• Structural Engineering and Mechanics
• /
• v.44 no.6
• /
• pp.801-814
• /
• 2012

The strain rate effects on the interaction between a Mode I matrix crack and an inclined elliptic matrix-inclusion interface under dynamic tensile loadings were investigated numerically, and the results are in agreement with previous experimental data. It is found, for a given material system, that there are the first and the second critical strain rates, by which three kinds of the subsequent crack growth patterns can be classified in turn with the increasing strain rate, namely, the crack deflection, the double crack mode and the perpendicular crack penetration. Moreover, such a crack deflection/penetration behavior is found to be dependent on the relative interfacial strength, the inclined angle and the inclusion size. In addition, it is shown that the so-called strain rate effect on the dynamic strength of granule composites can be induced directly from the structural dynamic response of materials, not be entirely an intrinsic material property.

• Computational Structural Engineering
• /
• v.6 no.2
• /
• pp.95-102
• /
• 1993

A modeling method is described to provide a smaller structural dynamic model which can be used to compare finite element model of a structure with its experimental counterpart. A structural dynamic model is assumed to be represented by dynamic stiffness matrix. To validate a finite element model, it is often necessary to condense a large degrees of freedom (dofs) to a relatively small number of dofs. For these purpose, static reduction techniques are widely used. However, errors in these techniques are caused by neglecting frequency dependent terms in the functions relating slave dofs and master dofs. An alternative method is proposed in this paper in which the frequency dependent terms are considered by expressing the reduced dynamic stiffness matrix with orthogonal polynomials. The reduced model has finally a minimum set of dofs, such as sensors and excitation points and it is under the same condition as the physical system. It is proposed that the reduced model can be derived from finite element model. The procedure is applied to example structure and the results are discussed.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.1120-1123
• /
• 1996

DMC(Dynamic Matrix Control) algorithm has been successfully used in industries for more than a decade. It can handle constraints and easily extended to MIMO case. The application of DMC, however, is limited to the open loop stable process because it uses the FIR(Finite Impulse Response) or FSR(Finite Step Response) model. Integrating process widely used in chemical process industry, is the representative open loop unstable process. The disturbance rejection of DMC is relatively poor due to the assumption that the current disturbance is equivalent to the future disturbance. We propose the IDMC(Improved Dynamic Matrix Control) for the integrating process, as well as non-integrating process. IDMC has shown better disturbance rejection using multi-step ahead predictor for the disturbance.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.1 no.3
• /
• pp.11-19
• /
• 1997

In this paper, an efficient dynamic analysis method of a building structure with viscoelastic dampers is proposed. Viscoelastic dampers are used for the purpose of controlling vibration of buildings. The matrix condensation technlque based on the rigid diaphragm assumption is not readily applicable for building structures with viscoelastic dampers. An improved procedure for damping matrix condensation is employed in the proposed method to increase the efficiency of analysis. Efficiency and accuracy of the proposed method are verified through analysis of an example structure.

• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.9
• /
• pp.827-835
• /
• 2015

In this paper, we present the implementation method of Dynamic Matrix Control(DMC) block for use with a Rapid Control Prototyping(RCP) system and consider the speed control of a DC motor using the developed DMC block. Firstly, we briefly introduce a lab-built RCP system. Secondly, we present a method for implementing a DMC block using C-language, which enables the DMC algorithm to be represented in a library block that can be used in a Simulink environment. Finally, we use the developed DMC block for the speed control of a DC motor, through which we show that the DMC-based control system can be easily implemented and applied to the real-time control of systems with relatively fast dynamics.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.12
• /
• pp.1433-1441
• /
• 2009

In multibody dynamic analysis, one of the most important problems is to reduce computation times for real-time simulation. This paper presents the derivation procedure of equations of motion of a 6${\times}$6 autonomous vehicle in terms of chassis local coordinates which do not require coordinates transformation matrix to enhance efficiency for real-time dynamic analysis. Also, equations of motion are derived using the VT(velocity transformation) technique and symbolic computation method coded by MATLAB. The Jacobian matrix of the equations of motion of a system is derived from symbolic operations to apply the implicit integration method. The analysis results were compared with ADAMS results to verify the accuracy and approve the feasibility of real time analysis.

• Smart Structures and Systems
• /
• v.9 no.1
• /
• pp.55-70
• /
• 2012

It is not easy to experimentally obtain the FRF (Frequency Response Function) matrix corresponding to a full set of DOFs (degrees of freedom) for a dynamic system. Utilizing FRF data measured at specific positions, with DOFs less than that of the system, as constraints to describe a damaged system, this study identifies parameter matrices such as mass, stiffness and damping matrices of the system, and provides a damage identification method from their variations. The proposed parameter identification method is compared to Lee and Kim's method and Fritzen's method. The validity of the proposed damage identification method is illustrated in a simple dynamic system.

• Journal of KSNVE
• /
• v.9 no.1
• /
• pp.103-112
• /
• 1999

A new modeling and analysis technique for one-dimensional distributed parameter systems is presented. First. discretized equations of motion in Laplace domain are derived by applying discretization methods for partial differential equations of a one-dimensional structure with respect to spatial coordinate. Secondly. the z and inverse z transformations are applied to the discretized equations of motion for obtaining a dynamic matrix for a uniform element. Four different discretization methods are tested with an example. Finally, taking infinite on the number of step for a uniform element leads to an exact dynamic matrix for the uniform element. A generalized modal analysis procedure for eigenvalue analysis and modal expansion is also presented. The resulting element dynamic matrix is tested with a numerical example. Another application example is provided to demonstrate the applicability of the proposed method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.04a
• /
• pp.144-149
• /
• 2012

The transfer matrix method is used to determine the dynamic characteristics(natural frequencies and mode shapes) by rotational speed of wind turbine blade. The problems treated on this study is coupled flapwise bending and chordwise bending of pre-twisted nonuniform wind turbine blade. The orthogonality relations that exist between the vibrational modes is derived and the algorithm for determination of the natural vibrational characteristics is suggested.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.15 no.2
• /
• pp.93-98
• /
• 2006

This study provides a comprehensive experimental study on the dynamic characteristics of a flexible matrix composite(FMC) driveshaft. A primary objective is to verify the analytic results of the FMC drivetrain based on the equivalent complex modulus approach and the classical lamination theory. A test rig has been constructed, which consists of a FMC shaft, a foundation beam, bearings, external dampers and a driving motor. The frequency response functions and transient responses are obtained from the external excitation and the spin-up testings. It turns out that the analytic results are in good agreement with the experimental ones.