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A Model-Based Systems Engineering Approach for Efficient System Architecture Representation in Conceptual Design: A Case Study for Flight Control Systems


A Model-Based Systems Engineering Approach for Efficient System Architecture Representation in Conceptual Design: A Case Study for Flight Control Systems

Jeyaraj, Andrew Kingsley ORCID: https://orcid.org/0000-0002-6032-5451 (2019) A Model-Based Systems Engineering Approach for Efficient System Architecture Representation in Conceptual Design: A Case Study for Flight Control Systems. Masters thesis, Concordia University.

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The reduction of the environmental footprint of aviation requires the development of more efficient aircraft. Emergent technologies in aircraft systems, such as more-electrical aircraft, are potential enablers for the next generation of aircraft. To support the adoption of these new technologies and to tackle the underlying integration challenges, aircraft system architectures need to be considered earlier in the aircraft design process, specifically within the conceptual design stage. To deal with the complexity and to make the system architecture development process more efficient and effective, a key enabler is to improve the representation of system architectures early in the design process. Introducing better architecture representations removes ambiguity and allows engineers to develop a shared understanding of the system. Model Based Systems Engineering (MBSE) has emerged as a systematic methodology to address complexity in systems design and overcome the drawbacks of the traditional paper based systems engineering approach used in aircraft development. This thesis investigates the use of the ARCADIA/Capella MBSE environment for the representation and specification of aircraft systems architecture in conceptual design. This thesis includes survey on the needs for system architecture representations in conceptual design. A methodology is developed within Capella to create architecture representations that are suitable for use in conceptual design. The primary flight control systems (PFCS), which by extension also includes the associated power systems, is selected to illustrate the proposed methodology. The proposed methodology consists of capturing architectural features such as interfaces, exchanges and variability. A catalog of modelling artifacts representing the various flight control actuation technologies at system level, logical and physical level has been developed. These elements can be combined to define any primary flight control system architecture. The model-based specification addresses the need to define rapidly many architecture variants for conventional and more-electrical technologies. The developed methodology is applicable to other aircraft systems. Overall, this work is an initial step towards introducing MBSE earlier in the aircraft development process thereby making it more efficient and responsive to the emerging needs of aircraft development.

Divisions:Concordia University > Gina Cody School of Engineering and Computer Science > Mechanical, Industrial and Aerospace Engineering
Item Type:Thesis (Masters)
Authors:Jeyaraj, Andrew Kingsley
Institution:Concordia University
Degree Name:M.A. Sc.
Program:Mechanical Engineering
Date:12 April 2019
Thesis Supervisor(s):Susan, Liscouet-Hanke
Keywords:Aircraft Design, Conceptual Design, Aircraft Systems, Aircraft System Architecture, Design Space Exploration, Capella, ARCADIA, Aircraft System Architecture Representation, System Architecture Definition, System Architecture Evaluation, Representation, Actuation Technology, More Electric Aircraft, All Electric Aircraft, Flight Control System, Primary Flight Control System Architecture
ID Code:985353
Deposited By: Andrew Jeyaraj
Deposited On:08 Jul 2019 13:56
Last Modified:08 Jul 2019 13:56


[1] P. Pisquali, “Airbus A380 History - Modern Airliners.” [Online]. Available: http://www.modernairliners.com/airbus-a380/airbus-a380_history/. [Accessed: 25-Mar-2019].
[2] D. Greising and J. Johnsson, “Behind Boeing’s 787 delays Problems at one of the smallest suppliers in Dreamliner program causing ripple effect,” 2007. [Online]. Available: https://www.chicagotribune.com/news/ct-xpm-2007-12-08-0712070870-story.html. [Accessed: 25-Mar-2019].
[3] Bombardier Inc., “Bombardier Aerospace Granted Authority to Offer CSeries Aircraft to Customers - Bombardier,” 2015. [Online]. Available: https://www.bombardier.com/en/media/newsList/details.158-bombardier-aerospace-granted-authority-to-offer-cseries-aircraft-to-customers.bombardiercom.html. [Accessed: 25-Mar-2019].
[4] D. Scholz, “Section 12: Aircraft Systems,” in The Standard Handbook for Aeronautical and Astronautical Engineers, New York: McGraw Hill, 2002, p. 12.1.
[5] International Air Transport Association, “IATA Technology Roadmap,” 2013.
[6] SAE International, “ARP4754A: Development of Civil Aircraft and Systems,” 2011.
[7] J. Gausemeier and S. Moehringer, “VDI 2206- A New Guideline for the Design of Mechatronic Systems,” in IFAC Proceedings Volumes, 2002, vol. 35, pp. 785–790.
[8] D. Raymer, Aircraft Design: A Conceptual Approach 5e and RDSWin STUDENT. American Institute of Aeronautics and Astronautics,Inc., 2012.
[9] J. Roskam, Airplane design: Part I. Lawrence, Kansas: Roskam Aviation and Engineering Corp., 2015.
[10] D. P. Raymer, Aircraft Design: A conceptual approach. Reston, VA: AIAA, 2006.
[11] Air Transport Association, “ATA 100.” [Online]. Available: http://www.s-techent.com/ATA100.htm. [Accessed: 12-Mar-2019].
[12] The Boeing Company, “AERO - 787 No-Bleed Systems,” 2008. [Online]. Available: https://www.boeing.com/commercial/aeromagazine/articles/qtr_4_07/article_02_3.html. [Accessed: 25-Mar-2019].
[13] D. M. Judt and C. P. Lawson, “Application of an automated aircraft architecture generation and analysis tool to unmanned aerial vehicle subsystem design.,” in Proceedings of the Institution of Mechanical Engineers. Part G, Journal of Aerospace Engineering, 2015, vol. 229, no. 9, pp. 1690–1708.
[14] M. Hornung, “Aircraft Systems ACS2017 Lecture 1,” Introduction to Aircraft Systems. Munich, Germany, 2017.
[15] L. Faleiro, “Power Optimised Aircraft A keystone in European research in More Electric Aircraft Equipment Systems,” 2006.
[16] I. Chakraborty and D. N. Mavris, “Integrated Assessment of Aircraft and Novel Subsystems Architectures in Early Design,” J. Aircr., vol. 54, no. 4, pp. 1268–1282, 2017.
[17] B. Sarlioglu and C. T. Morris, “More Electric Aircraft: Review, Challenges, and Opportunities for Commercial Transport Aircraft,” IEEE Trans. Transp. Electrif., vol. 1, no. 1, pp. 54–64, 2015.
[18] M. Noriko, T. Michiya, and O. Hitoshi, “Moving to an All-Electric Aircraft System,” IHI Eng. Rev., vol. 47, no. 1, pp. 33–39, 2014.
[19] P. W. Wheeler, J. C. Clare, A. Trentin, and S. Bozhko, “An overview of the more electrical aircraft,” Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng., vol. 227, no. 4, pp. 578–585, Dec. 2012.
[20] D. Judt and C. P. Lawson, “Methodology for automated aircraft systems architecture enumeration and analysis,” in AIAA ATIO, 2012.
[21] J. Ölvander, B. Lundén, and H. Gavel, “A computerized optimization framework for the morphological matrix applied to aircraft conceptual design,” Comput. Des., vol. 41, no. 3, pp. 187–196, 2009.
[22] H. Gavel, J. Oelvander, B. Johansson, and others, “Aircraft fuel system synthesis aided by interactive morphology and optimization.,” in 45th AIAA Aerospace Sciences Meeting, 2007.
[23] F. Villeneuve, “A method for concept and technology exploration of aerospace architectures,” Georgia Institute of Technology, 2007.
[24] “Systems Engineering Overview - SEBoK.” [Online]. Available: https://sebokwiki.org/wiki/Systems_Engineering_Overview. [Accessed: 25-Mar-2019].
[25] INCOSE, “Systems Engineering Vision 2020,” 2004.
[26] S. Friedenthal, A Practical Guide to SysML: The Systems Modeling Language. Burlington: Elsevier/Morgan Kaufmann Publishers, 2008.
[27] “Model-Based Systems Engineering (MBSE) (glossary) - SEBoK.” [Online]. Available: https://www.sebokwiki.org/wiki/Model-Based_Systems_Engineering_(MBSE)_(glossary). [Accessed: 04-Apr-2019].
[28] S. Liscouet-Hanke, B. R. Mohan, P. Jeyarajan Nelson, C. Lavoie, and S. Dufresne, “Evaluating a Model-Based Systems Engineering approach for the conceptual design of advanced aircraft high-lift system architectures,” in Canadian Aeronautics and Space Institute AERO 2017, 2017.
[29] D. Huart and O. Olechowski, “Towards a Model-Based Systems Lifecycle: CPCS from design to operations,” in International Workshop on Aircraft System Technologies, 2017.
[30] S. Liscouët-Hanke, “A Model Based Methodology for Integrated Preliminary Sizing and Analysis of Aircraft Power System Architectures,” Université Toulouse III - Paul Sabatier, 2008.
[31] E. Kang, E. Jackson, and W. Schulte, “An Approach for Effective Design Space Exploration BT - Foundations of Computer Software. Modeling, Development, and Verification of Adaptive Systems,” 2011, pp. 33–54.
[32] F. Zwicky, Morphological Analysis and Construction. New York: Wiley Inter-science, 1948.
[33] K. Griendling and D. Mavris, “A Systems Engineering Approach and Case Study for Technology Infusion for Aircraft Conceptual Design,” in Advances in Systems Engineering, American Institute of Aeronautics and Astronautics, Inc., 2016, pp. 219–268.
[34] W. Engler, P. Biltgen, and D. Mavris, “Concept Selection Using an Interactive Reconfigurable Matrix of Alternatives (IRMA),” in 45th AIAA Aerospace Sciences Meeting and Exhibit, American Institute of Aeronautics and Astronautics, 2007.
[35] C. P. Frank, R. A. Marlier, O. J. Pinon-Fischer, and D. N. Mavris, “Evolutionary multi-objective multi-architecture design space exploration methodology,” Optim. Eng., vol. 19, no. 2, pp. 359–381, 2018.
[36] F. Villeneuve and D. Mavris, “A New Method of Architecture Selection for Launch Vehicles,” in AIAA/CIRA 13th International Space Planes and Hypersonics Systems and Technologies Conference, 2005.
[37] R. Perez, J. Chung, and K. Behdinan, “Aircraft conceptual design using genetic algorithms,” in 8th Symposium on Multidisciplinary Analysis and Optimization, 2000.
[38] L. Blasi, L. Iuspa, and G. D. Core, “Conceptual aircraft design based on a multiconstraint genetic optimizer,” J. Aircr., vol. 37, no. 2, pp. 351–354, 1999.
[39] W. Crossley, E. T. Martin, and D. W. Fanjoy, “A multiobjective investigation of 50-seat commuter aircraft using genetic algorithm,” AIAA Pap., pp. 2001–5247, 2001.
[40] L. Chi, H. Qiu, Z. Chen, and L. Ke, A Design Space Exploration Method Using Artificial Neural Networks and Metamodeling, vol. 544. 2012.
[41] E. Ipek, S. A. McKee, K. Singh, R. Caruana, B. R. de Supinski, and M. Schulz, “Efficient architectural design space exploration via predictive modeling,” ACM Trans. Archit. Code Optim., vol. 4, no. 4, pp. 1–34, Jan. 2008.
[42] T. Lammering, “Integration of aircraft systems into conceptual design synthesis,” RTWH Aachen, Aachen, 2014.
[43] S. Liscouët-Hanke, J.-C. Maré, and S. Pufe, “Simulation Framework for Aircraft Power System Architecting,” J. Aircr., vol. 46, no. 4, pp. 1375–1380, Jul. 2009.
[44] I. Chakraborty and D. Mavris, “Assessing Impact of Epistemic and Technological Uncertainty on Aircraft Subsystem Architectures.” 2016.
[45] I. Chakraborty and D. N. Mavris, “Heuristic Definition, Evaluation, and Impact Decomposition of Aircraft Subsystem Architectures,” in 16th AIAA Aviation Technology, Integration, and Operations Conference, 2016.
[46] NASA, “Systems Engineering Handbook,” 2017.
[47] A. T. Morris and J. C. Breidenthal, “The Necessity of Functional Analysis for Space Exploration Programs.”
[48] E. L. Cole, “Functional analysis: a system conceptual design tool [and application to ATC system],” IEEE Trans. Aerosp. Electron. Syst., vol. 34, no. 2, pp. 354–365, 1998.
[49] N. Viola, S. Corpino, M. Fioriti, and F. Stesina, “Functional Analysis in Systems Engineering: Methodology and Applications,” in Systems Engineering - Practice and Theory, pp. 71–96.
[50] D. Raudberget, C. Levandowski, O. Isaksson, T. Kipouros, H. Johannesson, and J. Clarkson, “Modelling and assessing platform architectures in pre-embodiment phases through set-based evaluation and change propagation,” J. Aerosp. Oper., vol. 3, no. 3,4, pp. 203–221, 2015.
[51] D. S. Raudberget, M. T. Michaelis, and H. L. Johannesson, “Combining set-based concurrent engineering and function — Means modelling to manage platform-based product family design,” in 2014 IEEE International Conference on Industrial Engineering and Engineering Management, 2014, pp. 399–403.
[52] D. Reckzeh, Multifunctional wing moveables: Design of the A350XWB and the way to future concepts. 2014.
[53] T. Lampl, D. Sauterleute, and M. Hornung, “A Functional-Driven Design Approach for Advanced Flight Control Systems of Commercial Transport Aircraft,” in 6th International Workshop on Aircraft System Technologies, 2017.
[54] T. Lampl, T. Wolf, and M. Hornung, “Preliminary design of advanced flight control system architectures for commercial transport aircraft,” CEAS Aeronaut. J., pp. 1–10.
[55] O. Bertram, A. Berres, and H. Schumann, Function-driven Design Process of a Flight Control System for a Blended Wing Body Configuration. 2015.
[56] M. Armstrong, C. De Tenorio, D. Mavris, and E. Garcia, “Function Based Architecture Design Space Definition and Exploration,” in The 26th Congress of ICAS and 8th AIAA ATIO, American Institute of Aeronautics and Astronautics, 2008.
[57] M. Armstrong, “A process for function based architecture - Definition and modeling,” Sch. Aerosp. Eng., vol. Master of, no. April, p. 209, 2008.
[58] D. Mavris, C. de Tenorio, and M. Armstrong, Methodology for Aircraft System Architecture Definition. 2008.
[59] “Set-Based Design – Scaled Agile Framework.” [Online]. Available: https://www.scaledagileframework.com/set-based-design/. [Accessed: 05-Mar-2019].
[60] R. Bornholdt, T. Kreitz, and F. Thielecke, “Function-Driven Design and Evaluation of Innovative Flight Controls and Power System Architectures.” SAE International , 2015.
[61] SAE International, “ARP4761:Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment.,” 1996.
[62] G. Esdras and S. Liscouet-Hanke, “Development of Core Functions for Aircraft Conceptual Design: Methodology and Results,” in Canadian Aeronautics and Space Institute AERO 2015 Conference, 2015.
[63] A. Canedo and J. H. Richter, “Architectural Design Space Exploration of Cyber-physical Systems Using the Functional Modeling Compiler,” Procedia CIRP, vol. 21, pp. 46–51, 2014.
[64] A. Canedo, E. Schwarzenbach, and M. A. A. Faruque, “Context-sensitive synthesis of executable functional models of cyber-physical systems,” in 2013 ACM/IEEE International Conference on Cyber-Physical Systems (ICCPS), 2013, pp. 99–108.
[65] K. Michaels, “Key Trends In Commercial Aerospace Supply Chains,” Montreal, 2017.
[66] “Model Based Systems Engineering | Siemens.” [Online]. Available: https://www.plm.automation.siemens.com/global/en/our-story/glossary/model-based-systems-engineering/28573. [Accessed: 27-Mar-2019].
[67] N. A. Tepper, “Exploring the use of Model-Based Systems Engineering (MBSE) to develop Systems Architectures in Naval Ship Design,” Massachusetts Institute of Technology, 2010.
[68] J. A. Estefan, “Survey of Model-Based Systems Engineering (MBSE) Methodologies,” 2008.
[69] A. Maheshwari, “Industrial Adoption of Model-Based Systems Engineering: Challenges and Strategies,” 2015.
[70] B. A. Morris, D. Harvey, K. P. Robinson, and S. C. Cook, “Issues in Conceptual Design and MBSE Successes: Insights from the Model-Based Conceptual Design Surveys,” INCOSE Int. Symp., vol. 26, no. 1, pp. 269–282, Jul. 2016.
[71] National Aeronautics and Space Administration, “Constellation Program Lessons Learned Volume II Detailed Lessons Learned,” 2011.
[72] D. Nichols and C. Lin, “Integrated Model-Centric Engineering: The Application of MBSE at JPL Through the Life Cycle,” 2014.
[73] T. J. Bayer et al., Model Based Systems Engineering on the Europa Mission Concept Study. .
[74] C. Becker and T. Giese, “Application of Model Based Functional Specification Methods to Environmental Control Systems Engineering,” SAE Int. J. Aerosp., vol. 4, no. 2, pp. 637–651, 2011.
[75] P. George Mathew, S. Liscouet-Hanke, and Y. Le Masson, “Model-Based Systems Engineering Methodology for Implementing Networked Aircraft Control System on Integrated Modular Avionics – Environmental Control System Case Study,” SAE Tech. Pap., Oct. 2018.
[76] H. Luiz Valdivia de Matos, “Model-Based Specification of Integrated Modular Avionics Systems using Object-Process Methodology,” in 2018 IEEE/AIAA 37th Digital Avionics Systems Conference (DASC), 2018, pp. 1–8.
[77] C. Pessa, M. Cifaldi, E. Brusa, D. Ferretto, K. M. N. Malgieri, and N. Viola, “Integration of different MBSE approaches within the design of a control maintenance system applied to the aircraft fuel system,” in 2016 IEEE International Symposium on Systems Engineering (ISSE), 2016, pp. 1–8.
[78] Z. C. Fisher, K. Daniel Cooksey, and D. Mavris, “A model-based systems engineering approach to design automation of SUAS,” in 2017 IEEE Aerospace Conference, 2017, pp. 1–15.
[79] X. Hai, S. Zhang, and X. Xu, “Civil aircraft landing gear brake system development and evaluation using model based system engineering,” in 2017 36th Chinese Control Conference (CCC), 2017, pp. 10192–10197.
[80] T. Bayer, “Is MBSE helping? Measuring value on Europa Clipper,” in 2018 IEEE Aerospace Conference, 2018, pp. 1–13.
[81] R. Malone, B. Friedland, J. Herrold, and D. Fogarty, “Insights from Large Scale Model Based Systems Engineering at Boeing,” INCOSE Int. Symp., vol. 26, no. 1, pp. 542–555, Jul. 2016.
[82] J. D’Ambrosio and G. Soremekun, “Systems engineering challenges and MBSE opportunities for automotive system design,” in 2017 IEEE International Conference on Systems, Man, and Cybernetics (SMC), 2017, pp. 2075–2080.
[83] “Types of Models - SEBoK.” [Online]. Available: https://www.sebokwiki.org/wiki/Types_of_Models#Model_Classification. [Accessed: 29-Mar-2019].
[84] “DoD Modeling and Simulation (M&S) Glossary.” United States Department of Defense, 1998.
[85] “MBSE WorksTM: MBSE + SysML Overview - What is MBSE?” [Online]. Available: https://mbseworks.com/mbse-overview/. [Accessed: 05-Apr-2019].
[86] “What is Unified Modeling Language (UML)?” [Online]. Available: https://www.visual-paradigm.com/guide/uml-unified-modeling-language/what-is-uml/. [Accessed: 27-Mar-2019].
[87] “SysML FAQ: What are the SysML diagram types?” [Online]. Available: https://sysmlforum.com/sysml-faq/what-are-sysml-diagram-types.html. [Accessed: 05-Apr-2019].
[88] P. Roques, Systems Architecture Modeling with the Arcadia Method: A Practical Guide to Capella, 1st ed. Elsevier, 2017.
[89] J.-L. Voirin, “Motivations, Background and Introduction to Arcadia,” in Model-based System and Architecture Engineering with the Arcadia Method, M. Voirin, Ed. Elsevier, 2018, pp. 3–14.
[90] “Capella MBSE Tool - Arcadia.” [Online]. Available: https://polarsys.org/capella/arcadia.html. [Accessed: 04-Mar-2019].
[91] J.-L. Voirin, “Modelling Languages for Functional Analysis Put to the Test of Real Life,” in Complex Systems Design & Management, 2012.
[92] P. Roques, “Systems architecture modeling with the Arcadia method : a practical guide to Capella.” 2018.
[93] E. Caliò, F. Di Giorgio, and M. Pasquinelli, “Deploying Model-Based Systems Engineering in Thales Alenia Space Italia,” 2016.
[94] J. Navas, P. Tannery, S. Bonnet, and J. Voirin, “Bridging the Gap Between Model-Based Systems Engineering Methodologies and Their Effective Practice: A Case Study on Nuclear Power Plant Systems Engineering,” Insight, vol. 21, no. 1, pp. 17–20, 2018.
[95] S. Liscouët-Hanke and A. Jeyaraj, “A Model-Based Systems Engineering approach for efficient flight control system architecture variants modelling in conceptual design,” Int. Conf. Recent Adv. Aerosp. Actuation Syst. Components, pp. 34–41, 2018.
[96] “File:A32XFAMILYv1.0.png - Wikimedia Commons.” [Online]. Available: https://commons.wikimedia.org/wiki/File:A32XFAMILYv1.0.png. [Accessed: 04-Mar-2019].
[97] Hornung. Mirko, “Flight Control Systems -ACS2017.” pp. 69–121, 2017.
[98] I. Moir and A. Seabridge, Aircraft Systems Mechanical, electrical, and avionics subsystems integration, Second Edi. London: Professional Engineering Publishing Limited, 2001.
[99] Airbus, “Flight Deck and Systems Briefing for Pilots A350-900 Flight Deck and Systems Briefing for Pilots.”
[100] FAA, FAA-H-8083-31A, Aviation Maintenance Technician Handbook-Airframe, Volume 2. .
[101] S. Liscouet-Hanke, A. Tfaily, and G. Esdras, Parametric 3D Modeling for Integration of Aircraft Systems in Conceptual Design. 2015.
[102] J. Fuchte, B. Nagel, and V. Gollnick, “Automatic Fuselage System Layout using Knowledge Based Design Rules,” in Deutscher Luft- und Raumfahrtkongress (DLRK), 2012.
[103] R. Munjulury, I. Escolano Andr´es, A. Diaz Puebla, and P. Krus, “Knowledge-based flight control system and control surfaces integration in RAPID.,” in Aerospace Technology Congress 2016, 2016.
[104] R. Munjulury, I. Staack, A. Sabaté López, and P. Krus, Knowledge-based aircraft fuel system integration, vol. 90. 2018.
[105] N. Kodali Rao, “Influence of Parametric Modelling of Wing Subsystems on the Aircraft Design and Performance,” TU Delft, 2017.
[106] J.-C. Maré, “Aerospace actuators 2 : signal-by-wire and power-by-wire,” vol. 1, no. April 1992, p. 255, 2017.
[107] J. C. Maré, “Aerospace Actuators 1: Needs, Reliability and Hydraulic Power Solutions,” Aerosp. Actuators 1 Needs, Reliab. Hydraul. Power Solut., no. 9, pp. 1–220, 2016.
[108] J. Maré, “Signal-by-Wire Architectures and Communication.”
[109] X. Le Tron, “A380 Flight Controls Overview,” 2007.
[110] AIRBUS, “AIRBUS A320 Flight Crew Operating Manual - Flight Control System.”
[111] MOOG Inc., “Electro-Hydraulic Valves: A Technical Look | Moog.” [Online]. Available: http://www.moogvalves.com/h-and-p/infographic-1585DB-4148ZT.html. [Accessed: 13-Mar-2019].
[112] PolarSys, “Capella User Guide- Replicable Elements.” 2017.
[113] Bombardier Inc., “Bombardier Challenger 300 Flight Crew Operating Manual CSP 100-6 (Flight Controls),” 2004.
[114] AIRBUS, “AIRBUS A320 Flight Crew Operating Manual - Hydraulic System.”
[115] Dassault Aviation, “Dassault Falcon 7X ATA 27-FLIGHT CONTROLS.”
[116] Dassault Aviation, “Falcon 7X : ATA 29 – Hydraulic System General.”
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