• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.23-30
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• 1996

The purpose of this study was to investigate changes in thewall thickness of tube sinking and working forces by the upper bound method and ABAQUS code. The independent variables were : Workpiece material, original wall thickness of tube, die angle, friction, and diameter reduction. The results indicated that of these five variables were a factor in wall-thickness increase and working forces. Three variables, a inner tube wall angle and two angles of the velocity discontinuous surfaces, are optimized in this proposed velocity field by the upper bound method. In this method, we can estimate the working forces and final tube thicknesses whcih are similar to acturla forming process. Optimized process variables which are obtained by upper bound method are used in ABAQUS pre-model . In ABAQUS analysis, the stress and the strain contours which are considered to be heat generation occured by the friction during forming process are observed.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.799-804
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• 2003

Friction phenomenon can be described as two parts which are pre-sliding and sliding regions. In motion of the sliding region, friction forces depend on the velocity of the system and are known as Coulomb, stick-slip, stribeck effect and viscous friction. The pre-sliding region, which is before breakaway, depends on the position of the system. The motion of friction in the sliding region can be described as the LuGre model. But the pre-sliding motion of friction, which has hysteresis characteristics in general, is not known widely. Therefore, an improved friction model, which can describe the motion of friction in the pre-sliding region, is proposed in this paper. And simulation and experimental results show the effectiveness of the proposed friction model for precise tracking control systems.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.183.2-183.2
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• 2005

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.77-83
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• 2003

This paper deals with a position control problem of a hydraulic proportional position control system using a nonlinear friction compensation control. As nonlinear friction, stiction and coulomb friction forces are considered and modeled as deadzone and external disturbance respectively. In order to compensate this nonlinearities, we designed the controller which is the adaptive friction compensator using discrete time Model Reference Adaptive Control method in this paper. Digital Signal Processing board is employed for data acquisition and manipulation. The experimental results show that response is slow and steady-state error cannot be compensated properly without friction compensation but this compensator is effective to obtain fast response and good steady-state response.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.422-422
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• 2000

Parallel manipulators have been used to a variety of applications, including the motion simulators and mechanism for precise machining. A Stewart-Gough type parallel manipulator is composed of six linear joints which have wider contact areas than revolute ones, so linear joints are more affected by frictional force. First, the reference trajectories are computed from the model of the parallel manipulator assuming that it is subject to only the gravitational force and no friction exists. In the actual operation where friction exists, the control inputs, which correspond to the friction forces, are obtained by forcing the actual joint variables to follow these trojectories by proper control. It is shown that control performance can be improved when the friction compensation based on this information is added to the controller for position control of the moving plate of a parallel manipulator.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.3
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• pp.251-259
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• 2005

A discrete time model reference adaptive control has been applied in order to compensate the nonlinear friction characteristics in a hydraulic proportional position control system. As nonlinear friction, static and coulomb friction forces are considered and modeled as dead zone and external disturbance respectively. The model reference adaptive control system consists of a cascade combination of the dead zone. external disturbance and linear dynamic block. For adaptive control experiment. the DSP(Digital Signal Processor) board has been interfaced the hydraulic proportional position control system. The experimental results show that the MRAC(Model Reference Adaptive Control) for compensation of static and coulomb friction are very effective.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.585-590
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• 2017

Vehicle behavior is determined by forces and a torques generated at the ground contact surface of the tire. Various tire models are used to calculate the forces and torques acting on the tire. The brush model calculates the forces and torques with fewer coefficients than other tire models. However, owing to fewer degrees of freedom in calculating the forces, this model has limitations in precisely expressing measured data. In this study, this problem was addressed by adding the least parameters to the friction coefficient and tire properties of the brush model, and the proposed model was validated.

• Journal of Ocean Engineering and Technology
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• v.11 no.1
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• pp.65-73
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• 1997

The floating body discussed in this study is a 2-D rectangular floating unit supported by four vertical piles at its corners. Structures of this type are frequently seen as floating piers for the crafts in a small harbour. The movement in some modes of motion of such a flating body is fully or partially restrincted by the piles. The authors(Kim et al. 1994) carried out a series of model tests on its wave control function, its motion and the loads on piles. The experimental results showed that a certain degree of intial constriction force which clamps the floating unit in the horizontal direction can effectively reduce the body motion and wave energy without increasing mooring forces. This may be due to the friction forces occuring between the piles and the rollers installed in the mooring equipments on the floating unit. In this paper, we develop a numerical model for the prediction of wave transformation and floating body motions, where the friction force is idealized as the Coulomb friction and linearized into a damping force using the equivalent damping cofficient. This linearization is verified by comparing the results of motions between the linear and nonlinear analysis of the ezuations of motion. We further compare the caculation results by the linear model with the experimental results and discuss the effect of the friction force or the constriction force on body motions and wave energy dissipation.

• Proceedings of the Safety Management and Science Conference
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• 2002.05a
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• pp.207-214
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• 2002

This paper presents some physical evidences indicating that reduced friction occurs in an cryogenic machining process, in which LN2 is applied selectively in well-controlled jets to the selected cutting zone. In machining tests, cryogenic machining reduced the force component in the feed direction, indicating that the chip slides on the tool rake face with lower friction. This study also found that the effectiveness of LN2 lubrication depends on the approach how LN2 is applied regarding cutting forces related.

• The Korean Journal of Pain
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• v.36 no.2
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• pp.208-215
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• 2023

Background: To evaluate the feasibility, inter-reader reliability, and intra-reader reliability for various morphological features reported to be related to iliotibial band friction syndrome (ITBFS) on knee magnetic resonance imaging (MRI). Methods: A total of 145 patients with a clinical diagnosis and knee MRI findings consistent with ITBFS were included in the "study group" and 232 patients without knee pathology on both physical examination and MRI were included in the "control group". Various morphologic features on knee MRI were assessed including the patella shape, patella height, lateral epicondyle anterior-posterior (AP) width, lateral epicondyle height, ITB diameter (ITB-d), and ITB area (ITB-a). Results: Patients in the study group had significantly higher lateral epicondyle height (13.9 mm vs. 12.92 mm, P = 0.003), ITB-d (2.9 mm vs. 2.0 mm, P = 0.022), and ITB-a (38.5 mm² vs. 23.8 mm², P < 0.001) than the control group. ITB-a showed higher area under the curve index (0.849 with 74.1% sensitivity and 72.4% specificity at a 30.3 mm² cutoff) than ITB-d (0.710 with 70.8% sensitivity and 61.2% specificity at 2.4 mm cutoff) and lateral epicondyle height (0.776 with 72.4% sensitivity and 67.8% specificity at 13.4 mm cutoff). However, only the inter-reader agreement for ITB-a (intraclass correlation coefficient = 0.65) was moderate, while the agreements for other morphologic features were good or excellent. Conclusions: Lateral epicondyle height seems to be a reliable and feasible morphologic feature for diagnosis of ITBFS.