were stated and their structural relations were determined and displayed in an functional tree. For the derived functions, potential principle solutions were found by applying different problem solving methods like ’Analogy review’ or ’Brainstorming’. The collected solution principles were sorted, pre-assessed and added to the ordering scheme ’Morphological box’. In the pre-assessment of the sub-function ’Seal off entry port’ it was observed that no founded solution principle will lead to an satisfactory seal of the entry port. Hence an iterative step was introduced starting with expanding the scope of the system including the storage of the hose batch. After the update of the list of requirements and the functional tree, new solution principles to the additional functions that arose, were found and added to a new ’Morphological box’. Next several solution concepts were derived by combining the solution principles contained in the morphological boxes. Then the concepts were accessed by the ’Weighted Point Scoring’ method with the result of feasible solution concepts. In the last but second step of the design process a final solution concept was derived by selecting the best solution concepts of the sub systems. The final solutions concept consists of a new designed access panel which contains an entry port for the Eeloscope . At the access panel the feeder unit is attached by a Cam-Lock-coupling. The feeding motion is generated by two counter rotating concave rolls. The hose batch is located between the concave rolls. The rolls are driven by an electrical motor and a gear and belt setup. The feeding unit is connected to a hose storage unit by a hose equipped again with Cam-Lock couplings. The hose storage unit consist of a barrel that shall enable a helix-shaped arrangement of the hose batch to store it compactly. Finally the solution concept was evaluated by theoretically executing the future maintenance process and by applying a Failure Mode and Effects Analysis (FMEA). At the end a conclusion about the design process and the resulting solution concept was drawn and an outlook was given