Nezha-T: a Bi-floating State Lightweight Tail-sitter HAUV

Abstract

Hybrid aerial-underwater vehicles (HAUVs) are attracting significant interest for their unique capability to operate across both air and water. However, achieving a lightweight design coupled with efficient cross-domain performance remains a formidable challenge. This paper introduces Nezha-T, a novel, ultra-lightweight HAUV featuring a dual-stable floating state capability. This is achieved through an innovative center-of-gravity (CoG) arrangement method, which enables seamless transitions between upright and horizontal floating postures. This ability to stably floating in either orientation is crucial for stable water entry and exit, mitigating impact forces on the vehicle and its payload. Furthermore, to counteract the residual buoyancy inherent in this design, a zero-lift pitch angle is incorporated into the control system, improving depth-keeping and pitch control performance. The proposed design were rigorously validated through computational fluid dynamics (CFD) simulations, pool experiments, and open-water field tests. The results confirm the feasibility of the dual-stable floating states, demonstrate stable cross-domain traversal, verify the effectiveness of the depth-keeping control system, and validate the vehicle’s fixed-wing flight capability.