• Title/Summary/Keyword: Free Torque

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Effects of elastic medium on buckling of microtubules due to bending and torsion

  • Taj, Muhammad;Hussain, Muzamal;Afsar, Muhammad A.;Safeer, Muhammad;Ahmad, Manzoor;Naeem, Muhammad N.;Badshah, Noor;Khan, Arshad;Tounsi, Abdelouahed
    • Advances in concrete construction
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    • v.9 no.5
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    • pp.491-501
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    • 2020
  • Microtubules buckle under bending and torsion and this property has been studied for free microtubules before using orthotropic elastic shell model. But as microtubules are embedded in other elastic filaments and it is experimentally showed that these elastic filaments affect the critical buckling moment and critical buckling torque of the microtubules. To prove that, we developed orthotropic Winkler like model and demonstrated that the critical buckling moment and critical buckling torque of the microtubules are orders of higher magnitude than those found for free microtubules. Our results show that Critical buckling moment is about 6.04 nNnm for which the corresponding curvature is about θ = 1.33 rad /㎛ for embedded MTs, and critical buckling torque is 0.9 nNnm for the angle of 1.33 rad/㎛. Our results well proved the experimental findings.

Numerical Analysis of Flow around Propeller Rotating Beneath Free Surface (자유수면 아래에서 회전하는 프로펠러 주위 유동 수치 해석)

  • Park, Il-Ryong
    • Journal of Ocean Engineering and Technology
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    • v.29 no.6
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    • pp.427-435
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    • 2015
  • This paper provides the numerical results of a simulation of the flow around a propeller working beneath the free surface. A finite volume method is used to solve the unsteady Reynolds averaged Navier-Stokes (URANS) equations, where the wave-making problem is solved using a volume-of-fluid (VOF) method. The numerical analysis focuses on the propeller wake structure affected by the free surface, where we consider another free surface boundary condition that treats the free surface as a rigid wall surface. The propeller wake under the effect of these two free surface conditions shows a reduction in the magnitude of the longitudinal and vertical flow velocities, and its vortical structures strongly interact with the free surface. The thrust and torque coefficient under the free surface effect decrease about 3.7% and 3.1%, respectively. Finally, the present numerical results show a reasonable agreement with the available experimental data.

Disturbance Torque Suppression Control of Servo Motors for Missile Fin Actuators (미사일 Fin 액츄에이터용 서보모터의 외란 토크 억제 제어)

  • Kim, Chang-Hwan
    • Journal of National Security and Military Science
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    • s.1
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    • pp.311-343
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    • 2003
  • In this paper, we propose a generalized disturbance torque suppression control scheme of servo motors for missile fin actuators. Our controller consists of both a model based feed-forward controller and a stabilizing feedback controller. The feed-forward controller is designed such that the output of nominal plant tracks perfectly the reference position command with a desired dynamic characteristics. The feedback controller stabilizes the overall closed loop system. Furthermore, the feedback controller contains a free function that can be chosen arbitrary. The free function can be designed so as to achieve both the suppression of disturbances and the robustness to model uncertainties. In order to illuminate the superior performance of our control scheme to the conventional ones, we present some simulation results.

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Tuning-free Anti-windup Strategy for High Performance Induction Machine Drives (고성능 유도전동기 구동을 위한 자동 튜닝 Anti-windup 기법)

  • Seok Jul-Ki;Bae Sang-Gyu;Lee Dong-Choon
    • Proceedings of the KIPE Conference
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    • 2004.07a
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    • pp.312-315
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    • 2004
  • This paper presents a tuning-free conditional integration anti-windup strategy for induction machine with Proportional-Integral (PI) type speed controller. The on/off condition of integral action is determined by the frequency domain analysis of machine torque command without a prior knowledge of set-point changes. There are no tuning parameters to be selected by users for anti-windup scheme. In addition, the dynamic performance of the proposed scheme assures a desired tracking response curve with minimal oscillation and settling time even in the change of operating conditions. This algorithm is useful in many high performance induction machine applications not to allow the oscillation and overshoot of speed/torque responses. The main idea can be extended to general applications such as chemical processes and industrial robots.

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Control of Biped Robots Based on Impedance Control and Computed-Torque Control (계산-토크 제어와 임피던스 제어를 이용한 2족 보행 로봇의 제어)

  • Jeong, Ho-Am;Park, Jong-Hyeon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.6 s.177
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    • pp.1513-1519
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    • 2000
  • This paper proposes a hybrid control method of using impedance control and the computed-torque control for biped robot locomotion. Computed torque control is used for supporting (constrained) leg. For the free leg, the impedance control is used, where different values of impedance parameters are used depending on the gait phase of the biped robot. To reduce the magnitude of an impact and guarantee a stable footing when a foot contacts with the ground, this paper proposes to increase the damping of the leg drastically and to modify the reference trajectory of the leg. Computer simulations with a 3 -dof environment model for which a combination of a nonlinear and a linear compliant models is used, show that the proposed controller is superior to the computed-torque controllers in reducing impacts and stabilizing the footing.

A Study for the Prediction of a Tire Cornering Characteristics using a Finite Element Method (유한요소법을 이용한 타이어 코너링특성 예측에 관한 연구)

  • 김항우;조규종
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.1
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    • pp.151-162
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    • 1998
  • During a straight driving and cornering maneuver by a vehicle various forces and moments are exerted on the tire's footprint. A cornering properties, handling and stability performances of vehicle can be predicted by these forces and moments values. Therefore, on this study, a lateral force and a aligning torque are predicted by these forces and moments values. Therefore, on this study, a lateral force and a aligning torque are predicted using a finite element method. Contact area of the tire between bead and wheel are fixed to simplify of a finite element model. Lateral force is exerted on the rigid surface as a real load with Coulum friction after inflate and load vertically. Then, rotate the tire's axle to simulate a free rolling untill taken the equilibrium of a aligning torque. Also, experimental observations are made to test a reliability of a FE analysis conducted in this study. The finite element analysis said that good agreement was obtained with experimental results of these cornering properties, giving confidence within about one percent. So it os recommended that a finite element analysis can be used as a good tool to predicted the tire cornering properties.

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The Effects of Treadmill Aerobic Exercise Training on Isokinetic Muscle Strength in Students with Cerebral Palsy (트레드밀 유산소 운동이 뇌성마비학생의 등속성 근력에 미치는 영향)

  • Kang Soon-Hee
    • The Journal of Korean Physical Therapy
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    • v.16 no.4
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    • pp.1-10
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    • 2004
  • The purpose of this study was to investigate the effects of treadmill aerobic exercise training on isokinetic muscle strength in students with cerebral palsy. The subjects consisted of 9 female students with cerebral palsy between the ages of 10 to 22. The subjects performed treadmill aerobic exercise training with $0\%$ grade by free speed with three times a week for 20 minutes a session and 12 weeks. Concentric peak torque of knee flexors and knee extensors was measured before training and after training at $30^{\circ}/sec$ and $60^{\circ}/sec$ by isokinetic dynamometer. Paired t-test was used to assess changes in variables of isokinetic muscle strength. The results of analysis are as followings. 1) After training, concentric peak torque of the least affected knee flexors(p<.01) and the most affected knee flexors (p<.01) and concentric peak torque of the least affected knee extensors(p<.01) and the most affected knee extensors(p<.01) at $30^{\circ}/sec$ significantly increased. 2) After training, concentric peak torque of the least affected knee flexors(p<.05) and the most affected knee flexors(p<.01) and concentric peak torque of the least affected knee extensors(p<.05) and the most affected knee extensors(p<.01) at $60^{\circ}/sec$ significantly increased. These findings provide evidence that treadmill aerobic exercise training improves isokinetic muscle strength in students with cerebral palsy.

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Tuning-free Anti-windup Strategy for High Performance Induction Machine Drives (고성능 유도전동기 구동을 위한 자동 튜닝 Anti-windup 기법)

  • Seok Jul-Ki;Lee Dong-Choon
    • The Transactions of the Korean Institute of Power Electronics
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    • v.10 no.1
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    • pp.29-37
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    • 2005
  • This paper presents a tuning-free conditional integration anti-windup strategy for induction machine with Proportional-Integral(PI) type speed controller. The on/off condition of integral action is determined by the frequency domain analysis of machine torque command without a prior knowledge of set-point changes. There are no tuning parameters to be selected by users for anti-windup scheme. In addition, the dynamic performance of the proposed scheme assures a desired tracking response curve with minimal oscillation and settling time even in the change of operating conditions. This algorithm is useful in many high performance induction machine applications not to allow the oscillation and overshoot of speed/torque responses. The main idea can be extended to general applications such as chemical processes and industrial robots.

Chandler Wobble and Free Core Nutation: Theory and Features

  • Na, Sung-Ho;Roh, Kyoung-Min;Cho, Jungho;Yoo, Sung-Moon;Choi, Byungkyu;Yoon, Hasu
    • Journal of Astronomy and Space Sciences
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    • v.36 no.1
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    • pp.11-20
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    • 2019
  • Being a torque free motion of the rotating Earth, Chandler wobble is the major component in the Earth's polar motion with amplitude about 0.05-0.2 arcsec and period about 430-435 days. Free core nutation, also called nearly diurnal free wobble, exists due to the elliptical core-mantle boundary in the Earth and takes almost the whole part of un-modelled variation of the Earth's pole in the celestial sphere beside precession and nutation. We hereby present a brief summary of their theories and report their recent features acquired from updated datasets (EOP C04 and ECMWF) by using Fourier transform, modelling, and wavelet analysis. Our new findings include (1) period-instability of free core nutation between 420 and 450 days as well as its large amplitude-variation, (2) re-determined Chandler period and its quality factor, (3) fast decrease in Chandler amplitude after 2010.