Towards solving the problem that ultrasonic ranging studied in the past was difficult to reach sub-millimeter accuracy in long-distance ranging. In this paper, after analyzing principles of ranging, a system based on the cross-correlation algorithm and an ultrasonic synchronous transceiver platform had a 192 kHz high sampling rate was designed. First, an ultrasonic transceiver platform was designed as a USB audio system with a sound card as the core. Second, a reverse design idea was introduced into the FPGA software to design the accurate clock system, to achieve 192 kHz high sampling rate and transceiver synchronization. Third, to improve the accuracy and stability of ranging, a valid method was proposed to eliminate the jitter of real-time cross-correlation peaks based on this platform. Finally, we conduct extensive experiments, the results show that the range median error is only 0.95 mm in the range of 4.2 m.
Thermal pollution is one of the most urgent issues in the fields of ultra-precision measurement and manufacturing, which presents the demand of producing ultra-precision circulating cooling water (CCW) with the temperature stability up to millikelvin level and response time at hundred-second level. In this paper, an ultra-precision CCW producing method based on model identification and fuzzy-PID control is proposed and illustrated. A structure of circulating water loop with ultra-precision temperature control is proposed. A cooling module using of thermoelectric cooling device arrays as refrigerator and a heating module using electrical heating-tubes as heater are employed. A control algorithm based on fuzzy-PID is designed, and a variety of model identification experiments has been carried out to extract key parameters of the modules. Experimental results show that a temperature stability up to ±3mK is achieved, the temperature control resolution is better than 5mK, and the adjusting time of 1K step is 128s, satisfying the urgent need of ultra-precision measurement and manufacturing.
During proposal and development of a new non-contact nano-probe based on tunneling effect, analysis of the bias electric field (BEF) distribution is a key step for modeling and characterization of the probe. However, the BEF between the spherical electrode serving as the probing ball and the surface to be measured has combined features of macro- and micro- dimensions, which makes the modeling of it a far tricky problem. In this paper, a modeling finite difference method (FDM) based on non-uniform grids generation according to the structural features of the BEF is proposed, and the field distribution is solved with high accuracy. The maximum relative calculation error is within 15% compared with calculation results for a bias electric field with regular boundary with analytical electric image method.
In order to solve the problem of performance analysis and optimal design of flexible suspension structure for displacement measurement probing sensors, a novel theoretical model of stiffness with high accuracy is proposed. Both displacements constraint and angle constraint of elastic diaphragms are considered during modeling, and a stiffness equation including all dimensional parameters and material characteristics of elastic diaphragms is obtained. Thus the stiffness of the flexible suspension structure is modeled theoretically and accurately, and the influence on performance of probing sensors by each parameter can be analyzed. Simulations results show that the theoretical model of stiffness proposed is more accurate than existing models, and performance analysis and optimal design of probing sensors can be carried out based on it.
Based on the theoretical model of Airy spot, a method is proposed for improving the imaging speed from confocal microscopy. The virtual Airy spot is designed for obtaining the pattern on CCD at detecting plane. Here the size of the spot is determined by the parameters of imaging system and intensity data from point detector, which can receive data quicker than CCD. The treatment can improve the speed of imaging comparing with CCD at receiving end. The virtual structured detection is also utilized for generating high-resolution image. Some numerical simulation results are provided for demonstrating the validity of the proposed method.
KEYWORDS: Sensors, Spherical lenses, Chemical elements, Algorithm development, Environmental sensing, Control systems, Thermal energy technology, Temperature metrology, Structural design, Fluctuations and noise
In order to solve the problem of thermal drift and further improve the performance for sensors with extreme demand for precision, based on analysis of shortcomings of existing compensation methods and characteristics of thermal drift, a novel active suppression technology against thermal drift is proposed. Considering the change of properties of reference elements in sensors caused by temperature variation is the most major factor that introduces thermal drift error, a special thermal structure is designed to provide a small environmental chamber with sub-structure design of high performance heat isolation, heat conduction and homogenization of temperature, and the temperature in the environmental chamber is controlled with high precision based on bilateral temperature adjusting with thermo electronic cooler (TEC) devices, and a compound control algorithm of Bang-Bang and anti-windup PID. Experimental results with an ultra-precision spherical capacitive sensor show thermal drift error is significantly eliminated and the precision of the sensor can reach the level of several resolutions.
KEYWORDS: Sensors, Electrodes, Signal processing, Integrated circuits, Capacitance, Digital electronics, Wireless communications, Calibration, Data communications, Digital signal processing
In order to solve the problem of noncontact, wireless and nonmagnetic displacement sensing with nanometer resolution within critical limited space for ultraprecision displacement monitoring in the Joule balance device, a novel wireless digital capacitive displacement sensor (WDCDS) is proposed. The WDCDS is fabricated with brass and other nonmagnetic material and powered with a small battery inside, a small integrated circuit is assembled inside for converting and processing of capacitive signal, and low power Bluetooth is used for wireless signal transmission and communication. Experimental results show that the WDCDS proposed has a resolution of better than 1nm and a nonlinearity of 0.077%, therefore it is a delicate design for ultraprecision noncontact displacement monitoring in the Joule balance device, meeting the demand for properties of wireless, nonmagnetic and miniaturized size.
When conventional physical pinholes are used, the alignment of pinholes is always a problem. An iterative Wiener
deconvolution filter is used to reject out-of-focus light, a sub-pixel centre location method is used to locate the centre of
the pinhole, and the dimensions of the pinhole are optimized using the confocal microscopic theory. A filter with digital
pinhole is thus developed and compared with filter with conventional physical pinhole through comparative tests.
Experimental results indicate that the alignment of pinholes can be made easy, a filter with digital pinhole can be used to
take place of a filter with conventional physical pinhole, and it can also reduce the pixel crosstalk resulting from multipoint
illumination.
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