Calculation of Skin Depths and Eddy-Current Power Losses for Magnetic Position Sensors

We present a theoretic model to calculate skin depths and eddy-current power losses for a magnetic position sensor. Eddy-current, arised from the operation of an alternating-current excitation, induces secondary currents and fields between magnetic material and magnetic position sensor. In this paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar. The analytical model is derived from basic field and circuit theory considering a linear approximation for a nonlinear permeability. Thus the skin depths and eddy-current power losses from the model in eddy-current modeling techniques at various frequencies of an excited current source can be calculated. The proposed configuration is capable of predicting the skin depths and eddy-current power losses for a magnetic position sensor and has a consistence with experiments.

A position sensor based on grating projection with spatial filtering and polarization modulation

A position sensor based on grating projection with spatial filtering and polarization modulation is presented. A grating is projected onto the object to be measured through a 4f optical system with a spatial filter. After reflected by the object, the grating projection is imaged on a detection grating through another 4f optical system to form moiré fringes, The polarization modulated moiré signal is detected to obtain the position information of the object. In the position sensor, the moiré signal varies sinusoidally with the position of object. The measurement is independent of the incident intensity on the projection grating and the reflectivity of the object to be measured, In experiments, the effectiveness of the position sensor is proved, and the root mean square （RMS） error at each measurement position is less than 13 nm.

X-ray detection based on complementary metal-oxide-semiconductor sensors

Complementary metal-oxide-semiconductor(CMOS) sensors can convert X-rays into detectable signals; therefore, they are powerful tools in X-ray detection applications. Herein, we explore the physics behind X-ray detection performed using CMOS sensors. X-ray measurements were obtained using a simulated positioner based on a CMOS sensor, while the X-ray energy was modified by changing the voltage, current, and radiation time. A monitoring control unit collected video data of the detected X-rays. The video images were framed and filtered to detect the effective pixel points(radiation spots).The histograms of the images prove there is a linear relationship between the pixel points and X-ray energy. The relationships between the image pixel points, voltage, and current were quantified, and the resultant correlations were observed to obey some physical laws.

In Vivo Dosimetry of an Anthropomorphic Phantom Using the RADPOS for Proton Beam Therapy

The radiation positioning system (RADPOS) combines an electromagnetic positioning sensor with metal oxide semiconductor field-effect transistor (MOSFET) dosimetry, enabling simultaneous online measurement of dose and spatial position. Evaluation points can be determined with the RADPOS. The accuracy of in-vivo proton dosimetry was evaluated using the RADPOS and an anthropomorphic head and neck phantom. MOSFET doses measured at 3D positions obtained with the RADPOS were compared with treatment plan values calculated using a simplified Monte Carlo (SMC) method. MOSFET responses, which depend strongly on the linear energy transfer of the proton beam, were corrected using the SMC method. The SMC method was used to calculate only dose deposition determined by the experimental depth-dose distribution and lateral displacement of protons due to the multiple scattering effect in materials and incident angle. This method thus enabled rapid calculation of accurate doses in even heterogeneities. In vivo dosimetry using the RADPOS, as well as MOSFET doses, agreed with SMC calculations in the range of ?3.0% to 8.3%. Most measurement errors occurred because of uncertainties in dose calculations due to the 1-mm position error. The results indicate that uncertainties in measurement position can be controlled successfully within 1 mm when using the RADPOS with in-vivo proton dosimetry.

大坝的微形变监测系统设计研究

采用高精密激光传感器,运用屏蔽系统和位置补偿使精度提高到几百纳米级,可将其运用于超级高坝坝体形变监测。不受湿度、温度和电磁场的干扰,能在恶劣环境中正常工作。对作为测试平台的精密X-Y工作台进行了重点设计,提出了误差补偿的方案,使测量方法的原理误差降低到微米级的程度。

ASSESSING THE DYNAMIC ERRORS OF COORDINATE MEASURING MACHINES

The main factors affecting the dynamic errors of coordinate measuring machines are analyzed. It is pointed out that there are two main contributors to the dynamic errors: One is the rotation of the elements around the joints connected with air bearings and the other is the bending of the elements caused by the dynamic inertial forces. A method for obtaining the displacement errors at the probe position from dynamic rotational errors is presented. The dynamic rotational errors are measured with inductive position sensors and a laser interferometer. The theoretical and experimental results both show that during the process of fast probing, due to the dynamic inertial forces, there are not only large rotation of the elements around the joints connected with air bearings but also large bending of the weak elements themselves.

激光对射式光电传感器实现定位车快速精确定位

翻车机作业时,需要快速精确定位火车位置。提出一种利用安装在固定位置的多组激光对射式光电传感器,预先提供定位车目标位置,实现定位的快速性。通过由编码器、高速计数模块、模拟量输出模块、变频器等组成的系统实现定位的精确性。

基于LabVIEW的位标器电位器测角标定系统

设计了基于LabVIEW的位标器电位器测角标定系统,其以倾角传感器作为标定基准,通过与DSP通讯完成位标器姿态角的闭环控制,同时记录电位器输出电压和倾角传感器的反馈值,并通过数据融合获得从电位器输出电压到角度输出之间的转换函数,从而完成了位标器测角的自动标定,并在保证标定精度的同时提高了工作效率。

基于光纤应变传感器的型架定位器位置检测方法研究

针对飞机装配过程中型架定位器的位置变化,提出一种基于光纤应变传感器的定位器位置检测方法。通过光纤应变传感器对型架主体及定位器组件关键特征区域的应变和定位器位置变化量进行实时采集,对采集的数据进行分析和处理,采用BP(back propagation,反向传播)神经网络建立飞机型架不同区域应变量与定位器位置变化量之间的数学模型。在某型工艺装备上搭建型架定位器位置检测试验平台,根据试验数据分别建立了定位器在平面及空间范围受载下的位置检测神经网络模型。试验结果表明:当神经网络样本数量一定时,模型对定位器位置的预测精度与加载偏移角度有关,偏移角度越小,加载覆盖率越高,模型的预测精度越高。其中,平面内以30°间隔、空间以45°间隔加载时,建立的神经网络模型对定位器位置的预测精度满足定位要求,验证了本文方法的可行性。该方法摈弃了用数字化设备直接测量的传统方式,弥补了因视线遮挡而造成个别定位器位置无法被检测的缺陷,能对装配过程中所有定位器的位置进行检测,解决定位器位置偏差过大造成的飞机部件检测质量差的问题,提升了飞机的装配质量。

Efficient closed-form solution for target localization using TDOA measurements in the presence of sensor position errors

An efficient solution for locating a target was proposed, which by using time difference of arrival （TDOA） measurements in the presence of random sensor position errors to increase the accuracy of estimation. The cause of position estimation errors in two-stage weighted least squares （TSWLS） method is analyzed to develop a simple and effective method for improving the localization performance. Specifically, the reference sensor is selected again and the coordinate system is rotated according to preliminary estimated target position by using TSWLS method, and the final position estimation of the target is obtained by using weighted least squares （WLS）. The proposed approach exhibits a closed-form and is as efficient as TSWLS method. Simulation results show that the proposed approach yields low estimation bias and improved robustness with increasing sensor position errors and thus can easily achieve the Cramer-Rao lower bound （CRLB） easily and effectively improve the localization accuracy.

ABB智能定位器震荡的一般处理方法

ABB智能定位器结构紧凑,功能较多,安装及调试方便,故障率低,赢得广大客户的青睐,所以应用很广泛。仅惠州炼油厂运行一部,就有320台在使用。最近发现有22台定位器震荡导致调节阀波动,由不同的原因导致出现此现象。文章通过对出现震荡的不同现象,进行分析判断,总结出原因,并逐个列出每种原因的具体处理方法。

DEH控制系统常见故障浅析

针对DEH系统中的一些常见故障进行了分析,指出故障的现象及产生的原因并推荐了常规的处理方法,并以古交电厂DEH系统为例对故障进行了分析,列举了故障的处理方法及改进措施,对电厂运行检修人员正确使用和维护DEH系统有指导作用。

A Novel Adaptive Cooperative Location Algorithm for Wireless Sensor Networks

To overcome the disadvantages of the location algorithm based on received signal strength indication(RSSI) in the existing wireless sensor networks(WSNs),a novel adaptive cooperative location algorithm is proposed.To tolerate some minor errors in the information of node position,a reference anchor node is employed.On the other hand,Dixon method is used to remove the outliers of RSSI,the standard deviation threshold of RSSI and the learning model are put forward to reduce the ranging error of RSSI and improve the positioning precision effectively.Simulations are run to evaluate the performance of the algorithm.The results show that the proposed algorithm offers more precise location and better stability and robustness.