控制器非线性对飞机纵向飞行品质的影响分析

针对飞机控制系统执行机构具有非线性这一特点,选用某歼击机作为研究对象,分析各类非线性环节对飞机纵向短周期特性的影响。首先分析了死区、间隙和速率饱和等非线性环节的基本特性,建立了相应的包含非线性环节的飞行动力学模型,然后,基于Chalk准则计算不同非线性参数下的飞行品质指标,进行飞行品质评价。通过对不同飞控系统构型的对比研究,探讨了执行机构非线性对飞行品质的影响。研究结果表明,各非线性环节都将对系统的快速性产生不利影响,使系统有效上升时间增加,相位延迟增加。其中,间隙还会造成系统阻尼减小,可导致系统不稳并出现极限环振荡。

Effect of nonlinear characteristics of the control system on aircraft longitudinal flying qualities

For the nonlinear characteristics of the execution mechanism of the flight control system,in this paper,we select a fighter as the research subject to analyze the effect of nonlinear elements on aircraft longitudinal short-period characteristics.The data of a fighter dynamics is used to study.At first,the Chalk criterion for evaluating short-period FQ is introduced.And then the aircraft system dynamic model containing the nonlinear elements of flight control systems are built.The basic features of different nonlinear element,such as dead zone,backlash and actuator rate limit,are analyzed.At last,through the time-domain simulation the effect of nonlinear elements on flying quality are discussed with the use Chalk criterion.Comparing and analyzing the results,we find that the existence of dead zone,backlash and rate limit can increase the system phase delay and have great adverse effect on the speed of response.The backlash can also make the system damping smaller and the system instable,and finally cause limit loop oscillation.