The surface acoustic wave(SAW) frequency domain reader based on the frequency step continuous wave(FSCW) uses the principle similar to that of vector network analyzer(VNA) for measuring the frequency domain response to resolve the echo information of the SAW tag. Firstly, the theoretical derivation of frequency domain sampling principle based on FSCW is carried out to guide the design of the reader’s parameters. Then, by combining the direct digital synthesizer(DDS) and the IQ modulator with the built-in phase locked loop (PLL), a fast frequency-converting transmit chain is designed, and a bidirectional coupler and a hardware IQ demodulation chip are used in the receive chain to realize quadrature coherent mixing, which realizes the stable measurement of the absolute phase. Finally, the circuit board of the reader is actually made, and the performance of the reader is tested with the SAW tag. By comparing with the measured results of the VNA, it is showed that the reader designed in this paper is effective.

This paper designs a miniaturized ultra-wideband Balun filter based on the low-temperature co-fired ceramic (LTCC) technology. The Balun filter consists of a fifth-order bandpass filter and a Marchand Barron-based modified Barron cascade. The bandpass filter is designed as a wideband high rejection Barron filter using a coupled resonant design method, and an innovative inductive cascade topology is used between the second, third and fourth order resonance, thus the relative bandwidth of 48% or even wider has been realized. The coupling between the Balun input and output uses a parallel stacked coupling spiral transmission line, which greatly enhances the coupling between transmission lines and widens the bandwidth of the Balun. The Balun filter passband is 1.71~2.76 GHz,and the insertion loss is less than 2.3 dB.At 50~669 MHz, the rejection is greater than 35 dB,at 669~1 245 MHz, the rejection is greater than 17 dB,at 3 205~3 400 MHz, the rejection is greater than 27 dB,and at 3 400~6 000 MHz, the rejection is greater than 30 dB. The phase difference and amplitude difference of the signals of the two output ports are 180°±15°(1 710~2 340 MHz), 180°±10°(2 500~2 760 MHz) and ±1.0 dB, respectively. The proposed filter has high versatility and good market application prospects.

As the core element of various surface acoustic wave (SAW) devices, the performance of SAW resonator determines various specifications of SAW devices, among which the quality factor (Q) of resonator is the most important. The factors affecting the Q value of SAW resonators are introduced in this paper. It is pointed out that most of the substrate structure of SAW resonator with high Q is heterogeneous acoustic layer structure, and the heterogeneous acoustic layer structure is essentially one-dimensional phononic crystal. The results show that the Q value of the resonator can be improved by constructing phononic crystals at multiple positions to fully 3-D constrain the acoustic field energy of SAW resonator. Finally, the possible ideal structure of SAW resonator with high Q in the future is prospected.

In this paper, a double mode surface acoustic wave (DMS) filter based on 128°YX-LiNbO3 piezoelectric material is designed. The two-dimensional device model of DMS filter is obtained by using the coupling of mode (COM) model to carry out the theoretical analysis, and the single-stage DMS filter is obtained by using COMSOL to carry out the simulation of the two-dimensional device. In order to eliminate the shoulder peak appearing at the low-end near stop band of the DMS filter, this paper proposes to coat a layer of SiO2 film on its surface to form a temperature compensation structure. The results show that the designed DMS filter has a center frequency of 891.0 MHz, minimum insertion loss of -1.29 dB, 1 dB bandwidth of 34.0 MHz, fractional bandwidth of 3.8%, rectangular coefficient of 2.94 and out-of-band rejection of about -20 dB.

The surface acoustic wave (SAW) devices are widely used in extreme environmental sensing. Lanthanum gallium silicate(LGS) is a commonly used high-temperature piezoelectric crystal, but at high temperature, the strain glue cannot effectively transmit strain due to the bonding force. The transition layer thin film technology for the strain sensing at high temperature is studied in this paper. A new method and process technology of the transition layer thin film are proposed, which can realize the effect of more stable strain transition of the high temperature strain glue. The results show that the use of sputtering Al re-oxidation can significantly improve the bonding force between LGS and high-temperature glue, so as to realize good strain transfer. A super-large-scale measurement of 1 000 με is realized at 500 ℃ by using this transition layer.

For the ice detection of aerospace composite materials, a solution based on ultrasonic guided waves technology is proposed in this paper. The layered structure waveguide model is established by using the transfer matrix method, the dispersion curves of the phase velocity and group velocity are drawn, and the propagation characteristics of ultrasonic guided waves in the carbon fiber reinforced polymer (CFRP) plate are analyzed.On this basis, the hardware circuit composed of signal source and receiver is designed based on the field programmable gate array.The ice detection system and its experimental environment are set up in combination with the thermotank. By measuring the relative time delay of the echo signal wave packet, the feasibility of the ultrasonic guided waves ice detection scheme is verified, which provides a new idea for the field of aircraft ice detection.

The quartz crystal microbalance(QCM) is a mass-sensitive sensor with the advantages of high sensitivity and short response time. In order to expand the application of QCM technology in the field of liquid phase biomolecular sensing, a streptavidin-sensitive QCM sensor was successfully fabricated by electrochemically depositing the biomolecule-functionalized conducting polymers on the surface of QCM. The sensor can not only simultaneously realize the mass and electrochemical sensing of the streptavidin, but also has excellent anti-inteference ability against othor proteins. It has the potential to be further applied to liquid phase biochemical sensing and disease detection.

This paper introduces a 2.7 μm acousto-optic Q-switched device with high damage threshold. With comparison and analysis of several commonly used near-infrared acousto-optic materials, the lithium niobate crystal is a preferred medium material for the Q-switched device, which can provide suitable compromise among diffraction efficiency, optical performance, and resistance to laser damage. This paper also analyzes the relationship between Q value of the laser cavity and the diffraction efficiency. The purpose of reducing the driving power and improving the turn-off capability is achieved by optimizing the distribution of diffraction efficiency. This 2.7 μm acousto-optic Q-switched device made of lithium niobate crystal has an operating wavelength from 2.7 μm to 2.8 μm, an operating frequency of 40.68 MHz, an optical aperture of 3 mm, and a diffraction efficiency of 75% at the center part of the through hole. Compared with the acousto-optic Q-switched device made of tellurium oxide, the 2.7 μm acousto-optic Q-switched device made of lithium niobate crystal has higher laser damage resistance.

he sensory organs are essential for many animals, especially for those creatures living underwater. In this paper, a surface four-electrode PVDF piezoelectric fiber biomimetic flexible sensor was designed and fabricated using polyvinylidene fluoride(PVDF) as the material, imitating the tentacles of aquatic animal seals. The excitation source is used to test the performance of the prepared sensor, including outputting different waveforms to test the perception of different excitations, the perception of hydrodynamics and the perception of the directions of underwater moving objects. The experimental results show that the sensor has good sensing performance for different excitations; the speed detection limit reaches 0.15 mm/s, and has good directional detection ability. It has great application prospects for the underwater situation perception.

A side-hole fiber microfluidic sensor based on dual long-period fiber grating(LPFG) is proposed in this paper. The side-hole fiber (SHF) has two air holes, which are natural microfluidic channels, and the microfluidic sensor can be temperature compensated. The dual LPFGs are written on the side-hole fiber by a CO2 laser, and their resonant wavelengths are 1 268.7 nm and 1 385.8 nm, respectively. The experimental results show that, when the sensor is placed in a glycerol aqueous solution with a refractive index of 1.335~1.395, the refractive index sensitivities of the two LPFG resonance peaks are -88.724 nm/RIU and -79.474 nm/RIU, respectively, and the temperature sensitivities are 52.0 pm/℃ and 55.7 pm/℃, respectively. The sensing matrix of the sensor can be derived by using the refractive index and temperature sensitivity. The proposed microfluidic sensor with temperature compensation has good linear responsivity and can realize the simultaneous measurement of refractive index and temperature, which has potential value in the fields of environmental monitoring and food safety.

A tunable piezoelectric driven resonant mass sensor based on modal localization is proposed to detect the external mass disturbances in this paper. The detection structure of the mass sensor is composed of two cantilever beams with different lengths connected by mechanical coupling beams. Firstly, the theoretical modeling of asymmetric resonant element driven by piezoelectric actuator was carried out by using Hamiltonian principle and solved by Galerkin method. The vibration characteristics of the first two modes were obtained. The natural frequencies obtained by the theoretical solution are basically consistent with the COMSOL simulation analysis and experimental data comparison. Different experimental studies have shown that the detection range of the resonator without tuning mass was 2~10 mg, and the detection range of the resonator with tuning mass was increased to 1~13 mg, and the resolution of quality detection was also optimized. In addition, the nonlinear analysis of the structure of the sensor was carried out, and it was found that the detection sensitivity of the resonator under super harmonic vibration has been improved by 80%, which provided a basis for the design of the nonlinear resonance sensors.

In the wind tunnel experiment, the friction of the aircraft surface is less than 0.1% of the air pressure. For the measurement of surface friction in small area and small range, there is a contradiction between the accuracy and the reliability of the force balance. In order to solve the above problems, a two-dimensional force piezoelectric sensor which can amplify and measure the milli-newton level surface friction is designed based on the lever principle and the piezoelectric effect of quartz. The test performance is evaluated by the static calibration experiment and dynamic pulse excitation experiment. The experiments show that the measuring range of the sensor can be as low as 50 mN, both the nonlinearity error and repeatability error are lower than 1%, and the natural frequency is 2 428 Hz,which can meet the measurement requirements of surface friction in wind tunnel tests.

The PZT-52 piezoelectric ceramic column was prepared in this paper. The interdigitated electrodes were fabricated on the surface of piezoceramic substrate by screen printing, and the printing process flow of cylindrical ceramic surface electrodes was studied. The polarization tests of the samples were carried out using the oil bath thermal polarization method. By testing the free axial displacements of the actuators, the effect of the polarization time on the displacements of the piezoceramic actuator was studied. And the influence principle of polarization time on the domain turning and silver electrode forming quality was analyzed. The results show that the axial displacement increases gradually with the increase of polarization time. When the polarization voltage is 500 V, the polarization tempaerature is 110 ℃, and the polarization time is 60 min, the maximum displacement of the actuator is 0.30 μm.

In order to reduce the influence of the dynamic hysteresis characteristics of the piezoelectric micro-positioning stage on the positioning accuracy, a feedforward controller based on the rate-dependent inverse hysteresis model is designed to compensate the hysteresis. Firstly, the dynamic model of the stage is established on the basis of force analysis and motion analysis. Secondly, the Modified Prandtl-Ishilinskii(MPI) model is obtained by improving the classical Prandtl-Ishilinskii(PI) model, and the separated rate-dependent MPI model is obtained by connecting the MPI model in series with the linear dynamic model of the stage, and then the feedforward controller of the stage is established based on the rate-dependent MPI inverse model. Finally, the step response experiments and sinusoidal trajectory tracking experiments on the designed controller are carried out. The experimental results show that the designed controller has good positioning accuracy and tracking performance, and can effectively compensate the dynamic hysteresis errors of the piezoelectric micro-positioning stage.

In order to reduce the hysteresis nonlinearity of piezoelectric actuators and improve the positioning accuracy of microsystems, a piezoelectric drive power with the adaptive inverse control is designed in this paper. The signal conditioner, the Boost circuit of the front stage DC-DC and the single-phase full-bridge inverter circuit of the post stage DC-AC were analyzed and designed using the model TMSF320F28335 digital signal processing (DSP) chip. The functions of SPWM drive signal generation, AD sampling of displacement signals, and Prandtl-Ishlinskii adaptive inverse model have been realized by programming under the CCS6.0 software development environment. To validate the adaptive control performance of the designed piezoelectric drive power, the driving control experiments based on the adaptive inverse have carried out with piezoelectric ceramic actuator. The experimental results show that the root mean square error(RMSE) at 1Hz is 3.239 5 μm and the average error of mean absolute error (MAE) is 2.985 1 μm without the control. With the increase of frequency, the maximum values of RMSE and MAE at 20Hz are 21.402 9 μm and 19.306 2 μm, respectively. By using the piezoelectric drive power with the adaptive inverse control, the RMSE is 0.324 9 μm and the MAE is 0.265 6 μm at 1 Hz, and the RMSE is 12.639 μm and the MAE is 11.956 1 μm at 20 Hz.

Aiming at the nonlinear characteristics of rate-dependent hysteresis of piezoelectric stack actuators, a BP neural network rate-dependent hysteresis modeling method based on the Asymmetric unilateral backlash (aubacklash) operator is proposed in this paper. Firstly, an improved aubacklash operator is proposed to improve the residual displacement at the origin and strict center-symmetry of the backlash operator of Prandtl-Ishlinskii (PI) model. Secondly, the rate-dependent memory characteristics of hysteresis of piezoelectric stack actuator are analyzed, and a rate-dependent BP neural network hysteresis model is proposed. Finally, the accuracy evaluation system of hysterectomy modeling is set up, the parameters of aubacklash operator model are identified by Levenberg-Marquardt(L-M) algorithm, and the optimal structural parameters of BP neural network model are determined. The experimental results show that the mean square error of BP neural network model is reduced by 70.90%~89.98% and the relative error is reduced by 70.69%~89.84% compared with the traditional PI model at high and low single frequency and mixed frequency, which verifies the accuracy and frequency adaptability of the model.

There are a lot of high-frequency noises in the ocean gravity measurement data, so it is necessary to use a low-pass filter to extract the actual gravity anomaly information. Combined with the measured ocean gravity data, the method of determining the cut-off frequency and length of the low-pass filter is investigated, and the FIR low-pass filters with different window functions are designed. The experimental results of marine gravimetric data processing show that both the coincidence accuracy in the repeating line and error in the intersection non-conformity value of the FIR low-pass filter processing of Hanning window and Hamming window are better than 0.5 mGal(1 Gal=10-2 m/s2）, which can meet the requirements of marine gravity measurement.

The vibration suppression system of the traditional cantilever beam has the disadvantages of complexity and low accuracy in establishing the dynamic equations. This paper proposes to use the multi-physics field coupling simulation software to build the cantilever beam system as the controlled object, and establish the controller model in Simulink by designing the proportional, integral and differential (PID) algorithm to carry out the co-simulation on the vibration control of the cantilever structures. Because of the unknown structure, the selection of PID parameters of traditional controllers is often determined by trial and error based on experience. A model for optimizing PID parameters by genetic algorithm is established to realize the online optimization of parameters to control the vibration of piezoelectric cantilever beam in real time. The effectiveness of the model is verified by the simulation and experiments. In addition, the simulation and experiment on the vibration suppression is carried out by changing the position of the piezoelectric actuator at different stress points of the cantilever beam. The results show that the algorithm model has good robustness, and the best PID tuning parameters can be obtained at different positions such that the best effect of vibration suppression can be achieved.

The piezoelectric thin film vibration sensors have developed rapidly in recent years and have been widely used in structural health monitoring, medical electronics, acceleration, device vibration and other measurements. Aiming at the performance detection of piezoelectric thin film vibration sensor, a set of calibration equipment for the sensitivity and frequency response characteristics of piezoelectric sensor is designed in this paper. The calibration equipment uses the frequency adjustable vibration table as its core part. The vibration signal is provided by the adjustable frequency vibration table, and the vibration test on the standard piezoelectric sensor and the self-made sensor is carried out simultaneously. The test results show that the equipment can easily calibrate the sensitivity and frequency response characteristics of the measured sensor. The overall design of the calibration system is simple and easy to operate. At the same time, the system has small volume, high stability and small measurement error, which is convenient for the detection of various types of piezoelectric vibration sensors, and has strong practicability and broad development space. Based on the calibration of the self-made piezoelectric thin film sensor performance by the system, the influencing factors on the sensitivity of the piezoelectric thin film sensor are studied.

The concentric ring microphone arrays are widely used in acoustic imaging array systems, which can effectively suppress the interference and determine the location of sound sources. Under the conditions of limiting the number of array elements, the maximum aperture of the array and the minimum array element spacing, a method to design the broadband low-sidelobe concentric ring microphone array using the particle swarm algorithm is proposed in this paper. In this method, by constructing a fitness function reflecting the side lobe level of the broadband signal in the scanning area, and using the radius of the ring and the deflection angle of the array elements as the joint optimization parameters, the rapid optimization solution of the array is realized based on the particle swarm optimization algorithm. The simulation experiments show that the overall side lobe level of the optimized array obtained by the proposed method is lower than that obtained by taking the highest side lobe level as the fitness function, and also lower than the optimal array obtained by optimizing only the radius of the ring, which demonstrates the feasibility and effectiveness of the optimization method.

Using COMSOL software, a simplified analysis model was established, and the finite element analysis of the support column capacitive micromachined ultrasonic transducer(CMUT) model was carried out, and it was compared with the circular cavity CMUT model. The results show that the resonance frequency of the support column CMUT model is 10 kHz and the collapse voltage is 52 V, which is suitable for the low-frequency design. Comparing the support column CMUT model with the circular cavity CMUT model, it can be seen that the former model has a larger active area, less parasitic capacitance; higher device sensitivity, lower collapse voltage, and larger amplitude of membrane, but the sound signals emitted during working will be weaker than the latter.

The monitoring of the vibration state of the coolant pump of the pressurized-water reactor (PWR) nuclear power units is one of the important tasks in the maintenance of the nuclear power plants. In this work, in view of the demands for the acceleration sensor with high temperature resistance and strong radiation resistance for the vibration state monitoring of the coolant pump of a nuclear power plant in our country, the working characteristics of piezoelectric acceleration sensor in extreme environments are studied. The experimental results show that the working temperature of the proposed sensor is up to -55~480 ℃, the radiation resistance is up to 1×106 Gy. The operating state of the sensor has been verified through the vibration bench test. The results show that the output vibration signals of the sensor are consistent with that of the 5g(g≈9.8 m/s2） and 10g standard vibration signals. A vibration monitoring scheme than meets the requirements of nuclear power field application is proposed, and has been applied to a coolant pump of a nuclear power plant in our country. The experimental results meet the needs of nuclear power plants and lay a technical foundation for future batch application.

The response characteristics of piezoelectric cantilever under ultra-low amplitude excitation were studied through the electromagnetic excitation. Firstly, the response of the linear piezoelectric beam was studied experimentally, and the influence of excitation amplitude were analyzed. Then, the nonlinear response characteristic of the piezoelectric beam with unilateral stopper was investigated, and the influences of excitation amplitude and gap size on the broadband response of the piezoelectric beam with the unilateral stopper were analyzed. The experimental results showed that the amplitude of the piezoelectric beam was less than 140 μm under electromagnetic excitation of 0.003 N. The piezoelectric beam with a unilateral stopper showed a piecewise linear response and was sensitive to the micron scale change of the gap size. As the gap decreased from 100 μm to 20 μm, the maximum output voltage decreased from 3.14 V to 1.17 V, and the half-power bandwidth increased from 5.8 Hz to 18.2 Hz.

A logging-while-drilling(LWD） quadrupole composite transmitting transducer based on metal substrate structure is designed in this paper. The frequency domain and time domain acoustic responses of transducer are numerically simulated by the finite element method. The effects of the collar structure and excitation pulse width on its acoustic characteristics are investigated. A practical transmitting transducer is fabricated and encapsulated for the experimental test in the anechoic water tank. The test results show that the resonant frequency, emission voltage level and horizontal directivity of the transmitting transducer are in good agreement with the numerical simulation results. The transducer has a first-order bending vibration mode near the frequency of 4.7 kHz, and its emission voltage level can reach 126.2 dB. Therefore, it has the characteristics of low frequency and high power radiation, and can meet the requirements of the quadrupole acoustic logging-while-drilling.

The sleeve grouting connection is the main connection method of the stressed steel bars in the current prefabricated buildings, and the grouting quality is one of the key factors affecting the performance of prefabricated reinforced concrete structures. In this paper, an active detection method for the sleeve grouting defects based on the stress wave measurement by using the driving and sensing functions of piezoelectric ceramic materials is proposed, and the feasibility is verified by experiments, and its mechanism is analyzed by the numerical simulation. The piezoelectric ceramic patches are pasted on the surface of the sleeve connecting steel bars to measure the output signals of the piezoelectric ceramic sensors on the healthy specimen and the specimen with defects with different sizes, and the wavelet packed energy(WPE) is analyzed and compared. The results show that the grouting defects lead to an increase of the voltage amplitude of the output signals of the piezoelectric ceramic sensors, and the WPE index is related ot the size of the sleeve grouting defect. The proposed method can effectively detect the grouting defects in the sleeve.

The micro-particle manipulation technology, with its precise control, low cost, simplicity and high efficiency, has broad application prospects in biomedical engineering and micro-nano device manufacturing. The traditional control methods have shortcomings in the control of non-magnetic, non-conductive and high-density solid micro-particles. Therefore, this paper proposes a micro-particle manipulation system based on the low-frequency vibration of piezoelectric cantilever beam, which uses the flow at the bottom of the flow field to realize the aggregation of micro-particles. The aggregation microscopic test shows that the spherical alumina particles at the bottom of the culture dish move and aggregate towards the target region due to the bottom flow field excited by low-frequency vibration of piezoelectric vibrator, and reach a stable state at 122 s. The image processing of test results show that the aggregation area of the micro-particles is up to 79 405 μm2. The proposed manipulation method can realize the aggregation of high-density micro-particles and the aggregation range is large, which can provide a technical reference for the manufacturing of micro-nano devices.

Aiming at the vibration problem of piezoelectric cantilever beams, a fuzzy sliding mode active control strategy is proposed so as to reduce the buffeting based on the suppressing of the vibration of cantilever beams. The state space equation of the piezoelectric cantilever beam is established by introducing the state vector into the motion equation of the homogeneous beam element and the piezoelectric beam element. The order of the piezoelectric cantilever beam model is reduced by the equilibrium truncation method so as to improve the calculation efficiency, and the fuzzy sliding mode controller is designed based on the reduced-order model. The buffeting phenomenon introduced by the sliding mode control can be reduced effectively by using the fuzzy rule to adjust the switching gain and using the saturation function to replace the sign function, and its stability is proved by using the Lyapunov function. The results show that the fuzzy sliding mode control based on the saturation function can not only control the vibration of piezoelectric cantilever, but also reduce the buffeting phenomenon.

A circular patch antenna with annular coupling is proposed in this paper. Using the circular metal patch as the radiation patch of the antenna, two new resonant bands are generated by introducing two resonant rings onto the dielectric plate. By adjusting the height between the circular patch and the coupling ring, the operating frequency band of the antenna is further broadened. The irregular dielectric substrate is processed by 3D printing technology, which effectually solves the problems of difficult processing and long production cycle of traditional processing methods. The measured results show that the return loss is less than -10 dB in the operating frequency band of 3.8~5.8 GHz. At 5.1 GHz, the antenna gain reaches 8.4 dBi. The relative bandwidth of the antenna is 42%, and it has good omnidirectional radiation characteristics. The measured results are in good consistent with the simulation ones.

This paper proposes a new type of circular ring traveling wave linear ultrasonic motor with incomplete teeth. The motor’s movable slider is pressed against the end face of the tooth structure on the outer surface of the circular ring vibrator under a certain pre-pressure, four piezoelectric ceramic plates are evenly distributed at 90° intervals on the inner side of the circular structure, and four sets of driving teeth are arranged at 45° intervals from the position of the piezoelectric ceramic plates. When the motor is in operation, only one driving tooth works, and the service life of the ultrasonic motor can be increased by rotating the different working teeth. The motor operates with two in-plane third-order bending modes that are orthogonal to each other at the same frequency. The dynamic design and simulation of the vibrator was carried out using ANSYS finite element software, the effect of the structure parameter on the mode is analyzed. A prototype is fabricated and the vibration characteristics and output performance are tested. The experimental results show that the motor runs smoothly at the excitation voltage peak-to-peak value of 240 V, excitation frequency of 30.459 kHz and the pre-pressure of 0.6 N, with the maximum output force of 90 mN and motor no-load speed of 102 mm/s.

The piezoelectric actuators with local ring electrodes were fabricated by screen electrode printing, and its driving force was tested and studied. A clamping force test platform was built to test and analyze the radial clamping force of the piezoelectric actuators with local ring electrodes and the conventional electrode piezoelectric actuator. The experimental results show that under the excitation of square wave and sine wave with a frequency of 0.2 Hz and a peak value of 200 V, the peak values of radial clamping force in the electrode region of piezoelectric actuators with local ring electrodes are 0.60 N and 0.58 N, respectively. And the peak responses of the two clamping forces are 2.72 and 2.76 times higher than those of the conventional electrode piezoelectric actuator respectively. The peak values of the reverse clamping force in the electrodeless area are 0.29 N and 0.28 N, which are slightly larger than those of the conventional piezoelectric actuators. The experimental results also verify the orthogonality of the piezoelectric actuators with local ring electrodes.

The influence of the misalignment angle between the dither axis and sensitive axis of the mechanically dithered ring laser gyro on the gyro accuracy is analyzed theoretically. Based on the Euler dynamics equation of rigid body, the dynamic model of mechanically dithered ring laser gyro is established. The change of the product inertia of the gyro cavity caused by the misalignment angle of dither axis in gyro coordinates is calculated by the calculation method of the moment of inertia of the rigid body about an arbitrary axis. When the gyro dithers at high frequency, the lateral moment generated by the inertial product of the cavity causes the lateral deformation of the gyro sensitive axis, and then triggers the single-gyro-level coning error. This process has been quantitatively calculated in this work. The results show that the misalignment angle of gyro dither axis should be less than 5′ in high-precision applications.

The concrete-filled steel tubes (CFST) structures are increasingly widely used in super high-rise buildings. Due to inadequate construction quality control and the shrinkage of concrete materials, the mechanical behavior is negatively affected by the possible concrete core defect and the interface debonding between the concrete and the steel tube. In this paper, for the purpose of detecting the defects in CFST, the piezoelectric ceramic plate is mounted on the surface for measurement, and the influences of these two internal defects on the responses of the piezoelectric ceramic plate on different test paths are tested and numerically simulated. By comparing the output signals of the piezoelectric sensors on different detection paths of different specimen that are healthy and have concrete core defect and interface debonding defect, the effects of the defects on the stress wave propagation are investigated and the sensing range of detection with the patch and catch method is obtained. The results show that the proposed method can effectively detect the effects of the concrete-filled steel tube, and the determination of the sensing range provides a reference for the sensor arrangement in engineering application.

With the development of helicopter technology, there is an urgent need for quality inspection and research on a new type of helicopter blade iron-clad structure. The outer layer of the iron-clad structure is stainless steel, the middle layer is rubber and heating elements and the inner layer is glass fiber. The four types of typical structures that need to be classified and identified are the upper layer debonding defect, the heating element, the lower layer debonding defect, no defect and no heating element, but this kind of iron-clad structure has more layers, thinner layer thickness, more categories to be identified than the common multilayer structures, and the ultrasonic waves will have serious aliasing in this structure. Therefore, the propagation law of ultrasonic waves in the thin-walled multi-layer structure is studied, and a new ultrasonic reflection spectrum model of the iron-clad structure is established. The tested stainless, rubber, sound speed of the glass fiber, acoustic impedance, and frequency-attenuation coefficient curve, frequency spectrum of the 2.25 MHz and 5 MHz probes is brought into the model for simulation. The simulation results show that the 2.25 MHz probe can identify four structures of the iron-clad iron, and the 5 MHz probe can identify the other three structures except for the lower layer defects. The actual test results verify the simulation results of the new model.