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The input electrical impedance behaves as a capacitive when a piezoelectric transducer is excited near its resonance frequency. In order to increase the energy transmission efficiency, a series or parallel inductor should be used to compensate the capacitive impedance of the piezoelectric transducer. In this paper, the effect of the series matching inductor on the electromechanical characteristics of the piezoelectric transducer is analyzed. The dependency of the resonance/anti-resonance frequency, the effective electromechanical coupling coefficient, the electrical quality factor and the electro-acoustical efficiency on the matching inductor is obtained. It is shown that apart from compensating the capacitive impedance of the piezoelectric transducer, the series matching inductor can also change the electromechanical characteristics of the piezoelectric transducer. When series matching inductor is increased, the resonance frequency is decreased and the anti-resonance unchanged; the effective electromechanical coupling coefficient is increased. For the electrical quality factor and the electroacoustic efficiency, the dependency on the matching inductor is different when the transducer is operated at the resonance and the anti-resonance frequency. The electromechanical characteristics of the piezoelectric transducer with series matching inductor are measured. It is shown that the theoretically predicted relationship between the electromechanical characteristics and the series matching inductor is in good agreement with the experimental results.

We report a detailed study on the structural, microstructural, piezoelectric, dielectric and AC conductivity of Bi0.5(Na1−xKx)0.5TiO3 (BNKT; x = 0, 0.1, 0.2 and 0.3) ceramics fabricated by a conventional solid-state reaction method. XRD and Raman analysis revealed that Bi0.5(Na0.8K0.2)0.5TiO3 and Bi0.5(Na0.7K0.3)0.5TiO3 ceramics exhibit a mixture of rhombohedral and tetragonal structures. The segregation of K at the grain boundary was confirmed by transmission electron microscopy and is related to typical microstructural local compositional mapping analysis. Two transitions, at ∼ 330°C and 150°C, observed from the ε′ versus T curve in pure BNT are associated with the ferroelectric tetragonal to paraelectric cubic phase (TC) and ferroelectric rhombohedral to ferroelectric tetragonal phase (Td), respectively. Further, the TC and Td shifted towards the lower temperature with a rise in K concentration. Frequency dispersion of Td and TC suggest that BNKT ceramics exhibit a weak relaxor behavior with diffuse phase transition, which is confirmed by Uchino–Nomura criteria and the Vogel–Fulcher law. The AC resistivity ρac(T) follows the Mott variable range hopping conduction mechanism. A significant enhancement of dielectric and piezoelectric properties were observed for x = 0.2 system: dielectric constant (ε′ = 1273), dielectric loss (tanδ = 0.047) at 1 kHz, electromechanical coupling coefficients (kij: k33, kt ∼ 60%, k31 ∼ 62% and kp ∼ 46%), elastic coupling coefficients (S33D = 6.40 × 10−13 m2/N and S33E = 10.06 × 10−13 m2/N) and piezoelectric constants (d33 = 64.23 pC/N and g33 = 5.69 × 10−3 Vm/N).

The high-static-low-dynamic-stiffness (HSLDS) isolator is sensitive to mass deviation, which causes a shift in static equilibrium and results in softening of the dynamic response. This study introduces sliding mass inertia (SMI) to an HSLDS to mitigate the softening and enhance the dynamic performance of the system under mass deviation. The harmonic balance method (HBM) is employed to obtain the dynamic response of the vibrating system with the proposed nonlinear isolator. Key characteristics, such as the backbone curve, amplitude-frequency response, resonance peak, and displacement transmissibility are analyzed in detail through parametric analysis. The results indicate that mass deviation worsens the softening behavior of the HSLDS isolator. A higher mass deviation ratio results in an increase in both the amplitude and the resonance frequency of the system. Fortunately, however, the sliding mass eliminates the softening behavior, reduces the peak response, and improves the overall dynamic performance.

The vibration isolation system is now indispensable to high-precision instruments and equipment, which can provide a low vibration environment to ensure performance. However, the disturbance with variable frequency poses a challenge to the vibration isolation system, resulting in precision reduction of dynamic modeling. This paper presents a velocity self-sensing method and experimental verification of a vibration isolation system. A self-sensing actuator is designed to isolate the vibration with varying frequencies according to the dynamic vibration absorber structure. The mechanical structure of the actuator is illustrated, and the dynamic model is derived. Then a self-sensing method is proposed to adjust the anti-resonance frequency of the system without velocity sensors, which can also reduce the complexity of the system and prevent the disturbance transmitting along the cables. The self-sensing controller is constructed to track the variable frequency of the disturbance. A prototype of the isolation system equipped with velocity sensors is developed for the experiment. The experiment results show that the closed-loop transmissibility is less than −5 dB in the whole frequency rand and is less than −40 dB around, adding anti-resonance frequency which can be adjusted from 0 Hz to initial anti-resonance frequency. The disturbance amplitude of the payload can be suppressed to 10%.

In the semiconductor manufacturing industry, the dynamic model of a controlled object is usually obtained from a frequency sweeping method before motion control. However, the existing isolators cannot properly isolate the disturbance of the inertial force on the platform base during frequency sweeping (the frequency is between 0 Hz and the natural frequency). In this paper, an adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system (DSA-SAVIS) is proposed. This system has a significant anti-resonance characteristic; that is, the vibration amplitude can drop to nearly zero at a particular frequency, which is called the anti-resonance frequency. The proposed controller is designed to add an adjustable anti-resonance frequency to fully use this unique anti-resonance characteristic. Experimental results show that the closed-loop transmissibility is less than −15 dB from 0 Hz to the initial anti-resonance frequency. Furthermore, it is less than −30 dB around an added anti-resonance frequency which can be adjusted from 0 Hz to the initial anti-resonance frequency by changing the parameters of the proposed controller. With the proposed controller, the disturbance amplitude of the payload decays from 4 to 0.5 mm/s with a reduction of 87.5% for the impulse disturbance applied to the platform base. Simultaneously, the system can adjust the anti-resonance frequency point in real time by tracking the frequency sweeping disturbances, and a good vibration isolation performance is achieved. This indicates that the DSA-SAVIS and the proposed controller can be applied in the guarantee of an ultra-low vibration environment, especially at frequency sweeping in the semiconductor manufacturing industry.

The test specimen in environmental vibration test is connected to the fixture through several attachment points. The forces generated by the shaker must be transmitted equally to all attachment points. The forces transmitted to attachment points, however, are different because of the flexural vibration of the fixture. The variations of the transmitted force cause the undertest, especially at anti-resonance frequencies, in vibration test control. Anti-resonance frequencies at the attachment points of the fixture must be same in order to avoid the under-test in vibration test control. The structural modification of the fixture is needed so that anti-resonance frequencies at attachment points have the same value. In this paper, the method to calculate the anti-resonance frequencies and those sensitivities is presented. This sensitivity analysis is applied to the structural modification of the fixture excited at multi-points by the shaker. The antiresonance frequencies at the attachment points of the fixture can have the same value after structural modification, and the under-test in the vibration test control can be removed. Several computer simulations show that the proposed method can remove the under-tests, which are not removed in conventional vibration test control.