• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.1
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• pp.1-7
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• 2003

When a ship is course-keeping in the open seas, autopilot system is adapted. The design of autopilot system is very important for improvement of ship′s element research. Automatic steering system consists of autopilot device, power unit, steering gear, magnetic or gyro compass and ship dynamics. In order to evaluate automatic steering system of ships in open seas. we need to know the characteristics of each component of the system, and also to know the characteristics of disturbance to ship dynamics. In this paper, I provide evaluation method of autopilot navigation system of the fishing ship. Prediction method based on the principle of linear superposition is introduced for irregular disturbance. For the evaluation of automatic steering system of a ship, "performance index" is introduced from the viewpoint of energy saving and calculation method is frequency response analysis. Finally, I carried out calculation of sensitivity of control constants of autopilot with various conditions of ocean environments.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1271-1279
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• 2017

A highly accurate model-free controller is proposed for trajectory tracking control of robot manipulators. The proposed controller incorporates time-delay estimation (TDE) to estimate and cancel continuous nonlinearities of robot dynamics, and exploits fuzzy logic systems to suppress the effect of the TDE error, which is due to discontinuous nonlinearities such as friction. To this end, integral sliding mode is defined using desired error dynamics, and a Mamdani-type fuzzy inference system is constructed. As a result, the proposed controller achieves the desired error dynamics well. Implementation of the proposed controller is easy because the design of the controller is intuitive and straightforward, and calculations of the complex robot dynamics are not required. The tracking performance of the proposed controller is verified experimentally using a 3-degree of freedom PUMA-type robot manipulator.

• Transactions on Control, Automation and Systems Engineering
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• v.2 no.3
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• pp.207-213
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• 2000

This paper introduces a high-performance speed control system based on artificial neural networks(ANN) to estimate unknown parameters of a DC servo motor. The goal of this research is to keep the rotor speed of the DC servo motor to follow an arbitrary selected trajectory. In detail, the aim is to obtain accurate trajectory control of the speed, specially when the motor and load parameters are unknown. By using an artificial neural network, we can acquire unknown nonlinear dynamics of the motor and the load. A trained neural network identifier combined with a reference model can be used to achieve the trajectory control. The performance of the identification and the control algorithm are evaluated through the simulation and experiment of nonlinear dynamics of the motor and the load using a typical DC servo motor model.

• Journal of Ocean Engineering and Technology
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• v.10 no.1
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• pp.108-118
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• 1996

This paper presents automatic reentry of a deepsea reser by adaptive control. Reentry is one of the major pro blems regarding a deepsea riser. In the reentry operation, the lower end of riser must be accurately positioned over the tarket point on the seabed. But the deepsea riser shows complex elastic response due to flexibility and nonlinearity of the riser dynamics and the required positioning accuracy is high. Moreover, elastic deformation must by controlled for securing structural integrity. In adaptive control, uncertainly known parameters like added mass and drag coefficient in the riser dynamics are identified and control forces at the floating body and the riser are calculated simultaneously. An Adaptive algorithm for MIMO linear discrete time system without requiring a persistent excitation is adopted in this study. The effectiveness of adaptive control logic is tested by numerical simulation and model experiment. The designed control system shows good overall performances, so that the present study can be applied to the control of the deepsea riser.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.64-71
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• 2011

In this study, steady and unsteady aerodynamic analyses of a huge rocket configuration have been conducted in a transonic flow region. The launch vehicle structural response are coupled with the transonic flow state transitions at the nose of the payload fairing. The developed fluid-structure coupled analysis system is applied for aeroelastic computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. It can give very accurate and useful engineering data on the structural dynamic design of advanced flight vehicles. For the nonlinear unsteady aerodynamics in high transonic flow region, Navier-Stokes equations using the structured grid system have been applied to the rocket configurations. Also, it is typically shown that the current computation approach can yield realistic and practical results for rocket design and test engineers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.175-180
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• 2002

Loading/Unloading(L/UL) mechanism has been considered to be an alternative to contact start-stop(CSS) mechanism which eliminates stiction and wear associated with frequent start and stop process. It has other advantages including increased areal density due to lower flying height, reduced power consumption, and improved shock resistance. In order for L/UL to be Implemented in Near-field recording system properly, dynamics of optical flying head must be understood and optimized. In this paper the dynamic characteristics during loading process is analyzed numerically to investigate the effect of design parameters such as loading speed. slider shape, and initia conditions on the dynamic reponses of flying head..

• The Pure and Applied Mathematics
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• v.16 no.1
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• pp.133-145
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• 2009

The purpose of this paper is to extend and globalize the Walrasian evolutionary cobweb model in an independent single local market of Brock and Hommes ([3]), to the case of the global market evolution over an infinite chain of many local markets interacting each other through a diffusion of prices between them. In the case of decreasing demands and increasing supplies with a weighted average of rational and naive predictors, we investigate, via the methods of Lattice Dynamical System, the spatial-temporal behaviors of global market dynamics and show that some kind of bounded dynamics of global market do exist and can be controlled by using the parameters in the model.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.69-71
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• 2015

In our previous work, we investigated the orbital dynamics of Asteroid 1934 CT (or 1989 AC or 4179 Toutatis) from epoch 2012-Jul-24 (JDE2456132.5) using the Mercury program package. Asteroid 4179 Toutatis has an Earth and Mars crossing orbit with semimajor axis a = 2.5292 AU and eccentricity e = 0.6294, and therefore the perihelion distance is q = 0.9373 AU and the aphelion distance is Q = 4.1211 AU. After more than 300,000 years, asteroid 4179 Toutatis will escape from the Solar System, but during this time, it will have close-encounters with other planets from Venus to Uranus. As a continuation of this project, we investigated its energy changes in each close encounter. We also determine the energy of this asteroid when it escapes from the Solar System. The result is that during its orbital evolution, the energy of this asteroid changes and gives us negative, zero and positive values.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.351-351
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• 2000

Since the heat exchange system, such as the boiler of power plant, gas turbine, and radiator require an application of intelligent control system for a high rate heat efficiency and the efficiency of these systems is depended on the control methods it is important for operator to understand control system of these systems and intelligent control technologies. In order to properly apply control equipment and intelligent technology to these process control systems, it is necessary to understand fuzzy, neural network, genetics, and immune as well as the basic aspects and operation principle of the process that relate control, interrelationships of the process characteristics, and the dynamics that are involved. Generally, since PID controllers are used in these systems it is difficult far engineer to understand both the complex dynamics and the intelligent control method. In this paper, we design an effective experimental system for the intelligent control education and analyze its characteristics through experimental system and each intelligent method to study how they can learn intelligent control system by experiments.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.3
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• pp.335-343
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• 2014

An airbag is an important safety system and is well known as a safety system in cars during an accident. Airbag systems are also used as a shock absorber for UAVs to assist with rapid parachute landings. In this paper, the dynamics and gas dynamics of five airbag shapes, cylindrical, semi-cylindrical, cubic, and two truncated pyramids, were modelled and simulated under conditions of impact acceleration lower than $4m/s^2$ to avoid damage to the UAV. First, the responses of the present modelling were compared and validated against airbag test results under the same conditions. Second, for each airbag shape under the same conditions, the responses in terms of pressure, acceleration, and emerging velocity were investigated. Third, the performance of a pressure relief valve is compared with a fixed-area orifice implemented in the air bag. For each airbag shape under the same conditions, the optimum area of the fixed orifice was determined. By examining the response of pressure and acceleration of the airbag, the optimum shape of the airbag and the venting system is suggested.