Attenuation of Vibrations in Aircraft Landing Gears due to Impact Loads Using Magnetorheological Dampers

飞机在着陆时会受到冲击载荷的影响。冲击载荷的强度取决于进场速度、着陆条件、操纵面布置、跑道粗糙度等。由此产生的振动可能会影响乘客的舒适性和结构完整性。拟议研究的目的是研究起落架系统通过加入磁流变液阻尼器来降低振动的性能。飞机起落架减振器的基本功能是吸收飞机机身框架在着陆过程中的冲击动能。目前使用的是油气减振器系统，本质上是由气体和油形成流体弹簧和阻尼器的减震器。它们有一个通过流体流动孔口延伸的计量销，可以改变孔口面积。通过对计量销进行整形，使支柱载荷在动态载荷作用下保持相当恒定。如果可以根据负载和进场要求，例如飞机的不同重量或着陆时不同的下沉率，来改变阻尼值，那将是最理想的。 在着陆过程中，飞机的机翼仍然承担着飞机的大部分重量和升力。目标是优化升力的递减，使飞机在垂直方向上经历恒定的减速。这反过来又降低了结构部件中的振动应力。 上述研究的科学方法是(I)系统运动方程的解析解，(Ii)包括磁流变液阻尼器在内的起落架动力学的数值模拟，以及(Iii)采用半实物方法对磁流变液阻尼器部件进行实验研究。 这项工作在更好的车辆设计中的新颖性和预期意义：磁流变液阻尼器通过向磁流变液施加适当的电流来迅速改变其阻尼性。通过引入蓄能器和阀门，可以在磁流变液阻尼器中实现刚度的变化。该技术已成功地应用于车辆悬架的半主动振动控制。预计在飞机结构中也可以达到类似的减振效果。 HQP培训将成为本研究的一部分。在车辆悬架中使用磁流变液阻尼器对平顺性振动进行半主动控制已被证明是成功的。三名博士生正在研究配备磁流变阻尼器的系统的不同方面。在拟议的项目过程中，建议再培训两名博士生

Aircrafts are subject to impact loads during landing. The intensity of the impact loads depends on the approach velocity, landing conditions, control surface deployment, runway roughness etc. The resulting vibrations can affect passenger comfort and structural integrity. The objectives of the proposed research are to study the performance of the landing gear system in reducing vibrations by incorporating magnetorheological fluid dampers. The basic function of the shock absorber in aircraft landing gears is to absorb the impact kinetic energy of the aircraft body frame during landing. Oleo-pneumatic shock absorber system, which are essentially shock absorbers with gas and oil forming a fluid spring and damper, are currently used. They have a metering pin extending through the fluid flow orifice, which can vary the orifice area. By shaping the metering pin the strut load is adjusted to be fairly constant under dynamic loading. It would be ideal if the damping could be varied according to the load and approach requirements such as for different weight of the aircraft or different sink rate at the time of touchdown. During landing, the aircraft wings still carry the bulk of the aircraft weight with the lift force. The objective is to optimize the progressive reduction in the lift such that the aircraft experiences a constant deceleration in the vertical direction. This in turn reduces the vibratory stresses in the structural components. The scientific approaches for the above studies are (i) Analytical solutions to the equations of motion of the system which is essentially one with time varying mass and damping properties, (ii) numerical simulation of the landing gear dynamics including the magnetorheological fluid dampers, and (iii) experimental studies on the MR damper component following a Hardware-in-the-loop approach. Novelty and expected significance of the work in better vehicle design: Magnetorheological fluid dampers change their damping property very quickly by the application of appropriate current to the MR fluid. Variation in stiffness can be achieved in the MR damper by introducing an accumulator and a valve. The technology has been very successfully applied in vehicle suspensions to control vibrations in a semi-active fashion. It is expected that similar vibration reduction can be achieved in aircraft structures also. HQP training will form a part of this research. MR fluid dampers in vehicle suspensions for semi-active control of ride vibrations have been found to be successful. Three Ph.D. students are working on different aspects of systems equipped with MR dampers. It is proposed to train 2 more Ph.D. students in the course of the proposed project