Nezha-F: Design and Analysis of a Foldable and Self-Deployable HAUV

This letter introduces a small hybrid aerial underwater vehicle (HAUV), which we named Nezha-F, that can fly in the air, perform vertical profiling underwater, and vertically take off and land from both the water surface and ground. A foldable and self-deployable arm mechanism linked to and driven by a piston variable buoyancy system (PVBS) is proposed to reduce the excessive underwater drag caused by aerial structures. By having a compact size and successfully balanced aerial and underwater performance without adding excessive actuators, this design provides a feasible idea for the miniaturization of amphibious floats. The dynamic characteristics of the small PVBS are linear fitted, and modeled. The originally nonlinear actuator performance is linearized by the post-fitting mapping. Asymmetric dead zones of the actuator are removed by adding compensation to the algorithm. During a 10-day field test, the vehicle showed good aerial performance and underwater control effect. Several full mission cycle tests proved the vehicle's ability in semi-autonomous operation and robust domain crossing and verified the vehicle's endurance during each mission stage.