Design, structure analysis and shock control of aircraft landing gear system with MR damper

This study proposes a new magneto-rheological aircraft main landing gear (MRAMLG) system and comprehensively treats from a mathematical modelling to drop testing for the evaluation of the landing efficiency. A mathematical model is formulated based on specifications and requirements of existing small aircraft Oleo type landing gear system. To ensure structural stability of the landing gear components such as main trust, column and trunnion, a transient structural analysis is carried out using the finite element method (FEM) and a fatigue life is analysed based on empirical formulas and the rainflow-counting (RC) algorithm. Subsequently, a novel controller is formulated to enhance the landing efficiency by integrating the time delay model and 3-stage hysteresis regulator. In the synthesis of the controller, a desired force model based on the energy law is added to accurately track the desired yield stress needed for the desired field-dependent force. In this work, the proposed control algorithm is named as the model-based force-tracking (MBFT) controller. To evaluate the landing efficiency or shock struct efficiency (SSE) of the proposed MRAMLG, an experimental apparatus for drop test is designed and manufactured by considering a dummy (sprung) mass of 640-720 kg at the maximum sink speed of 3 m s-1. The sink speed represents the rate of descent of the MRAMLG's tire just before it touches the ground. It is demonstrated from simulation and experiment that the SSE with the MBFT controller is higher than 83% across various landing conditions with different sprung mass and sink speed, while the conventional controllers, proportional-integral and skyhook, compared to MBFT, do not show consistent performance depending on the sprung mass and sink speed.