• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.9
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• pp.3782-3796
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• 2020

A three-dimensional (3D) reconstruction is an important research area in computer vision. The ability to detect and match features across multiple views of a scene is a critical initial step. The tracking matrix W obtained from a 3D reconstruction can be applied to structure from motion (SFM) algorithms for 3D modeling. We often fail to generate an acceptable number of features when processing face or medical images because such images typically contain large homogeneous regions with minimal variation in intensity. In this study, we seek to locate sufficient matching points not only in general images but also in face and medical images, where it is difficult to determine the feature points. The algorithm is implemented on an adaptive threshold value, a scale invariant feature transform (SIFT), affine SIFT, speeded up robust features (SURF), and affine SURF. By applying the algorithm to face and general images and studying the geometric errors, we can achieve quasi-dense matching points that satisfy well-functioning geometric constraints. We also demonstrate a 3D reconstruction with a respectable performance by applying a column space fitting algorithm, which is an SFM algorithm.

• Journal of Ocean Engineering and Technology
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• v.35 no.6
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• pp.434-445
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• 2021

This paper proposes an optimal design method for an unmanned underwater vehicle (UUV) platform to overcome strong current. First, to minimize the hydrodynamic drag components in water, the vehicle is designed to have a streamlined disc shape, which help maintaining horizontal motion (zero roll and pitch angles posture) while overcoming external current. To this end, four vertical thrusters are symmetrically mounted outside of the platform to stabilize the vehicle's horizontal motion. In the horizontal plane, four horizontal thrusters are symmetrically mounted outside of the disc, and each of them has the same forward and reverse thrust performances. With these four thrusters, a specific thrust vector control (TVC) method is proposed, and for external current in any direction, four horizontal thrusters are controlled to generate a vectored thrust force to encounter the current while minimizing the vehicle's rotation and maintaining its heading. However, for the numerical simulations, the vehicle's hydrodynamic coefficients related to the horizontal plane are derived based on both theoretical and empirically derived formulas. In addition to the simulation, experimental studies in both the water tank and circulating water channel are performed to verify the vehicle's various final performances, including its ability to overcome strong current.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.4_2
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• pp.655-662
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• 2022

Recently, with the increase in the use of UAV(unmanned aerial vehicles), research on horizontal maintenance stations that can take off and land in various environments has been actively conducted. These stations can safely land UAV through multiple DOF(degrees of freedom) or at least 2-DOF-based actuator actuation. Among them, many researchers are dealing with the multi-DOF stewart platform due to its high safety. However, the stewart platform requires high-precision control technology because it requires a lot of torque to actuate according to the load action. Therefore, in this paper, to solve the mentioned problem, a bevel gear-based 2-DOF horizontal maintenance station system is proposed. The proposed system is configured to prevent damage due to air resistance when maintaining ships and to install it in a small space. Also, in terms of system configuration, the bevel gear-based horizontal maintenance system has the main advantage of being able to take off and land UAVs of various sizes through the replacement of station pads. The driving of the system consists of a simple form that can control the motor by adjusting the rotation speed of the motor according to the sea waveform.

• Journal of Ocean Engineering and Technology
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• v.36 no.3
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• pp.181-193
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• 2022

This study presents a mission management technique that is a key component of underwater docking system used to expand the operating range of autonomous underwater vehicle (AUV). We analyzed the docking scenario and AUV operating environment, defining the feasible initial area (FIA) level, event level, and global path (GP) command to improve the rate of docking success and AUV safety. Non-holonomic constraints, mounted sensor characteristic, AUV and mission state, and AUV behavior were considered. Using AUV and docking station, we conducted experiments on land and at sea. The first test was conducted on land to prevent loss and damage of the AUV and verify stability and interconnection with other algorithms; it performed well in normal and abnormal situations. Subsequently, we attempted to dock under the sea and verified its performance; it also worked well in a sea environment. In this study, we presented the mission management technique and showed its performance. We demonstrated AUV docking with this algorithm and verified that the rate of docking success was higher compared to those obtained in other studies.

• Journal of The Korean Association of Information Education
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• v.18 no.3
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• pp.413-422
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• 2014

The positive impacts of robotics education and programming education on learners are similar. However, robotics education differs from programming education because it includes purchasing and building robots that cause financial and cognitive load of learners. Due to these differences, two kinds of education may not possess equal efficacies for all schools or all learning objectives. To verify this hypothesis, we conducted meta-analysis of studies on robotics education published in South Korea to estimate the effect sizes and compare it to that of programming education. The difference between the average effect sizes of robotics education and of programming education was significant, as the former was 0.4060 and the latter 0.6664. The average effect size of programming education was significantly larger than that of robotics education for primary school students. Middle school students achieved the highest results in both robotics education and programming education. Also, robotics education became more effective than programming education as students were older. Analysis on objectives showed that programming education uniformly affected all areas, whereas robotics education had more impact on affective domain than cognitive domain. Robot construction had the largest effect size, followed by robot construction and programming, robot programming, and robot utilization. Programming education has larger positive impacts on students overall compared to robotics education. Robotics education is more effective to upperclassmen than programming education, and improves affective domain of students. Also, robotics education shows higher efficacy when combined with various subjects.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2010-2015
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• 2003

In this paper, a design and control of the safe arm with passive compliant joints(PCJ) is presented. Each PCJ has a magneto- rheological damper and maximum 6 springs. Compliance analysis in Cartesian space is performed with the compliance ellipsoid; this analysis shows a map between compliance in the joint space and compliance in Cartesian space. Vibration control of the arm using an input shaping technique is also presented; the results of a simulation and an experiment prove that a fast motion of the safe arm without residual vibration can be performed.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.803-807
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• 2003

Tele-operation and remote monitoring techniques are essential and important technologies for performing the inspection and repair tasks effectively in nuclear power plants. This paper presents the application of a mobile robot for the remote monitoring and inspection of the Calandria faces, where human access is limited because of the high-level radioactive environments during full power operation. The mobile robot was designed with reconfigurable crawler type of wheels attached on the front and rear side in order to pass through the ditch. The extendable mast, mounted on the mobile robot, can be extended up to 8 m vertically. This robot was also equipped a visible CCD/thermal infrared inspection head module and a stereo camera module for the enhancement of visual inspection.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.185-190
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• 1993

The POSTECH Hand adopting coupled tendon driven technique with planar two fingers is developed. The hand is designed to emulate principal motions of the human hand which has two and three joints respectively. Its kinematic parameters are determined through a parameter optimizing technique to aim at improving the isotropy of fingertip motions with new criterion functions of design. For the control of the hand, tension and torque control algorithms are developed. Based on the virtual stiffness concept, we develop the stiffness control method of a grasped object with redundant finger mechnism and investigate experimentally.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1679-1683
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• 2005

This paper suggests the new type of a joint torque sensor which is attached at each joint of a manipulator for making compliance. Previous six axis force/torque sensors are high cost and installed end-effector of the manipulator. However, torque on links of previous an end-effector cannot be measured. We design a joint torque sensor that can be fully integrated with an actuator in order to measure applying torque of the manipulator. The sensor system is designed through the structural analysis. The proposed joint torque sensors are installed to the 6 DOF manipulator of a mobile robot for hazardous works and we implemented experiments of measuring applied torque to the manipulator. By the experiment, we proved that the proposed low-cost joint torque sensor gives acceptable performance when we control a manipulator.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.290-295
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• 1992

Tendon driven method to drive one joint using two actuators is developed and implemented. While the method has advantages over conventional transmissions, it also has several drawbacks like tendon slack, elongation and endurability. In this paper, a compensation method of the intrinsic non-linearities of tendon is proposed to improve the performance of antagonistic tendon driven method. In this method, tendon tension measurement is prerequisite which is measured with strain gauge type tension sensor. The developed method is implemented on one link test bed with colocated and non-colocated position sensor.