跪式起落架结构参数对直升机滚转模态频率影响的研究

Effect of Kneeling Landing Gear Structural Parameters on Helicopter Rolling Mode Frequence

铰接式单旋翼直升机的滚转模态是影响地面共振最关键的模态。文章针对跪式起落架结构和力的非线性特点,计算了起落架轮轴垂向力与缓冲支柱轴向力的传递系数。利用缓冲支柱及轮胎的静压缩试验数据,采用迭代计算的方法进行了全机地面平衡计算。基于刚度和阻尼等效计算原则,提出了跪式起落架系统的等效刚度和等效阻尼计算方法。通过对UH-60直升机仿真计算可知,摇臂外撑一定角度、缓冲支柱及轮轴长度增加、缓冲支柱与机身连接点下移能够不同程度的提高机体滚转模态频率。若将摇臂撑开30°,缓冲支柱伸长0.2 m,轮轴伸长0.2 m时,机体滚转模态频率可从3.54Hz提高到4.35Hz,比设计改进前提高了22.8%。通过改进起落架结构参数设计提高机体滚转模态频率,能够有效改善直升机的地面共振特性。

The roll mode of hinged single-rotor helicopter is the most important mode that affects ground resonance. Considering the nonlinear characteristics of the structure force of the kneeling landing gear, the transmission coefficient of the axial force of the vertical force of the kneeling landing gear＇ s wheel axle and the axial force of the oleo shock absorber was calculated. Using the static compression test data of the oleo shock absorber and the wheel, the calculation of helicopter ground balance was carried out by using iterative calculation method. Based on the equivalent calculation principle of stiff- ness and damping, the equivalent stiffness and equivalent damping calculation method of the kneeling landing gear system were presented. The calculation results of UH-60 show that some factors can improve the rolling mode fiequency, such as the angle of the rocker open out, the increase of oleo shock absorber and wheel axle and the connection point of the oleo shock absorber and the body moves down. If the rocker is open out 30 degrees and the length of the oleo shock absorber and the wheel axle increase by 0.2 m, the rolling mode fiequency is up to 4.35 Hz, which is increased by 22.8%. The ground resonance characteristics of helicopter can be improved effectively by improving the design of structural parameters of the landing gear and increasing the roll mode frequency of the body.