Joun-Ho Lee

Localization of a mobile robot using images of a moving target

In this paper, the localization of a mobile robot using images of a moving target is introduced. Typical objects are stored in the database for the localization of the mobile robot. With a fixed camera, a perspective camera model and a given object database, an image frame can provide the pose (distance and orientation) of the object with respect to the camera. Utilizing the consecutive image frames and motion estimation technology, the relative pose of the object with respect to the camera can be obtained accurately; and during the process, calibration of camera with respect to the world frame, i.e. localization of a mobile robot, is gradually performed. This localization scheme is demonstrated by the experiments.

Compensation for phase dispersion in horizontal-switching liquid crystal cell for improved viewing angle

In this paper we propose an optical configuration of a horizontal-switching liquid crystal (LC) cell with two positive C-plates and a single A-plate in order to improve the optical property in the diagonal direction, which is a weakness of horizontal-switching LC cells. The proposed configurations optical design was performed on a Poincare sphere with the trigonometric method. From calculations, we show that the proposed structure can increase the contrast ratio in the diagonal direction by about 10 times.

P‐92: Optical Configurations of TW‐IPS LC Cell for Very Wide Viewing Angle in Large Size TV Application

Two optical configurations of TW-IPS LC cell, which can provide wide viewing characteristics in diagonal direction by applying optimized compensation films, are proposed. Improvement of viewing angle characteristics has been analyzed on the Poin’care sphere and we calculated optical performance. To verify the calculation, we measured the viewing angle of the proposed TW-IPS cell experimentally and compared with a normal S-IPS cell. We applied the novel optical configurations to our 32-inch TFT-LCD for TV application.

Image-based visual servoing control of a SCARA type dual-arm robot

Visual servoing is the fusion of results from many elemental areas including high-speed image processing, kinematics, dynamics, control theory, and real-time computing. It has much in common with research into active vision and structure from motion, but is quite different from the often described use of vision in hierarchical task-level robot control systems. We present a new approach to visual feedback control using image-based visual servoing with the stereo vision in this paper. In order to control the position and orientation of a robot with respect to an object, a new technique is proposed using a binocular stereo vision. The stereo vision enables us to calculate an exact image Jacobian not only at around a desired location but also at the other locations. The suggested technique can guide a robot manipulator to the desired location without giving such priori knowledge as the relative distance to the desired location or the model of an object even if the initial positioning error is large. This paper describes a model of stereo vision and how to generate feedback commands. The performance of the proposed visual servoing system is illustrated by the simulation and experimental results and compared with the case of a conventional method for dual-arm robot made by Samsung Electronics Co. Ltd.

Optical configuration of a horizontal-switching liquid-crystal cell for improvement of the viewing angle

We propose an optical configuration of a horizontal-switching liquid-crystal cell, consisting of a splayed liquid-crystal cell and uniaxial films, to improve the viewing angle characteristics by compensating for the phase dispersion in a diagonal direction. The optical design of the proposed configuration was performed on a Poincaré sphere with geometric calculations. By fabricating in-plane switching cells with the introduced configuration, we demonstrated their optical performances. As a result, we found that the diagonal viewing angle of the proposed horizontal-switching cell could be increased by 80% compared to a symmetrical viewing cone.

Fine active calibration of camera position/orientation through pattern recognition

Precise information on an object, which is obtained through pattern recognition, is fused into an active calibration process. The calibration process can be classified into two modes, i.e., passive and active calibration. Passive calibration is possible by using images of calibration grids pre-located at a reference position with fixed size, while active calibration is performed using images of real objects, which are to be manipulated. In most active calibration processes, either based upon a line-correspondence scheme or upon a point-correspondence scheme, clear images of the object are required. Even with uncontaminated images, there exist errors in estimating the position and orientation of a camera due to lens distortion and limited number of pixels, as well as inherent errors due to the perspective model of a camera. These problems are being tackled in various ways since there is no simple and solid approach. In this paper, precise position and shape information of an object, which is obtained by a pattern recognition procedure, is integrated into the calibration process based upon a point-correspondence scheme to improve the accuracy in estimating the position/orientation of a camera. Experiments are performed to show the improvement in this accuracy.

Recycling of Coal Fly Ash for Fabrication of Porous Mullite Composite

Unidirectional pore structured porous mullite composite has been fabricated using a TBA-based freeze-gelcasting of coal fly ash/alumina slurries. After sintering at 1300-1500o C, the shrinkage, apparent porosity and compressive strength of the resulting porous composites were investigated. After sintering at 1500o C, the composite showed the maximum compressive strength of ~51 MPa and the minimum apparent porosity of ~64%.

Implementation of a new sliding mode control for SCARA robot

This paper addresses the implementation of a new sliding mode control algorithm for a high speed/precision controller which is robust against the variation of robot parameters and load. The nonlinear dynamics become prominent in high speed operation but can hardly be modeled accurately. Therefore, we consider the nonlinear inertia, Coriolis and centrifugal force terms as external disturbances. This approach is applied to sliding mode control to obtain switching control inputs. The control input obtained satisfy the existence condition of sliding mode. A dynamic simulator has been developed and used to evaluate the proposed algorithm for SCARA robots. Simulated results show that the proposed algorithm is robust against disturbances and reduces the amount of chattering. An experiment was performed to demonstrate the simulated results in a real system.

P-147: Novel Electrode Structure in the Super-IPS LC Cell for High-Aperture Ratio

In this paper, we propose a novel electrode structure, which exhibits high-aperture ratio, in the super in-plane switching (SIPS) liquid crystal (LC) cell for high transmittance. Generally, the transmittance of the S-IPS LC cell is not superior to other LC mode using the multi domain effect because of the low aperture ratio. To improve the aperture ratio of the S-IPS cell, we found the method to minimize the black matrix (BM) area by applying the novel electrode structure which can move the disclination from the active area. As a result, we found that the proposed electrode structure could provide higher aperture ratio than that of the conventional type by reducing the BM area, so that we could achieve the high transmittance compared to the conventional structure. We used the commercial software ‘TechWiz LCD’ for calculation of the director configuration, which applies Q-tensor method.

Static Configuration of the Super In-Plane Switching Liquid Crystal Director on the Electrode

In this work we investigate dynamic behavior of the LC director including the defect nucleation and the LC director field on the shape of the electrode using the Q-tensor method in the Super IPS cell. In general, the Q-tensor method can model the defect dynamics in a liquid crystal director field in addition to electrical behavior of the LC director.