Sang-Won Ji

A Study on Position Mooring System Design for the Vessel Moored by Mooring Lines

This paper presents the experimental results about position mooring (PM) system applied to the barge ship. The aim of the PM is to maintain the position and motion of the ships surge and sway directions as desired. In this paper, a system consisting of a barge vessel and mooring lines is mathematically modeled. The position and orientation of the vessel is controlled by changing the tensions of the mooring lines with the subwinch. A comparison of the newly designed mathematical model with the existing PID control method and the results of experiments indicated that the proposed designing method is more efficient than the traditional method.

Study on the Measurement Method of Leakage Flow-rate for Pneumatic Driving Apparatus

In this study, a measurement method of leakage flow-rate for pneumatic driving apparatus is proposed. The existing measurement methods of leakage flow-rate of air need disassemble the test component. Therefore, there was no effective method to measure the leakage flow-rate while operating pneumatic driving apparatus. In this study, the leakage flow-rate is measured by the pressure change in an isothermal chamber that can realize isothermal conditions by stuffing steel wool into it. Therefore, wide range of flow-rate could be measured only from the pressure response and the leakage flow-rate can be measured during operating pneumatic apparatus. The effectiveness of the proposed method is proved by experimental results

Experimental approach for mooring winch control system design

In the barge ship, the mooring winch system with the cable is used to keep its position in the specified area. In this paper, we consider a single type mooring winch system and control system design problem. For this, we separate the controlled system as two parts except the vessel. The one is the winch drum part without cable and the other is the cable part. Where it is considered that the winch dynamics are known, because it can be easily calculated. However the cable dynamics are too complicate and difficult to obtain them directly such that it is considered as uncertainty. Using known winch dynamics, a cable model which is unknown in general can be easily extracted from experiment data in which the characteristics of cable and winch motion are mixed. Based on these results, we design a robust control system, and control performance is evaluated by simulation.

Control Allocation and Controller Design for Marine Vessel based on H ∞ Control Approach

*Department of Mechanical System Engineering, College of Engine ering, Pukyoung National University, Busan, KoreaKEY WORDS: Dynamic positioning system DPS, Marine vessel 선박, Control allocation 제어력분배, Robust control 강인제어, Stability 안정성, Control performance 제어성능, Linear Matrix Inequality(LMI) 선형행렬부등식 ABSTRACT: In this paper, the authors propose a new approach to the contro l problem of marine vessels that are moored or controlled by actuators. The vessel control system is basically based on Dyna mic Positioning System (DPS) technology. The main object of this paper is to obtain a more useful control design method for DPS. In this problem, t he control allocation is a complication. For this problem, many results have been given and verified by other researchers using a two-step proces s, with the controller and control allocation design processes carried out individually. In this paper, the authors provide a more sophisticated design solution for this issue. The authors propose a new design metho d in which the controller design and control allocation problems are considere d and solved simultaneously. In other words, the system stabili ty, control performance,and allocation problem are unified by an LMI (linea r matrix inequality) based on control theory. The usefulness of the proposed approach is verified by a simulation using a supply vessel mode l.교신저자 김영복: 부산광역시 남구 신선로 365, 051-629-6197, kpjiwoo@pknu.ac.kr

A control allocation sterategy based on multi-parametric quadratic programming algorithm

Control allocation is an important part of a system. It implements the function that map the desired command forces from the controller into the commands of the different actuators. In this paper, the authors present an approach for solving constrained control allocation problem in vessel system by using multi-parametric quadratic programming (mp-QP) algorithm. The goal of mp-QP algorithm applied in this study is to compute a solution to minimize a quadratic performance index subject to linear equality and inequality constraints. The solution can be pre-computed off-line in the explicit form of a piecewise linear (PWL) function of the generalized forces and constrains. The efficiency of mp-QP approach is evaluated through a dynamic positioning simulation for a vessel by using four tugboats with constraints about limited pushing forces and found to work well.

A NEW CONTROL ALLOCATION DESIGN FOR MARINE VESSEL BASED ON ROBUST CONTROL

In this study, we propose a new approach to control design problem for the marine vessels which are moored or controlled by several actuators. In sometime and special purposes, the vessels are to be positioned by actuators which are installed on them or assisted by extra systems. We can see that there are many types of actuator in the real applications. Among them, the useful and widely applicable systems are thruster and mooring winch. In the case of applying these systems to the actual plants, a complicate fact is the control allocation problem. To make a good solution on this problem, many results have been given and verified by many researchers with a two step process. Exactly it means that controller design and control allocation process are carried out individually. In the result, the stability and performance of the control system are not considered, such that the basic objectives of control system design are not guaranteed any more. In this paper, the author gives a sophisticated solution for this issue. The authors show a new design method in which the controller design and control allocation problem can be converted by one step problem. In other word, the authors show that the system stability, control performance and allocation problem are unified by a condition obtained from H  control theory.