Exploring differently frequency domain analysis of MIMO aeroservo elasticity (ASE) system stability using H-infinity-norm

Sections 1 through 3 of the full paper explain our different exploration mentioned in the title, whose core consists of; (1) we derive the equations of motion in frequency domain for a multiple-input and multiple-output (MIMO) ASE system; (2) using the system stability theory, we prove that the H-infinity-norm of the frequency response function matrix of the ASE system is close to the infinity near the critical point of aeroservoelastic stability; (3) based on this unique property, we use the H-infinity-norm to develop a method for frequency domain analysis of ASE system stability so as to determine the instability boundary of the ASE system. Section 4 simulates a certain aircraft that is equipped with MIMO flight control system for yaw loop and roll loop to analyze the stability of the ASE system; the numerical results, given in Tables 1 and 2, and their analysis show preliminarily that: (1) the ASE system stability obtained with our frequency domain analysis method agrees well with that obtained with the pk method, which is closely related to Ref. 7 by Rodden and Johnson; (2) the stability boundary of the ASE system of the aircraft is smaller than that of the aircraft which is not equipped with the MIMO flight control system; (3) with the notch filter added to the control system for suppressing the critical mode, our frequency domain analysis method shows that the critical stability boundary increases prominently.