• Journal of Institute of Control, Robotics and Systems
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• v.20 no.11
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• pp.1125-1130
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• 2014

In this paper, we discuss the relation between the motion profile and pre-filter. As previously reported in various literatures [1-3], a tuned motion profile can effectively reduce residual vibration by placing inherent zeros of the motion profile at the vibratory pole of systems similar to the role of the input shaping technique. From the results, we factorize the motion profile into a basis function and an input shaper. In contrast to the previously reported impulse-sequence-based input shapers, the input shaper extracted from the motion profile has unique characteristics. Thanks to the characteristics of the input shaper extracted from the motion profile, it has advantages to reduce the vibrations caused by not only the modeled vibratory mode but also unmodeled dynamics which exist in higher frequency ranges.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.5
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• pp.209-217
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• 2013

In order to verify the reliability of numerical site response analysis program, both soil free-field and base rock input motions should be provided. Beside the field earthquake motion records, the most effective testing method for obtaining the above motions is the dynamic geotechnical centrifuge test. However, need is to verify if the motion recorded at the base of the soil model container in the centrifuge facility is the true base rock input motion or not. In this paper, the appropriate input motion measurement method for the verification of seismic response analysis is examined by dynamic geotechnical centrifuge test and using three-dimensional finite difference analysis results. From the results, it appears that the ESB (equivalent shear beam) model container distorts downward the propagating wave with larger magnitude of centrifugal acceleration and base rock input motion. Thus, the distortion makes the measurement of the base rock outcrop motion difficult which is essential for extracting the base rock incident motion. However, the base rock outcrop motion generated by using deconvolution method is free from the distortion effect of centrifugal acceleration.

• Earthquakes and Structures
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• v.2 no.2
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• pp.171-187
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• 2011

Rational scaling of design earthquake ground motions for tall buildings is essential for safer, risk-based design of tall buildings. This paper provides the structural designers with an insight for more rational scaling based on drift and input energy demands. Since a resonant sinusoidal motion can be an approximate critical excitation to elastic and inelastic structures under the constraint of acceleration or velocity power, a resonant sinusoidal motion with variable period and duration is used as an input wave of the near-field and far-field ground motions. This enables one to understand clearly the relation of the intensity normalization index of ground motion (maximum acceleration, maximum velocity, acceleration power, velocity power) with the response performance (peak interstory drift, total input energy). It is proved that, when the maximum ground velocity is adopted as the normalization index, the maximum interstory drift exhibits a stable property irrespective of the number of stories. It is further shown that, when the velocity power is adopted as the normalization index, the total input energy exhibits a stable property irrespective of the number of stories. It is finally concluded that the former property on peak drift can hold for the practical design response spectrum-compatible ground motions.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.76-82
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• 2010

This paper presents a seismic response analysis of bridge structures considering the spatial variation of input ground motion. In earthquake analyses of structures, it is usually assumed that the input ground motion is the same at every support. However, this assumption is not justified for long structures like bridges, because observations have shown that the earthquake ground motion can vary considerably within relatively small distances. When the soil under the foundation is relatively soft and deep, an analysis of the foundation-soil interaction must always be performed. To consider the foundation-soil interaction, a soil response analysis is performed first, and after determining the material characteristics of the foundation element obtained by this foundation-soil interaction analysis, the seismic response analysis of a bridge superstructure with equivalent springs and dampers is performed. Finally, the influences of the spatial variation in the input motion, which are affected by different soil characteristics, are considered.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.284-291
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• 2006

This paper presents a seismic response analysis of bridge structures considering foundation-soil interaction and multi-support input motion. In the earthquake analysis of structures it is usually assumed that the input ground motion is the same at all supports. However, this assumption is not justified for long structures like bridges, because observations have shown the earthquake ground motion can vary considerably within relatively small distances. When the soil under the foundation is relatively soft and deep, analysis for foundation-soil interaction always must be peformed. To consider foundation-soil interaction, soil response analysis is preceded, and after determining the material characteristics of foundation element obtained by foundation-soil interaction analysis at the frequency domain, the seismic response analysis of bridge superstructure with the equivalent spring and damper is performed. Finally, influences of multi-support input motion, which are affected by different soil characteristics, are also considered in this paper.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.1
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• pp.11-20
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• 2008

In probabilistic seismic analysis of nonlinear structural system, dynamic analysis is performed to obtain the distribution of the response estimate using input ground motion time histories which correspond to a given seismic hazard level. This study investigates the differences in the distribution of the responses and the failure probability according to input ground motion models. Two types of input ground motion models are considered: real earthquake records scaled to specified intensity level and artificial input ground motion fitted to design response spectrum. Simulation results fir a nonlinear SDOF system demonstrate that the spectrum matched input ground motion produces larger failure probability than those of scaled input ground motion due to biased responses. Such tendency is more remarkable in the site of soft soil conditions. Analysis results show that such difference of failure probability is due to the conservative estimation of design response spectrum in the range of long period of ground motion.

• The Journal of Korean Institute for Practical Engineering Education
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• v.5 no.1
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• pp.34-39
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• 2013

This paper suggests an input device that allows a user not only to naturally interact with education contents in virtual environment but also to sense haptic feedback according to his/her interaction. The proposed system measures a user's motion and then creates haptic feedback based on the measured position. To create haptic information in response to a user's interaction with educational contents in virtual environment, we develop a motion input device which consists of a motion controller, a haptic actuator, a wireless communication module, and a motion sensor. To measure a user's motion input, an accelerometer is used as the motion sensor. The experiment shows that the proposed system creates continuous haptic sensation without any jerky motion or vibration.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04a
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• pp.631-636
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• 1995

A robotic wrist with three rolling motion is considered. It has the gear trains with three independent input parameters and mechanical interference in their motion. This paper presents dervation of basic kinematic equations that relate the input parameters and the orientation of the end-effector, determination of singularities in its motion, and the computational procedure of the inverse kinematics.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.1
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• pp.56-64
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• 2013

We propose an efficient minimum-time cornering motion planning algorithms for differential-driven wheeled mobile robots with motor control input constraint, under piecewise constant control input sections. First, we established mobile robot's kinematics and dynamics including motors, divided the cornering trajectory for collision-free into one translational section, followed by one rotational section with angular acceleration, and finally the other rotational section with angular deceleration. We constructed an efficient motion planning algorithm satisfying the bang-bang principle. Various simulations and experiments reveal the performance of the proposed algorithm.

• Geomechanics and Engineering
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• v.22 no.1
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• pp.25-33
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• 2020

In metropolitan areas, the quantity and density of the underground structure increase rapidly in recent years. Even though most damage incidents of the underground structure were minor, there were still few incidents causing a great loss in lives and economy. Therefore, the safety evaluation of the underground structure becomes an important issue in the disaster prevention plan. Liquefaction induced uplift is one important factor damaging the underground structure. In order to perform a preliminary evaluation on the safety of the underground structure, simplified prediction equations were introduced to provide a first order estimation of the liquefaction induced uplift. From previous studies, the input motion is a major factor affecting the magnitude of the uplift. However, effects of the input motion were not studied and included in these equations in an appropriate and rational manner. In this article, a numerical simulation approach (FLAC program with UBCSAND model) is adopted to study effects of the input motion on the uplift. Numerical results show that the uplift and the Arias Intensity (Ia) are closely related. A simple modification procedure to include the input motion effects in the Sasaki and Tamura prediction equation is proposed in this article for engineering practices.