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Ornithopters are bird‐like flapping‐wing robots. Only small ornithopters can hover, with long endurance at hummingbird size. Could larger ornithopters be improved further to hover longer? This paper reviews and examines the drive and power of hovering ornithopters, and elastic means of energy or thrust boosters. While the rotation of flexible wings enhance the thrust generation, two‐winged ornithopters did not scale up well because of higher disk loading. In comparison, the X‐winged or multiple‐V‐winged ornithopters enjoy a lower disk loading by beating multiple wings slower, at a smaller stroke angle or a longer span. Further, the clap‐and‐fling interaction of V and X‐wings boosts the thrust generation. Future works can explore the wing flexibility and morphology change to improve the hoverability and flight agility of ornithopters. Only small ornithopters can hover, longest at the hummingbird size. This article reviews the drive and power of these hovering machines, focusing on elastic energy and thrust boosters. Unlike two‐winged designs, X‐winged and multiple‐V‐winged ornithopters benefit from lower disk loading and slower, smaller wingbeats, and the clap‐and‐fling effect.

Inspired by bird flight, flapping‐wing robots have gained significant attention due to their high maneuverability and energy efficiency. However, the development of their perception systems faces several challenges, mainly related to payload restrictions and the effects of flapping strokes on sensor data. The limited resources of lightweight onboard processors further constrain the online processing required for autonomous flight. Event cameras exhibit several properties suitable for ornithopter perception, such as low latency, robustness to motion blur, high dynamic range, and low power consumption. This article explores the use of event‐based vision for online processing onboard flapping‐wing robots. First, the suitability of event cameras under flight conditions is assessed through experimental tests. Second, the integration of event‐based vision systems onboard flapping‐wing robots is analyzed. Finally, the performance, accuracy, and computational cost of some widely used event‐based vision algorithms are experimentally evaluated when integrated into flapping‐wing robots flying in indoor and outdoor scenarios under different conditions. The results confirm the benefits and suitability of event‐based vision for online perception onboard ornithopters, paving the way for enhanced autonomy and safety in real‐world flight operations. A thorough analysis of event‐based vision for flapping‐wing robots is presented, with emphasis on hardware integration, suitability under challenging flight conditions, and real‐time performance. Theoretical and experimental studies demonstrate how these sensors enable robust and efficient onboard perception for ornithopters, thereby advancing autonomy and safety in both indoor and outdoor environments.

Wing design is a critical factor in the aerodynamic performance of flapping-wing (FW) robots. Inspired by the natural wing structures of insects, bats, and birds, we explored how bio-mimetic wing vein morphologies, combined with a bio-inspired double wing clap-and-fling mechanism, affect thrust generation. This study focused on increasing vertical force and payload capacity. Through systematic experimentation with various vein configurations and structural designs, we developed innovative wings optimized for thrust production. Comprehensive tests were conducted to measure aerodynamic forces, power consumption, and wing kinematics across a range of flapping frequencies. Additionally, wings with different aspect ratios, a key factor in wing design, were fabricated and extensively evaluated. The study also examined the role of bio-inspired vein layouts on wing flexibility, a critical component in improving flight efficiency. Our findings demonstrate that the newly developed wing design led to a 20% increase in thrust, achieving up to 30 g-force (gf). This research sheds light on the clap-and-fling effect and establishes a promising framework for bio-inspired wing design, offering significant improvements in both performance and payload capacity for FW robots.

Mechanism design and lift force calculation of an underactuated flapping wing robot with flexible planar wings are investigated in this paper. A spatial four-bar mechanism is introduced to realize flapping movements of wings, and then the emphasis contents of the paper are focused on lift force calculation of the robot system. A simple approach is presented for quantitatively calculating lift and thrust forces of the underactuated flapping wing system. Several robot prototypes have been fabricated on the basis of the optimization results with regard to a set of specific parameters. Some flight experiments show that the presented transmission mechanism and the optimization approach are feasible.

An optimized actuator for a flapping-wing robot was developed using detailed geometric and physical models to more closely mimic natural flapping dynamics. The robot’s actuator was reconfigured into a linked mechanism and analyzed through geometric equations. The pseudo-rigid-body model was employed to derive mechanical equations. Dual objectives were set for actuator optimization: minimizing both the maximum transmission angle and the potential energy of the flapping motion, subject to geometric and physical constraints. The optimization utilized the NSGA-II algorithm. Additionally, a virtual prototype with rigid-flexible coupling was created for simulation assessments pre- and post-optimization. Multi-objective optimization led to significant performance gains, including a 35.8% reduction in minimum potential energy, a 45.7% decrease in the standard deviation of the angular velocity, and a 10.0% improvement in the actuator angle’s range of angular variation at a flutter frequency of 4.5 Hz, all compared to a geometry-only baseline. These results suggest that the design provides enhanced stability and better replicates the natural dynamics of flapping flight.

Flapping-Wing Aerial Vehicles (FWAVs), which take inspiration from the flight of birds and insects, have gained increasing attention over the past decades due to advantages such as low noise, biomimicry and safety, enabled by the absence of propellers. These features make them particularly suitable for applications in natural environments and operations near humans. However, their complexity introduces significant challenges, including difficulties in take-off and landing as well as limited endurance. Perching represents a promising solution to address these limitations. By equipping these drones with a perching mechanism, they could land on branches to save energy and later exploit the altitude to resume flight without requiring human intervention. Specifically, this review focuses on perching mechanisms based on grasping. It presents designs developed for flapping-wing platforms and complements them with systems originally intended for other types of aerial robots, evaluating their applicability to FWAV applications. The purpose of this work is to provide a structured overview of the existing strategies to support the development of new, effective solutions that could enhance the use of FWAVs in real-world applications.

Flapping wing micro aerial vehicles (FWMAVs) are recognized for their significant potential in military and civilian applications, such as military reconnaissance, environmental monitoring, and disaster rescue. However, the lack of takeoff and landing capabilities, particularly in landing behavior, greatly limits their adaptability to the environment during tasks. In this paper, the purple stem beetle (Sagra femorata), a natural flying insect, was chosen as the bionic research object. The three-dimensional reconstruction models of the beetle’s three thoracic legs were established, and the adhesive mechanism of the thoracic leg was analyzed. Then, a series of bionic design elements were extracted. On this basis, a hook-pad cooperation bionic deployable landing mechanism was designed, and mechanism motion, mechanical performance, and vibration performance were studied. Finally, the bionic landing mechanism model can land stably on various contact surfaces. The results of this research guide the stable landing capability of FWMAVs in challenging environments.

Flapping-wing flying robots (FWFRs), especially large-scale robots, have unique advantages in flight efficiency, load capacity, and bionic hiding. Therefore, they have significant potential in environmental detection, disaster rescue, and anti-terrorism explosion monitoring. However, at present, most FWFRs are operated manually. Some have a certain autonomous ability limited to the cruise stage but not the complete flight cycle. These factors make an FWFR unable to give full play to the advantages of flapping-wing flight to perform autonomous flight tasks. This paper proposed an autonomous flight control method for FWFRs covering the complete process, including the takeoff, cruise, and landing stages. First, the flight characteristics of the mechanical structure of the robot are analyzed. Then, dedicated control strategies are designed following the different control requirements of the defined stages. Furthermore, a hybrid control law is presented by combining different control strategies and objectives. Finally, the proposed method and system are validated through outdoor flight experiments of the HIT-Hawk with a wingspan of 2.3 m, in which the control algorithm is integrated with an onboard embedded controller. The experimental results show that this robot can fly autonomously during the complete flight cycle. The mean value and root mean square (RMS) of the control error are less than 0.8409 and 3.054 m, respectively, when it flies around a circle in an annular area with a radius of 25 m and a width of 10 m.

This paper describes the development of a three-degrees-of-freedom flapping-wing robot with a variable-amplitude link mechanism for controlling the lift and thrust forces acting on it. The variable-amplitude link mechanism comprises a lever-crank mechanism driven by a brushless DC motor and a linear actuator to control the amplitude of the flapping angle. The robot also comprises two DC motors with reduction gears for feathering and lead-lag motion. In our experiments, the measurement of force-torque revealed the effects of the motion of each wing. We found that the flapping-amplitude difference between the left and right wings causes a roll and yaw moment.

Birds in nature exhibit excellent long-distance flight capabilities through formation flight, which could reduce energy consumption and improve flight efficiency. Inspired by the biological habits of birds, this paper proposes an autonomous formation flight control method for Large-sized Flapping-Wing Flying Robots (LFWFRs), which can enhance their search range and flight efficiency. First, the kinematics model for LFWFRs is established. Then, an autonomous flight controller based on this model is designed, which has multiple flight control modes, including attitude stabilization, course keeping, hovering, and so on. Second, a formation flight control method is proposed based on the leader–follower strategy and periodic characteristics of flapping-wing flight. The up and down fluctuation of the fuselage of each LFWFR during wing flapping is considered in the control algorithm to keep the relative distance, which overcomes the trajectory divergence caused by sensor delay and fuselage fluctuation. Third, typical formation flight modes are realized, including straight formation, circular formation, and switching formation. Finally, the outdoor formation flight experiment is carried out, and the proposed autonomous formation flight control method is verified in real environment.