Influence of structural torsional degree of freedom on nose landing gear shimmy

Abstract The structural characteristic of combining a maneuvering mechanism and a shimmy damper into a single component is present in the nose landing gear of large civil aircraft. Establishing a more accurate shimmy model based on this property is crucial. The three torsional degrees of freedom shimmy of the nose landing gear was mathematically and physically modeled. The time domain curve, spectrum diagram, and bifurcation diagram were used to compare the three torsional degrees of freedom shimmy model and the single torsional degrees of freedom shimmy model. The three-torsional freedom model predicts a greater amplitude and a longer convergence time in comparison to the findings of the single-torsional freedom model. The sliding tube's torsional vibration frequency falls from 10.9Hz to 8.1Hz in the three-torsional degree-of-freedom model, while the structure's lateral vibration frequency stays the same. The three-torsional freedom model predicts a decrease in the region of stable and torsional shimmy and an increase in the area of lateral and quasi-periodic shimmy. The amplitudes of all degrees of freedom in the three torsional degrees of freedom model, regardless of whether it is torsional or lateral, are greater than those in the single torsional degrees of freedom model when the vertical load is fixed. By increasing the torsional degrees of freedom of the shimmy damper and the main fitting, the inertia, stiffness, and damping in the torsional direction are redistributed in the three-torsional shimmy vibration model, which reduces the stability of the system.