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Journal ArticleDOI

Experimental Performance Evaluation of Coaxial Rotors for a Micro Aerial Vehicle

01 Oct 2013-Journal of Aircraft (American Institute of Aeronautics and Astronautics)-Vol. 50, Iss: 5, pp 1465-1480

AbstractBecause of their potential for application in both civil and military sectors as well as the challenge in designing a tiny flying vehicle, micro aerial vehicles have attracted enormous attention. Several configurations of micro aerial vehicles are under development, namely fixed wing, rotary wing, and flapping wing. Under rotary-wing micro aerial vehicles, coaxial contrarotating configurations with a stabilizer bar seem to provide excellent stability behavior in pitch and roll degrees of freedom. This paper presents the results of an experimental study performed on a coaxial-contrarotor helicopter model to evaluate the performance of the rotor system using different rotor blades. The thrust and power of the rotors in independent and coaxial configurations were observed. The percentage thrust loss in the coaxial configuration was seen to be dependent on the ratio of the upper- and lower-rotor revolutions per minute as well as the spacing between the rotors. A theoretical analysis using a nonuniform inflow ... more

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Proceedings ArticleDOI
05 Jan 2015
TL;DR: A complete dynamic model for an unmanned coaxial helicopter is established which is proven accurate but simple enough for dynamic analysis and real time simulation.
Abstract: Modeling and analysis of a coaxial helicopter’s dynamics is a demanding work because of the complex characteristics in rotor aerodynamics and swashplate mechanism. In this paper, a complete dynamic model for an unmanned coaxial helicopter is established which is proven accurate but simple enough for dynamic analysis and real time simulation. An 14-states aerodynamic model including flapping dynamics and induced velocities is derived considering interaction between rotors. The model is validated to have a good consistency with existed experimental and CFD results. After that, by introducing swashplate kinematics, actuator dynamics and rigid body dynamics, a complete model is constructed. Trim analysis is performed over a large range of forward flight speed, and the hovering performance is analyzed by calculating the necessary power and rotors’ figure of merit in different altitude and load. The coupling between heave and yaw motion is also analyzed to propose a decoupling strategy in control design.

6 citations

Proceedings ArticleDOI
13 Jan 2014
TL;DR: A technique for control mixing is proposed for the ease of pilot control and also closed loop design of coaxial rotor helicopters at the Micro Air Vehicle scale based on the aerodynamic interaction of the two rotors.
Abstract: Coaxial rotor helicopters at the Micro Air Vehicle scale are becoming widely accepted as an easy to fly and stable configuration. This study models the heave and yaw modes of the vehicles dynamics, based on the aerodynamic interaction of the two rotors. The linearized model is represented in state space with a closed form solution. It is then evaluated for its stability and control response. The coupling between the height and heading transient response is evaluated. Based on these characteristics, a technique for control mixing is proposed for the ease of pilot control and also closed loop design. The steady state values of the model are validated using typical parameters of a commercially available vehicle. The predicted thrust sharing between the rotors is found to match with that reported in experiments. The effect of the interaction between the two coaxial rotors on the system performance and stability is analyzed.

1 citations

Journal ArticleDOI
Shanyong Zhao1, Zhen Liu1, Che Penglei1, Bingfei Li1, Tianjiao Dang1, Chen Bu1 
Abstract: In this paper, the bio-inspired blade motion is introduced to improve the propulsive performance of nano rotor at an ultra-low Reynolds number. However, the complex flow interacts with the flexible...

1 citations

Journal ArticleDOI
TL;DR: Simulation and experiment compared with the conventional PIDC are carried out, the results demonstrate the effectiveness and the robustness of the proposed control method of this paper.
Abstract: Aiming at the position and attitude tracking of coaxial rotor aircraft (CRA), this paper proposes a combinatorial control method of sliding mode control (SMC) coupled with proportional-integral-derivative control (PIDC). Considering the complete description of flight dynamics, aerodynamics and airflow interference, the dynamical model of CRA is established. The dynamical model is simplified according to the actual flight, then the simplified dynamical model is divided into two subsystems: a fully-actuated subsystem and an under-actuated subsystem. The controller of the fully-actuated subsystem consists of a SMC controller coupled with a rate bounded PIDC controller, while the controller of the under-actuated subsystem is composed of a SMC controller. The sliding manifold is defined by combining the position and velocity tracking errors of the state variables for each subsystem. Lyapunov stability theory is used to verify the stability of the sliding mode controller, which ensures that all state trajectories of the system can reach and stay on the sliding mode surface, the uncertainty and external interference of the model are compensated. Simulation and experiment compared with the conventional PIDC are carried out, the results demonstrate the effectiveness and the robustness of the proposed control method of this paper.

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05 Jun 2000
Abstract: Preface Acknowledgements List of main symbols List of figures List of tables 1. Introduction: a history of helicopter flight 2. Fundamentals of rotor aerodynamics 3. Blade element analysis 4. Rotating blade motion 5. Basic helicopter performance 6. Conceptual design of helicopters 7. Rotor airfoil aerodynamics 8. Unsteady aerodynamics 9. Dynamic stall 10. Rotor wakes and tip vortices Appendix Index.

2,079 citations

05 Feb 2001
Abstract: Low-speed aerodynamics is important in the design and operation of aircraft flying at low Mach number, and ground and marine vehicles. This 2001 book offers a modern treatment of the subject, both the theory of inviscid, incompressible, and irrotational aerodynamics and the computational techniques now available to solve complex problems. A unique feature of the text is that the computational approach (from a single vortex element to a three-dimensional panel formulation) is interwoven throughout. Thus, the reader can learn about classical methods of the past, while also learning how to use numerical methods to solve real-world aerodynamic problems. This second edition has a new chapter on the laminar boundary layer (emphasis on the viscous-inviscid coupling), the latest versions of computational techniques, and additional coverage of interaction problems. It includes a systematic treatment of two-dimensional panel methods and a detailed presentation of computational techniques for three-dimensional and unsteady flows. With extensive illustrations and examples, this book will be useful for senior and beginning graduate-level courses, as well as a helpful reference tool for practising engineers.

1,651 citations

01 Jan 1926
Abstract: 1. Introduction 2. Bernoulli's equation 3. The stream function 4. Circulation and vorticity 5. The velocity potential and the potential function 6. The transformation of a circle into an aerofoil 7. The aerofoil in two dimensions 8. Viscosity and drag 9. The basis of aerofoil theory 10. The aerofoil in three dimensions 11. The monoplane aerofoil 12. The flow round an acerofoil 13. Biplane aerofoils 14. Wind tunnel interference on areofoils 15. The airscrew: momentum theory 16. The airscrew: blade element theory 17. The airscrew: wind tunnel interference Appendix Bibliography Index.

628 citations

01 Mar 1997
Abstract: The recent appearance of the Kamov Ka-50 helicopter and the application of coaxial rotors to unmanned aerial vehicles have renewed international interest in the coaxial rotor configuration. This report addresses the aerodynamic issues peculiar to coaxial rotors by surveying American, Russian, Japanese, British, and German research. (Herein, 'coaxial rotors' refers to helicopter, not propeller, rotors. The intermeshing rotor system was not investigated.) Issues addressed are separation distance, load sharing between rotors, wake structure, solidity effects, swirl recovery, and the effects of having no tail rotor. A general summary of the coaxial rotor configuration explores the configuration's advantages and applications.

162 citations

Journal ArticleDOI
Abstract: The aerodynamic characteristics of airfoils operating at Re = 4 X 10 3 were examined, varying the parameters related to the airfoil shape such as thickness, camber, and roughness. Airfoils with good aerodynamic performance at this Re have the following shape characteristics : (1) they are thinner than airfoils for higher Re numbers, (2) they have a sharp leading edge, and (3) they have a camber of about five percent with its maximum camber at about mid-chord. The characteristics of airfoils are strongly affected by leading edge vortices. The measured two-dimensional airfoil characteristics indicate that the planform, which greatly affects the flight performance of the three-dimensional wing at high Reynolds numbers, has little effect on the flight performance at this Reynolds number.

146 citations