The dispersion curves(phase velocity and electromechanical coupling coefficient)of ZnO(aplane)/sapphire(r plane)structure are obtained by theoretical calculation.A SAW filter with ZnO/sapphire structure is designed based on the calculating results.The SAW filter prototype is fabricated by depositing ZnO film on sapphire substrate and then fabricating chip.In the process,the a-plane ZnO thin film has been grown.Three SAW modes of the thick film sample,named mode 0,mode 1and mode 2,are measured.The measured center frequency of mode 0and mode 1and mode 2is 1 073.79 MHz,1 290.63 MHz and 1 572.3 MHz respectively.The measured phase velocity of mode 0and mode 1and mode 2is 3 865.67m/s,4 646.25m/s and 5 660.27m/s respectively.
In order to address the problem of the severe non-linearity in the self-alignment loop of the platform when the large angle misalignment exists on the stationary base,a new large angle self-alignment algorithm of HRG is designed based on the unscented particle filter(UPF),and the numerical simulation and rotating platform simulation have been carried out.The results show that the superiority of this algorithm which made a contribution to the application of the HRG to the initial platform will be demonstrated through theoretical analysis,digital simulation and experimental results.
A method of frequency synthesis has been present at the X-Band with low phase noise based on a highovertone bulk acoustic resonator(HBAR).According to the working principle of HBAR,using a HBAR and sound table filters consist of oscillating loop with low phase noise,which can directly generate S-band signal.X-band signal can be obtained by quadruplicated frequency module.This method serried with SAW filter has raised out-of-band noise suppression.The phase noise at the frequency of 2.2GHz reaches-118.9dBc/Hz@1kHz,and the phase noise of 8.8GHz at X-band is-107.4dBc/Hz@1kHz after quadruplicated frequency.
The PT/PZT(PbTiO_3/Pb(Zr_(0.52)Ti_(0.48))O_3)multilayered thin films deposited on Pt/Ti/SiO_2/Si substrates is prepared by Sol-Gel method.The influence of different annealing time on the nanostructure,crystal orientation and phase change characteristics is analyzed.The influence of different annealing time on nanostructure using FESEM and on the crystal orientation and phase change characteristics using XRD and Raman are measured separately.The test result reveals that at elevated annealing time,the thin film will transform from trigonal phase into tetragonal phase,and have a preferred orientation of(110).The optimized annealing time is found to be 20 min,at which the thin film possesses perfect crystallization,uniform grain size and pure perovskite phase.It is expected that this kind of thin film can be used in MEMS devices.
2-2PZT/Epoxy piezoelectric composite materials with parallel model was prepared by pouring processing,and the performance of composite was investigated.The results indicated that the optimal proportion between epoxy resin and polyamide resin 650 was 4∶1,and was then cured at room temperature for 3~5days.With the increase of frequency,dielectric loss tanδdecreased and stabilized.The piezoelectric constant d33,dielectric constanteand dielectric loss tanδincreased with PZT volume content.At 1kHz maximum piezoelectric constant d33 reached to 146.5pC/N,dielectric constantewas 2 100 and dielectric loss tanδwas 0.090.The bending strength of162.2 MPa and deflection of 6% ~10% for PZT/Epoxy composite materials could be achieved respectively when volume fraction of PZT was 63.5%.
In order to further refine the fuel atomization particle size,agasoline nozzle was designed based on the one-dimensional vibration theory.The vibration modal and harmonic responses were analyzed with the finite element method to obtain the resonant frequency and the frequency of vibration displacement and stress distribution,the theoretic frequency of 30.157 kHz was nearly equal to the measured frequency of 30.862 kHz of the HP-4286 A LCR precision impedance instrument.Furthermore,theoretical analysis and experimental research for the nozzle atomization effect of gasoline were done,theoretical calculation of particle size of?24.38μm were basically consistent with the measured particle size of?27.62μm,the size was reduced about 2times compared with the size(about?50μm)of traditional gasoline injector.The results show that the device can effectively improve the atomization quality and fuel efficiency of gasoline,and provide technical reference for the design of the engine fuel injector.
Aluminum nitride(AlN)films with c-axis orientation were grown on(111)Si substrates by laser molecular beam epitaxy.The current transport mechanisms and the density of interface state of Au/AlN/Si MIS structure were studied.The AlN/Si heterojunctions exhibited a typical rectifying characteristic,which was attributed to the space-charge-limited current mechanism.The ideality factor was 2.88 and the interface state density of AlN/Si was about 1.1×10~(12) eV~(-1)·cm~(-2),mainly distributed in 0.26 eV distancing the top of valence band of Si,and consisted of O impurities,N vacancy and Al—Si bond formed from Si atoms in place of N atoms during the AlN films growth.
The beam path of Michelson interferometer was adjusted to make sure that the responsive voltage rates of the photoelectric probe was consistent with that of the triangular wave slaving voltage,and to keep maximum peak to peak value.By continuously changing the slaving voltage,the related changes in responsive voltage and extension offset.dependence on driven voltage was find.When measuring the harmonic response features,peak to peak value rates of responsive voltage and that of extension offset are used and compared.
Zn0.7Co0.3(Ti1-xSnx)Nb2O8(x=0.1,0.15,0.2,0.25,0.3,0.35)microwave ceramics were prepared by traditional solid-state reaction method.The influences of Sn substituted for Ti on the phase constitution crystal structure and microwave dielectric properties of Zn0.7Co0.3(Ti1-xSnx)Nb2O8ceramics were also discussed.The XRD patterns revealed the main phase of ZnTiNb2O8 and little substitution content of Zn0.17Ti0.5Nb0.33O2.With further substitution of Sn,the lattice constant,volume and density of the ceramics increased,the ceramics structure also became tight showed by SEM.Tremendous improvement of Q×fvalue while a declining trend oferandτf were obtained with increasing xvalue.Appropriate substitution value(x=0.35)would conduct excellent microwave dielectric properties(er=30.5,Q×f=46 973 GHz,τf=-45.4×10-6/℃)sintered at 1 080 ℃.
In order to reduce the effect of hysteresis nonlinearity of piezoelectric ceramic on the tracking accuracy of the system,the classical PI hysteresis model which can be analyzed inversely is adopted to build the model of the piezoelectric ceramic in this paper.The PI hysteresis inverse model is used in the feed-forward control algorithm and the Neural PID feed-back control algorithm is designed.The feed-forward control algorithm is combined with the Neural PID feed-back control algorithm and then the compound control algorithm is attained.Let the feed-forward Control algorithm and the compound control algorithm run on the controller and experiment proves that the tracking error of the feed-forward control algorithm is 1.256μm and the tracking error of the compound control algorithm is0.092μm.The tracking accuracy has an improvement of 1.164μm by the compound control algorithm.
Aiming at the demand of the impact monitoring on stiffened composite panel,a fast impact load detection method based on distributed optical fiber grating sensing network is proposed.Optimization allocation of the FBG sensor is realized,different rank energy distributing trend of impact response signals are obtained by using the wavelet packet,the sample response matrix is constructed based on the ratio of the the amplitude ratio of the specific energy spectrum.Based on the above research,the impact detection of stiffened composite panel can be realized by BP neural network.
The static time drift of MEMS accelerometer was studied through theory and experiments,and a BM wavelet packets general regression neural network(GRNN)was developed to compensate the drift.The first,the error of the drift was removed by the wavelet packet based on the Birge-Massert improved function,the second,the zero drift model of the MEMS accelerometer was established based on GRNN,which has a good approximation capability,fast learning speed and excellent network stability.The computer results show that this model can compensate the zero drift effectively.Comparing with the original data,compensation with least square fitting and compensation only by GRNN,the mean values of zero drift is reduces by 97.4%,67.8%,67.8% respectively;the variance reduces by 87.4%,87.5%,90.9%,respectively.The delay time of the model is 10-5s.The results illustrate the feasibility and validity of the Birge-Massert wavelet packers general regression neural network model.
In order to collect the vibration energy when cars through the road,a vibration generation device based on piezoelectric materials is designed to transform vibrational energy into electricity,collecting maximum vibration energy from the environment.For purpose of absorbing the maximum external energy,the following research is completed.The influence of the deformation of piezoelectric material to generate electricity is analyzed,and a model which can find the minimum deformation of piezoelectric materials to produce maximum electricity is designed.A hybrid circuit model mainly in parallel and secondly in series is made based on the analyzing of the influence of the link method of piezoelectric patches to the electrical energy output.A piezoelectric generation device is made and experiments show the power of electrical energy output is 0.061 2 W,capacitors store electrical power is0.026 4 W,power generation efficiency is 14.42%,and capacity storage efficiency is 6.21%.
The principle,design and fabrication process of the high overtone bulk acoustic resonator(HBAR)which can generate the comb-spectrum signal with the operating frequency of about 10 GHz at UHF band are presented in the paper.Also,the resonator with Au/Cr/ZnO/Au/Cr/YAG/Cr/Au/ZnO/Cr/Au two-port structure is designed,and the Qvalue of experimental sample is more than 23 000 at the resonance frequency of 2.240 137 GHz.The future work will focus on ZnO film growth,HBAR design modification and Qvalue improvement.
Sound source location has a wide application in the military,industrial noise location and other areas;the beam-forming based on microphone array is the main method for sound source localization.MVDR algorithm has a greater advantage compared to conventional beam-forming algorithms,however,MVDR algorithm has a large amount of calculation and general processor can not meet the real-time requirement.Considering the characteristics of huge data and complex operations in the procession of beam-forming,the fixed-point DSP chip TMS320DM642 produced by TI Company is selected.Mixed by C and Assembly Language,the application of uniform circular array of eight microphones on TMS320DM642 DSP based MVDR algorithm can be realized.The processing speed is much faster than on the Advanced RISC Machines(ARM),with the features of high speed,high precision and strong practicability.
Cameras are the front-end equipments of the video surveillance system in substation,Their reasonable stationing is important for not only remote surveillance but also safety and reliable operation of the substation.Stationing rule base is based on substation 3Dvisual scene.Under the base,we can calculate and display the surveillance range of the camera in 3Dscene as well as give the numbers and the positions of cameras installed in substation.Thus,cameras installation of the whole substation is automatically built.A intelligent cameras stationing is realized.The test results show that the system has a high application value in eliminating the surveillance hidden danger effectively,improving the remote surveillance system and maintenance technology of substation and raising the efficiency of remote inspection and intelligent linkage.
To improve the precision of piezoelectric ceramic actuator in adjusting the length of optical resonant cavity,a driving system of piezoelectric ceramic actuator was designed;meanwhile,in order to improve the hysteresis of piezoelectric ceramic,the hysteresis model was established by using the Duhem model.The hysteresis model has been obtained by using the gradient descent method to identify the model parameters.The actuator was controlled by using the inverse model compensation and PID method.The experimental result indicates that the Duhem model can effectively fit the hysteresis of the actuator,and the maximum error is less than 0.2μm in a range of 15μm;and in the compound control,the maximum error of the actuator is nearly 12 nm,this indicates the effectiveness of the compound control method.
Focused on the coning error compensation algorithm of RLG strapdown SINS,an attitude algorithm which is different from conventional one is researched,and a class of new algorithm based on interval-sample is proposed in this paper.The correlation analysis of each angle increment outputted by gyroscope with its vicinal ones is conducted in this new algorithm.Then according to the correlation analysis result,the data is selected from the section most approximate to infinitesimal rotation and ameliorate the rotation vector.The attitude algorithm result indicates that the new method has better performances on compensation accuracy and convergence property comparing with the conventional one.
Due to its passive and long-life characteristic,surface acoustic wave(SAW)temperature sensor has been widely concerned and applied.In order to ensure the accuracy of the SAW temperature sensor,the precise and effective calibration should be implemented.Because wireless signal-to-noise ratio has an impact on the echo frequency variance,it is important to acquire the accurate functional relationship between the resonating frequency and temperature using the minimal temperature point.In this paper,based on frequency statistical characteristics of the echo signal,the relationship between the calibration accuracy and the number and position of temperature point is discussed by using Monte-Carlo simulation;the measurement accuracy of 1% within the full scale of sensor is realized.Otherwise,aone-point calibrationmethod is proposed to eliminate the influence of position variation between the sensor reader and the sensor after installation.
In this paper,PbMoO4 and TeO2normal acousto-optical deflectors with center frequency of 100 MHz and operating at laser length of 0.632 8μm.The size design parameters of two deflectors are given.The characteristics of deflectors are analyzed through maximum diffraction efficiency,bandwidth,transit time and other performance characteristics and curves obtained from the simulation of two deflectors on MATLAB software.The simulation result shows that TeO2 deflector has an improvement on characteristics comparing with PbMoO4 deflector.
