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Meeting	ACGS Committee Meeting 108 - Gettysburg - October 2011
Agenda Location	9 SUBCOMMITTEE C – AVIONICS AND SYSTEM INTEGRATION 9.2 Knowledge-based Engineering of Actuation Concepts for Flight Control Systems
Title	Knowledge-based Engineering of Actuation Concepts for Flight Control Systems
Presenter	Frank Thielecke
Affiliation	Technical University of Hamburg
Available Downloads*	presentation
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Abstract	Knowledge-based Engineering of Actuation Concepts for Flight Control Systems Prof. Dr.-Ing. F. Thielecke Hamburg University of Technology, Institute for Aircraft Systems Engineering Nesspriel 5, D-21129 Hamburg, frank.thielecke@tuhh.de 1. Trend towards More-Electric Aircraft At the Institute of Aircraft System Engineering of the Hamburg University of Technology several projects in collaboration with industrial partners comprise topical challenges and research trends in More-Electric Aircraft. In this contribution several aspects like complexity for energy flow on aircraft level, electromechanical actuators for primary flight control and nose landing gear, on-board cooling as well as tools for systems architecting are analyses and discussed. The tendency to replace pneumatic and hydraulic systems by electrical solutions in the aerospace industry leads to a decreased power system diversity and therefore to an increase in the complexity of the remaining electrical generation and distribution system. Additionally the system design process of such resulting aircraft systems does not solely include the analysis of serial and parallel structures but also complex system topologies with several bridge structures and a state discrete dynamic behaviour to ensure safety critical and operational reliability targets. These new system architectures offer an optimization potential in redundancy allocation, component decisions and consumer supply which is difficult to manage without the usage of dedicated analysis and optimization tools. 2. Knowledge-based Architecting of High Lift and Hydraulic Systems High lift actuation system design is a highly iterative process. Especially the preliminary design phase, which sets the course for the following design steps, is characterized by uncertain and changing data input. Despite the importance of this early design phase, a specialized and integrated computational support is not available. The objective of the research project WissBaSys is to offer knowledge-based design assistance focused on the preliminary design of high lift actuation systems. Moreover, information concerning a specific drive system architecture and component data can be used for an automated model generation leading to a significant time reduction and enhanced traceability. A capable approach for order reduction of shaft transmission models, as well as the concept for computer-aided modeling, is presented. Based on the general concept of interval-constraint problems to handle the uncertain data and system parameter during this preliminary design phase, it is possible to get consistent system data, to perform design trades in a cost and time-efficient way, to optimize the integrated architecture, and to provide the models for further dynamic simulation analysis incl. in the influence of faults to the system loads. Due to the power of the knowledge-based architecting and sizing concept, a new project is focusing on the adaptation of this method for hydraulic power system design. The presentation describes the new challenges and possible solutions. 3. Model-based Diagnostics of Flight Control Systems A method is presented that allows a model-based development of a fault diagnosis system for an aircraft hydraulic power distribution system. For this, a steady-state model that contains nominal and faulty behaviors is modeled with the TUHH software SPYDER. On the basis of the model, the sensibility of system states to faults is analyzed and conclusions are drawn considering the optimal placement of sensors. In addition, diagnosis rules are derived. 4. Tools for Systems Reliability Analysis The presentation includes a new methodology to analyze and optimize complex fault tolerant aircraft systems in the pre-design phase to support the system engineer. The optimization process is based on the analysis functionalities of the SYRELAN (System Reliability Analysis) tool. This includes a hybrid model, imaging the failure-free system architecture by using Reliability Block Diagrams (RBD) on a first level and the state discrete dynamic system behavior with the use of Concurrent Finite State Machines (CFSM) on a second level. This hybrid model is equivalent to the usage of MARKOV chains but allows a local definition of the state discrete dynamic behavior on event level using five different states: active, active-hot, passive-warm, passive-cold and isolated. Based on the hybrid model a multiple redundant system (MRS) is modeled, which includes all possible architecture solutions. This allows the optimization of the system architecture considering the failure-free nominal state but due to the set of system functions also for degraded system states and a defined number of failed components.