Abstract:Assembly is the key step for fabrication of high performance precision miniature devices or products, as the dimensions of the parts and their key structures are small, the assembly is inevitable to be sensor-based precision assembly. During assembly, the deviation of the position and orientation between the mating parts needs to be precisely measured, as well as the contact force or state to be controlled. Firstly, the sensors technology for assembly of miniature devices are briefly described, and then in combination of the application requirement of precision assembly of miniature devices, the vision sensor, the micro force senor, etc. and measurement technology are reviewed, precision measurement method and assembly control techniques are analyzed, aiming to provide reference value for the progress of precision assembly technology and development of assembly equipment.

Abstract:Bionics research has found that a variety of organisms can perceive polarized light in the environment, which could assist individuals to achieve behaviors such as foraging, migration and environmental perception. Among them, the peculiar ability of insects, which use the polarized skylight field to navigate, has the advantages of complete autonomy, resisting active interference, and no cumulative error over time. It has aroused the attention of researchers to bio-inspired polarized skylight navigation technology. Focusing on the polarization detection mechanism of insects, the polarized skylight distribution patterns in various weather environment are analyzed, bio-inspired polarized skylight navigation sensors are developed, and polarized skylight navigation methods for complex situations are researched, which may provide new research ideas for long-distance, long-period autonomous navigation and combined navigation applications in complex conditions.

Abstract:Considering the complex tracking measurement system and high development cost of active laser tracker, a passive laser tracking method is proposed to measure the spatial coordinates of target points. Firstly, the error analysis model of the passive laser tracking measurement system was established according to HTM principle, and the detection method of relevant error parameters was proposed. The measurement error of the passive laser tracking measurement system was reduced from 550μm to 150.8μm after error compensation. In order to further improve the measurement accuracy, residual errors after error compensation were collected as sample data, and BP neural network was used to train the sample data. After the residual error of the passive laser tracking system was compensated by the trained BP neural network model, the measurement error of spatial coordinate measurement was reduced from 150.8μm to 51.6μm. Compared with HTM error compensation method, the compensation effect of HTM+BP neural network model is improved by 65.8%.

Abstract:The machining accuracy of machine tools and the measuring accuracy of measurement instruments are significantly influenced by the positioning accuracy of linear stages, which are the basic components of the machine tool and the measurement instrument. Since there are the manufacturing error and the assemble error, the linear stage exists six-degree-of-freedom geometric motion errors, which will affect its positioning accuracy. It is essential to measure the geometric motion errors for compensating the positioning errors of the linear stage induced by the geometric motion errors. The traditional measurement method can only measure a single error element, which is time-consuming. In addition, the size of the traditional measurement instrument is bulky and cannot realize on-line geometric motion errors measurement. Therefore, a series of compact and low-cost multi-degree-of-freedom geometric motion errors measurement method are proposed in this paper. The degree-of-freedom of the measurement system can be selected according to the requirement of the measurement. The measurement systems can not only realize high-precision measurement, but also achieve on-line measurement. Multi-degree-of-freedom geometric motion errors measurement methods play an important role in improving the motion accuracy of linear stages.

Abstract:Constant chord height, base tangent length and the span of the rod are the parameters describing the tooth thickness of the gear. This article discusses the characteristics of the three tooth thickness parameters, and analyzes the increment relationship of the three parameters. Then, the calculation formula for the conversion between the three parameters increment was derived. Finally, the examples for the formulas were applied. Based on the conversion relationship of the three tooth thickness parameters, the increment of two tooth thickness parameters can be easily obtained once one of the tooth thickness parameters is given. It will be convenient for engineering applications.

Abstract:The closing and creeping displacement changes of the switch rail that as the weak link of railroad turnout are related to the safety of the train，which requires regular detection and strict control. For this purpose，both method and system for measuring closing and creeping displacements are developed. The system uses a motion guide rod to convert the closing and creeping displacements into linear and small angular displacements. Moreover，a calculation model for closing and creeping displacements and a calibration method is established. A dedicated data acquisition and transmission circuit is developed to realize the collection and monitoring of the closing and creeping displacements. The experimental results show that the measurement error is less than 0.2 mm，which meets the requirement of high-precision measurement for the closing and creeping of switch rail.

Abstract:The transmissibility of the structure can be defined as the ratio of spectrum of two measured response signals. The transmissibility is entirely unrelated to the excitation, which comprehensively reflects the physical characteristics of the structure, such as stiffness, damping and mass. Therefore, it is widely used in structural state detection. Here, signals observed by tri-axial accelerometer are treated as vector signals, and then transmissibilities for single channel signal are extended to quaternion-based three-channel joint transmissibility (QTJT). This method preserves the correlation among different channels, and overcomes the problem of signal distortion caused by separate processing for each single channel. Moreover, QTJT avoids the negative influence of sensor installation attitude on the final results in different detections. Thus the engineering practicability is improved. Based on the comprehensive test platform of ballastless track, state detection experiments of fastener loosening and temperature force changing were carried out by using QTJT, in which method of Karhunen-Loeve Transform (K-LT) and dual-tree quaternion wavelet transform (DQWT) were employed, respectively. For each experiment, detection result with the accuracy of over 90% was obtained.

Abstract:Laser has the advantages of high directivity, high monochromaticity, high coherence and energy density which cannot be achieved by ordinary light source, laser technology has been widely used in measurement, analysis, processing and manufacturing, medical and other fields. In recent years, due to the unique advantages of laser technology such as high precision, non-contact and good stability, it has become a research hotspot in the field of precision measurement and manufacturing. This paper reviews the application status of laser technology in precision measurement and machining, and classifies and summarizes the measurement principles and application scenarios. Finally, the development trend of laser technology in precision measurement and machining field is predicted on the basis of the present development status, which provides reference for the application of laser technology in the field of precision measurement and precision machining.

Abstract:The connection technique of various microparts is the key to improve the microsystem integration. The adhesion connection with high-viscosity adhesive presents the advantages, including simple operation, weak internal stress, no requirement of high temperature and pressure. Thus the adhesion connection has gradually become an important bonding method for high performance microsystems. The micro-dispensing of high-viscosity liquid has significant influence on the bonding performance. Since the flow resistance of high-viscosity liquid tube injection system is very high, the improvements on driving mode etc. are necessary for the micro-dispensing of high-viscosity adhesive in specific occasions. But the problem of high flow resistance has not been completely solved. The transfer dispensing method of the liquid mainly depends on the adhesion and transfer pressure between the transfer head, liquid and substrate surface. This method eliminates the restriction of the flow resistance in the tube, and does not need the high driving force, which is beneficial to the micro-dispensing of the high-viscosity liquid. In this paper, the mechanism of high-viscosity liquid micro-transferring is introduced. And the progress on both high viscosity droplet-loading and droplet-transferring are presented. At last, the development trends are prospected.

Abstract:With the miniaturization of products, manual assembly is getting difficult, and this assembly method can on longer meet the requirements of high-performance micro or small devices. To develop automated assembly equipment is an effective way to solve this problem. Due to the diversified assembly tasks, and factors such as device improvements, product upgrades, shortening of the research and development (R&D) cycle, the micro/ small assembly equipment developed is required to respond rapidly to the product changes. Therefore, the development of flexible assembly systems is the key to cope with the challenge. This paper introduces main technologies and methods for improving the flexibility of micro/ small assembly systems, namely modularization, and automatic exchange of manipulating tools and micro grippers for miniature parts. This paper the research progress. On this basis, the researchers proposed the system architecture of the flexible micro assembly system for a certain type miniature devices. The automated equipment for precision assembly of small devices developed based on the architecture is briefly introduced. This paper aims to provide reference for the development of flexible micro/ small assembly equipment.

Abstract:In response to the demand for non-contact measurement of gas pressure, a technical analysis of barometric pressure measurement based on the TDLAS direct absorption method was carried out. Taking CO2 as the research object, through the theoretical study of absorption spectrum based on Beer-Lambert law, a pressure measurement model is established, the pressure measurement process is simulated by MATLAB software, and the simulation results are compared with the results of SpectraPlot. Finally, an experimental system was built for verification. The results show that in the pressure range of 1 to 2 atm, the simulation results of the absorbance curve are highly coincident with the results of SpectraPlot, and the maximum deviation of the integrated absorbance value is less than 8%. The relative error of the pressure measurement experiment results shows a trend of increasing with the increase of pressure. This conclusion provides a reference for the future research on the measurement of medium pressure gas by absorption spectroscopy.

Abstract:According to the research status of reliability evaluation of liquid engine, the reliability of flow measurement system is evaluated from two dimensions of performance reliability and structure reliability. The definition of performance reliability of measurement system is given. The measurement data are regarded as normal distribution, and the confidence limit of one-sided reliability is calculated by interval estimation. The definition of structural reliability of measurement system is given. According to the series reliability diagram of flow measurement system, the exponential life failure test information is transformed into binomial success or failure test information. The L-M (Lindstrom-Maddens) combined with look-up table and linear interpolation method is used to solve the lower confidence limit of structural reliability. The reliability evaluation method of measurement system has important reference significance for measurement technicians in the industry.

Abstract:Along with the measurement demand of pointer pressure gauge and the development of automatic measurement technology, the pressure gauge intelligent verification has become one of the development trends of pressure measurement. This paper reviews the development process of pointer pressure gauge verification, describes the structure and characteristics of the pressure gauge intelligent verification system, compares and summarizes the research progress of pressure gauge intelligent verification at home and abroad, presents the basic structure of pressure gauge intelligent measurement, and finally summarizes the challenges and development trends of intelligent verification of pressure gauge. This paper has reference to realize the intelligent, efficient and low-cost verification of pointer pressure gauge.