Design and Implementation of Robofly Wing Flapping Mechanism Using Piezoelectric Crystal

Micromechanical Flying Insect (MFI) or simply ‘robofly’ is a newly introduced air vehicle which is tiny and maneuverable. It is a project requiring collaboration from several academic areas such as biology, robotics and engineering. The target robotic insects are electromechanical devices propelled by a pair of independent flapping wings to achieve sustained autonomous flight, thereby mimicking real insects. Part of the research involves trying to figure out how insects, and specifically flies, flap their wings with high speed and intensity. Initiation stage of this project was to conduct thorough study and research on the robofly. Considering high frequency of flapping motion, robofly is best actuated by piezoelectric ceramics. The direct piezoelectric effect is that piezo ceramic generates an electrical charge during mechanical distortion or load. During an inverse piezoelectric effect the piezoceramic body changes under the influence of an electrical field. The Piezoelectric effect can occur under the influence of external forces. Depending on the force direction electrical charges with corresponding polarity are generated. An inverse piezoelectric effect takes place under the influence of electrical fields. The body changes its dimension along with the change of voltage. The main objective of this project is mainly the design of the thorax structure for robofly and it is defined as the most critical part during this project ongoing. The most efficient method for the robofly to take off into the air is to design a flapping mechanism actuated by piezoelectric. Using a four bar linkage, small piezoelectric linear displacement can be converted to rotational wing motion at high frequency. Solid model design and motion simulation has been generated for both options. The output from both designs are to be compared and the best output in terms of wing stroke angle being picked as best design

Design and Implementation of Robofly Wing Flapping Mechanism Using Piezoelectric Crystal

Micromechanical Flying Insect (MFI) or simply ‘robofly’ is a newly introduced air vehicle which is tiny and maneuverable. It is a project requiring collaboration from several academic areas such as biology, robotics and engineering. The target robotic insects are electromechanical devices propelled by a pair of independent flapping wings to achieve sustained autonomous flight, thereby mimicking real insects. Part of the research involves trying to figure out how insects, and specifically flies, flap their wings with high speed and intensity. Initiation stage of this project was to conduct thorough study and research on the robofly. Considering high frequency of flapping motion, robofly is best actuated by piezoelectric ceramics. The direct piezoelectric effect is that piezo ceramic generates an electrical charge during mechanical distortion or load. During an inverse piezoelectric effect the piezoceramic body changes under the influence of an electrical field. The Piezoelectric effect can occur under the influence of external forces. Depending on the force direction electrical charges with corresponding polarity are generated. An inverse piezoelectric effect takes place under the influence of electrical fields. The body changes its dimension along with the change of voltage. The main objective of this project is mainly the design of the thorax structure for robofly and it is defined as the most critical part during this project ongoing. The most efficient method for the robofly to take off into the air is to design a flapping mechanism actuated by piezoelectric. Using a four bar linkage, small piezoelectric linear displacement can be converted to rotational wing motion at high frequency. Solid model design and motion simulation has been generated for both options. The output from both designs are to be compared and the best output in terms of wing stroke angle being picked as best design

An Experimental Investigation into the Effect of Flap Angles for a Piezo-Driven Wing

This article presents a comparison of results from six degree of freedom force and moment measurements and Particle Image Velocimetry (PIV) data taken on the Air Force Institute of Technology\u27s (AFIT) piezoelectrically actuated, biomimetically designed Hawkmoth, Manduca Sexta, class engineered wing, at varying amplitudes and flapping frequencies, for both trimmed and asymmetric flapping conditions to assess control moment changes. To preserve test specimen integrity, the wing was driven at a voltage amplitude 50% below the maximum necessary to achieve the maximal Hawkmoth total stroke angle. 86 and 65 stroke angles were achieved for the trimmed and asymmetric tests respectively. Flapping tests were performed at system structural resonance, and at 10% off system resonance at a single amplitude, and PZT power consumption was calculated for each test condition. Two-dimensional PIV visualization measurements were taken transverse to the wing planform, recorded at the mid-span, for a single frequency and amplitude setting, for both trimmed and asymmetric flapping to correlate with the 6-DoF balance data. Linear velocity data was extracted from the 2-D PIV imagery at 1/2 and 1 chord locations above and below the wing, and the mean velocities were calculated for four separate wing phases during the flap cycle. The mean forces developed during a flap cycle were approximated using a modification of the Rankine-Froude axial actuator disk model to calculate the transport of momentum flux as a measure of vertical thrust produced during a static hover flight condition. Values of vertical force calculated from the 2-D PIV measurements were within 20% of the 6-DOF force balance experiments. Power calculations confirmed flapping at system resonance required less power than at off resonance frequencies, which is a critical finding necessary for future vehicle design considerations

Large-strain piezoelectric actuators using controlled structural buckling

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 59-60).Buckling is a highly nonlinear and singular phenomenon in thin beams, and is usually an undesired characteristic that must be prevented from occurring in engineered systems. Buckling, however, can be a useful mechanism for gaining extremely large displacement amplification, since a infinitesimal displacement in the axial direction of the beam may lead to a large deflection in the middle of the beam. This thesis presents a novel large-strain piezoelectric actuator exploiting the buckling of a structure with imbedded piezoelectric stack actuators. The realization of this buckling actuator began by rethinking the paradigm of where PZT stacks are placed in traditional flexure-based displacement amplification mechanisms. Although the free displacement of a PZT stack is only 0.1% of the stack length, the buckling mechanism can produce a large bipolar displacement that is approximately 150 times larger than the original PZT displacement. Furthermore, the structural buckling produces a pronounced nonlinearity in output impedance; the effective stiffness viewed from the output port varies as a function of output displacement, which can be a useful property for those applications where actuator stiffness needs to vary. Buckling is controlled with phased activation of the input units and either 1) a strategically placed redirecting stiffness or 2) multiple buckling units working in parallel.by Devin Michael Neal.S.M

Design and Control of Flapping Wing Micro Air Vehicles

Flapping wing Micro Air Vehicles (MAVs) continues to be a growing field, with ongoing research into unsteady, low Re aerodynamics, micro-fabrication, and fluid-structure interaction. However, research into flapping wing control of such MAVs continues to lag. Existing research uniformly consists of proposed control laws that are validated by computer simulations of quasi-steady blade-element formulae. Such simulations use numerous assumptions and cannot be trusted to fully describe the flow physics. Instead, such control laws must be validated on hardware. Here, a novel control technique is proposed called Bi-harmonic Amplitude and Bias Modulation (BABM) which can generate forces and moments in 5 vehicle degrees of freedom with only two actuators. Several MAV prototypes were designed and manufactured with independently controllable wings capable of prescribing arbitrary wing trajectories. The forces and moments generated by a MAV utilizing the BABM control technique were measured on a 6-component balance. These experiments verified that a prototype can generate uncoupled forces and moments for motion in five degrees of freedom when using the BABM control technique, and that these forces can be approximated by quasi-steady blade-element formulae. Finally, the prototype performed preliminary controlled flight in constrained motion experiments, further demonstrating the feasibility of BABM

Design optimization of small-scale unmanned air vehicles

Ph.DDOCTOR OF PHILOSOPH

Towards MAV Autonomous Flight: A Modeling and Control Approach

This thesis is about modeling and control of miniature rotary-wing flying vehicles, with a special emphasis on quadrotor and coaxial systems. Mathematical models for simulation and nonlinear control approaches are introduced and subsequently applied to commercial aircrafts: the DraganFlyer and the Hummingbird quadrotors, which have been hardware-modified in order to perform experimental autonomous flying. Furthermore, a first-ever approach for modeling commercial micro coaxial mechanism is presented using a flying-toy called the Micro-mosquito

Aeroelastic investigation of conventional fixed wings and bio-inspired flapping wings by analysis and experiment.

In this thesis, the structure and aeroelastic design, analysis and optimization of conventional fixed wing is firstly addressed. Based on the study results of conventional fixed wing, the study then focuses on the more complicated aerodynamics and aeroelasticity of flapping wing Micro Air Vehicles (MAV). A Finite Element (FE) model of a composite aircraft wing is firstly used as case study for the aeroelasticity of conventional fixed wing. A MATLAB-NASTRAN interfaced optimization platform is created to explore the optimal design of the wing. Optimizations using the developed platform show that 13% of weight reduction can be achieved when the optimization objective is set to minimize wing weight; and 18.5% of flutter speed increase can be achieved when aeroelastic tailoring of composite laminate layups is carried out. The study results further showed that the most sensitive part of the wing for aeroelastic tailoring is near the engine location, which contributes to the majority of flutter speed increment for optimization. In order to facilitate the structural design of non-circular cross section fuselage of Blended-Wing-Body (BWB) aircraft, an analytical model of 2D non-circular cross section is developed, which provides efficient design and optimization of the fuselage structure without referring to FE models. A case study based on a typical BWB fuselage using the developed model shows that by optimizing the fuselage structure, significant weight saving (17%) can be achieved. In comparison with the conventional fixed wing, insect flapping wings demonstrate more complicated aerodynamic and aeroelastic phenomena. A semi-empirical quasi-steady aerodynamic model is firstly developed to model the unsteady aerodynamic force of flapping wing. Based on this model, the aerodynamic efficiency of a Flapping Wing Rotor (FWR) MAV is investigated. The results show that the optimal wing kinematics of the FWR falls into a narrow range of design parameters governed by the dimensionless Strouhal number (St). Furthermore, the results show that the passive rotational of the FWR converges to an equilibrium state of high aerodynamic efficiency, which is a desirable feature for MAV applications. Next, the aerodynamic lift coefficient and efficiency of the FWR are calculated and compared with typical insect-like flapping wings and rotary wing. The results show that the aerodynamic efficiency of FWR in typical wing kinematics is higher than insect-like flapping wings, but slightly lower than the conventional rotary wing; the FWR aerodynamic lift coefficient (CL) surpassed the other wings significantly. Based on the numerical results, the study then continued to experimental investigations of the FWR. A prototype FWR model of weight 2.6g is mounted on a load cell to measure the instantaneous lift production. The kinematics of the wing is captured using high speed camera. Aeroelastic twist of the wing is measured using the resulting wing motion. Analyses by CFD and the quasi-steady aerodynamic model is then carried out and compared with experimental results. The study revealed that passive twist of the FWR wing due to aeroelastic effects forms desirable variations of wing Angle of Attack (AoA), which improves the aerodynamic performance of FWR. The results of the thesis provide guidance for structural, aerodynamic and aeroelastic design, analysis and optimization of conventional fixed wing, as well as bio-inspired flapping wing MAVs.PhD in Aerospac

Abstract Dynamically tuned design of the MFI thorax ∗

This paper presents an analysis of the major mechanical component (the thorax) of the micromechanical flying insect (MFI), a centimeter sized aerial vehicle currently in development at UC Berkeley. We present a description of the kinematics of the mechanism which converts piezoelectric actuation into complex 3D wing motion. A complete non-linear modeling of the system based on the Lagrangian energy technique is presented. A design methodology is presented in order to achieve optimal matching conditions. Two kinds of sensors which are presently utilized on the MFI are described. Experimental results are presented which validate some of the modeled non-linear aspects of the mechanism.