• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.18-23
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• 1990

In this paper, the dynamic modeling and a tip-position controller of a single-link flexible manipulator are developed. To design the controller of a flexible manipulator, at first, it is required to obtain the accurate dynamic model of manipulator describing both rigid motion and flexible vibration. For this purpose, FEM(Finite Element Method) and Lagrange approach are utilized to obtain the dynamic model. After obtaining the dynamic model of a single-link manipulator, a controller which computes the input torque to perform the desired trajectory is developed using neural network.

• Land and Housing Review
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• v.4 no.3
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• pp.271-277
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• 2013

The BNWF (Beam on Nonlinear Winkler Foundation) model is one of the simplest idealizations for a pile embedded in soil as it ignores the continuity of the soil. This method is difficult to model the behavior of pile group foundation subjected to lateral loading. The limitation can be overcome with the utilization of the finite element method (FEM) or finite different method (FDM) to represent a pile element embedded in a soil medium. Both the ground and piles are modeled with soild elements. The solid elements, which do not have rotational degree of freedom, is not appropriate for modeling piles. It can be overcome by substantially increasing the number of elements, which can be prohibitive for 3D modeling. This paper used the beam element and rigid link incorporated in the OpenSees to model the pile. The accuracy of the model is validated through comparison with lateral load test and BNWF analysis. It is shown that the method can capture the measured behavior accurately. It is therefore recommended to be used in group pile analyses.

• Earthquakes and Structures
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• v.7 no.4
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• pp.415-448
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• 2014

A method is presented in this paper to analyze the dynamic response behavior of suspended building structures. The effect of semi-rigid connections that link suspended floors with their supporting structure on structural performance is investigated. The connections, like the restrains in non-structural suspended components, are designed as semi-rigid to avoid pounding and as energy dissipation components to reduce structural response. Parametric study is conducted to assess the dynamic characteristics of suspended building structures with varying connection stiffness and suspended mass ratios. Modal analysis is applied to identify the two distinct sets of vibration modes, pendulum and bearing, of a suspended building structure. The cumulative modal mass is discussed to ensure the accuracy in applying the method of response spectrum analysis by SRSS or CQC modal combination. Case studies indicate that a suspended building having semi-rigid connections and proper suspended mass ratios can avoid local pounding failure and reduce seismic response.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.1-7
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• 2003

In this paper, we discuss the control scheme on active compliance control of flexible manipulators. The active compliance control scheme is extended from the scheme for rigid manipulators. To illustrate the validity of the proposed control scheme, we show experimental results for the case when the end-effector is not moving and when it is moving while applying force. Although flexible manipulators show some problems of stability yet it is clear from these results that flexible manipulators are more effective to reduce damage of environment because of link flexibility than rigid ones.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.3
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• pp.250-256
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• 2015

We present a novel method to model the body posture of a worm for vision-based automatic monitoring and analysis. The worm considered in this study is a Caenorhabditis elegans (C. elegans), which is popularly used for research in biological science and engineering. We model the posture by an open chain of a few curved or rigid line segments, in contrast to previously published approaches wherein a large number of small rigid elements are connected for the modeling. Each link segment is represented by only two parameters: an arc angle and an arc length for a curved segment, or an orientation angle and a link length for a straight line segment. Links in the proposed method can be readily related using the Denavit-Hartenberg convention due to similarities to the kinematics of an articulated manipulator. Our method was tested with real worm images, and accurate results were obtained.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.2
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• pp.94-101
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• 1996

The equations of motion for a basic industrial robotic system which has a rigid or a flexible arm are derived by Lagrange's equation, respectively. Especially, for the deflection of the flexible arm, the assumed mode method is employed. These equations are highly nonlinear equations with nonlinear coupling between the variables of motion. In order to design the control law for the rigid-arm robot, Hunt-Su's nonlinear transformation method and Marino's feedback equivalence condition are used with linear quadratic regulator(LQR) theory. The control law for the rigid-arm robot is employed to input the desired path and to provide the required nonlinear transformations for the flexible-arm robot to follow. By using the implicit Euler method to solve the nonlinear equations, the comparison of the motions between the flexible and the rigid robots and the effect of flexibility are examined.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.1
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• pp.205-213
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• 1997

In this study, dynamic analysis of a passenger car is carried out to analyze ride quality over a random road profile. The front suspension of the car is a MacPherson strut type and the rear suspension is a multi- link type. The following five different models are constructed and compared to see the effects of engine vibration and chassis flexibility in the ride quality. (1) one rigid chassis model, (2) a rigid chassis and rigid engine model, (3) a rigid engine and flexible chassis model with one vibration mode, (4) one flexible chassis model with six engine vibration modes and one chassis vibration mode, (5) one flexible chassis model with seven vibration modes and four static correction modes. The result shows that engine vibration modes and the first bending mode of the chassis are important in the ride quality.

• Steel and Composite Structures
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• v.51 no.3
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• pp.305-323
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• 2024

Previous experimental studies have effectively demonstrated the remarkable efficiency of the stiffened channel link in connecting circular columns and I-shaped beams. This research aims to present design criteria and assess the seismic properties of this specific connection type through numerical modeling. Various parameters, including stiffener type and geometric properties of the stiffened channel element, were duly taken into account. The findings from over 136 nonlinear finite element analyses (FEAs) reveal that the recommended detailing scheme reliably satisfies all the regulations specified for rigid beam-to-column connections in special moment frames.

• Steel and Composite Structures
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• v.34 no.5
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• pp.625-641
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• 2020

The realistic modeling of the beam-column semi-rigid connection in steel frames attracted the attention of many researchers in the past for the seismic analysis of semi-rigid frames. Comparatively less studies have been made to investigate the behavior of steel frames with semi-rigid connections under different types of earthquake. Herein, the seismic behavior of semi-rigid steel frames is investigated under both far and near-field earthquakes. The semi-rigid connection is modeled by the multilinear plastic link element consisting of rotational springs. The kinematic hysteresis model is used to define the dynamic behavior of the rotational spring, describing the nonlinearity of the semi-rigid connection as defined in SAP2000. The nonlinear time history analysis (NTHA) is performed to obtain response time histories of the frame under scaled earthquakes at three PGA levels denoting the low, medium and high-level earthquakes. The other important parameters varied are the stiffness and strength parameters of the connections, defining the degree of semi-rigidity. For studying the behavior of the semi-rigid frame, a large number of seismic demand parameters are considered. The benchmark for comparison is taken as those of the corresponding rigid frame. Two different frames, namely, a five-story frame and a ten-story frame are considered as the numerical examples. It is shown that semi-rigid frames prove to be effective and beneficial in resisting the seismic forces for near-field earthquakes (PGA ≈ 0.2g), especially in reducing the base shear to a considerable extent for the moderate level of earthquake. Further, the semi-rigid frame with a relatively weaker beam and less connection stiffness may withstand a moderately strong earthquake without having much damage in the beams.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1371-1381
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• 1995

A novel hybrid control scheme to actively control the endpoint position of a very flexible single-link manipulator is proposed. The control scheme consists of a motor mounted at the beam hub and a piezofilm actuator bonded to the surface of the flexible link. The control torque of the motor to produce a desired motion is firstly determined by employing the sliding mode control theory on the equation of motion of the rigid link having the same mass as that of the proposed flexible link. The torque is then applied to the flexible manipulator in order to activate the commanded motion. During the motion, undesirable oscillation is actively suppressed by applying a feedback control voltage to the piezofilm actuator. Consequently, the imposed desired position is accomplished. In order to demonstrate high control performances accrued from the proposed method, computer simulations are undertaken by treating both regulating and tracking control problems.