The design of aerial-aquatic multirotors can benefit from thruster rotation so that the thrusters can act directly in the lateral directions of surge and sway when submerged. This allows much more effective locomotion underwater as opposed to the aerial configuration where rotational acceleration is used to direct small components of thrust in the lateral directions. However, the introduction of lateral thruster components by rotating the thrusters about their respective arm axes creates additional coupled moment terms. Here, the dynamics of this design is analysed to show that critical angles of thruster rotation can achieve stable surge and sway movements while also decoupling lateral from rotational movements.

Hybrid aerial-aquatic vehicles have the unique ability of travelling in both air and water and can benefit from both lower fluid resistance in air and energy efficient position holding in water. However, they have to address the differing requirements which make optimising a single design difficult. While existing examples have shown the possibility of such vehicles, they are mostly structurally identical to normal aerial vehicles with minor adjustments to work underwater. Instead of using rotational acceleration to direct a component of thrust in surge and sway, we propose a quadrotor based vehicle that tilts its rotors about the respective arm so that a larger component of thrust can be directed in the lateral plane or in the opposite direction without rotating the vehicle body. A small-scale prototype of this design is presented here, detailing the design considerations including mechanical actuation, static stability and waterproofing.

Electric aerial propulsion systems are commonly used for many small-scale unmanned aerial vehicles (UAVs), providing a light and powerful method of generating thrust. In the emerging area of aerial-aquatic vehicles, most existing prototypes rely on such systems to propel themselves in both air and water. As the density of water is three orders of magnitude larger than that of air, a spinning aerodynamic body in the medium will experience significantly higher torque at the same speed. This results in aerial propulsion systems to be heavily mismatched underwater, as the required torque is higher than the drive torque that a typical aerial motor can provide. Here, an in-depth investigation of such off-design operation is conducted. Based on numerical simulation, we identify the feasible operating range of such systems and present an evaluation framework that identifies a motor-propeller combination from a component database that maximises underwater performance while ensuring aerial thrust requirements are met.

In this paper, we implement a real-time method for incrementally stitching aerial images over a large area. To collect high-quality aerial images, the camera is mounted on a gimbal. Being isolated from the vibration of the drone, the camera can provide relatively stable and less blurry images. To achieve fast aerial mapping, instead of using traditional feature extraction and matching steps, this algorithm only relies on camera position and orientation for blending. The mosaic is fused and incrementally updated based on the adaptive weight multi-band blending algorithm. The weight matrix and Laplacian pyramid for blending are updated adaptively. The orthoimage can be reconstructed from the Laplacian pyramid incrementally. This method was applied in the aerial mapping task of the ninth International Micro Air Vehicle Conference and Flight Competition, achieving a high quality map that contributed to the team's championship in the outdoor competition.