## 1 Introduction  
As a treasure house of resources and a defense barrier, the importance of the ocean is very significant. With the development of society, the abundant resources contained in the vast ocean are also driving people to explore and utilize its value continuously. In terms of ocean exploration, the amphibious vehicle has more advantages in continuous observation and the obtaining of parameters, that is, being able to continuously observe both in the air and underwater. Compared to traditional single-medium vehicles, they significantly improve observation efficiency. In order to realize the continuous observation of the integration of sea and air and to utilize the characteristics of water and air media in special scenarios to complete specific tasks, it is necessary to develop specific navigation vehicles to meet these objectives. Research and application of traditional submarine and airplane vehicles have accumulated a considerable amount of history. The concept of the \"submersible aircraft\" with underwater navigation capabilities has been proposed for 70 years, which is also the origin of human exploration towards an HAUV [1]. The so-called HAUV [2] refers to a vehicle that combines the characteristics of aerial maneuvering flight and underwater concealed navigation. Different usage scenarios determine its unique functionality. And at the same time, due to this particularity, although research on HAUV has been ongoing for many years, it is still in its exploratory stage. The application characteristics of an HAUV determine its potential and wide application in marine-related military and civilian fields, with broad prospects [3]. It is known that the research process of HAUV is facing many difficulties. A full mission profile of a fully functional HAUV includes the stages of cruise in the air, water entry, underwater cruise and water exit. Among them, water entry and exit trans-media locomotion is the key process for an HAUV to realize the integration of water and air, which affects the continuity and integrity of the function of the HAUV in the whole mission profile and is also an unavoidable issue in the development process. There are several reasons for the difficulty in achieving a fully functional HAUV. Firstly, due to the significant differences in physical properties between air and water, designing an HAUV that meets both aerodynamic and hydrodynamic shape requirements is a huge challenge [2]. It is necessary to consider the process characteristics within the mission profile and the medium characteristics in the working environment comprehensively. Secondly, the mechanics in the trans-media process are very complicated; the wind and wave interference on the water surface, viscous damping, added mass, etc., are time-varying and uncertain, which makes the control problem of the HAUV, which originally integrates aerodynamics, hydrodynamics, flight control, underwater navigation and other disciplines, making it more complex [4]. To summarize, during the research process of the HAUV, it is necessary to consider the configuration design and the implementation method of trans-media. In this paper, the main discussion is on the overall configuration of the HAUV and flight-path angle controller for diving process, and a corresponding controller is designed. The contributions of this paper are as follows: (1) A variable-sweep HAUV configuration is proposed, and a specific mode of \"variable sweepback in the air + fixed configuration dive into water\" is designed, providing a foundation for further research on HAUVs and their trans-media locomotion control; (2) To ensure the stability of the HAUV in the process of air to water entry, a tracking controller for flight-path angle based on ADSC is designed. The remainder of this paper is organized as follows. In the second section, a variable-sweep HAUV configuration is proposed, and uncertain disturbance items are added to the traditional morphing-aircraft dynamics equation to simulate the real plunge-dive process as much as possible.