• The Journal of Korea Robotics Society
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• v.11 no.4
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• pp.217-225
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• 2016

Dynamic Positioning (DP) is used to automatically maintain the position and heading of a floating structure subjected to environmental disturbances. A DP control system is composed of a motion controller to compute the desired force and moment and a thrust allocator to distribute the computed force and moment to multiple thrusters considering mechanical and operational constraints. Among various thruster configurations, azimuth thrusters or propeller/rudder pairs tend to make the allocation problem difficult to solve, because these types of propulsion systems include nonlinear constraints. In this paper, a dynamic positioning strategy for a twin-thruster ship that is propelled by two azimuthing thrusters is addressed, and a thrust allocation method which does not require a numerical optimization solver is proposed. The applicability of the proposed method is demonstrated with an experiment using an autonomous boat.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.571-576
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• 2007

This study presents stiffness-based optimal design to control quantitatively lateral drift of frame-shear wall structures subject to seismic loads. To this end, lateral drift constraints are established by introducing approximation concept that preserves the generality of the mathematical programming and can efficiently solve large scale problems. Also, the relationships of sectional properties are established to reduce the number of design variables and resizing technique of member is developed under the 'constant-shape' assumption. Specifically, the methodology of dynamic displacement sensitivity analysis is developed to formulate the approximated lateral displacement constraints. The 12 story frame-shear wall structural models is considered to illustrate the features of dynamic stiffness-based optimal design technique proposed in this study.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.1
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• pp.31-37
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• 2003

A robust tracking control for nonholonomic dynamic systems is proposed in this paper. Since nonholonomic dynamic systems have constraints imposed on motions that are not integrable, i.e., the constraints cannot be written as time derivatives of some functions of generalized coordinates, advanced techniques are needed for their control. It is shown that if the state of nonholonomic systems is mapped into a bounded space by a coordinate transformation, a robust controller for dynamic models of nonholonomic systems with input disturbances can be designed using sliding mode control. Stability and robustness of the proposed controller are proved in the Lyapunov sense. Numerical simulations on the trajectory tracking of a two-wheeled mobile robot are conducted to validate the effectiveness of the proposed controller.

• Structural Engineering and Mechanics
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• v.54 no.3
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• pp.453-474
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• 2015

A hybrid approach of Particle Swarm Optimization (PSO) and Swallow Swarm Optimization algorithm (SSO) namely Hybrid Particle Swallow Swarm Optimization algorithm (HPSSO), is presented as a new variant of PSO algorithm for the highly nonlinear dynamic truss shape and size optimization with multiple natural frequency constraints. Experimentally validation of HPSSO on four benchmark trusses results in high performance in comparison to PSO variants and to those of different optimization techniques. The simulation results clearly show a good balance between global and local exploration abilities and consequently results in good optimum solution.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.574-582
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• 1999

This paper discusses the multi-level optimization method in dynamic optimization problems through stiffened plate of ship structures. In structural optimization the computational cost increases rapidly as the number of design variables increases. And we need a great amount of cal-culation and time on problems of modified dynamic characteristics of large and complicated struc-tures. In this paper the multi-level optimization is proposed which decreases computational time and cost. the dynamic optimum designs of stiffened plate that control the natural frequency and minimize weight subjected to constraints condition are derived. The way to apply the multi-level optimization methods in this study follow: In the first step the dynamic characteristics is controlled for the two-dimensional model of stiffened plate by sensitivity analysis and quasi-least squares methods. In the second step the cross-section of the stiffener is decided so that the weight is minimized under needed constraints by the steepest descent or ascent method. In the third the three-dimensional model is made based on the results of the first step and the second step confirmation and finer tuning of the objective function are carried out. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.899-909
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• 1992

An iterative solution technique is presented to analyze the dynamic systems of rigid bodies subjected to kinematic constraints. Lagrange multipliers associated with the constraints are iteratively computed by monotonically reducing an appropriately defined constraint error vector, and the resulting equation of motion is solved by a well-established ODE technique. Constraints on the velocity and acceleration as well as the position are made to be satisfied at joints at each time step. Time integration is efficiently performed because decomposition or orthonormalization of the large matrix is not required at all. An acceleration technique is suggested for the faster convergence of the iterative scheme.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1940-1949
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• 2015

This paper presents an Enhanced Particle Swarm Optimization (EPSO) to solve short-term hydrothermal scheduling (STHS) problem with non-convex fuel cost function and a variety of operational constraints related to hydro and thermal units. The operators of the conventional PSO are dynamically controlled using exponential functions for better exploration and exploitation of the search space. The overall methodology efficiently regulates the velocity of particles during their flight and results in substantial improvement in the conventional PSO. The effectiveness of the proposed method has been tested for STHS of two standard test generating systems while considering several operational constraints like system power balance constraints, power generation limit constraints, reservoir storage volume limit constraints, water discharge rate limit constraints, water dynamic balance constraints, initial and end reservoir storage volume limit constraints, valve-point loading effect, etc. The application results show that the proposed EPSO method is capable to solve the hard combinatorial constraint optimization problems very efficiently.

• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.1891-1899
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• 2004

The characteristics of dynamic systems subjected to multiple linear constraints are determined by considering the constrained effects. Although there have been many researches to investigate the dynamic characteristics of constrained systems, most of them depend on numerical analysis like Lagrange multipliers method. In 1992, Udwadia and Kalaba presented an explicit form to describe the motion for constrained discrete systems. Starting from the method, this study determines the dynamic characteristics of the systems to have positive semidefinite mass matrix and the continuous systems. And this study presents a closed form to calculate frequency response matrix for constrained systems subjected to harmonic forces. The proposed methods that do not depend on any numerical schemes take more generalized forms than other research results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1674-1684
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• 1994

An efficient iterative method is presented for the dynamic analysis of bodies moving on flexible structures. In contrast to traditional approaches, the nominal motion of the body is considered here as an unknown. The correct contact forces between the bodies and the flexible structures are computed by an iterative method reducing the specially defined error vectors to zero, and thus satisfying the constraints between the bodies and the structures. Even thought only simple equations of motions and simple time integrators are adopted, the correct solutions are economically obtained and the Timoshenko paradox is completely resolved. Numerical simulations are conducted demonstrate the accuracy and reliability of the solution and to compare the results with the reference.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.25-32
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• 2004

This paper presents a new optimization technique of acceleration curve for dynamic structure's movement in which high speed and low vibration are desirable. This technique is based on a genetic algerian with a penalty function for acceleration optimization under the assumption that an initial profile of acceleration curves constitutes the first generation of the genetic algorithm. Especially the penalty function consists of the violation of constraints and the number of violated constraints. The optimized acceleration of the crane through the genetic algorithm and commercial dynamic analysis software has shown to have accurate movement and low vibration compared to the conventional accelerations with jerk discontinuity.