Finite element analysis of static and modal characteristics of quadrotor UAVs

Abstract

Structural stiffness and low-frequency vibration characteristics govern the load-carrying reliability of a quadrotor airframe. An ANSYS Workbench finite-element model was used to calculate the response of a four-arm frame under central downward loads of 100, 200, and 300 N. Equivalent stress, total deformation, the first six natural frequencies, and the associated mode shapes were obtained under a common material and support definition. Peak stress increased from 2.2243 to 6.6730 MPa and peak deformation from 0.0016145 to 0.0048436 mm over the investigated load range, with no change in the dominant load-transfer path. The modal solution yielded frequencies from 89.870 to 89.887 Hz; modes 1 and 2 and modes 3 and 4 were coincident within the reported precision. A published finite-element study of a different UAV frame placed its first three modes between 72.294 and 141.32 Hz, which is the same frequency order as the present solution. The calculated stress concentrations and narrow modal band identify the arm junctions and propulsion-speed range that require attention in subsequent structural assessment.