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

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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