磁阻式传感器在角度测量中的应用

介绍一种利用磁阻式传感器构成的非接触角度自动测量系统。分析了非接触角度测量系统的结构、原理以及信号处理方法,给出了角度测试结果,系统的角度测量范围为0°~180°,测量精度为±0. 5°。     

一种可同时测量位移和角度的电容式传感器设计

提出了一种可同时测量位移和角度的变面积式差动电容传感器的设计方案。位移测量范围为-50～50mm,准确度可达0.2mm,角度测量范围为0～180°,准确度可达0.5°。通过在结构上采用介质差动法,该传感器克服了边缘效应的影响,具有测量范围宽、线性度良好、受温度影响小等优点。     

天空散射光偏振成像噪声建模与分析

仿生偏振导航是近年来兴起的一种新原理导航方式,对天空光进行成像可以获得更为丰富的天空散射光的偏振信息以及分布特征,有利于提高偏振导航传感器的精度和抗干扰能力.根据现有的Stokes参量测量偏振光的原理以及成像装置的噪声模型,对基于Stokes参量法的偏振角度测量噪声进行了建模,并根据模型进行了仿真分析.仿真结果表明:提高相机的信噪比(SNR)能够显著提高偏振成像的质量,当相机的SNR大于44 dB时,天空偏振角度的测量标准差将优于1°/像素;得到了0°,60°,120°和0°,45°,90°检偏器分布模式下对不同偏振角度的入射光测量噪声的统计分布特征.尽管0°,60°,120°的检偏器布置方案相对于0°,45°,90°的检偏器布置方案有着更大的计算复杂度,但在使用相同信噪比相机的情况下,该布置方案的噪声更小.该结论将对天空偏振光成像装置的构建及其误差分析与补偿技术提供参考.     

MEMS无线数显角度测量仪设计

针对双轴或单轴高精度角度测量的工况需要,采用8位单片机为主控芯片,高精度数字MEMS为传感器芯片设计了一种体积小、功耗低的无线数显角度测量仪.远端上位机通过ZigBee无线模块对测量仪进行操作和三维显示,同时集成OLED屏可就地显示测量数据.具有双轴±90°倾角测量和单轴绝对式0°~360°转角测量功能.测试结果表明:该测量仪测量精度为0.1°,具有较高的推广应用价值.     

热阻式流速仪的设计

阐述了流速仪的组成与热平衡原理,并结合实际情况在水体流场中得到了良好的应用.其控制方式采用恒流方式和恒温方式.此流速仪主要测量渠道的时均流,测量范围为0～2m/s,低流速(0～0.5m/s)的精度达到1%;高流速(0.5～2m/s)的精度达到3%.     

皮托管测量影响因素分析 I. 检测杆与安装角的影响

在现场使用中,皮托管不可避免地会偏离其标准使用条件,从而引起附加误差.针对不同型号的皮托管进行了较系统的试验,旨在研究检测杆和安装角对皮托管测量的影响.结果表明,在被测流速较低时,皮托管检测杆直径的大小对全压的测量影响较小,且测量值误差也较小;在皮托管安装角不超过±10°的范围内,流速测量误差为±2%;较小管径检测杆的测量值存在非零安装角时,受流速的影响比较小.这些结论为优化皮托管的测量提供了指导.     

基于加速度计的数字式倾角仪的设计

所设计的数字式倾角仪是一种基于MEMS热电偶加速度计的智能测量仪,可用于测量0°~360°倾角,同时,针对环境温度变化时对加速度计的影响,通过软件进行了补偿,测试表明:该倾角仪的测量精度达±0. 1°,并具有良好的工作稳定性和较高的性价比。     

基于CORDIC算法的360°角度传感器的设计

一维霍尔板型角度传感器无法测量0～360°的角度,采用4个霍尔器件的联合测角技术和CORDIC算法可实现0～360°范围内的角度测量。文章详细描述了4个霍尔器件联合测角技术的测角原理及实现算法,并引入了符号幅值表示法,即先利用正弦和余弦的幅值进行0°～90°范围内的反正切CORDIC运算,再根据正弦和余弦正负号(符号)的不同组合实现角度从0°～90°到0°～360°的映射。Modelsim平台仿真验证了该方法的准确度和精度,仿真误差小于0.01%,实测总误差不大于0.05°。     

基于应变式双参数倾斜仪的设计

为精确测量桩体在施工过程的倾斜角度,介绍一种基于电阻应变计式的双参数倾斜仪,阐述了倾斜仪的结构设计和工作原理;推导出倾斜角和方位角的数学模型。对放大电路及其信号变换电路进行硬件设计和软件编程。实验结果表明倾斜角在±10°范围内,其测量精度为0.04°;方位角在0°～360°范围内,其测量精度为2.253°,可以满足桩基础施工的技术要求。     

深海高流速传感器研制

阐述了深海高流速传感器的工作原理、结构设计、工艺研究及信号处理技术,该传感器中流速测量采用毕托管原理,利用差压传感器测量流体总压与静压差,流向测量采用水向标原理,角度变化由磁阻芯片检测,并采用单片机进行数据采集和后续处理,使得传感器具有测量范围宽、准确度高、耐高静压、分辨力高、抗振动冲击、耐腐蚀、适于深海中流场测量等特点。     

Surface tension driven flow for open microchannels with different turning angles

Present study examines the flow characteristics of open microchannels with sharp turns by experimental and numerical methods. For the open channel system in microscale, the flow is mainly driven by surface tension at atmospheric pressure. The open channels are of various aspect ratios of depth-to-width, ranging from 0.75 to 3, and of turning angles from 45° to 135°. It is found that the turning angle and the aspect ratio of depth-to-width play major roles in the velocity of liquid front advancing, the meniscus of liquid–gas interface shape, and head loss of flow due to turning. Besides, the radius of curvature of the liquid front is reduced as the liquid front travels downstream and over the turning elbow. The loss coefficient remains the same for turning angles less than 75°, whereas it is increased further and is even more pronounced for turning angles larger than 105°. Numerical predications based on conservation laws agree with the experimental observations, and the flow characteristics are well described for open channel in microscale, as the aspect ratio is greater than or near to 1.5.     

A bioinspired touching sensor for amphibious mobile robots

An amphibious mobile robot relies on effective sensing ability to adapt itself in complicated amphibious environments. In this paper, we present a multifunctional whisker-like touching sensor with low energy consumption, inspired by amphibious animals. The sensor comprises a leverage system and a two-dimensional position tracing system, transforming the moving position of biowhisker to a changing laser spot coordinates. On land, the sensor driven by a motor is able to track the movement of biowhisker directly, telling the change of contact position, to sense nearby objects and explore their surface by touching. In underwater environment, the sensor can obtain in real-time external flow direction and velocity by passive impulsion. Testing results showed that our prototype can sense flow or drag force direction in 360° exactly, and tell flow velocity under 1 m/s, it can also recognize line or arc edges of obstacle correctly by touching.     

激光测速雷达的性能对比分析

激光测速雷达较传统大气数据系统在测量精度方面有显著的优势。为了能够在稳定流场下实现对比测试,将激光测速雷达和高精度超声波风速风向仪一同放置于风塔200 m高度进行长时间对比。以10 min、1 min、1 s、0.1 s为尺度对两者测量的真空速(风速)和侧滑角(风向)进行分析。数据表明激光测速雷达的测量精度和超声波风速风向仪(速度精度0.18 m/s、风向2°)是同级别的。     

CMOS风速风向传感器的设计

介绍了一种CMOS(互补MOS)集成风速风向传感器,使用恒温差(CTD)控制模式将芯片加热,使其中间加热区域的温度高于周围环境(风)温度一定值。该传感器在有风吹过它的表面时能同时测量风速和风向。采用4个串联的热堆测量芯片中心区域的平均温度,这种测温的方法简单、新颖。在简单阐述CMOS硅热流量传感器的工作原理和结构之后,主要介绍驱动和信号读取电路。经过风洞测试,传感器能够测量风速0～23m/s,具有良好的线性度和灵敏度,同时,传感器360°内方向敏感。     

Liquid and gas flows in microchannels of varying cross section: a comparative analysis of the flow dynamics and design perspectives

This paper presents a comparative study of the flow of liquid and gases in microchannels of converging and diverging cross sections. Towards this, the static pressure across the microchannels is measured for different flow rates of the two fluids. The study includes both experimental and numerical investigations, thus providing several useful insights into the local information of flow parameters as well. Three different microchannels of varying angles of convergence/divergence (4°, 8° and 12°) are studied to understand the effect of the angle on flow properties such as pressure drop, Poiseuille number and diodicity. A comparison of the forces involved in liquid and gas flows shows their relative significance and effect on the flow structure. A diodic effect corresponds to a difference in the flow resistance in a microchannel of varying cross section, when the flow is subjected alternatively to converging and diverging orientations. In the present experiments, the diodic effect is observed for both liquid and gas as working fluids. The effect of governing parameters—Reynolds number and Knudsen number, on the diodicity is analysed. Based on these results, a comparison of design perspectives that may be useful in the design of converging/diverging microchannels for liquid and gas flows is provided.     

Topology optimization of internal partitions in a flow-reversing chamber muffler for noise reduction

A topology-optimization-based design method for a flow-reversing chamber muffler is suggested to maximize the transmission loss value at a target frequency considering flow power dissipation. Rigid partitions for high noise reduction should be carefully placed inside the muffler to avoid extreme flow power dissipation due to a 180° change in flow direction from an inlet to an outlet. The optimal flow path for minimum flow power dissipation is well known to change depending on the Reynolds number, which is a function of the inlet flow velocity. To optimize the partition layout with an optimal flow path in an expansion chamber at a given Reynolds number, a flow-reversing chamber muffler design problem is formulated by topology optimization. The formulated topology optimization problem is implemented using the finite element method with a gradient-based optimization algorithm and is solved for various design conditions such as the target frequencies, rigid partition volumes, Reynolds numbers, non-design domain settings, and allowed amounts of flow power dissipation. The effectiveness of our suggested approach is verified by comparing the optimized partition layouts obtained by the suggested method and previous methods.     

A microcantilever-based gas flow sensor for flow rate and direction detection

Utilizing conventional micro-electro-mechanical systems techniques, this study fabricates and characterizes a novel micro gas flow sensor comprising four silicon nitride/silicon wafer cantilever beams arranged in a cross-form configuration. The residual stresses induced within the beams during their fabrication cause the tip of each beam to curve slightly in the upward direction. However, as air travels over the surface of the sensor, the upstream cantilevers are deflected in the downward direction, while the downstream cantilevers are deflected in the upward direction. The velocity of the air flow is then determined by measuring the corresponding change in resistance of the piezoresistors patterned on the upper surface of each cantilever beam. It is shown that by measuring the change in resistance of all four cantilever beams, the proposed sensor can detect not only the velocity of the air flow, but also its direction.     

Numerical solution of the problem of unsteady supersonic flow around the front part of the wings with a detached shock wave

The object of this paper is to describe a numerical method for the solution of the problem of unsteady supersonic flow around the front part of the wings with a detached shock wave. The planform and the airfoil of the wings must be constructible but otherwise arbitrary. The velocity vector of the free stream is directed in an arbitrary direction but without flow separation.The problem is formulated for the three-dimensional, hyperbolic system of equations of unsteady, inviscid, chemically reactive gas flow in a mixed subsonic and supersonic domain. It is solved by a finite difference, implicit, second-order method with the use of the time-dependent stationing principle.A curvilinear coordinate system is introduced in which the numerical domain becomes a simple rectangle. The coordinate system is time-dependent and adapted for the planform of the wing and the free-stream parameters. The planform of the wind and the velocity vector of the free stream may be changed in the time-dependent stationing process. The flow field is computed around the front part of wings which have an elliptical planform and an aspect ratio λ ? 2 for selected values of M_æ between 1.5 and 5.     

An experimental study on the flow behavior near the read-and-write arm in a hard disk drive model with a shroud opening

Complex flow inside a hard disk drive (HDD) was investigated using a simplified 3.5″ model for clarifying the mechanism causing flow-induced vibration. In contrast to the authors’ related study in the past, our model had a non-axisymmetric geometry equipped with a shroud opening and a read/write arm (RWA). The model is designed to serve as a benchmark to study HDD flows both in experiments and in numerical simulations. The complex flow behavior in the disk-to-disk space was investigated with the RWA inserted into the inter-disk space. Flow measurements were carried out with a test rig which consisted of transparent disks, RWA and covers. The measurements were performed at the disk Reynolds number Re _d  = 1.2 × 10⁵ which corresponds to the rotation speed of 7,700 rpm of a real 3.5″ HDD. Two sets of the flow measurements were performed—the first Reynolds stress components measured along four different lines with the RWA inserted at a shallow angle (experiment I), and the other mean and rms velocity statistics along several selected lines with two different RWA insertion angles (experiment II). The mean velocity and velocity variance were obtained at a spatial resolution of 30 μm along eight different lines perpendicular to the disk surfaces. The high spatial resolution of the results was achieved using a laser Doppler velocity profile sensor with a physical resolution in micrometers and a velocity uncertainty of 0.2 %. In the experiment I, the mean velocity and velocity variance statistics were mostly consistent with the common findings in other studies using axisymmetric models except for the flow behavior in the radial direction at the shroud opening. The secondary flow behavior was likely caused by the shroud opening which was not included in most of the models in the past. In experiment II, the mean velocity and velocity variance were successfully measured through examination of the flow above and below the RWA in the space between the rotating disks. The resulting velocity statistics exhibit turbulent Couette-like flow in the narrow 1 mm space between the disks and the RWA.     

Haptic discrimination of virtual surface slope

We report the difference thresholds of the slope of a virtual surface rendered via a force–feedback haptic interface with the body frontal plane as a reference. The factors varied in experiments were the stiffness of a virtual plane, the lateral velocity with which the haptic probe scanned the plane, the length of a scanning interval, the movement direction of the probe to the body frontal plane (toward or away from the body), and lateral scanning direction (left-to-right or right-to-left). Measured slope thresholds ranged from 8.33° to 12.74° and were generally higher than or similar to previously published thresholds for haptic orientation or angle discrimination. The results suggested that haptic slope discriminability was independent of surface stiffness and lateral scanning velocity. Slope discrimination was largely affected by the lateral scan distance, indicating that the terminal difference of probe normal position can be an important sensory cue. In terms of scan direction, inward or rightward scans resulted in better slope discrimination than outward or leftward scans, respectively. These thresholds and findings have implications for haptics applications that involve geometric model modification or simplification of virtual objects while preserving their perceptual properties.