Real-time Displacement Monitoring Research Articles

Structural displacement measurement using deep optical flow and uncertainty analysis

Displacement serves as a crucial indicator in the field of structure health monitoring for assessing the condition of civil engineering structures. Computer vision is commonly employed for this purpose due to its cost-effectiveness and convenience. Traditional non-contact computer vision methods, such as optical flow, have been applied to obtain the displacement of bridges. However, real-time monitoring remains challenging due to the computational complexity involved. Therefore, optical flow based on deep learning (referred to as deep optical flow) has gained significant attention. Its main advantage lies in its ability to achieve real-time displacement monitoring, which is of great significance. Furthermore, the accuracy of deep optical flow is comparable to that of traditional optical flow methods for displacement measurement. In this paper, the deep optical flow, RAFT-GOCor, is proposed and applied to extract the displacement of structures, then Bayesian RAFT-GOCor based on Monte Carlo dropout is also presented and applied to analyze the uncertainty of the displacement. The algorithms are verified by laboratory simulated experiments and field bridge loading test. The results indicate that both deep optical flow and uncertainty analysis are feasible methods for measuring structural displacement.

Real-time displacement monitoring using camera video records with camera motion correction

Structure from Motion (SfM) method can reconstruct the story drift ratio, but the camera motion produced by earthquakes reduces the measuring accuracy. This paper improves the applicability of the traditional method by correcting camera motion according to the identification of translation and rotation of camera. Experiments at different levels are designed to prove the proposed method. First, one set of experiments proves the motion correction method by the Single-degree-of-freedom (SDOF) system.The error of maximum response is 4.5% for the case with less rotation. As for the camera motion with larger rotation, the average error increases to 7.9%, which still meets the practical utilization. After that, the accuracy of using SfM method is confirmed by the Multi-degree-of-freedom (MDOF) system with the average error of 4.9%. This paper is expected to extend approaches for the application of the SfM method in the case of huge earthquakes.

GNSS Real-Time Warning Technology for Expansive Soil Landslide—A Case in Ningming Demonstration Area

Efficient monitoring and early warning are the preconditions of realizing expansive soil landslide hazard prevention and control. Previous early warning of expansive soil landslides was evaluated through soil sampling experiments to analyze the stability coefficient. However, the existing methods lack timeliness and ignore the inconsistent deformation characteristics of different parts of the landslide mass. There are still difficulties in the dynamic numerical early warning of landslides at multiple points. Considering that the degradation of expansive soil landslides’ strength is directly reflected by surface displacement, for the Ningming expansive soil demonstration area and based on the GNSS shallow real-time displacement monitoring sequence, a landslide early-warning method based on the GNSS displacement rate combined with the GNSS displacement tangent angle model was proposed, and we thus designed early-warning thresholds for different warning levels. Combined with multi-source data such as soil moisture, soil pressure, and rainfall, the feasibility of accurate early warning of expansive soil landslides based on GNSS real-time surface displacement was verified. The proposed method does not require numerical calculation of internal stress and achieved two successful early warnings of landslides in the test area, which has a certain promotional value.

A Continuous Tilt Sensor Based on UWFBG Technology for Landslide Real-Time Monitoring

Displacement monitoring is the key work of landslide disaster early warning. Distributed and real-time displacement monitoring can provide a more accurate and timely reference for landslide instability evaluation. However, existing technologies have deficiencies in combining distributed and real-time capabilities. Given this, a novel continuous ultra-weak fiber Bragg grating (UWFBG)-based tilt sensor is proposed. First, the tensile test is designed and carried out to investigate the strain transfer mechanism of the UWFBG cable. Then, calibration experiments are used to verify the monitoring performance of the sensors. Finally, the UWFBG tilt sensors are applied in the Majiagou landslide, a typical reservoir landslide located in Three Gorges Reservoir Area (TGRA). The results show that the sliding surface of the landslide is located at 33 m, and the maximum displacement value is 8.1 mm during the monitoring period. When the landslide is in a stable deformation state, the dynamic range of displacement is 1.4 mm. The UWFBG tilt sensors with distributed and real-time monitoring characteristics can achieve accurate landslide displacement measurement and provide outlets for early warning.

Real-Time and Near Real-Time Displacement Monitoring With GNSS Observations in the Mining Activity Areas

Real-Time and Near Real-Time Displacement Monitoring With GNSS Observations in the Mining Activity Areas

Assessment of Real-Time PPP with Trimble RTX correction service for real-time dynamic displacement monitoring based on high-rate GNSS observations

Real-time displacement monitoring of earth crust and engineering structures with the Global Navigation Satellite System (GNSS) is highly important for detecting and preventing the damage and possible loss of life during natural phenomena. Nowadays, the Real-Time Kinematic Precise Point Positioning (RT-PPP) method using a stand-alone GNSS receiver can provide fast and accurate dynamic displacement. Trimble Real-Time Extended (RTX) technology enables real-time precise positioning with cm-level accuracy in a short convergence time. The present study investigates, for the first time, the dynamic displacement detection performance of RT-PPP based on CenterPoint RTX correction service for early warning systems and rapid risk assessment. To evaluate the performance of Trimble RTX technology, a series of shake table experiments were conducted and harmonic oscillations with different frequencies and amplitudes were generated. Trimble RTX solutions were obtained at 20 Hz sampling rate and compared with Linear Variable Differential Transformer (LVDT) data, considered as reference, in both frequency and time domains. Results show that Trimble RTX technology can accurately detect the frequency of harmonic motions, whose amplitudes are slightly different from LVDT values because of GNSS inherent noise. The average of Root Mean Square Error (RMSE) values obtained from the differences between LVDT and filtered RTX-derived time series for all events is 3.6 mm. These results indicated that the CenterPoint RTX technology could be employed for real-time and near-real-time applications to monitor structural and earthquake-induced motions accurately.

Research and Development of Real-time High-precision GNSS Receivers: A Feasible Application for Surveying and Mapping in Vietnam

In recent years, the Global Navigation Satellite System (GNSS) has been widely applied insurveying and mapping. Currently, in Vietnam, dual-frequency GNSS receivers are quite extensivelyapplied with the real-time kinematic (RTK) measurement technique using a continuously operatingreference station network. However, high-accuracy GNSS receivers are often expensive, sometimes notmeeting the needs of users for specific applications. This research develops two types of low-cost highprecisionGNSS receivers for RTK positioning for different purposes. First, the millimeter precisionGNSS receiver used in real-time displacement monitoring is based on Trimble's BD970 mainboardtechnology and some other modules. These components are interconnected according to a standarddesign scheme and assembled in an enclosure to form a GNSS receiver. In addition, a GNSS datatransmission in the National Marine Electronics Association standard format by Networked Transport ofRadio Technical Commission for Maritime Services via Internet Protocol (NTRIP) has beendesigned and developed. The GNSS receiver after development is loaded with program code written inthe C# programming language, using the Arduino programming tool. Second, the GNSS receivers havethe centimeter accuracy for RTK positioning used in surveying and mapping based on U-blox'smainboard technology and some other modules. These modules are also connected together according toa standard design scheme and assembled in an enclosure to form a complete GNSS receiver. Theevaluation results show that the designed and developed GNSS receivers completely meet therequirements of surveying and mapping in coal mines in Vietnam, such as real-time monitoring oflandslides, surveying and topographical mapping and other surveying works to serve the mining process.

Principle and application of in-situ monitoring system for ground displacement induced by shield tunnelling

The ground displacements with complicated distribution induced by metro shield crossing and overlapping construction can significantly influence the stability of surrounding tunnels and structures, which really need to be monitored in practice systematically and exactly. In the present work, a high-accuracy monitoring system at the observation station was developed to precisely and real-timely monitor ground displacements in different depths. The present system combines the static level gauge with a single-point extensometer by platform anchorage, ensuring the real-time displacement monitoring automatically realized with high precision, high frequency and low disturbance. Additionally, a method of spatial coordinate transformation for different subsurface displacements is proposed to obtain the displacement values at the same borehole. The multiple regression analysis method is applied to eliminate the influence of actual unstable construction factors on the monitoring results, and it determines the displacement corrections modified by main factors including the selected monitoring point coordinates and tunnelling parameters. Two case studies in Beijing Subway Line 14 and New Airport Express have shown that the present monitoring method is feasible and suitable to describe the ground displacements under different geological conditions.

Automatic subway tunnel displacement monitoring using robotic total station

Real-time displacement monitoring is important for ensuring the safety of subway tunnel structures when construction activities are carried out near them. Owing to the special environmental characteristics of tunnels, many displacement monitoring techniques are either inapplicable to subway tunnel structures or have limitations in terms of the accuracy and automation of monitoring. Therefore, this article focuses on the automatic monitoring of subway tunnel displacement using robotic total stations. Using prisms as reflectors, the robotic total stations can perform highly accurate displacement monitoring by measuring angles and distances in a non-contact manner. A mathematical model for displacement monitoring with one total station in a short monitoring zone is developed, and a model for monitoring a long tunnel zone with multiple total stations is derived to guarantee the accuracy of monitoring. An automatic displacement monitoring system with robotic total stations is built, where the data acquisition and data management of the system are detailed through its hardware composition and software functions, respectively. An experiment on a tunnel showed the available monitoring range of a single robotic total station, and the accuracy of monitoring the long zone with multiple robotic total stations was verified. The application of the monitoring system to the Guangzhou Metro Line 2 confirmed its robustness.

Pulse Radar with Field-Programmable Gate Array Range Compression for Real Time Displacement and Vibration Monitoring.

This paper aims to present the basic functionality of a radar platform for real time monitoring of displacement and vibration. The real time capabilities make the radar platform useful when live monitoring of targets is required. The system is based on the RF analog front-end of a USRP, and the range compression (time-domain cross-correlation) is implemented on the FPGA included in the USRP. Further processing is performed on the host computer to plot real time range profiles, displacements, vibration frequencies spectra and spectrograms (waterfall plots) for long term monitoring. The system is currently in experimental form and the present paper aims to prove its functionality. The precision of this system is estimated (using the 3σ approximation) at 0.6 mm for displacement measurements and 1.8 mm for vibration amplitude measurements.

Lessons Learned from the Landslides in Shengli East Open-Pit Mine and North Open-Pit Mine in Xilinhot City, Inner Mongolia Province, China

The locations of the 2013 eastern ShengLi open pit mine landslide and the 2010 northern ShengLi open pit mine landslide were both in the XilinHot city of Inner Mongolia province, in areas with similar geographical, regional geological, geomorphic conditions and excavation depth. There are so many similar characteristics, such as landslides triggered by the rain storms, landslides occurred many times, landslides with long time deformation, but there are also some differences between the two landslides, such as the scale and failure mode. Field investigations showed that the two landslides were both occurred several days after the rain storms, the eastern ShengLi open pit mine landslide body with the volume of 85 million m3 has been in persistent deformation with an observed maximum horizontal displacement of 58 m in August 2013, Furthermore the implemented check dams at east open pit mine had not formed an efficacious blocking system to resist the flow because of incorrect judgment regarding the landslide style. The northern ShengLi open pit mine landslide body with 0.5–1 million m3 occurred several times after each rain storm. In the whole, the time of persistent deformation about the eastern ShengLi open pit mine was much longer than that of the northern ShengLi open pit mine because of the difference of the filling material of fault and space combination between the faults and the slope. Field investigation, physical model experiments, real-time displacement monitoring and numerical simulation were implemented to investigate the characteristics, mechanism, and retaining measures of the two landslides. The insights gleaned herein may be valuable for the understanding of the mechanisms of landslides and improving preventative measures against these types of events in north China in the future.

Self-compensating displacement sensor based on hydramatic structured transducer and fiber Bragg grating

An optical fiber displacement sensor with a large measuring range for simultaneous displacement and temperature measurement is presented in this paper. We developed a specific transducer based on the piston and hydraumatic structure to realize a large displacement measurement, which combined the large measuring range and high precision into a single sensor system. The spectrum showed two reflection peaks used to compensate for cross-sensitivity in the displacement detection. This displacement sensor can linearly work in a large measuring displacement range greater than 45 mm with a high sensitivity of 0.036 nm/mm. The sensor we reported can be developed for real-time displacement monitoring in many industrial environments such as the mechanical shape or liquid level monitoring.

Real-time displacement monitoring of a composite stiffened panel subjected to mechanical and thermal loads

Real-time reconstruction of the deformed structural shape using in situ strain measurements is an inverse problem, commonly called shape sensing. The knowledge of the deformed structural shape in real time has important implications for assessing strain, stress, and failure states, and thus constitutes a key component of structural health monitoring. In addition, shape sensing is required for control and actuation of smart structures. In this paper, shape sensing analyses are carried out for typical composite stiffened structures using the inverse Finite Element Method (iFEM). By using a limited set of discrete strain data, iFEM allows full-field reconstruction of displacements that can thus be monitored also far from sensor locations. First, the iFEM theoretical framework and the formulation of a triangular, inverse shell element are briefly discussed. Then, a general strain-sensor configuration amenable to stiffened shell structures is proposed. Several numerical results are presented for static, dynamic, and thermal loadings. The robustness of the method with respect to input errors is also investigated. It is shown that iFEM is a viable methodology for shape sensing of composite stiffened structures, having the desired computational efficiency, accuracy, and robustness with respect to strain-measurement errors. The iFEM shape-sensing methodology is particularly attractive because it does not require any information regarding applied loading, elastic material constants, inertial properties, or damping characteristics.

Wireless Displacement Sensing of Micromachined Spiral-Coil Actuator Using Resonant Frequency Tracking

This paper reports a method that enables real-time displacement monitoring and control of micromachined resonant-type actuators using wireless radiofrequency (RF). The method is applied to an out-of-plane, spiral-coil microactuator based on shape-memory-alloy (SMA). The SMA spiral coil forms an inductor-capacitor resonant circuit that is excited using external RF magnetic fields to thermally actuate the coil. The actuation causes a shift in the circuit's resonance as the coil is displaced vertically, which is wirelessly monitored through an external antenna to track the displacements. Controlled actuation and displacement monitoring using the developed method is demonstrated with the microfabricated device. The device exhibits a frequency sensitivity to displacement of 10 kHz/μm or more for a full out-of-plane travel range of 466 μm and an average actuation velocity of up to 155 μm/s. The method described permits the actuator to have a self-sensing function that is passively operated, thereby eliminating the need for separate sensors and batteries on the device, thus realizing precise control while attaining a high level of miniaturization in the device.

Application of Slope Safety Automatic Monitoring Technology in the Project of Road No.1 in Republic of Congo

Slope safety has been well concerned by the society in recent years. Slope displacement monitoring is an important subject of slope safety and its research has been developing rapidly. In this article, we draw up a pilot slope safety automatic monitoring scheme for the project of Road No.1 in Republic of Congo, which depends on real-time displacement monitoring. This scheme uses fixed inclinometer as its main appliance and achieves wireless data transmission. During this process, we considered both local climate and the characteristics of high slopes along the road, and finished a series of work including monitoring position selection, critical slip surface prediction and finally monitoring system establishment. Our ultimate objective is to achieve real-time monitoring of slope situation, and furthermore set up the relationship among slope displacement, rainfall and time. With the derived relationship we would be able to forecast the development of slope deformation and possible danger caused by the slopes.

Inclinometer Monitoring of the Castelrotto Landslide in Italy

Over the last decades the real-time displacement monitoring systems have been increasingly used for assessing the risk conditions due to landslide movements and for managing the early-warning systems. Any decision about safety actions is therefore based upon the data provided by the instrumentation. The purpose of this work is to suggest how in-place inclinometers may be combined with periodical measurements by using a mobile probe in order to evaluate the current movement of a landslide and to assess the reliability of data. The monitoring system installed at the landslide of Castelrotto (northern Italy) is described, giving some details on the instrumentation and the data collected so far. A local quadratic trend model is developed to estimate the kinematic characteristics of the movement, and a statistical procedure for comparing real-time data with periodical measures is given to assess the reliability of data. This analysis shows how the direction of the displacement may be used as an indicator of reliability.

ＧＰＳ変位モニタリングシステムの連続観測における安定性の検証と計測結果の処理方法の提案

The authors are developing a real-time displacement monitoring system by using the Global Positioning System to assess the stability of large slopes. This paper presents the results of field experiments for long-term continuous measurements and discusses the stability and properties of the data obtained by the system. The measured values include random errors, deviations, and largely scattered errors. In order to choose the acceptable data from the original data, including the above errors, a data processing method is proposed in this paper. Applying the proposed method, the system can provide stable and reliable data.Field experiments for displacement measurements were also conducted to verify the applicability of the system to continuous displacement monitoring. It is concluded that the system can detect at least 5 mm displacements in the horizontal direction and 10 mm displacements in the vertical direction in real time. The accuracy is better than that of the conventional off-line GPS method.