جستجوی مقالات مرتبط با کلیدواژه "piezoelectric patches" در نشریات گروه "مکانیک"

This paper presents a study concerning active vibration control of a smart flexible spacecraft during attitude maneuver using thrusters and reaction wheels (RW) in combination and piezoelectric (PZT) sensor/actuator patches. The large-angle maneuver and residual vibration of the spacecraft are controlled using an extended Lyapunov-based design (ELD) and strain rate feedback (SRF) theory for a two-mode mission. The single-axis fully coupled nolinear rigid-flexible dynamic of the system is derived applying a Lagrangian approach and Finite Element Method (FEM). The overall stability of the system including energetic terms covering a hub and two flexible appendages, torsional spring, RW, and PZT dynamics, has been proved and the control law has been derived accordingly. A pulse-width pulse-frequency (PWPF) modulation is used to alleviate the excitations of high-frequency flexible modes. However, due to the fast maneuver, there are still residual vibrations in the system. Hence, the SRF algorithm using PZT is applied to prepare further vibration suppression. A great feature of the proposed hybrid actuator system is the switching time of the thrusters and RW, which is based on total system energy. The numerical results for a flexible spacecraft with large-angle, agile, and precise maneuver requirements through a comparative study verify the merits of the proposed approach.

This paper presents a study concerning active vibration control of a smart, flexible spacecraft during attitude maneuver using thrusters/ a reaction wheel and piezoelectric patches. The large-angle maneuver and residual vibration of the spacecraft are controlled utilizing an extended Lyapunov-based design (ELD) and strain rate feedback (SRF) theory. The single-axis fully coupled rigid-flexible dynamic of the system is derived applying a Lagrangian approach and Assumed Mode Method (AMM). The system's overall stability, including energetic terms covering a hub, two flexible appendages, PZT sensor/actuator, RW dynamics, and torsional spring, has been proved, and the control law has been derived accordingly. A pulse-width pulse-frequency (PWPF) modulation is used to alleviate the excitations of high-frequency flexible modes. However, due to the fast maneuver, there are still residual vibrations in the system. Hence, the SRF algorithm using PZT is applied to prepare further vibration suppression. The performance of the proposed extended controller is compared to the conventional Lyapunov and pole placement control algorithms. The numerical results for simultaneously large angle attitude and vibration control of a flexible spacecraft through a comparative study verify the merits of the proposed approach.

Exploiting the nonlinear nature of structural damage through piezoelectric patches is one of the latest concepts of early detection of damage. Support loosening as one of the prevalent defects in engineering systems is a source of contact acoustic nonlinearity. Vibro-acoustic modulation has proven to be a promising method for revealing structural nonlinearity characteristics. Requiring a large number of cycles to be solved in the time domain to reach the steady-state before evaluating the results in the frequency domain, makes using existing computational methods such as finite element method to model this phenomenon very expensive. This paper is concerned with a novel numerical method called Fourier spectral element to investigate the vibro-acoustic modulation in the Euler-Bernoulli beam caused by contact nonlinearity. Three piezoelectrics were attached to the beam as the probe, pump and sensor. The numerical outcomes are compared against the experimental results to check the validity of the developed method. The results show that the Fourier spectral element not only provides a high convergence rate but is also capable of simulating the phenomenon of modulation with sufficient accuracy.

In this paper, control of forced vibration amplitude of a rotating FGM conical shell is studied using FGPM patches. Four piezoelectric patches are placed inner and outer of the shell. In order to obtain the system dynamic equations, the energy method and the classical plate theory are used and simply supported boundary conditions are considered. Each system variable is considered as an expression by separation of variables with variable-time coefficients. Subsequently by substitution the considered responses in the energy functions and finally using the Lagrange equation, the governing equations of the system are obtained. Natural frequencies are compared with the result of previous researches in the case of non-rotating and rotating shell. Also to control vibration, velocity feedback is used so that sensor voltage, which is dependent on the surface, thickness, and location of each sensor, is calculated and used in the actuator voltage. In the following section, control of the system is done for first mode and then convergent system, which in both cases, Closed-loop system well dampens amplitude of forced vibrations.

Employing nonlinear dynamic signature of the host structure for early damage detection and remaining useful life estimation purposes, is an emerging idea in the area of piezoelectric patches based structural health monitoring. Clamped support loosening is one of the defects that not only may cause disorder in system’s functioning, but also obstruct damage identification process through distorting the signals. In this study, support loosening induced contact acoustic nonlinearity (CAN) behavior was monitored by vibro-acoustic modulation (VAM) technique. Using miniaturized PZT patches with the capability to be installed on the host structure permanently for both pump and probe actuation as well as sensing the modulated signal, enabled online monitoring via VAM technique. An appropriate filter was designed to eliminate the unintentionally excited natural frequencies and to reveal the sidebands. In this study, the sensitivity of modulation strength to the pump excitation frequency was also investigated. According to the results, appearance of sidebands around the central probe frequency is an appropriate indicator for CAN identification. In order to study the mechanism of modulation phenomenon, a coupled field electromechanical finite element (FE) model was developed. Proper matching of the numerical and experimental results indicates sufficient accuracy of the developed FE model and its potential to predict the modulation behavior.

The active vibration control of a smart cantilever rotary beam, using dual sensor and actuator piezoelectric patches stuck on the outer surface of the beam, is studied. Motion equations are discretized by finite element method with 6 and 9 DOF elements for parts without piezoelectric patches and with them, respectively. Several types of controllers such as LQR, LQG and rate feedback controller are employed to actively control vibrations of the beam. Simulation results exhibit a better performance in terms of settling time for the LQR controller due to all states’ feedback; while rate controller is only relying on the sensor patches for feedback which is convenient in terms of cost. Also, the effect of the number of piezoelectric patches is studied.

In this paper, the response of simply supported flexible core sandwich beam with piezoelectric patch, under uniform harmonic loading with and without the control is analyzed. Sandwich beam is modeled using three-layer sandwich beam theory. Governing equations of motion are obtained using Hamilton’s principle, based on Euler–Bernoulli beam theory for face-sheets and linear displacement field theory for soft core. By defining suitable state variables in time domain and using Galerkin’s method, the state space equations of system are derived from governing equations of motion. Controller is designed using LQR technique. Dynamic response and frequency response of beam in open and closed loop configuration are obtained and the effect of flexible core on the control of dynamic response is investigated. The obtained results show that the controller can play an important role toward damping out the vibration of the sandwich beam. Also, it is shown that the %18 difference between vibration amplitudes of top and bottom face sheets, because of the flexibility of the core, affects the position of piezo actuator and sensor.