Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> We aim at developing autonomous micro-flyers capable of navigating within houses or small built environments. The severe weight and energy constraints of indoor flying platforms led us to take inspiration from flying insects for the selection of sensors, signal processing, and behaviors. This paper presents the control strategies enabling obstacle avoidance and altitude control using only optic flow and gyroscopic information. For experimental convenience, the control strategies are first implemented and tested separately on a small wheeled robot featuring the same hardware as the targeted aircraft. The obstacle avoidance system is then transferred to a 30-gram aircraft, which demonstrates autonomous steering within a square textured arena. <s> BIB001 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> This paper presents and compares two different approaches to integrating sensor information from an Inertial Measuring Unit (IMU), Global Positioning System (GPS) receiver and monocular vision camera mounted to a low-flying Unmanned Aerial Vehicle (UAV) for building large-scale 3D terrain reconstructions. Both approaches utilise a statistically optimal bundle adjustment formulation that incorporates Vision, IMU and GPS observations into the map and pose optimisation process. Our first approach employs a novel pose-only formulation that optimises relative camera poses based on vision feature matches between frames, while incorporating IMU and GPS information. Our approach is related to, but differs from existing pose-graph techniques by formulating a set of 1D epipolar constraints for features matched between two camera frames, rather than minimising 4D feature re-projection errors, or marginalising feature states. We compare results of the method to a second approach which estimates both 3D features and poses together, using airborne vision, IMU and GPS data collected in an ecology mapping application. The results demonstrate a reduction in the computational complexity during optimisation for the pose-only approach, while producing equivalent accuracy in the reconstructed 3D terrain map. <s> BIB002 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> In this article, the design, system modeling and control of a new hybrid type of Unmanned Aerial Vehicle (UAV) is presented. Based on the flight principles of the Dos Samara UAV, a new vehicle that combines the capability of hovering, like a helicopter, and high speed-increased endurance flying, like a fixed-wing aircraft, is designed. The nonlinear dynamics model of the aircraft operating in helicopter mode is derived and linearized around hovering operation. Based on this model an LQ-controller is designed. The performance of the overall system is examined in simulation studies. <s> BIB003 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> Most existing robots are designed to exploit only one single locomotion mode, such as rolling, walking, flying, swimming, or jumping, which limits their flexibility and adaptability to different environments where specific and different locomotion capabilities could be more effective. Here we introduce the concept and the design of a flying robot with Adaptive Morphology for Multi-Modal Locomotion. We present a prototype that can use its wings to walk on the ground and fly forward. The wings are used as whegs to move on rough terrains. This solution allows to minimize the structural mass of the robot by reusing the same structure (here the wings) for different modes of locomotion. Furthermore, the morphology of the robot is analysed and optimized for ground speed. <s> BIB004 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> This paper presents a novel approach for constructing light-weight, low-cost air-deployable sensor modules and miniature unmanned aerial vehicles which consist of printed circuit boards as integrated electronic, structural and aerodynamic lift-producing devices. In this way, each aircraft can be a single-piece, single-manufacturing step assembly, reducing materials, processing and labour costs. This approach allows the fabrication of devices that are sufficiently inexpensive so as to be economic for single-use or disposable applications, such as long-range sensor deployment for environmental monitoring. We present two example low-cost, proof-of-concept aircraft employing electro-aeromechanical structures - rotary-wing and fixed-wing - and demonstrate their flight performance. <s> BIB005 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> The stability and control derivatives of an unmanned aerial vehicle (UAV) map the platform's control inputs to its dynamic response. The modeling is labor intensive and requires coarse approximations. Similarly, models constructed through flight tests are only applicable to a narrow flight envelope, and classical system identification approaches require prior knowledge of the model structure, which, in some instances, may only be partially known. The goal of this study is to tackle these problems by introducing a new system identification method based on the dependent Gaussian processes. This allows high-fidelity nonlinear flight dynamic models to be constructed through experimental data. The proposed algorithm captures the cross coupling between input parameters and learns the system stability and control derivatives. In addition, it captures any dependences embodied in the outputs. This paper provides both the theoretical underpinnings and practical application of this approach. The theory was tested in simulation on a highly coupled oblique wing aircraft and was demonstrated on a delta-wing UAV platform using real flight data. The results are compared against an alternative parameteric model and show improvements in identifying the coupling between flight modes, the ability to provide uncertainty estimates and robustness, and applicability to a broader flight envelope. <s> BIB006 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> We present the design and implementation of a small Vertical-Take-Off-and-Landing (VTOL) aircraft. The vehicle requires minimal additional components to achieve the hover capability and is thus very efficient in forward flight. We improve over the state of the art by using a single controller in all flight modes without using blending between hover condition and fixed wing controllers or gain scheduling. We present a compact airflow estimation model for VTOL airframes which rely on the slipstream across control surfaces for hover attitude control. Furthermore we show attitude and position control results in simulation. Finally we show outdoor flight experiments validating our simulation results. <s> BIB007 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> Unmanned solar powered aircraft offer a unique set of advanced capabilities and have set general aviation records for longest continuous flight and greatest sustained altitude. However, the application of solar powered flight to small scale solar powered unmanned aerial vehicles (UAVs) has seen sparse research activity and is only partially explored. The use of solar power as an energy resource allows small scale UAVs to carry heavier, more powerful sensor payloads, and can extend flight times to over 24 hours, thereby achieving multi-day flight. This work focuses on recent developments by the Center for Distributed Robotics on a four meter wingspan solar UAV designed for low altitude aerial sensing applications. Highlighted in this paper are aspects of airframe, propulsion, and electronics hardware design as well as experiments that quantify the solar power system and airframe performance. <s> BIB008 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> This paper addresses the challenges of the design, development and control of a new convertible VTOL tailsitter unmanned aerial vehicle that combines the advantages of both fixed wing and rotary wing systems. Wind tunnel measurements are used to get an understanding of the control allocation and to model the static forces and moments acting on the system. Based on the derived model, a novel controller that operates in SO(3) and handles the dynamics of the vehicle at any attitude configuration, including the rotorcraft and fixed-wing regimes as well as their transitions, is presented. This unified controller allows the autonomous transition of the system without discontinuities of switching, as well as its overall high performance flight control. The capabilities and flying qualities of the platform and the controller are demonstrated and evaluated by means of extensive experimental studies. <s> BIB009 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> C. Fixed-wing UAVs <s> Throughout the wide range of aerial robot related applications, selecting a particular airframe is often a trade-off. Fixed-wing small-scale unmanned aerial vehicles (UAVs) typically have difficulty surveying at low altitudes while quadrotor UAVs, having more maneuverability, suffer from limited flight time. Recent prior work [1] proposes a solar-powered small-scale aerial vehicle designed to transform between fixed-wing and quad-rotor configurations. Surplus energy collected and stored while in a fixed-wing configuration is utilized while in a quad-rotor configuration. This paper presents an improvement to the robot's design in [1] by pursuing a modular airframe, an optimization of the hybrid propulsion system, and solar power electronics. Two prototypes of the robot have been fabricated for independent testing of the airframe in fixed-wing and quad-rotor states. Validation of the solar power electronics and hybrid propulsion system designs were demonstrated through a combination of simulation and empirical data from prototype hardware. <s> BIB010
A fixed-wing UAV (Fig. 9 (a)-(k) ) BIB007 ,  , BIB004 , BIB005 , BIB002 - BIB001 , also known as airplane, aeroplane, or simply a plane, is one of the most common aircrafts in the aviation history. Compared to a multi-rotor aircraft, a fixed-wing UAV generally has higher flight safety (still able to glide for a long time after engines break down in the air) and longer flight time (much more energy-efficient). Figure 9 (a)-(c) show three typical fixed-wing UAVs. Bryson and Sukkarieh BIB002 demonstrate a mapping application with their fixed-wing UAV by integrating information from an IMU sensor, a GPS sensor, and a downwardfacing monocular camera ( Fig. 9 (a) ). Hemakumara and Sukkarieh BIB006 focus on system identification topic and aim to learn the complex dynamic model of their fixed-wing UAV by using Gaussian processes (Fig. 9 (b) ). Morton et al. BIB008 focus on hardware development, where they detail the design and developments of their solar-powered and fixed-wing UAV (Fig. 9 (c) ). Compared to a multi-rotor UAV, a conventional fixed-wing UAV is more energy efficient during cruise flight but does not have the hovering capability, in which a fixed-wing UAV cannot maintains its position in the air and requires more space for take-off and landing. Bapst et al. BIB007 aim to combine the merits of both types of UAVs, where they present their design, modeling, and control of a UAV that could vertically take-off and land (VTOL) like a multi-rotor UAV and perform cruise flight like a fixed-wing UAV (Fig. 9 (d) ). Verling et al. BIB009 present another design of this type of hybrid fixed-wing UAV based on a new modeling and controller approach, where they focus on the smooth and autonomous transition between the VTOL mode and cruise mode (Fig. 9 (e) ). Researchers have also explored topics on fixed-wing UAVs with transformable shapes. Daler et al. BIB004 build a fixed-wing UAV that could fly in the air and walk on the ground by rotating its wings ( Fig. 9 (f) ). D'Sa et al. BIB010 present a UAV that could fly in a fixed-wing configuration and perform VTOL in a quadcopter configuration (Fig. 9 (g) ). Alexis and Tzes BIB003 present a hybrid UAV, where the UAV could perform cruise flight like a fixed-wing UAV and perform hovering flight like a bicopter (Fig. 9 (h) ). Their key design lies on the hybrid wings/propellers' structures: in the fixed-wing configuration, the one-blade structures are fixed at the right positions and act as wings; in the bicopter configuration, the one-blade structures rotate and act as propellers. Papachristos et al.  develop another type of hybrid UAV, where the UAV could perform cruise flight like a fixed-wing UAV and perform hovering flight like a tricopter (Fig. 9 (i) ). Several palm-sized fixed-wing UAVs have also been designed by researchers. Zufferey and Floreano BIB001 design a small fixed-wing UAV that has only 30 grams and capable of navigating autonomously at an indoor environment (Fig. 9 (j) ). Despite its small size, the 30-gram fixed-wing UAV can also avoid obstacle during flight by relying on optical flow techinique. Pounds and Singh BIB005 present a novel and low-cost fixed-wing UAV by integrating electronics and lift-producing devices onto a paper aeroplane (Fig. 9 (k) ).