Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> VII. DISCUSSION AND FINAL REMARKS <s> This paper presents an experimental study on the development of a cyclogyro-based flying robot with a new variable angle of attack mechanism. A cyclogyro is a flying machine supported in the air by power-driven rotors that rotate about a horizontal axis, like the paddle-wheels of a steamboat. Machines of this type have been designed by some companies but there has been no record of any successful flights. Our design starts with a new variable angle of attack mechanism with an eccentric (rotational) point in addition to a rotational point connecting to a motor. The main feature of the mechanism with the eccentric rotational point is the ability to change attack of angles in accordance with the wing positions (as determined by the rotational angles of the cyclogyro) without actuators. The design parameters (wing span, the number of wings, and eccentric distance) of the flying robot are determined through a series of experiments. Experimental results show that the cyclogyro-based flying robot with the new variable angle of attack mechanism is capable of generating sufficient lift force for flying. <s> BIB001 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> VII. DISCUSSION AND FINAL REMARKS <s> We develop a flying robot with a new pantograph-based variable wing mechanism for horizontal-axis rotorcrafts (cyclogyro rotorcrafts). A key feature of the new mechanism is to have a unique trajectory of variable wings that not only change angles of attack but also expand and contract according to wing positions. As a first step, this paper focuses on demonstrating the possibility of the flying robot with this mechanism. After addressing the pantograph-based variable wing mechanism and its features, a simulation model of this mechanism is constructed. Next, we present some comparison results (between the simulation model and experimental data) for a prototype body with the proposed pantograph-based variable wing mechanism. Both simulation and experimental results show that the flying robot with this new mechanism can generate enough lift forces to keep itself in the air. Furthermore, we construct a more precise simulation model by considering rotational motion of each wing. As a result of optimizing design parameters using the precise simulation model, flight performance experimental results demonstrate that the robot with the optimal design parameters can generate not only enough lift forces but a 155 gf payload as well. <s> BIB002 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> VII. DISCUSSION AND FINAL REMARKS <s> The kite mechanics including some basic aerodynamics is reviewed in order to set up a framework for the development of robotic kite systems. Some historical background is provided together with a brief review of kite applications, which have been numerous and diverse. Robotizing the kite is expected to enhance its capabilities and revive scientific kiting. Towards that direction a methodology for controlling the angular elevation (and the altitude) of a single-line kite by actively adjusting the length of its bridle strings is proposed together with the required implementation hardware. Preliminary simulations and proof-of-concept field testing using a box kite were carried out. <s> BIB003 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> VII. DISCUSSION AND FINAL REMARKS <s> In this article we present a mathematical model of a spincopter - an inherently stable and easy to control unmanned aerial vehicle (UAV). Although the devised model represents only the first approximation of spincopter's physics, it captures basic phenomena that are sufficient for derivation and testing of a simple control algorithm. Results obtained by simulations in Simulink®, presented herein, demonstrate efficient performance of the proposed simple controller structure. Further tests, including investigation of complex aerodynamics effects and hardware-specified limitations, have been done using X-Plane® software package. Finally, the proposed controller has been tested experimentally. Both, X-Plane® and experimental results confirmed the outcome from Simulink®. <s> BIB004 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> VII. DISCUSSION AND FINAL REMARKS <s> In this work, we present a flying saucer, a kind of unmanned aerial vehicle(UAV), lifted based on Coandă effect. Coandă effect is an interesting fluid dynamic phenomenon that the interaction between the flow and curved surfaces produce attraction, which results in the lifting of the object. The flying saucer adopting Coandă effect is easy to hover while keeping its posture stable, and vertical take-off and landing(VTOL) is possible. Its design procedures via optimization and manufacturing procedures are explained in details, and the preliminary tests in the indoor and outdoor are successfully demonstrated. <s> BIB005 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> VII. DISCUSSION AND FINAL REMARKS <s> Aerial cargo delivery, also known as airdrop, systems are heavily affected by atmospheric wind conditions. Guided airdrop systems typically employ onboard wind velocity estimation methods to predict the wind in real time as the systems descend, but these methods provide no foresight of the winds near the ground. Unexpected ground winds can result in large errors in landing location, and they can even lead to damage or complete loss of the cargo if the system impacts the ground while traveling downwind. This paper reports on a ground-based mechatronic system consisting of a cup and vane anemometer coupled to a guided airdrop system through a wireless transceiver. The guidance logic running on the airdrop system's onboard autopilot is modified to integrate the anemometer measurements at ground level near the intended landing zone with onboard wind estimates to provide an improved, real-time estimate of the wind profile. The concept was first developed in the framework of a rigorous simulation model and then validated in the flight test. Both simulation and subsequent flight tests with the prototype system demonstrate reductions in the landing position error by more than 30% as well as a complete elimination of potentially dangerous downwind landings. <s> BIB006 </s> Recent Developments in Aerial Robotics: A Survey and Prototypes Overview <s> VII. DISCUSSION AND FINAL REMARKS <s> This paper presents the “monospinner”: a mechanically simple flying vehicle with only one moving part. The vehicle is shown to be controllable in three translational degrees of freedom and two rotational degrees of freedom. The vehicle has a single scalar control input, the thrust magnitude, and is controlled by a cascaded control strategy with an inner attitude controller and an outer position controller. The vehicle design is chosen based on two robustness metrics: the ability to maintain hover under perturbations and the probability of input saturation based on a stochastic model. The resulting mechanical and control designs are experimentally demonstrated, where it is also shown that the vehicle is sufficiently robust to achieve hover after being thrown into the air. <s> BIB007
While we have covered and selected more than one thousand UAV papers in several top journals and conferences since (Fig. (a)-(b) ) BIB001 , BIB002 , spincopters (Fig. (c)-(d) ) BIB004 , BIB007 , Coandǎ UAV (Fig.  (e) ) BIB005 , parafoil UAV (Fig. (f) ) BIB006 , and kite UAV (Fig. (g) ) BIB003 appear in the reviewed papers. See text for details. 2001, we focused on the robotic communities (TRO, TME, IJRR, RAS, IROS, ICRA, HRI, ROMAN). To extend the survey, we could expand into journals/conferences in the aerospace and aeronautics communities, such as International Journal of Robust and Nonlinear Control [134] , Journal of Guidance, Control, and Dynamics [135] , and International Conference on Unmanned Aircraft Systems  . UAVs from the commercial sectors would also provide fertile ground. To name a few, the DJI Phantom 4 [137] and YUNEEC Typhoon H [138] ) appear to possess advanced path planning, human tracking, and obstacle avoidance algorithms. However, private companies often do not provide detailed technical information to the public. In the Part II of this survey, we cover the trends in aerial robotics by discussing three emerging topics-(i) holonomic UAVs, a special type of UAV that can perform horizontal motions while maintaining orientation; (ii) localization and mapping with UAV; and (iii) human-drone interaction. APPENDIX A ADDITIONAL SURVEY RESULTS Figure 14 and Fig. 15 show a pie chart and a map of the country distribution of UAV papers. In descending order, the top ten countries with the most drone papers since 2001 are United States of America, Switzerland, France, Australia, Germany, Japan, Spain, China, Italy, and South Korea. Other countries in the pie chart include Canada, Mexico, Venezuela, Brazil, United Kingdom, Portugal, Netherlands, Belgium, Austria, Czech Republic, Croatia, Hungary, Slovakia, Sweden, Finland, Denmark, Greece, Cyprus, South Africa, United Arab Emirates, Iran, Israel, Saudi Arabia, Turkey, India, Taiwan, Philippines, Malaysia, and Singapore. Figure 16 shows that the number of papers that use motion capture system increases rapidly since 2009. Motion capture system is a system that relies on multiple high-speed cameras to record the movement of reflective markers attached on the UAV in real time. The system offers sub-millimeter position accuracy measurement and is useful in various drone researches, such as topics related to positioning control and visual localization. In term of occurrence (reputation) in descending order, the top widely used commercial system are Vicon [139] , OptiTrack [140] , Qualisys [141] , MotionAnalysis [142] , PTI Phoenix [143] , Advanced Realtime Tracking (ART)  , NaturalPoint [145] , and Leica [146] . 