Sensor For Inspection Research Articles

Development of a 2 MHz Sonar Sensor for Inspection of Bridge Substructures.

Hydraulic factors account for a large part of the causes of bridge collapse. Due to the nature of the underwater environment, quick and accurate inspection is required when damage occurs. In this study, we developed a 2 MHz side scan sonar sensor module and effective operation technique by improving the limitations of existing sonar. Through field tests, we analyzed the correlation of factors affecting the resolution of the sonar data such as the angle of survey, the distance from the underwater structure and the water depth. The effect of the distance and the water depth and the structure on the survey angle was 66~82%. We also derived the relationship between these factors as a regression model for effective operating techniques. It is considered that application of the developed 2 MHz side scan sonar and its operation method could contribute to prevention of bridge collapses and disasters by quickly and accurately checking the damage of bridge substructures due to hydraulic factors.

Measuring frequency of one-dimensional vibration with video camera using electronic rolling shutter

Cameras offer a unique capability of collecting high density spatial data from a distant scene of interest. They can be employed as remote monitoring or inspection sensors to measure vibrating objects because of their commonplace availability, simplicity, and potentially low cost. A defect of vibrating measurement with the camera is to process the massive data generated by camera. In order to reduce the data collected from the camera, the camera using electronic rolling shutter (ERS) is applied to measure the frequency of one-dimensional vibration, whose frequency is much higher than the speed of the camera. Every row in the image captured by the ERS camera records the vibrating displacement at different times. Those displacements that form the vibration could be extracted by local analysis with sliding windows. This methodology is demonstrated on vibrating structures, a cantilever beam, and an air compressor to identify the validity of the proposed algorithm. Suggestions for applications of this methodology and challenges in real-world implementation are given at last.

Combining a Touch Probe and a Laser Sensor for 3D Part Inspection on CMM

Path planning is a main concern for multi-sensor automated inspection. In this paper, a 3D scanner that combines a laser-sensor and a touch probe is used and mounted on the motorized head of a CMM. Due to this particularity, the path planning is defined in terms of scanner configurations, in which inspection features that could be measured by either the laser-sensor or the touch probe are clustered. For each scanner configuration, the ability of laser-sensor in terms of quality and accessibility is assessed and then the probe ability is assessed before setting the next configuration. The effectiveness of the proposed approach is tested on a part defined by its CAD model.

Development of Quality Inspection Sensor for the Paper Mill Finishing Line

Development of Quality Inspection Sensor for the Paper Mill Finishing Line

Novel design for PIG to eliminate the effect of hydraulic transients in oil and gas pipelines

Hydraulic Transient is one of the most destructive effects in oil and gas pipelines. Currently existing pigs are one of the main sources for this phenomena due to their physical characteristics and function. In this study, by implementation of a new design to the system of pigs, which utilizes the free spaces surrounding the robot, the effect of hydraulic transient is fully eliminated. To demonstrate the practicality and significance of this study, several various simulation experiments such as laminar flow, pressure distribution, velocity variations and stress analysis are conducted on the new design with adjustable arms as well as the former design utilizing sealing disks. The benefit of using adjustable arms exceeds the goal of this research and makes the design extremely versatile by giving it the ability of multi-diameter pipeline inspection and speed maintenance to derive highest resolution for inspection sensors.

Scheduling of two-machine robotic rework cells: In-process, post-process and in-line inspection scenarios

This study focuses on the domain of a two-machine robotic cell scheduling problem under three inspection scenarios. We propose the first analytical method for minimizing the partial cycle time of cells with in-process and post-process inspection scenarios, and then we convert this cell into a multi-function robotic cell with in-line inspection scenario. For the first scenario, parts are inspected in one of the production machines using multiple sensors, while the inspection process is performed by an independent inspection machine for the second scenario. Alternatively, the inspection can be performed by a multi-function robot for the third scenario. A distinguishing characteristic of this robot is that it can perform inspection of the part in transit. However, the robot cannot complete the part transition and load it on the next destination machine if it identifies a fault in the part. The stochastic nature of the process prevents us from applying existing deterministic solution methods for corresponding scheduling problems. In the first stage, we present a heuristic method that converts a multiple-sensor inspection system into a single-sensor inspection system. The expected cycle times of two different cycles are derived based on a geometric distribution, and then the maximum expected throughput is pursued for in-process and post-process inspection sensors, respectively. In the second stage, we develop the inspection system into an in-line inspection system using a multi-function robot. Finally, we determine if it is technically feasible and profitable to replace the in-process (or post-process) inspection scenario with the in-line inspection scenario.

Automatic Detection of Malfunctioning Photovoltaic Modules Using Unmanned Aerial Vehicle Thermal Infrared Images

Cells of a PV (photovoltaic) module can suffer defects due to various causes resulting in a loss of power output. As a malfunctioning cell has a higher temperature than adjacent normal cells, it can be easily detected with a thermal infrared sensor. A conventional method of PV cell inspection is to use a hand-held infrared sensor for visual inspection. The main disadvantages of this method, when applied to a large-scale PV power plant, are that it is time-consuming and costly. This paper presents an algorithm for automatically detecting defective PV panels using images captured with a thermal imaging camera from an UAV (unmanned aerial vehicle). The proposed algorithm uses statistical analysis of thermal intensity (surface temperature) characteristics of each PV module to verify the mean intensity and standard deviation of each panel as parameters for fault diagnosis. One of the characteristics of thermal infrared imaging is that the larger the distance between sensor and target, the lower the measured temperature of the object. Consequently, a global detection rule using the mean intensity of all panels in the fault detection algorithm is not applicable. Therefore, a local detection rule was applied to automatically detect defective panels using the mean intensity and standard deviation range of each panel by array. The performance of the proposed algorithm was tested on three sample images; this verified a detection accuracy of defective panels of 97% or higher. In addition, as the proposed algorithm can adjust the range of threshold values for judging malfunction at the array level, the local detection rule is considered better suited for highly sensitive fault detection compared to a global detection rule. In this study, we used a panel area extraction method that we previously developed; fault detection accuracy would be improved if panel area extraction from images was more precise. Furthermore, the proposed algorithm contributes to the development of a maintenance and repair system for large-scale PV power plants, in combination with a geo-referencing algorithm for accurate determination of panel locations using sensor-based orientation parameters and photogrammetry from ground control points.

On the Safety and Performance Demonstration Tests of Prototype Gen-IV Sodium-Cooled Fast Reactor and Validation and Verification of Computational Codes

Abstract The design of Prototype Gen-IV Sodium-Cooled Fast Reactor (PGSFR) has been developed and the validation and verification (V&V) activities to demonstrate the system performance and safety are in progress. In this paper, the current status of test activities is described briefly and significant results are discussed. The large-scale sodium thermal-hydraulic test program, Sodium Test Loop for Safety Simulation and Assessment-1 (STELLA-1), produced satisfactory results, which were used for the computer codes V&V, and the performance test results of the model pump in sodium showed good agreement with those in water. The second phase of the STELLA program with the integral effect tests facility, STELLA-2, is in the detailed design stage of the design process. The sodium thermal-hydraulic experiment loop for finned-tube sodium-to-air heat exchanger performance test, the intermediate heat exchanger test facility, and the test facility for the reactor flow distribution are underway. Flow characteristics test in subchannels of a wire-wrapped rod bundle has been carried out for safety analysis in the core and the dynamic characteristic test of upper internal structure has been performed for the seismic analysis model for the PGSFR. The performance tests for control rod assemblies (CRAs) have been conducted for control rod drive mechanism driving parts and drop tests of the CRA under scram condition were performed. Finally, three types of inspection sensors under development for the safe operation of the PGSFR were explained with significant results.

A Flexible Arrayed Eddy Current Sensor for Inspection of Hollow Axle Inner Surfaces.

A reliable and accurate inspection of the hollow axle inner surface is important for the safe operation of high-speed trains. In order to improve the reliability of the inspection, a flexible arrayed eddy current sensor for non-destructive testing of the hollow axle inner surface was designed, fabricated and characterized. The sensor, consisting of two excitation traces and 28 sensing traces, was developed by using the flexible printed circuit board (FPCB) technique to conform the geometric features of the inner surfaces of the hollow axles. The main innovative aspect of the sensor was the new arrangement of excitation/sensing traces to achieve a differential configuration. Finite element model was established to analyze sensor responses and to determine the optimal excitation frequency. Experimental validations were conducted on a specimen with several artificial defects. Results from experiments and simulations were consistent with each other, with the maximum relative error less than 4%. Both results proved that the sensor was capable of detecting longitudinal and transverse defects with the depth of 0.5 mm under the optimal excitation frequency of 0.9 MHz.

Novel Rotating Current Probe With GMR Array Sensors for Steam Generate Tube Inspection

This paper presents a novel probe design that uses a rotating current excitation scheme and giant magnetoresi-stance (GMR) sensors for steam generator tube inspection. Rotating eddy currents in the tube wall under test is induced using a pair of axial and circumferential excitation coils. A circumferential array of GMR sensors measures the radial component of the magnetic field. The perturbation in eddy current flow caused by a defect produces a radial component field that is measured by the GMR sensors. A C-scan image of the induced magnetic field obtained with the axial motion of probe shows defect location and orientation. The probe is sensitive to both the axial and circumferential defects and offers the advantages of high sensitivity over a wide frequency range. A finite-element model was developed to mimic the underlying physical process and predict the output images of defects with different orientations and sizes. A prototype unit consisting of excitation coils and GMR sensor array along with a data acquisition system was developed and tested. A steam generator tube sample with machined axial and circumferential notches was inspected using the prototype probe. Experimental results demonstrating the feasibility of the concept are presented.

Magnetoresistive Sensor With Magnetic Balance Measurement for Inspection of Defects Under Magnetically Permeable Fasteners

Magnetoresistive (MR) sensors in conjunction with low-frequency eddy current can be used for detecting subsurface defects under fasteners in aluminum multilayer airframe structures. Frequently, the fasteners are made of magnetically permeable material, e.g. steel, which can be magnetized resulting in a strong remanence. Strong residual magnetism can shift the work point of MR sensor outside of its linear range. The limited measureable range of MR sensor presents additional challenges, since the amplitude of the steel fastener signal is much greater than the defect signal. This paper shows that one can employ magnetic balance measurement (MBM) method to inspect defects under permeable fasteners using MR sensor. The MBM method is based on proportional–integral–derivative feedback control mechanism. The operational principle of MBM was numerically mimicked using a Simulink model. Calculation results show that the bias point of the MR sensor in MBM is kept invariant, so the effect of the strong remanence field is eliminated and the operating point of the sensor on the linear region of its characteristics stays constant. Furthermore, the measurement range of the MR sensor was extended 21 times with given parameters without sacrificing sensitivity. A prototype was built and tested on a two-layer aluminum sample with steel fasteners and machined subsurface notches. Experimental results show that MBM improves the performance of MR sensor for defect inspection around magnetized steel fastener.

Differential Sensor Measurement With Rotating Current Excitation for Evaluating Multilayer Structures

Rotating current probe using rotating electromagnetic fields and currents generated by orthogonal excitation coils is required for achieving similar sensitivity to defects in all radial directions around fastener. However, orthogonal excitation scheme only has a single null field point. When using array sensors for rapid inspection, sensors located away from the point measure a strong background field that must be eliminated. This paper presents a new approach using two giant magnetoresistive sensor arrays in a differential configuration to reduce the impact of the background field and increase signal-to-noise ratio. The operation of the differential probe is validated using a finite-element model. A prototype probe was designed, built, and tested. Experimental results obtained using the prototype probe to inspect a two-layer aluminum sample are presented.

A significant enhancement of color transition from an on-off type achromatic colorimetric nanosensor for highly sensitive multi-analyte detection with the naked eye.

Here, we report the development of an achromatic nanoparticle-based colorimetric sensor (achromatic nanosensor) with an on-off type color change that significantly enhances the color transition and increases the sensitivity of the sensor for naked-eye inspection. The achromatic nanosensor was prepared via a modified CMYK (CRYK) subtractive color model by combining DNA-functionalized gold nanoparticles (AuNPs-DNA), silver nanoparticles (AgNPs-DNA), and gold nanorods (AuNRs-DNA). The initially black-colored achromatic nanosensor not only allowed multiplexed detection by generating target-specific diverse color changes, but also improved the recognition of color changes by the naked eye. Thus, this on-off type color change enabled analysis near the limit of detection (LOD) with the naked eye. In addition, we developed a new image processing method adapted for this achromatic sensor. By quantifying the saturation value of the color images of the achromatic sensor, we could significantly amplify the color signal of the samples, which is difficult to achieve with general colorimetric sensors. The practical application of this achromatic nanosensor for biomarker detection was demonstrated with thrombin and platelet-derived growth factor (PDGF) in human blood plasma. These results provide a new sensing platform that is applicable to most NP-based colorimetric sensing systems for a wide range of applications, including biomolecular diagnosis, chemical pollutant sensing, environmental monitoring, etc.

A Novel Edge Feature Description Method for Blur Detection in Manufacturing Processes

A novel inspection sensor by using an edge feature description (EFD) algorithm based on a support vector machine (SVM) is proposed for industrial inspection of images. This method detects and adaptively segments blurred images by using the proposed algorithm, which uses EFD to effectively classify blurred samples and improve the conventional methods of inspecting blurred objects; the algorithm selects and optimally tunes suitable features. The proposed sensor applies a suitable feature-extraction strategy on the basis of the sensing results. Experimental results demonstrate that the proposed method outperforms the existing methods.

자동차용 볼트의 검사를 위한 시뮬레이션에 기반한 ECT 센서 설계 및 실험적특성

자동차용 볼트의 검사를 위한 시뮬레이션에 기반한 ECT 센서 설계 및 실험적특성

A novel TMR-based MFL sensor for steel wire rope inspection using the orthogonal test method

Magnetic flux leakage (MFL) sensors, with their compact configuration and high sensitivity to small defects, have attracted much attention in recent years for the non-destructive testing of ferromagnetic structures. Tunnel magneto-resistive (TMR) devices have superior performances in sensitivity and linear operation range over conventional magneto-resistive devices. In this paper, a commercial TMR device is employed for developing an electromagnet-based MFL sensor. The electromagnet magnetizer includes Helmholtz-like coils together with a custom-made magnetic shield. The orthogonal test method is applied to aid the structural parameter optimization to the magnetizer based on the finite element analysis results of magnetic field distribution. In this study a prototype of a TMR-based MFL sensor is developed, and its performances on detecting various types of defects are tested on a scanning apparatus. The experimental results show that the MFL signal induced by a blind hole with dimensions of 0.3 mm in both depth and diameter is detectable. In addition, two adjacent notches located more than 2.0 mm from each other can be clearly distinguished from the received MFL signal. The detectable angular detection range for a single TMR device is estimated as 52° in the tested linear shaft rod. The consistency between the simulated and received MFL signal induced by a row of notches inspires confidence in the proposed sensor design method, which in the future can be transplanted for TMR-based sensor array design. Finally, the TMR-based MFL sensor is used for detecting a flaw of a single broken wire with a diameter of 0.5 mm, and the induced MFL signal can be clearly recognized from the oscillation signal that is generated by the twisted rope surface. Therefore, the presented TMR-based MFL sensor has great potential for steel wire rope inspection with enhanced sensitivity to small defects, and it is capable of being integrated into production lines due to its compact configuration.

Investigation on Sensitivity of a Contact-Type Thermal Sensor for Surface Defect Inspections

This paper presents an investigation on the sensitivity of a thermal sensor, which will be used as a contact detection sensor for surface defect inspections. In the proposed concept, frictional heat generated at a slight contact between a defect on a measuring surface and the thermal sensor will be utilized to find out existences of defects on the measuring surface. The frictional heat will be detected as a deviation of the electrical resistance of the sensing element in the thermal sensor. According to the principle, the sensor temperature will increase at the contact with defects. However, in the previous research by the authors, the sensor temperature was found to decrease at the contact with the glass-ball probe, whose tip diameter was on the order of several-ten μm. Following the experiments in the previous study, in this paper, further experimental investigation is carried out by employing an AFM probe as a nano-tip probe so that the sensitivity of the thermal sensor as a contact detection sensor for nano-scale defects inspection can be verified. Furthermore, a possible mechanism of the heat flow at the contact interface, which can explain the results observed in these experiments, is also introduced.

Modal identification of simple structures with high-speed video using motion magnification

Video cameras offer the unique capability of collecting high density spatial data from a distant scene of interest. They can be employed as remote monitoring or inspection sensors for structures because of their commonplace availability, simplicity, and potentially low cost. An issue is that video data is difficult to interpret into a format familiar to engineers such as displacement. A methodology called motion magnification has been developed for visualizing exaggerated versions of small displacements with an extension of the methodology to obtain the optical flow to measure displacements. In this paper, these methods are extended to modal identification in structures and the measurement of structural vibrations. Camera-based measurements of displacement are compared against laser vibrometer and accelerometer measurements for verification. The methodology is demonstrated on simple structures, a cantilever beam and a pipe, to identify and visualize the operational deflection shapes. Suggestions for applications of this methodology and challenges in real-world implementation are given.

An onsite inspection sensor for the formation of hull plates based on active binocular stereovision

Nowadays, the inspection of formed hull plates is still more dependent on wooden templates. The method based on wooden templates is imprecise, inefficiency and costly. In this article, an alternate measurement sensor for onsite inspection of formed hull plates is developed. The sensor can obtain accurate quantitative result with high efficiency. The case study demonstrated that the sensor could substitute wooden templates to inspect formed hull plates in workshop.

Integration of fiber-optic sensors in measuring machines

In last years, optical metrology due to its capability in miniaturization and sensitivity became the primary solution in measurement of complex geometries and fragile pieces. Here, we propose a promising approach to perform highly accurate distance measurements using low-coherence fiber-optic sensors for quality inspection of nozzle orifices in fuel injection systems. In this effort, we develop an adaptive image processing algorithm in MATLAB and install the necessary hardware on a form tester to accelerate and simplify the aligning process. As a result, the repeatability of measurements is one order of magnitude improved while the standard deviation is almost 60% reduced.