To enhance the low-frequency distributed vibration control capabilities for lightweight thinwalled structures, this study reports a piezoelectric meta-plate with nonlinear semi-active electrical stiffness tuning. The ...
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To enhance the low-frequency distributed vibration control capabilities for lightweight thinwalled structures, this study reports a piezoelectric meta-plate with nonlinear semi-active electrical stiffness tuning. The proposed meta-plate consists of mechanical and electrical sections, with piezoelectric coupling at their interface. The distributed nonlinear semi-active enhanced SSDV shunting circuits are in the electrical domain, utilizing the piezoelectricity to affect the dynamic equivalent bending stiffness of the whole plate structure. Results show that the nonlinear semi-active electrical stiffness tuning of the proposed meta-plate can induce broadband electromechanical band gaps and enhance wave attenuation through band gap hybridization. The existence of these band gaps and their coupling effects are indirectly demonstrated by the metaplate vibration transmission characteristics. In the case of a thin-walled meta-plate with a 1x5 array of periodic cells, there are 13 vibrational transmission modes within the 0-2 kHz range, with 12 significantly attenuated. The majority of vibration transmission modes are attenuated by more than 10dB, reaching a maximum of 64dB Additionally, the obtained equivalent damping ratio of the semi-active enhanced SSDV electrical circuit is below 0.4, so the nonlinear semi-active enhanced SSDV electrical shunt circuits are underdamped and exhibit high control stability. Therefore, the proposed semi-active distributed vibration control approach also has better robustness and reliability.
The issue of output constraints is studied for a flexible-link manipulator in the presence of unknown spatially distributed disturbances. The manipulator can be taken as an Euler-Bernoulli beam and its dynamic is expr...
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The issue of output constraints is studied for a flexible-link manipulator in the presence of unknown spatially distributed disturbances. The manipulator can be taken as an Euler-Bernoulli beam and its dynamic is expressed by partial differential equations. On account of the uncertainty of disturbances, we present a disturbance observer to estimate infinite dimensional disturbances on the beam. The observer is proven exponentially stable. Considering the problem of output constraints in the practical engineering, we propose a novel distributed vibration controller based on the disturbance observer to fulfill the position regulation of the joint angle and suppress elastic deflections on the flexible link, while confining the regulating errors of output in a suitable scope that we can assign. The closed-loop system is demonstrated exponentially stable based on an integral-barrier Lyapunov function. Simulations validate the effectiveness of the design scheme.
In the recent development of active structural systems and microelectromechanical systems, piezoelectrics are widely used as sensors and actuators, Because of the limitations of theoretical and experimental models in ...
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In the recent development of active structural systems and microelectromechanical systems, piezoelectrics are widely used as sensors and actuators, Because of the limitations of theoretical and experimental models in design applications, finite element development and analysis are proposed and presented in this paper, A new laminated quadratic CO piezoelastic triangular shell finite element is developed using the layerwise constant shear angle theory, Element and system equations are also derived, The developed piezoelastic triangular shell element is used to model 1) a piezoelectric bimorph pointer and 2) a semicircular ring shell, Finite element (triangular shell finite element) solutions are compared closely with the theoretical, experimental, and finite element (thin solid finite element) results in the bimorph pointer case, Natural frequencies and distributedcontrol effects of the ring shell with piezoelectric actuators of various length are also studied, Finite element analyses suggested that the inherent piezoelectric effect has little effect on natural frequencies of the ring shell. vibrationcontrol effect increases as the actuator length increases, and it starts leveling off at the seven-patch (70%) actuator, Coupling and control spillover of lower natural modes are also observed.
Light-activated shape memory polymer (LaSMP) is a novel actuator with dynamic Young's modulus and strain when exposed to ultraviolet lights, which can be used in noncontact vibrationcontrol. This study focuses on...
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Light-activated shape memory polymer (LaSMP) is a novel actuator with dynamic Young's modulus and strain when exposed to ultraviolet lights, which can be used in noncontact vibrationcontrol. This study focuses on the vibrationcontrol effect of LaSMP patches on hemispherical shells with free boundaries. An LaSMP strain variation model is presented with experimental verifications. Based on the strain model, the control forces of LaSMP patches on hemispherical shells are introduced. The FEM method is used to obtain natural frequencies of the free hemispherical shell by solid modeling in ANSYS and proved by comparing numerical results with analytical and experimental results. Using the modal expansion method, the LaSMP vibrationcontrol of hemispheres is investigated, and independent modal responses are presented and evaluated. The results indicate that LaSMP patch can controlvibrations of hemispherical shells by reducing vibration amplitudes. And the control effect is better for low modal vibration, as the LaSMP-induced strain is relatively smaller. By establishing the relationship between LaSMP actuator forces and modal amplitude reduction, this study offers an analytical tool and procedure for future LaSMP application to vibrationcontrols of flexible structures.
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