• Nuclear Engineering and Technology
• /
• v.25 no.2
• /
• pp.233-236
• /
• 1993

For one-dimensional two-phase flow without phase change and without axially-temporally rapid change of pressure, the interrelationship between the drift-flux model and the two-fluid model is studied. It is derived on the basis of the fact that the vapor conservation equation is related to the momentum equation by the drift flux. Starting from the two-fluid model, we obtain the interfacial friction expressed in terms of drift-flux parameter. Also, by deriving the void propagation equation, the drift-flux is shown to have jnterrelationship with forces in the two-fluid model.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.2397-2401
• /
• 2005

It is well understood that force reflecting coupled with visual display can be an important two-way communication channel in human-computer interaction. In this work, important components for a high-fidelity system bandwidth are force reflecting device and that all the computations including contact determination and response computation have to be performed in less than a millisecond. This paper describes a force-reflecting device and an embedded controller. The realized force-reflecting device is based on a novel serial type mechanical structure, and features compactness, high sustained output force capability, low friction, zero backlash, and enough workspace. The embedded controller reduces software computational load via main processor and simplifies hardware strictures by the time-division control. The device is integrated with existing dynamic simulation algorithms running separate workstation, so that objects can be manipulated in real time and the corresponding forces felt back by the operator.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10a
• /
• pp.81-86
• /
• 2000

In recent modern protective systems have been introduced to reduce the vulnerability of bridges to seismic events. These protective systems include base isolation devices of different types, damping devices and active control devices. The objective of this study is to analytically evaluate the efficiency of a seismic retrofit scheme using base isolation systems, such as lead rubber bearings and sliding isolators. In this study, a triaxial model was used, which is capable of accurately developing the behavior of sliding isolators including the influence of the changing vertical force and velocity on the friction coefficients. Seismic response analyses of the bridge before and after retrofit were carried out by using a three-dimensional nonlinear seismic analysis program, IDARC-BRIDGE. To evaluate the efficiency of a retrofit scheme using triaxial isolators, a comparative study of performances of above two base isolation systems was conducted, and the numerical results show that the triaxial isolation solution can effectively reduce the sheat forces at the piers for the vertical ground motion.

• 제어로봇시스템학회:학술대회논문집
• /
• 2002.10a
• /
• pp.90.5-90
• /
• 2002

In this research, we are trying to develop an automatic sorting system, which is mostly affected by frictional forces between a veneer and plank. So we will make a suitable dynamic model and mechanism to control the velocity feedback. We will suggest stick-slip motion model which can predict the stability behavior of this system. The control system has a feedback loop, in which the following operations are included. A kind of sensor can get the velocity of the mass to adhesive veneer. The output of result signal should be passed to a filter, then to a phase shifter, which applies an adjustable phase-shift, to a variable-gain amplifier. A shaker will be attached to the mass, which ex...

• 제어로봇시스템학회:학술대회논문집
• /
• 1988.10b
• /
• pp.964-968
• /
• 1988

In mechanical systems in which the dynamics of armatures is dominated by electrostatic forces, motions will generally be unstable. This paper deals with the control problems of this kind of micro electrostatic device systems. In these systems, the mass of micro mechanical parts is so small that the inertia term in the equation of motion is negligible. However, nonlinear terms, such as friction and driving force, become dominant. The purpose of this paper is to realize the stable motion without delay and, overshoot etc. A micro-mechanical system used in this paper consists of a plane wafer with striped electrodes converted with an insulation layer and thin cylindrical roller is placed over on it. The performance of motions is confirmed by some simulations.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.5
• /
• pp.110-116
• /
• 2011

Water on a road surface can lower the coefficient of friction of vehicle tires and it involves lots of risks. One way to prevent water from staying is to cut many "rain grooves" into the edges of the pavement parallel. Such grooves, however, can exert unwanted side forces, particularly on passenger tires, which cause "Groove Wander" making the drivers uncomfortable. The "Groove Wander" is somewhat related to vehicle geometry, but is more strongly related to interaction between road grooves and tire tread's longitudinal grooves. This thesis tries to examine principles to estimate "Groove Wandering" effect focusing on the design of longitudinal groove. Additionally, it studied how to reduce pipe resonance longitudinal grooves form in the contact patch.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.10a
• /
• pp.77-82
• /
• 2003

In end milling process, undeformed chip thickness and cutting force vary periodically with phase change of the tool. Recently, a model has been proposed to simulate the shear and friction characteristics of an up-end milling process in terms of the equivalent oblique cutting to this. In the current study, the varying undeformed chip thickness and the cutting forces in a down-end milling process have been replaced with the equivalent ones of oblique cutting. And, the down-end milling characteristics of SM45C has been compared with that of the up-end milling previously presented with different helix angles.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.63-68
• /
• 1996

In this study, the effect of tool rake angles and the change of cutting conditions on specific cutting pressure in face milling is investigated. The cutting force in face milling is predicted from the double cutting edge model in 3-dimensional cutting. Conventional specific cutting pressure model is modified by considering the variation of tool rake angles. Effectiveness of the modified cutting force model is verified by the experiments using special face milling cutters with different cutter pockets and various rake angles. From the comparison of the pressented model and the specific cutting pressure, it is shown that the axial force can be predicted by the tangential and redial forces without the knowledge of friction angle and shear angle. Also, the relation between specific cutting pressure and cutting cindition including feedrate, cutting velocity and depth of cut is studied.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.993-996
• /
• 2000

A brushless linear motor is suitable for a high-accuracy servo mechanism. It is also suitable for operation with higher speed and precision. Since it does not involve some sort of mechanical coupling, linear driving force can be applied directly. Basic models including magetomotive force and electromotive forces are introduced and simplified. Both conventional PID and fuzzy controllers are implemented and performance results using those controllers are compared. Along with better simulated performance observed using fuzzy controller, further fabrication is to be included with various empirical results. Several system operational characteristics have been observed. Typical nonlinearities as friction, cogging and torque or thrust ripple that might deteriorate system performance would be tackled using presumably effective method such as neural network based learning controller.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.713-718
• /
• 2003

Decubitus ulcer is a pressure-induced ulceration of the skin occurring in persons confined to bed for long periods of time. In order to prevent decubitus ulcer, the medical bed mechanism to minimize pressure, friction, and shear forces acting between bed and patient had been developed. Air mattress also can be effective for reducing pressure over bony prominence. In this study, motion analysis was performed to examine whether this bed mechanism functioned properly in case of using air mattress, which was much thicker than common hospital mattress. We found that the patient on the air mattress above the medical bed for preventing decubitus ulcer slipped upward and downward excessively as the general motored-bed. New bed mechanisms were synthesized kinematically using simple 4-bar and 6-bar linkages so as to reduce sliding between the bed and the patient on the air mattress for preventing decubitus ulcer.