探究轮静电检测器特征性能

CHARACTERIZING THE PERFORMANCE OF THE WHEEL ELECTROSTATIC SPECTROMETER探究轮静电检测器特征性能Abstract-A Wheel Electrostatic Spectrometer has been developed as a surveying tool to be incorporated into a planetary rover design. Electrostatic sensors with various protruding cover insulators are embedded into a prototype rover wheel. When these insulators come into contact with a surface, a charge develops on the cover insulator through tribocharging. A charge spectrum is created by analyzing the accumulated charge on each of the dissimilar cover insulators. We eventually intend to prove charge spectra can be used to determine differences in planetary regolith properties. We tested the effects of residual surface charge on the cover insulators and discovered a need to discharge the sensor cover insulators after each revolution. We proved the repeatability of the measurements for this sensor package and found that the sensor repeatability lies within one standard deviation of the noise in the signal.摘要我们开发了一款轮静电检测器作为检测工具集成到行星探测器的设计中。有各种不同凸起外壳的静电传感器镶嵌到原型探测器的轮上。当这些传感器与任何表面接触时，因为摩擦生电传感器的外壳绝缘层上就会带电。我们通过分析聚集在每个不同的外壳绝缘层上的电荷编制了电荷谱。我们希望最终证明电荷谱可以用来区别行星表层土的不同特性。我们测验了外壳绝缘层上的残余电荷的影响并且发现每转一圈传感器外壳绝缘层需要清除一次静电。我们证明了这套传感器测量的可重复性并且发现传感器的重复性处于信号中噪声标准差范围内。I. INTRODUCTIONCurrent Martian surface exploration missions incorporate technologies to study the mineral makeup of the Martian regolith in search of volatiles, such as oxygen, that are of great importance for a manned mission to Mars. Volatiles can be extracted from the Martian regolith through In-Situ Resource Utilization (ISRU) processes and used to make drinking water for astronauts and fuel for the return trip to Earth 1. Prior to a manned mission, it is important to determine location and concentrations of these volatiles and minerals. A surveying instrument is necessary to optimize the use of a Martian rover in search of these crucial elements. 简介目前的火星表面探测任务集成了多种技术在搜寻挥发物，如对载人火星任务至关重要的氧气的过程中研究火星表层土的矿物构成。挥发物可以用现场资源设备（ISRU）运行从火星表层土中提取并且用于为宇航员制造饮用水和返回地球过程的燃料【1】。在载人火星任务之前，确定这些挥发物和矿物质的位置和集中度极为重要。优化搜寻这些关键物质的火星探测器使用的勘察设备必不可少。We have developed the Wheel Electrostatic Spectrometer (WES) as a possible surveying tool to be incorporated into a Martian rover design. Electrostatic sensors with various cover insulators are embedded into a prototype wheel to analyze how these insulators charge against other materials. The sensor cover insulators - Teflon, Lucite, G 1 0 and Lexan - were strategically chosen based on their respective locations in the triboelectric series 2. Since each ofthe dissimilar cover insulatorswill charge differently, a charge spectrum is created when tribocharged against the same regolith simulant. In theory, Martian regolith types with different mineral compositions and volatile concentrations will charge the various cover insulators differently, thus allowing scientists to determine when the Martian rover is moving over a different type of regolith 3. In addition, this instrument will enable studies of the Martian electrostatic environment, a subject not yet studied in detail on the Martian surface. It may even be possible to determine the type of regolith that the rover is traversing through a detailed spectral comparison 4. Fig. 1 shows the Wheel Electrostatic Spectrometer.我们开发了轮静电检测器（WES）可集成到火星探测器的设计中。有不同外壳绝缘层的传感器安装到原型轮上用来分析这些绝缘层与其它材料接触时任何带电。这些传感器外壳绝缘层- Teflon, Lucite, G 1 0 和 Lexan都是根据它们在摩擦生电序列表中的位置精心选取的【2】。因为这些不同的外壳绝缘层带电不同，我们编制了它们与相同的模拟火星表层土接触摩擦生电的电荷谱。理论上讲，火星表层土因矿物质组成和挥发物集中程度不同而有不同类型，不同的外壳绝缘层带电也应该不同，因此科学家们可以确定什么时候火星探测器正在哪种不同类型的表层土上移动【3】。此外，这个仪器使火星静电环境的研究成为可能，这个课题还没有在火星表面仔细研究。甚至可能通过谱系比较确定探测器正在移动的地方的表层土的类型【4】。图1.显示这个轮静电检测器。 （图片缺失）Fig. 1. - WES prototype prepared to roll on Martian regolith simulant. The circular insulators are shown protruding from the surface ofthe wheel.图1. 准备碾压模拟火星表层土的轮静电检测器原型。可以看到圆形的绝缘层从轮表面伸出。In this paper, we describe several tests to partially characterize the performance of the previously developed Wheel Electrostatic Spectrometer 2. We examine the need to neutralize the surface charge after each wheel revolution. In addition, we assess the repeatability of the sensor responses.本文描述了几个试验部分地给出了以前开发的轮静电检测器的特征性能【2】。我们探究了轮每转一周就要中和电荷一次的需要。此外，我们还评估了传感器响应的可重复性。II. ELECTRONICSThe electronics for the WES are based on the Mars Environmental Compatibility Assessment (MECA) project. This device was slated to fly on the 2001 Mars Surveyor Lander 5. However, the lander portion of the mission was cancelled and the MECA electrometer was never flown.The signal from each sensor head is sent to a one nF capacitor. The sensing head of the electrometer is made of a pad electrode with two concentric ring electrodes. The inner concentric ring serves as a guard while the outer ring acts as a ground. The voltage generated is amplified andsent to a routine for analysis. Fig. 2 demonstrates the tribocharging process while Fig. 3 displays the sensor head. 电子学原理轮静电检测器的电子学原理基于火星环境兼容性评估（MECA）项目。这个设备被安排到2001年的火星勘察着陆器上【5】。然而，这个任务的着陆器部分被取消，MECA项目从来没有启动。来自传感器探头的信号被发送到一个1nF的电容器。电量计的探头由一个有两个同心环电极的垫构成。内同心环作为一个监测器而外同心环作为接地器。监测到的电压被放大后发送到分析子程序。图2.展示摩擦生电过程，图3.显示传感器探头。 （图片缺失）Fig. 2. - Simplified Electronics Diagram 5. The sensor on the left shows the capacitor state when in contact with the regolith while the sensor diagram on the right displays the capacitor state after the insulator has been tribocharged. （图片缺失）图2. 简化的电子学原理图【5】。左边的传感器显示接触到表层土时的电容状态而右侧的传感器图绝缘层摩擦生电后的电容器状态。 （图片缺失）Fig. 3. - WES electronics sensor head. The sensor head is comprised of a large circular sensing pad and two concentric rings that act as a guard and a ground.图3.轮静电探测器的电子传感器探头。探头由一个大圆形传感垫和两个分别作为监测器和接地器的同心环构成。III. ExperimentsThe experiments presented in this section were conducted in a low humidity environment( 4% RH). The data was taken from each sensor using a National Instruments 9201 Analog Input Module. A LabVIEW program was created to read signals from the analog input module and save the incoming data to a text file. The sampling frequency in each of the presented data sets is 100Hz. The WES was rolled by hand in the discussed experiments. A. Sensor NormalizationSensor normalization was performed to ensure that all sensors had a similar response when exposed to the same electric field. To do this, a probe with rounded edges was placed 3 mm away from each sensor insulator and a Keithley 248 High Voltage Power Supply was used to supply 2 kV to the probe.Fig. 4 displays the response from each sensor.III. 试验本节描述的试验是在低湿度环境（ 4% RH）下进行的。数据是用每个传感器中的National Instruments公司的模拟输入模块9201采集的。我们编制了LabVIEW程序读出来自模拟输入模块的信号并且把读出数据保存成文本文件。对这些数据集的采样频率是100Hz。在这个试验中轮静电检测器是用手转动的。A. 传感器正则化我们进行了传感器正则化来保证所有传感器处在同样的静电场中有相似的响应。为了实现这个目的，我们用一个有圆形刃的探棒放在距传感器绝缘层3mm的地方，用Keithley 248高压电源加2kV电压。 图4. 显示每个传感器的响应（图片缺失）Fig. 4. - 2 kV applied to rounded probe with 3mm gap. Notice a drastic difference in the response voltage from the G I 0 sensor compared to the Teflon and Lexan sensors.图4. 2kV加到圆形探棒上，与传感器间有3mm间隙。注意G I 0传感器与Teflon 和 Lexan传感器的电压响应的不同。Fig. 4 demonstrates that a normalization factor was needed due to the variance in the amplification of each sensor. This variance is possibly the result of a loose resistor tolerance when the circuit was designed. A correction factor was applied to each sensor based on this data. The normalization factors for G I 0, Lexan, Lucite, and Teflon were found to be 1, 1.50, 1.21, and 1.61 , respectively. These normalization factors were verified with an additional test that applied the normalization factors prior to saving the data. Fig. 5 displays the results from this experiment.图4 显示因为每个放大器的分散性我们需要一个正则化系数。这个分散性可能是电路设计时电阻的容差过宽造成的。根据这个结果我们给每个传感器一个修正系数。G I 0, Lexan, Lucite, 和 Teflon 传感器的正则化系数分别为1,1.50,1.21和1.61。这些正则化系数在另外一次试验中得到了验证，在这个试验中数据在保存前都乘以正则化系数了。图5 显示这个试验的结果。 （图片缺失）Fig. 5. - 2 kV applied to rounded probe with approximately 3 mm gap after normalization is applied. The sensors response voltages are nearly identical after the normalization is applied.图5. 正则化后2kV加到圆形探棒上，与传感器间有3mm间隙。正则化后传感器的电压响应几乎相同。As shown in Fig. 5, the normalization factors greatly reduce the variance between the four sensors peak values. It should be noted that the gap distance is slightly greater than in the first experiment, as can be easily shown by the response voltage change in the G I 0 sensor. Minor gap changescause great differences in the sensor response voltages. 如图5 所示，正则化系数大大地减少了四个传感器峰值的分散性。值得注意的是这个间隙比前一个试验的略大一点，在可以G I 0传感器的电压响应变化上很容易地看出。间隙的微小变化会造成传感器电压响应的巨大变化。B. Charge NeutralizationThis experiment was designed to test the need to neutralize the surface charge on the insulators after each wheel revolution. JSCIA lunar simulant was used in each test 7.It should be noted that post processing was completed on each of the data sets displayed. A 6-point moving average was used to improve the signal-to-noise ratio and the normalization factors described in Sensor Normalization were applied.B. 电荷中和本试验是为了检验绝缘层在轮每转一周后需要中和表面电荷而设计的。每次试验都用了JSC1A月球模拟土层【7】。值得注意的是每组数据都经过了后处理。我们用6点移动平均法来改进信噪比并且在用到传感器正则化的地方我们都给出了正则化系数。In the first experiment, the wheel was rolled over the simulant to allow each insulator to be tribocharged. After the 10-second data acquisition period was complete, the capacitor was discharged. While discharging, a 3M Benchtop Air Ionizer was used to neutralize the surface charge on each of the tribocharged insulators. This process was repeated several times. Fig. 6 shows the Lucite sensor response from the previously described experiment.在第一个试验中，轮滚过模拟土层让每个绝缘层摩擦带电。10秒后数据采集周期完成，电容器放电。在放电时，我们用3M公司的Benchtop空气离子发生器来中和每个传感器绝缘层因摩擦带的电荷。这个过程重复了几次。图6显示前面提到的试验中Lucite传感器的响应。（图片缺失）Fig. 6. - Lucite rolled on JSC 1 A lunar simulant. The surface charge was neutralized after each run. Lucite separates from the regolith simulant at approximately 3 seconds. The shape and the magnitude of the sensor response voltage is approximately the same in each trial.图6. Lucite在JSC 1 A模拟月球土层上滚过。每次滚过后表面电荷都中和掉。Lucite传感器大约在3秒后与模拟土层分离。传感器电压响应的形状和幅值在每次试验中都几乎相同。This experiment was repeated without the use of the air ionizer so that the surface charge remained on the insulators after each trial. The capacitor was discharged after each trial. In the first run, the insulator has no surface charge. In all subsequent trials, the residual surface charge remains on the insulator from the previous run. Fig. 7 displays the data from the Lucite sensor from this experiment.这个试验重复几次而没有使用空气离子发生器以便表面电荷在每次试验后都存留在绝缘层上。每次试验后电容器都放电。第一次试验时，绝缘层表面没有电荷。在此后的试验中，前一次试验产生的电荷残留在绝缘层表面。图7 显示在这些试验中Lucite传感器测得的数据。 （图片缺失）Fig. 7. - Lucite rolled on JSCIA simulant. The surface charge was not neutralized after each run. Lucite separates from the regolith simulant at approximately 2.5 seconds.图7. Lucite在JSC 1 A模拟月球土层上滚过。每次试验后表面电荷没有被中和。Lucite传感器大约在2.5秒后与模拟土层分离。Fig. 6 and Fig. 7 illustrate the need for the sensors to be discharged after each revolution. When the surface charges are neutralized, a clear and stable response is observed. When the surface charges are not neutralized, the sensor response peaks with an opposite sign as what should be expected and rapidly returns to a near 0 volt response.This data also demonstrates it may not be necessary to clean the insulators after each revolution. The peak response voltage ofLucite returns to approximately the same value without any cleaning.图6 和图 7 表明每转一周后传感器需要放电。一旦表面电荷被中和，就可以看到一个清晰稳定的响应。一旦表面电荷没有被中和，在响应本该快速归零的地方传感器响应出现一个负的峰值。C. Sensor Response RepeatabilityAnother task to characterize the performance of the WES was to investigate the repeatability of the sensor responses during electrostatic testing. To analyze the electrostatic response repeatability, due care was taken to ensure identical test conditions. The relative humidity was monitored to ensure the level did not exceed 4% during testing. The regolith was mixed after each trial to limit the effects from variation in surface compactness. The insulators surface charges were neutralized prior to each test. Fig. 8 displays a sample of the data from the trials.C. 传感器响应的重复性探究轮静电检测器特征性能的另一个任务是研究在静电试验过程中传感器响应的重复性。为了分析静电响应的重复性，我们非常精心地保证试验条件的同一性。我们监测相对湿度来保证在试验时其水平不超过4%。每次试验后我们都把表层土混合一下以限制表面接触的分散性。绝缘层表面电荷在每次试验前都被中和掉。图8 显示由试验获得的丰富数据。 （图片缺失）Fig. 8. -Comparison of 4 trials. WES was rolled on JSClA lunar simulant. The data demonstrates when these materials are tribocharged against lunar regolith, a level of repeatability can be expected.图 8. 4个试验的比较。轮静电检测器滚过JSC 1 A模拟月球土层。数据表明一旦这些材料与月球土层摩擦生电，就会有一定水平的重复性。The error bars in Fig. 8 represent plus or minus one standard deviation ofthe noise in the first 130 data points, approximately .025 volts for these experiments. Based on the data presented, with the exception of the Teflon sensor, the sensor responses appear to be repeatable within one standard deviation of the noise. Peak voltages lying outside of their respective sensors error bars are likely associated with a non-automated rolling system, allowing for variation in speed of contact, duration of contact, and pressure of contact.图8 中的误差条显示在第一组130个数据点的噪声标准差为正一或负一，在这些试验中大约为0.025伏。根据这些显示的数据，除了Teflon传感器外，其它传感器的响应表现出在一个噪声标准差范围内的重复性。峰值电压在它们对应的传感器的误差条以外的可能与非自动滚动系统有关，这样的系统存在接触速度、时间、和压力的分散性。IV. CONCLUSIONS AND FUTURE WORKWe have shown the sensor responses to be repeatable to within one standard deviation of the noise. We demonstrated the need to neutralize the surface charge on the cover insulators. These experiments also demonstrated that the insulators may not need to be cleaned after each wheel revolution. The electrostatic sensors used in the tests reported here have now been redesigned to increase the signal-to-noise ratio, to make each sensor independent, and to reduce the variance between each sensor. Testing with these new electrostatic sensors is currently underway. Future testing will include rolling WES on a variety of lunar and Martian regolith types to compare the spectral response between simulants. An automated WES rolling system is being developed to increase the repeatability between trials. Based on the data presented in Charge Neutralization, there will be a need for a Martian atmospheric static elimination tool. This tool is currently in the planning stages.IV. 结论和未来的工作我们展示了传感器响应在一个噪声标准差范围内的重复性。我们证明了外壳绝缘层上的电荷需要中和掉。这些试验还证明了轮转一周后绝缘层不必清理。我们提到的试验里用的静电传感器现在已经重新设计了以增加信噪比，保证每个传感器独立并且减少任何两个传感器间的偏差。用这些新传感器进行的试验目前正在进行中。未来的试验将包括在一系列不同类型的月球和火星表层土上滚动轮静电检测器以比较不同模拟表层土的谱响应。我们正在开发一个自动轮静电检测器滚动系统来增加重复性。根据电荷中和中的数据，火星大气静电清除工具是有必要的。这个工具目前正在计划阶段。REFERENCES参考文献1 G.B. 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