Development of a System Identification Tool for Subscale Flight Testing

• Main Author: Arustei, Adrian
• Format: Others
• Language: English
• Published: Linköpings universitet, Fluida och mekatroniska system 2019
• Subjects: GFF; Generic Future Fighter; system identification; orthogonal function modeling; equation error method; output error method; aerodynamic derivatives; flight dynamics; flight testing; Aerospace Engineering; Rymd- och flygteknik
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-157292

Aircraft system identification has been widely used to this day in applications like control law design, building simulators or extending flight envelopes. It can also be utilized for determining flight-mechanical characteristics in the preliminary design phase of a flight vehicle. In this thesis, three common time-domain methods were implemented in MATLAB for determining the aerodynamic derivatives of a subscale aircraft. For parameter estimation, the equation-error method is quick, robust and can provide good parameter estimates on its own. The output-error method is computationally intensive but keeps account of the aircraft's evolution in time, being more suitable for fine-tuning predictive models. A new model structure is identified using multivariate orthogonal functions with a predicted squared error stopping criteria. This method is based on linear regression (equation-error). The code written is flexible and can also be used for other aircraft and with other aerodynamic models. Simulations are compared with experimental data from a previous flight test campaign for validation. In the future, this tool may help taking decisions in conceptual design after a prototype is tested.