Matrix pencil method integration into stabilization diagram for poles identification in rotorcraft and powered-lift applications

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Pivetta, P.
Trezzini, A.A.
Favale, M.
Lilliu, C.
Colombo, A.
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The development of a safe and reliable VTOL aircraft is largely dependent on the availability of accurate and practical model of the system. Due to the complex dynamic behavior of rotorcraft and related subsystems, system identification based on flight data is essential in producing representative models. Traditional approaches, such as the polynomial based Prony method, are computationally expensive and sensitive to signal noise and disturbances. They also lack any indication of reliability and typically require time-consuming manual post-verification by a specialist. Given the unique complexity of VTOL aircraft, associated poor signal to noise ratio, and presence of tonal disturbances in flight data, current system identification methods are not robust enough. In this paper, a comprehensive two-step method is presented to address the mentioned limitations of current techniques. The proposed method is an output-only identification technique, based on time-domain analysis of the free decay response. Here, a modified Matrix Pencil (MP) method is coupled with the stabilization diagram to identify system poles. The main features of the method are the capability to assess simultaneously multiple time-histories in order to obtain a more comprehensive description of the system and, at the same time, a time saving analysis; the independence of tonal disturbances and noise; the generation of a qualitative measure of confidence on the results. The algorithm was implemented in a software package, and extensive evaluation of the method was conducted using flight data. The results of the evaluation confirmed the capability of the method to detect poles within proximity of tonal disturbances. In addition, indicated an efficiency improvement of 70% in automatic system pole identification in high-noise signals when compared to MP techniques not used in conjunction with stabilization diagram.