• Title/Summary/Keyword: Virtual Damper

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Control simulation of MR damper for a cruise bus including the virtual dynamic damper (가상 동흡진기를 고려한 우등버스용 MR댐퍼의 제어 시뮬레이션)

  • Park, S.J.;Sohn, J.H.
    • Journal of Power System Engineering
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    • v.15 no.2
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    • pp.19-24
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    • 2011
  • In this study, a control method of MR(magneto-rheological) damper for a cruise bus is investigated. A virtual dynamic damper and a sky-hook algorithm are employed to control the damping characteristics of MR damper. Coefficients for a virtual dynamic damper are determined through the parameter identification. A quarter car model of a cruise bus is established by using ADAMS/Car program for the computer simulation. Sine wave excitation and random excitation are used to compare the controlled MR damper with the passive damper. From the simulation results, the performance of MR damper with a virtual dynamic damper is better than that of the passive damper.

Effects of a First-order-hold Method and a Virtual Damper on the Stability Boundary of a Virtual Spring (일차홀드 방식과 가상 댐퍼가 가상 스프링의 안정성 영역에 미치는 영향)

  • Lee, Kyungno
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.6
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    • pp.396-401
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    • 2019
  • A virtual rigid is modeled as the parallel structure of a virtual spring and a virtual damper. The reflective force from the virtual model is designed to be as large as possible to improve the realism of the virtual environment while maintaining the stable interaction. So, it is important to analyze the stability boundary of the virtual spring and damper. In the previous researches, the stability boundary is analyzed based on the zero-order-hold (ZOH) method, but it is analyzed based on the first-order-hold (FOH) method and the virtual damper in the paper. The boundary value of the stable virtual damper is inverse proportional to the sampling time and the maximum value of stable virtual stiffness is inverse proportional to the square of the sampling time. And the maximum value in the FOH method is increased to 110% of the value in the ZOH method. If the virtual damper is smaller than about 50% of the boundary value of the virtual damper in the FOH method, the stable virtual stiffness in the FOH method is several times larger than that in the ZOH method.

Effect of the sampling time of high-frequency ZOH and a physical damper on stable haptic interaction (고주파 영차홀드의 샘플링 주기와 물리적 댐퍼가 안정적인 햅틱 상호작용에 미치는 영향)

  • Lee, Kyungno
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.2
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    • pp.649-654
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    • 2019
  • Stable haptic interaction with virtual environments is essential not only for the safety of the user but also for improving the immersion of the user. If the coefficient of a virtual spring is increased, the system becomes unstable. Therefore, the coefficient of the virtual spring is limited. The haptic system with the high-frequency zero-order-hold (HF-ZOH) is proposed to enhance the stability margin of a virtual spring. In this paper, the relationship among the sampling period of HF-ZOH, the coefficient of the physical damper, and the maximum stable margin of the virtual spring is analyzed. The lager the coefficient of the physical damper is, the shorter the sampling period of the HF-ZOH is, the larger the stable region of the virtual spring becomes. If the ratio N is larger than 40, the stable region of the proposed method is about three times to eight times that of the previous method, according to the coefficient of the physical damper. Hence the method enables to improve the user's realism in virtual environments.

A Real-Time Collision-Free Trajectory Planning and Control for a Car-Like Mobile Robot (이동 로봇을 위한 실시간 충돌 회피 궤적 계획과 제어)

  • 이수영;이석한;홍예선
    • Journal of Institute of Control, Robotics and Systems
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    • v.5 no.1
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    • pp.105-114
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    • 1999
  • By using the conceptual impedance and the elasticity of a serial chain of spring-damper system, a real-time collision-free trajectory generation algorithm is proposed. The reference points on a trajectory connected by the spring-damper system have a mechanism for self-Position adjustment to avoid a collision by the impedance, and the local adjustment of each reference point is propagated through the elasticity to a real robot at the end of the spring-damper system. As a result, the overall trajectory consisting of the reference points becomes free of collision with environmental obstacles and efficient having the shortest distance as possible. In this process, the reference points connected by the spring-damper system take role of virtual robot as global guidance for a real robot, and a cooperative optimization is carried out by the system of virtual robots. A control algorithm is proposed to implement the impedance for a car-like mobile robot.

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Modeling of progressive collapse of a multi-storey structure using a spring-mass-damper system

  • Yuan, Weifeng;Tan, Kang Hai
    • Structural Engineering and Mechanics
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    • v.37 no.1
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    • pp.79-93
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    • 2011
  • A simple mechanical model is proposed to demonstrate qualitatively the pancake progressive collapse of multi-storey structures. The impact between two collapsed storeys is simulated using a simple algorithm that builds on virtual mass-spring-damper system. To analyze various collapse modes, columns and beams are considered separately. Parametric studies show that the process of progressive collapse involves a large number of complex mechanisms. However, the proposed model provides a simple numerical tool to assess the overall behavior of collapse arising from a few initiating causes. Unique features, such as beam-to-beam connection failure criterion, and beam-to-column connection failure criterion are incorporated into the program. Besides, the criterion of local failure of structural members can also be easily incorporated into the proposed model.

Effects of the time delay on the stability of a virtual wall model with a first-order-hold method (시간지연에 의한 일차홀드 방식을 포함하는 가상벽 모델의 안정성 영향 분석)

  • Lee, Kyungno
    • Journal of Institute of Convergence Technology
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    • v.4 no.2
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    • pp.17-21
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    • 2014
  • This paper presents the effects of the time delay on the stability of the haptic system that includes a virtual wall and a first-order-hold method. The model of a haptic system includes a haptic device model with a mass and a damper, a virtual wall model, a first-order-hold model and a time delay model. In this paper, the time delay is considered as the computational time delay that is assumed to be as much as the sampling time. As the time delay increases, the maximal available stiffness of a virtual wall model is reduced reversely. The relation among the time delay and the maximum available stiffness, the mass and the damper of the haptic device are analyzed using the MATLAB simulation.

Stability Analysis of a Haptic System with a First-Order-Hold Method (일차 홀드 방식의 반력 구현 시스템에 대한 안정성 해석)

  • Lee, Kyungno
    • Journal of Institute of Control, Robotics and Systems
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    • v.20 no.4
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    • pp.389-394
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    • 2014
  • This paper presents the effect of a reflective force computed from a first-order-hold method on the stability of a haptic system. A haptic system is composed of a haptic device with a mass and a damper, a virtual spring, a sampler and a sample-and-hold. The boundary condition of the maximum virtual stiffness is analytically derived by using the Routh-Hurwitz criterion and the condition shows that the maximum virtual stiffness is proportional to the square root of the mass and the damper of a haptic device and also is inversely proportional to the sampling time to the power of three over two. The effectiveness of the derived condition is evaluated by the simulation. When the reflective forces are computed by using the first-order-hold method, the maximum available stiffness to guarantee the stability is increased several hundred times as large as when the zero-order-hold method is applied.

Hyper-elastic Model Haptic Feedback Using Finite Element Analysis (유한요소 해석을 이용한 초탄성체 햅틱 피드백 연구)

  • Park, Seunghyun;Kim, Jinhyun
    • Journal of Sensor Science and Technology
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    • v.31 no.4
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    • pp.260-265
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    • 2022
  • In this study, we establish hyper-elastic haptic feedback in a virtual environment using finite element analysis techniques and develop a Force Torque (FT) sensor utilization method for application in tele-operation environments. In general, regarding haptic feedback data, in a tele-operation environment, the user is provided with feedback according to the measured force data when the model is inserted through an FT sensor. Conversely, in a virtual environment, the press-fitting model can be expressed through the spring-damper system rather than an FT sensor to provide feedback. However, unlike rigid and the elastic bodies, the hyper-elastic body represented by a spring-damper system in a virtual environment is a simple impedance model using stiffness and damping coefficients; it is limited in terms of providing actual feedback. Thus, in this study, haptic feedback was implemented using the data obtained from POD-RBF analysis results during hyper-elastic press-fitting experiments. The haptic feedback mechanism developed in this study was verified by comparing the FT sensor feedback data measured and calculated through hyper-elastic press-fitting experiments with spring-damper feedback data. Subsequently, the POD-RBF analysis feedback was compared and evaluated against the feedback mechanism of each environment through the test subject, and the similarities between the POD-RBF analysis feedback and FT sensor data feedback were verified.

Stability of Haptic System with consideration for Sample-and-Hold Methods and Properties of Haptic Device (샘플-홀드 방식과 햅틱 장치 물성치에 따른 햅틱 시스템의 안정성 분석)

  • Lee, Kyungno
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.11
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    • pp.5338-5343
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    • 2013
  • In a haptic system, a virtual wall is modeled as a virtual spring. The larger the stiffness of the virtual spring is, the more improved the reality of the virtual wall is, but the more unstable the haptic system becomes. This paper shows how to increase the stiffness of the virtual spring while the stability of the haptic system is guaranteed and shows the effects of a mass (Md) and a damper (Bd) of a haptic device on the stability when first-order hold method is applied and a virtual wall is modeled as a virtual spring (Kw). The simulation results show the boundary of the virtual spring is proportional to the square root of the mass (Md) and the damper (Bd) while maintaining the stability. The relation among the virtual spring (Kw), the mass (Md) and the damper (Bd) of the haptic device, and sampling time (T) is inferred as $K_w{\leq}{1.611M_d}^{0.50}{B_d}^{0.50}T^{-1.51}$, by using the simulation results. The maximum available stiffness of the virtual spring in first-order hold method is larger than in zero-order hold method. So the reality of the virtual wall can be improved.

A Real-Time Collision-Free Trajectory Planning and Control for a Car-Like Mobile Robot (모바일 로봇의 충돌회피 알고리즘 개발)

  • Nguyen, Huu-Cong;Kim, Gi-Bok;Jo, Sang-young
    • Journal of the Korean Society of Industry Convergence
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    • v.18 no.2
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    • pp.99-109
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    • 2015
  • This study proposes a new approach to analyze the impedance and the elasticity of a serial chain of spring-damper system, areal-time collision-free trajectory generation algorithm is proposed. The reference points on a trajectory connected by the spring-damper system have a mechanism for self-position adjustment to solve a collision problem by the impedance, and the local adjustment of each reference point is propagated through the elasticity to a real robot at the end of the spring-damper system. As a result, the overall trajectory consisting of the reference points becomes free of collision with environmental obstacles and efficient having the shortest distance as possible. In this process,, the reference points connected by the spring-damper system take role of virtual robot as global guidance for a real robot, and a cooperative is carried out by the system of robots. A control technology is proposed to implement for mobile robot.