一种直升机运动模态中纵横向耦合分析方法

An analytical method for longitudinal-lateral couplings in helicopter motional modes

提出了一种定量分析直升机纵横向耦合特性的方法,包括运动模态中状态量间耦合作用的幅值特性、时间特性和积分特性。幅值特性描述耦合作用的相对强弱,时间特性描述耦合作用起增强/减弱作用的时间比例,积分特性描述耦合作用引起状态量发散/收敛的快慢。将该方法应用于"美洲豹"直升机悬停状态的典型纵向振荡模态,对比分析了该运动模态纵横向分离和纵横向耦合情况下状态量之间的耦合特性。分析发现,纵横向耦合使得横向速度和滚转角速度对俯仰角速度产生耦合,耦合强度是纵向速度对俯仰角速度耦合作用的近3倍,并加快了俯仰角速度的发散。纵横向耦合显著改变了该运动模态的耦合特性,进而影响了其稳定性。

A quantitative method to analyze helicopter longitudinal-lateral coupling char- acteristics was put forward, including amplitude characteristics, time characteristics, and in- tegration characteristics of couplings among state variables of a motional mode. Relative strengths of couplings could be reflected by amplitude characteristics. Time ratios of couplings with intensifying or diminishing effects could be described by time characteristics. And divergence or convergence rates of state variables caused by couplings could be represen- ted by integration characteristics. With the typical longitudinal oscillatory mode of a hove- ring Puma helicopter as an example, the couplings characteristics among state variables of the mode were analyzed through comparison between longitudinal-lateral decoupled and coupled conditions. It showed that, because of longitudinal-lateral couplings, both lateral velocity and roll rate had effects on pitch rate, and their strength was almost three times the effect of longitudinal velocity on pitch rate, and the divergence rate of pitch rate was accelerated. Longitudinal-lateral couplings had a great effect on coupling characteristics of the mode, and the dynamic stability was influenced further.