A Low-Cost Variable Buoyancy System for Hybrid Aerial Underwater Vehicle

This paper presents a low-cost variable buoyancy system (VBS) that can be integrated into Hybrid Aerial Underwater Vehicles (HAUVs). HAUVs are widely used in scientific research and must be lightweight and highly maneuverable to ensure sufficient endurance and operational reliability in underwater/air environments. To meet these key requirements, this study designs a low-cost and sustainable VBS that can adjust the attitude and depth of the HAUV during underwater operations. By redesigning the pipeline structure, the number of airbags, and their placement, internal gas self-circulation was achieved, thereby reducing costs. The PID controller based on depth and attitude information was further developed to ensure that the VBS operated more stably under complex underwater conditions. Field experiments on the application of the designed VBS on an HAUV based on a PID controller showed that the HAUV with the VBS could maintain the desired robot attitude and vertical speed and perform stable vertical movements.