Autonomous flight control with different strategies applied during the complete flight cycle for flapping-wing flying robots

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.

Bird-mimetic Wing System of Flapping-wing Micro Air Vehicle with Autonomous Flight Control Capability

A micro air vehicle with a bird-mimetic up-down and twisting wing drive system was developed in this study. The Flap- ping-wing Micro Air Vehicle （FMAV）, with a 50 cm wingspan and a double-crank drive system, performed successful flights of up to 23 min. The performance and capabilities of the FMAV were enhanced by adapting a number of unique features, such as a bird-mimetic wing shape with a span-wise camber and an up-down and twisting wing drive mechanism with double-crank linkages, This lift-enhancing design by mimicking the flapping mechanism of a bird＇s wing enabled the 210 g FMAV to fly autonomously in an outdoor field under wind speeds of less than 5 m.s-1. Autonomous flight was enabled by installing a flight control computer with a micro-electro-mechanical gyroscope and accelerometers, along with a micro video camera and an ultralight wireless communication system inside the fuselage. A comprehensive wind tunnel test shows that the FMAV with a high-camber wing and double-crank mechanism generates more lift and less net thrust than the FMAV with a flat wing and single-crank mechanism, which confirms the improved performance of the developed FMAV, as well as the superior slow flying or hovering capabilities of the FMAV with a high-camber wing and double-crank wing drive system.

A Potential Flow Based Flight Simulator for an Underwater Glider

Underwater gliders are recent innovative types of autonomous underwater vehicles （AUVs） used in ocean exploration and observation. They adjust their buoyancy to dive and to return to the ocean surface. During the change of altitude, they use the hydrodynamic forces developed by their wings to move forward. Their flights are controlled by changing the position of their centers of gravity and their buoyancy to adjust their trim and heel angles. For better flight control, the understanding of the hydrodynamic behavior and the flight mechanics of the underwater glider is necessary. A 6-DOF motion simulator is coupled with an unsteady potential flow model for this purpose. In some specific cases, the numerical study demonstrates that an inappropriate stabilizer dimension can cause counter-steering behavior. The simulator can be used to improve the automatic flight control. It can also be used for the hydrodynamic design optimization of the devices.

Design and Control of an Autonomous Bat-like Perching UAV

Perching allows small Unmanned Aerial Vehicles(UAVs)to maintain their altitude while significantly extending their flight duration and reducing noise.However,current research on flying habitats is poorly adapted to unstructured environments,and lacks autonomous capabilities,requiring ideal experimental environments and remote control by personnel.To solve these problems,in this paper,we propose a bat-like UAV perching mechanism by investigating the bat upside-down perching method,which realizes double self-locking in the perching state using the ratchet and four-link dead point mechanisms.Based on this perching mechanism,this study proposes a control strategy for UAVs to track targets and accomplish flight perching autonomously by combining a binocular camera,single-point LiDAR,and pressure sensors.Autonomous perching experiments were conducted for crossbar-type objects outdoors.The experimental results show that a multirotor UAV equipped with the perching mechanism and sensors can reliably achieve autonomous flight perching and re-flying off the target outdoors.The power consumption is reduced to 2.9%of the hovering state when perched on the target object.

Flight control of a large-scale flapping-wing flying robotic bird:System development and flight experiment

Large-scale flapping-wing flying robotic birds have huge application potential in outdoor tasks,such as military reconnaissance,environment exploring,disaster rescue and so on.In this paper,a multiple modes flight control method and system are proposed for a large-scale robotic bird which has 2.3 m wingspan and 650 g mass.Different from small flapping wing aerial vehicle,the mass of its wings cannot be neglected and the flapping frequency are much lower.Therefore,the influence of transient aerodynamics instead of only mean value are considered in attitude estimation and controller design.Moreover,flight attitude and trajectory are highly coupled,and the robot has only three actuators----one for wings flapping and two for tail adjustment,it is very difficult to simultaneously control the attitude and position.Hence,a fuzzy control strategy is addressed to determine the command of each actuator by considering the priority of attitude stabilization,trajectory tracking and the flight safety.Then,the on-board controller is designed based on FreeRTOS.It not only satisfies the strict restrictions on mass,size,power and space but also meets the autonomous,semi-autonomous and manual flight control requirements.Finally,the developed control system was integrated to the robotic prototype,HIT-phoenix.Flight experiments under different environment conditions such as sunny and windy weather were completed to verify the control method and system.

Trajectory tracking control of a VTOL unmanned aerial vehicle using offset-free tracking MPC

Designing a stable and robust flight control system for an Unmanned Aerial Vehicle(UAV)is an arduous task.This paper addresses the trajectory tracking control problem of a Ducted Fan UAV(DFUAV)using offset-free Model Predictive Control(MPC)technique in the presence of various uncertainties and external disturbances.The designed strategy aims to ensure adequate flight robustness and stability while overcoming the effects of time delays,parametric uncertainties,and disturbances.The six degrees of freedom DFUAV model is divided into three flight modes based on its airspeed,namely the hover,transition,and cruise mode.The Dryden wind turbulence is applied to the DFUAV in the linear and angular velocity component.Moreover,different uncertainties such as parametric,time delays in state and input,are introduced in translational and rotational components.From the previous work,the Linear Quadratic Tracker with Integrator(LQTI)is used for comparison to corroborate the performance of the designed controller.Simulations are computed to investigate the control performance for the aforementioned modes and different flight phases including the autonomous flight to validate the performance of the designed strategy.Finally,discussions are provided to demonstrate the effectiveness of the given methodology.