Development of low-cost sensors for structural health monitoring applications

(English) There is increasing interest in developing low-cost sensors for economical structural health monitoring of civil engineering infrastructures. In addition to their price, they have the additional benefit of being easily connected to low-cost microcontrollers such as Arduino. A reliable data acquisition system based on Arduino technology can further lower the cost of data collection and monitoring, enabling long-term monitoring at an affordable cost. This thesis proposes the following four high-precision low-cost monitoring systems.Firstly, to correctly measure structural responses, a Cost Hyper-Efficient Arduino Product (CHEAP) has been developed. CHEAP is a system made up of five synchronized accelerometers connected to an Arduino microcontroller that works as a data collecting device. CHEAP is a uniaxial MEMS accelerometer with a sampling frequency of 85 Hz. To validate its performance, laboratory experiments were carried out and the results were compared with those of two high-precision accelerometers (PCB393A03 and PCB 356B18).Secondly, a unique low-cost inclinometer is presented, the Low-cost Adaptable Reliable Angle-meter (LARA), which measures inclination through the fusion of different sensors: five gyroscopes and five accelerometers. LARA combines a microcontroller based on Internet of Things technology (NODEMCU), allows wireless data transmission, and free commercial software for data collection (SerialPlot). To confirm the precision and resolution of this device, its measurements under laboratory conditions were compared with the theoretical ones and with those of a commercial inclinometer (HI-INC). Laboratory results of a load test on a beam demonstrate LARA's remarkable accuracy. It is concluded that the accuracy of LARA is sufficient for its application in detecting bridge damage.Thirdly, the effect of combining similar range sensors to investigate the increase of the accuracy and mitigation of the ambiental noises, is also elucidated. To investigate the sensor combination theory, a measuring equipment composed of 75 contactless ranging sensors controlled by only two microcontrollers (Arduinos), was built. The 75 sensors are 25 HC-SR04 (analog), 25 VL53L0X (digital), and 25 VL53L1X. (digital). In addition, the impact of various environmental conditions on the standard deviation, distribution functions, and error level of these sensors (HC-SR04, VL53L0X, and VL53L1X) is determined.Finally, a novel remote versatile data acquisition system is presented that allows the recording of time with microsecond resolution for the subsequent synchronization of the acquired data of the wireless sensors located at various points of a structure. This functionality is what would allow its application to static or quasi-static load tests or to the modal analysis of structures. The system developed has a noise density of 51 g/Hz and a sampling frequency of 333 Hz. This device was used to identify the eigenfrequencies and modal analysis of several structures (polvorín footbridges in Barcelona and Andoain Bridge, Donostia-San Sebastian). The comparison of the modal analysis of the Andoain Bridge using the acquired data of the developed accelerometer and data acquisition equipment with those of commercial accelerometers (PCB 607A61) were satisfactory.The low-cost accelerometer, inclinometer and data acquisition system developed and validated in this thesis can make SHM and infrastructure damage detection a reality at low cost, long term and remotely.(Español) Cada vez hay más interés en desarrollar sensores baratos para conocer de manera económica el estado de las infraestructuras civiles. Además de su precio, estos sensores tienen la ventaja añadida de poder conectarse fácilmente a microcontroladores de bajo coste como Arduino. Un sistema fiable de adquisición de datos basado en la tecnología Arduino puede disminuir aún más el coste de la recogida de datos y la monitorización, lo que permitiría una monitorización a largo plazo a un coste asequible. Esta tesis propone los cuatro siguientes sistemas de monitorización de alta precisión y bajo coste.En primer lugar, para medir correctamente las respuestas estructurales, se ha desarrollado el Cost Hyper-Efficient Arduino Product (CHEAP). CHEAP es un sistema compuesto por cinco acelerómetros sincronizados de bajo coste conectados a un microcontrolador Arduino que hace el papel de dispositivo de recogida de datos. CHEAP es un acelerómetro MEMS uniaxial con una frecuencia de muestreo de 85 Hz. Para validar su rendimiento, se efectuaron unos experimentos de laboratorio y sus resultados se compararon con los de dos acelerómetros de alta precisión (PCB393A03 y PCB 356B18). En segundo lugar, se presenta un inclinómetro de bajo coste, un Low-cost Adaptable Reliable Angle-meter (LARA), que mide la inclinación mediante la fusión de distintos sensores: cinco giroscopios y cinco acelerómetros. LARA combina un microcontrolador basado en la tecnología del Internet de las Cosas (NODEMCU), que permite la transmisión inalámbrica de datos, y un software comercial gratuito para la recogida de datos (SerialPlot). Para confirmar la precisión y resolución de este dispositivo, se compararon sus mediciones en condiciones de laboratorio con las teóricas y con las de un inclinómetro comercial (HI-INC). Los resultados de laboratorio de una prueba de carga en una viga demuestran la notable precisión de LARA. Se concluye que la precisión de LARA es suficiente para su aplicación en la detección de daños en puentes.En tercer lugar, también se dilucida el efecto de la combinación de sensores de rango similar para investigar el aumento de la precisión y la mitigación de los ruidos ambientales. Para investigar la teoría de la combinación de sensores, se construyó un equipo de medición compuesto por 75 sensores para la medición de distancias acoplados a dos microcontroladores de Arduino. Los 75 sensores son 25 HC-SR04 (analógicos), 25 VL53L0X (digitales) y 25 VL53L1X (digitales). Además, se determina el impacto de diversas condiciones ambientales en la desviación estándar, las funciones de distribución y el nivel de error de estos sensores.Por último, se presenta un novedoso y versátil sistema de adquisición de datos a distancia que permite el registro del tiempo con una resolución de microsegundos para la sincronización posterior de las lecturas de los sensores inalámbricos situados en diversos puntos de una estructura. Esta funcionalidad es lo que permitiría su aplicación a pruebas de carga estáticas o quasi-estaticas o al análisis modal de las estructuras. El sistema desarrollado tiene una densidad de ruido de 51 g/Hz y una frecuencia de muestreo de 333 Hz. Este dispositivo se utilizó para identificar las frecuencias propias y los modos de vibración de varias estructuras (pasarelas polvorín en Barcelona y Puente de Andoain, Donostia-San Sebastian). Los modos calculados en una de ellas, el Puente de Andoain, a partir de los datos obtenidos con el acelerómetro y sistema de adquisición de datos desarrollado se comparan satisfactoriamente con los de sensores comerciales (PCB 607A61). El acelerómetro, el inclinómetro y el sistema de adquisición de datos de bajo coste desarrollados y validados en esta tesis pueden hacer realidad la SHM y la detección de daños en infraestructuras a bajo coste, a largo plazo y de forma remota.Postprint (published version

Using RPA for performance monitoring of dynamic SHM applications

Robotic Process Automation (RPA) is a source of growing applications in a number of industries both as an individual technology and as a complement to other technologies (such as Internet of Things (IoT)). RPA allows the automation of human activities on a computer, especially when these activities are repetitive and high in volume. RPA saves man-hours and increases the productive capacity of the processes. The application of RPA in civil engineering is still in its early stages, and there has been little work on the subject in the literature. This paper presents RPA technology, for the first time in the literature, as a long-term management, control, and auto fault correction process for a low-cost accelerometer that can be used in SHM applications. However, this process requires a significant number of man-hours to stay operational, given the architecture of its applications. With the application of an RPA implementation workflow formulated based on the Design Science Research Method (DSRM), the management and control of the data acquisition process of a low-cost accelerometer located on a structural column are automated and put into operation in this study. RPA also made it possible to automatically detect and notify users of errors in the process, restart the process, and bring the process back online every time errors occurred. In this way, an automated process was obtained that operated continually and freed up human labour.The Spanish Ministry of Economy and Competitiveness: BIA2017-86811-C2-1-R; The Spanish Ministry of Economy and Competitiveness: BIA2017-86811-C2-2-R; The Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya, Catalunya, Spain: 2017 SGR 1482; Spanish Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant: PRE2018-083238.Peer ReviewedPostprint (published version

Application of low-cost sensors for accurate ambient temperature monitoring

In structures with reduced monitoring budgets, the high cost of commercial metering devices is always an obstacle for monitoring structural health. This might be an issue when temperatures must be measured for both structural and environmental reasons. To fill this gap, in this paper, a novel monitoring system is proposed for the accurate measurement of indoor temperature in buildings. This protocol is characterized by its generality, as it can be easily adapted to measure any structural or environmental parameters on site. The proposed monitoring system uses from one to eight low-cost sensors to obtain multiple measurements of the ambient temperatures. The accuracy ranges of the developed monitoring systems with different numbers of sensors are statistically analysed. The results indicate that the discrepancy of the measurements decreases with the increase in the number of sensors, as the maximum standard deviation of 10 sensors (0.42) decreases to 0.32 and 0.27 for clusters of 20 and 30 sensors, respectively.This research was funded by the Spanish Ministry of Economy and Competitiveness (grant number BIA2013-47290-R, BIA2017-86811-C2-1-R, and BIA2017-86811-C2-2-R) and by the Universidad de Castilla La Mancha (grant number 2018-COB-9092).Peer ReviewedPostprint (published version

DETAILED EVALUATION OF LOW-COST RANGING SENSORS FOR STRUCTURAL HEALTH MONITORING APPLICATIONS

To evaluate the safety of structures, choosing a proper maintains protocol to assess the performance/ workability of the structures in the future, Structural health monitoring (SHM) applications are required. The SHM application usually applies to unique structures with high budgets. For using them on structures with low-budgets low-cost sensors required. Low-cost sensors are getting considerable attention compared with the expensive traditional alternatives. This paper introduces 3 types of low-cost displacement measuring sensors. These sensors were programmed and controlled by an Arduino. Acquiring data from them was done by a connected computer to the Arduino. By engaging these sensors in a few experiments and evaluating their responses, their functionality and accuracy in different situations are investigated. Moreover, the pros and cons of each one of them for each test are illustrated. By taking into account their price, their advantages on exceptional circumstances, and their reliability, different sensors for different situations have been proposedPara evaluar la seguridad de las estructuras, elegir un protocolo de mantenimiento adecuado para evaluar el rendimiento/la viabilidad de las estructuras en el futuro, se requieren aplicaciones de monitorización de la salud estructural (SHM). La aplicación SHM suele aplicarse a estructuras únicas con presupuestos elevados. Para utilizarlas en estructuras con presupuestos bajos se necesitan sensores de bajo coste. Los sensores de bajo coste están recibiendo una atención considerable en comparación con las costosas alternativas tradicionales. En este trabajo se presentan 3 tipos de sensores de medición de desplazamiento de bajo coste. Estos sensores fueron programados y controlados por un Arduino. La adquisición de datos de los mismos se realizó mediante un ordenador conectado al Arduino. Mediante la participación de estos sensores en algunos experimentos y la evaluación de sus respuestas, se investiga su funcionalidad y precisión en diferentes situaciones. Además, se ilustran los pros y los contras de cada uno de ellos para cada prueba. Teniendo en cuenta su precio, sus ventajas en circunstancias excepcionales y su fiabilidad, se han propuesto diferentes sensores para diferentes situacione

Low-cost sensors accuracy study and enhancement strategy

Today, low-cost sensors in various civil engineering sectors are gaining the attention of researchers due to their reduced production cost and their applicability to multiple nodes. Low-cost sensors also have the advantage of easily connecting to low-cost microcontrollers such as Arduino. A low-cost, reliable acquisition system based on Arduino technology can further reduce the price of data acquisition and monitoring, which can make long-term monitoring possible. This paper introduces a wireless Internet-based low-cost data acquisition system consisting of Raspberry Pi and several Arduinos as signal conditioners. This study investigates the beneficial impact of similar sensor combinations, aiming to improve the overall accuracy of several sensors with an unknown accuracy range. The paper then describes an experiment that gives valuable information about the standard deviation, distribution functions, and error level of various individual low-cost sensors under different environmental circumstances. Unfortunately, these data are usually missing and sometimes assumed in numerical studies targeting the development of structural system identification methods. A measuring device consisting of a total of 75 contactless ranging sensors connected to two microcontrollers (Arduinos) was designed to study the similar sensor combination theory and present the standard deviation and distribution functions. The 75 sensors include: 25 units of HC-SR04 (analog), 25 units of VL53L0X, and 25 units of VL53L1X (digital).The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research project BIA2017-86811-C2-1-R, directed by José Turmo, and BIA2017-86811-C2-2-R, directed by Jose Antonio Lozano-Galant. All these projects are funded with FEDER funds. Authors are also indebted to the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya, Catalunya, Spain for the funding provided through Agaur (2017 SGR 1482). It is also to be noted that funding for this research has been provided for Seyedmilad Komarizadehasl by the Spanish Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant (PRE2018-083238).Peer ReviewedPostprint (published version

Low-cost sensors technologies for monitoring sustainability and safety issues in mining activities: advances, gaps, and future directions in the digitalization for smart mining

Nowadays, monitoring aspects related to sustainability and safety in mining activities worldwide are a priority, to mitigate socio-environmental impacts, promote efficient use of water, reduce carbon footprint, use renewable energies, reduce mine waste, and minimize the risks of accidents and fatalities. In this context, the implementation of sensor technologies is an attractive alternative for the mining industry in the current digitalization context. To have a digital mine, sensors are essential and form the basis of Industry 4.0, and to allow a more accelerated, reliable, and massive digital transformation, low-cost sensor technology solutions may help to achieve these goals. This article focuses on studying the state of the art of implementing low-cost sensor technologies to monitor sustainability and safety aspects in mining activities, through the review of scientific literature. The methodology applied in this article was carried out by means of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and generating science mapping. For this, a methodological procedure of three steps was implemented: (i) Bibliometric analysis as a quantitative method, (ii) Systematic review of literature as a qualitative method, and (iii) Mixed review as a method to integrate the findings found in (i) and (ii). Finally, according to the results obtained, the main advances, gaps, and future directions in the implementation of low-cost sensor technologies for use in smart mining are exposed. Digital transformation aspects for data measurement with low-cost sensors by real-time monitoring, use of wireless network systems, artificial intelligence, machine learning, digital twins, and the Internet of Things, among other technologies of the Industry 4.0 era are discussed.The authors are indebted to the projects PID2021-126405OB-C31 and PID2021-126405OB-C32 funded by FEDER funds—A Way to Make Europe and Spanish Ministry of Economy and Competitiveness MICIN/AEI/10.13039/501100011033/. The financial support of the Research Department of the Catholic University of Temuco and the Civil Engineering Department of the University of Castilla-La Mancha is also appreciated.Peer ReviewedPostprint (published version

Laboratory validation of an Arduino based accelerometer designed for SHM applications

Nowadays, low-cost sensors based on low-cost microcontrollers and microprocessors are gaining a lot of attention from researchers. This increasing interest is due to the fact that the implementation of low-cost solutions may make Structural Health Monitoring (SHM) applicable and affordable to structures with a low budget for their SHM. However, many of the present solutions do not have comparable accuracy and resolution with those of the traditional commercial accelerometers. Also, the noise density of these newly developed prototypes has not been checked through laboratory experiments. In fact, the characteristics of the designed and created accelerometer are simply copied from the datasheet of the chipset used to develop the solution. Moreover, the sampling frequency of the majority of the available low-cost solutions usually is lower than 100 Hz. This paper presents a consistent work with the development of a low-cost wireless accelerometer with a sampling frequency of 333 Hz and noise density of 51µg/vHz. This accelerometer's accuracy, noise density, and reliability are evaluated through a series of laboratory experiments. It is essential to mention that this accelerometer does not need any additional data acquisition equipment and is self-sufficient.Postprint (published version

EVALUATION OF LOW-COST ANGULAR MEASURING SENSORS

One of the main issues for performing Structural Health Monitoring (SHM) is the high cost of metering devices. In order to make it applicable to the conventional structures with low defined budgets, low-cost sensors have been widely utilized. In this paper, the characteristics of a low-cost circuit (MPU9250) with low power consumption for measuring angles are studied. This circuit is composed of an accelerometer, a gyroscope, and a magnetometer. There are two ways of coding and using this sensor for angular measurements. In the first application, the accelerometer and the gyroscope of the circuit are only used to get angle around X and Y-axis. In the second application, the gyroscope is going to be added to the other two sensors in order to get angular measurements of all axis. The data accuracy plus the advantages and disadvantages of the response of this circuit regarding each code has been studied in this paper by using the codded sensor in some experiments. Although the second application showed less error from the expected results, it was less stable than the first application.Uno de los principales problemas para llevar a cabo la monitorización de la salud estructural (SHM) es el elevado coste de los dispositivos de medición. Con el fin de para que sea aplicable a las estructuras convencionales con bajos presupuestos definidos, se han utilizado ampliamente sensores de bajo coste. En este trabajo se estudian las características de un circuito de bajo coste (MPU9250) con bajo consumo de energía para la medición de ángulos. estudiado. Este circuito está compuesto por un acelerómetro, un giroscopio y un magnetómetro. Hay dos formas de codificar y utilizar este sensor para las mediciones angulares. En la primera aplicación, el acelerómetro y el giroscopio del circuito sólo se utilizan para obtener el ángulo alrededor de los ejes X e Y. En la segunda aplicación, el giroscopio se añadirá a los otros dos sensores para dos sensores para obtener mediciones angulares de todos los ejes. La precisión de los datos y las ventajas e inconvenientes de de la respuesta de este circuito con respecto a cada código se ha estudiado en este trabajo utilizando el sensor codificado en algunos experimentos. Aunque la segunda aplicación mostró menos error respecto a los resultados esperados, fue menos estable que la primera aplicación

Improving the resolution and accuracy of low-cost Arduino-based accelerometers

An increasing number of researchers are working on Structural Health Monitoring (SHM) applications. However, the high price of traditional commercial accelerometers is known to be one of the significant drawbacks of SHM methods. On the one hand, to apply SHM applications to structures with a lower budget dedicated for their health and safety assessments, development of low-cost sensors can be an answer. On the other hand, low-cost sensors are known to have lower accuracy and resolution compared with those of traditional commercial accelerometers. For the first time in the literature, this paper represents a methodology for improving the resolution and accuracy of low-cost, low-resolution accelerometers. To do so, this paper proposes averaging the outputs of several aligned synchronized low-cost accelerometers. The validity of the proposed methodology has been examined through a series of laboratory experiments. These experiments tested accelerometers made from one, two, three, four and five combined MPU9250 chipsets on a shaking table. Moreover, two commercial accelerometers (393A03 and 356B18) were used to validate the accuracy of the developed solutions.Postprint (published version

A review on low-cost sensors compatible with open-source platforms used for life-cycle monitoring of civil structures

Lately, the need for adopting sensors in buildings and infrastructures for monitoring and inspection of the health state of those structures is increasing. This demand is due to the increasing age of the structural stock worldwide. Consequently, more economical ways of Structural Health Monitoring applications are getting huge attention. This paper presents and evaluates several low-cost electronics compatible with open-source digital technologies for static and dynamic Structural System Identification applications. Firstly, an open-source microcontroller (Arduino), the main programable logic controller, and a Raspberry pi, a small single-board computer, are introduced. Secondly, various economic sensors with diverse measurement applications, such as ultrasonic and laser ranging, acceleration, temperature, and humidity, are discussed. Thirdly, multiple experiments in different controlled ambients are applied to assess and compare their tolerances as well as advantages and disadvantages of their use, among their price. Some problems with the Arduino codes and sensor positions emerged during the installation of the sensors and the data collection process. Finally, to attain an effective manner of using these low-cost electronics, this article offers answers to the issues faced.The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research project BIA2017-86811-C2-1-R directed by José Turmo.This project was funded with FEDER funds. Authors are also indebted to the Secre-taria d’ Universitats i Recerca de la Generalitat de Catalunya for the funding provided through Agaur (2017 SGR 1481). It is also to be noted that funding for this research has been provided for MR. Seyedmilad Komarizadehasl by Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant (PRE2018-083238).Postprint (published version