Nonlinear Response of Aeroservoelastic Systems Using Discrete State-Space Approach

A generalized direct simulation method using a discrete time-domain state-space approach for transient response of both open- and closed-loop nonlinear aeroelastic systems is developed. Based on a nonlinear parameter scheme that divides the nonlinear system into sublinear systems, the method first assembles a set of discrete time-domain state-space equations and then computes the transient response by switching the time-integration procedure between this set of state-space equations. In so doing, various nonlinearities in structures, aerodynamics and/or control systems can be included. The method is validated by correlating the transient response of a three-degree-of-freedom airfoil section in freeplay with the experimental and numerical results obtained by Conner et al. The stability of a strut-braced wing with buckling effects at two trim conditions is also studied, which shows that the aeroelastic stability of the present strut-braced wing is trim-condition dependent. Such results clearly could not be obtained if using a linear aeroelastic analysis.