A model of equivalent beam vibration for Mars quadcopter arm and experimental verification

In Chinese Mars sample return mission, a Mars quadcopter is planned to be employed to collect different types of rocks, rock fragments, and loose soil on the surface of Mars. Due to the difficulty of generating thrust in the thin Martian atmosphere, the quadcopter needs to undergo an extreme lightweight design to reduce its gravity on Mars. The lightweight design results in a decrease in the stiffness of the rotor arm, leading to the first natural frequency of the arm being lower than the maximum operating rotational frequency of the rotor. The unbalanced forces generated during the acceleration of the rotor’s rotation induce resonance in the arm, resulting in significant vibrational displacements at the end of the arm. To improve the support stability of the arm, it is necessary to predict the vibrational displacements at the end of the arm through numerical simulation methods. This paper establishes an equivalent beam model for the vibrational characteristics of the arm based on multi-layer shells, torsional springs, and rotational damping. The beam vibration model is simplified by restricting higher-order small deformations of the beam section. The comparison between the simulated data of the beam model and the experimental data shows that the equivalent beam model established for the vibrational characteristics of the arm can predict the displacement response at the end of the arm during resonance. The comparison of simulation data between the beam model and the simplified beam model shows that employing the simplified beam model for simulations can reduce the computational time by 99.1%.