Flapping-wing Robot Research Articles

A Low Mass Power Electronics Unit to Drive Piezoelectric Actuators for Flying Microrobots

This paper presents a power electronics design for the piezoelectric actuators of an insect-scale flapping-wing robot, the RoboBee. The proposed design outputs four high-voltage drive signals tailored for the two bimorph actuators of the RoboBee in an alternating drive configuration. It utilizes fully integrated drive stage circuits with a novel highside gate driver to save chip area and meet the strict mass constraint of the RoboBee. Compared with previous integrated designs, it also boosts efficiency in delivering energy to the actuators and recovering unused energy by applying three power saving techniques, dynamic common mode adjustment, envelope tracking, and charge sharing. Using this design to energize four 15 nF capacitor loads with a 200 V and 100 Hz drive signal and tracking the control commands recorded from an actual flight experiment for the robot, we measure an average power consumption of 290 mW.

Monolithic fabrication of an insect‐scale self‐lifting flapping‐wing robot

Robots on the order of insect-scale are difficult to manufacture using MEMS technologies for sub-millimetre structures or conventional methods for large devices beyond centimetres. This work presents an electromagnetically driven, monolithically fabricated, insect-scale self-lifting flapping-wing robot for the first time. This robot is created using a simple monolithic method, by which most of the components are integrated and fabricated from a single sheet. Finally, the monolithic insect-scale flapping-wing robot can generate sufficient lift to take off.

Aeromechanic Models for Flapping-Wing Robots With Passive Hinges in the Presence of Frontal Winds

Following the emergence of small flight-capable flapping-wing micro air vehicles, efforts toward autonomous outdoor operations of these small robots outside controlled laboratory conditions have been made. For the robots to overcome wind disturbances, it necessitates better insights into the interaction between the aerodynamics of flapping wings in the presence of winds and the robot's actuation system. In this paper, we consider the effects of constant frontal wind on a direct-drive flapping wing robot with passively rotating hinges and a compliant transmission. A simplified quasi-steady model that encapsulates the effects of frontal wind on aerodynamic forces is proposed. The model facilitates the calculation of periodic aerodynamic forces from nominal flapping kinematics. When combined with the dynamics of the actuation system, we are able to predict the lift force generated by the robot from the driving signals, without direct measurements of the flapping kinematics or the angle of attack. The proposed framework was experimentally verified on a flapping-wing robot prototype with a single wingspan of 76 mm. The results reveal up to 40% increases in lift when the robot was subject to 2.5 m/s horizontal winds. An analysis of the frequency response of the system is also provided to explain the resonance principles of the robot in the presence of frontal winds.

Development of 3-DoF Flapping-wing Robot with Variable Amplitude Link Mechanism

Development of 3-DoF Flapping-wing Robot with Variable Amplitude Link Mechanism

Superfast high-resolution absolute 3D recovery of a stabilized flapping flight process.

Scientific research of a stabilized flapping flight process (e.g. hovering) has been of great interest to a variety of fields including biology, aerodynamics, and bio-inspired robotics. Different from the current passive photogrammetry based methods, the digital fringe projection (DFP) technique has the capability of performing dense superfast (e.g. kHz) 3D topological reconstructions with the projection of defocused binary patterns, yet it is still a challenge to measure a flapping flight process with the presence of rapid flapping wings. This paper presents a novel absolute 3D reconstruction method for a stabilized flapping flight process. Essentially, the slow motion parts (e.g. body) and the fast-motion parts (e.g. wings) are segmented and separately reconstructed with phase shifting techniques and the Fourier transform, respectively. The topological relations between the wings and the body are utilized to ensure absolute 3D reconstruction. Experiments demonstrate the success of our computational framework by testing a flapping wing robot at different flapping speeds.

The design and microfabrication of a sub 100 mg insect‐scale flapping‐wing robot

A piezo-actuated self-lifting insect inspired flapping-wing robot is presented. A novel method is presented in the work, which has taken into account the difficulties and the precision of assembly among micro components. Each component is properly designed and reasonably arranged to reduce the assembly difficulties of such insect-scale robot. Specifically, the design of the piezoelectric actuator has taken into account the electrical isolation and assembly issues. The transmission and the airframe are integrated into one component to avoid assembly difficulties. Fibre directions of wing veins are reasonably arranged to possess high strength and stiffness. As a result, this robot, which weighs 84 mg with a wingspan of 35 mm, can generate sufficient thrust to take off with a flapping amplitude approximately ±60° under the resonant wingbeat frequency of 100 Hz.

Experimental optimization of wing shape for a hummingbird-like flapping wing micro air vehicle

Flapping wing micro air vehicles (MAVs) take inspiration from natural fliers, such as insects and hummingbirds. Existing designs manage to mimic the wing motion of natural fliers to a certain extent; nevertheless, differences will always exist due to completely different building blocks of biological and man-made systems. The same holds true for the design of the wings themselves, as biological and engineering materials differ significantly. This paper presents results of experimental optimization of wing shape of a flexible wing for a hummingbird-sized flapping wing MAV. During the experiments we varied the wing ‘slackness’ (defined by a camber angle), the wing shape (determined by the aspect and taper ratios) and the surface area. Apart from the generated lift, we also evaluated the overall power efficiency of the flapping wing MAV achieved with the various wing design. The results indicate that especially the camber angle and aspect ratio have a critical impact on the force production and efficiency. The best performance was obtained with a wing of trapezoidal shape with a straight leading edge and an aspect ratio of 9.3, both parameters being very similar to a typical hummingbird wing. Finally, the wing performance was demonstrated by a lift-off of a 17.2 g flapping wing robot.

Dynamics and flight control of a flapping-wing robotic insect in the presence of wind gusts.

With the goal of operating a biologically inspired robot autonomously outside of laboratory conditions, in this paper, we simulated wind disturbances in a laboratory setting and investigated the effects of gusts on the flight dynamics of a millimetre-scale flapping-wing robot. Simplified models describing the disturbance effects on the robot's dynamics are proposed, together with two disturbance rejection schemes capable of estimating and compensating for the disturbances. The proposed methods are experimentally verified. The results show that these strategies reduced the root-mean-square position errors by more than 50% when the robot was subject to 80 cm s-1 horizontal wind. The analysis of flight data suggests that modulation of wing kinematics to stabilize the flight in the presence of wind gusts may indirectly contribute an additional stabilizing effect, reducing the time-averaged aerodynamic drag experienced by the robot. A benchtop experiment was performed to provide further support for this observed phenomenon.

Liftoff of an Electromagnetically Driven Insect-Inspired Flapping-Wing Robot

We present the first electromagnetically driven, self-lifting, sub-100-mg, insect-inspired flapping-wing microaerial vehicle. This robot, with a weight of 80 mg and a wingspan of 3.5 cm, can produce sufficient thrust to lift off. The wing beat frequency is up to 80 Hz and the flapping amplitude is approximately ±70°. An electromagnetic actuator is employed to control the flapping amplitude and create passive wing rotation. To the best of our knowledge, this is the world's smallest electromagnetically driven flapping-wing robot that is capable of liftoff.

Perching with a robotic insect using adaptive tracking control and iterative learning control

Inspired by the aerial prowess of flying insects, we demonstrate that their robotic counterpart, an insect-scale flapping-wing robot, can mimic an aggressive maneuver seen in natural fliers— landing on a vertical wall. Such acrobatic movement differs from simple lateral maneuvers or hover, and therefore requires additional considerations in the control strategy. In this paper, we propose a single-loop adaptive tracking flight control suite designed with an emphasis on the ability to track dynamic trajectories, and an iterative learning control algorithm to account for unmodeled dynamics and systematic errors for improved landing accuracy. Magnets were chosen to enable attachment to the vertical surface due to their simplicity. The proposed controller was verified in a series of hovering and aggressive translational flights. Furthermore, we show that by learning from previous failed attempts, the biologically-inspired robot could successfully perch on a magnetic wall after eight learning iterations.

Instantaneous wing kinematics tracking and force control of a high-frequency flapping wing insect MAV

The superior maneuverability of insect flight is enabled by rapid and significant changes in aerodynamic forces, a result of subtle and precise change of wing kinematics. The high sensitivity of aerodynamic force to wing kinematic change demands precise and instantaneous feedback control of the wing motion trajectory, especially in the presence of various parameter uncertainties and environmental disturbances. Current work on flapping wing robots was limited to open-loop averaged wing kinematics control. Here we present instantaneous closed-loop wing trajectory tracking of a DC motor direct driven wing-thorax system under resonant flapping. A dynamic model with parameter uncertainties and disturbances was developed and validated through system identification. For wing trajectory generation, we designed a Hopf oscillator based central pattern generator with smooth convergence. Using the linearized model while treating the nonlinearity as disturbance, we designed a proportional-integral-derivative (PID) controller and a linear quadratic regulator (LQR) for instantaneous wing trajectory tracking at 24 Hz; Using the original nonlinear model, we designed a nonlinear controller to achieve robust performance at over 30 Hz. The control algorithms were implemented and compared experimentally on a 7.5 g Flapping Wing Micro Air Vehicle (MAV). The experiments showed that the PID and nonlinear controls resulted in precise trajectory tracking; while LQR controller tracked with less precision but with smaller input effort. In addition, the nonlinear control algorithm achieved better tracking of wing trajectories with varying amplitude, bias, frequency, and split-cycles while adapting to the variations on wing morphological parameters such as wing geometry and stiffness. Furthermore, the lift force measurements of the nonlinear control results were compared with those of open-loop average wing kinematics control commonly adopted in current designs.

A Roll Controlling Approach for a Simple Dual-Actuated Flapping Aerial Vehicle Model

Aerial vehicles have been investigated recently in different contexts, due to their high potential of utilization in multiple application areas. Different mechanisms can be used for aerial vehicles actuation, such as the rotating multi-blade systems (Multi-Copters) and more recently flapping wings. Flapping wing robots have attracted much attention from researchers in recent years. In this study, a simple dual-actuated flapping mechanism is proposed for actuating a flapping wing robot. The mechanism is designed, simulated and validated in both simulation and experiments. A roll controlling approach is proposed to control the roll angle of the robot via controlling the speeds of both motors actuating each of the wings. The results achieved are validated experimentally, and are promising opening the door for further investigation using our proposed system

自在な羽ばたき動作を行える羽ばたき飛行ロボットの持続飛行の実現

This paper presents the realization of sustained flight of a flapping wing robot. Unmanned aerial vehicles (UAVs) have attracted a significant amount of attention in recent years due to their ability of flight. One of the UAVs attracting attention is the flapping robot like a bird. The robot can fly in the sky, and is safer than rotorcrafts such as helicopter and multicopter since the operating frequency is much less than rotorcrafts. In our previous paper, flapping wing robot with oscillating controlled RC servomotors has been developed and succeeded in a flight of 30m. However, long-distance and sustained flight is not realized yet. The purpose of this research is the realization of sustained flight of the flapping wing robot. We redesign and improve the flapping robot. Moreover, we make a catapult for achieving reproducible flight experiments.

チョウを規範としたはばたき飛翔ロボットの研究

This paper proposes a butterfly-inspired flapping-wing robot that is equipped with a variable flapping angle mechanism and describes generated force when the flapping angle was changed. Motion analysis of the mechanism showed that the flapping angle changed from 104 degrees to 129 degrees. Generated forces in vertical and horizontal directions were measured using a three-axis load cell and effect of the flapping angle on the fluid forces was investigated. The results showed that the force in vertical direction was large at a minimum flapping angle and a maximum flapping frequency.

Design and Research on Mechanism of Bionic Flapping-wing Air Vehicle

The fly mechanism and motion characteristics of the birds were analyzed. By the bionics principle, a new bionic flapping wing mechanism was proposed in order to imitate the motion of bird wing. The virtual prototype of this mechanism was established through ADAMS, then the kinematic simulation analysis was applied to the prototype in order to validate the feasibility of this mechanism. And a computational fluid dynamics software, named Fluent was employed to analyze the aerodynamic force of bionic wing. These results shorten the period of manufacturing of flapping wing mechanism, and can provide theoretical basis for the research and manufacture of bionic flapping wing robot. The Flapping-wing Air Vehicle (FAV) based on bionics is a sort of new aircraft which imitates birds. Compared with the traditional fixed wing and rotor aircraft, setting the lift, hovering and push functions in a flapping wing system is the main characteristics of Flapping-wing Air Vehicle and it has strong maneuverability (1). Flapping-wing Air Vehicle has advantages of high maneuverability, low noise, low cost, multifunction and potential applications to the modern war. In view of the FAV has great advantages in military and civilian applications, research institutions and universities around the world design various types of FAV. Research on this field has also been conducted in China. At present, the successful flight of FAV mostly adopts single crank rocker mechanism, such as MAV developed by northwestern polytechnical university (2). Although single crank rocker mechanism can achieve predetermined flapping frequency and angle, but itself is a symmetrical structure. The motion of both sides wings is asymmetry in the process of flapping flight and affects the flight stability and security. This paper analyzes the movement characteristics of bird wings from the perspective of bionics. A symmetric double sections flapping wing mechanism is designed in order to imitate the motion of bird wing. The virtual prototype of this mechanism is established through ADAMS, then the kinematic simulation analysis is applied to the prototype in order to improve the quality of the flapping wing flight. For the problem of the unsteady aerodynamic of flapping wing flight, by using the method of numerical simulation, the aerodynamic force is analyzed. The wing and tail are designed in the end. All these works are supposed to find the best design scheme and achieve sustainable flapping wing flight. 2. Design and Simulation Analysis of The Flapping -wing Mechanism

Multi-body simulation of a flapping-wing robot using an efficient dynamical model

The aim of this article is to present an efficient dynamical model for simulating flapping robot performance employing the bond graph approach. For this purpose, the complete constitutive elements of the system under investigation, including the main body and accessories, flapping mechanism, flexible wings and propulsion system consisting of a battery, DC motors and gear boxes, are considered. A complete model of the system was developed appending bond graph models of the subsystems together utilizing appropriate junctions. The wings were also modeled using ANSYS only for an initial evaluation. Moreover, a computer model was developed employing the block-oriented structure of Simulink in MATLAB software for simulation studies. Further investigation was performed developing a finite element model of the flexible wing and multi-body simulation tool. SimMechanics toolbox of MATLAB software was used to investigate whether the equations obtained from the bond graph were extracted correctly and whether the relationships between all the subsystems are maintained so that they lead to a logical motion for the flapping wing. The very good agreement between the results achieved from various models illustrates the validity and accuracy of the proposed bond graph model in this study. As a result, the offered approach presents a comprehensive and efficient model to obtain a clear insight into the power flow between the subsystems included in a flapping robot and provides helpful information for the design of such systems.

2A2-G10 サーボモータの揺動制御による羽ばたき飛行の実現

2A2-G10 サーボモータの揺動制御による羽ばたき飛行の実現

Corrigendum to A Review of Fabrication Options and Power Electronics for Flapping-wing Robotic Insects

Corrigendum to A Review of Fabrication Options and Power Electronics for Flapping-wing Robotic Insects

Model-Free Control of a Hovering Flapping-Wing Microrobot

We present a model-free experimental method to find a control strategy for achieving stable flight of a dual-actuator biologically inspired flapping-wing flying microrobot during hovering. The main idea proposed in this work is the sequential tuning of parameters for an increasingly more complex strategy in order to sequentially accomplish more complex tasks: upright stable flight, straight vertical flight, and stable hovering with altitude and position control. Each term of the resulting multiple-input---multiple-output (MIMO) controller has a physical intuitive meaning and the control structure is relatively simple such that it could potentially be applied to other kinds of flapping-wing robots.

Design of planar four-bar linkage with n specified positions for a flapping wing robot

This paper focuses on the design of a flapping wing robot and proposes a unified design formula for planar four-bar linkages with arbitrary n prescribed positions. The absolute coordinates of a circle point corresponding to every prescribed position are expressed by those of the first one through matrix transformation. Because the distance between any circle point and center point is always equal to the length of the side link jointed with the fixed base, a set of quadratic equations for the distance constraints are obtained. Expanding and rearranging these equations presents a linear system for the coordinates of center point. The condition for existing solution of these equations requires that the rank of the augmented rectangle coefficient matrix, C, should always be less than 3 as there are only two unknown coordinates for the center point. The rectangle augmented coefficient matrix C is (n−1)×3, and therefore it can be transformed to a 3×3 square matrix, M, by left multiplying the transpose of C. This provides a unified expression for the design of a planar four-bar linkage with arbitrary n positions for a flapping wing.