• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.35 no.12
• /
• pp.567-572
• /
• 1986

In this paper, a new type of step motor with two degree of mechanical freedom, which is named rotary-Linear Step Motor(RLSM), is presented. Its rotor axis can perform linear and rotary motions either separately or simultaneously. This paper discribes the design of RLSM using finite element method in which the magnetic saturation effect of the iron core is taken into account. The design parameters such as torques, forces and inductances are obtained from the computed magnetic vector potentials. A new type of Rotary-Linear Step Motor was constructed. The calculated parameters agree well with measurements.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.106.6-106
• /
• 2001

In this paper, a four-degree-of-freedom non-linear model is developed to study the dynamic response of vehicle that is caused by the disturbance from the road. The chaotic vibration of the model is investigated with numerical simulation. The model displays complicated dynamic responses including harmonic motions and chaos. It is found that changing of the damping coefficients of the system can eliminate the chaotic response.

• Tribology and Lubricants
• /
• v.17 no.1
• /
• pp.64-71
• /
• 2001

This paper presents dynamic responses of disk flutter and bump in HDD slider. The slider is modeled for three degree-of-freedom systems, which are capable of lifting, pitching, and rolling motions. In numerical analysis, loads from air pressure, preload and static moments from the slider, and stiffness and damping coefficients of the suspension are considered for investigating the dynamic characteristics analysis. The numerical results are presented as functions of typical parameters such as a disk velocity, stiffness and damping coefficients of the suspension, and skew angle.

• Earthquakes and Structures
• /
• v.11 no.1
• /
• pp.165-178
• /
• 2016

The goal of energy-based seismic design is to obtain a structural design with a higher energy dissipation capacity than the energy dissipation demands incurred under earthquake motions. Accurate estimation of the story hysteretic energy demand of a multi-story structure is the key to meeting this goal. Based on the assumption of a mode-equivalent single-degree-of-freedom system, the energy equilibrium relationship of a multi-story structure under seismic action is transformed into that of a multi-mode analysis of several single degree-of-freedom systems. A simplified equation for the estimation of the story seismic hysteretic energy demand was then derived according to the story shear force and deformation of multi-story buildings, and the deformation and energy relationships between the mode-equivalent single-degree-of-freedom system and the original structure. Sites were categorized into three types based on soil hardness, namely, hard soil, intermediate hard (soft) soil, and soft soil. For each site type, a 5-story and 10-story reinforced concrete frame structure were designed and employed as calculation examples. Fifty-six earthquake acceleration records were used as horizontal excitations to validate the accuracy of the proposed method. The results verify the following. (1) The distribution of seismic hysteretic energy along the stories demonstrate a degree of regularity. (2) For the low rise buildings, use of only the first mode shape provides reasonably accurate results, whereas, for the medium or high rise buildings, several mode shapes should be included and superposed to achieve high precision. (3) The estimated hysteretic energy distribution of bottom stories tends to be underestimated, which should be modified in actual applications.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.26 no.6
• /
• pp.237-246
• /
• 2022

Based on the random-vibration-theory methodology, dynamic responses of nuclear facilities subjected to obliquely incidental and incoherent earthquake ground motions are calculated. The spectral power density functions of the 6-degree-of-freedom motions of a rigid foundation due to the incoherent ground motions are obtained with the local wave scattering and wave passage effects taken into consideration. The spectral power density function for the pseudo-acceleration of equipment installed on a structural floor is derived. The spectral acceleration of the equipment or the in-structure response spectrum is then estimated using the peak factors of random vibration. The approach is applied to nuclear power plant structures installed on half-spaces, and the reduction of high-frequency earthquake responses due to obliquely incident incoherent earthquake ground motions is examined. The influences of local wave scattering and wave passage effects are investigated for three half-spaces with different shear-wave velocities. When the shear-wave velocity is sufficiently large like hard rock, the local wave scattering significantly affects the reduction of the earthquake responses. In the cases of rock or soft rock, the earthquake responses of structures are further affected by the incident angles of seismic waves or the wave passage effects.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.12
• /
• pp.2687-2694
• /
• 2002

A precision displacement measuring system is proposed, which can detect the 3-DOF translational motions of precision positioning devices. The optical system, which is composed of two diode-laser sources and two quadratic PSDs, is adapted to detect the position of the spherical reflector usually mounted on the platform of positioning devices. Each of the laser beams from diode-laser sources is reflected at the highly reflective surface of the sphere; hence, the 3-dimensional position of the sphere causes the directional change of the reflected beams, which is detected by the PSDs. In this paper, we define the relationships between the output values of the two PSDs and the 3-DOF translational motions of the sphere. Based on a deduced measurement model, we perform measurement simulation and evaluate the performance of the proposed measurement system: linearity, sensitivity, measuring range, and measurement error. The results show that the proposed measuring method is very useful for the measurement of the precision displacement of 3-DOF micro motions.

• Earthquakes and Structures
• /
• v.9 no.3
• /
• pp.673-698
• /
• 2015

This paper investigates inelastic seismic demands of the normal component of near-fault pulse-like ground motions, which differ considerably from those of far-fault ground motions and also parallel component of near-fault ones. The results are utilized to improve the nonlinear static procedure (NSP) called Displacement Coefficient Method (DCM). 96 near-fault and 20 far-fault ground motions and the responses of various single degree of freedom (SDOF) systems constitute the dataset. Nonlinear Dynamic Analysis (NDA) is utilized as the benchmark for comparison with nonlinear static analysis results. Considerable influences of different faulting mechanisms are observed on inelastic seismic demands. The demands are functions of the strength ratio and also the pulse period to structural period ratio. Simple mathematical expressions are developed to consider the effects of near-fault motion and fault type on nonlinear responses. Modifications are presented for the DCM by introducing a near-fault modification factor, $C_N$. In locations, where the fault type is known, the modifications proposed in this paper help to obtain a more precise estimate of seismic demands in structures.

• Journal of the Korea Computer Graphics Society
• /
• v.3 no.1
• /
• pp.1-7
• /
• 1997

Technology for the realistic model and the motion control of human is applied to many areas of computer graphics, virtual reality and computer simulations. Human body is a multi-articular body. Generally, to create a human model and motions. articulated body models are generated and their motions are controlled based upon kinematics. The hand of the human consists of many small articulations and each articulations have a various degree of freedom. This paper presents a model of human hand which is based on the two kinds of constraints to control the motions of the hand realistically. To build a hand model, we experimented the anatomy of the human hand, and the diverse motions of the hand are tested.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.36 no.6
• /
• pp.371-380
• /
• 2023

To calculate seismic fragility, it is important to select input earthquake ground motions that can properly express the characteristics of the target site. This study analyzed the seismic fragility of a single-degree-of-freedom (SDOF) model based on input earthquake ground motions in strong and low-to-moderate seismic regions. As a first step, a total of four sets of input earthquake ground motions were selected,: two sets measured near or far from overseas strong earthquake records and two sets exhibiting the characteristics of low-to-moderate earthquake regions in South Korea. A nonlinear SDOF model for three natural periods was applied to the target structure, and incremental dynamic analysis was used for fragility analysis. In addition, four damage states were defined, and seismic fragility results for each natural period of the nonlinear SDOF model for the four aforementioned input earthquake ground motion sets were obtained for each damage state.

• Earthquakes and Structures
• /
• v.17 no.6
• /
• pp.577-590
• /
• 2019

The seismic response of structures to strong ground motions is a complex problem that has been studied for decades. However, most of current seismic regulations do not assess the potential level of damage that a structure may undergo during a strong earthquake. This will happen in spite that the design objectives for any structural system are formulated in terms of acceptable levels of damage. In this article, we analyze the expected damage in single-degree-of-freedom systems subjected to long-duration ground motions generated in soft soil sites, such as those located in the lakebed of Mexico City. An energy-based methodology is formulated, under the consideration of input energy as the basis for the evaluation process, to estimate expected damage. The results of the proposed methodology are validated with damage curves established directly with nonlinear dynamic analyses.