Piotr Kohut

Monitoring of a civil structure’s state based on noncontact measurements

In this article, the comparison of two noncontact measurement methods dedicated to civil engineering structures’ state examination is presented. The vision-based method computes the displacement field of the analyzed structure by means of the digital image correlation coefficient. The system consists of one or more high-resolution digital cameras mounted on a head or on portable tripods. The developed methodology and created software application embedded in an MS-Windows operating system are presented. The second system measures the deflection of the structures by means of a radar interferometer. In both cases, it is possible to measure many points on the structure simultaneously. This article presents a comparison of the displacement field measurement performed on a field setup, as well as the span of a steel bridge designed for tram traffic. Both systems are described, with special attention given to their application in measurements of civil engineering structures. This article demonstrates a preliminary test performed to verify both of the noncontact systems in relation to high-accuracy measurement devices, the precise surveying level, and the electronic dial indicator of displacement. The experiment was designed intentionally to simulate the geometric conditions of the real structure, but the displacement values were generated and controlled by the operator. As a key study, a steel viaduct subjected to an operational load was measured, as a type of structure for which the observation is required in terms of structural health monitoring. It was subjected to the operational load caused by tram traffic. Both examined systems were applied. The accuracy analysis of both systems was investigated, and the obtained results were discussed.

Vision based condition assessment of structures

In this paper, a vision-based method for measuring a civil engineering constructions in-plane deflection curves is presented. The displacement field of the analyzed object which results from loads was computed by means of a digital image correlation coefficient. Image registration techniques were introduced to increase the flexibility of the method. The application of homography mapping enabled the deflection field to be computed from two images of the structure, acquired from two different points in space. An automatic shape filter and a corner detector were implemented to calculate the homography mapping between the two views. The developed methodology, created architecture and the capabilities of software tools, as well as experimental results obtained from tests made on a lab set-up and civil engineering constructions, are discussed.

Mobile Laser Scanning Systems for Measuring the Clearance Gauge of Railways: State of Play, Testing and Outlook

The paper contains a survey of mobile scanning systems for measuring the railway clearance gauge. The research was completed as part of the project carried out for the PKP (PKP Polish Railway Lines S.A., Warsaw, Poland) in 2011–2013. The authors conducted experiments, including a search for the latest solutions relating to mobile measurement systems that meet the basic requirement. At the very least, these solutions needed to be accurate and have the ability for quick retrieval of data. In the paper, specifications and the characteristics of the component devices of the scanning systems are described. Based on experiments, the authors did some examination of the selected mobile systems to be applied for measuring the clearance gauge. The Riegl (VMX-250) and Z+F (Zoller + Fröhlich) Solution were tested. Additional test measurements were carried out within a 30-kilometer section of the Warsaw-Kraków route. These measurements were designed so as to provide various elements of the railway infrastructure, the track geometry and the installed geodetic control network. This ultimately made it possible to reduce the time for the preparation of geodetic reference measurements for the testing of the accuracy of the selected systems. Reference measurements included the use of the polar method to select profiles perpendicular to the axis of the track. In addition, the coordinates selected were well defined as measuring points of the objects of the infrastructure of the clearance gauge. All of the tested systems meet the accuracy requirements initially established (within the range of 2 cm as required by the PKP). The tested systems have shown their advantages and disadvantages.

The Project of Tank Inspection Robot

The paper presents the project of tank inspection robot. In order to discuss the designing process, algorithm of design has been provided. There are four design stages: the analysis of the construction problem, the synthesis, testing/improving robots construction and finally testing it. First stage of project process is divided into constructive and imitative analysis. Constructive analysis means searching for still not existing solutions of robots and detection methods. In this paper we concentrate only on constructive analysis.

A structure's deflection measurement and monitoring system supported by a vision system

Abstract In this paper a vision-based method for measuring vertical deflection of large engineering structures under load is presented in example of crane working arm deflection measurements. The deflection is computed by means of a digital image correlation technique embedded in the vision-based system. The results of measurements performed on the vision system were compared with data obtained using a Leica Laser Tracker system. The comparison revealed proper functioning of the developed vision system in industrial conditions.

Structure's Condition Monitoring Based on Optical Measurements

In the paper the vision-based method of civil engineering constructions in-plane deflection measurement and state monitoring is presented. The displacement field of the analyzed structure resulting from a load was computed by means of the digital image correlation coefficient. The application of homography mapping enabled the deflection curve to be computed from two images of the construction acquired from two distinct points in a space. There developed methodology, created software tool as well as experimental results obtained from tests made on lab set-ups and a civil engineering construction are investigated. The experiments are carried out on the lab setup consisting of SRL high resolution digital cameras and the steel frame loaded by a point force. The vision based method results are compared with other contact and non-contact measurement techniques. The deflection of the tram viaduct is investigated and results are compared with the data obtained by the interferometric radar.

Application of Vision Based Damage Detection for Real Civil Engineering Structure

Structural Health Monitoring (SHM) is an emerging field of technology that involves the integration of sensors, data transmission, processing and analysis for detection, as well as localization and assessment of damage which can lead to its failure in the future [1,. In general, SHM methods can be divided into two groups: local and global ones. The second group can be applied if a global change in the geometry of a structure can be observed. In practice, the most commonly used methods of damage detection are based on the analysis of variations in various dynamic properties caused by damage [3,. However, the excitation of large structures can be costly and difficult. The acquisition of static deflection requires much less effort, which makes the damage detection methods based on changes in deflection curves more attractive for practical use [5-1. Damage detection and localization methods require a densely sampled deflection curve.

Application of hot-stage microscopy to evaluating sample morphology changes on heating

Investigations of the thermal properties of a raw material or a ceramic product under a hot-stage microscope allow, among others, determining the characteristic temperatures corresponding to the changes of the shape and the cross-section area of samples being heated. They are based on observing and analysing images of the sample recorded with the growth of its temperature. The pictures of changes allow establishing—for the raw materials with the ability of thermal expansion—the technological temperatures of sintering, softening, thermal expansion, melting and flowing. Their knowledge is necessary in determining optimum ranges of manufacture conditions for a number of ceramic processes. Considering some difficulties with precise determination of these characteristic temperatures and with the problem of measuring the coefficient of thermal expansion S of clay raw materials, the authors have proposed hereby a new method of measuring a sample cross-section area on heating under a hot-stage microscope. It has been invented and implemented in the Matlab software environment on the basis of an image analysis of the expanding sample. The changes of its cross-section area (i.e. an outline area visible under a hot-stage microscope) are continuously recorded on the film and can be converted after digital processing into sample volume changes. The method is applicable to precise measuring the coefficient of thermal expansion S of clay raw materials, among others those used in the manufacture of lightweight ceramic aggregates.

Mechatronics Systems Supported by Vision Techniques

In the paper an application of vision methods and algorithms in various domains that contribute to mechatronics is presented. Regarding mechatronics devices and machines as robots, a vision system employed for a testing station simulating an industrial assembly line is discussed. Some numerical aspects concerning image pre-processing, analysis and geometrical transformations commonly used in robotics were introduced. To accomplish an effective investigation, the developed methodology and algorithms were implemented and verified on an experimental setup composed of two industrial robots and automation devices cooperating with two various vision systems. In the case of underwater robots for tank inspection, image pre-processing and analysis algorithms for the robots position estimation, an image scale calculation and wall crack detection were investigated. An active vibration control system is treated as a mechatronic device which contains mechanical parts, electronics and software. In this example, a visual servoing architecture based on image features for controlling an active vibration control system was examined. For an effective investigation and synthesis of visual servoing algorithms, a MATLAB/Simulink/dSPACE hardware–software environment was employed. A vision system was used to analyze vibration amplitude of the vibro-isolation mass of the active suspension system and to provide a feedback control signal. The connection of 3D vision techniques with modal analysis was shown. Within the confines of the project a methodology for amplitude of vibration measurement and a software tool for modal analysis realization based on visual data were developed. The 3D measurements and structure of the construction were obtained by application and development of passive 3-D vision techniques. From this area, ‘structure from motion’ techniques were developed. In the experimental research, a mechatronic test stand was designed and manufactured enabling automatic two-axis control of a camera. A frame structure was built, in which a guiding-rail system was mounted enabling straight-line motion of a camera. Additionally, a system realizing rotational motion of a camera was built in. To control the experiment stand, software was created enabling the combination of the hardware-software part of the stand with the software part of a vision system. A tool was developed for the purpose of modal analysis and estimation of the quantities characterizing dynamic properties of the structure based on vision signals. As a conclusion, the presented, implemented and tested vision methods in various hardware-software programming platforms are discussed

Experimental assessment of rectification algorithm in vision-based deflection measurement system

Abstract An uncertainty assessment of a vision-based method for the measurement of a structure’s in-plane deflection is presented. In the investigated approach, the displacements of measurement points in the structure under load are computed by means of digital image correlation. The application of homography mapping enables the deflection field to be computed from two images of the structure acquired from distinct points in space. The impact of the camera’s pose and changes in focal length on the performance of the developed vision algorithm is investigated. The paper presents and discusses the influence of rectification algorithm on the quality of the vision-based measurement system as well.