Hyun-Chan Cho

Constant Altitude Flight Control for Quadrotor UAVs with Dynamic Feedforward Compensation

This study addresses the control problem of an unmanned aerial vehicle (UAV) during the transition period when the flying mode changes from hovering to translational motion in the horizontal plane. First, we introduce a compensation algorithm that improves height stabilization and reduces altitude drop. The main principle is to incorporate pitch and roll measurements into the feedforward term of the altitude controller to provide a larger thrust force. To further improve altitude control, we propose the fuzzy logic controller that improves system behavior. Simulation results presented in the paper highlight the effectiveness of the proposed controllers.

Telerobotic system for cell manipulation

In this paper, telerobotic system for cell injection applications is proposed. Fidelity and stability are contradicting factors in teleoperation. Most of cells manipulations nowadays are performed manually by the human operators. These highly precise operations require high-skilled professional operators. However, the success and survival rate of the cells is very low due to the great sensitivity of cells. Moreover, while manipulating, operator cannot feel any interaction with the cells because of their negligible mass, therefore all the operations are based on the visual information provided by the high-precision microscope. In addition, during every operation the humanpsilas hand has a certain vibration that can affect the quality of teleoperation, especially in telesurgery, nanomanipuation and other precise tasks. All of the reasons listed above show that the cells manipulation is an exclusively complex task for a human operator to perform. Therefore, applying telerobotic system for the cells manipulation may provide us with many advantages and could help us to overcome the problems listed above.

Tracking a moving ground object using quadcopter UAV in a presence of noise

This paper addresses visual servoing control of quadrotor unmanned aerial vehicles (UAVs) during tracking of a moving ground object. The proposed system uses single monocular camera as an input for feedback control system of quadcopter. The main objectives of the developed control system was to compensate for the noise introduced by the visual sensor and to reduce errors in object tracking by means of filtering. The proposed control strategy was verified through extensive computer simulations for different cases of object motion trajectories and velocities. The developed control system helped to reduce average object tracking error by up to 60%.

Human-Friendly Intelligent Hue Control System for Display Unit

Human`s sight holds the most extents for recognizing information among other senses. If we make much better visualized environment for human, it will become more beneficial in person`s emotion or body. Human is using a lot of display units in modern society. Basic hues ate Red, Green and Blue. Using these three colors, we can change hue sense and degree of brightness of display unit. If we control hue of unit to be suitable according to individual environment, we can feel comfortable or reduce stress. In this paper, we present Human-Friendly Intelligent Hue Control System(HFIHCS) that control hue of display unit using fuzzified factors related to human`s emotion and environment. The effectiveness of the proposed system is demonstrated by questionnaire.

Improved automatic gain control circuit using fuzzy logic

A problem that arises in most communication receivers concerns the wide variation in power level of the signals received at the antenna. These variations cause serious problems which are usually be solved in receiver design by using Automatic Gain Control (AGC). AGC is achieved by using an amplifier whose gain can be controlled by using external current or voltage. We have to note that the AGC circuit does not respond to rapid changes in the amplitude of input and multifrequency. Nowadays, with the development of the fuzzy theory, the advantages of the fuzzy logic are recognized widely and deeply. Applying fuzzy logic to AGC circuit is a way to enhance AGC circuit.

System of Agricultural Land Monitoring Using UAV

The purpose of this study is to develop a system configuration for gathering data and building a database for agriculture. Some foreign agriculture-related companies have already constructed such a database for scientific agriculture. The hardware of this system is composed of automatic capturing equipment based on aerial photography using a UAV. The software is composed of parts for stitching images, matching GPS data with captured images, and building a database of collected weather information, farm operation data, and aerial images. We suggest a method for building the database, which can include information about the amount of agricultural products, weather, farm operation, and agricultural land images. The images of this system are about 5 times better than satellite images. Factors such as farm working and environmental factors can be basic data for analyzing the full impact of agriculture land. This system is expected to contribute to the scientific analysis of Koreas agriculture.

Adaptive control over quadcopter UAV under disturbances

This paper is concerned with adaptive compensation for position tracking error of quadrotor UAVs. We propose an adaptive compensation scheme which effectively reduces errors in tracking desired position along X- and Y-axis in the presence of constant disturbance. The proposed control strategy is verified through extensive computer simulations. Implementation of the designed adaptive compensator allowed to reduce tracking error by a factor of 3 and can be effectively used in practical quadcopters.

Optimal initial structure of the RBF networks using time-frequency localization and genetic algorithm

In this paper, we propose the initial optimized structure of radial basis function networks that is simple and rapidly converges. We construct the hidden node with radial basis functions; their localization is similar to an approximation target function in the plane of time and frequency. We finally make a good decision for the initial structure for function approximation using a genetic algorithm.

TEMPERATURE INFERENCE SYSTEM BY ROUGH-NEURO-FUZZY NETWORK

Rough set theory, suggested by Pawlak in 1982, has been useful in AI, machine learning, knowledge acquisition, knowledge discovery from databases, expert systems, inductive reasoning, etc. One of the main advantages of rough sets is that they do not need any preliminary or additional information about data and are capable to reduce superfluous information. However, their significant disadvantage in real applications is that inferences are not real values but disjoint intervals of real values. In order to overcome this difficulty, we propose a new approach in which rough set theory and neuro-fuzzy fusion are combined to obtain the optimal rule base from input/output data. These results are applied to the rule construction for inferring the temperature at specified points in a refrigerator.

A Study on Developing Intelligent Control System for Charging/Discharging Lithium Secondary Battery Cells With Numerical Impedence Predictions

The Lithium secondary battery system needs very high capacity with high effectiveness because the industrial applications have been increased to include a hybrid car, airplanes, and the other aerospace fields, etc. Battery control system will switch off the charging current if one cell has reached full charge for stabilization; this happens due to serial connection and old status of battery cells in order to prevent being over charged and to increase the efficiency of them by keeping the rest of cells from being fully charged. It is a quite important to estimate impedance for state of charge in characteristics of battery cells to set the time to charge the each cell of the battery pack. This paper suggests the method of predicting battery impedance because of aging effects by using numerical simulations, which are verified with the experimental laboratory works. This paper also develops an Intelligent fuzzy control algorithm to maximize the efficiency of the battery cells by keeping the time to charge or discharge each cell of battery pack be more uniform.Copyright