• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.1673-1678
• /
• 2005

This paper addresses both theoretical and experimental studies of the stability of haptic interfaces during the simulation of virtual Coulomb friction. The first objective of this paper is to present an analysis of how friction affects stability in terms of the describing function method and the absolute stability theory. Two different feedback methods are introduced and are used to evaluate the analysis: an active force feedback, using a motor, and a passive force feedback, using controllable brake. The second objective of this paper is to present a comparison of the theoretical and experimental results. The results indicate that the sustained oscillations due to the limit cycle occur when simulating friction with an active force feedback. In contrast, a passive force feedback can simulate virtual friction without the occurrence of instability. In conclusion, a hybrid active/passive force feedback is proposed to simulate a highly realistic friction display.

• Earthquakes and Structures
• /
• v.3 no.6
• /
• pp.805-820
• /
• 2012

An enhanced and efficient methodology is proposed for evaluating the robustness of an uncertain structure with passive dampers. Although the structural performance for seismic loads is an important design criterion in earthquake-prone countries, the structural parameters such as storey stiffnesses and damping coefficients of passive dampers are uncertain due to various factors or sources, e.g. initial manufacturing errors, material deterioration, temperature dependence. The concept of robust building design under such uncertain structural-parameter environment may be one of the most challenging issues to be tackled recently. By applying the proposed method of interval analysis and robustness evaluation for predicting the response variability accurately, the robustness of a passively controlled structure can be evaluated efficiently in terms of the so-called robustness function. An application is presented of the robustness function to the design and evaluation of passive damper systems.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.11 s.242
• /
• pp.1534-1541
• /
• 2005

Unlike industrial manipulators, the manipulators mounted on service robots are interacting with humans in various aspects. Therefore, safety has been one of the most important design issues. Many compliant robot arms have been introduced for safety. It is known that passive compliance method has faster response and higher reliability than active ones. In this paper, a new safety mechanism based on passive compliance is proposed. Passive mechanical elements, specifically transmission angle of the 4-bar linkage, springs and shock absorbing modules are incorporated into this safety mechanism. This mechanism works only when the robot arm exerts contact force much more than the human pain tolerance. Validity of this mechanism is verified by simulations and experiments. It is shown that the manipulator using this mechanism provides higher performance and safety than those using other passive compliance mechanisms or active methods.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.5 s.236
• /
• pp.707-715
• /
• 2005

In this work, Scalar Passive code in Lattice Boltzmann Method is employed to simulate two-phase flow of low Reynolds number in a micro-channel. The mixing characteristics in a micro-channel is a function of Peclet number. The mixing length increases with the Peclet number. It is found that with the inclusion of static elements at the channel, rapid mixing of two liquids can be achieved, as shown by the results of computer simulations. The enhancement in mixing performance is thought to be caused by the generation of eddies and by lateral velocity component when the mixture flows past static elements. The results indicate that the size of static element has more effect on the mixing than the number of static element.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.12
• /
• pp.2319-2323
• /
• 2010

The existing contact-type bearings using rolling or sliding require continuous maintenance due to abrasion caused by friction and are not suitable for high-speed rotation and slimming. A magnetic bearing without contact can overcome such problems but the performance depends on the allocation of magnets and the structure of bearings. This paper proposes a method designing parameters of a passive magnetic bearing to improve levitation force. The proposed method employs Halbach array as the allocation of magnets, uses particle swam optimization to determine the structure of bearings. The numerical experiment shows that the levitation force is improved by the proposed method compared with the existing one using finite element analysis.

• Journal of Korean Society for Atmospheric Environment
• /
• v.29 no.2
• /
• pp.217-227
• /
• 2013

Passive air samplers (PAS) have been developed since the early 2000s and widely used for the atmospheric monitoring of persistent organic pollutants (POPs). PAS are useful especially for the investigation of source-receptor relationship of POPs because they provide higher spatial resolution data. In Korea, however, only a few research groups have conducted POPs monitoring using PAS. One of the reasons for the limited application of PAS might be due to a complicated calculation method for air concentration. In this study, therefore, we introduced the principle of polyurethane foam (PUF)-PAS, which has been most widely used in the world, and provided an example of the calculation of air concentration of polycyclic aromatic hydrocarbons (PAHs). As all data tables and equations for this calculation were provided, this method can be used for the conversion of the amount of POPs (ng) in a PUF disk to air concentration ($ng/m^3$).

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.3
• /
• pp.466-471
• /
• 2012

In this paper, we consider the problem of a robust passive filtering with low-order for discrete-time singular systems with polytopic uncertainties. A BRL(bounded real lemma) for robust passivity with a dissipativity of discrete-time uncertain singular systems is derived. A low-order robust passive filter design method is proposed by new reduced-order method and LMI(linear matrix inequality) technique on the basis of the obtained BRL. Finally, illustrative examples are presented to show the applicability of the proposed method.

• Smart Structures and Systems
• /
• v.19 no.4
• /
• pp.351-360
• /
• 2017

Protection of structures against natural hazards such as earthquakes has always been a major concern. Semi-active control combines the reliability of passive control and versatility and adaptability of active control. So it has recently become a preferred control method. This paper proposes an algorithm based on Uniform Deformation Theory to mitigate vulnerable buildings using magneto-rheological (MR) damper. Due to the successful performance of fuzzy logic in control of systems and its simplicity and intrinsically robustness, it is used here to regulate MR dampers. The particle swarm optimization (PSO) algorithm is also used as an adaptive method to develop a fuzzy control algorithm that is able to create uniform inter-story drifts. Results show that the proposed algorithm exhibited a desirable performance in reducing both linear and nonlinear seismic responses of structures. Performance of the presented method is indicated in compare with passive-on and passive-off control algorithms.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.2
• /
• pp.115-122
• /
• 2002

In this paper, we proposed a new technique to be compatible the passive with active ETC system. Now the TTA is making a Standard of the Active DSRC System. So It is necessary to be compatible the developed and running passive ETC system with the developing active ETC system. So we proposed the direct conversion method without performance a decreasing of passive DSRC system using a similar bandwidth of the active ETC system. Simulations carried out and the results show the difference between the conventional and proposed method.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.23 no.6
• /
• pp.440-445
• /
• 2018

This study proposes a novel control and design method for a grid-connected inverter with an LCL filter without damping. The current resonance phenomenon must be considered when designing the grid-connected inverter system with an LCL filter. Passive or active damping is used in the inverter system to reduce the resonant current. However, passive damping reduces the efficiency of the system, and active damping methods are complex. If the resonant frequency is in a specific region, then the system will be unstable. This study examines the process of stabilizing the entire region without resonant damping. The validity of the proposed method is verified through simulation and experimentation.