RFTacho：旋转机械的非侵入式RF监控
RFTacho: Non-intrusive RF monitoring of rotating machines
摘要：
转速测量在许多工程应用中是必不可少的，它可以消除单独通过振动监测无法检测到的故障，并增强旋转机械振动信号的分析。光学、磁性或机械转速表是目前最先进的转速表。它们的局限性是需要视线，直接接近旋转物体。本文提出了RFTacho，转速测量\emph{system}，利用新的硬件和信号处理算法，方便地产生高精度的读数。RFTacho使用RF轨道角动量（OAM）波同时测量多台机器的转速，对机器的性能没有要求。OAM天线使其能够在工业中常见的高散射环境中工作，因为与线性极化天线相比，它们对去极化具有弹性。RFTacho通过使用两种新颖的信号处理算法来实现这一点，以同时提取多个旋转物体的旋转速度，这些旋转物体存在于高散射环境、非视线场景和动态环境条件下产生的噪声中，分辨率为$1 rpm$。我们在几个真实世界的机器上测试RFTacho，如风扇，电机，空调。结果表明，RFTacho具有平均。$<0.5\%$与地面实况相比的误差。我们展示了RFTacho的同时多目标测量能力，其他转速计没有。初步实验表明，RFTacho可以测量高达7000 rpm（理论上为60000 rpm）的速度，在不同的覆盖距离和方位角下具有高弹性，在5 GHz免许可频段工作时仅需150 mW的发射功率。RFTacho是第一个基于RF的传感系统，它结合了OAM波和新颖的处理方法，以非侵入式方式同时测量多台机器的转速。
英文摘要：
Measuring rotation speed is essential to many engineering applications; it elicits faults undetectable by vibration monitoring alone and enhances the vibration signal analysis of rotating machines. Optical, magnetic or mechanical Tachometers are currently state-of-art. Their limitations are they require line-of-sight, direct access to the rotating object. This paper proposes RFTacho, a rotation speed measurement \emph{system} that leverages novel hardware and signal processing algorithms to produce highly accurate readings conveniently. RFTacho uses RF Orbital Angular Momentum (OAM) waves to measure rotation speed of multiple machines simultaneously with no requirements from the machine's properties. OAM antennas allow it to operate in high-scattering environments, commonly found in industries, as they are resilient to de-polarization compared to linearly polarized antennas. RFTacho achieves this by using two novel signal processing algorithms to extract the rotation speed of several rotating objects simultaneously amidst noise arising from high-scattering environments, non-line-of-sight scenarios and dynamic environmental conditions with a resolution of $1 rpm$. We test RFTacho on several real-world machines like fans, motors, air conditioners. Results show that RFTacho has avg. error of $<0.5\%$ compared to ground truth. We demonstrate RFTacho's simultaneous multiple-object measurement capability that other tachometers do not have. Initial experiments show that RFTacho can measure speeds as high as 7000 rpm (theoretically 60000 rpm) with high resiliency at different coverage distances and orientation angles, requiring only 150 mW transmit power while operating in the 5 GHz license-exempt band. RFTacho is the first RF-based sensing system that combines OAM waves and novel processing approaches to measure the rotation speed of multiple machines simultaneously in a non-intrusive way.
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