Research On Robust Stability Of Multi-loop Aeroservoelastic System

Aeroservoelasticity (ASE) considers the interaction betweenaerodynamics,inertial,structural, actuation, sensing ,and control system.Theclosed-loop interaction of these elements may cause aircraft instabilities. Thus,aeroservoelastic stability analysis is an importance work for new aircraft designs andflight test. For this reason, some new methods based on advanced multi-loop systemstability analysis and advanced signal processing tools are presented to meet thedemand of new aircraft flight testing. The research results are applied to new aircraftASE stability analysis, and achieve great military and economy benefit. The mainresults of this thesis are described as follows:1. A detailed scheme for ASE flight testing is designed firstly, which uses the sweepsignal as command to actuator. Finally, a flight test to evaluate the ASE stability isaccomplished.2. A time-frequency filtering method based on Morlet wavelet is proposed to separatethe noise form flight data, which can reduce the effects of noise and provide a moreaccurate analysis result.3. The return difference matrix (RDM) method is investigated, which evaluates thestability margin of aeroservoelastic system by determining the minimum singularvalue of the system return difference matrix. And the relationship between singularvalue and classical gain and phase margins are given for tesing engineer.4. In order to overcome the conservativeness, a new method based on robustμanalysis is presented to evaluate the stability margin of multiloop aeroservoelasticsystem from flight test data. And the relationship betweenμand classical gainand phase margins is discussed in this paper, the evaluation diagram ofμand classical gain and phase margins for stability margins analysis is given.5. An ASE data processing system is constructed and validated by real flight testing data, thefinal results show effectiveness and efficiency of the system.Finally, the return difference matrix method and robustμmethod combined withtime-frequency filter are validated by real flight testing data, and the results arecompared with classical stability margin analysis method for single input single output(SISO) system, a detailed discussion is given.The results illustrate that these method presented in this paper can be used toobtain satisfied stability margin during flight for multiloop aeroservoelastic system.Also, These methods can used to analyse stability margins of MIMO control system.Thus these methods for system stability margin analysis play important role in moderncombat aircrafts design and test.