• Smart Structures and Systems
• /
• 제26권5호
• /
• pp.591-603
• /
• 2020

Dynamic deflection monitoring is an essential and critical part of structural health monitoring for high-speed railway bridges. Two critical problems need to be addressed when using inclinometer sensors for such applications. These include constructing a general representation model of inclination-deflection and addressing the ill-posed inverse problem to obtain the accurate dynamic deflection. This paper provides a dynamic deflection monitoring method with the placement of optimal inclinometer sensors for high-speed railway bridges. The deflection shapes are reconstructed using the inclination-deflection transformation model based on the differential relationship between the inclination and displacement mode shape matrix. The proposed optimal sensor configuration can be used to select inclination-deflection transformation models that meet the required accuracy and stability from all possible sensor locations. In this study, the condition number and information entropy are employed to measure the ill-condition of the selected mode shape matrix and evaluate the prediction performance of different sensor configurations. The particle swarm optimization algorithm, genetic algorithm, and artificial fish swarm algorithm are used to optimize the sensor position placement. Numerical simulation and experimental validation results of a 5-span high-speed railway bridge show that the reconstructed deflection shapes agree well with those of the real bridge.

• Applied Microscopy
• /
• 제45권2호
• /
• pp.37-43
• /
• 2015

In present work, work-hardening behavior of TiCu-based bulk metallic glass composite with B2 particles has been studied by systemic structural and mechanical investigations. After yield, pronounced work-hardening of the alloy was clearly exhibited, which was mainly related to the martensitic transformation as well as the deformation twinning in B2 particles during deformation. At the early plastic deformation stage (work-hardening stage), the stress-induced martensitic transformation from B2 phase to B19' phase and deformation-induced twinning of B19' phase was preferentially occurred in the around interface areas between B2 phase and amorphous matrix by stress concentration. The higher hardness value was observed in vicinity of interface within the B2 particles which are probably connected with martensitic transformation and deformation twinning. This reveals that the work-hardening phenomenon of this bulk metallic glass composite is a result of the hardening of B2 particles embedded in amorphous matrix.

• 한국생산제조학회지
• /
• 제9권2호
• /
• pp.102-111
• /
• 2000

Methodology of volumetric error identification and compensation is presented to improve the accuracy of NC machine tools by using a reference artifact and a touch trigger probe. Homogeneous transformation matrix and kinematic chain are used for modeling the geo-metric and thermal errors of a three-axis vertical machining center. The reference artifact is designed and fabricated to identify the model parameters by machine tool metrology. Parameters in the error model are able to be identified and updated by direct measurement of the reference artifact on the machine tool under the actual conditions which include the thermal interactions of error sources. A volumetric error compensation system based on IBM/PC is linked with a FANUC CNC controller to compensate for the identified volumetric error in machining workspace.

• 대한기계학회논문집A
• /
• 제25권12호
• /
• pp.1966-1973
• /
• 2001

The Jacobian matrix of the equations of motion of a system using velocity transformation technique is derived via variation methods to apply the implicit integration algorithm, DASSL. The concept of generalized coordinate partitioning is used to parameterize the constraint set with independent generalized coordinates. DASSL is applied to determine independent generalized coordinates and velocities. Dependent generalized coordinates, velocities, accelerations and Lagrange multipliers are explicitly retained in the formulation to satisfy all of the governing kinematic and dynamic equations. The derived Jacobian matrix of a system is proved to be valid and accurate both analytically and through solution of numerical examples.

• 비파괴검사학회지
• /
• 제31권3호
• /
• pp.233-245
• /
• 2011

A new BWIM(bridge weigh-in-motion) algorithm using both measured strain and acceleration data is proposed. To consider the effects of bridge vibration on the estimation of moving loads, the dynamic governing equation is applied with the known stiffness and mass properties but damping is ignored. Dynamic displacements are computed indirectly from the measured strains using the beam theory and accelerations are measured directly by accelerometers. To convert a unit moving load to its equivalent nodal force, a transformation matrix is determined. The incompleteness in the measured responses is considered in developing the algorithm. To examine the proposed BWIM algorithm, simulation studies, laboratory experiments and field tests were carried. In the simulation study, effects of measurement noise and estimation error in the vehicle speed on the results were investigated.

• Journal of Electrical Engineering and Technology
• /
• 제11권1호
• /
• pp.241-246
• /
• 2016

This paper presents a method that can improve the performance of permanent magnet synchronous motor current control by minimizing the measured current phase delay caused by the Low Pass Filter(LPF) used to cut off the noises that flowed in when feedback currents are measured. Although existing methods that change the Cutoff Frequency of the LPF can minimize phase delays during high speed rotations, their noise cutoff effects are much lower and this may lead to the decline of control performance. Therefore, in this study, an algorithm that can compensate current phase delays through relatively simple calculations from the synchronous motor d-q axis coordinate transformation matrix and the inverse transformation matrix is proposed and the validity of the proposed method is verified by comparing the waveform of the calculated current with the waveform of actual currents through simulations and experiments.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.638-640
• /
• 2001

In this paper, system equation of the magnetic equivalent circuit of the induction motor be consist of the magnetomotive force transformation matrix and the flux transformation matrix. The system equation is fed by three phase sinusoidal current and get to magnetomotive force on the teeth. This study confirmed the time and spatial distribution of the magnetomotive force on the teeth created by the winding.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 춘계학술대회 논문집
• /
• pp.1321-1324
• /
• 2004

Unbalanced systems, such as distribution systems, have difficulties in fault locations due to single-phase laterals and loads. In this paper, a novel fault location algorithm is suggested for a line to line faults using inverse theorem of matrix on electric power lines. The fault location for balanced systems has been studied using the current distribution factor, by a conventional symmetrical transformation, but that for unbalanced systems has not been investigated due to their high complexity The proposed algorithms overcome the limit of the conventional algorithm using the conventional symmetrical transformation, which requires the balanced system and are applicable to any electric power system but are particularly useful for unbalanced distribution systems. The simulation results oriented by the real distribution system are presented to show its effectiveness and accuracy.

• 대한기계학회논문집
• /
• 제14권2호
• /
• pp.324-330
• /
• 1990

In this study, in order to perform dynamic design of machine tools reasonably and effectively, a method was formulated to be applicable to the damped structures connected by joints having elasticity and damping by using substructure synthesis method. And a nonlinear solution method was proposed and it formulates the nonlinear parts by describing functions and uses the reducing transformation matrix by the substructure synthesis method. The results of frequency response analysis of a machine tool, where an NC lathe was partitioned by three parts of spindle, housing and bed-base part and the nonlinearity of bearing parts between spindle and housing was modelled, showed force dependency of the response.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1996년도 춘계학술대회 논문집
• /
• pp.738-742
• /
• 1996

In the present paper, We have tried to reconfirm the "Interlligent" material properties using both the sintered TiNi/A(1100) matrix composite by powder metallurgy method. By using these specimen, Shape meorystrengthening effect in tensile strengthand fatigue crack propagation above inverse transformation temperature of TiNi fiber were investigated. More over, by SEM obsevation, the effect of the residual stress at the interface between A1 matrix and TiNi fiber and some brittle precipitation layers such as inter metallic compounds on fracture mechanisms was metallurgically discussed.discussed.