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To prevent flutter phenomena in a wind turbine, minimize vibration and increase the blades' life, a systematic analysis is required to investigate the effects between the cyclic aerodynamic loads and the structural performance of the turbine. A dynamic analysis of a straight-bladed vertical axis wind turbine (SB-VAWT) blade is investigated in this paper, and a simplified approach for the energy equations of an Eulerian beam subjected to twist and transverse bending deflections is introduced. The aerodynamic loads are estimated using the double multiple stream tube models. They are introduced into the dynamic model in the aeroelastic coupling, where the structural displacements are fed back to update the aerodynamic loads by utilizing the average acceleration method for the numerical integration of the equations. Reduced order modeling is then imposed based on the first modes of vibration. It is found that the structural displacement has little effect on the aerodynamic loads, and SBVAWTs experience higher transverse displacements compared with those in curved-blade VAWTs.

In this paper, an on-line closed-loop identification of mainly mass and inertia of an under-actuated aerial vehicle, namely a quadrotor acting as an aerial manipulator, is presented. Being treated as a rigid body, only one set of eighteen- or six tri-axial linear accelerometers is used to facilitate such estimation. Force and torque disturbances acting upon the vehicle during identification are also estimated which will refine the overall estimation quality of the unknown parameters. Namely, recursive linear and nonlinear least squares methods are used to obtain initial and refined estimations, respectively. Random disturbances are introduced to the closed-loop system to ensure enough excitation of the overall system. Issues related to identifiability, stability and performance are discussed. Since the proposed method depends on general kinematical and dynamical analyses of motion, it is claimed that the presented method will be also applicable to a wider range of, mainly, aerial vehicles. [ABSTRACT FROM AUTHOR]

The present investigation focuses on the design and mathematical modeling of a microelectromechanical (MEMS) mode-localized based sensor/actuator system. This device incorporates a sensitive clamped–clamped shallow arch microbeam with an initial curvature shaped to resemble one of the first two symmetric and asymmetric modes of free oscillations of a clamped–clamped beam. The analysis reveals that with a suitable arrangement of the initial shape of the device flexible electrode and a proper tuning of the maximum initial rise and the actuating dc load enables the transition to display certain bistable behavior. This could be a better choice to build a device with a large stroke. Furthermore, the generated data showed the occurrence of mode-veering, indicating a coupling between the concerned symmetric and asymmetric modes of vibrations, and offering the possibility for such a device to be used as a mode-localized MEMS-based sensor utilizing veering and crossing phenomena. Indeed, where a certain energy is exchanged between symmetric and asymmetric modes of a microbeam, it can be utilized to serve as a foundation for the development of a new class of highly precise resonant sensors that can capture, with a certain level of precision, any of the sensed signal amplitudes. [ABSTRACT FROM AUTHOR]