Finite Element Analysis and Active Control for Nonlinear Flutter of Composite Panels Under Yawed Supersonic Flow

A coupled structural-electrical modal finite element formulation for composite panels with integrated piezoelectric sensors and actuators is presented for nonlinear panel flutter suppression under yawed supersonic flow. The first-order shear deformation theory for laminated composite plates, the von Karman nonlinear strain-displacement relations for large deflection response, the linear piezoelectricity constitutive relations, and the first-order piston theory of aerodynamics are employed. Nonlinear equations of motion are derived using the three-node triangular MIN3 plate element. Additional electrical degrees of freedom are introduced to model piezoelectric sensors and actuators. The system equations of motion are transformed and reduced to a set of nonlinear equations in modal coordinates. Modal participation is defined and used to determine the number of modes required for accurate solution. Analysis results for the effect of arbitrary flow yaw angle on nonlinear supersonic panel flutter for isotropic and composite panels are presented. The results show that the flow yaw angle has a major effect on the panel limit-cycle oscillation amplitude and deflection shape. The effect of combined aerodynamic and acoustic pressure loading on the nonlinear dynamic response of isotropic and composite panels is also presented. It is found that combined acoustic and aerodynamic loads have to be considered for high aerodynamic pressure values. Simulation studies for nonlinear panel flutter suppression using piezoelectric self-sensing actuators under yawed supersonic flow are presented for isotropic and composite panels. Different control strategies are considered including linear quadratic Gaussian (LQG), linear quadratic regulator (LQR) combined with the extended Kalman filter (EKF), and optimal output feedback. Closed loop criteria based on the norm of feedback control gain (NFCG) and on the norm of Kalman filter estimator gain (NKFEG) are used to determine the optimal location of piezoelectric actuators and sensors, respectively. Optimal sensor and actuator locations for a range of yaw angles are determined by grouping the optimal locations for different angles within the range. The results demonstrate the effectiveness of piezoelectric materials and of the nonlinear output controller comprised of LQR state feedback and EKF nonlinear state estimator in suppressing nonlinear flutter of isotropic and composite panels at different flow yaw angles

Advanced Mobile Robotics: Volume 3

Mobile robotics is a challenging field with great potential. It covers disciplines including electrical engineering, mechanical engineering, computer science, cognitive science, and social science. It is essential to the design of automated robots, in combination with artificial intelligence, vision, and sensor technologies. Mobile robots are widely used for surveillance, guidance, transportation and entertainment tasks, as well as medical applications. This Special Issue intends to concentrate on recent developments concerning mobile robots and the research surrounding them to enhance studies on the fundamental problems observed in the robots. Various multidisciplinary approaches and integrative contributions including navigation, learning and adaptation, networked system, biologically inspired robots and cognitive methods are welcome contributions to this Special Issue, both from a research and an application perspective

Structural dynamics branch research and accomplishments

Summaries are presented of fiscal year 1989 research highlights from the Structural Dynamics Branch at NASA Lewis Research Center. Highlights from the branch's major work areas include aeroelasticity, vibration control, dynamic systems, and computation structural methods. A listing of the fiscal year 1989 branch publications is given

Technology for large space systems: A bibliography with indexes (supplement 17)

This bibliography lists 512 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1987 and June 30, 1987. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

Dynamic analysis of magnetorheological elastomer configured sandwich structures

The work presented in this thesis is concerned with the investigation of the dynamic behaviour of magnetorheological elastomers (MREs) and smart sandwich structures. An extensive review, covering existing smart materials and their applications, has highlighted that smart materials and structures can be applied to large scale structures. Comprehensive experimental tests have been carried out in order to gain knowledge and data on the dynamic shear properties and behaviour of stiffness change of MRE and MRE cored adaptive sandwich beam structures depending on magnetic fields. Dynamic shear property tests with different curing stages have been enhanced to obtain various properties. The new developed forced vibration test rig enabled forced vibration tests of MRE embedded sandwich beam with various aspects such as different magnetic field strength, various oscillations of force amplitudes, boundary conditions and damping effects under localised magnetic fields to be made. In parallel to these experimental investigations, a new theoretical model was developed by combining the magnetisation effects on iron particles in terms of the curing times. In addition, a new macro scale modelling approach for rubber like materials (nonlinear behaving materials) was made by adopting FEA analysis to obtain the optimum volume of pores and size of iron particles to enhance the performance of MREs. A higher order sandwich beam theory is extended to include damping properties of MRE. It has been demonstrated that a higher order sandwich beam theory appears to be the most versatile and accurate modelling method for a sandwich beam with an MRE core material. The results from higher order theory have been combined with a power flow analysis for the smart floating sandwich raft vibration isolation system. Finally, an experimental study was performed to illustrate the control capabilities of MRE adaptive vibration absorber for a propeller shaft in real time. From this research work, a better understanding of the dynamic behaviour of MRE embedded sandwich beam has been acquired

Vibration, Control and Stability of Dynamical Systems

From Preface: This is the fourteenth time when the conference “Dynamical Systems: Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and Ministry of Science and Higher Education of Poland. It is a great pleasure that our invitation has been accepted by recording in the history of our conference number of people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcomed over 180 persons from 31 countries all over the world. They decided to share the results of their research and many years experiences in a discipline of dynamical systems by submitting many very interesting papers. This year, the DSTA Conference Proceedings were split into three volumes entitled “Dynamical Systems” with respective subtitles: Vibration, Control and Stability of Dynamical Systems; Mathematical and Numerical Aspects of Dynamical System Analysis and Engineering Dynamics and Life Sciences. Additionally, there will be also published two volumes of Springer Proceedings in Mathematics and Statistics entitled “Dynamical Systems in Theoretical Perspective” and “Dynamical Systems in Applications”

Large space structures and systems in the space station era: A bibliography with indexes

Bibliographies and abstracts are listed for 1372 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1990 and June 30, 1990. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

14th Conference on Dynamical Systems Theory and Applications DSTA 2017 ABSTRACTS

From Preface: This is the fourteen time when the conference “Dynamical Systems – Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and the Ministry of Science and Higher Education. It is a great pleasure that our invitation has been accepted by so many people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcome nearly 250 persons from 38 countries all over the world. They decided to share the results of their research and many years experiences in the discipline of dynamical systems by submitting many very interesting papers. This booklet contains a collection of 375 abstracts, which have gained the acceptance of referees and have been qualified for publication in the conference proceedings [...]

Modeling and shape estimation of smart structures for active control

Piezoelectric materials allow the transformation of electric constraints into mechanical constraints and vice versa. They are used as controllers or sensors in the industrial field. The analysis of the behavior of piezoelectric materials lays within the use of these materials in structures whose form or modes of vibration are to be controlled. The need for these studies is crucial. From a general point of view, the need for stability of structures has become increasingly important with the development of technologies related to telecommunications and microtechniques. Adaptive structures are the only means to achieve the requisite stability in the face of diverse situations. The objective of this research is to model the effect of electro- mechanical coupling and to estimate the shape of the adaptive structures for active control. Ideal models were developed for various adaptive structures. These models make it possible to determine the static and dynamic behavior of these structures. The model behavior was compared with experimental results and the, numerical, finite elements and the Rayleigh-Ritz methods. Results obtained from all of the above approaches reveal good agreements among them. For a possible application of active control, the analysis of substructures in commercial FEA software ANSYS is used to extract the mass, the rigidity and input matrices. In order to evaluate at real time the shape of the flexible or composite structures, an algorithm was developed to determine the forms of the structures under arbitrary loads and different boundary conditions. The results obtained by this method were compared with those obtained from numerical, the finite elements and experimental methods. The results also, show that the developed algorithm makes it possible to correctly estimate the structures