Comprehensive Identi铿乧ation from FrEquency Responses (CIFER庐)
Figure: Comprehensive Identi铿乧ation from FrEquency Responses
System identi铿乧ation is a procedure by which a mathematical description of vehicle
or component dynamic behavior is extracted from test data. System identi铿乧ation can
be thought of as an inverse of simulation. Simulation requires the adoption of (a-priori)
engineering assumptions to allow the formulation of model equations. These simulation
models are then used to predict aircraft or subsystem motion. In contrast, system
identi铿乧ation begins with measured aircraft motion and "inverts" the responses to
rapidly extract a model which accurately re铿俥cts the measured aircraft motion, without
making a-priori assumptions or requiring a time-consuming modeling effort. Applications
of system identi铿乧ation results include:
(1) comparison of wind tunnel and 铿俰ght characteristics; (2) validation and update
of simulation models; (3) handling-qualities analyses and speci铿乧ation compliance;
(4) optimization of automatic 铿俰ght control systems; and (5) vibration and aeroelastic
analyses.
The U.S. Army Combat Capabilities Development Command (DEVCOM) Aviation & Missile Center (AvMC) and San Jos茅 State University Research Foundation (91传媒厂RF) jointly distribute an integrated facility for system identi铿乧ation based on a comprehensive frequency-response approach that is uniquely suited to the dif铿乧ult problems associated with 铿俰ght-test data analysis. The foundation of the CIFER庐 approach is the high-quality extraction of a complete multi-input/multi-output (MIMO) set of non-parametric input-to-output frequency responses. These responses fully characterize the coupled characteristics of the system without a-priori assumptions. Advanced Chirp-Z transform and composite optimal window techniques developed and exercised with over 10 years of 铿俰ght project applications provide signi铿乧ant improvement in frequency-response quality relative to standard Fast Fourier Transforms (FFTs). Sophisticated nonlinear search algorithms are used to extract a state-space model which matches the complete input/output frequency-response data set.
Key Features of the CIFER庐 Approach Are:
- Identi铿乧ation algorithms highly-exercised and tuned based on many
铿俰ght projects - Highly-铿俥xible and interactive de铿乶ition of identi铿乧ation model structures
- Fully automated weighting function selection based on frequency-response accuracy
- Reliable parameter accuracy metrics
- Integrated procedure for identi铿乧ation and model structure determination
- Time-domain veri铿乧ation of models, including identi铿乧ation of offsets
and biases
Application Modules within CIFER庐 Allow:
- Rapid identi铿乧ation of transfer-function models
- Spectral signal analysis
- Handling-qualities and classical servoloop analysis
- Time- and frequency-domain comparisons of identi铿乧ation versus simulation model prediction
Additional Information
SALES & OTHER INQUIRIES CONTACT
San Jos茅 State University Research Foundation
flight-control-sta@sjsu.edu
