Unmanned Aerial Vehicles (UAVs) autonomous approaching and landing on mobile platforms always play an important role in various application scenarios. Such a complicated autonomous task requires an integrated multi-sensor system to guarantee environmental adaptability in contrast to using each sensor individually. Multi-sensor fusion perception demonstrates great feasibility to compensate for adverse visual events, undesired vibrations of inertia sensors, and satellite positioning loss. In this paper, a UAV autonomous landing scheme based on multi-sensor fusion is proposed. In particular, Ultra Wide-Band (UWB) sensor, Inertial Measurement Unit (IMU), and vision feedback are integrated to guide the UAV to approach and land on a moving object. In the approaching stage, a UWB-IMU-based sensor fusion algorithm is proposed to provide relative position estimation of vehicles with real time and high consistency. Such a sensor integration addresses the open challenge of inaccurate satellite positioning when the UAV is near the ground. It can also be extended to satellite-denied environmental applications. When the landing platform is detected by the onboard camera, the UAV performs autonomous landing. In the landing stage, the vision sensor is involved. With the visual feedback, a deep-learning-based detector and local pose estimator are enabled when the UAV approaches the landing platform. To validate the feasibility of the proposed autonomous landing scheme, both simulation and real-world experiments in extensive scenes are performed. As a result, the proposed landing scheme can land successfully with adequate accuracy in most common scenarios.

To improve the crashworthiness of civil aircraft, the design concept of energy absorption structure for civil aircraft is investigated. Two typical different design principles could be identified. The first category includes Helicopter and Light fixed-wing Aircraft (HLA), and Transport, Mid-size and Commuter type Aircraft (TMCA) are classified into the second group. Frame, strut and bottom structure are the three kinds of energy absorption structure for TMCA. The strut layout of conventional civil aircraft is studied and some energy absorption devices are adopted. High efficiency energy absorption structures such as the foam and sine-wave beam are employed as the bottom structure for both of HLA and LMCA. The finite element method is used to analyse and design energy absorption structure in aircraft crashworthiness problem. Results show that the crashworthiness of civil aircraft could be largely improved by using proper strut layout and excellent energy absorption device. The stiffness combination of frame and strut should be considered to get better global aircraft deformation. Supporting platform and failure model are the two core problems of bottom energy absorption structure design. Foam and sine-wave beam under the lifted frame could improve the crashworthiness of civil aircraft.

Micro tandem bi-copters are capable of passing through narrow gaps owing to their particular slender shape. However, the introduction of the tilting servo motors leads to a non-minimum phase roll dynamics, which affects their flight stability when exploring environments with unpredictable disturbances. In this letter, we propose and design a re-configurable aerial platform consisting of two modular bi-copters with an undocking mechanism. In combined configuration, a crossover docking approach is employed to compensate for the poor stability in their servo-controlled attitude of each bi-copter. In bi-copter configuration, the minimum size (equal to ideal passable gap's width) of the system was reduced by 58% through mid-air separation. In detail, to compare the attitude response of the two configurations, a dynamic model considering servo response and non-minimum phase is established and simulated, and flying poking experiments were also conducted on them respectively. On the other hand, the performance of single bi-copter including trajectory tracking and passing through narrow gaps was demonstrated through flight tests. Finally, the feasibility of the undocking mechanism was verified by mid-air separation experiments. The proposed system is promising to be applied in scenarios containing both complex perturbations and confined spaces, while also having the potential to improve exploration efficiency through collaborative work.