Difference between revisions of "Barotrauma detection system"

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(Created page with "=Quick summary= file:bms_sensor.png|thumb|500px|Figure 1: (a) Geophone and accelerometer installed in a watertight housing mounted on an impact plate and exemplary (b) geoph...")
 
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[[file:bms_vortex_tube2.png|thumb|500px|Figure 3: (a) Vortex tube outlet with mounted sensors and (b) vortex tube running during the field calibration (source: VAW).]]
 
[[file:bms_vortex_tube2.png|thumb|500px|Figure 3: (a) Vortex tube outlet with mounted sensors and (b) vortex tube running during the field calibration (source: VAW).]]
  
Developed by: VAW, ETH Zurich, Switzerland; Test Case partner: Limmatkraftwerke AG, Baden, Switzerland
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Developed by: Centre for Biorobotics, Tallinn University of Technology
  
Date: February 2019
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Date: 2019
  
 
Type: [[:Category:Devices|Device]]
 
Type: [[:Category:Devices|Device]]
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=Introduction=
 
=Introduction=
An indirect Bedload Monitoring System (BMS) is developed for bedload transport monitoring in the vortex tube system installed in the headwater channel of the FIThydro case study hydropower plant (HPP) Schiffmühle. The BMS allows the quantitative assessment of bedload transport in rivers, torrents and hydraulic sediment diversion structures. The measurements support the evaluation of bedload continuity across hydropower plants or other hydraulic structures.
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The BDS sensor housing consists of two POM plastic end caps and a 4 cm outer diameter polycarbonate plastic tube, with a total length of 14 cm, and mass of 150 g (Figure 1). Neutral buoyancy of the BDS is achieved by estimating the water temperature during deployment (±5 °C) and manually adjusting the length of the sensor by screwing the flat end cap inwards or outwards to modify the total sensor volume. Each hemispherical end cap contains three digital total pressure transducers (MS5837-2BA, TE Connectivity, Switzerland) have a sensitivity of 0.0021 kPa (0.21 mm water column) and are linearly rated for 25 m of water depth, and can be used up to 45 m of water depth using a non-linear correction based on laboratory calibration. Each pressure transducer is equipped with its own on-chip temperature sensor, allowing for all pressure readings to include real-time temperature correction using a 2nd order algorithm. All sensors were tested against a HOBO reference pressure sensor under static and dynamic conditions in a laboratory barochamber. The BDS employs a high-speed digital sampling architecture with a 400 kHz clock rate.  
  
The BMS consists of two passive acoustic sensors, i.e. a geophone (GS-20DX manufactured by Geospace Technologies, Houston TX, USA) and an accelerometer (ICP352C03 manufactured by PCB Piezoelectronics, Depew NY, USA), mounted to an impact plate in a watertight housing (Figure 1a). These sensors do not directly measure bedload transport but register the vibration signals of the impact plate, i.e. oscillations induced by the impingement of passing bedload particles. In the case study HPP, the impact plate is the steel wall of the vortex tube (Figure 1a). The vibration signal output of both sensors is a voltage that is sampled at a frequency of fs = 51.2 kHz. The raw signals are then transmitted and further processed (Figure 1b, c).  
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All BDS units are equipped with an atmospheric auto-calibration algorithm. All three transducers are set to a default value of 100 kPa (1000 mbar) at local atmosphere. All sensors are therefore auto-calibrated to local changes in atmospheric pressure which occur during the day, directly before each field deployment. This feature removes the necessity of manually correcting pressure sensor readings.
  
The BMS presented here is similar to the Swiss Plate Geophone System (SPGS) (Rickenmann et al. 2012) but includes an additional accelerometer sensor to expand the range of frequencies and hence the potentially detectable particle sizes compared to the SPGS.
+
The BDS units use three pressure sensors for two reasons. The first is to ensure repeatable field measurements with increased fault tolerance. The BDS uses Triple Modular Redundancy (TMR) by including a pressure sensor array in lieu of a single pressure sensor, whose error and failure cannot be controlled during deployment [1]. The second is that multiple sensors allow for the detection of pressure gradients during passage, which may correspond to regions of high shear.
 +
 
 +
In addition to the three pressure transducers, the BDS sensor also contains a digital 9 degree of freedom inertial measurement unit (IMU) model BNO055 (Bosch Sensortec, Germany) integrating linear accelerometer, gyroscope and magnetometer sensors. In contrast to existing barotrauma sensors, which require extensive post-processing to providing real-time absolute orientation at 100 Hz. The device uses proprietary (Bosch Sensortec, Germany) sensor fusion algorithms to combine the linear accelerometer, gyroscope and magnetometer readings into the body-oriented Euler angles.
  
The maximum amplitude recorded during a bedload transport event can be related to the maximum grain diameter. Additionally, the sum of impulse counts above a certain amplitude threshold can be related to the transported bedload volume. Both relations are BMS setup- and site-dependent and therefore, a calibration is required to correlate the recorded impact signals to known bedload transport rates, often obtained from traditional bedload sampling (Rickenmann et al. 2012). If possible, a calibration in a laboratory flume as well as in the field setting is recommended (Gray et al. 2010, Rickenmann et al. 2014, Wyss et al. 2016a, Wyss et al. 2016b, Albayrak et al. 2017).
 
  
 
=Application=
 
=Application=
Within the scope of FIThydro, a BMS consisting of a geophone and accelerometer was installed on the vortex tube at HPP Schiffmühle, which diverts bedload from the headwater channel to the residual flow reach. The vortex tube consists of a steel tube embedded in the side weir, connecting the two parallel channels (Figure 2). A gate valve is positioned in the side weir, which opens automatically when a predefined discharge is exceeded. The opening of the valve automatically triggers the BMS measurements.
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The sensors are turned on by activating the magnetic switch. Afterwards, they are deployed into the water where they travel through the hydropower plant (Figure 2). Balloon tags inflate, bringing the sensors to the surface, where they are recovered by boat. The data are saved as text files and can be imported into Excel, R, MATLAB and other commonly used software for processing and visualization.
  
In contrast to the SPGS, the steel tube is used as an impact plate for the BMS and the sensors are mounted directly onto the outside of the steel tube (Figure 3). Therefore, laboratory calibration was not easily possible. Instead, the system was calibrated in the field by repeatedly dumping sediment samples of known grain size distribution and volume upstream of the vortex tube and subsequently flushing them to the residual flow reach. In addition, drop tests with single grains were performed when the vortex tube was not in operation. The single grain signals help to analyze the influence of grain size, grain form, drop height, and drop location on the amplitude and frequency signals.
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=Other information=
 
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The cost of each sensor is 500 EUR. Tests at 5 case study sites have shown that an average of 120 data sets per day can be recovered for each hydropower plant operational scenario (e.g. full load, ½ load).
The first results of the presented BMS are promising, but the data analysis will be further refined and extended. Furthermore, a larger number of recorded flood events is necessary to check the plausibility of the results obtained so far. Overall, it is demonstrated that the measurement principle of the state-of-the-art SPGS can be extended to non-standardized impact plates like steel vortex tubes, and the use of an additional accelerometer sensor, given that appropriate calibration measures are taken.
 
  
=Other information=
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<table border="1">
The total costs for the geophone and accelerometer sensors amount to approx. 885-1'330 €. The costs for the field computer, the analog-digital-converter, and the 3G modem are approx. 5'300-6'200 €. Additional costs for the installation, data transmission, and the calibration depending on the site conditions and set-up.
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<caption>Table 1: Technical specifications of the commercial ATS Sensor Fish Model ARC800 and the BDS developed in the FITHydro project.</caption>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p><strong>Physical and sensor specifications</strong></p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p><strong>ATS Sensor Fish Model ARC800</strong></p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p><strong>FITHydro Barotrauma Detection System</strong></p>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p>Physical dimensions</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>89.9 x 24.5 mm (fixed)</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>143 + 1.25 x 40 mm (adjustable)</p>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p>Density</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>1 mg / mm&sup3; (fixed)</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>1.0 mg / mm&sup3; (adjustable)</p>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p>Excess mass (wet weight)</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>0.5 g</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>+/- 1.15 g</p>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p>Sensor sampling rate</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>2048 Hz (analog)</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>400 kHz (digital), saved at 100 or 250 Hz</p>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p>Maximum sampling time</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>4 min</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>240 min</p>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p>3D acceleration</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>0 &ndash; 200 g</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>+/- 16 g</p>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p>3D rotational velocity</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>0 &ndash; 2000 &deg;/s</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>+/- 2067 &deg;/s</p>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p>Pressure</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>0 - 1399.64 kPa (1 sensor)</p>
 +
<p>accuracy: +/- 1.4 kPa</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>0 - 2941 kPa (3 sensors) accuracy: 0.1 kPa</p>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td style="text-align: center;" width="202">
 +
<p>Temperature sensor</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>-40 - 125 &deg;C</p>
 +
<p>(separate sensor for temperature correction)</p>
 +
</td>
 +
<td style="text-align: center;" width="202">
 +
<p>-20 - 85 &deg;C</p>
 +
<p>(temperature correction on each pressure sensor)</p>
 +
</td>
 +
</tr>
 +
</table>
  
 
=Relevant literature=
 
=Relevant literature=

Revision as of 11:56, 18 June 2019

Quick summary

Figure 1: (a) Geophone and accelerometer installed in a watertight housing mounted on an impact plate and exemplary (b) geophone and (c) accelerometer signal of the identical single grain impact. SumIMP denotes the total number of peaks above the threshold amplitude Amin for the event shown. Amaxmax is the maximum amplitude registered during this event. Only positive amplitude values are considered.
Figure 2: (a) Conceptual sketch of the vortex tube functionality and (b) vortex tube outlet at HPP Schiffmühle (source: VAW).
Figure 3: (a) Vortex tube outlet with mounted sensors and (b) vortex tube running during the field calibration (source: VAW).

Developed by: Centre for Biorobotics, Tallinn University of Technology

Date: 2019

Type: Device

Suitable for the following [[::Category:Measures|measures]]:

Introduction

The BDS sensor housing consists of two POM plastic end caps and a 4 cm outer diameter polycarbonate plastic tube, with a total length of 14 cm, and mass of 150 g (Figure 1). Neutral buoyancy of the BDS is achieved by estimating the water temperature during deployment (±5 °C) and manually adjusting the length of the sensor by screwing the flat end cap inwards or outwards to modify the total sensor volume. Each hemispherical end cap contains three digital total pressure transducers (MS5837-2BA, TE Connectivity, Switzerland) have a sensitivity of 0.0021 kPa (0.21 mm water column) and are linearly rated for 25 m of water depth, and can be used up to 45 m of water depth using a non-linear correction based on laboratory calibration. Each pressure transducer is equipped with its own on-chip temperature sensor, allowing for all pressure readings to include real-time temperature correction using a 2nd order algorithm. All sensors were tested against a HOBO reference pressure sensor under static and dynamic conditions in a laboratory barochamber. The BDS employs a high-speed digital sampling architecture with a 400 kHz clock rate.

All BDS units are equipped with an atmospheric auto-calibration algorithm. All three transducers are set to a default value of 100 kPa (1000 mbar) at local atmosphere. All sensors are therefore auto-calibrated to local changes in atmospheric pressure which occur during the day, directly before each field deployment. This feature removes the necessity of manually correcting pressure sensor readings.

The BDS units use three pressure sensors for two reasons. The first is to ensure repeatable field measurements with increased fault tolerance. The BDS uses Triple Modular Redundancy (TMR) by including a pressure sensor array in lieu of a single pressure sensor, whose error and failure cannot be controlled during deployment [1]. The second is that multiple sensors allow for the detection of pressure gradients during passage, which may correspond to regions of high shear.

In addition to the three pressure transducers, the BDS sensor also contains a digital 9 degree of freedom inertial measurement unit (IMU) model BNO055 (Bosch Sensortec, Germany) integrating linear accelerometer, gyroscope and magnetometer sensors. In contrast to existing barotrauma sensors, which require extensive post-processing to providing real-time absolute orientation at 100 Hz. The device uses proprietary (Bosch Sensortec, Germany) sensor fusion algorithms to combine the linear accelerometer, gyroscope and magnetometer readings into the body-oriented Euler angles.


Application

The sensors are turned on by activating the magnetic switch. Afterwards, they are deployed into the water where they travel through the hydropower plant (Figure 2). Balloon tags inflate, bringing the sensors to the surface, where they are recovered by boat. The data are saved as text files and can be imported into Excel, R, MATLAB and other commonly used software for processing and visualization.

Other information

The cost of each sensor is 500 EUR. Tests at 5 case study sites have shown that an average of 120 data sets per day can be recovered for each hydropower plant operational scenario (e.g. full load, ½ load).

Table 1: Technical specifications of the commercial ATS Sensor Fish Model ARC800 and the BDS developed in the FITHydro project.

Physical and sensor specifications

ATS Sensor Fish Model ARC800

FITHydro Barotrauma Detection System

Physical dimensions

89.9 x 24.5 mm (fixed)

143 + 1.25 x 40 mm (adjustable)

Density

1 mg / mm³ (fixed)

1.0 mg / mm³ (adjustable)

Excess mass (wet weight)

0.5 g

+/- 1.15 g

Sensor sampling rate

2048 Hz (analog)

400 kHz (digital), saved at 100 or 250 Hz

Maximum sampling time

4 min

240 min

3D acceleration

0 – 200 g

+/- 16 g

3D rotational velocity

0 – 2000 °/s

+/- 2067 °/s

Pressure

0 - 1399.64 kPa (1 sensor)

accuracy: +/- 1.4 kPa

0 - 2941 kPa (3 sensors) accuracy: 0.1 kPa

Temperature sensor

-40 - 125 °C

(separate sensor for temperature correction)

-20 - 85 °C

(temperature correction on each pressure sensor)

Relevant literature

  • Albayrak, I., Müller-Hagmann, M., Boes, R.M. (2017). Calibration of Swiss Plate Geophone System for bedload monitoring in a sediment bypass tunnel. In Proc. 2nd Intl. Workshop on Sediment Bypass Tunnels (Sumi, T., ed.), paper FP16, Kyoto University, Kyoto, Japan
  • Gray, J.R., Laronne, J.B., Marr, J.D.G. (2010). Bedload-surrogate Monitoring Technologies, US Geological Survey Scientific Investigations Report 2010-5091. US Geological Survey: Reston VA.
  • Rickenmann, D., Turowski, J.M., Fritschi, B., Klaiber, A., Ludwig, A. (2012). Bedload transport measurements at the Erlenbach stream with geophones and automated basket samplers. Earth Surface Processes and Landforms, 37, 1000-1011.
  • Rickenmann, D., Turowski, J.M., Fritschi, B., Wyss, C., Laronne, J., Barzilai, R., Reid, I., Kreisler, A., Aigner, J., Seitz, H., Habersack, H. (2014). Bedload transport measurements with impact plate geophones: comparison of sensor calibration in different gravel-bed streams. Earth Surface Processes and Landforms, 39, 928-942.
  • Wyss, C.R., Rickenmann, D., Fritschi, B., Turowski, J.M, Weitbrecht, V., Boes, R.M. (2016a). Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 1. Impulse counts and particle size identification. Water Resources Research, 52, 7744-7759.
  • Wyss, C.R., Rickenmann, D., Fritschi, B., Turowski, J.M, Weitbrecht, V., Boes, R.M. (2016b). Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 2. Application to field sites with direct bed load samples. Water Resources Research, 52, 7760-7778.


Contact information