Combined time- and frequency-domain aircraft system identification using pareto optimization

Aircraft system identification can either occur in the time-or frequency-domain with each approach having inherent advantages and disadvantages. For example, time-domain modelling generates superior time history matches and has a superior ability to achieve a trim solution. However, time-domain models do not provide a high degree of insight to the frequency responses of the system, which is important for control law development and for matching handling qualities for pilot-in-the-loop simulation — this is a strength of the frequency-domain approach. This paper utilises a Pareto optimization procedure to combine both the time- and frequency-domain approaches and exploit the strengths of both methods. Pareto fronts are generated for the system identification of a 6 degree-of-freedom forward flight model at 90 kts of the National Research Council of Canada’s Bell 412 helicopter. The generated Pareto fronts showed the necessity of balancing the time- and frequency-domain matches whereby moving from the compromise solution to either the isolated time- or frequency-domain solutions resulted in a small improvement in one while the other suffered relatively more. Accordingly, the multi-objective solution using Pareto optimization capitalized on the strengths of both approaches and avoided an overspecialized solution in either of the domains.
ASME 2021 International Mechanical Engineering Congress and Exposition, November 1-5, 2021, Virtual, Online