Acceleration Feedback Control Strategy Research Articles

Improvement of the band-gap characteristics of active composite laminate metamaterial plates

The characteristics of vibration frequency band-gaps for the composite laminate metamaterial plates are improved by equidistantly placing macro-fiber composite (MFC) piezoelectric patches along one direction of the plates. An acceleration feedback control strategy is proposed to actively regulate the band-gap characteristics of the metamaterial plates. The spectral element method (SEM) and transfer matrix method are used to calculate frequency response curves and attenuation constants of the metamaterial plates, and the calculated results by the SEM are compared with that of the finite element method (FEM) to validate the correctness and accuracy of the present numerical method. The obtained results demonstrate that when lattice constant of the structure is properly designed, superior band-gap properties in the low and medium frequency ranges can be achieved by adjusting the dimensions of the MFC piezoelectric patches. Improved characteristics of the Bragg scattering band-gaps in the medium and high frequency regions can also be obtained using the acceleration feedback control strategy. Moreover, band-gap widths can be significantly enlarged by actively tuning the acceleration feedback gain. In addition, the starting frequencies and band-gap widths of the composite laminate metamaterial plates can be adjusted using different cross-ply angles of the MFC piezoelectric patches and composite laminate metamaterial plates.

Effect of feedback on PID controlled active structures under earthquake excitations

In this paper, different feedback control strategies are presented for active seismic control using proportional-integral-derivative (PID) type controllers. The parameters of PID controller are found by using an numerical algorithm considering time delay, maximum allowed control force and time domain analyses of shear buildings under different earthquake excitations. The numerical algorithm scans combinations of different controller parameters such as proportional gain (<TEX>$K_p$</TEX>), integral time (<TEX>$T_i$</TEX>) and derivative time (<TEX>$T_d$</TEX>) in order to minimize a defined response of the structure. The controllers for displacement, velocity and acceleration feedback control strategies are tuned for structures with active control at the first story and all stories. The performance and robustness of different feedback controls on time and frequency responses of structures are evaluated. All feedback controls are generally robust for the changing properties of the structure, but acceleration feedback control is the best one for efficiency and stability of control system.

The stability analysis and active control of a composite laminated open cylindrical shell in subsonic airflow

The stability analysis and active control of a composite laminated open cylindrical shell in subsonic airflow are conducted using piezoelectric material. The equation of motion of the shell with piezoelectric patch is derived from Hamilton’s principle and transformed into the ordinary differential equations using Galerkin’s method. The linear potential flow theory is applied to derive the aerodynamic pressure. The displacement and acceleration feedback control strategies are used to obtain the active stiffness and mass by applying an appropriate external control voltage to activate the piezoelectric patch. The natural frequencies of the system are calculated, from which the flow velocity for the open cylindrical shell under instability can be obtained. The effects of the ply angles of the shell and the feedback control gains on the stability properties of the structural system are discussed. From the results, it can be seen that when the flow velocity becomes sufficiently high, the open cylindrical shell exhibits instability of the divergence type and the instability velocity decreases with the increase in the ply angle. The stability of the system can be improved by the displacement feedback control strategy. With the increase in the displacement feedback control gain, the instability velocity of the system increases. For the acceleration feedback control strategy, the instability velocity of the system remains unchanged, which illustrates that the active mass induced by the acceleration feedback has no effect on the instability velocity of the composite laminated open cylindrical shell.

Control of sound and vibration of fluid-filled cylindrical shells via periodic design and active control

The wave propagation, vibration transmission and acoustic emission characteristics in the passive and the active periodic shell systems are investigated. A finite element method (FEM) is utilised to conduct the investigation. In the passive periodic shell, two pivotal frequencies (i.e., the cut-off frequency of the periodic shell, and the resonant frequency of flexural vibration of shell ring), which are existed in an arbitrarily high circumferential mode, are found; the frequency range is divided into three regions by these two frequencies. Various band formation mechanisms and the dynamic properties within the three frequency regions are illustrated, with the aid of a series of vibration deformations. Furthermore, an active periodic shell is constructed. Several control methods, such as inverted displacement-, velocity- and acceleration-feedback control strategies, are explored for the active shell. Under these control strategies, the effects of negative stiffness, damping coefficient and mass modulation, can be produced, thus enabling the band gap generable and its characteristics, such as their bandwidth, location and attenuation coefficient, adjustable. The pressure level of the structure-borne sound is also suppressed along the shell within the band gaps.

Nature of seismic control force in acceleration feedback

Active control methods have been applied to numerous civil structures in recent years. A significant amount of the research on active control methods has been based on full-state feedback using the linear quadratic regulator (LQR) control algorithm; because measurement of the full state (i.e., the displacements and velocities of all DOFs) is difficult, such algorithms are impractical in full-scale implementations. Output feedback strategies based on measured acceleration at a limited number of points has been proposed and validated. However, a thorough understanding of the dissipative nature of the associated control forces and the way in which these forces protect the structure have been elusive. This paper considers the hysteric behavior of the control forces produced by the widely employed linear quadratic Gaussian (LQG)-based acceleration feedback control strategies and explores parallels with the pseudo-negative stiffness (PNS) semi-active damping systems. Numerical simulation studies carried out on one-story and three-story buildings with active bracing show that the LQG-based algorithms are quite versatile and can produce controllers with a variety of behaviors, including the PNS, depending upon the control objectives chosen. Copyright © 2012 John Wiley & Sons, Ltd.

Active aeroelastic flutter suppression of a supersonic plate with piezoelectric material

The active aeroelastic flutter properties of supersonic plates are investigated by using the piezoelectric material. The piezoelectric material has been extensively used for the active vibration control of engineering structures. In this paper, the piezoelectric material is further used to improve the flutter characteristics of the supersonic plates. The equation of motion of the plate and piezoelectric material system is obtained by Hamilton’s principle with the assumed mode method. The supersonic piston theory is used to evaluate the aerodynamic load. By applying an appropriate external control voltage to activate the piezoelectric material, a displacement and acceleration feedback control strategy is used to obtain the active stiffness and active mass. Solving the eigenvalue problem of the equation of motion, the natural frequencies and damping ratios of the structural system are obtained. Furthermore, the aeroelastic flutter bounds are calculated, and the effects of feedback control gains on the active aeroelastic flutter characteristics of the structure are analyzed in detail. From the numerical results it is seen that the active stiffness and active mass have prominent effects on the flutter characteristics of the supersonic plates. The aeroelastic flutter properties can be greatly improved by introducing the active stiffness and active mass into the supersonic plate with the piezoelectric patch. With the increase of the feedback control gains, the active aeroelastic flutter properties for the lower order modes of the supersonic plate are gradually improved.

Improving the Aeroelastic Flutter Characteristics of Supersonic Beams Using Piezoelectric Material

The active aeroelastic flutter characteristics of supersonic beams are investigated. The main contribution of this research is that the piezoelectric material is used to increase the flutter velocities of the supersonic beams. A modeling approach based on the conventional theory of structural dynamics is employed. The process of deriving equations is not complicated and easy to understand. This methodology is verified to be accurate and effective. Hamilton’s principle with the assumed mode method is used to develop the equation of motion of the structural systems. The supersonic piston theory is adopted to evaluate the aerodynamic pressure. Using the standard eigenvalue methodology, the solutions for complex eigenvalue problem are obtained. A displacement and acceleration feedback control strategy is used to obtain the active stiffness and active mass. The aeroelastic flutter bounds are obtained by calculating the natural frequencies and damping ratios. The effects of the active stiffness and mass on the flutter properties of the supersonic beams are analyzed. From the numerical results, it is seen that by adding the active stiffness and mass to the supersonic beams, the aeroelastic flutter properties can be effectively improved. Especially, if the acceleration and displacement feedback gains are increased to proper values, the flutter can even be eliminated for the supersonic cantilevered beams.

Fault tolerant structural control systems for civil engineering applications

AbstractThe objective of this work is to experimentally examine some practical issues relating to the reliability and performance of active structural control systems. Using the newly constructed shaking table in the Department of Structural Mechanics at the University of Pavia, experiments were conducted employing an actively controlled, three story test structure. A DC‐motor based active mass driver system was used as the active control device. An H2/LQG controller based on acceleration feedback is applied to the system. The first objective of this work is to demonstrate the efficacy of the acceleration feedback control strategy. Next, two experiments are conducted with the goal of investigating fault tolerant control system design. In the first case, the occurence of a sensor failure is simulated experimentally, and the resulting controlled performance and robustness characteristics are assessed. The second set of tests is to evaluate the ability of the controller to reduce the structural responses when reduced information is available for control action determination. Both of these issues are important practical concerns in the design and implementation of a structural control system.

Acceleration Feedback Control of MDOF Structures

To date, most of the current active structural control strategies for aseismic protection have been based on either full-state feedback (i.e., all structural displacements and velocities) or on velocity feedback. However, accurate measurement of displacements and velocities is difficult to achieve directly in full-scale applications, particularly during seismic activity, since the foundation of the structure is moving with the ground. Because accelerometers can readily provide reliable and inexpensive measurement of accelerations at strategic points on the structure, development of control methods based on acceleration feedback is an ideal solution to this problem. The purpose of the present paper is to demonstrate experimentally that acceleration feedback-control strategies are effective and robust, and they can achieve performance levels comparable to full-state feedback controllers.