High-accuracy ultrasonic temperature measurement based on MLS-modulated continuous wave

Ultrasonic temperature measurement has the potential to improve measurement accuracy by increasing the length of a received signal due to its excellent performance with noise resistance. However, when the distance between the transmitter and receiver is limited, the received signal can be polluted by strong multiple echoes, which can significantly degrade temperature accuracy. This paper proposes a method for high-resolution ultrasonic temperature measurement. With the use of a maximum length sequence (MLS)-modulated continuous wave, the obstructive effect of echoes is effectively suppressed. A hybrid method is employed for accurate time-of-flight (TOF) estimation by incorporating both cross-correlation and phase shift (PS), which is the basis of highly accurate temperature measurement. The experimental results in distilled water show that the proposed method estimates TOF with a standard deviation of less than 0.3 ns, and temperature errors consistently remain within ±0.04 °C.     

快速离焦投影三维测量技术

随着数字投影技术的发展,基于投影的三维面型测量技术在多种场合得到广泛应用。基于相移的结构光投影测量技术以其算法简便精度较高得到较快发展。但投影仪为非线性仪器,会影响强度变化,进而影响相位测量精度;此外由于投影仪工作原理的投影速度受到限制。离焦投影技术的出现为高速测量和高精度测量提供了新的方法。总结了目前国内外对离焦投影技术的研究现状;从投影工作原理、相移算法、解包裹算法、误差补偿、条纹调制、标定技术及离焦投影技术的相关技术细节进行全面介绍,为数字离焦投影三维测量工作的研究提供参考。     

铝电解槽连续测温方法研究

本文提出了利用温度平衡原理对铝电解槽进行连续测温的方法。由于采取了负反馈措施,能够用热电偶在电解槽外面对内部温度进行测量,而不受环境温度变化的影响。初步的实验表明,这种方法使得铝电解槽温度的低成本、高精度连续测量成为可能,可望在冶金行业获得广泛应用。     

Displacement measurement using digital speckle multi-frequency harmonic wave correlation method

In the displacement measurement using digital speckle correlation method, significant measuring error due to the multi-peak nature of the correlation coefficient function is a critical issue as sometimes the secondary peak can be wrongly determined as the maximum instead of the highest peak. In the multi-frequency harmonic wave correlation method (MHCM) as proposed in this work, for speckle patterns before and after the displacement, correlation calculations were performed on corresponding sets of data matrices assembled by amplitudes/intensities obtained from harmonic waves with different frequencies. The calculated maximum correlation coefficients were compared with each other to locate the maximum in order to measure the displacement. Both ultrasonic speckle MHCM and laser speckle MHCM were applied to the displacement measurement respectively. Measured results indicated that MHCM effectively helps to ensure the correct determination of the maximum correlation coefficient, to avoid random errors caused by other factors and improves the measurement accuracy in the meanwhile.     

考虑温度影响的表面波压力测量模型研究

薄壁压力容器是一种常见的工业设备,为了保证生产过程的顺利进行,经常需要检测它们的压力。表面波在材料表面的传播速度与表面应力有关,因此以表面应力为中间变量,建立了被测容器压力与由此引起的表面波传播时间变化之间的关系模型。考虑温度、温度应力对表面波传播速度的影响,以及温度变化引起的热变形对传播距离的影响,推导了表面波压力检测的修正模型,并对修正模型各参数进行了分析,得到简化模型。实验证明了模型的正确性。使用该方法时,压力测量最大误差为0.11 MPa,平均误差为0.045 MPa。     

分布光度计测量LED路灯光通量的不确定度评定

为了减少检测的误差,提高检测结果精确度,评定LED路灯光通量的不确定度,分析了用分布光度计法测量LED路灯光通量的影响因素,建立数学模型对测量不确定度进行评定,并计算出A类、B类不确定度,最终给出测试结果的不确定度报告。相对扩展不确定度评定结果为4.13%,置信概率P为99%。结果表明,光谱辐射计的测量误差和标准灯的不确定度所产生的测量不确定度影响因素最大。     

An Accurate Ultrasonic Distance Measurement System with Self Temperature Compensation

Abstract

This study proposes an accurate distance measurement system which has self-temperature-compensation (STC) with the environmental average temperature in space, rather than a single point temperature. This system combines both the amplitude modulation (AM) and the phase modulation (PM) of the pulse-echo technique. The proposed system can reduce error caused by inertial delay and the amplitude attenuation effect when using the AM and PM envelope square waveform (APESW). The proposed system adopts two identical measurement hardware sets using the APESW ultrasonic driving waveform. The first set measures the sound velocity (the environmental average temperature information is also involved) as the result of the temperature compensation data for the second distance measuring set. Without using a temperature sensor, experimental results indicate that the proposed STC distance measurement system can accurately measure the distance. The experimental standard deviation of the linearity with respect to the distance is found to be 0.21 mm at a range of 50 to 500 mm. Moreover, the proposed system's temperature uncertainty effect produced a standard deviation of 0.093 mm, while the temperature sensor system's uncertainty effect produced a standard deviation of 0.68 mm. The STC manner is simple and can be easily adapted for robotic applications for which the temperature sensors can not easily be set up and placed. The main advantages of this STC distance measurement system are: high resolution, low cost, and ease of implementation.     

薄膜谐振Lamb波传感器测量液体流速矢量的方法

针对液体流速测量领域中微型流量传感器高品质因数、高灵敏度的性能要求。本文设计一种双端增强型薄膜谐振结构实现Lamb波传感器的高品质因数,利用传感器反对称模式(A01模式)在薄膜-液体界面处的消逝波实现液体流速矢量测量。所制作的双端增强型薄膜谐振Lamb传感器A01模式的主峰品质因数为703,A01模式的频率移动量与液体流速大小存在线性关系,频率移动方向与液体流动方向存在对应关系。流速实测灵敏度约为270 Hz/mm/s,传感器稳定性噪声小于0.2Hz,流速最低检测极限值(LOD)为2.2μm/s,流量最低检测极限值(LOD)为18.3nL/min。结果表明,双端增强型薄膜谐振Lamb波传感器可以实现液体流速高灵敏度矢量测量。     

Volume-weighted mean particle volume estimation using different measurement methods

The use of the ‘point-sampled intercepts’ method on histopathological material is evaluated for the main purpose of comparing different methods of intercept length measurements. The volume-weighted mean nuclear volume—nuclear —of the carcinoma of the ampulla of Vater is calculated using three methods for measuring intercept lengths: a semiautomatic image analyser, an equidistant I_o-ruler and a logarithmic -ruler. Rulers of several classes and lengths are used, and the results of the nuclear estimations are compared. The equidistant I_o-ruler is more accurate than the logarithmic -ruler. With a greater number of ruler classes and with adjustment of ruler length to the greatest nuclear intercept lengths, the systematic deviation from the true value of the nuclear is smaller. The nuclear parameter has great power to differentiate intestinal carcinoma from normal tissue.     

编解码电路在遥测遥控系统中的应用

本文介绍了一种新颖的编解码芯片的工作原理,给出了一个应用实例,讨论了ＵＭ３７５８－１０８在浑水浊度测控系统中的应用,最后给出了实验结果。     

A new fault diagnosis algorithm for helical gears rotating at low speed using an optical encoder

Helical gears are widely used in gearboxes due to its low noise and high load carrying capacity, but it is difficult to diagnose their early faults based on the signals produced by condition monitoring systems, particularly when the gears rotate at low speed. In this paper, a new concept of Root Mean Square (RMS) value calculation using angle domain signals within small angular ranges is proposed. With this concept, a new diagnosis algorithm based on the time pulses of an encoder is developed to overcome the difficulty of fault diagnosis for helical gears at low rotational speeds. In this proposed algorithm, both acceleration signals and encoder impulse signal are acquired at the same time. The sampling rate and data length in angular domain are determined based on the rotational speed and size of the gear. The vibration signals in angular domain are obtained by re-sampling the vibration signal of the gear in the time domain according to the encoder pulse signal. The fault features of the helical gear at low rotational speed are then obtained with reference to the RMS values in small angular ranges and the order tracking spectrum following the Angular Domain Synchronous Average processing (ADSA). The new algorithm is not only able to reduce the noise and improves the signal to noise ratio by the ADSA method, but also extracts the features of helical gear fault from the meshing position of the faulty gear teeth, hence overcoming the difficulty of fault diagnosis of helical gears rotating at low speed. The experimental results have shown that the new algorithm is more effective than traditional diagnosis methods. The paper concludes that the proposed helical gear fault diagnosis method based on time pulses of encoder algorithm provides a new means of helical gear fault detection and diagnosis.