Date and place of thesis defense:
18.09.2009. Faculty of Mechanical Engineering
mr. sc. Muharem ©abić
prof. dr. Safet Brdarević
An approach to redesign of structural layout of aircraft maintenance system
Research presented in this thesis tries to set essential fundamentals for research of system reconfigurability. Identification of basic system features as multi efficiency, evolvability and survivability enabled by reconfigurability lead to quantity analysis of system design. Key characteristics of reconfigurable system are modularity, convertibility, scalability, integrability, customization and diagnosability.
A reconfigurable system can be modeled as a system that tries to produce a desired output and fulfill some objective at various points during its operation by undergoing some form of on-line reconfiguration. On-line reconfiguration represents system functionality change adjusting some reconfigurable hardware characteristics and supporting system software without shutting down system operation. When system output requires changes caused by environment and demand request which are above on-line reconfiguration bandwidth, the system shuts down to alter its capabilities to meet the new objectives. The system upgrade can be considered as capability and functionality increase of reconfigurable system when capacity and new functionalities are needed.
Reconfigurable systems can be inverted to various configurations (or states) through system form or its function changes in order to get desired system output to satisfy required reconfiguration time and expenses. The reconfigurability is distinctive design system feature which defines ease of internal changes and extent of system reconfigurability. Any system can be considered as reconfigurable if reconfiguration time and expenses for setting a new configuration is in reasonable limits.
A set of system configuration is defined as set of specific discrete or continuous states which consist of different form and/or functionality performance related to existing circumstances. Difference could appear in the form of functionality attributes or in the form of any externally added function. Systems which have in the stage of initial design embodied functionalities are multifunctional systems and could be not considered as reconfigurable systems. Systems which have been undergone to a reconfiguration before achieving new modified function or goal can be considered as reconfigurable. The convention is accepted that one way reconfiguration systems can not be considered as reconfigurable. Changes that take place in the process of system reconfiguration must be reversible what give the system reconfigurable features.
In the research, fundamental characteristics of reconfigurability of aircraft maintenance system and their limitations are surveyed. Proposed model offers possibility of quantifying of reconfiguration process and exact way of measuring of reconfiguration conduction. Aircraft maintenance system reconfiguration stands for physical and information change of current system configurations. The physical reconfiguration is constituted of changing relative location of basic departments and adding hardware modules to lower hierarchy elements. The information reconfiguration means exchange or adding of software modules, controlers and differnt interfaces. Physical and information reconfiguration of system are parts of unique process and mutually supplemented.
In the aircraft maintenance system case studies, new departments were added due to change of product mix and physical reconfiguration is quantified. The proposed math model merges optimal locations methods with location placement methods in the presence of barriers and using yielded data for calculating of reconfigurability coefficient. The reconfigurability coefficient of proposed system configuration is used as criteria for reconfigurable system layout solution and together with economical analysis is part of decision making process.
Briefly, results and notices derived from carried research indicate that in case of no short term expanses decrease than long term competitiveness and market sustainability, reconfigurability of system is key characteristic. Those systems requires initial large investment but on long term gain economical benefit and quick adaptability on new market requirements.
Key words: aircraft maintenance system, layout, modularity, reconfigurabiity, reconfigurability factor