• Journal of KIISE:Software and Applications
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• v.36 no.2
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• pp.131-143
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• 2009

Based on the fact that a human being walks naturally and stably with consuming a minimum energy, this paper proposes a new method of generating a natural gait of 5-link biped robot like human by analyzing a COG (Center Of Gravity) trajectory of human's gait. In order to generate a natural gait pattern for 5-link biped robot, it considers the COG trajectory measured from human's gait images on the sagittal and frontal plane. Although the human and 5-link biped robot are similar in the side of the kinematical structure, numbers of their DOFs(Degree Of Freedom) are different. Therefore, torques of the human's joints cannot are applied to robot's ones directly. In this paper, the proposed method generates the gait pattern of the 5-link biped robot from the GA algorithm which utilize human's ZMP trajectory and torques of all joints. Since the gait pattern of the 5-link biped robot model is generated from human's ones, the proposed method creates the natural gait pattern of the biped robot that minimizes an energy consumption like human. In the side of visuality and energy efficiency, the superiority of the proposed method have been improved by comparative experiments with a general method that uses a inverse kinematics.

• Journal of the Korea Computer Graphics Society
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• v.27 no.5
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• pp.1-11
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• 2021

The purpose of our research is to efficiently deform a 3D models which is composed of a triangular mesh and a skeleton. We designed a novel inverse kinematics (IK) solver that calculates the updated positions of mesh vertices with fewer computing operations. Through our user interface, one or more markers are selected on the surface of the model and their target positions are set, then the system updates the positions of surface vertices to construct a deformed model. The IK solving process for updating vertex positions includes many computations for obtaining transformations of the markers, their affecting joints, and their parent joints. Many of these computations are often redundant. We precompute those redundant terms in advance so that the 3-nested loop computation structure was improved to a 2-nested loop structure, and thus the computation time for a deformation is greatly reduced. This novel IK solver can be adopted for efficient performance in various research fields, such as handling 3D models implemented by LBS method, or object tracking without any markers.

• Journal of the Korea Computer Graphics Society
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• v.29 no.3
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• pp.69-77
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• 2023

This study proposes a rigid-body tracking based virtual avatar application method to increase the social presence and provide various experiences of virtual reality(VR) users in an immersive virtual environment. The proposed method estimates the motion of a virtual avatar through inverse kinematics based on real-time rigid-body tracking based on motion capture using markers. Through this, it aims to design a highly immersive virtual environment with simple object manipulation in the real world. Science experiment educational contents are produced to experiment and analyze applications related to immersive virtual environments through virtual avatars. In addition, audiovisual education, full-body tracking, and the proposed rigid-body tracking method were compared and analyzed through survey. In the proposed virtual environment, participants wore VR HMDs and conducted a survey to confirm immersion and educational effects from virtual avatars performing experimental educational actions from estimated motions. As a result, through the method of utilizing virtual avatars based on rigid-body tracking, it was possible to induce higher immersion and educational effects than traditional audiovisual education. In addition, it was confirmed that a sufficiently positive experience can be provided without much work for full-body tracking.

• Korean Journal of Applied Biomechanics
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• v.16 no.2
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• pp.1-8
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• 2006

The purpose of this study was to evaluate normalized jerk according to shoes, slope, and velocity during walking. Eleven different test subjects used three different types of shoes (running shoes, mountain climbing boots, and elevated forefoot walking shoes) at various walking speeds(1.19, 1.25, 1.33, 1.56, 1.78, 1.9, 2, 2.11, 2.33m/sec) and gradients(0, 3, 6, 10 degrees) on a treadmill. Since there were concerns about using the elevated forefoot shoes on an incline, these shoes were not used on a gradient. Motion Analysis (Motion Analysis Corp. Santa Rosa, CA USA) was conducted with four Falcon high speed digital motion capture cameras. Utilizing the maximum smoothness theory, it was hypothesized that there would be differences in jerk according to shoe type, velocity, and slope. Furthermore, it was assumed that running shoes would have the lowest values for normalized jerk because subjects were most accustomed to wearing these shoes. The results demonstrated that elevated forefoot walking shoes had lowest value for normalized jerk at heel. In contrast, elevated forefoot walking shoes had greater normalized jerk at the center of mass at most walking speeds. For most gradients and walking speeds, hiking boots had smaller medio-lateral directional normalized jerk at ankle than running shoes. These results alluded to an inverse ratio for jerk at the heel and at the COM for all types of shoes. Furthermore, as velocity increased, medio-lateral jerk was reduced for all gradients in both hiking boots and running shoes. Due to the fragility of the ankle joint, elevated forefoot walking shoes could be recommended for walking on flat surfaces because they minimize instability at the heel. Although the elevated forefoot walking shoes have the highest levels of jerk at the COM, the structure of the pelvis and spine allows for greater compensatory movement than the ankle. This movement at the COM might even have a beneficial effect of activating the muscles in the back and abdomen more than other shoes. On inclines hiking boots would be recommended over running shoes because hiking boots demonstrated more medio-lateral stability on a gradient than running shoes. These results also demonstrate the usefulness of normalized jerk theory in analyzing the relationship between the body and shoes, walking velocity, and movement up a slope.

• Journal of the Korea Computer Graphics Society
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• v.26 no.3
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• pp.9-19
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• 2020

With the recent development of various kinds of virtual reality devices, there has been an active research effort to increase the sense of reality by recognizing the physical behavior of users rather than by classical user input methods. Among such devices, the Leap Motion controller recognizes the user's hand gestures and can realistically trace the user's hand in a virtual reality environment. However, manipulating an object in virtual reality using a recognized user's hand often causes the hand to pass through the object, which should not occur in the real world. This study presents a way to build a visual feedback system for enhancing the user's sense of interaction between hands and objects in virtual reality. In virtual reality, the user's hands are examined precisely by using a ray tracing method to see if the virtual object collides with the user's hand, and when any collision occurs, visual feedback is given through the process of reconstructing the user's hand by moving the position of the end of the user's fingers that enter the object through sign distance field and reverse mechanics. This enables realistic interaction in virtual reality in real time.

• Journal of Practical Engineering Education
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• v.14 no.3
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• pp.543-553
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• 2022

A collaborative robot(Cobot) is one of the production systems presented in the 4th industrial revolution and are systems that can maximize efficiency by combining the exquisite hand skills of workers and the ability of simple repetitive tasks of robots. Also, research on the development of an efficient interface method between the worker and the robot is continuously progressing along with the solution to the safety problem arising from the sharing of the workspace. In this study, a method for controlling the robot by recognizing the worker's hand signal was presented to enhance the convenience and concentration of the worker, and the safety of the worker was secured by introducing the concept of a safety zone. Various technologies such as robot control, PLC, image processing, machine learning, and ROS were used to implement this. In addition, the roles and interface methods of the proposed technologies were defined and presented for using educational media. Students can build and adjust the educational media system by linking the introduced various technologies. Therefore, there is an excellent advantage in recognizing the necessity of the technology required in the field and inducing in-depth learning about it. In addition, presenting a problem and then seeking a way to solve it on their own can lead to self-directed learning. Through this, students can learn key technologies of the 4th industrial revolution and improve their ability to solve various problems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3873-3879
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• 2010

Home service robot are not working in the fixed task such as industrial robot, because they are together with human in the same indoor space, but have to do in much more flexible and various environments. Most of them are developed on the base of the wheel-base mobile robot in the same method as a vehicle robot for factory automation. In these days, for holonomic system characteristics, omni-directional wheels are used in the mobile robot. A holonomicrobot, using omni-directional wheels, is capable of driving in any direction. But trajectory control for omni-directional mobile robot is not easy. Especially, azimuth control which sensor uncertainty problem is included is much more difficult. This paper develops trajectory controller of 3-wheels omni-directional mobile robot using fuzzy azimuth estimator. A trajectory controller for an omni-directional mobile robot, which each motor is controlled by an individual PID law to follow the speed command from inverse kinematics, needs a precise sensing data of its azimuth and exact estimation of reference azimuth value. It has imprecision and uncertainty inherent to perception sensors for azimuth. In this paper, they are solved by using fuzzy logic inference which can be used straightforward to perform the control of the mobile robot by means of the fuzzy behavior-based scheme already existent in literature. Finally, the good performance of the developed mobile robot is confirmed through live tests of path control task.