Xing Shen

Vibration control laws via shunted piezoelectric transducers: A review

Attaching a piezoelectric transducer to a vibrating structure, and shunting it with an electric circuit, gives rise to different passive, semi-passive, and semi-active control techniques. This paper attempts to review the research related to structural vibration control, via passive, semi-passive, and semi-active control methods. First, the existing electromechanical modeling is reviewed, along with the modeling methods. These range from lumped parameters, to distributed parameters modeling of piezostructural systems shunted by electrical networks. Vibration control laws are then discussed, covering passive, semi-passive, and semi-active control techniques, which are classified according to whether external power is supplied to the piezoelectric transducers, or not. Emphasis is placed on recent articles covering semi-passive and semi-active control techniques, based upon switched shunt circuits. This review provides the necessary background material for researchers interested in the growing field of vibration damping and control, via shunted piezostructural systems.

Free standing Pt–Au bimetallic membranes with a leaf-like nanostructure from agarose-mediated electrodeposition and oxygen gas sensing in room temperature ionic liquids

In order to overcome the difficulty of recycling and reusing the Pt–Au bimetallic particles in their supports during a catalytic process, and some problems in electrochemistry (that is, many development steps in an assay, high background signals, reliability and robustness of surface structures), a free-standing Pt–Au bimetallic membrane with impressive a leaf-like nanostructure was synthesized using agarose-mediated electrodeposition. The membrane is characterized by SEM, TEM, EDS, and XRD. The Pt–Au membrane electrode is tested by CV measurements. The membrane electrode presents very low background currents. The sharp nanoedges and nanotips on the membrane might offer many active centers for catalysis. Sensing behavior is reported for oxygen, O2, in various room temperature ionic liquids using Pt–Au electrode.

Self-powered synchronized switch damping on negative capacitance for broadband vibration suppression of flexible structures

Synchronized switch damping (SSD)techniques using piezoelectric materials have been used by different researchers for many years for the structure vibration control. In these techniques, a piezoelectric patch is bonded on or embedded into the vibrating structure and connected to or disconnected from a network of electrical components through an electronic switch, which is controlled by a digital signal processor (DSP), in synchronous with the structure motion. Recently, Self-powered SSD techniques have emerged in which the DSP is replaced by a low pass filter, thus making the whole system self-powered. The control performance of the previously used Self-powered SSD techniques heavily relied on the electrical quality factor of the shunt circuit, thus limiting their control performance as the electrical quality factor could not be increased beyond certain limit. However, in order to bypass the influence of the electrical quality factor on the control performance, a new Self-powered SSD technique has been proposed in this paper in which the inductance in the previous Self-powered SSD techniques has been replaced with a negative capacitance thus making the whole circuit capacitive without resonance. However, it is found that the voltage on the piezoelectric patch can still be inverted. In order to access the control performance of the proposed technique in comparison with the previous Self-powered SSD techniques, experiments are performed on a cantilever beam subjected to both single mode and multimode excitations. Keeping the value of negative capacitance slightly greater than the inherent capacitance of the piezoelectric patch gave the optimum damping performance. Experiments results confirmed the effectiveness of the proposed technique as compared to the previous SSD techniques.

Study of Large-Displacement Actuators Made of Antiferroelectric Ceramics and Its Integration with SMA

A new type of large-displacement actuator called RAINBOW (Reduced And Internally Biased Oxide Wafer) was fabricated by a chemical reduction of PSZT antiferroelectric ceramics. It is found that PSZT was easily reduced and the optimal conditions for producing RAINBOW samples were determined to be 870°C for 2∼3 hours. The AFE-FE phase transitions occur at lower field strength for these reduced antiferroelectric ceramics compared with normal ones. Larger axial displacement (about 190 μm) were obtained from the samples. Furthermore, the possibility of the integration between antiferroelectric ceramics and SMA was also explored. PVD (Physical Vapor Deposition) method was applied to depose SMA (shape memory alloy) films on the reduced layers of the ceramic patches. Experimental results show that this integrated material has better mechanical properties and SMA films do contribute actuation to the whole composite actuating structure. So the integration method for these two kinds of functional materials is a reasonable idea to manufacture actuators with better performance.

Active Noise Isolation of a Plate Structure Without Using Acoustic Sensors

In this study, an improved system of active noise isolation without using acoustic sensors is used to suppress the noise transmission through a plate structure. The system used in this study is an improvement of the system proposed by the authors in an earlier study, in which the sound pressure of the noise radiated from a GFRP plate is estimated from the voltage signals of the piezoelectric elements embedded in the plate by using the Rayleighs integral formula and the estimated sound pressure is used as the feedback signal in the control system. Owing to the large estimation error, the former method is only partially successful, that is, it is effective for some of the resonance frequencies, but not for the others. In this study, a neural network is used instead of the Rayleighs integral formula. The control system consists of a neural network identifier and an adaptive feedback controller using the filtered-X LMS algorithm for feedback control. Experimental results show that the estimated sound pressure of the radiated noise agrees well with the sound pressure measured directly by a microphone. The new noise isolation system without using acoustic sensors exhibits the same noise control performance as the conventional system using microphone sensors. It also exhibits better noise control performance than the vibration control system, which directly uses the signals from the piezoelectric elements as feedback.

Characterization and Microstructure of PLZT RAINBOW Ceramics

Abstract A new type of large displacement actuating materials called RAINBOW (Reduced and Internally Biased Oxide Wafer) ceramics is fabricated by a chemical reduction of PLZT piezoelectric ceramics. It is found that PLZT is easily reduced and the thickness of reduced layer has a linear relationship with the reduction time. The optimal conditions for producing RAINBOW samples from PLZT are determined to be 950°C for 1-1.5 hours. SEM micrograph shows that the RAINBOW ceramics are composed of reduced and unreduced layer obviously. And the reduced layer is transgranularly fractured while the unreduced ceramic is intergranularly fractured. Metallic lead and refractor oxides (PbO, ZrO2, Zr-TiO4, etc.) are found in the reduced layer by XRD analyses, however, the crystal structure of PLZT is not found. The analysis of the reduction mechanism is in good accordance with experimental data.

Power output and efficiency of a negative capacitance and inductance shunt for structural vibration control under broadband excitation

Structural vibration control using a piezoelectric shunt is an established control technique. This technique involves connecting a piezoelectric patch, which is bonded onto or embedded into the vibrating structure, to an electric shunt circuit. Thus, vibration energy is converted into electrical energy and is dissipated through a network of electrical components. Different configurations of shunt have been researched, among which the negative capacitance-inductance shunt has gained prominence recently. It is basically an analog, active circuit consisting of operational amplifiers and passive elements to introduce real and imaginary impedance on the vibrating structure. The present study attempts to model the behavior of a negative capacitance-inductance shunt in terms of power output and efficiency using circuit modeling software. The shunt model is validated experimentally and is used to control the structural vibration of an aluminum beam, connected to a pair of piezoelectric patches, under broadband excitation. The model is also used to determine the optimal parameters of a negative capacitance-inductance shunt to increase the efficiency and predict the voltage output limit of op-amp against the supply voltage.

Study of RAINBOW Actuator and its Intergation with SMA

A new kind of large-displacement piezoelectric actuator — reduced and internally biased oxide wafer (RAINBOW) actuator composed of reduced and unreduced layers, is prepared from PZT (Pb(ZrxTi1-x)O 3) by chemical reduction. Its phase components, microstructure, and actuating properties are also researched. It is found that the displacement of reduced RAINBOW PZT is three times larger than that of the traditional PZT; however, re-oxide phases are found in the reduced layer of composite PZT, showing that the reduction procedure needs to be improved. Furthermore, the possibility of the integration between PZT and shape memory alloy (SMA) is explored. Physical vapor deposition (PVD) method is applied to depose SMA films on the reduced layer of RAINBOW PZT patches. Results of mechanical and actuating experiments show that this kind of integration is a reasonable idea to manufacture actuators with better performance.A new kind of large-displacement piezoelectric actuator - reduced and internally biased oxide wafer (RAINBOW) actuator composed of reduced and unreduced layers, is prepared from PZT (Pb(ZrxTi1x)O3) by chemical reduction. Its phase components, microstructure, and actuating properties are also researched. It is found that the displacement of reduced RAINBOW PZT is three times larger than that of the traditional PZT; however, re-oxide phases are found in the reduced layer of composite PZT, showing that the reduction procedure needs to be improved. Furthermore, the possibility of the integration between PZT and shape memory alloy (SMA) is explored. Physical vapor deposition (PVD) method is applied to depose SMA films on the reduced layer of RAINBOW PZT patches. Results of mechanical and actuating experiments show that this kind of integration is a reasonable idea to manufacture actuators with better performance.

Study of a reduced and internally biased oxide wafer PZT actuator and its integration with shape memory alloy

Large displacement piezoelectric actuators of a new kind?RAINBOW (reduced and internally biased oxide wafer) actuators, which are composed of reduced and unreduced layers?were prepared from PZT (Pb(ZrxTi1?x)O3) by chemical reduction. The distribution of stress inside the RAINBOW structure and its actuating properties were both studied. It is found that the optimal ratio of reduced layer thickness for the RAINBOW structure is 0.3; reduced RAINBOW PZT has a lower resonance frequency and a three-times-larger displacement than traditional PZT; furthermore, the possibility of integration of PZT and SMA (shape memory alloy) was also explored. The PVD (physical vapor deposition) method was applied to deposit SMA coatings on the reduced layers of RAINBOW PZT patches. Results of mechanical and actuating experiments show that this is a reasonable idea for manufacturing actuators with better performance.

Study of RAINBOW Actuators Made of PSZT

Abstract A new type of large-displacement actuator called RAINBOW (Reduced And Internally Biased Oxide Wafer) was fabricated by a chemical reduction of PSZT antiferroelectric ceramic. It is found that PSZT was easily reduced and the optimal conditions for producing RAINBOW samples were determined to be 870°C for 2∼3 h. The AFE-FE phase transitions occur at lower field strength in RAINBOWs compared with normal PSZT. Larger axial displacement (about 190μm) was obtained from the RAINBOWs by application of electric fields exceeding the phase switching level. The field-induced displacement of the RAINBOWs is dependent on the manner of applying the load on the samples.