垂索-辅助索系统的建模与固有特性

辅助索被认为是长索振动控制中一种富有潜力的手段。为研究安装辅助索后系统的固有特性及其随关键参数的变化规律,建立了由N根垂索和M道辅助索组成的索网系统的模型,得到其无量纲运动方程,引入边界条件、连续条件和平衡条件进行求解。将模型退化到双索-辅助索系统,求得其无量纲频率方程。采用数值分析研究了Irvine参数λ^(2)、辅助索刚度和位置、波速比η等关键参数对系统频率和模态的影响。研究表明,当两索参数相同时,垂度仅影响反相频率,故同相振动和反相振动的ω-λ^(2)曲线分别表现为“穿越”(crossover)现象和“转向”(veering)现象。当λ^(2)为某特定值时,任意辅助索刚度下的一阶反相振动频率均等于一阶同相频率,从而频率曲线均通过第一个“穿越”点。两索参数相同时,增大辅助索刚度仅提高系统反相振动频率,但其增幅不超过1。两索波速不同时,系统所有频率均随波速差异增大而发生往高阶的“跳阶”(jumping)现象,且频率阶次越高“跳阶”次数越多。

带自锁机构的垂索回收无人机翼尖拦阻钩设计

针对垂索回收固定翼无人机的回收特点,设计了一型具有自锁功能的翼尖拦阻钩。处于回收航路的无人机与拦阻索接触时,自锁机构在两者相互作用下快速勾住并锁紧拦阻索。该机构通过弹簧及连杆实现自主回收,解决了拦阻后无人机下滑的问题。利用CATIA软件进行拦阻钩模型的运动仿真和关键承力零件过载情况的有限元分析,确保装置可靠。该型拦阻钩设计原理科学可行,通过结构适配设计,可应用于多型舰载小型固定翼无人机的回收,应用前景广泛。

Calculation model and mechanism analysis for rain-wind-induced vibration of stay cable

Rain-wind-induced vibration of cable was studied based on previous research achievements. According to the quasi-steady assumption, the governing equation of vertical motion of the cable was derived and the criterion for unstable motion and occurrence mechanism was studied. A comparison was performed between the oscillation responses of the stay cable obtained from calculated model and previous results. The results indicate that the analysis model can reflect the main characteristics of wind-rain-induced vibrationt of the cable which is amplitude- and velocity-restricted, and it is probably related with the periodic vortex shedding of wake flow. It is essential for the occurrence of rain-wind-induced or wind-induced vibration of cable that the derivative of lift coefficient with respect to transient angle of attack is less than zero. When rain-wind-induced vibration occurs, the aerodynamic force has a dual function for the vibration, and the maximum amplitude of stayed-cable is determined by the relative value of aerodynamic exciting force and aerodynamic damping force.