• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.57-64
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• 2007

There have been many researches for optimal controllers in multivariable systems, and they generally use accurate linear models of the plant dynamics. Real systems, however, contain nonlinearities and high-order dynamics that may be difficult to model using conventional techniques. Therefore, it is necessary a PID gain tuning method without explicit modeling for the multivariable plant dynamics. The PID tuning method utilizes the sign of Jacobian and gradient descent techniques to iteratively reduce the error-related objective function. This paper, especially, focuses on the role of I-controller when there is a steady state error. However, it is not easy to tune I-gain unlike P- and D-gain because I-controller is mainly operated in the steady state. Simulations for an overhead crane system with dynamic friction show that the proposed PID-LC algorithm improves controller performance, even in the steady state error.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.47-50
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• 2002

선반건조 일정계획에 있어서 탑재 공정은 전체 생산일정 계획 중 선박 한 척에 대한 계획의 시발점이 되며, 병목현상 등을 유발하여 다른 일정에 가장 큰 영향을 주게 되는 공정이다. 최근 많은 조선소에서 하나의 Dock 내에서 두 착 이상의 배를 동시에 건조하는 tandem 방식을 택하고 있어 dock 내의 한정된 Crane 의 개수와 Crane의 Capacity, 공수 등의 자원, 그리고 작업환경에서 일어날 수 있는 여러 가지 변수들을 제대로 고려하지 못 했을 시에는 일정의 차질과 Dock의 회전율을 떨어트리게 한다. 본 논문에서는 가상공간에 하나의 Dock 를 만들어서 일정계획에서 작성한 Network를 사용하여 실제 작업하게 해서 그 Network가 현장에서의 최적한가를 점검하게 하고 현장에서 수정하는 작업을 줄이게 하는 것의 방법으로 simulation을 개발하였다.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.6 no.1
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• pp.30-37
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• 2003

This paper describes vibration control of a suspended system using wave absorption method. A moving multiple-pendulum system and a moving wire-and-load system are treated. The wire-and-load system is extended to a model crane system that has a motor system to roll up and down the suspended mass like a real crane. The same program with different parameter values controls these three systems. Both numerical simulation and experiment have been conducted, and the present control method has shown to be quite effective.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.84-91
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• 2006

The synthesis of optimal controllers for multivariable systems usually requires an accurate linear model of the plant dynamics. Real systems, however, contain nonlinearities and high-order dynamics that may be difficult to model using conventional techniques. This paper presents a novel loaming method for the synthesis of LQR controllers that doesn't require explicit modeling of the plant dynamics. This method utilizes the sign of Jacobian and gradient descent techniques to iteratively reduce the LQR objective function. It becomes easier and more convenient because it is relatively very easy to get the sign of Jacobian instead of its Jacobian. Simulations involving an overhead crane and a hydrofoil catamaran show that the proposed LQR-LC algorithm improves controller performance, even when the Jacobian information is estimated from input-output data.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.45.2-45
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• 2001

In case that the perfect model following conditions are not satisfied in the system, a perfect model-following controller is difficult to apply to the system. To deal with this problem, in this paper, a robust imperfect stable model-following controller is designed by combining time delay controller and sliding mode controller based on the concept of two degrees of freedom(2-DOF) controller design method. The experimental dynamic modeling of the commercial overhead crane with capacity of two tons is carried out. To remove the noise of the measuring signals from the swing angle measurement device and estimate the state of the swing angles of the transported object at each time instant, realtime tracker is designed using Kalman filter. The performance of the designed robust controller is tested through the commercial overhead. The experimental results show that the designed controller is robust and applicable to real systems.

• Coupled systems mechanics
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• v.7 no.4
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• pp.485-507
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• 2018

The moving load causes the occurrence of vibrations in civil engineering structures such as bridges, railway lines, bridge cranes and others. A novel engineering method for separation of the variables in the differential equation of the elastic line of Bernoulli-Euler beam has been developed. The method can be utilized in engineering structures, leading to "a beam under moving load model" with generalized boundary conditions. This method has been implemented for analytical study of the dynamic response of the metal structure of a single girder bridge crane due to the telpher movement along the bridge girder. The modeled system includes: a crane bridge girder; a telpher, moving with a constant horizontal velocity; a load, elastically fixed to the telpher. The forced vibrations with their own frequencies and with a forced frequency, due to the telpher movement, have been analyzed. The loading resulting from the telpher uniform movement along the bridge girder is cyclical, which is a prerequisite for nucleation and propagation of fatigue cracks. The concept of "dynamic coefficient" has been introduced, which is defined as a ratio of the dynamic deflection of the bridge girder due to forced vibrations, to the static one. This ratio has been compared with the known from the literature empirical dynamic coefficient, which is due to the telpher track unevenness. The introduced dynamic coefficient shows larger values and has to be taken into account for engineering calculations of the bridge crane metal structure. In order to verify the degree of approximation, the obtained results have been compared with FEM outcomes. An additional comparison has been made with the exact solution, proposed by Timoshenko, for the case of simply supported beam subjected to a moving force. The comparisons show a good agreement.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.4
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• pp.238-247
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• 2018

This paper considers the problem of scheduling loading and unloading operations of a crane in a railway terminal motivated from rail-road container transshipment operations at Uiwang Inland Container Depot (ICD). Unlike previous studies only considering the total handling time of containers, this paper considers a bi-criteria objective of minimizing the weighted sum of the total handling time and tenant service time. The tenant service time is an important criterion in terms of terminal tenants who are private logistics companies in charge of moving containers from/to the terminal using their trucks. In the rail-road container shipment yard, the tenant service time of a tenant can be defined by a time difference between beginning and finishing loading and unloading operations of a crane. Thus, finding a set of sequences and time of the crane operations becomes a crucial decision issue in the problem. The problem is formulated as a nonlinear program which is improved by linearizing a nonlinear constraint in the model. This paper develops a genetic algorithm to solve the problem and performs a case study on the Uiwang ICD terminal. Computational experiment results show that the genetic algorithm shows better performance than commercial optimization solvers. Operational implications in terms of tenants are drawn through sensitivity analyses.

• Journal of Korean Society of Forest Science
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• v.82 no.2
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• pp.195-206
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• 1993

The purpose of this study is to provide a basis for establishing regional harvesting systems that ist the prerequisites for the forest mechanization. The factors restricting to the forest harvesting and logging methods from topographical aspects are studied for this purpose. Three main harvesting methods studied in this paper are : shortwood method, longwood method and full tree method. This study shows : the shortwood method is suitable for low, the longwood method for medium, the full tree method for high topographical conditions. For the logging methods, the focus of the study is on various ground based logging systems by animalpower, manpower, gravitation, wheeled & crawler vehicle and cable. The factors limiting the coverage of logging operation are slope and logging distance. The cable crane logging methods are classified by logging distance into short distance(to 300 or 400m), middle distance(to 700 or 800m) and long distance cable crane methods (over 700 or 800m). The wheeled vehicle method shows serious damages to forest resources, whereas the logging by log-line of the gravitation logging method and cable crane method tend to minimize such damages. The wheeled & crawler vehicle method also shows difficult to apply in the high slope conditions, whereas cable crane method can be applied to maximum 120% steep slope and uphill conditions.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1754-1757
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• 2004

For the anti-sway control of traveling cranes, there are several solutions, i.e., by fuzzy control, by optimal control theory, etc. Each of them is reported to be effective. And, H infinity control and $H_2$ control can be also used. However, the full order observer which estimates all states in the controlled object is used in these methods. Therefore, the orders of these controllers are apt to be higher than that of the optimal controller, etc. Because the conventional H2 controller which minimizes $H_2$ norm consists of two parts, that is: feedback gains which make the controlled object stable and the full order observer which estimate those states. If the minimal order observer is used instead of the full order one, the order of the controller can be reduced. In this paper, we propose a new method based on the minimalization of $H_2$ norm using the minimal order observer. And, we confirm the effect of a new $H_2$ controller in the experiments of the anti-sway control of a traveling crane.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.813-817
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• 2003

By increasing trades between countries, importance of harbors is becoming serious, including our country. When it comes to Container Crane Operation, the most important matter is how many containers are loaded in a truck or a ship by given time. This can be a crucial matter of harbors in taking care of materials. The present harbors' crane uses a wire-rope conveyance materials are transported in the air and have high free-angle of location. The sway can cause the delay of time, wrong position of Trolley and the damage of materials. In this study, we obtain the optimal PID parameters with GA(Genetic Algorithm) and apply those parameters to the PID Controller. In the result of the experimentation, we can see how effectively the PID controller, applied with the optimal parameters obtained by GA, can control the sway angle.