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
TL;DR: In this paper, an experimental study performed on a coaxial-contrarotor helicopter model was performed to evaluate the performance of the rotor system using different rotor blades. But, the results of the experimental study were limited to a single-rotor configuration and 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.
Abstract: Because 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 ...
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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.
8 citations
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.
7 citations
TL;DR: In this article , a combinatorial control method of sliding mode control (SMC) coupled with proportional-integral-derivative control (PIDC) is proposed for position and attitude tracking of coaxial rotor aircraft (CRA).
5 citations
TL;DR: In this article , a ducted fan UAV is designed using the open source code OpenProp and the computational fluid dynamics simulation model using sliding mesh technique is established and validated as a reliable tool for highly vortical flows by propeller thrust experiment.
Abstract: Recently, ducted fan unmanned aerial vehicles (UAVs) have attracted considerable attention due to their potential for application in both civil and military missions. Compared with free propellers, the presence of duct can in principle decrease the flow contraction after propeller, and gives the potential to fly efficiently with high security, compact structure, and low noise. In the present study, a ducted fan UAV is designed using the open source code OpenProp. The computational fluid dynamics (CFD) simulation model using sliding mesh technique is established and validated as a reliable tool for highly vortical flows by propeller thrust experiment. The effect of the duct, revolution speed, and distance between propellers on the aerodynamic characteristics of the ducted fan UAV is evaluated in detail. Results show that the unducted coaxial upper and lower propellers generate 3.8%, 4.3% more thrust than the unducted single propellers, respectively, and the unducted upper and lower propellers generate 55.9%, 34.9% more thrust than ducted propellers, respectively. The ducted fan UAV generates 5.7% more thrust and consumes 39.1% less power than the unducted coaxial propellers. The thrust of the ducted fan UAV increases first and then follows with a decreased tendency as the distance between propellers increases.
3 citations
TL;DR: In this paper , a consideration of the coaxial rotor Mini UAV to analyse the suitability for mountain terrain is presented, and various design parameters are analyzed to arrive at viable design configurations for coaxial rotary wing UAVs to operate in mountain terrain.
Abstract: Due to its compactness, agility, good hover performance, and ease of carriage, coaxial rotor Mini UAV is apt for various military and civilian applications in mountain terrain. This paper examines various factors to arrive at viable configurations of coaxial rotor Mini UAV for applications in mountain terrain. A consideration of the coaxial rotor Mini UAV to analyse the suitability for mountain terrain is presented. Coaxial rotor design is evaluated to assess the design requirements of mountain terrain. Various design parameters are analysed to arrive at viable design configurations for coaxial rotor Mini UAVs to operate in mountain terrain. Due to mechanical complexities, more than three blades per rotor for a small coaxial rotary wing aircraft is not recommended. The compact frame of the coaxial rotor Mini UAV is a key advantage, so rotor blades with a radius bigger than 1 m are not desirable. With a radius smaller than 1 m, a range of 0.9 m to 1.2 m, and an rotor speed between 900 RPM and 1200 RPM for 3-blade and 2-blade coaxial rotors, the Mini UAV offers a variety of options for applications in mountain terrain.
1 citations
References
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01 Jan 2010
TL;DR: In this article, a nonlinear model for the coaxial helicopter muFly is presented to derive a dynamic model which accurately reflects the physical characteristics allowing accurate simulations and which is also simple enough to be used for the controller design later on.
Abstract: This thesis deals with two of the most important tasks during the design of a fully autonomous micro helicopter: the rotor and control design. Both areas are strongly affected by the extremely small size of the vehicle. The rotors on the micro helicopter are working in the low Reynolds number regime reducing strongly the efficiency and limiting the autonomy time of the helicopter. In order to increase the efficiency, the influence of various blade parameters and lift enhancing devices is investigated. This is approached by using three different simulation methods designated for different applications: a Blade Element Momentum Theory code, a Vortex Method and CFD simulations. Those simulation methods are validated on a coaxial test bench capable of measuring rotors of complex shapes manufactured on a rapid prototyping machine. Additionally the drive train of the helicopter is integrated in the investigations allowing a realistic scenario as on the helicopter. The developed methods and obtained investigation results assist researchers and engineers in developing an efficient propulsion system for micro helicopters. On the control side the small size leads to faster system dynamics and limits the payload for accurate sensors and actuators. The control problem is first addressed by the development of a nonlinear model for the coaxial helicopter muFly. Here the goal is to derive a dynamic model which accurately reflects the physical characteristics allowing accurate simulations and which is also simple enough to be used for the controller design later on. In order to validate the model and to find the platform depending system parameters an identification process is carried out. The identification on the real flight data is done using a nonlinear technique called the Covariance Matrix Adaptation Evolution Strategy (CMA-ES). The results obtained show the accuracy of the nonlinear model. Finally, the control strategy is presented including the low-level and highlevel control. The low-level controllers for attitude and heave are designed by the H∞ method. The controllers are implemented on the helicopter and successively tested during flight. Additionally, a high-level control approach
19 citations
27 May 2009
TL;DR: Advantages over traditional micro-scaled VTOL configurations include passive stability, efficient autorotation, low body drag, mechanical simplicity, low cost, high payload capacity, and substantial damage tolerance.
Abstract: Conventionally Micro/Nano scaled hovering flight presents a myriad of challenges and unique design opportunities. The culmination of microelectronics and state of the art measuring devices has enabled the creation of a Micro-air-vehicle (MAV 1 ) resembling one of nature’s most efficient fliers, the seed of the Maple tree. The planform design of the VTOL mechanical samara is based on previous work 2 , which characterized autorotation efficiency, and is employed as the main lifting surface of the vehicle. The collective pitch is controlled by a servo actuator, and the rotation rate is maintained by a propeller oriented parallel to the plane of rotation and is offset from the center of mass. Vertical speed and height are controlled by variation of collective pitch at constant propeller rpm, or variation of propeller rpm at a constant collective pitch. Precise attitude data is collected by a VICON 3 motion capture system. The commanded altitude of the Samara is maintained by feeding back the error in position to a control loop which contains the system and actuator dynamics. Identifying the relationship between vertical velocity and collective pitch for a given thrust is one of the main goals of these experiments. Two vehicles are presented and compared in this study. The first vehicle, Samara-I has a maximum dimension of 27cm, and weights 75 grams. The second vehicle, Samara-II has a maximum dimension of 18cm, and weighs 38 grams. The vehicles can be launch from the ground, or by hand and have been flown outdoors in winds up to 10 mph. Advantages over traditional micro-scaled VTOL configurations include passive stability, efficient autorotation, low body drag, mechanical simplicity, low cost, high payload capacity, and substantial damage tolerance.
13 citations
Dissertation•
01 Jan 2010
TL;DR: In this article, a ducted contra-rotating coaxial rotor system was designed and tested to assess its potential use as a micro aerial vehicle (MAV), and performance measurements (thrust and power) of the system in hover and forward flight were obtained.
Abstract: Title of thesis: DESIGN AND PERFORMANCE OF A DUCTED COAXIAL ROTOR IN HOVER AND FORWARD FLIGHT Timothy Edward Lee, Master of Science, 2010 Thesis directed by: Professor J. Gordon Leishman Department of Aerospace Engineering A ducted contra-rotating coaxial rotor system was designed and tested to assess its potential use as a micro aerial vehicle (MAV). Performance measurements (thrust and power) of the system in hover and forward flight were obtained. The influence of several design parameters (rotor spacing, duct inlet shape, position of rotors within the duct, and tip clearance) on performance was determined. Performance measurements of the unducted coaxial rotor, as well as the unducted/ducted single rotor configurations, were also obtained to give a performance baseline for the ducted coaxial rotor. The aerodynamic characteristics of the isolated duct were assessed from loads measurement and surface flow visualization. While the net system performance of operating the coaxial rotor within the confines of a duct was not always improved, the ducted coaxial rotor concept is still attractive for a MAV based on total attainable thrust for a given rotor size and other operational benefits. DESIGN AND PERFORMANCE OF A DUCTED COAXIAL ROTOR IN HOVER AND FORWARD FLIGHT by Timothy Edward Lee Thesis submitted to the Faculty of the Graduate School of the University of Maryland, College Park in partial fulfillment of the requirements for the degree of Master of Science 2010 Advisory Committee: Professor J. Gordon Leishman, Chair/Advisor Professor Roberto Celi Associate Professor James Baeder
8 citations