# Development of an Autonomous Underwater Helicopter with High Maneuverability
## 6 Conclusions  
In this paper, the AUH, a new type of disc-shaped AUV for seabed-to-seabed operating modes, is proposed. It has the characteristics of maneuverability and vertical motion stability. The prototype was built, and several groups of experiments were carried out on it. Based on this, we draw the following conclusions:  
1. Because the special disc shape has the characteristics of horizontal in-plane isotropy, large vertical resistance, and small horizontal resistance, there is no need for over-actuation to achieve stable motion with high maneuverability within acceptable limits. It is feasible to increase endurance by reducing the number of propellers.
2. At least four propellers are necessary for maneuverability of the AUH. The pitch vibration in the horizontal linear motion experiment is consistent with the prediction of dynamic analysis. To eliminate the harmful resistance and angle of attack caused by this vibration, a set of propellers that can provide an active recovery moment is required. Together with at least two propellers needed to complete the plane motion, four propellers in two groups are necessary for AUH to complete the stable motion of high maneuverability.  
Figure 16: The vertical lifting motion and landing experiment. (**a**) AUH was near the surface of the water; (**b**) AUH began to sink; (**c**) AUH continued to sink; (**d**) AUH landed at the bottom of the pool; (**e**) the pitch angle and roll angle of AUH during the experiment.  
3. The prototype of the AUH has the potential for high maneuverability. It has the potential to cruise in a small area flexibly, land on the seabed and take off. It is indicated that the AUH may be a solution for increasingly complex undersea engineering tasks, especially near-seabed operations.  
At present, although the AUH has the potential for high maneuverability, only a simple quadrangle path test has been carried out, due to the lack of a high-accuracy positioning system and navigation system. Next, we will try to set up a more complex running path for the AUH in conjunction with the positioning and navigation system to further demonstrate its excellent maneuverability. In addition, with the high-accuracy positioning system, we will be able to more intuitively compare the performance of other submersibles, including torpedo-type submersibles, to further verify the advantages of the high maneuverability of the disc-shaped AUH. In addition, it is expected to carry working modules such as manipulators and to break through the problem that AUVs cannot carry out near-seabed engineering operations.  
The work described in this article is the collaborative development of all authors. Conceptualization, Y.C. and H.H.; methodology, Z.W.; investigation, Y.C. and H.H.; experiments performance, Z.W. and X.L.; data curation, X.L.; supervision, H.H.; writing--original draft preparation, Z.W.; writing--review and editing, H.H. and Y.C.  
The study was supported financially by the National Key R&D Program of China (NO. 2017 YFC0306100).  
The authors would like to thank [PERSON], [PERSON], and other staff of Ocean College, Zhejiang University for making the prototype and performing the experiments.  
The authors declare no conflict of interest.