光纤位移传感的改进网络补偿方法研究

本文研究了一种改进的网络补偿方法，在建立四光纤位移传感结构的数学模型基础上，说明了该方法的补偿机理，并对影响补偿性能的因素进行了分析。改进网络法具有补偿性能完善、实现简单的特点，对于光纤位移传感、粗糙度传感等具有重要的实用价值。     

Simultaneous measurement of strain and temperature using a hybrid local and distributed optical fiber sensing system

Structure multi-parameters measurement, such as strain, displacement, corrosion and temperature, is of the utmost importance for structural health monitoring. Meanwhile uncoupling method of temperature and strain has still a technical problem in structure sensing measurement. In this paper, we proposed a method for simultaneous measurement of strain and temperature using a hybrid local and distributed optical fiber sensing system. The principle of the method is investigated and then validated by the theoretical simulation experiments and tensile tests in laboratory. Furthermore, one experiment for internal force measurement of a smart stranded wire, under the interaction of temperature and strain, is also conducted in lab. The experimental results show that the strain and temperature can be well measured simultaneously by using one multi-signal optical fiber sensor.     

Monitoring of sea bed level changes in nearshore regions using fiber optic sensors

This work reports the implementation and test of a pressure optical sensor suitable to measure, in situ, the sea bed level changes in the nearshore regions. The sensor is based on a fiber Bragg grating (FBG) embedded in a polymeric resin block. The increase of the pressure on the top face of the sensor, due to the change of sediments layer height, results in a change of the FBG Bragg wavelength. The sensor response reveals the capacity to discriminate sea bed level changes down to 2.5 cm, under field survey conditions. Finally, the sensor was successfully tested in a field trial survey at Costa da Caparica, Portugal.     

NO x 传感器的氧补偿及其标定策略

针对氧化锆基氮氧化物传感器信号受汽车尾气氧含量影响,导致精度不佳问题,提出一种氧补偿算法和标定策略。根据NO_x传感器工作原理进行模拟试验,分析不同氧含量下泵电流I_P2与NO_x浓度的关系,得出氧补偿算法,并分析了氧含量与补偿系数的关系,设计出一种实时对I_P2误差补偿的方案,使I_P2在氧含量为0%～20%,NO_x为0～3 000×10^-6范围内的误差减小到23 nA,对应NO_x浓度误差降低到15×10^-6以内。为进一步提高传感器测量的准确度,设计了一套标定方案,并与国外NO_x传感器进行对比测试。结果表明,该传感器在发动机瞬态工况下,NO_x浓度为0～2 000×10^-6的环境中,测量误差为0～25×10^-6,验证了该方案的可行性,满足尾气中NO_x浓度的监测要求,为提高氧化锆基NO_...     

Temperature and refractive index sensor using a high-birefringence fiber loop mirror and single mode-coreless-single mode fiber structure

A novel fiber optic sensor for the simultaneous measurement of refractive index and temperature is reported. The sensor consists of a high-birefringence fiber loop mirror and a section of single mode-coreless-single mode fiber structure. The single mode-coreless-single mode fiber structure served as a refractometer while the high-birefringence fiber loop mirror was used to measure temperature. The multimode interference valley of the single mode-coreless-single mode fiber structure was sensitive to the surrounding refractive index of liquids (96.42 nm/refractive index unit) and had almost no response to temperature fluctuations. The high-birefringence fiber loop mirror was highly sensitive to temperature (1.98 nm/°C) but was insensitive to changes in refractive index. The theoretical and experimental results demonstrated simultaneous measurement of temperature and refractive index. The optimum resolution was 2.07 × 10^?4 refractive index units and 0.01°C.     

Experimental studies on fiber optic sensors embedded in concrete

Embedded fiber optic sensors are quite suitable for quantitative non-destructive long-term monitoring of concrete structures. Fiber optic sensors can be embedded in different types of structures, such as, buildings, roads, bridges, dams, etc. for monitoring different physical parameters like strain, temperature, deformation, etc. Bare fiber optic sensors are not suitable for directly embedding in concrete. Hence, some form of protective mechanism needs to be provided to the fragile fiber optic sensor for reliable performance. Suitable protective encapsulation to the bare sensor should ensure that there is no relative slip at the interface of the matrix concrete and the encapsulation. Investigations carried out to develop technique of embedding fiber optic sensor in concrete and performance evaluation of the developed embedment techniques are presented.     

光纤位移传感器在低温装置中测量超导转子悬浮微位移的应用

介绍了一种补偿式光纤位移传感器,对比分析了该传感器在室温(293 K)下和液氮温度(77 K)下的传输特性。结果表明,该传感器能有效地消除外界环境的影响,可用于宽温度范围的位移测量。在液氦温度(4.2 K)下测量超导转子悬浮微位移的实验结果表明,该传感器可在低温下进行位移测量,测量分辨率达到10 μm。实验结果为光纤位移传感器在低温环境下的应用提供了参考。     

光纤传感测量系统在超导转子旋转装置中的应用

介绍了超导转子旋转驱动原理以及应用在超导转子旋转装置中的一种光纤传感测量系统。光纤传感测量系统包括微位移光纤传感器、转速光纤传感器、电机控制光纤传感器和信号读取图形,该系统能够进行转子悬浮微位移和旋转速度的测量并提供转子旋转所需的控制信号。在4.2K低温下进行了转子悬浮旋转实验,超导球形转子悬浮微位移测量分辨率为10μm,转子转速达到了1013rpm。实验结果为进一步应用光纤传感测量系统精确监控超导转子工作姿态提供了参考。     

The fibre optic sensor in the in-process measurement of surface roughness

In the paper, a NFF type fibre optic displacement sensor is proposed, which now has been adopted to measure surface roughness. The system with this sensor is designed to be suitable for in-process measurement, in which a Z8 single-chip microcomputer is matched. The whole system is supported by assembly programs and is automatic, intelligent and flexible. The output changes of the sensor are discussed respectively for several special cases, and some necessary measures are described for the real operational environments.     

Determination of total polyphenols in tea by a flow injection-fiber optic spectrophotometric system

A flow injection-fiber optic spectrophotometric system was established for the online determination of total polyphenol content in tea samples. The method was based on the chromogenic reaction between the phenolic compounds (gallic acid) and ferrous tartrate which was used as the colorimetric reagent and the absorption was determined at the maximum absorption wavelength of 540?nm at 20°C and pH 7.5. The calibration curve from standard solutions of gallic acid was linear in the range from 0.010 to 0.100?mg/mL with a correlation coefficient of 0.9970. The relative standard deviation of polyphenol measurements for eight tea samples was between 0.55 and 3.18%. It can be concluded that the proposed method has allowed simple, fast, and accurate determination of total polyphenol content in tea products.     

A new flexible FBG sensing beam for measuring dynamic lateral displacements of soil in a shaking table test

In this paper, the design, validation, and application of a new flexible fiber Bragg grating (FBG) sensing beam are presented for effectively measuring dynamic lateral displacements inside soil mass in a shaking table test. The special flexible FBG sensing beam has been fabricated by employing a series of FBG sensors along with design of temperature compensation. Based on this design, equations of converting strains to lateral displacements are derived by using both differential and integral methods. Subsequently, the effectiveness of the FBG sensing beam has been verified in a shaking table test with non-contact laser displacement sensors (LDSs). The dynamic lateral displacements at different depths of the soil mass in the shaking table box throughout time history are calculated by differential and integral methods and compared with the results of LDSs. The comparison validates the measurement accuracy of the FBG sensing beam. Additionally, the Fast Fourier Transform (FFT) analysis result demonstrates that frequency measured by the sensing beam fits well with the results of traditional accelerometers and LDSs. Therefore, it can be concluded that the flexible FBG sensing beam is compatible with the stiffness of the soil and is capable of measuring dynamic lateral displacements with good accuracy in a shaking table test.     

基于光纤分布式传感器的时频定位技术

光纤单芯分布式传感系统可对传感线路上的扰动信号进行检测与定位,特别适合各种长距离的管道监控,如油管监控。传统的频域定位算法,依靠单独的几个频率点,有一定的局限性,并且如果扰动源未激发出所需要的频率范围,就无法获得频率缺失点,这种判断方法就会失效。提出了一种简单的时域定位算法,与频域算法进行互补,提高了系统的稳定性和普适性。     

Autonomous estimation of angle random walk of fiber optic gyro in attitude determination system of satellite

Angle random walk of fiber optic gyro is a dominant noise source in high-accuracy attitude control system of satellite. The coefficient of angle random walk denotes the magnitude of angle random walk and can be regarded as a “state of health” for gyro diagnosis. However, satellite motion included in gyro output disturbs in-orbit estimation of angle random walk. Moreover, the Allan variance method has too large offline computational effort and data storage requirements to be applied to in-orbit estimation. In addition, with the development of deep space exploration, it is urged that satellite should be more autonomy including autonomous fault diagnosis and reconfiguration. To overcome the barriers and meet satellite autonomy, we present a new autonomous estimation of angle random walk. A difference between angle increments of star sensor and gyro is taken to remove satellite motion from gyro output. Then, a simplified observation model based on Allan variance is proposed to estimate the angle random walk. Simulations show the proposed method correctly estimates the coefficient of angle random walk in real time and tracks the degradation of angle random walk caused by gamma radiation in space. The technique proposed here effectively isolates satellite motion, and requires no data storage and any ground support.     

Simultaneous distributed measurement of the strain and temperature for a four-point bending test using polarization-maintaining fiber Bragg grating interrogated by optical frequency domain reflectometry

We demonstrate a simultaneous distributed strain and temperature measurement technique with the spatial resolution of 1 mm using fiber Bragg gratings inscribed in a polarization-maintaining and absorption-reducing fiber (PANDA-FBGs) and optical frequency domain reflectometry (OFDR). We conduct four-point bending tests in an environmental chamber. Using high birefringent PANDA-FBGs that are manufactured specifically for the simultaneous measurements, the uniform temperature distributions and the typical strain distribution profiles of the four-point bending tests were successfully obtained. The measurement errors of strain were from −31 με to 19 με, and of temperature were from −0.9 °C to 1.3 °C. The spatial standard deviation was 7.5 με and 0.9 °C. We also discussed the effect of the residual strain of the sensor-bonding procedures and the data averaging.     

齿轮三维测量中线激光传感器位姿标定方法

在齿轮三维测量中,传感器位姿标定的结果直接影响测量结果的准确性.本文提出了一种基于特征标准件的线激光传感器位姿标定方法,并设计了一款具有一定几何特征的标准件.该方法解耦了传感器与仪器之间的位姿关系,通过运动过程中传感器与标准件的几何关系计算传感器的三个姿态角并调整至标定零位,然后通过多次偏置求等区域均值的方法依次计算传...     

Calculation of the unit normal vector using the cross-curve moving mask method for probe radius compensation of a freeform surface measurement

This paper proposes a cross-curve moving mask method to calculate the unit normal vector based on 5 or 9 data points of a freeform surface measurement for probe radius compensation. This is done in order to simplify the calculation and thus, produce a more efficient and time-saving process. Passing through the middle point and 4 or 8 neighboring points, two crossed curves – longitude and latitude can be constructed. The unit normal vector at the middle point can be determined by calculating the cross product of two tangent vectors along these two crossed curves. Different curve fitting methods for the curves passing through 5 or 9 data points, such as Bézier and B-spline methodologies, have been investigated. Three kinds of surfaces, namely, a spherical surface, a cosine-like surface and a shoe-shaped surface (hereby termed “shoe last”) are selected for evaluating the accuracy of the calculated unit normal vectors.     

航向测量系统中三轴磁传感器标定的等效两步法

针对航向测量系统中三轴磁传感器误差参数标定问题提出了等效两步法。通过奇异值分解将测量模型等效为一组坐标变换,分析误差参数的几何意义及等效变换方法的意义与特点,依据几何意义将标定过程分为两步进行,即等效传感器坐标系标定及等效非对准标定。利用椭球面方程系数计算等效传感器坐标系误差参数,明确椭球法标定参数的几何意义;应用主成分分析法进行等效非对准标定,分析传统主成分分析法产生符号错误及非正交问题的原因与影响,并研究符号修正与正交修正方法。等效两步法的标定过程不需要航姿参考、地磁信息及辅助传感器,实验表明其航向角校正精度与点积不变法相当。     

Added advantages in using a fiber Bragg grating sensor in the determination of early age setting time for cement pastes

A fiber Bragg grating (FBG) sensor was used to monitor the early age curing temperatures of cement paste. Additional advantages in using the sensor were highlighted. The FBG was inscribed by a Continuous Wave 244 nm argon ion laser in the photosensitivity fiber. The fabricated FBG was calibrated from room temperature to 105 °C. In this temperature range, the FBG was found to be good in terms of both the sensitivity and linearity which were around 9 pm/°C and 99.9%, respectively. A host specimen with ratio of Portland cement, sand and water of 800, 500, and 275 ml by volume was used in the experiment. Results showed that the FBG could determine the initial and the final early age setting times. The initial early age setting time for the cement paste was about 5 h and the final early age setting time was about 14 h after casting.