• Wind and Structures
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• v.9 no.2
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• pp.159-178
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• 2006

For the slender and flexible cable supported bridges, identification of all the flutter derivatives for the vertical, lateral and torsional motions is essential for its stability investigation. In all, eighteen flutter derivatives may have to be considered, the identification of which using a three degree-of-freedom elastic suspension system has been a challenging task. In this paper, a system identification technique, known as covariance-driven stochastic subspace identification (COV-SSI) technique, has been utilized to extract the flutter derivatives for a typical bridge deck. This method identifies the stochastic state-space model from the covariances of the output-only (stochastic) data. All the eighteen flutter derivatives have been simultaneously extracted from the output response data obtained from wind tunnel test on a 3-DOF elastically suspended bridge deck section-model. Simplicity in model suspension and measurements of only output responses are additional motivating factors for adopting COV-SSI technique. The identified discrete values of flutter derivatives have been approximated by rational functions.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.17-20
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• 2002

In this paper voltage distribution in stator windings of induction motor driven by IGBT PWM inverter is studied. To analyze the irregular voltage of stator winding, equivalent circuit model of inverter-cable-motor was proposed and high frequency parameter is computed by using finite element method (FEM). Electro-magnetic transient program (EMTP) analysis of the whole system for induction motor and PWM inverter is proposed. Induction motor, 50[HP], and a switching surge generator was built to consider the voltage distribution. The results of EMTP analysis compared with experimental results.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.1
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• pp.43-49
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• 2005

The high rate of voltage rise (dv/dt) in motor terminals caused by high-frequency switching and impedance mismatches between inverter and motor are known as the primary causes of irregular voltage distributions and insulation breakdowns on stator windings in IGBT PWM inverter-driven induction motors. In this paper, voltage distributions in the stator windings of an induction motor driven by an IGBT PWM inverter are studied. To analyze the irregular voltages of stator windings, high frequency parameters are derived from the finite element (FE) analysis of stator slots. An equivalent circuit composed of distributed capacitances, inductance, and resistance is derived from these parameters. This equivalent circuit is then used for simulation in order to predict the voltage distributions among the turns and coils. The effects of various rising times in motor terminal voltages and cable lengths on the stator voltage distribution are also presented. For a comparison with simulations, an induction motor with taps in the stator turns was made and driven by a variable-rising time switching surge generator. The test results are shown.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.51.4-51
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• 2002

$\textbullet$ A noval haptic mouse system is developed for human computer interface. $\textbullet$ Five bar mechanism is adapted for 2 dof force feedback with virtual environment. $\textbullet$ Double prismatic joint type mechanism is adapted to reflect 1 dof grabbing force feedback. $\textbullet$ Cable driven mechansim is used for actuation to reduce backlash and endow backdrivability. $\textbullet$ Virtual wall perception experiment is conducted to obtain force specification for haptic mouse. $\textbullet$ Average mouse workspace is measured using magnetic position tracker.

• Wind and Structures
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• v.30 no.6
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• pp.633-648
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• 2020

The objective of this work was to investigate the interference effects of two-parallel bridge decks on aerodynamic coefficients, vortex-induced vibration, flutter instability and flutter derivatives. The two bridges have significant difference in cross-sections, dynamic properties, and flutter speeds of each isolate bridge. The aerodynamic static tests and aeroelastic tests were performed in TU-AIT boundary layer wind tunnel in Thammasat University (Thailand) with sectional models in a 1:90 scale. Three configuration cases, including the new bridge stand-alone (case 1), the upstream new bridge and downstream existing bridge (case 2), and the downstream new bridge and the upstream existing bridge (case 3), were selected in this study. The covariance-driven stochastic subspace identification technique (SSI-COV) was applied to identify aerodynamic parameters (i.e., natural frequency, structural damping and state space matrix) of the decks. The results showed that, interference effects of two bridges decks on aerodynamic coefficients result in the slightly reduction of the drag coefficient of case 2 and 3 when compared with case 1. The two parallel configurations of the bridge result in vortex-induced vibrations (VIV) and significantly lower the flutter speed compared with the new bridge alone. The huge torsional motion from upstream new bridge (case 2) generated turbulent wakes flow and resulted in vertical aerodynamic damping H1^* of existing bridge becomes zero at wind speed of 72.01 m/s. In this case, the downstream existing bridge was subjected to galloping oscillation induced by the turbulent wake of upstream new bridge. The new bridge also results in significant reduction of the flutter speed of existing bridge from the 128.29 m/s flutter speed of the isolated existing bridge to the 75.35 m/s flutter speed of downstream existing bridge.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.9
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• pp.840-845
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• 2010

This paper proposes the method indirectly measuring the operating force of the end-effect tip of surgical robot instrument which conducts the surgical operation in the body on behalf of the surgeon's hand. Due to the size and safety obligation to the surgical robot instrument, it is difficult to measure the operation force of its tip like grasping force. However the instrument is driven by cable-pulley torque transmission mechanism and when some force is occurred at the tip, then the reaction force appears on the cable as additional tension. Based on this phenomenon, this paper proposes a method to estimate the operating force from measuring reaction force against the driving motor by using a loadcell. And it induces mathematical equation to calculate the force from loadcell by approaching the modulus of elasticity to high order polynomial. And this paper proves the validity of proposed mechanism by experimental test.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.9
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• pp.833-839
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• 2010

In this paper, a novel 1 DOF hand rehabilitation robot is proposed in consideration of ADL training for stroke patients. To perform several ADL trainings, the proposed robot can move the thumb part and the part of 4 fingers simultaneously and realize the full ROM (Range of Motion) in grasp. Based on these characteristics, the proposed robot realizes several types of grasp such as cylindrical grasp, lateral grasp, and pinch grasp by using a passive revolute joint that can change the thumb movement direction. The movement of the thumb is driven by a cable mechanism and the part of 4 fingers is moved by a four-bar linkage mechanism.

• The Journal of Korea Robotics Society
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• v.7 no.1
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• pp.20-28
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• 2012

In spite of the difficulties and uncertain characteristic of cable driven method, surgical robot instrument has adopted it as driving mechanism for various reasons. To overcome the problem of cable system, previous research applied SMCSPO (sliding mode control with sliding perturbation observer) algorithm as robust controller to control the instrument and found that the value of SPO (sliding perturbation observer) followed force disturbance, reaction force loaded on the tip very similarly. Thus, this paper confirms that the perturbation observer is sufficient estimator which finds out the mount of loaded force on the surgical robot instrument. To prove the proposition, simulation using the similar model with an actual instrument and experimental evaluation are performed. The results show that it is possible to substitute SPO for sensors to measure the reaction force. This estimated reaction force will be used to realize haptic function by sending the reaction force to a master device for a surgeon. The results will contribute to create surgical benefit such as shortening the practice time of a surgeon and giving haptic information to surgeon by using it as haptic signal to protect an organ by making force boundary.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.415-420
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• 2017

Underactuated prosthetic hands are relatively light and economical. In this work, an economical grasping force control system is proposed for underactuated prosthetic hands with adaptive grasp capability. The prosthetic hand is driven by a main cable based on a set of electromyography sensors on the forearm of a user. Part of the main cable tension related to grasping force is fed back to the user by a skin-mounted vibrator. The proper relationship between the grasping force and the vibrator drive voltage was established and prototype tests were performed on a group of users. Relatively accurate grasping force control was achieved with minimal training of users.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.338-342
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• 2008

Hybrid Electric Vehicle(HEV) is driven by an internal-combustion engine and an electric motor. It is a combination of an internal-combustion engine and several electrical equipments which use a high voltage battery, an electric motors, an inverter and others. But there is not any separate detailed enforcement regulations for high voltage electric appliances in the existing vehicle-related safety standards. So, test standards suggestion as well as test technique development need to be done for ensuring electrical safety, for an electric motor, a high voltage battery, a(n) inverter/converter and an electric power transmission units and other equipments to ensure the safety of high voltage electric appliances which is the HEV key electrical component. In this paper, We are to provide helpful data to support test technique development and test standard establishment for HEV design and electrical safety security by the following methods; by measuring the voltage, the electric current, and the frequency of HEV, by analyzing electrical characteristics of high voltage electric appliances, and by analyzing temperature characteristics of the electrical current among the analyzed electrical characteristics by thermal imagining cameras.