Evaluation of Flight Dynamics Model Simulation DAVEML
Evaluation of Flight Dynamics Model Simulation DAVEML
Evaluation of Flight Dynamics Model Simulation DAVEML
Bruce Jackson
NASA Langley Research Center Hampton, Virginia
Bruce Hildreth
Science Applications International Corporation Lexington Park, Maryland
Brent W. York
Naval Air Systems Command Patuxent River, Maryland
William B. Cleveland
Northrop Grumman Info. Technology Mountain View, California
2004 AIAA Modeling & Simulation Technology Conference Providence, Rhode Island AIAA 2004-5038
Rapid sim rehosting - minutes instead of months Potential for industry significant cost saving
2002 paper: $ 6+ M per year per aircraft model
Concept
Std. Model Editor Standard Tools Report Editor
Site A (exporter) Export API The Standard (XML-based) Import API Site B (importer)
Import API
Site C (importer)
Concept
Need for standard representation of vehicle dynamics/aerodynamics Get away from ad-hoc, site-specific standards Many are possible; were proposing one Standard is superset of typical sitespecific standards
An exchange standard: no requirement for end use
Previous efforts
MODCOMP - 1980's - attempt to standardize on software & hardware for all training simulations Similar attempts to standardize software modules DIS/HLA/SEDRIS sim environment & network M&S T.C. started data standards effort in early 90s Efforts focused on vehicle dynamics model Objective: to easily exchange a model from one site to another
2. Check case data required to verify proper model transfer 3. Signal definitions (variable names) required to clearly state what the transferred information is (units, axis system, sign convention, etc)
Includes methodology for naming new variables Includes axis system definitions
Proposed AIAA Sim Data Standard Standard Function Table with statistics & provenance
s Mach CL Ref
Independent variables
Provenance ID
}
Statistics
Dependent variable
1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0.0 -0.2 -50. A 0 50 A A B B A A B B
CLALFA(alfa, Mach,delta_s)
C C C A
100
150
+x
An XML approach
eXtensible Markup Language (XML) becoming popular way to encode data for on-line exchange Text-based human/machine readable files Lots of XML utility programs available Specialized set of markup tags developed: Dynamic Aerospace Vehicle Exchange Markup Language (DAVE-ML) First proposed in 2002 (AIAA M&ST Monterey)
DAVE-ML features
Language- and facility-independent Encodes non-linear function tables Encodes build-up equations (via MathML) Encodes history & provenance of model Encodes statistical uncertainty of data Self-documenting (via XSLT) Can include validation data (checkcases)
A Recommended Practice (RP) for implementation has been developed by an informal DAVE-ML steering subcommittee
The RP defines how the information is exchanged
RP Demonstration I (2003-2004)
Two existing aerodynamic models encoded with DAVE-ML as examples Two simulation facilities (Ames and Pax) developed import tools Ames also developed an export tool Successfully demonstrated import and automatic validation of aero models
Demonstration I results
NASA Ames
Historically a FORTRAN-based facility Employ Function Table Processor (FTP) precompiler to create FORTRAN table interpolation subroutines for each table Wrote Perl scripts to import DAVE-ML into FTP source file, FORTRAN code snippets, checkcase routines Wrote Perl scripts to export FTP input files into DAVE-ML files Reduced import time from "several" to single week
Additional progress
Informal DAVE-ML steering committee formed (Bruce Hildreth as chair bruce.hildreth@saic.com) DAVE-ML website created: http://dcb.larc.nasa.gov/utils/fltsim/DAVE Discussion list created: simstds@larc.nasa.gov On-line DAVE-ML reference manual available Java tool to convert DAVE-ML into Simulink
Tested with several internal NASA projects; one was 12.5 MB / 107 KLOC / 97 tables / 717 K pts
Next steps
Invite additional participation / feedback Submit to AIAA; seek ANSI/ISO standard and recommended practice Develop model editor and report generator applications Distribute existing tools developed to test DAVE-ML for use by the modeling community
Conclusions
The initial version of the standard is ready
Substantial savings of time & effort clearly possible Improve efficiency of the simulation community
Exchange with NAVAIR and NASA Ames has demonstrated DAVE-ML is ready for submittal as the Recommended Practice for simulation data exchange
Questions?
Backup slides
Existing standards
Simnet/DIS/HLA-networking/architecture SEDRIS- environmental data representation FAA Advisory Circulars (AC 120-40) Standard atmosphere Standard world (WGS 95?)
dx/dt = Ax + Bu Y = Cx + Du
States and Inputs are key everything in the dynamic simulation depends upon them They should be easily identifiable for good software documentation and maintainability Units for clarity and documentation purposes
Examples
s_bodyXVelocity_fps sd_bodyXAcceleration_fps2 aeroXBodyForceCoefficient thrustYBodyForce_lbf s_ prefix indicates that this variable is a state sd_ prefix indicates that this variable is a state derivative
Variable Names
Names database and definition complete Naming convention taken from STARS Simulation work (Lead by NAWCTSD) Short names taken from NASA Ames
Example Table of Names
Symbol Short Name 8 Character PHI THET PSI PHIR THETR PSIR PHID THED PSID Long Name 33 Character name Same as STARS? Description (including axis system if applicable) Roll Euler Angle, L (local) Frame Pitch Euler Angle, L (local) Frame Yaw Euler Angle, L (local) Frame Roll Angle, L frame Pitch Angle, L frame Yaw Angle, L frame Euler roll rate, L frame Euler pitch rate, L frame Euler yaw rate, L frame Units Sign Convention RWD ANU ANR RWD ANU ANR RWD ANU ANR Initial Value Minimum Value Maximum Value Reference Note Date Last Changed
180 90 180 /2
vs
CLFlaps0 = CLALFA_prad*angleOfAttack_rad + CLDe_pdeg*De_deg+ CLQ*s_bodyPitchRate_radps*chord_f/(2.0*trueAirspeed_fps)
vs
CLFlaps0 = CLALFA_pdeg*angleOfAttack_deg + CLDe_pdeg*De_deg+ CLQ*s_bodyPitchRate_degps*chord_f/(2.0*trueAirspeed_fps)