• Journal of Welding and Joining
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• v.16 no.3
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• pp.85-94
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• 1998

Welding fabrication invariantly involves three district sequential steps: preparation, actual process execution and post-weld inspection. One of the major problems in automating these steps and developing autonomous welding system, is the lack of proper sensing strategies. Conventionally, machine vision is used in robotic arc welding only for the correction of pre-taught welding paths in single pass. In this paper, developed vision processing techniques are detailed, and their application in welding fabrication is covered. The software for joint tracking system is finally proposed.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.244-244
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• 2000

We proposed the above-knee prosthesis using rotary MR damper in which knee joint is semi-actively controlled by microprocessor. Dissipation torque in the knee joint can be controlled by the magnetic field which is induced by applying current to a solenoid, Tracking control of knee joint angle was tested by 3-DOF Leg simulator. The experimental results show that the proposed above-knee prosthesis system had good performance in swing phase tracking and repetitive controller in conjunction with a computed control law and PD control law, reduced RMS tracking error as the repetitions of tracking. Moreover, desired knee angle trajectory was generated based on the estimation of gait period with the gyro signal and the tracking control was performed.

• International Journal of Korean Welding Society
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• v.4 no.1
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• pp.30-37
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• 2004

There have been continuous efforts on automating welding processes. This automation process could be said to fall into two categories, weld seam tracking and weld quality evaluation. Recently, the attempts to achieve these two functions simultaneously are on the increase. For the study presented in this paper, a vision sensor is made, a vision system is constructed and using this, the 3 dimensional geometry of the bead is measured on-line. For the application as in welding, which is the characteristic of nonlinear process, a fuzzy controller is designed. And with this, an adaptive control system is proposed which acquires the bead height and the coordinates of the point on the bead along the horizontal fillet joint, performs seam tracking with those data, and also at the same time, controls the bead geometry to a uniform shape. A communication system, which enables the communication with the industrial robot, is designed to control the bead geometry and to track the weld seam. Experiments are made with varied offset angles from the pre-taught weld path, and they showed the adaptive system works favorable results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.903-911
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• 1999

A high speed tracking control system for 6-6 Stewart platform manipulator is designed for performing the model based joint-axis sliding mode control. Because of the complex dynamics and kinematics of the Stewart platform manipulator, two computer systems, consisting of a PC and a DSP, are adopted, so that real time tasks are run in synchronous and asynchronous modes. It is experimentally proven that the proposed control system makes the convenience in implementation of model based tracking control, so that it can achieve effective tracking control under relatively high speed and additional payload conditions.

• Journal of Welding and Joining
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• v.18 no.3
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• pp.60-67
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• 2000

In this study, we constructed a preview-sensing visual sensor system for weld seam tracking in GMA welding. The visual sensor consists of a CCD camera, a diode laser system with a cylindrical lens and a band-pass-filter to overcome the degrading of image due to spatters and/or arc light. To obtain weld joint position and edge points accurately from the captured image, we compared Hough transform method with central difference method. As a result, we present Hough transform method can more accurately extract the points and it can be applied to real time weld seam tracking. Image processing is carried out to extract straight lines that express laser stripe. After extracting the lines, weld joint position and edge points is determined by intersecting points of the lines. Although a spatter trace is in the image, it is possible to recognize the position of weld joint. Weld seam tracking was precisely implemented with adopting Hough transform method, and it is possible to track the weld seam in the case of offset angle is in the region of $\pm15^{\circ}$.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.10
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• pp.152-159
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• 1996

We have designed and implemented an optoelectronic hardware of binary phase extraction joint transform correlator (BPEJTC) which provides higher peak-to-sidelobe ratio than many other versions of JTC that has been published so far and does not produce correlation peaks due to intra-class association, to construct a multi-target tracking system. The digital processing unit controlling the entire system plays the part of modifying and binarizing the joint transform power spectrum (JTPS) and the optical processing unit is mainly used to take fourier transform operations. Some experimental results conducted by designed system along with its architecture showed the processing rate of 6 frames per second, thereby the potential applicability of the proposed system to real-time multitarget tracking system is given.

• Journal of Welding and Joining
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• v.19 no.2
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• pp.208-214
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• 2001

In this study, we constructed a visual sensor system for weld seam tracking in real time in GMA welding. A sensor part consists of a CCD camera, a band-pass filter, a diode laser system with a cylindrical lens, and a vision board for inter frame process. We used a commercialized robot system which includes a GMA welding machine. To extract the weld seam we used a inter frame process in vision board from that we could remove the noise due to the spatters and fume in the image. Since the image was very reasonable by using the inter frame p개cess, we could use the simplest way to extract the weld seam from the image, such as first differential and central difference method. Also we used a moving average method to the successive position data or weld seam for reducing the data fluctuation. In experiment the developed robot system with visual sensor could be able to track a most popular weld seam. such as a fillet-joint, a V-groove, and a lap-joint of which weld seam include planar and height directional variation.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.76-82
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• 2000

An arc sensor system to compensate positional errors was developed on the foundation of sensor interface system to make use of the on-line shift function of industrial welding robot. Investigating the on-line shift function, we examine the quantitative relationship between the deviation from programmed path and the correction data transferred from personal computer to robot controller. The number of input parameters for weld seam tracking can be reduced by making the relationship between the deviation and the correction data during half weaving be the function of only cross time. With the results of weld seam tracking for the butt joint with V-groove and fillet joint of sheet metal, good performance was implemented. By developing the sensor interface system to compensate the positional errors, industrial welding robot can be expected to contribute to the promotion of welding automation.

• Laser Solutions
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• v.12 no.1
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• pp.19-24
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• 2009

Because of its fast and precise welding performance, laser welding is becoming a new excellent welding method. However, the precise focusing and robust seam tracking are required to apply laser welding to the practical fields. In order to laser weld a type of T joint like a circular pipe on a square pipe, which could be met in the three dimensional structure such as an aluminum space frame, a visual sensor system was developed for automation of focusing and seam tracking. The developed sensor system consists of a digital CCD camera, a structured laser, and a vision processor. It is moved and positioned by a 2-axis motorized stage, which is attached to a 6 axis robot manipulator with a laser welding head. After stripe-type structured laser illuminates a target surface, images are captured through the digital CCD camera. From the image, seam error and defocusing error are calculated using image processing algorithms which includes efficient techniques handling continuously changed image patterns. These errors are corrected by the stage off-line during welding or teaching. Laser welding of a circular pipe on a square pipe was successful with the vision tracking system by reducing the path positioning and de focusing errors due to the robot teaching or a geometrical variation of specimens and jig holding.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.3
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• pp.204-212
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• 2020

For general target tracking works by receiving a set of measurements from sensor. However, if the SNR(Signal to Noise Ratio) is low due to small RCS(Radar Cross Section), caused by remote small targets, the target's information can be lost during signal processing. TBD(Track Before Detect) is an algorithm that performs target tracking without threshold for detection. That is, all sensor data is sent to the tracking system, which prevents the loss of the target's information by thresholding the signal intensity. On the other hand, using all sensor data inevitably leads to computational problems that can severely limit the application. In this paper, we propose an iterative Joint Integrated Probabilistic Data Association as a practical target tracking technique suitable for a low SNR multi-target environment with real time operation capability, and verify its performance through simulation studies.