More Than Dynamic Modelling


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AN understanding as to how the J2 UNiversal Tool-Kit can be used for the complete development of aircraft and provides more capability than just dynamic modelling

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More Than Dynamic Modelling

  1. 1. The J2 Universal Tool-Kit - More than Dynamic Modelling AIRCRAFT MODELLING AND PERFORMANCE PREDICTION SOFTWARE Key Aspects INDUSTRIES MOST COMMON POINTS We Already Have the Capability We Don’t Do that Analysis Yet I use Matlab/Simulink MOVING TO THE NEXT STAGE Beyond Flight Modelling FLIGHT TESTING Performing flight trials from conceptual design WHY NOT FLY? What do pilots think of the latest design? CONCLUSION More than Dynamic Modelling
  2. 2. Jane’s “All the World’s Aircraft” has documented over 950 aircraft projects from over 550 manufacturers across the globe. In performing it’s market research to develop requirements and understand the industry perspective on software design tools, J2 Aircraft Dynamics have spoken, directly and indirectly, to over 200 of these manufacturers. In addition to our research, we have over 15 years experience in aircraft design and control including handling qualities evaluation and envelope expansion of the Eurofighter Typhoon Aircraft, design and control system development of Reconnaissance, Radar Jamming and Flying Target UAVs, Thrust Vectoring and conventional aircraft. Each aircraft class offers their own unique requirements on handling qualities, stability and control, and manoeuvring. We have analysed Business Jets and a variety of unconventional aircraft and missile systems. This extensive research and experience base underpins the overall capabilities of the J2 Universal Tool-Kit. We have not yet come across any other solution that comes close to achieving the benefits offered by the J2 solution. From our conversations and research and our discussions with Manufacturers, Consultants, Government Agencies, and Universities worldwide on the J2 Universal Tool-Kit, the 3 most common points that are made are: “We already have the ability to model and simulate our aircraft” “We don’t use simulation of our aircraft at the early stages of the design” “We already have Matlab” With this in mind, the purpose of this document is to help to understand the current situation, and to outline/define how the J2 Universal Tool-Kit can be used to return significant value/provide significant savings in time, costs and improved productivity. Take the time to know where you can accelerate your knowledge and understanding and know where you can significantly reduce your costs of design
  3. 3. INDUSTRIES MOST COMMON POINTS We Already Have the Capability All serious/major manufacturers have some form of simulation capability. This is often legacy code that has been written by engineers for some project past that has been updated and modified over time to fit each new project. In very large organisations, a separate software group may have been commissioned to write a more general solution. However, in all cases this solution utilises comprehensive data for defining the aircraft coefficient information, as well as mass and inertia details. In the worst case scenario the aircraft data is actually embedded in the code itself (hard coded and typically written in FORTRAN) and any changes to the aircraft design require a modification to the code and corresponding re-compilation. In better situations, the aircraft data is stored in text files that are loaded into the software at run-time. In all cases the amount of data and structure of the code means that engineers are reluctant to use simulation early in the design cycle when the design is in a state of flux as they would have to generate masses of information and produce numerous copies of code to be able to analyse the design changes, and model the impact of modification and sensitivity studies. This is viewed as too big a task. If the J2 Universal Tool-Kit is used as an inherent part of the early design process data can be detailed or simple; it can come from any data source at any point in the lifecycle. The models are built up from a logical hierarchy which maps onto the aircraft structure providing an easy to use and understandable aircraft model. The use of J2 Universal also unlocks significant savings on design hours and a considerable increase in fidelity of the flight model and assessment of design changes, even at the early stages with no additional hours wasted on re-writing and compiling code. Comparing the J2 Universal Tool-Kit Approach to one of the Existing Approaches to Dynamic Modelling Logical Structure to Aircraft Model Definition Multiple pages of aircraft specific code to define the aircraft model data
  4. 4. The speed with which engineers can construct aircraft models and variations can come down from weeks/months to hours/days. This results in them being able to construct more models and evaluate more cases in a significantly Integration of User Defined Libraries to the Aircraft reduced time. The ability to build the Model aircraft from any data source means that models can be “flown” much earlier in the design lifecycle increasing fidelity and confidence which in turn can unlock significant value and benefit. In some cases though, internal development has introduced a smooth process for generating data and turning it into software code. In this situation, such comprehensive data models can be included in the J2 Universal Tool-Kit through open interfaces that provide a simple drag ‘n’ drop approach to including manufacturers data libraries. This then unlocks the benefits summarised above. Mapping Model Parameters to Library Inputs
  5. 5. This same data model has many uses and can be used for many analyses not just flight simulation and dynamic modelling. Static stability can be assessed, as well as classical linear characteristics about any flight condition such as eigenvalue, poles and zeros and root locus analysis. Eigenvalues across Airspeed Showing Modes of Motion Root Locus At the same time the modes of motion are automatically calculated to assess any type of classical figure of merit Evaluating Short Period Characteristics against ESDU 92006
  6. 6. We Don’t Do that Analysis Yet As mentioned in the introduction, many companies do not perform their dynamic modelling analysis until much later in the design cycle. Whilst this has become an accepted process it does not mean it is the best way to proceed. When performing any analysis on an aircraft for the first time, it will always uncover aspects that were not known or not previously predicted. These aspects will, in turn, result in potential design changes even after CDR which can lead to unwanted and often significant cash burn and budget overrun. This outcome is due to the complex nature of aircraft and all the contributing factors and is especially true when investigating handling qualities, and stability and control. There are so many factors to consider (aerodynamics, weights, structures, propulsion) that simple approximations cannot identify all the characteristics. It is therefore always necessary to perform dynamic response modelling to fully understand the situation. With the J2 Universal Tool-Kit it is possible to perform dynamic modelling at the very beginning of the aircraft design lifecycle, greatly reducing the risk of surprises and unwanted cash burn on fixes. Cost of Changes Number of Changes Changes using J2 Traditional Changes Cost of Change Mission Preliminary Flight Detail Design Manufacture Delivery Specification Design Trials Development Process Comparison of the Changes made and the Cost of Each Change due to Traditional Design Process and Using the J2 Universal Tool-Kit If we now look at how aircraft are developed, it can be seen that the cost of modifying the airframe goes up exponentially throughout the process. A traditional approach to stability and control, handling qualities, and behavioural analysis can incur major changes very late on in the project design cycle due to the late approach to dynamic modelling. By bringing this analysis forwards in the design cycle, a much greater understanding of the aircraft can be developed and although more changes may be required in the early stages this is where changes can be accommodated easily and cheaply, so having a reduced impact on the design. The resultant savings can be seen below.
  7. 7. J2 Approach Traditional Approach Cost of Changes Advantage Mission Preliminary Flight Detail Design Manufacture Delivery Specification Design Trials Development Process Total Cost of Changes when comparing the Traditional Approach and the J2 Universal Tool-Kit Experience shows that 80% of the project costs are defined during the first 20% of the project. The J2 Universal Tool-kit provides the opportunity to know as much about the aircraft as early as possible to avoid expensive late fixes and significant cash burn. I use Matlab/Simulink In this situation, it is felt that companies have moved forwards from the more traditional in-house developed FORTRAN solutions. The truth is, in many situations companies have just changed their language from a structured high order language, such as FORTRAN to Matlabs scripting language. Matlab/Simulink is an excellent tool for developing control systems and matrix manipulation. However, the user requires significant domain knowledge to develop a solution. In the case of dynamic modelling, users have to trim 1 case at a time and then run the responses 1 case at a time, they have to then run the response manoeuvre from the created initial conditions and then develop read/write routines to store and retrieve the data. Creating plots requires further scripting activities all of which takes time away from the designers’ available hours. Matlab/Simulink is very widely used in the aerospace industry, so the J2 engineers naturally decided to take a look at how to improve the process by working with Matlab/Simulink. The key was to integrate the best of Matlab/Simulink with the best of the J2 Universal Tool-Kit. This was done by
  8. 8. creating a series of Simulink components that enable the two tools to merge seamlessly, enabling users to quickly build logical ordered easy to understand data models in the J2 Universal Tool-Kit and merge these using Flight Control Systems developed within Matlab/Simulink. Seamless Integration of J2 Universal Tool-Kit into Matlab/Simulink Models These models can then be analysed using the J2 Universal Tool-Kit providing multiple case batch run capability, automatic data storage and retrieval and visualisation.
  9. 9. Visualizing Closed Loop Matlab/Simulink Models The visualisation enables the user to view and compare multiple parameters in real time to fully understand the aircraft’s behaviour and the impact of design decisions. Comparison between different aircraft, configurations or with/without an FCS can all be viewed either in graphs and traces or in real-time at the click of a button. Merging this capability with Matlabs control system design really gives you, the user, the best of both worlds.
  10. 10. MOVING TO THE NEXT STAGE Beyond Flight Modelling The above arguments are primarily focused on companies performing small changes from their existing analysis capability to use the J2 Universal Tool-Kit in the same way. Effectively trying to persuade them to go from 1 seat of their existing solution to 1 seat of the J2 Universal Tool-Kit. However, the J2 Universal Tool-Kit is much more than a simple like for like swap of their existing process of flight dynamic modelling for an easier, faster and better solution. The J2 Universal Tool-Kit enables companies to utilise an integrated collaborative platform for their design and analysis process and to change their fundamental approach to aircraft design, enabling the flight test and certification program to be investigated from the very beginning. This will produce growing confidence and increased fidelity throughout the design and analysis cycle and will result in the aircraft get certified sooner and know that they have developed the best solution possible to meet the mission requirements. In a traditional process, aerodynamics are developing the airframe, passing that information to structures and weights groups who are calculating their information. At the same time the design is changing. Once everyone is happy with the data they eventually send it to Flight Mechanics for analysis. FM investigates behaviour and then sends the data models to be evaluated by FCS. The design is then updated based upon the findings and the whole process repeated. Aerodynamic Design Structural Design Weights Analysis Flight Mechanics FCS Design Classical Waterfall Approach to Design This process can lead to frantic activity when new data is delivered and periods of frustrating inactivity when the analysis is complete and the next set of data is being generated. Inherent in this approach is the ability to introduce errors through data transfer techniques, as well as introducing further errors through attempts to streamline the process by starting work on incomplete data. With the J2 Universal Tool-Kit these issues are totally eliminated due to the centralised database and the way in which each discipline can interact directly with the J2 solution. Throughout the design lifecycle of the aircraft each discipline can continually add information and analyse the most current design. The central database provides version control and configuration
  11. 11. management so even when analysis is started on an intermediate solution, as the solution evolves and takes shape, so the analysis can be simply re-run with the most up to date solution automatically. This dramatically tightens up quality control of the iterative loops of the design cycle to the point of complete interdisciplinary concurrent design. Aerodynamic Design Structural Design Weights Analysis Flight Mechanics FCS Design Reducing Timescales with a Data Centric Environment The key benefits of these improvements are that other disciplines can utilise the data and results developed from analysis performed by other engineers with the same model without the need to perform their own trim and response analyses. For example Structural Engineers can extract the loads information from the flight test cases already run by Flight Mechanics. Aerodynamics can develop tolerance models for sensitivity studies and FCS can re-use their analyses to assess the robustness of the controller. Weights group can change CG locations of the whole aircraft or individual components, and Flight Mechanics can compare the different scenarios and how it affects stability and handling qualities.
  12. 12. CL CLo CL Tolerances to the Lift Curve Slope Applied to the Baseline Aircraft and Documented
  13. 13. FLIGHT TESTING Performing flight trials from conceptual design “Imagine the possibilities if you could take any aircraft concept and immediately understand how it will behave, and be able to perform all flight trials and certification flights instantly”. This is not a dream. Using the J2 Universal Tool-Kit unlocks this potential and is exactly what you can do. When presented with a Mission Specification and Requirements for an aircraft, one of the first stages suggested is to understand how the aircraft is to be tested and certified/validated. How are flight test going to perform their process? These validation manoeuvres can be built into the J2 Universal Tool-Kit right at the beginning of the design stages and the aircraft can be “flown” through the complete flight test program at any stage in its development cycle. What is even more beneficial is the ability to rapidly create variations of the original aircraft model enabling the complete flight envelope to be “flown” over numerous aircraft and all the results then compared. The benefit is that the impact of configuration changes, aerodynamic tolerances, and sensitivity studies can all be performed by only creating the data once. These comparisons can be represented graphically or through real-time visualisation to really understand what is happening to the aircraft. Comparing the Impact of Design Changes on FAR 23 Aircraft Roll Characteristics
  14. 14. From conceptual design, as the aircraft evolves, it is possible to simply re-run the analyses automatically using the latest design and latest version of the data without having to re-create the test cases. By the time the design has reached CDR the configuration is settled and engineers already have great confidence that the aircraft will satisfy design goals and receive certification. However, even at the final stages of the design, through to the actual flight trials, the J2 Universal Tool-Kit provides continual support to the engineers. Data from the flight test data recorder can be loaded into the J2 solution to enable an observer to follow the aircraft and view the flight from the comfort of their own desk using the unique 360 degree visualisation plug-in. This data can then be used to perform re-prediction analysis of the flight model using original pilot inputs to evaluate and assess the model against the real aircraft. This can be further used to refine and validate the model.
  15. 15. Visualizing Flight Test Data and Comparing Predicted Flight to Flight Tests.
  16. 16. WHY NOT FLY? What do pilots think of the latest design? To obtain pilot opinions of aircraft in early stages of design classically requires the development of real time code, look-up tables and interpolation routines and any number of steps just so that it can be connected into a simulator. The effort involved often negates the benefits as the aircraft’s design has moved on by the time the solution is developed. But Pilot opinion is important, this is why the Copper- Harper Rating, and Pilot Opinion Contours have been developed and are used in evaluating aircraft. This is not the case with the J2 Universal Tool-Kit. In this case the real-time capability is already integrated; the dynamic model has already been developed, so in order to run pilot-in- Desktop Simulation with the J2 Universal Tool-Kit the loop simulation of any aircraft within the database requires a few simple mouse clicks. In this respect, pilots can give instant reaction and feedback to different designs and different options. This feature can be used as a simple desktop simulator for basic handling evaluation, or can be integrated across the network directly into a full mission simulator using standard CIGI graphics interface and cockpit inputs/controls. All this can be achieved without the need to write any aircraft specific code, so pilots can fly the aircraft instantly. Automatic Integration of the J2 Universal Tool-Kit into a G-Cueing Full Motion Simulator
  17. 17. CONCLUSION More than Dynamic Modelling All the functionality described above is not the result of utilising different tools to manually develop responses or trims. There are no complex text files that need to be mastered before anything can be achieved or software and scripts to be written to start the first analysis. The full capability is available from a single integrated toolset that utilises easy to use graphical interfaces and built-in domain knowledge to produce rapid prototyping and developing of aircraft through comprehensive stability and control, handling qualities and behavioural analysis. The J2 Universal Tool-Kit focuses on engineers being able to arrive at results and produce data faster and more efficiently, so they can spend more time designing the aircraft and less time designing the tools. From concept to completion, it is possible to build and fly the complete flight test program; integrating data across disciplines automatically without the need to transfer files and the J2 Universal Tool-Kit improving design cycle QC and maintaining consistency through a data centric approach. All engineers can have access to results for further post processing. Where existing tools and processes exist, the best of these can be integrated into the complete J2 Universal tool-kit to ensure continual workflow and no reduction in productivity due to changeover. As has been demonstrated above, all this capability does not just sit with a single flight dynamics or simulation engineer, but is utilised throughout the company bringing all departments together for an improved design process. The functionality and the way the data is managed, demonstrates that the J2 Universal Tool-Kit is much more than a dynamic modelling solution. For this reason alone many companies and research establishments across the world have adopted or are adopting the J2 Universal Tool-Kit into their design process. These include: EADS Embraer Korean Air National Aerospace Laboratories India Cranfield University Arizona State University Allow J2 Aircraft Dynamics to demonstrate how your organisation can realise these benefits and improve on the design lifecycle process.
  18. 18. IT TOOK J2 AIRCRAFT DYNAMICS’ AEROSPACE ENGINEERING AND AIRCRAFT DESIGN SPECIALISTS OVER 10 YEARS TO BUILD THE ‘CODE’ THAT ENABLES THE UNIVERSAL TOOL–KIT TO INVESTIGATE ALL ASPECTS OF AIRCRAFT HANDLING AND PERFORMANCE. WE HAVE DONE ALL THIS SO THAT YOU DON’T HAVE TO. This state-of-the-art, but easy-to-use software PLUG-INS suite gives you unprecedented power to design J2 Builder and ‘fly’ multiple configurations of the complete An easy-to-use graphical interface that flight envelope in a 3-D virtual environment – all rapidly develops aircraft models and at the click of a mouse! When using the J2 builds multiple variants for comparison Universal Tool Kit, you can save hundreds of thousands of dollars by streamlining your J2 Elements process, maximizing your analysis capability and Enables automatic calculation of total aerodynamic coefficients and derivatives reduce the risk of serious project flaws. through integrated strip theory. J2 Developer At the heart of J2’s A Software Development Kit (SDK) for all software is the J2 users to write their own components and Universal Framework, libraries with an interface into J2 Aircraft Models. a cutting-edge configuration control J2 Freedom Provides flight dynamics simulation of and data management aircraft data models, allowing you to platform that hosts all evaluate the complete flight envelope. steps of the design process. Everything J2 Active we offer begins and An open COM interface that instantly interacts with this key integrates your existing design packages with the power of the J2 Universal Tool- framework. kit. J2 Matlab Toolbox Get the full capability of J2 with Simulink Now it’s time to investigate our range of plug- Model files. Manoeuvres from within J2 ins. ‘Mix and match’ their additional design and can be flown on Simulink Models. Run all analysis capabilities using floating licenses. Take analyses from within J2 Universal Tool- control of a bespoke package that perfectly fits Kit. J2 Visualize your requirements. This way, you get Instant understanding and evaluation of the right functionality and maximise the return aircraft behaviour through data visualization and graphic displays. on your investment. J2 Virtual View any results in a virtual 3-D real- ARE YOU READY TO RETHINK THE WAY YOU world, to understand what exactly DEVELOP YOUR AIRCRAFT? happens during unexplained/complex manoeuvres J2 Pilot To find out more about J2 Aircraft Dynamics, Using the J2 Pilot plug-in’s automatic interfaces/models you can fly aircraft on our software and our consultancy services, visit your. You can also use J2 Pilot interfaces to merge the finished design into pilot training simulators.