Jon Berndt

1

• Jon Berndt
• jon_at_jsbsim.org
• JSBSim Project Development Coordinator
• AIAA Houston Annual Technical Symposium
• May 11, 2007

2
JSBSim The Basics

• JSBSim has been under development for 10 years.
• It runs on Windows, Mac, Linux, IRIX, etc.
• All source code is available.
• Open Source tools are all that is needed to build
  and use it.
• It is scriptable.
• It can be run from a stub application (in
  standalone mode) or integrated within a larger
  application framework such as OpenEaagles, or a
  simulation such as FlightGear.

3
JSBSim Project Philosophy

• Simulating flight requires extensive technical
  knowledge.
• JSBSim aims to find a balance between fidelity
  and simplicity, so the task of simulating the
  flight of any aerospace vehicle can be done with
  the minimum specific input possible.
• The target audience is upper level engineering
  students.
• JSBSim also provides advanced capabilities for
  those who need it.

4
Easy to use for application developers
(as a standalone simulation application)

• include ltFGFDMExec.hgt
• int main(int argc, char argv)
• JSBSimFGFDMExec FDMExec
• bool result true
• FDMExec.LoadScript(argv1)
• while (result) result FDMExec.Run()

5
Easy to use for application developers
(called from a simulation application)

• int initialize_flight_dynamics(char name)
• FDMExec new FGFDMExec()
• FDMExec-gtLoadAircraft(name)
• FDMExec-gtDoTrim(mode)
• int run_flight_dynamics()
• copy_inputs_to_jsbsim()
• FDMExec-gtRun()
• copy_outputs_from_jsbsim()

6
JSBSim Program Flow
External program
Trim
End
Load
Start
Run
Aircraft Engine definition files
JSBSim Executive
7
Flight Control Block Diagram Example
8
Flight Control Components in JSBSim
ltsensor name"fcs/attitude/sensor/phi-rad"gt
ltinputgt attitude/phi-rad lt/inputgt ltlaggt 0.5
lt/laggt ltnoise variation"PERCENT"gt 0.05
lt/noisegt ltquantization name"attitude/sensor/qu
antized/phi-rad"gt ltbitsgt 12 lt/bitsgt
ltmingt -3.14 lt/mingt lt!-- -180 degrees --gt
ltmaxgt 3.14 lt/maxgt lt!-- 180 degrees --gt
lt/quantizationgt ltbiasgt 0.001 lt/biasgt
lt/sensorgt ltpid name"fcs/roll-ap-error-pid"gt
ltinputgtfcs/attitude/sensor/phi-radlt/inputgt
ltkpgt 2.0 lt/kpgt ltkigt 0.2lt/kigt ltkdgt 1 lt/kdgt
lt/pidgt
9
Flight Control Components in JSBSim
ltsensor name"fcs/attitude/sensor/phi-rad"gt
ltinputgt attitude/phi-rad lt/inputgt ltlaggt 0.5
lt/laggt ltnoise variation"PERCENT"gt 0.05
lt/noisegt ltquantization name"attitude/sensor/qu
antized/phi-rad"gt ltbitsgt 12 lt/bitsgt
ltmingt -3.14 lt/mingt lt!-- -180 degrees --gt
ltmaxgt 3.14 lt/maxgt lt!-- 180 degrees --gt
lt/quantizationgt ltbiasgt 0.001 lt/biasgt
lt/sensorgt ltpid name"fcs/roll-ap-error-pid"gt
ltinputgt fcs/attitude/sensor/phi-rad lt/inputgt
ltkpgt 2.0 lt/kpgt ltkigt 0.2lt/kigt ltkdgt 1 lt/kdgt
lt/pidgt
10
Complex Functions

• ltfcs_function name"Heading to Waypoint Rad"gt
• ltfunctiongt
• ltatan2gt lt!-- atan2 (deltaY, deltaX )--gt
• ltproductgt
• ltsingtltpropertygt fcs/delta-lon-rad
  lt/propertygtlt/singt
• ltcosgtltpropertygt ap/wp_latitude_rad
  lt/propertygtlt/cosgt
• lt/productgt
• ltdifferencegt
• ltproductgt
• ltcosgtltpropertygt position/lat-gc-rad
  lt/propertygtlt/cosgt
• ltsingtltpropertygt ap/wp_latitude_rad
  lt/propertygtlt/singt
• lt/productgt
• ltproductgt
• ltsingtltpropertygt position/lat-gc-rad
  lt/propertygtlt/singt
• ltcosgtltpropertygt ap/wp_latitude_rad
  lt/propertygtlt/cosgt
• ltcosgtltpropertygt fcs/delta-lon-rad
  lt/propertygtlt/cosgt
• lt/productgt
• lt/differencegt
• lt/atan2gt

11
Aerodynamic Forces and Moments

• Aerodynamic forces and moments are each defined
  and built up for the three axes, from any number
  of individual contributions. A force or moment
  component for an axis can be defined as a
  function of any property value, lookup table
  value, or constant value.
• An example showing how the pitching moment due to
  flap deflection is defined is presented in the
  next slide.

12
XML Aerodynamic Term Definition

• ltfunction name"aero/moment/Df"gt
• ltdescriptiongtPitching moment due to flap
  deflectionlt/descriptiongt
• ltproductgt
• ltpropertygt aero/qbar-area lt/propertygt
• ltpropertygt metrics/cbarw-ft lt/propertygt
• lttablegt
• ltindependentVargt fcs/flap-pos-deg
  lt/independentVargt
• lttableDatagt
• 0.0 0.0
• 10.0 -0.0654
• 20.0 -0.0981
• 30.0 -0.1140
• lt/tableDatagt
• lt/tablegt
• lt/productgt
• lt/functiongt
• Represents M?f qbar Sw cbar Cm?f

13
XML Aerodynamic Term Definition

• ltfunction name"aero/moment/Df"gt
• ltdescriptiongtPitching moment due to flap
  deflectionlt/descriptiongt
• ltproductgt
• ltpropertygt aero/qbar-area lt/propertygt
• ltpropertygt metrics/cbarw-ft lt/propertygt
• lttablegt
• ltindependentVargt fcs/flap-pos-deg
  lt/independentVargt
• lttableDatagt
• 0.0 0.0
• 10.0 -0.0654
• 20.0 -0.0981
• 30.0 -0.1140
• lt/tableDatagt
• lt/tablegt
• lt/productgt
• lt/functiongt
• Represents M?f qbar Sw cbar Cm?f

14
XML Aerodynamic Term Definition

• ltfunction name"aero/moment/Df"gt
• ltdescriptiongtPitching moment due to flap
  deflectionlt/descriptiongt
• ltproductgt
• ltpropertygt aero/qbar-area lt/propertygt
• ltpropertygt metrics/cbarw-ft lt/propertygt
• lttablegt
• ltindependentVargt fcs/flap-pos-deg
  lt/independentVargt
• lttableDatagt
• 0.0 0.0
• 10.0 -0.0654
• 20.0 -0.0981
• 30.0 -0.1140
• lt/tableDatagt
• lt/tablegt
• lt/productgt
• lt/functiongt
• Represents M?f qbar Sw cbar Cm?f

15
XML Aerodynamic Term Definition

• ltfunction name"aero/moment/Df"gt
• ltdescriptiongtPitching moment due to flap
  deflectionlt/descriptiongt
• ltproductgt
• ltpropertygt aero/qbar-area lt/propertygt
• ltpropertygt metrics/cbarw-ft lt/propertygt
• lttablegt
• ltindependentVargt fcs/flap-pos-deg
  lt/independentVargt
• lttableDatagt
• 0.0 0.0
• 10.0 -0.0654
• 20.0 -0.0981
• 30.0 -0.1140
• lt/tableDatagt
• lt/tablegt
• lt/productgt
• lt/functiongt
• Represents M?f qbar Sw cbar Cm?f

16
XML Aerodynamic Term Definition

• ltfunction name"aero/moment/Df"gt
• ltdescriptiongtPitching moment due to flap
  deflectionlt/descriptiongt
• ltproductgt
• ltpropertygt aero/qbar-area lt/propertygt
• ltpropertygt metrics/cbarw-ft lt/propertygt
• lttablegt
• ltindependentVargt fcs/flap-pos-deg
  lt/independentVargt
• lttableDatagt
• 0.0 0.0
• 10.0 -0.0654
• 20.0 -0.0981
• 30.0 -0.1140
• lt/tableDatagt
• lt/tablegt
• lt/productgt
• lt/functiongt
• Represents M?f qbar Sw cbar Cm?f

17
XML Aerodynamic Term Definition

• ltfunction name"aero/moment/Df"gt
• ltdescriptiongtPitching moment due to flap
  deflectionlt/descriptiongt
• ltproductgt
• ltpropertygt aero/qbar-area lt/propertygt
• ltpropertygt metrics/cbarw-ft lt/propertygt
• lttable nameaero/coefficient/Cmdfgt
• ltindependentVargt fcs/flap-pos-deg
  lt/independentVargt
• lttableDatagt
• 0.0 0.0
• 10.0 -0.0654
• 20.0 -0.0981
• 30.0 -0.1140
• lt/tableDatagt
• lt/tablegt
• lt/productgt
• lt/functiongt
• Represents M?f qbar Sw cbar Cm?f

18
Output

• JSBSim has a versatile data logging system.
• Any number of output sections can be specified
  in the configuration file.
• Logical data sets can be output, and/or
  individual parameters.
• Output can be sent to one or many (in any
  combination)
• Socket (local or remote)
• File
• Console

19
Developing a Specific Flight Model

• The JSBSim code is generic, allowing anything
  from a ball, to an aircraft, to a rocket, to be
  modeled. The task of modeling the dynamics of a
  specific flight vehicle then becomes mostly one
  of acquiring the needed data.

20
Sources of Modeling Data (data farming)

• FAA Type Certificate Data Sheets (TCDS)
• Weight and balance
• Propulsion data
• Limitations
• Aerosurface deflections
• Fuel capacity
• Etc.

• NASA Technical Reports
• Aerodynamics
• Test response
• Mass properties (MoI)
• Aircraft geometry

21
Sources of Modeling Data (contd.)

• POH (Pilot Operating Handbook)
• Textbooks
• Manufacturers information (web site)
• Pilot inputs. Maybe.

22
XML Technologies Used

• Aircraft, engine, thruster, scripts, and
  initial conditions are all specified in an
  XML-based format collectively known as JSBSim-ML.
• An XML schema is provided to validate an XML file
• An XML stylesheet language transform is provided
  for displaying XML files in a prettier format.
• Expat, an established, open source XML parsing
  library, is used in JSBSim, offloading that
  development task.

23
XML-based Standard

• The AERO-ML (aka DAVE-ML) standard is being
  prepared for submission to the AIAA standards
  committee. JSBSim provided a (surprise) early
  example of an implementation for the concept of
  describing an aircraft flight model in XML. The
  AERO-ML effort is being spearheaded by Bruce
  Hildreth (AIAA Standards Committee) and Bruce
  Jackson (LaRCsim author).
• The most recent version of JSBSim-ML has in
  return been influenced by AERO-ML.

24
XSL Stylesheet Formatting
25
JSBSim Example Uses

• JSBSim has been incorporated into at least two
  large scale battlefield simulators in order to
  provide flight simulation capabilities
  (OpenEaagles, and another as written about in a
  Swedish thesis work).
• LMCO, Missiles and Fire Control, used JSBSim in
  one case to model a Predator in an integrated
  air/ground simulator (as far as I can tell).
• University of Naples used JSBSim to make batch
  runs in a study to determine the clearance
  between a radio tower near a runway and the
  flight path of a 737 under a variety of nominal
  and off-nominal conditions.
• A European company used JSBSim for a downrange
  impact study for a workhorse launch vehicle, in a
  scenario where the first stage failed.

26
JSBSim Example Uses (2)

• A group of EC companies used JSBSim as one of
  several components assembled to study landing and
  taxiing traffic at European airports with an eye
  towards improving flow and safety.
• A slightly modified version of JSBSim was used to
  develop a guidance and control scheme for a
  finless rocket, using an evolving neural network
  neuroevolution.
• Interorbital Systems, used a modified JSBSim to
  develop control laws for one of their sounding
  rockets

27
Flight Simulation in Education

• JSBSim aims to be a useful tool in the academic
  world. Industry needs and teaching approaches
  have evolved over the years
• industry, government, and academia the
  likely employers of aerospace graduates desire
  a workforce which is the more holistic and
  systems-thinking as opposed to the highly
  specialized, research-oriented engineer of past
  generations.
• AIAA/MIT paper Re-engineering Aerodynamics
  Education

28
Flight Simulation in Education

• Aerospace vehicle design encompasses many
  disciplines, which are fused together by system
  engineering.
• By mathematically modeling the components
  aerodynamics, propulsion, guidance and control,
  etc. they will grasp the theoretical
  underpinning of key engineering disciplines and
  their interactions.
• Peter Zipfel, Adjunct Associate Professor,
  University of Floridaauthor of Building
  Aerospace Simulations in C

29
Flight Simulation in Education

• in the modeling and simulation courses, where
  the emphasis is on the total system, I insist
  that they use a compiled language. Why not
  MATLAB? MATLAB/SIMULINK is great for control
  system design, but hides the mathematics
  underneath block diagrams and icons. For complete
  vehicle simulations it is important that the
  student experiences the mathematical modeling
  process first hand.
• Peter Zipfel, Adjunct Associate Professor,
  University of Floridaauthor of Building
  Aerospace Simulations in C

30
JSBSim in Education

• JSBSim has proven to be very helpful in an
  academic setting. The most commonly seen use is
  the modeling and simulation of UAV flight and
  exercising guidance and control laws.
• The favor has also been returned in contributed
  code and even in the beginning of another open
  source project, JSBSim Commander.

31
Additional Tools, JSBSim Commander
32
Additional Tools DATCOM

• Digital DATCOM is a freely available tool that
  attempts to determine aerodynamic coefficients
  and stability derivatives for an aircraft as
  defined in a text input file.
• A contributor to the JSBSim project has modified
  DATCOM to provide its data output directly in
  JSBSim format. (see www.holycows.net/datcom)

33
Additional Tools AVL

• AVL is a program written by Mark Drela (MIT) that
  uses the vortex lattice method to determine
  aerodynamic qualities of a defined vehicle. A
  student has offered to modify the open source AVL
  code so it can output directly in JSBSim format.

34
Additional Tools Stripchart

• A stripchart application has been written that
  accepts data from JSBSim via a socket interface.

35
Future Goals

• Documentation
• More examples
• Release version 1.0
• Multi-body capability (specifically, multi-stage
  capability)

36

• Additional Material

37
Referencing Papers

• Robust Non-Linear Control through Neuroevolution,
  Faustino John Gomez, B.A., PhD Dissertation,
  University of Texas, Austin, August 2003
• Active Guidance for a Finless Rocket Using
  Neuroevolution, Faustino John Gomez, University
  of Texas, Austin, 2003
• Simulated Flight Testing of an Autonomous
  Unmanned Aerial Vehicle Using FlightGear, Eric F.
  Sorton and Sonny Hammaker, Institute for
  Scientific Research, Inc.
• Automating the Cockpit, Marten Tamerius,
  University of Technology, Delft, The Netherlands,
  2003

38
Referencing Papers

• Extending a Battlefield Simulator with Large
  Scale Terrain Rendering and Flight Simulator
  Functionality, Daniel Johansson, Department of
  Science and Technology, Linköpings Universitet,
  Norrköping, Sweden, November 2005
• Development of a Low-Cost Simulator for
  Demonstration and Engineer Training, Burns, R.
  S.  Duquette, Matthew M.  Howerton, Joseph B. 
  Simko, Richard J., AIR FORCE RESEARCH LAB
  WRIGHT-PATTERSON AFB OH AIR VEHICLES DIRECTORATE,
  July 2003