• Journal of Institute of Control, Robotics and Systems
• /
• v.19 no.9
• /
• pp.846-852
• /
• 2013

In this paper, the authors propose a new approach to control problem of the marine vessels which are moored or controlled by actuators. The vessel control problem in the specified area is called a DPS (Dynamic Positioning System). The main objective of this paper is to obtain more useful control design method for DPS. In this problem, a complicate fact is control allocation which is a numerical method for distributing the control signal to the controlled system. For this, many results have been given and verified by other researchers using two individual processes. It means that the controller design and control allocation design process are carried out individually. In this paper, the authors give more sophisticated design solution on this issue. In which the controller design and control allocation problem are unified by a robust controller design problem. In other word, the stability of the closed-loop system, control performance and allocation problem are unified by an LMI (Linear Matrix Inequality) constraint based on $H_2/H_{\infty}$ mixed design framework. The usefulness of proposed approach is verified by simulation with a supply vessel model and found works well.

• Journal of Ocean Engineering and Technology
• /
• v.26 no.3
• /
• pp.20-25
• /
• 2012

In this paper, the authors propose a new approach to the control problem of marine vessels that are moored or controlled by actuators. The vessel control system is basically based on Dynamic Positioning System (DPS) technology. The main object of this paper is to obtain a more useful control design method for DPS. In this problem, the control allocation is a complication. For this problem, many results have been given and verified by other researchers using a two-step process, 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 method in which the controller design and control allocation problems are considered and solved simultaneously. In other words, the system stability, control performance, and allocation problem are unified by an LMI (linear matrix inequality) based on control theory. The usefulness of the proposed approach is verified by a simulation using a supply vessel model.

• Journal of Navigation and Port Research
• /
• v.47 no.4
• /
• pp.256-270
• /
• 2023

In this study, a sliding mode (SM) controller for dynamic positioning (DP) was specifically designed for a turret connection operation of a ship or an offshore structure in which an arbitrary point on the structure could be controlled as the motion center instead of the center of mass. The SM controller allows control of the arbitrary point and provides capability to manage uncertainties in the dynamics of ships and offshore structures, external forces caused by unknown changing marine environments, and transient performance of DP systems. The Jacobian matrix included in kinematic equations of the controlled object was modified to design the SM controller to control based on an arbitrary point of ships or offshore structures. To ensure robustness of the controller, the Lyapunov stability theory was applied in the design of the SM controller. In general, for robustness in DP control, gain scheduling based on a proportional-derivative (PD) control algorithm is employed. However, finding appropriate gains for gain scheduling complicates the application of DP systems. Therefore, in this study, the SM control algorithm was considered to mitigate the complexity of the DP controller for ships and offshore structures. To validate the proposed SM control algorithm, time-domain simulations were conducted and utilized to evaluate the performance of the control algorithm. The effectiveness of the proposed SM controller was assessed by comparing simulation results with results of a conventional PD control algorithm applied in DP control.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.2 s.191
• /
• pp.86-94
• /
• 2007

In this paper, a dual stage servo mechanism has been developed for image tracking system to improve control performances such as small rise time, small overshoot, small settling time, small stabilization error etc. A secondary stage, a platform, actuated by a pair of electro-magnets is mounted on a conventional elevation gimbal. In this mechanism, the gimbal provides large range but slow motion and the platform provides small range but fast positioning. A sliding mode control is applied to the platform positioning to attain robust performances and stability in the presence of the disturbance related to dynamic coupling of the gimbal and the platform. Results from experiments illustrate that the suggested dual stage mechanism controlled by the sliding mode control is effective in improving responses and attenuating the disturbance response related with dynamic coupling.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.8 s.227
• /
• pp.1093-1098
• /
• 2004

This paper presents a close-loop feedback control scheme, which can simultaneously satisfy multiple conflicting control performances, for a high speed positioning system driven by a brushless D.C. motor. With the dynamic model of the motor and proportional-plus-derivative feedback controllers selected as sample controllers, the convex combined feedback controller is formulated for implementing a direct-drive manipulator. Experimental results show that the developed multiple simultaneous specification(MSS) controller can meet desired control performances; maximum overshoot and rise time.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.3
• /
• pp.394-401
• /
• 2010

In this article, we investigate a robust friction compensation scheme for the purpose of accomplishing precision positioning performance a servo mechanical system with nonlinear dynamic friction. To estimate the friction state and tackle robustness problem for uncertainty, a RFNN and reconstructed error compensator as well as a robust friction state observer are developed. The asymptotic stability of the series of friction compensation methodologies are verified from the Lyapunov's stability theory. Some simulations and experiments on a servo mechanical system were carried out to evaluate the effectiveness of the proposed control scheme.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.50 no.9
• /
• pp.417-422
• /
• 2001

The brushless DC motor(BLDCM) is widely used in many applications. One of the application of the BLDCM is the stage which is one of process in the semiconductor manufacturing processes. Very high performance is required in the stage process. In this paper, the 1 degree of freedom positioning system for the basic technology of the stage is studied. The linearization method is proposed to make the controller design procedures easy by measuring the thrust force ripple using the strain gauge. And through the experiments, it is proved that the inner velocity control loop is necessary to make more precise positioning control system.

• Proceedings of the KIEE Conference
• /
• 2004.05a
• /
• pp.33-37
• /
• 2004

To meet an increasing demand for high performance in gun dynamic plant, both a precise and a fast response positioning are strongly required for the gun servomechanism control. A mode switching control(MSC) system, which includes a fine stabilizing controller, fast positioning one and a switching function, is widely used to meet this requirement. Stabilization is performed through PID controller, while proximate time optimal servo(PTOS) is used for target designation. Because gun dynamic have large damping comparing to acceleration, PTOS algorithm with damping is newly derived. This paper adopts the initial value compensation method that improve the transient response after switching. Some simulation results are given to show the effectiveness of our scheme.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2004.04a
• /
• pp.103-106
• /
• 2004

Nowadays it is necessary to manage the road system effectively because of the explosive increment of vehicle and goods. To resolve this problems through the fast upgrade of information about position and time of moving vehicle, the combined navigation system using GPS and complementary navigation system, i.e. INS, DR, etc. has been used. Although GPS is popular for the vehicle navigation system, this is not useful for the kinematic positioning of the vehicles in the urban canyon because of its few satellites. Therefore, this study deals with the kinematic positioning of the vehicles with GPS CORS to GPS navigation. For this, first the static single point positioning of GPS and GPS for reference station was performed to evaluate the accuracy of GPS positioning. Next, in the post-processed, the DGPS (Differential GPS) was performed for the kinematic positioning of the vehicles. So, it is expected that GPS CORS can be applicable to the control of traffic flow, the effective management of road system, and the development of ITS and it is regarded that the combined navigation system of vehicles with GPS, INS, and DR, etc. should be studied constantly.

• Journal of Positioning, Navigation, and Timing
• /
• v.1 no.1
• /
• pp.7-14
• /
• 2012

Due to inaccurate safe navigation estimates, maritime accidents have been occurring consistently. In order to solve this, the precise positioning technology using carrier phase information is used, but due to high buildings near inland waterways or inclination, satellite signals might become weak or blocked for some time. Under this weak signal environment for some time, the GPS raw measurements become less accurate so that it is difficult to search and maintain the integer ambiguity of carrier phase. In this paper, a method to generate code and carrier phase measurements under this environment and maintain resilient navigation is proposed. In the weak signal environment, the position of the receiver is estimated using an inertial sensor, and with this information, the distance between the satellite and the receiver is calculated to generate code measurements using IGS product and model. And, the carrier phase measurements are generated based on the statistics for generating fractional phase. In order to verify the performance of the proposed method, the proposed method was compared for a fixed blocked time. It was confirmed that in case of a weak or blocked satellite signals for 1 to 5 minutes, the proposed method showed more improved results than the inertial navigation only, maintaining stable positioning accuracy within 1 m.