Aircraft Dutch roll equivalent matching initial value selection method

Abstract

The invention discloses an aircraft Dutch roll equivalent matching initial value selection method and belongs to the technical field of aircraft operation stabilization system design. The method comprises the steps that first, amplitude and phase data of a sideslip angle within the range of 0.1-10rad / s relative to a pedal force high-order system is obtained; second, a second-order system equivalent to a high-order transmission function in the first step is acquired based on a typical second-order system; third, a damping ratio initial value of a Dutch roll is determined according to a maximumvalue of an amplitude curve and an amplitude at the position of omega=0.1; fourth, a frequency initial value omega<d> of the Dutch roll is calculated; fifth, the amplitude at the position of omega=0.1and the frequency initial value are utilized to calculate a gain K initial value; and sixth, a time delay value tau is determined. According to the method, an initial value of equivalent matching isobtained according to the amplitude and phase data of the high-order system, the initial value is approximate to an exact solution, and it can be guaranteed that the equivalent matching requirement ismet in subsequent solving. Through the method, the work of repeatedly debugging the initial value is avoided, working efficiency is improved, and calculation difficulty is lowered.

Description

technical field [0001] The invention belongs to the technical field of aircraft control system design, and in particular relates to a method for selecting an initial value of an aircraft Dutch roll equivalent fitting. Background technique [0002] Most current aircraft are designed with a control stability augmentation system. There are far more aircraft modes after control stabilization than those without stabilization, so it is difficult to directly apply mature flight quality specifications. At present, the typical method is equivalent matching, that is, to find an equivalent low-order system for a certain high-order system, and the difference of the corresponding output of the two systems in a certain frequency domain range satisfies certain index conditions. Equivalent low-level systems can use quality specifications for modal analysis, flight quality assessment, etc. [0003] The equivalent matching principle is that the index function of the amplitude and phase diff...

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Problems solved by technology

The expression of the mismatch degree function is complex. When using algorithms such as least squares and Newton iteration, the calculation of the initial value will affect the accuracy of the equivalent fitting. Improper selection of the initial value will result in unreasonable results, which cannot reflect the characteristics of high-order systems.

[0009] Initial value selection is a key task in equivalent fitting. At present, there is no unified method for initial value selection, which mainly depends on the experience of engineers.

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