Elementary Model of Nose Gear Retraction and Oleo-Pneumatic Strut Compression

摘要

Landing gear systems have two major non-linear components that need to be modeled in order to fully represent a complete landing profile, the extension actuator and the oleo-pneumatic strut. In order to test the equations of motion, the components were put together as part of a system similar to the F-15 nose gear. Working Model tested the geometry, yielding a geometry specific force time diagram that compares well to experimental results. A real system's actuator follows a control system input, which is designed to follow a force displacement path. The equations governing a typical actuator are integrated to compare two models: a simplified model and one that assumes no leaking nor compressibility of the fluid. The strut acts as a spring mass system, with a non-linear spring and a damper proportional to the square of the velocity. The strut equations of motion are formulated as well as the constraints for both constant velocity and a simulated drop test. These equations are also integrated to show either a force displacement or time displacement diagrams. The results are then compared to the expected values for each type of test, showing data consistent with experimental and other computational methods.