Control of Impact Loads on Aircraft Landing Gears Using Magnetorheological Fluid Dampers

使用磁流变液阻尼器控制飞机起落架上的冲击载荷：飞机起落架中的减震器需要在着陆过程中吸收和消散冲击动能，以减少传递到飞机主体和乘客的振动。本研究的目的是研究在起落架系统中使用磁流变液阻尼器的性能。飞机起落架减振器的基本功能是吸收和耗散飞机机身框架在着陆过程中的冲击动能，从而将传递给飞机主体的振动降低到可以容忍的水平。通常使用的是油压杆，本质上是减震器，它有一个带有气体和油的流体弹簧。油气减振系统是目前大中型飞机上最常用的减振系统之一，因为它在着陆和滑行过程中提供了减震和有效的减振。在压缩过程中，石油和天然气要么保持分离，要么混合在一起，具体取决于设计类型。在最初的撞击之后，随着空气压力迫使油通过后坐力小孔返回到它的腔内，能量被耗散。大多数设计都有一个通过流体流动小孔延伸的计量销，可以改变小孔的面积。这一变化是通过塑造计量销来调整的，以便支柱负载在动态负载下相当恒定。一旦设计了计量针，阻尼值就会随时间变化，以满足不同的加载条件。然而，如果可以根据负载和进场要求，例如飞机的不同重量，或者当飞机在着陆时具有不同的下沉率时，改变阻尼将是最理想的。在飞机着陆期间，起落架接触到跑道，飞机的悬浮质量很少传递到跑道，因为飞机的机翼仍然承担着飞机的大部分重量和升力。由于着陆后升力缓慢减小，起落架所经历的表观质量随时间变化。目标是优化升力的渐进式降低，使飞机在垂直方向上经历恒定的减速，以确保结构完整性和乘客的乘坐舒适性。上述研究的科学方法是(I)具有时变质量和阻尼性的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。这项工作对飞机工业的新颖性和预期意义：磁流变液阻尼器通过在磁流变液上施加磁场来非常迅速地改变其阻尼性。该技术已成功地应用于车辆悬架系统中，以实现车辆振动的半主动控制。在飞机结构中也可以实现类似的减振。与起落架相关的行业，如加拿大Heroux Devtec、Noramtec-Montréal、QC、Messier-Bugatti-Dowty，将从这项研究的结果中受益最大。

Control of Impact Loads on Aircraft Landing Gears Using Magnetorheological Fluid Dampers: Shock absorbers in aircraft landing gears are required to absorb and dissipate the impact kinetic energy during landing so as to reduce the vibrations transmitted to the main aircraft body and to the passengers. The objectives of the proposed research are to study the performance of the landing gear system by using a magentorheological fluid damper in the system. The basic function of the shock absorber in aircraft landing gears is to absorb and dissipate the impact kinetic energy of the aircraft body frame during landing so as to reduce the vibrations transmitted to the main body of the aircraft to a tolerable level. Normally, oleo struts, which are essentially shock absorbers that have a fluid spring with gas and oil are used. Oleo-pneumatic shock absorber system is currently one of the most common in medium to large aircrafts, as it provides shock absorption as well as effective damping during landing and taxiing. During the compression process, the oil and gas either remain separated or are mixed depending on the type of design. After the initial impact, energy is dissipated as the air pressure forces the oil back into its chamber through recoil orifices. Most designs have a metering pin extending through the fluid flow orifice, which can vary the orifice area. This variation is adjusted by shaping the metering pin so that the strut load is fairly constant under dynamic loading. Once the metering pin is designed, the damping varies as a prescribed function of time to meet different loading conditions. However, 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 when the aircraft has different sink rate at the time of touchdown. During aircraft landing, the landing gears touch the runway with very little of the suspended mass of the aircraft transmitted to the runway because the aircraft wings still carry the bulk of the aircraft weight with the lift force. As the lift is slowly reduced after touch down, the apparent mass experienced by the landing gears changes as a function of time. The objective is to optimize the progressive reduction in the lift such that the aircraft experiences a constant deceleration in the vertical direction in order to ensure the structural integrity and ride comfort to the passengers. The scientific approaches for the above studies are (i) Analytical solutions to the equations of motion which is a system with time varying mass and damping properties, (ii) numerical simulation of the landing gear dynamics including the magnetorheological fluid dampers. Novelty and expected significance of the work to the aircraft industry: Magnetorheological fluid dampers change their damping property very rapidly by the application of a magnetic field across the MR fluid. The technology has been very successfully applied in vehicle suspensions in order to control the vehicle vibrations in a semi-active fashion. A similar vibration reduction can be achieved in aircraft structures also. The industries involved with the landing gears, such as Heroux Devtec Canada, Noramtec - Montréal, QC, Messier-Bugatti-Dowty, will benefit the most with the outcome of this research.