提出了直升机垂直着陆撞击激起旋翼扰动的动力学模型，为预估粗暴着陆时起落架载荷和旋翼液压阻尼器轴向速度幅值给出了一种数值模拟方法。以弹性轴承旋翼直升机为例，对垂直着陆时直升机机体、起落架、旋翼桨叶及阻尼器的动力响应进行了数值模拟，分析了着陆撞击引起机体和旋翼扰动的力学机理，可知在起落架触地后的第1个振荡周期中，各片桨叶将经历其不同的摆振幅值，并激起旋翼摆振后退型响应。着陆撞击引起桨叶的大扰动，将冲开阻尼器的定压安全活门，严重降低其等效阻尼。随机着陆时，起落架触地速度及过载系数、旋翼挥舞及摆振幅度和阻尼器速度峰值等动态参数由于着陆时机体的姿态角及角速度不同呈现很大的分散性，其分散性与着陆高度有关。
A dynamic model for helicopter rotor perturbation excited by impact of vertical landing is proposed, and a numerical simulation method is given to predict landing gear loading and the axial velocity amplitude of hydraulic lag damper in hard landing. Dynamic responses of helicopter fuselage, landing gears, rotor blades and lag dampers are numerical simulated in the vertical landing of an elastic globe-hinge rotor helicopter. The mechanical mechanism of lead-lag disturbance of the rotor blade due to the landing impact is analyzed. It is found that in the first period of oscillation after landing, each blade will undergo different amplitude of lead-lag displacement and result in response of regressive lag mode of rotor. Large disturbance of the rotor blade caused by landing impact will blow off the relieve valve of the damper, significantly decreasing the equivalent damping of the damper. As the sample helicopter undergoes a random vertical landing, the dynamic parameters such as impact velocities and overload factors of landing gears, the amplitude of blade flap and lead-lag displacement, and axial velocity of the damper are shown to be significantly scattered due to different attitudes and angular velocities of the airframe at landing, and the scatter depends on landing altitude.
[1] BAUCHAU O A, LIU H Y. On the modeling of hydraulic components in rotorcraft systems[J]. Journal of American Helicopter Society, 2006, 51(2):175-184.
[2] EYRES R D, CHAMPNEY A R, LIEVEN N A. Modeling and dynamic response of a damper with relief valve[J]. Nonlinear Dynamics, 2005, 40(2):119-147.
[3] 胡国才, 柳泉, 罗云宝. 直升机旋翼液压阻尼器动载荷分析[J]. 应用力学学报, 2014, 31(1):105-109. HU G C, LIU Q, LUO Y B. Dynamic load analysis of helicopter rotor hydraulic lag damper[J]. Chinese Journal of Applied Mechanics, 2014, 31(1):105-109(in Chinese).
[4] NIEBANCK C, GIRVAN W. Sikorsky S-76 analysis, design, and development for successful dynamic characteristics[C]//Proceedings of the American Helicopter Society 34th Annual Forum. Fairfax, VA:American Helicopter Society, 1978.
[5] 王唯, 夏品奇. 采用磁流变阻尼器的直升机"地面共振"分析[J]. 南京航空航天大学学报, 2003, 35(3):264-267. WANG W, XIA P Q. Ground resonance analysis of helicopter with magnetorheological lag damper[J]. Journal of Nanjing University of Aeronautics and Astronautics, 2003, 35(3):264-267(in Chinese).
[6] 胡国才. 带机体状态反馈的直升机地面共振分析[J]. 航空学报, 2006, 27(3):427-431. HU G C. Analysis of helicopter ground resonance with fuselage state feedback[J]. Acta Aeronautica et Astronautica Sinica, 2006, 27(3):427-431(in Chinese).
[7] WANG W, XIA P Q. Adaptive control of helicopter ground resonance with magnetorheological damper[J]. Chinese Journal of Aeronautics, 2007, 20(4):501-510.
[8] GUALDI S, MASARATI P, MORANDINI M, et al. A multi-body approach to the analysis of helicopter-terrain interaction[C]//28th European Rotorcraft Forum, 2002:72.1-12.
[9] THO C H, SPARKS C E, SAREEN A, et al. Efficient helicopter skid landing gear dynamic drop simulation using Lsdyna[J]. Journal of the American Helicopter Society, 2004, 49(4):483-492.
[10] ZHU Z H, MICHEL L, JAMES M. Fatigue life estimation of helicopter landing probe based on dynamic simulation[J]. Journal of Aircraft, 2009, 46(5):1533-1543.
[11] VALLONE G, MANES A, SBARUFATTI C, et al. Helicopter harsh landing vents:A computational hybrid methodology to estimate fuselage damage[J]. Journal of Aircraft, 2013, 50(6):1896-1907.
[12] PITT D M, PETERS D A. Theoretical prediction of dynamic inflow derivatives[J]. Vertica, 1981, 5(1):21-34.
[13] HU G C, XIANG J W, ZHANG X G. Dynamic stability analysis for nonlinear helicopter rotor/fuselage coupled system[J]. Chinese Journal of Aeronautics, 2003, 16(1):22-28.
[14] GAONKAR G H, PETERS D A. Review of dynamic inflow modeling for rotorcraft flight dynamics[J]. Vertica, 1988, 12(3):213-242.
[15] XIN H, HE C J. An efficient panel ground effect model for rotorcraft simulations[C]//Proceedings of the American Helicopter Society 61st Annual Forum. Fairfax, VA:American Helicopter Society, 2005.
[16] HU G C, XIANG J W, ZHANG X G. On influence of kinematics to equivalent damping of helicopter blade hydraulic damper[J]. Applied Mathematics and Mechanics, 2002, 23(8):922-930.
[17] LINDSLEY N J, TALEKAR N B. A tire model for air vehicle landing gear dynamics[EB/OL].[2012-02-25]. http://ww.adams.com/news/events/userconf/na/2000/18-USAF-tire-landing-gear.pdf.
[18] TASKER F A, CHOPRA I. Assessment of transient analysis techniques for rotor stability testing[J]. Journal of the American Helicopter Society, 1990, 37(1):39-50.
[19] 吴靖, 胡国才. 带定压活门的液压阻尼器力学性能研究[J]. 华中科技大学学报(自然科学版), 2017, 45(2):44-49. WU J, HU G C. On mechanical features of hydraulic damper with pressure relieve valve[J]. Journal of Huazhong University of Science and Technology (Natural Science Edition), 2017, 45(2):44-49(in Chinese).
[20] GAONKAR G H. Toward a complete stochastic model of air wake turbulence for helicopter shipboard operation[C]//Proceedings of the American Helicopter Society 63rd Annual Forum. Fairfax, VA:American Helicopter Society, 2007.
[21] 徐广, 胡国才, 王允良. 直升机-舰船动态配合着舰仿真研究[J]. 飞行力学, 2016, 34(2):20-23. XU G, HU G C, WANG Y L. Research on shipborne helicopter-ship dynamic interface and simulation of landing on the flight deck[J]. Flight Dynamics, 2016, 34(2):20-23(in Chinese).
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