• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.2
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• pp.63-77
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• 1990

The combined deckstructure-car system of a car carrier is especially sensitive to hull girder vibrations due to mechanical excitations and wave loads. For the free and forced vibration analysis of the system, the analytical methods based on the receptance method and two schemes for efficient applications of the methods are presented. The methods are especially relevant to dynamical reanalysis of the system subject to design modification or to dynamic optimization. The deck-car system is modelled as a combined system consisting of a stiffened plate representing deck, primary structure, and attached subsystems such as pillars, additional stiffeners and damped spring-mass systems representing cars/trucks. For response calculations of the system subjected to displacement excitations along the boundaries, the support displacement transfer ratio conceptually similar to the receptance is introduced. For the verification of accuracy and calculation efficiency of the proposed methods, numerical and experimental investigations are carried out.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.2
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• pp.671-686
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• 2020

Due to the long training time and high training cost of traditional surgical training methods, the emerging virtual surgical training method has gradually replaced it as the mainstream. However, the virtual surgical system suffers from poor authenticity and high computational cost problems. For overcoming the deficiency of these problems, we propose an optimized model for the local compression deformation of soft tissue. This model uses a simulated annealing algorithm to optimize the parameters of the soft tissue model to improve the authenticity of the simulation. Meanwhile, although the soft tissue deformation is divided into local deformation region and non-deformation region, our proposed model only needs to calculate and update the deformation region, which can improve the simulation real-time performance. Besides, we define a compensation strategy for the "superelastic" effect which often occurs with the mass-spring model. To verify the validity of the model, we carry out a compression simulation experiment of abdomen and human foot and compare it with other models. The experimental results indicate the proposed model is realistic and effective in soft tissue compression simulation, and it outperforms other models in accuracy and real-time performance.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.4
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• pp.27-38
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• 2001

A mechanical lumped parameter model is proposed for the dynamic modeling of a semi-infinite reservoir. A semi-analytic transmitting boundary is derived for a semi-infinite 2-D reservoir of constant depth. The characteristics of the solution are examined in both frequency and time domains. Mass, damping and spring coefficients of the mechanical model are obtained to preserve the major features of the solution such as eigenfrequencies and the shapes of Bessel functions that appear as kernels in the convolution integrals. The lumped parameter model in its final form consists of two masses, a spring and two dampers for each eigenfrequency. Application examples demonstrated that the new lumped parameter model could be used for the time domain analysis of dam-reservoir systems.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.4
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• pp.72-82
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• 1990

A simple numerical analysis procedure has been proposed to trace the response of unstiffened offshore tubular members subjected to lateral impacts and eventually to estimate the consequential extent of damage. In the procedure a tubular member is reduced to a spring-mass system having two degrees-of-freedom. one for local denting deformation and the other for that of overall bending. Results of impact tests have been correlated with those of numerical analysis in order to achieve an empirical representation of the strain-rate sensitivity and other dynamic effects upon the spring coefficient for bending deformation. The theoretical estimates of extents of damage correlate reasonably well with those obtained in experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1385-1391
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• 1997

An analysis is presented on the stability of an elastic cantilever column subjected to a concentrated follower force as to the influence of the elastic restraint and a tip mass at the free end. The elastic restraint is formed by the rotatory springs. For this purpose, the governing equations and boundary conditions are derived by using Hamilton's principle, and the critical flutter loads and frequencies are obtained from the numerical evaluation of the eigenvalue functions of the considered system.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.142-144
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• 1996

For the accurate analysis of motional characteristics of electrical machines, it is needed to solve the motion equations together with the electromagnetic field equations. In this paper the sequential coupling of systems, the spring mass system and the electromagnetic system, is adopted. The induced current and the magnetic fields are calculated by FEM with given speed. And then, with the computed electromagnetic force, the mechanical equations are solved by the Runge-Kutta method. The above to processes are repeated sequentially to obtain the time domain solutions. The resultant values are applied to the energy conservation law to prove the usefulness of the proposed sequential method.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.5
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• pp.68-77
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• 1994

The authors apply the transfer influence coefficient method to the 3-dimensional vibration analysis of beam with multi-joints and formulate a general algorithm to analysis the longitudinal, flexural and torsional coupled free vibration. In this paper, the structure, which is mainly founded in the robot arms, cranes and so on, has some crooked parts, subsystems and joints but has no closed loop in this system. It is modeled as the beam of a distributed mass system with massless translational, rotational and torsional springs in each node, and joint elements of release or roll at which node the displacement vector is discontinuous. The superiorty of the present method to the transfer matrix method in the computation accuracy was confirmed by the numerical computation results. Moreover, we confirmed that boundary and intermediate conditions could ve controlled by varying the values o the spring constants.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.94-100
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• 2002

The conventional sliding mode control (SMC) technique requires a priori knowledge of the upperbounds of disturbances and/or modeling uncertainties to assure robustness. This, however, may not be easy to obtain in practical situation. This paper presents a new methodology, a sliding mode control with disturbance estimator (SMCDE), which offers a robust control performance without a priori knowledge about the disturbance. The proposed technique is featured by an average value of the imposed disturbance over a certain period. A nonlinear spring-mass-damper system and a two-link robot system are adopted as illustrative application examples. Control performances such as estimation error and tracking error are compared between the proposed methodology and conventional scheme.

• Journal of KSNVE
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• v.6 no.5
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• pp.555-565
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• 1996

This paper is concerned with the theoretical and experimental study on the force control of a miniature robotic finger that grasps an object at three other positions with the fingertip. The artificial finger is a uniform flexible cantilever beam equipped with a distributed set of compact grasping force sensors. Control action is applied by a piezoceramic bimorph strip placed at the base of the finger. The mathematical model of the assembled electro- mechanical system is developed. The distributed sensors are described by a set of concentrated mass-spring system. The formulated equations of motion are then applied to a control problem in which the finger is commanded to grasp an object. The H$_{\infty}$-controller is introduced to drive the finger. The usefulness of the proposed control technique is verified by simulation and experiment..

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.295-298
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• 1996

In this paper, a self-tuning optimal control algorithm is proposed to retain the optimal performance of an active suspension system, when the vehicle has some time varying parameters and parameter uncertainties. We consider a 2 DOF time-varying quarter car model which has the parameter variation of sprung mass, suspension spring constant and suspension damping constant. Instead of solving algebraic riccati equation on line, we propose a neural network approach as an alternative. The optimal feedback gains obtained from the off line computation, according to parameter variations, are used as the neural network training data. When the active suspension system is on, the parameters are identified by the recursive least square method and the trained neural network controller designer finds the proper optimal feedback gains. The simulation results are represented and discussed.