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Journal Article

ℒ1 Adaptive Flutter Suppression Control Strategy for Highly Flexible Structure

2013-09-17
2013-01-2263
The aim of this work is to apply an innovative adaptive ℒ1 techniques to control flutter phenomena affecting highly flexible wings and to evaluate the efficiency of this control algorithm and architecture by performing the following tasks: i) adaptation and analysis of an existing simplified nonlinear plunging/pitching 2D aeroelastic model accounting for structural nonlinearities and a quasi-steady aerodynamics capable of describing flutter and post-flutter limit cycle oscillations, ii) implement the ℒ1 adaptive control on the developed aeroelastic system to perform initial control testing and evaluate the sensitivity to system parameters, and iii) perform model validation and calibration by comparing the performance of the proposed control strategy with an adaptive back-stepping algorithm. The effectiveness and robustness of the ℒ1 adaptive control in flutter and post-flutter suppression is demonstrated.
Technical Paper

UAV Operation, Crash Analysis, and Measurement of Particle Concentrations above a Forest and Surrounding Farmland

2009-11-10
2009-01-3129
The Nucleation In ForesTs (NIFTY) campaign was conducted in the Morgan Monroe State Forest (MMSF) during the month of May 2008. The objectives of this campaign were to understand the principal mechanisms of nucleation, the limitations of nucleation and growth, the spatial extent of nucleation events, subsequent particle growth after nucleation in MMSF, and the link between particle nucleation and breakdown of the nocturnal boundary layer which enhances vertical mixing. This paper discusses the use of a UAV to perform selected aspects of this project, mission that was accomplished by a team of students during the campaign, and analysis of a crash which concluded the mission.
Technical Paper

System Identification from GVT and Taxiing of an Unmanned Aerial Vehicle

2013-09-17
2013-01-2190
The modal parameters of an aircraft structure are currently estimated from ground vibration tests (GVT). These tests are carried out on ground in order to estimate the frequency response functions first and then the modal parameters. Such estimates require one or more shakers to excite the structure together with simultaneous measurements of both the input and the output signals. Recent developments in operational modal analysis allowed such modal identification from the measurements of the output responses only, provided that the unmeasurable excitation is practically a white noise stochastic input in the frequency range of interest and is randomly exciting the different parts of the structure. In this paper the effects of the different test setup on the modal parameter estimates will be presented. Both input-output based experimental modal analysis and operational modal analysis are performed on an Unmanned Aerial Vehicle, the Clarkson University Golden Eagle.
Technical Paper

Structural and Manufacturing Considerations for a Research Unmanned Aerial Vehicle

2009-11-10
2009-01-3196
This paper discusses the various factors that were addressed in the planning process for the design and construction of an unmanned aerial vehicle (UAV) destined for use as a multirole research aircraft for Clarkson University. Details related to mission requirements, cost, construction materials, manufacturing methods, and regulatory requirements will be discussed. The resulting airframe, structure, manufacturing, and control system plan of action will be laid out. An overview of anticipated FAA regulations will be presented, and the need to design for conformity to said regulations addressed. Emphasis will be placed on design and manufacturing decisions relating to the extensive use of composite materials throughout the aircraft.
Technical Paper

Rapid Prototyping as a Tool to Support Wind Tunnel Testing of Unconventional Unmanned Airships

2013-09-17
2013-01-2193
Scaled models are often used to check the aerodynamic performance of full scale aircraft and airship concepts, which have gone through a conceptual and preliminary design process. Results from these tests can be quite useful to improve the design of unconventional airships whose aerodynamics might be quite different from classical configurations. Once the airship geometry has been defined, testing is required to acquire aerodynamic data necessary to implement the mathematical model of the airship needed by the flight control system to develop full autonomous capabilities. Rapid prototyping has the great potential of playing a beneficial role in unconventional autonomous airship design similarly to the success obtained in the design process of conventional aircrafts.
Technical Paper

Improved Multibody Model of Flexible Wing

2013-09-17
2013-01-2265
In the development of High Altitude Long Endurance (HALE) UAVs and their control the flexibility of the wing must be taken into account. The wing of this type of UAVs, usually made of highly flexible composite materials, has high aspect ratio with significant bending-torsional deformation during flight. The NASA Helios, as an example, has tragically shown that wing deformation coupled with control and power operation can cause serious problem in flight, instability can suddenly occur and can be quite difficult to foresee. In this paper the mathematical description of a flexible wing multibody model is presented. It is suitable to simulate the effect of both structural flexibility and flight dynamics and maneuvering on the wing deformation, and can be used to help developing control strategies for air vehicles with highly deformable wings.
Technical Paper

Experimental Methods for the Characterization of the Static and Dynamic Stability of a Spinning Body

2011-10-18
2011-01-2735
Newly developed technologies are enabling the design of Unmanned Aerial Vehicles (UAVs) and Micro Air Vehicles (MAVs) with heretofore unrealized capabilities. A tube-launch MAV would allow the increased flexibility to launch an aircraft rapidly without need for a runway or complex launching system, either from a vehicle, installation, or as a man-portable device. The MAV would fill the diameter of the launch tube and deploy aerodynamic lifting and control surfaces after launch. In order to deploy the lifting surfaces the MAV must be capable of deploying control surfaces, negating any tube-imparted roll rate, and developing an optimal flight attitude automatically. An experimental method was developed to characterize the aerodynamics and stability of a blunt body spinning under conditions of roll rate decay in the Clarkson University High Speed Wind tunnel. This method is to be used to evaluate the development of an active roll rate control system for spinning projectiles.
Technical Paper

Experimental Investigation on a 3D Wing Section Hosting Multiple SJAs for Stall Control Purpose

2015-09-15
2015-01-2453
Flow control over aerodynamic shapes in order to achieve performance enhancements has been a lively research area for last two decades. Synthetic Jet Actuators (SJAs) are devices able to interact actively with the flow around their hosting structure by providing ejection and suction of fluid from the enclosed cavity containing a piezo-electric oscillating membrane through dedicated orifices. The research presented in this paper concerns the implementation of zero-net-mass-flux SJAs airflow control system on a NACA0015, low aspect ratio wing section prototype. Two arrays with each 10 custom-made SJAs, installed at 10% and 65% of the chord length, make up the actuation system. The sensing system consists of eleven acoustic pressure transducers distributed in the wing upper surface and on the flap, an accelerometer placed in proximity of the wing c.g. and a six-axis force balance for integral load measurement.
Journal Article

Experimental In-Flight Rolling MAV Wing Deployment and Aerodynamic Characterization

2011-10-18
2011-01-2648
The deployment dynamics of a tape-spring style, folding MAV wing in flight are complicated and an investigation is made using wind tunnel testing. High speed photography is used to characterize the deployment motion of the wing while a force balance records six- axis aerodynamic loading of the model. An in-flight deployment of a folding wing would be advantageous after an autonomous tube launch, however the dynamics are potentially problematic due to buckling. Steady state aerodynamics of prototype tube-launch MAVs are characterized for both rigid body and compliant, rolling wings. Aerodynamic phenomena associated with the significant relative body size are identified. Wing deployments are demonstrated at four different angles-of-attack at single velocity, while an extreme case deployment is shown at a high velocity. Two-piece cylindrical shells are used to retain the wing prior to deployment and are released by hot-wire cutting of retaining lines.
Technical Paper

Design, Optimization, Performances and Flight Operation of an All Composite Unmanned Aerial Vehicle

2013-09-17
2013-01-2192
Unmanned Aerial Vehicles (UAVs) provide the ability to perform a variety of experimental tests of systems and unproven research technologies, including new autopilot systems and obstacle avoidance capabilities, without risking the lives of human pilots. This paper describes the activities of design, optimization, and flight operations of a UAV conceived at Clarkson University (USA) and equipped to perform wind speed measurements to support wind farmsite planning. The UAV design has been assisted and validated by the use of an automatic virtual environment for the assisted design of civil UAVs. This tool can be used as a “computing machine” for civil UAVs. The operator inputs the mission profile and other generic parameters and data about performance, aerodynamics, and weight breakdown are extracted. A mathematical model of the UAV for flight simulation and its dynamic computations, along with automatic drawing is also produced.
Technical Paper

Design, Manufacturing, and Testing of a Research Unmanned Aerial Vehicle

2011-10-18
2011-01-2721
This paper details the novel manufacturing processes for an experimental, all-composite, research UAV to be used by Clarkson University. Discussions will include an in depth report on the selection of materials, manufacturing methods, and the implementation and results of the fabrication procedures for the structural components along with the challenges of constructing an aircraft capable of meeting multiple FAA regulatory requirements.
Technical Paper

Design and Experimental Investigation of a Small UAV

2009-11-10
2009-01-3166
In this paper two different tools have been applied to the problem of designing a small UAV. With these tools a parametric study of wing configuration and sizing was performed. The focus of this study was to optimize range and endurance of the UAV during a particular flight mission. The two numerical analysis tools applied to the UAV wing design were developed for widely different analysis problems. The first tool, the aircraft DATCOM was developed for the preliminary design analysis of manned aircraft and will be used to perform parametric modeling and geometry optimization. The Projectile Rocket Ordinance Design and Analysis System (PRODAS®) software was developed for ballistic projectiles and will be used for 6 DOF fixed plane trajectory simulation of the developed UAV concepts. While the scale of the UAV selected does not match well with the DATCOM software, the mission requirements and analysis format of the software is advantageous.
Technical Paper

An Integrated Software Environment for UAV Missions Support

2013-09-17
2013-01-2189
This paper describes the design and development of a virtual environment conceived to support flight operations of an Unmanned Air Vehicle (UAV) used for wind mapping in the proximity of existing or planned wind farms. The virtual environment can be used in pre-flight briefings aiming to define a trajectory from a list of waypoints, to change and eventually re-plan the mission in case of intersection with no fly zones, to simulate the mission, and to preview images/videos taken from the UAV on-board cameras. During flight, the tool can be used to compute the wind speed along the trajectory by analyzing the data streaming from the UAV. The integration of Augmented Reality (AR) techniques in the flight environment provides assistance in remotely piloted landings, and allows visualizing flight and environmental information that are critical to the mission.
Technical Paper

Active Flow and Aeroelastic Control of Lifting Surfaces Using Synthetic Jet Actuators

2007-09-17
2007-01-3920
Active flow control devices such as zero-net-mass-flux actuators have broad aeronautical applications. Among them, low power and lightweight Synthetic Jet Actuators can be used to improve the performance of flight vehicles, providing load alleviation capabilities, expanding their flight envelope, and preventing catastrophic failure by aeroelastic instabilities. Numerical and experimental investigations are proving that SJAs are effective in actively altering the boundary layer; the effect of the momentum exchange due to the SJAs leads to a rearrangement of streamlines, a virtual aerodynamic shaping that enable changes in the aerodynamics forces acting on the lifting surfaces. This paper discusses development aspects that the authors have been conducting on the topic with applications to load alleviation and flutter suppression for aircraft wings.
Journal Article

A Reduced Order Model for the Aeroelastic Analysis of Flexible Wings

2013-09-17
2013-01-2158
The aeroelastic design of highly flexible wings, made of extremely light structures yet still capable of carrying a considerable amount of non-structural weights, requires significant effort. The complexity involved in such design demands for simplified mathematical tools based on appropriate reduced order models capable of predicting the accurate aeroelastic behaviour. The model presented in this paper is based on a consistent nonlinear beam model, capable of simulating the unconventional aeroelastic behaviour of flexible composite wings. The partial differential equations describing the wing dynamics are reduced to a dimensionless form in terms of three ordinary differential equations using a discretization technique, along with Galerkin's method. Within this approach the nonlinear structural model an unsteady indicial based aerodynamic model with dynamic stall are coupled.
Technical Paper

A Mesh Based Approach for Unconventional Unmanned Airship Added Masses Computation

2013-09-17
2013-01-2191
Added masses computation is a crucial aspect to be considered when the density of a body moving in a fluid is comparable to the density of the fluid displaced: added mass can be defined as the inertia added to a system because an accelerating or decelerating body displaces some volume of neighboring fluid as it moves through it. The motion of vehicles like airships and ships can be addressed only by keeping into account the effect of added masses, while in case of aircrafts and helicopters this contribution is usually neglected. Lighter Than Air flight simulation, unmanned airships flight control system, airships flight dynamics are typical applications in which added masses are fundamental to achieve an effective and realistic modeling. A panel based method using the mesh of an airship external shape is developed to account for the added massed.
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