Author: Dennis K. HendersonPublisher:
ISBN:
Category :
Languages : en
Pages : 204
Book Description
Aeroelastic Vehicle Flight Control Synthesis Using Quantitative Feedback Theory
Author: Dennis K. HendersonMasters Theses in the Pure and Applied Sciences
Author: Wade H. ShaferPublisher: Springer Science & Business Media
ISBN: 1461519691
Category : Science
Languages : en
Pages : 426
Book Description
Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS)* at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dis semination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volumes were handled by an international publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 38 (thesis year 1993) a total of 13,787 thesis titles from 22 Canadian and 164 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this impor tant annual reference work. While Volume 38 reports theses submitted in 1993, on occasion, certain uni versities do report theses submitted in previous years but not reported at the time.
Masters Theses in the Pure and Applied Sciences
Author: Sade H ShaferPublisher: Springer Science & Business Media
ISBN:
Category : Education
Languages : en
Pages : 440
Book Description
Cited in Sheehy, Chen, and Hurt . Volume 38 (thesis year 1993) reports a total of 13,787 thesis titles from 22 Canadian and 164 US universities. As in previous volumes, thesis titles are arranged by discipline and by university within each discipline. Any accredited university or college with a grad
Aeronautical Engineering
Author: Flight-vehicle Materials, Structures, and Dynamics--assessment and Future Directions: Structural dynamics and aeroelasticity
Author: Ahmed Khairy NoorPublisher:
ISBN:
Category : Science
Languages : en
Pages : 536
Book Description
The fifth volume of a six-volume monograph, the objective of which is to broaden the awareness among material scientists, engineers, and research workers about the recent developments which can impact future flight vehicles. The present volume, Volume 5, is divided into three parts. The first part h
Aeroelastic Analysis of a Joined-Wing Sensorcraft
Author: Jennifer J. SitzPublisher:
ISBN: 9781423519256
Category : Aeroelasticity
Languages : en
Pages : 84
Book Description
This study performed an aeroelastic analysis of a joined-wing SensorCraft. The analysis was completed using an aluminum structural model that was splined to an aerodynamic panel model. The force and pressure distributions were examined for the four aerodynamic panels: aft wing, fore wing, joint, and outboard tip. Both distributions provide the expected results (elliptical distribution), with the exception of the fore wing. The fore wing appears to be affected by interference with the joint. The use of control surfaces for lift and roll was analyzed. Control surfaces were effective throughout most of the flight profile, but may not be usable due to radar requirements. The aft wing was examined for use in trimming the vehicle. Also, two gust conditions were examined. In one model, the wing twist was simulated using a series of scheduled control surfaces. Trim results (angle of attack and twist angle) were compared to those of previous studies, including gust conditions. The results are relatively consistent with those calculated in previous studies, with variations due to differences in the aerodynamic modeling. To examine a more physically accurate representation of aft wing twist, it was also modeled by twisting the wing at the root. The twist was then carried through the aft wing by the structure. Trim results were again compared to previous studies. While consistent for angle of attack results, the aft wing twist deflection remained relatively constant throughout the flight profile and requires further study.
Scientific and Technical Aerospace Reports
Author: NASA SP.
Author: Aeronautical Engineering: A Cumulative Index to a Continuing Bibliography (supplement 287)
Author: Robust Scheduling Control of Aeroelasticity
Author: Zebb David PrimePublisher:
ISBN:
Category : Aeroelasticity
Languages : en
Pages : 163
Book Description
Aeroelasticity is a broad term describing the often complex interactions between structural mechanics and aerodynamics. Aeroelastic phenomena such as divergence and flutter are potentially destructive, and thus must be avoided. Passive methods to avoid undesirable aeroelastic phenomena often involve the addition of mass and/or limiting the achievable performance of the aircraft. However, active control methods allow both for the suppression of undesirable aeroelastic phenomena, and for utilisation of desirable aeroelastic phenomena using actuators, thus increasing performance without the associated weight penalty of passive systems. The work presented in this thesis involves the design, implementation and experimental validation of novel active controllers to suppress undesirable aeroelastic phenomena over a range of airspeeds. The controllers are constructed using a Linear Parameter Varying (LPV) framework, where the plant and controllers can be represented as linear systems which are functions of a parameter, in this case airspeed. The LPV controllers are constructed using Linear Matrix Inequalities (LMIs), which are convex optimisation problems that can be used to represent many linear control objectives. Using LMIs, these LPV controllers can be constructed such that they self-schedule with airspeed and provide upper performance bounds during the design process. The aeroelastic phenomena being suppressed by these controllers are Limit-Cycle Oscillations (LCOs), which are a form of flutter with the aeroelastic instability bounded by a structural nonlinearity in the aeroelastic system. In this work, the aeroelastic system used is the Nonlinear Aeroelastic Test Apparatus (NATA), an experimental aeroelastic test platform located at Texas A&M University. Three and four degree-of-freedom dynamic models were derived for the NATA, which include second-order servo motor dynamics. These servo motor dynamics are often neglected in literature but are sufficiently slow that their dynamics are significant to the controlled response of the NATA. The dynamic model also incorporates quasi-steady aerodynamics, which are accurate for low Strouhal numbers calculated from the oscillation frequency of the wing. Is it shown how the dynamics of the NATA can be represented in LPV form, with a quadratic dependence on airspeed and linear dependence on torsional stiffness. Using a variety of techniques the parameters of the NATA are identified, and shown through nonlinear simulation to provide excellent agreement with experimental results. It is also argued that structural nonlinearity, in the way of a nonlinear torsional spring connecting the wing section to the base, generally improves stability due to its largely quadratic stiffness function, and hence in many instances it is safe to linearise this nonlinearity when designing a controller. Using a H2 generalised control problem representation of a Linear Quadratic Regulator (LQR) state-feedback controller, LPV synthesis LMIs are constructed using a standard transformation which render the LMIs affine in the transformed controller and Lyapunov matrices. These matrices have the same quadratic dependence on airspeed as the NATA model. To reduce conservatism the parameter space of airspeed versus airspeed squared is gridded into triangular convex hulls over the true parameter curve, and the LMIs are numerically optimised to give an upper bound on the H2 norm across the design airspeed. The resulting state-feedback controller is constructed from the transformed controller and Lyapunov matrices, and can be solved symbolically as a function of airspeed, however it forms a high-order rational function of airspeed, hence it is quicker to solve for the controller gains numerically on-line. The controller is analysed for the classical measures of robustness, namely gain and phase margins, and maximum sensitivity. While not providing the guarantees of these measures that a conventional LQR controller provides, the controller is shown to be sufficiently robust across the airspeed design range. Experimental results for this controller were performed, and the results show excellent LCO suppression and disturbance rejection, the results from which are published in Prime et al. (2010). Following the above work based on a scalar performance index, the upper bound on the H2 norm is allowed to vary with airspeed using the same quadratic dependence on airspeed as the NATA model, and the transformed controller and Lyapunov matrices. A simple method of solving the LMIs is shown such that the LPV H2 upper bound is as close to optimal as possible, and using this method a new controller is synthesised. This new controller is compared against the LPV LQR controller with the scalar performance index, and is shown to be closer to optimal across the airspeed design range. Nonlinear simulations of the controlled NATA using this new controller are then presented. Based on Prime et al. (2008), a Linear Fractional Transformation (LFT) is applied to the NATA model to render the dynamics dependent upon the feedback of the linear value of airspeed. This allows the LMIs to be constructed at only two points, the extreme values of the linear design airspeed, rather than gridding over the parameter space as was performed above. An output-feedback controller that itself depends upon the feedback of a function that is linearly dependent upon airspeed is constructed using an induced L2 loop-shaping framework. The induced L2 performance objective is based upon a Glover-McFarlane H∞ loop-shaping process where the NATA singular values are shaped using pre- and post-filters, and minimising the induced L2 norm from both the input and output to both the input and output. An LFT controller is synthesised, and simulations are performed showing the suppression of LCOs.