一种用于神经肌肉疾病评估系统的幅相测量电路的设计

神经肌肉疾病评估系统的关键是能同时准确提取幅值和相位信息。利用AD8302的高度集成特性设计了一种幅相测量电路。给出了电路原理图,详细论述了测量频率为50 kHz时,幅相测量电路设计的具体方法。性能分析结果表明,幅值和相位的测量性能与额定值比较接近。在±20 dB范围内,幅值测量精度在±0.5 dB以内;在±90°范围内,相位测量精度在±0.9°以内。     

倾斜梳齿的MEMS电容式加速度传感器自我标定特性研究

本论文研究MEMS电容式加速度传感器的自我标定方法,模拟机械振动台标定,提高标定效率和降低标定成本,并从理论上分析了DRIE工艺误差对传感器自我标定精度的影响。本文分析的传感器模型梳齿间距为4um,厚度80um,传感器自我标定以模拟幅值为1g的振动台标定为例,针对DRIE工艺加工的高深宽比梳齿电容存在正负侧壁倾斜角α的情况,分析了该倾斜角对梳齿式传感器自我标定的影响。分析结果表明：传感器工作在开环电路时,梳齿的倾斜对传感器自我标定影响明显,且随着倾斜角度的增大而增大。与梳齿完全平行时传感器的自我标定相比,倾斜角为±0.1°时,自我标定误差约为10%;倾斜角为0.5°时,自我标定误差约为27%;倾斜角为-0.5°时,极板发生吸合。表明传感器工作在开环电路时,梳齿的倾斜角对传感器的自我标定影响明显,而传感器工作在闭环电路时,梳齿的倾斜对自我标定的影响明显降低,当倾斜角小于±0.5°时,自我标定的误差小于0.6%,理论误差接近于激光干涉仪绝对标定法的误差(0.5%－1%),证明了自我标定方法的可行性。本文还分析了倾斜角影响自我标定精度的原因以及提出了开环自我标定时减小倾斜角误差的方法,并阐述了具体的修正步骤。     

一种新型磁敏集成角度传感器及其测量系统

研制了一种无触点的十字形两维集成垂直霍尔器件 ,它对平行于芯片表面的磁场敏感。当与被测转角θ的物件轴向相连的径向永久磁铁转动时 ,传感器给出了相对于被测角度的两种信号电压 ,通过接口电路和PC机组成的非接触式测量系统把信号转换为转角θ。测试结果表明该角度传感器及其测量系统的测量精度在 0°～ 36 0°范围内可达± 1°     

基于超声波原理的开孔参数标定系统研究

针对传统的人工丈量方法标定开孔方位角和倾斜角存在操作程序繁琐、稳钻时间长、精度低等问题,设计了基于超声波原理的钻孔开孔参数标定系统。该系统采用超声波渡越时间检测法测量参考点之间的距离,并由单片机解算出钻杆的方位角,选用微机械三轴加速度计测量倾斜角,实现了全自动化的实时跟踪测量及智能化的钻机姿态调整语音指导操作;在误差允许范围内,可快速标定所需开孔参数。该系统提高了开孔参数标定精度、标定效率及煤矿管理水平,降低了矿工劳动强度和煤矿管理成本。     

基于超声波原理的开孔参数标定系统研究

针对传统的人工丈量方法标定开孔方位角和倾斜角存在操作程序繁琐、稳钻时间长、精度低等问题,设计了基于超声波原理的钻孔开孔参数标定系统。该系统采用超声波渡越时间检测法测量参考点之间的距离,并由单片机解算出钻杆的方位角,选用微机械三轴加速度计测量倾斜角,实现了全自动化的实时跟踪测量及智能化的钻机姿态调整语音指导操作;在误差允许范围内,可快速标定所需开孔参数。该系统提高了开孔参数标定精度、标定效率及煤矿管理水平,降低了矿工劳动强度和煤矿管理成本。     

一种新型太阳跟踪器的设计

设计了基于位置敏感探测器(PSD)的太阳跟踪器,实现对太阳的自动跟踪。该跟踪器能够适应各种天气,晴天时启动光电跟踪,阴雨天时启动日历跟踪,能够实现方位角在360°范围内,高度角在90°范围内自动跟踪。进行了系统误差分析与实验,实验结果表明:该方法的跟踪精度在±12°,视场角度内为0.1°,各种天气情况下,跟踪器均能稳定地工作,能够达到预期的设计性能。     

振动下惯性随钻测量的方位漂移闭环补偿

为解决振动下惯性随钻测量(Measurement While Drilling,MWD)方位角失真的问题,提出一种方位漂移在线闭环补偿方法。方法：考虑陀螺仪随时间漂移而加速度计长时测量稳定,利用多传感器分布式信息融合,获得微惯性测量单元(Micro Inertial Measurement Unit,MIMU)测量加速度和重力加速度在钻具坐标系下的向量误差,建立存在振动的方位陀螺漂移PI控制模型,设计一种基于函数逼近理论的新型神经网络结构,通过优化权值直接确定法(Optimized Weights Direct Determination,OWDD)快速确定网络权值,将神经网络辨识信息反馈给PI控制器,实现对方位陀螺漂移的自适应控制,实时跟踪误差趋向并补偿。结果：最后设计实验,振动台实验中方位角误差由10.15°/h减小到0.21°/h,实际钻井实验中方位角误差由10.53°/h减小到0.3°/h。结论：结果表明振动下方位角测量精度明显提高。     

基于单片机的电容式角位移测量系统

介绍一种电容式角位移测量系统,它以电容传感器作为敏感元件,以89C51单片微机为控制核心。详细分析了电容式角位移传感器的结构、特点及工作原理,叙述了该系统的硬件框图及软件流程图,实验结果表明:在0°~90°测量范围内,系统的测量精度可以达到±0.05°。     

一种新型磁阻传感器的研究及应用

介绍了美国Honeywell公司生产的磁阻弱磁传感器的性能特点,以及由其组成的三轴智能型弱磁传感器在测量磁航向方面的应用.实验结果表明:在捷联状态下,用垂直陀螺提供载体的姿态角,在俯仰角、倾斜角达±45°的情况下,测角精度优于 0.6°.该传感器应用的显著特点是体积小、重量轻.它与垂直陀螺组成简易捷联航姿系统,已用于无人机的控制与导航.     

一种基于磁传感器的MEMS陀螺标定方法

根据微型航姿测量系统各传感器的特点,研究出了一种基于磁传感器输出的MEMS陀螺标定方法,并根据MEMS陀螺误差参数模型设计相应的补偿算法,分别对MEMS陀螺的零偏和标度因数误差进行了补偿。与传统标定方法相比,该方法实现简单,适用于现场标定。实验结果表明,该标定方法能够有效地提高MEMS陀螺测量精度,补偿后陀螺在静态条件下2分钟内,俯仰角漂移小于0.035°,倾斜角漂移小于0.15°,航向角的漂移小于0.2°。当陀螺三轴均有角速率输入时,在角速度小于25°/s情况下误差都能保持在±2°以内。     

Human Factors Requirements for the Development of U.S. Army Materiel∗†

This study investigated the effects of visual cues, muscular fatigue, task performance and experience of working on inclined surfaces on activity of postural muscles in the lower limbs associated with maintaining balance on three inclined surfaces – 0°, 14° and 26°. Normalised electromyographic (NEMG) data were collected in 44 professional roofers bilaterally from the rectus femoris, biceps femoris, tibialii anterior and gastrocnemii medial muscle groups. The 50th and 95th percentile NEMG amplitudes were used as EMG variables. Results showed that inclination angle and task performance caused a significant increase in the NEMG amplitudes of all postural muscles. Visual cues were significantly associated with a decrease in the 95th percentile EMG amplitude for the right gastrocnemius medial and tibialis anterior. Fatigue was related to a significant decrease in the NEMG amplitude for the rectus femoris. Experience of working on inclined surfaces did not have a significant effect on the NEMG amplitude.     

高精度微波引导设备角度数据检测系统设计与实现

针对当前某高精度微波引导设备的角度制导性能精准检测难度大的问题,基于ARM+DSP+FPGA的总体架构,研究并搭建了高精度角度数据检测系统的硬件电路结构,基于C/C++、VHDL和Verilog开发了角度数据测试软硬件程序,实现了对微波引导设备空间角度、数据信号的接收、处理、解算和测量;并进行试验验证,结果表明该系统实现了设计功能、达到了指标要求,对高精度微波引导设备角度测量方位角优于0.16°,仰角优于0.18°,数据字与设备预置信息一致,满足高精度角度、数据的检测要求,对有效提高该微波引导设备的可靠性具有重要意义。     

一种新型的塔康方位角估算方法

塔康作为近程无线电导航系统,为飞机提供与地面台的距离和方位角度等信息,但由于硬件工艺、环境等限制,其测量精度极易受到噪声的影响.针对这一问题,提出了一种新型的方位角估算方法.该方法在最小二乘法的基础上,创新性地增加了误差检测功能和拟合数据反馈的功能,通过误差检测功能去除超过误差门限范围的接收数据,再利用平均后的拟合数据...     

Two-dimensional broadband and wide angle scanning multi-beam antenna based on leaky-wave metasurface

In this article, a novel two-dimensional multi-beam antenna with a broad band and a wide angle scanning range is proposed. It is composed a leaky-wave metasurface (MTS) and a four-port feeding network with high isolation. The leaky-wave MTS formed by T-shaped slots is displayed as radiator and divided into four angular sectors, each one devoted to the formation of a beam in a given elevation plane. At every fixed frequency, the antenna can radiate multi beam in azimuth plane through exciting different ports. Also, multi-beam radiation with a broad band and a wide angle scanning range in the elevation plane is realized when fixed port is excited at different frequency. The antenna with overall size of 207 mm by 207 mm by 2.0 mm is fabricated on FR-4 substrate. The measured and simulated results show that the ?10 dB relative bandwidth is 30% (from 9.44 to 12.77 GHz). When different ports are excited at the same frequency, the azimuth of radiation beam is steered to 0°, 90°, 180°, and 270°. In addition, the beam-scanning range of the prototyped antenna is from 29° to 75° when the frequency sweeps in the range of 9.5–12.0 GHz. Also, the maximum radiation efficiency reaches to 31.1% and the measured peak gain within the scanning range is 12.29 dBi.     

The effects of a sloped ground surface on trunk kinematics and L5/S1 moment during lifting

There are many work environments that require workers to perform manual materials handling tasks on ground surfaces that are not perfectly flat (e.g. in agriculture, construction, and maritime workplaces). These sloped ground surfaces may have an impact on the lifting strategy/technique employed by the lifter, which may, in turn, alter the biomechanical loading of the spine. Describing the changes in kinematics and kinetics of the torso is the first step in assessing the impact of these changes and is the focus of the current research. Subjects' whole-body motions were recorded as they lifted a 10 kg box while standing on two inclined surfaces (facing an upward slope: 10° and 20°), two declined surfaces (facing a downward slope: ? 10° and ? 20°), and a flat surface (0°) using three lifting techniques (leg lift, back lift and freestyle lift). These data were then used in a two-dimensional, five-segment dynamic biomechanical model (top-down) to evaluate the effect of these slopes on the net moment about the L5/S1 joint. The results of this study showed an interesting interaction effect wherein the net L5/S1 moment was relatively insensitive to changes in slope angle under the back lift condition, but showed a significant effect during the leg lift and freestyle lifting conditions. The results show that under the freestyle lifting condition the peak L5/S1 moment was significantly higher for the inclined surfaces as compared to the flat surfaces (6.8% greater) or declined surfaces (10.0% greater). Subsequent component analysis revealed that both trunk flexion angle and angular trunk acceleration were driving this response. Collectively, the results of this study indicate that ground slope angle does influence the lifting kinematics and kinetics and therefore needs to be considered when evaluating risk of low back injury in these working conditions.     

Centered inclined slot coupling between waveguides with coplanar axes

The article presents the method of finding the complete equivalent circuit of two waveguides with coplanar axes coupled through a centered inclined slot in the common broad wall. The variational method based on dyadic Green's function is used for finding the parameters of the equivalent circuit. A cosinusoidal aperture field distribution is assumed. Considerable mathematical simplification is resulted from replacing the centered inclined slot by an equivalent magnetic dipole. Coupling slot characteristics are deduced, including resonant length, dominant mode scattering in both the waveguides. Numerical and experimental results for resonant lengths and scattering parameters are presented over a range of tilt angles, frequencies, and waveguide dimensions. These results have significant applications in linear waveguide arrays and coupler design. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

What Do the Sun and the Sky Tell Us About the Camera?

As the main observed illuminant outdoors, the sky is a rich source of information about the scene. However, it is yet to be fully explored in computer vision because its appearance in an image depends on the sun position, weather conditions, photometric and geometric parameters of the camera, and the location of capture. In this paper, we analyze two sources of information available within the visible portion of the sky region: the sun position, and the sky appearance. By fitting a model of the predicted sun position to an image sequence, we show how to extract camera parameters such as the focal length, and the zenith and azimuth angles. Similarly, we show how we can extract the same parameters by fitting a physically-based sky model to the sky appearance. In short, the sun and the sky serve as geometric calibration targets, which can be used to annotate a large database of image sequences. We test our methods on a high-quality image sequence with known camera parameters, and obtain errors of less that 1% for the focal length, 1° for azimuth angle and 3° for zenith angle. We also use our methods to calibrate 22 real, low-quality webcam sequences scattered throughout the continental US, and show deviations below 4% for focal length, and 3° for the zenith and azimuth angles. Finally, we demonstrate that by combining the information available within the sun position and the sky appearance, we can also estimate the camera geolocation, as well as its geometric parameters. Our method achieves a mean localization error of 110 km on real, low-quality Internet webcams. The estimated viewing and illumination geometry of the scene can be useful for a variety of vision and graphics tasks such as relighting, appearance analysis and scene recovery.     

Straight ladder inclined angle in a field environment: the relationship among actual angle,method of set-up and knowledge

Ladder inclined angle is a critical factor that could lead to a slip at the base of portable straight ladders, a major cause of falls from heights. Despite several methods established to help workers achieve the recommended 75.5° angle for ladder set-up, it remains unclear if these methods are used in practice. This study explored ladder set-up behaviours in a field environment. Professional installers of a company in the cable and other pay TV industry were observed for ladder set-up at their worksites. The results showed that the actual angles of 265 ladder set-ups by 67 participants averaged 67.3° with a standard deviation of 3.22°. Although all the participants had training on recommended ladder set-up methods, only 3 out of 67 participants applied these methods in their daily work and even they failed to achieve the desired 75.5° angle. Therefore, ladder set-up remains problematic in real-world situations.

Practitioner Summary: Professional installers of a cable company were observed for portable straight ladder set-up at their worksites. The ladder inclined angle averaged 67.3° with a standard deviation of 3.22°, while the recommended angle is 75.5°. Only a few participants used the methods that they learned during training in their daily work.     

基于Fuzzy ART聚类的卫星在轨姿态监测系统设计

针对传统卫星在轨姿态监测系统无法确定在轨姿态向量与正常向量匹配度,导致姿态角度监测结果不精准的问题,提出基于Fuzzy ART聚类的卫星在轨姿态监测系统设计;系统硬件根据GPS解算方位角和俯仰角,隔离载体扰动;使用MSP430数字/模拟信号转换器,统一CPU指令和寻址模式;使用AS5145B磁角位置编码器输出脉冲信号;通过双轴磁传感器HMC6352的电磁罗盘电路得出卫星在轨姿态大致方向;软件部分利用Fuzzy ART聚类卫星在轨姿态监测数据,确定聚类中心,判定卫星在轨姿态向量与正常向量匹配度,根据匹配结果,开辟新的记忆节点,给出报警信息,完成姿态监测;实验结果表明,所设计系统在轨道圈数为1圈时施加控制力矩,能够迅速使姿态达到稳定;轨道圈数为2圈时,z轴方向的俯仰角与实际三维角度相差1°,表明该系统对卫星在轨姿态监测准确率较高.     

均匀流场中四边形锥柱的压力试验研究

通过水池试验研究了在雷诺数Re为3.19×104~1.15×106,攻角为0°~180°,以15°为间隔,表面倾斜且前后不对称的四边形锥柱状结构在均匀流场中所受的压力载荷。分析了模型所受的周向压力和斯特劳哈尔数Sr随Re和攻角的变化趋势。结果表明:与圆柱绕流相比,倾斜壁面和攻角使压力在背压区和边界层分离点发生变化,同时,Sr也由0.2降到0.13。