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

飞机在着陆时受到冲击载荷的影响。冲击载荷的强度取决于进近速度、着陆条件、控制面展开、跑道粗糙度等因素。由此产生的振动会影响乘客的舒适度和结构的完整性。提出的研究目标是研究起落架系统通过结合磁流变阻尼器来减少振动的性能。飞机起落架减震器的基本功能是吸收飞机降落时机体框架的冲击动能。目前使用的是油-气减震器系统，本质上是气体和油形成流体弹簧和减震器的减震器。它们有一个通过流体流动孔延伸的计量销，它可以改变孔的面积。通过塑造计量销，在动态载荷下调整支撑载荷为相当恒定。如果阻尼能根据载荷和进近要求（如飞机的不同重量或着陆时的不同下沉速率）而变化，那将是理想的。***在着陆时，飞机机翼仍以升力承载飞机的大部分重量。目标是优化升力的逐步减小，使飞机在垂直方向上经历恒定的减速。这反过来又减少了结构部件的振动应力。***上述研究的科学方法是(i)系统运动方程的解析解（本质上是一个具有时变质量和阻尼特性的系统），（ii）起落架动力学（包括磁流变阻尼器）的数值模拟，以及（iii）采用硬件在环方法对磁流变阻尼器组件进行实验研究。***这项工作的新颖性和预期意义：磁流变阻尼器通过在磁流变液中施加适当的电流，可以非常迅速地改变其阻尼特性。通过引入蓄能器和阀，可以在MR阻尼器中实现刚度的变化。该技术已非常成功地应用于车辆悬架，以半主动方式控制振动。预计在飞机结构中也可以实现类似的减振。***HQP培训将成为本研究的一部分。磁流变阻尼器在车辆悬架中的半主动振动控制已被发现是成功的。三位博士生正在研究配备磁流变阻尼器的系统的不同方面。拟建项目**拟再培养2名博士研究生

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**