吊挂物为刚体模型的直升机外吊挂飞行平衡与稳定性分析

基于外吊挂刚体假设,建立直升机-刚体吊挂耦合非线性动力学模型,刚体模型的外吊挂引入了额外的自由度和额外约束,使原来的9阶直升机非线性动力学方程增加到19阶,并通过小扰动假设进行线性化。利用延拓方法对直升机-刚体吊挂系统在不同的飞行速度下进行配平,与直升机单体飞行的实验数据以及直升机-质点吊挂系统的计算结果进行对比,分析带刚体外吊挂的直升机与无吊挂和质点吊挂模型平衡状态的差别。采用差分法计算刚体吊挂假设下直升机的运动模态,并分析加入外吊挂后对直升机稳定性的影响。结果表明,刚体外吊挂给系统引入5个新的运动模态,其中吊索摆动的两个运动模态是稳定的,而吊挂姿态运动的3个运动模态不稳定,同时吊挂的引入使得直升机运动的短周期模态和滚转模态变得不稳定,严重影响了直升机的飞行品质。

Equilibrium Characteristics and Stability Analysis of Helicopter with Rigid-Body Modeling Slung-Load

Based on rigid body modeling slung load hypothesis, a nonlinear dynamics model of the helicopter with slung load coupl i ng system is presented, and the rigid body modeling slung load brings in ex tr a degrees of freedom and constraints, which makes the nonlinear equations of helic o pter motion increase from 9 orders to 19 orders. The nonlinear equations are li n earized by small perturbation hypothesis and trimmed by continuation. Then the t rimmed results are compared with the experimental data of helicopter flight and the cal culation results of helicopter with mass point modeling slung load. The motion modes of helicopter with rigid body modeling slung load hypothesis are calculated with difference method, and the impacton stabili ty of helicopter by extra slung load is analyzed at the same time. Results sho w that the rigid slung load adds five new motion modes to the system, two of wh i ch about sling swinging are stable, three of which about slung load attitude mot i on are unstable. Meanwhile, the introduction of slung load makes the sh o r t period mode and the roll mode of helicopter unstable, which has a strong impac t on the flight quality of helicopter.