• Journal of Institute of Control, Robotics and Systems
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• v.20 no.2
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• pp.218-222
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• 2014

In this paper, we introduce an autonomous calibration method for a 2D laser displacement sensor (e.g. laser vision sensor and laser range finder) by matching a single point on a flat structure. Many arc welding robots install a 2D laser displacement sensor to expand their application by recognizing their environment (e.g. base metal and seam). In such systems, sensing data should be transformed to the robot's coordinates, and the geometric relation (i.e. rotation and translation) between the robot's coordinates and sensor coordinates should be known for the transformation. Calibration means the inference process of geometric relation between the sensor and robot. Generally, the matching of more than 3 points is required to infer the geometric relation. However, we introduce a novel method to calibrate using only 1 point matching and use a specific flat structure (i.e. circular hole) which enables us to find the geometric relation with a single point matching. We make the rotation component of the calibration results as a constant to use only a single point by moving a robot to a specific pose. The flat structure can be installed easily in a manufacturing site, because the structure does not have a volume (i.e. almost 2D structure). The calibration process is fully autonomous and does not need any manual operation. A robot which installed the sensor moves to the specific pose by sensing features of the circular hole such as length of chord and center position of the chord. We show the precision of the proposed method by performing repetitive experiments in various situations. Furthermore, we applied the result of the proposed method to sensor based seam tracking with a robot, and report the difference of the robot's TCP (Tool Center Point) trajectory. This experiment shows that the proposed method ensures precision.

• Korean Journal of Construction Engineering and Management
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• v.23 no.1
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• pp.64-72
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• 2022

The retaining wall structure is essential for construction work that performs underground excavation. Displacement management of the retaining wall structure is important regardless of the size of the construction. However, in the case of small-scale construction sites with an excavation depth of less than 10m, displacement management of retaining wall structure not properly performed due to problems such as 1) companies' smallness, 2) lack of capacity of construction managers, 3) complexity of installation, dismantling and displacement of measuring instruments. As a result of analyzing previous research, it was analyzed that it is difficult to apply this to a small - scale construction site because most of the previous research has problems in using an expensive 3D scanner or installing many measuring instruments. This study aims to propose a conceptual design of a displacement measurement system for retaining wall structure based on laser sensor and to verify the displacement recognition performance of core technology applied to the conceptual design. A conceptual design was proposed using a 2D laser scanner. As a result of verifying the displacement recognition of the 2D laser scanner, a displacement of 15mm was analyzed to be sufficiently understandable. In the future, if the proposed conceptual design is developed and applied to the small-scale construction site, it is thought that it will contribute to the reduction of safety accidents at small-scale construction sites.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.1250-1251
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• 2022

Measuring management is an important part of preventing the collapse of retaining walls in advance by evaluating their stability with a variety of measuring instruments. The current work of measuring management requires considerable human and material resources since measurement companies need to install measuring instruments at various places on the retaining wall and visit the construction site to collect measurement data and evaluate the stability of the retaining wall. It was investigated that the applicability of the current work of measuring management is poor at small and medium-sized urban construction sites(excavation depth<10m) where measuring management is not essential. Therefore, the purpose of this study is to develop a laser sensor-based hardware to support the wall displacement measurements and their control software applicable to small and medium-sized urban construction sites. The 2D lidar sensor, which is more economical than a 3D laser scanner, is applied as element technology. Additionally, the hardware is mounted on the corner strut of the retaining wall, and it collects point cloud data of the retaining wall by rotating the 2D lidar sensor 360° through a servo motor. Point cloud data collected from the hardware can be transmitted through Wi-Fi to a displacement analysis device (notebook). The hardware control software is designed to control the 2D lidar sensor and servo motor in the displacement analysis device by remote access. The process of analyzing the displacement of a retaining wall using the developed hardware and software is as follows: the construction site manager uses the displacement analysis device to 1)collect the initial point cloud data, and after a certain period 2)comparative point cloud data is collected, and 3)the distance between the initial point and comparison point cloud data is calculated in order. As a result of performing an indoor experiment, the analyses show that a displacement of approximately 15 mm can be identified. In the future, the integrated system of the hardware designed here, and the displacement analysis software to be developed can be applied to small and medium-sized urban construction sites through several field experiments. Therefore, effective management of the displacement of the retaining wall is possible in comparison with the current measuring management work in terms of ease of installation, dismantlement, displacement measurement, and economic feasibility.

• Korean Journal of Construction Engineering and Management
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• v.24 no.2
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• pp.70-78
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• 2023

Inclinometer has several problems of 1)difficulty installing inclinometer casing, 2) measuring 2D local lateral displacement of retaining wall, 3) measurement by manpower. To solve such problems, a 2D LiDAR sensor-based retaining wall displacement measurement system was developed in previous studies. The purpose of this study is to select a displacement analysis algorithm to be applied in the retaining wall displacement measurement system. As a result of the displacement analysis algorithm selection, the M3C2 (Multiple Model to Model Cloud Comparison) algorithm with a displacement estimation error of 2mm was selected as the displacement analysis algorithm. If the M3C2 algorithm is applied in the system and the reliability of the displacement analysis result is secured through several field experiments. Convenient management of the displacement for the retaining wall is possible in comparison with the current measurement management.

• Korean Journal of Construction Engineering and Management
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• v.25 no.3
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• pp.68-82
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• 2024

The planning stage of laser scanning is crucial for acquiring high-quality 3D source data. It involves assessing the target space's environment and formulating an effective measurement strategy. However, existing practices often overlook on-site conditions, with decisions on scanner deployment and scanning locations relying heavily on the operators' experience. This approach has resulted in frequent modifications to scanning locations and diminished 3D data quality. Previous research has explored the selection of optimal scanner locations and conducted preliminary reviews through simulation, but these methods have significant drawbacks. They fail to consider scanner inaccuracies, do not support the use of multiple scanners, rely on less accurate 2D drawings, and require specialized knowledge in 3D modeling and programming. This study introduces an optimization technique for laser scanning planning using 3D simulation to address these issues. By evaluating the accuracy of scan data from various laser scanners and their positioning for scanning a retaining wall structure in a small-scale building, this method aids in refining the laser scanning plan. It enhances the decision-making process for end-users by ensuring data quality and reducing the need for plan adjustments during the planning phase.

• Smart Media Journal
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• v.13 no.3
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• pp.18-26
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• 2024

Road surface monitoring is essential for maintaining road environment safety through managing risk factors like rutting and crack detection. Using autonomous driving-based UGVs with high-performance 2D laser sensors enables more precise measurements. However, the increased energy consumption of these sensors is limited by constrained battery capacity. In this paper, we propose a fusion sensor system for efficient surface monitoring with UGVs. The proposed system combines color information from cameras and depth information from line laser sensors to accurately detect surface displacement. Furthermore, a dynamic sampling algorithm is applied to control the scanning frequency of line laser sensors based on the detection status of monitoring targets using camera sensors, reducing unnecessary energy consumption. A power consumption model of the fusion sensor system analyzes its energy efficiency considering various crack distributions and sensor characteristics in different mission environments. Performance analysis demonstrates that setting the power consumption of the line laser sensor to twice that of the saving state when in the active state increases power consumption efficiency by 13.3% compared to fixed sampling under the condition of λ=10, µ=10.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.1
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• pp.22-31
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• 2002

A Safety Monitoring System using a laser and 2-D arrayed photo sensors is developed. To monitor of the deformation and small rotation of structure the developed optical system using 2-D photo sensor array was used to detect the variation of optical orbit of laser which was induced by deformation of the structure. Also, an operating program to manage the system and an algorithm for the data acquisition and the database are introduced. In this study, we demonstrated the capabilities of this system by laboratory experiments before applying the system to the field.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.447-448
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• 2007

Product development is consisting by trend that accommodate almost function digital cam in camera phone that can speak of Mobile appliance, and competition about number of elemental area of image sensor is consisting for market prior occupation between these. Propose in this research and small size camera phone self-focusing adjustment actuator that do city manufacture is similar with general storehouse pickup actuator drive way, but selected in cylindrical to reduce space that lens holder occupies because there is restriction loading of lens and space enemy. Target number of research established that execute drive displacement more than $600{\mu}m$ in 2.75V that is house voltage that is used in Mobile device that is general. Also, described about maximum transfer displacement characteristic, displacement response characteristic, hysteresis, response characteristic, smallest transfer step characteristic, actuator's drive characteristic that is manufactured to examination item of maximum consumption electric power by special quality estimation system that apply laser displacement sensor that produce itself to evaluate city manufactured actuator's special quality.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.111-117
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• 2003

In the design of the split type free displacer Stilting cryocooler the motion of the displacer is very important to decide the cooling capacity, which depends upon the working gas pressure, the swept volume in the compression space and the expansion space, operating frequency, the phase shift between piston and displacer, etc. In this study, Stirling cryocooler actuated by the electric farce of the dual linear motor is designed and manufactured. Cool down characteristics of the cold end with laser displacement sensor in the expander of the Stilting cryocooler is evaluated. The charging pressure was 15kg$_{f}$/$\textrm{cm}^2$ and operating frequency was 50Hz. Input power and the lowest temperature were about 32W and 67K, respectively. And, displacement of the piston is measured by LVDTs (Linear Variable Differential Transformers), displacement of thedisplacer is measured by laser optic method, and phase shift between piston and displacer is discussed. As the peak-to-peak pressure of the compressor was increased, peak-to-peak displacement of the displacer was increased. The peak-to-peak displacement of the displacer increases in the range of 0 - 64.5Hz(resonant frequency of the displacer), but decreases steeply when the operating frequency is bigger than the resonant frequency. Finally when the phase shift between displacements of the Piston and displacer is 45。, operating frequency is optimum and is decided by resonant frequency of the expander, mass and cross section area of the displacer and constant by friction and flow resistance.e.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.141-141
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• 2017

장미과(Rosaceae)에 속하는 딸기(Fragaria ananassa Duch.)는 비타민 C가 풍부하고 독특한 향기를 갖는 과채류로서 겨울에서 봄까지의 기간 동안 대부분 생식으로 소비되고 있다. 국내에서 재배되는 품종으로는 설향, 매향, 장희 등이 있으며 품종에 따라 성분과 함량이 다양하지만 일반적으로 유기산이 많아서 신맛과 단맛이 조화로운 특징이 있다. 소비자들이 딸기를 구입할 때 딸기가 포장된 상자에 모양이 일정하고 붉은 색상이 선명한 딸기에 호감을 갖게 된다. 딸기는 품종에 따라 기준이 되는 모양이 다르기 때문에 숙련된 선별사에 의해서 대부분 육안으로 선별되고 있는 실정이다. 하지만 개인적인 선별 능력의 차이와 주관적인 판단으로 인해 규격을 벗어난 딸기가 혼입되어 전체적인 품질 등급을 떨어뜨리는 경우가 종종 발생하기도 한다. 따라서 본 연구에서는 품종별로 기준이 되는 표준 형상과 비정상적인 모양의 기형 딸기를 객관적으로 판별하여 선별할 수 있는 영상 시스템을 구축하기 위해 수행되었으며 표준이 되는 딸기의 3차원 형상을 구축하기 위해 2차원 레이저 변위 센서를 이용하여 딸기의 입체 영상을 구축하고자 하였다. 실험을 위해 사용된 딸기는 시중에서 구입한 설향 품종이었으며 2차원 레이저 변위 센서는 라인 스캔 방식으로 1회 프로파일 스캔에 1,280개의 데이터 포인터를 획득할 수 있으며 분해능은 0.095~0.17 mm이었다. 상부에 부착된 2차원 레이저 변위 센서와 하부에 놓인 딸기의 거리는 100 mm였다. 획득한 딸기의 2차원 영상은 높이 차이를 이용하여 색상 농도로 표현하였으며 이 영상을 다시 3차원 영상으로 구축하였다.