Speed Calibration Research Articles

Image-Based Ultrasound Speed Estimation in Isotropic Materials

In Nondestructive Evaluation (NDE), ultrasound imaging is a useful tool for detecting flaws or measuring corrosion in metal pipes. Phased-array systems are becoming standard in NDE, as well as post-processing imaging techniques such as the Total Focusing Method. These techniques require knowledge of parameters such as distance between transducer elements, times of arrival and sound speed to produce sharp images. A deviation in sound speed, for instance, may compromise image accuracy. In this paper, we propose a sound speed estimator based on image quality metrics. The approach consists in generating several reconstructed images from the same acquisition signals, but using a set of candidate sound speeds. The speed value that yields the sharpest image is then chosen as the estimated sound speed. Estimates made on data obtained by simulation of a typical scenario presented relative combined uncertainties as low as 0.0166%. The results, obtained in both simulated and real scenarios, show good agreement with expected speeds. The proposed method can be considered a reference-free sound speed calibration method aimed at field applications.

Validation and Calibration of Significant Wave Height and Wind Speed Retrievals from HY2B Altimeter Based on Deep Learning

HY2B is now the latest altimetry mission that provides global nadir significant wave height (SWH) and sea surface wind speed. The validation and calibration of HY2B are carried out against National Data Buoy Center (NDBC) buoy observations from April 2019 to April 2020. In general, the HY2B altimeter measurements agree well with buoy observation, with scatter index of 9.4% for SWH, and 15.1% for wind speed. However, we observed a significant bias of 0.14 m for SWH and −0.42 m/s for wind speed. A deep learning technique is novelly applied for the calibration of HY2B SWH and wind speed. Deep neural network (DNN) is built and trained to correct SWH and wind speed by using input from parameters provided by the altimeter such as sigma0, sigma0 standard deviation (STD). The results based on DNN show a significant reduction of the bias, root mean square error (RMSE), and scatter index (SI) for both SWH and wind speed. Several DNN schemes based on different combination of input parameters have been examined in order to obtain the best model for the calibration. The analysis reveals that sigma0 STD is a key parameter for the calibration of HY2B SWH and wind speed.

Speed Calibration and Traceability for Train-Borne 24 GHz Continuous-Wave Doppler Radar Sensor

The 24 GHz continuous-wave (CW) Doppler radar sensor (DRS) is widely used for measuring the instantaneous speed of moving objects by using a non-contact approach, and has begun to be used in train-borne movable speed measurements in recent years in China because of its advanced performance. The architecture and working principle of train-borne DRSs with different structures including single-channel DRSs used for freight train speed measurements in railway freight dedicated lines and dual-channel DRSs used for speed measurements of high-speed and urban rail trains in railway passenger dedicated lines, are first introduced. Then, the disadvantages of two traditional speed calibration methods for train-borne DRS are described, and a new speed calibration method based on the Doppler shift signal simulation by imposing a signal modulation on the incident CW microwave signal is proposed. A 24 GHz CW radar target simulation system for a train-borne DRS was specifically realized to verify the proposed speed calibration method for a train-borne DRS, and traceability and performance evaluation on simulated speed were taken into account. The simulated speed range of the simulation system was up to (5~500) km/h when the simulated incident angle range was within the range of (45 ± 8)°, and the maximum permissible error (MPE) of the simulated speed was ±0.05 km/h. Finally, the calibration and uncertainty evaluation results of two typical train-borne dual-channel DRS samples validated the effectiveness and feasibility of the proposed speed calibration approach for a train-borne DRS with full range in the laboratory as well as in the field.

Developing a revised social force model for pedestrians’ earthquake emergency evacuation

After earthquake, the correct and efficient earthquake emergency evacuation of pedestrian is crucial for reducing casualties. Based on the research on the quantitative of panic coefficient and the calibration of initial desired speed, this research has constructed the revised social force model which could accurately simulate the post-earthquake evacuation process of the crowed. Using the revised social force model, the effects of classroom layout, seismic intensity, the number of safeties exits and the number of students in the classroom on the evacuation efficiency are further studied. And then, according to the research results, the classroom layout has been further optimized to improve the students’ earthquake emergency evacuation efficiency. These research results are scientific bases for the targeted earthquake emergency safety education and the design of classroom layout.

Calibration and Cross Validation of Global Ocean Wind Speed Based on Scatterometer Observations

AbstractGlobal ocean wind speed observed from seven different scatterometers, namely, ERS-1, ERS-2, QuikSCAT, MetOp-A, OceanSat-2, MetOp-B, and Rapid Scatterometer (RapidScat) were calibrated against National Data Buoy Center (NDBC) data to form a consistent long-term database of wind speed and direction. Each scatterometer was calibrated independently against NDBC buoy data and then cross validation between scatterometers was performed. The total duration of all scatterometer data is approximately 27 years, from 1992 until 2018. For calibration purposes, only buoys that are greater than 50 km offshore were used. Moreover, only scatterometer data within 50 km of the buoy and for which the overpass occurred within 30 min of the buoy recording data were considered as a “matchup.” To carry out the calibration, reduced major axis (RMA) regression has been applied where the regression minimizes the size of the triangle formed by the vertical and horizontal offsets of the data point from the regression line and the line itself. Differences between scatterometer and buoy data as a function of time were investigated for long-term stability. In addition, cross validation between scatterometers and independent altimeters was also performed for consistency. The performance of the scatterometers at high wind speeds was examined against buoy and platform measurements using quantile–quantile (Q–Q) plots. Where necessary, corrections were applied to ensure scatterometer data agreed with the in situ wind speed for high wind speeds. The resulting combined dataset is believed to be unique, representing the first long-duration multimission scatterometer dataset consistently calibrated, validated and quality controlled.

Surface sediment characteristics related to provenance and ocean circulation in the Drake Passage sector of the Southern Ocean

Understanding present-day sediment provenance and transport processes is crucial for studies about the dynamics of ocean circulation, as well as for paleoclimate reconstructions in the Drake Passage (DP), a key area for Earth's global oceanic circulation and climate during past and future. Based on a comprehensive set of surface sediment samples, we used spatial variations in grain-size distribution, bulk sediment mineralogy, silt and clay mineralogy across the entire DP region to elucidate the terrigenous sources and transport mechanisms. The statistical evaluation of these data identifies southern Patagonia (carbonate, illite, chlorite, feldspar and quartz) and the Antarctic Peninsula (chlorite, smectite, and amphibole) as the main sources for terrigenous sediments in the DP region. Different current systems are transporting the sediment material. Here, we provide a new, robust flow speed calibration for silt grain-sizes to enable the reconstruction of Antarctic Circumpolar Current (ACC) dynamics in the DP sector of the Southern Ocean. We correlated the sortable silt mean grain-size records of surface sediments with adjacent long-term current meter data. A clear bottom current speed pattern shows the variability of the ACC in the DP responding to the dynamics of ocean fronts, in agreement with modern observation.

Rotating-arm method for low speed calibration of hot-wire probes in water applications

An instrument for calibration of hot-wire probes at very low velocities in water applications is introduced. The technique is based on moving a hot-wire probe by means of a rotating-arm device in still water. This simple in situ calibration method is principally beneficial for the investigations of three-dimensional boundary layers which are encountered for instance over rotating disks. In addition to this proposed technique, an existing alternative method in which the calibration is performed against a known reference velocity over a flat surface of a rotating disk is conducted. The comparison of both methods show that the rotating-arm technique is superior to that existing alternative flat-surface calibration method.

High speed imaging method for rotational speed calibration

High speed imaging method for rotational speed calibration

Conceptualizing the sewage collection system for integrated sewer-WWTP modelling and optimization

This paper proposes a new conceptual modelling approach and calibration method for sewer systems, driven by the interest in using the sewer as a bioreactor and long-term biochemical modelling of the integrated system consisting of the sewage collection system and the wastewater treatment plant (WWTP). The new approach consists of a method for simplifying a complex sewer network into a simpler, yet accurate, computationally efficient (conceptual) model able to capture the relevant sewer dynamics, both in terms of water quantity and water quality entering the wastewater treatment plant. Water quality predicted by the conceptual model was assessed using a detailed biochemical process model and compared against a whole-network biochemical model that covers all hydraulic segments and pipes of the sewer system. The conceptual biochemical model achieves very similar results as the whole-network model in terms of water quality, while providing much faster simulation speed (minutes rather than hours) and easy calibration. Given these advantages, the conceptual biochemical model of a collection system can be used in an integrated model with which sewer and WWTP can be simulated simultaneously for long-term evaluation of optimization scenarios. The model was applied to the prediction of the biochemical components, e.g. sulfide, organics and nutrients, which are essential for the control and management of sewer corrosion and pollutant removal.

National-scale Traffic Model Calibration in Real Time with Multi-source Incomplete Data

Real-time traffic modeling at national scale is essential to many applications, but its calibration is extremely challenging due to its large spatial and fine temporal coverage. The existing work is focused on urban-scale calibration with complete field data from single data sources (e.g., loop sensors or taxis), which cannot be generalized to national scale because complete single-source field data at national scale are almost impossible to obtain. To address this challenge, in this article, we design MultiCalib, a model calibration framework to optimize traffic models based on multiple incomplete data sources at national scale in real time. Instead of simply combining multi-source data, we theoretically formulate a multi-source model calibration problem based on real-world contexts and multi-view learning. In particular, we design (i) convex multi-view learning to integrate multi-source data by quantifying biases of data sources, and (ii) context-aware tensor decomposition to infer incomplete multi-source data by extracting real-world contexts. More importantly, we implement and evaluate MultiCalib with two heterogeneous nationwide vehicle networks with 340,000 vehicles to infer traffic conditions on 36 expressways and 119 highways, along with four cities across China. The results show that MultiCalib outperforms baseline calibration by 25% on average with the same input data. Based on the proposed national-scale traffic model calibration, we design a novel dispatching framework integrated with our speed calibration model where we guide a vehicular fleet among national-scale highways with a routing strategy to reduce general traveling time. The results show that a routing strategy based on MultiCalib outperforms a routing strategy based on a state-of-the-art traffic model by 45% on average.

Design of Hot-bulb Probe Low-Pressure Wind Speed Calibration System

In order to measure the wind speed in Mars rover thermal vacuum test correctly, a low-pressure wind speed calibration system need to be developed. The purpose of this paper is to establish a low pressure-wind speed calibration system, and give an error analysis of it. In this paper, the Hot-bulb Probe calibration scheme, calibration conditions are introduced. The errors caused by length measurement and speed measurement, disturbance of low field, measuring instrument are fully analyzed.

Effect of disjunct sampling on calibration of design wind speed

Three main tasks consist of calibrating design wind speed. These include obtaining high quality extreme wind speed records, selecting the most appropriate probabilistic model, and applying the best fitting method to estimate the distribution parameters. The last two aspects have critical impact on the calibrated design wind speeds and have been intensively studied periodically. However, data quality is still the primary factor that affects the reliability of the calibrated design wind speed. The data is typically screened and processed before carrying out extreme value analysis. This includes removing erroneous data and conducting standardization. Besides quality control and standardization, the total number of years of data and the sampling intervals of data in each recording day also need to be considered. The former concern, also known as sample size effect, is well acknowledged and revisited in a recent study. The later concern draws relatively few attentions. One recent study investigated the later concern by using some wind speed observations at ground level. As the sample size is limited, the effect of sample size and disjunct sampling could be mixed in their observation. Moreover, appreciation of the disjunct sampling from sampling theory was not investigated in their study. To better appreciate the impact of disjunct sampling on design wind speed calibration alone, the effect of sample size needs to be eliminated. This requires very long period wind speed records that are not available for historical records. Therefore, this study employs Monte Carlo technique to simulate long term wind speed samples. The simulated wind speeds are used to investigate the impact of disjunct sampling on the design wind speed and the combined effect of disjunct sampling and limited sample size on design wind speed. Effect of disjunct sampling appears in part of the period on the estimated return period wind speeds is also investigated.

A Proposed Calibration Procedure for the Simulation of Wind-Driven Rain in Small-Scale Wind Tunnel

The simulation of wind-driven rain in the wind tunnel should ensure a realistic representation of rainfall events in a laboratory environment. It necessitates therefore an understanding of how the governing input parameters of the tunnel relate to its outputs. In this perspective, a preliminary calibration should be carried out in order to grant the reproduction of a homogeneous volume of rainwater and a natural raindrop size distribution. A precise and straightforward procedure to be followed is missing. Based on experimental investigations, this study outlines a series of calibration steps that should be performed in the wind tunnel before the rain simulation takes place. It applies in particular to small scale facilities as opposed to the large wind tunnels designed for full-scale testing of building components and vehicles. Such procedure concentrates on the following aspects: wind speed calibration by vane anemometer; calibration of the sprinkler system and rain intensity measurements for assessing its spatial distribution. The main findings include the introduction of a governing function for the sprinkler system, a method for rain mapping as well as the individuation of an optimal set-up in the wind tunnel for rain simulation.

Off-Nadir SFMR Brightness Temperature Measurements in High-Wind Conditions

AbstractWind and wave-breaking directions are investigated as potential sources of an asymmetry identified in off-nadir remotely sensed measurements of ocean surface brightness temperatures obtained by the Stepped Frequency Microwave Radiometer (SFMR) in high-wind conditions, including in tropical cyclones. Surface wind speed, which dynamically couples the atmosphere and ocean, can be inferred from SFMR ocean surface brightness temperature measurements using a radiative transfer model and an inversion algorithm. The accuracy of the ocean surface brightness temperature to wind speed calibration relies on accurate knowledge of the surface variables that are influencing the ocean surface brightness temperature. Previous studies have identified wind direction signals in horizontally polarized radiometer measurements in low to moderate (0–20 m s−1) wind conditions over a wide range of incidence angles. This study finds that the azimuthal asymmetry in the off-nadir SFMR brightness temperature measurements is also likely a function of wind direction and extends the results of these previous studies to high-wind conditions. The off-nadir measurements from the SFMR provide critical data for improving the understanding of the relationships between brightness temperature, surface wave–breaking direction, and surface wind vectors at various incidence angles, which is extremely useful for the development of geophysical model functions for instruments like the Hurricane Imaging Radiometer (HIRAD).

Investigation on high rotational speed calibration device

This paper presents the novel implementation of a high rotational speed device for optical tachometer calibration based on brushless DC coreless micro motor and FPGA technology at National Institute of Metrology (NIM), China. The structure of the device and key technology involved were described. The dual closed-loop control solution was explained. For control algorithm, virtual instrument technology is used to build up FPGA hardware from National Instrument and calibration software developed by Lab VIEW. Some calibration results of a laser tachometer are shown in the measurement range from 40000 to 99999 r/min. The expanded calibration uncertainty is 1 × 10−4, k = 2. This high rotational speed calibration device is the first successful technical realization of the measurement unit of r/min (RPM) with resolution of 1 r/min for engineering applications in China and, therefore, used as an important working standard at NIM for the feasible traceability of high-precision optical tachometers national wide at high measurement range above 40000 r/min.

Bicycling Simulator Calibration: Proposed Framework

Bicycling simulation allows for the low-risk experimental study of human factors within transportation environments. A cyclist pedals on a stationary bike trainer, which is instrumented to detect the speed of the wheel and the steering angle of the bicycle. This paper proposes a speed calibration procedure to increase the validity of the simulator results, by using an independent bicycle computer for comparing the simulator speed. The speed ratio, defined as the simulator speed divided by the bike computer speed, approaches one when the simulator is properly calibrated. The effect of tire pressure was analyzed by examining the speed ratio for various tire pressures. The optimal tire pressure was selected as the one that provided a speed ratio closest to one when all other factors were held constant. In the final calibration, a gain factor was used to modify the simulator speed calculation that was embedded in the simulator’s bicycle dynamics model. Following calibration, the final simulation speed was within 99.5% of the bicycle computer speed, indicating that the physical speed of the wheel was accurately modeled in the simulation environment. The calibration procedure uses general equations and techniques that can be applied to other bicycling simulators to calibrate speed measurements and improve the consistency of experimental data worldwide.

Mobile Wind Speed and Wind Direction Measurement System of Train Vehicle

In order to solve the ground fixed wind station can not fully measure the wind field along the railway, mobile wind speed and direction measurement system of train vehicle is required. Which need to be addressed is with the vehicle moves, the result of the measurement system is integrated wind speed, there is a need for measured wind and direction for transformation to get the real result. And the measurement system is installed on the roof of the train, the appropriate measurement method to avoid high-voltage interference is very important. The paper designed a mobile wind speed and direction measurement system by using pore air pressure measure wind speed and direction, realized speed and position measurement through the GPS module, and completed measurement of wind speed and direction data calibration and transmission by microprocessor.

Research on the performance of electro-hydraulic proportional flow valve controlled by active pilot pump

The cartridge flow valves, used in heavy machine and equipment, have the advantages of low leakage, large flow capacity, simple structure, and ease of modulation. However, in order to reduce the influence of load variety on the flow through valve, a pressure differential compensator or a cartridge type flow sensor should be added to the proportional throttle valve. These methods have disadvantages of reducing the flow capacity of valve and increasing the throttling loss. To overcome these disadvantages, a low energy consumption, high controllable electro-hydraulic proportional flow valve which consists of a hydraulic transistor (Valvistor) and a small displacement hydraulic pump driven by a servo motor is proposed firstly in the world. As the pump flow is basically proportional to the pump speed and little influenced by load variety, the flow through main valve is proportional to pilot pump speed. In the research, it’s known that feedback throttle slot pre-opening will cause the decrease of the main valve flow as pressure drop increases. So, small orifices are used instead of the pre-opening of feedback throttle slot to reduce the influence of load variety on the flow through valve. Furthermore, a method of pressure differential changing with pilot pump rotational speed calibration is introduced to further mitigate the influence of pressure difference. In this paper, the mathematical dynamic model of the valve is also established and the stability criterion of valve is derived. The influence of valve parameters and the flow pulsation of pilot pump on valve flow performance is analyzed and simulated. In view of the pilot pump flow pulsation frequency being much higher than the valve natural frequency, the research shows that the influence of flow pulsation of pilot pump on valve flow performance is very little. The research work provides a new method for the large flow electro-hydraulic proportional control system.

気体流速校正設備間比較による校正結果の妥当性評価

気体流速校正設備間比較による校正結果の妥当性評価

Improvements to NIST׳S air speed calibration service

We discuss five significant improvements to the Air Speed Calibration Service conducted by the National Institute of Standards and Technology (NIST): 1. Reduced-uncertainty calibration of the secondary standard [Laser Doppler Anemometer, (LDA)] using a spinning disk, 2. Reduced-uncertainty LDA measurements that account for the position-dependence of the air speed in the test section and for window effects, 3. Improved repeatability, precision, and ease of calibrations by using automated data acquisition and PID air speed control, 4. optical character recognition data acquisition system for anemometers lacking electrical outputs, and 5. up-to-date uncertainty budget of the LDA. Also, we present the results (with uncertainties) of Pitot tube calibrations.