Passive roll stabilization using internal fluid dynamics in insect-scale models

Flight stabilization in unsteady environments remains a significant challenge in aerial robotics, particularly for microscale vehicles or those with internal fluidic payloads. This study draws inspiration from hypothesized passive fluid redistribution mechanisms in flying insects and explores the role of introducing internal liquid mass to enhance roll stability. The main objective is to improve passive stabilization without entirely relying on active control mechanisms. Experimental validation is conducted with a simple cylindrical model that was geometrically scaled 1:1 to the Goliath beetle to observe how the internal sloshing helps in stabilizing the aerial disturbances. Four experimental cases were tested – 1. Reference case hollow model, 2. The same model, half-filled with water, 3. The model is filled with an equivalent solid mass, 4. The model has an equivalent solid weight distributed along its roll axis. Each configuration was subjected to three controlled impact tests simulating wind gusts: Run 1 (~ 7.35mJ) is where a 5g weight was dropped from 15cm asymmetrically to one wing to generate roll motion; Run 2 (~ 14.97mJ) used a 10g weight; Run 3 (~ 29.94mJ) used a 20g weight.

All the impact and roll events are captured and analyzed using Tracker software to gather the wingtip displacement (Y-position) over time. Results from these successive runs under the same conditions reveal that the water sloshing (case 2) introduces a passive stabilizing moment that suppresses the roll perturbation and damps the oscillatory motion. This approach might benefit the aerial vehicle manufacturers, especially for UAVs carrying liquid payloads or those used for wildlife suppression.