• Fibers and Polymers
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• v.6 no.2
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• pp.146-150
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• 2005

In this paper, friction of air-jet textured yams is investigated. Using a friction measuring apparatus fabricated inhouse, dynamic friction forces of the yams under yarn-to-metal (YM) and yam-to-yam (YY) rubbing modes are measured. The influence of processing variables of air-jet texturing viz., overfeed, air pressure, dry/wet texturing and normal/core-and-effect texturing on dynamic friction is analysed. The results indicate that friction force increases with increasing rubbing speeds and yam input tension. YM dynamic friction decreases initially and then starts to increase at higher overfeeds. YY dynamic friction increases with increasing overfeed. YM dynamic friction decreases with an increase in air pressure while an opposite trend is observed for YY friction. Wet textured yams have higher friction than dry textured yams. Core wetted coreand-effect textured yams have higher friction than normal textured yams.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.4
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• pp.296-304
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• 2002

A position tracking control schemes on the precise mechanical system in presence of nonlinear dynamic friction is proposed. A nonlinear dynamic friction is regarded as the bristle friction model to compensate effects of friction. The conventional sliding mode controller often has been used as a non-model-based friction controller, but it has a poor tracking performance in high-precision position tracking application since it completely cannot compensate the friction effect below a certain precision level. Thus to improve the precise position tracking performance, we propose the sliding mode control method combined with the friction-model-based observer having tunable structure of the transient response. Then this control scheme has a good transient response as well as the high precise tracking performance compared with the conventional sliding mode control without observer and the control system with similar type of observer. The experiments on the bali-screw drive table with the nonlinear dynamic friction show the feasibility of the proposed control scheme.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.208.2-212
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• 1997

In a model based friction comensation for a frictional system,the performance of the system is inflenceed by the selection of the friction model. Especially, when a real plant have dynamic friction characteritics, the compensation of friction with a static friction model may deteriorate the perfomance. For the system we constlucted an adaptiv parameter estimation and friction compensation with a newly introduced dynamic friction model proposed by Canudas et.[1]. The model depicts varios frictional phenomena,such as Stibeck effect,frictional memory, Stick-slip motion. Parmeter identification algorithm are followed conventional RLSM adaptive rule. The stability for the closed system was proved by the Lyapunov stability. The result say that if a real system have dynamic friction property,the friction compensation with the dynamic friction model will improve the perfomance moreover static friction model based compensation may lead to the system unstable.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.51-61
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• 2002

A tracking control scheme on the XY ball-screw drive system in the presence of nonlinear dynamic friction is proposed. A nonlinear dynamic friction is regarded as the Lund-Grenoble friction model to compensate effects of friction. The conventional VSC method that often has been used as a non-model-based friction controller has poor tracking performance in high-precision position tracking application since it cannot compensate the friction effect below a certain precision level completely. Thus to improve the precise position tracking performance, we propose the integral type VSC method combined with the friction-model-based observer. Then this control scheme has the high precise tracking performance compared with the non-model-baked VSC method and the PID control method with a similar observer. This fact is shown through the experiment on the XY ball-screw drive system with the nonlinear dynamic friction.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.207-213
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• 2001

Shaking table tests to investigate the dynamic friction behavior of interfaces between dense dry granular soils and construction material(concrete) were performed and the results are reported. The results show the variation of dynamic interface friction coefficients between dense dry granular soils and construction material was small in the sliding velocity range employed in this study. It was also observed that dynamic interface friction coefficients decreased as mean grain sizes of granular soils increased. These coefficients were compared with the friction coefficients obtained from the peak internal friction angles of the same granular soils by plane strain compression tests.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1111-1117
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• 2008

During the dynamic analysis of a system, the Coulomb friction law is emploved to calculate the friction force. Since the static friction coefficient is only employed during the zero relative velocity, it is impractical to employ the coefficient during the dynamic analysis. To calculate the static friction force, therefore, some friction models have been developed. In this study, the integration stability and the accuracy of the models are investigated with some numerical examples. The effect of time step size during the numerical integration is also investigated. The numerical study shows that the friction model employed for most commercial codes is not as good as the one proposed in this study.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.202-208
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• 2014

Friction force on robot systems is highly nonlinear and especially disturbs precise control of the robots at low speed. This paper deals with the dynamic friction compensation problem of a well-known one-link benchmark robot system. We consider the LuGre model because the model can successfully represent dynamic characteristics and various effects of friction phenomenon. The proposed controller is constructed as two parts. An adaptive controller based on dual observers is used to estimate and compensate the dynamic friction. In order to attenuate the friction estimation error and other disturbances, PI observer is additionally designed. Through the computer simulations with the benchmark system, this paper first examines the effects of nonlinear dynamic friction on the control performance of the benchmark robot system. Next, it is shown that the control performance against the dynamic friction is improved by using the proposed controller.

• Tribology and Lubricants
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• v.14 no.3
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• pp.65-73
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• 1998

A dynamic analysis and friction loss of non-variable swash plate compressor are studied theoretically. Rotating swash plate and reciprocating pistons are modelled kinematically, and forces and torques acting on rotor-bearing system are analyzed. Then, friction losses on 4 roller bearings, 10 sliding parts between swash plate and shoes, and 10 lubricating surfaces between cylinders and pistons are calculated. On each frictional element of sliding surfaces and roller bearings, the same friction loss is obtained, respectively.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.11
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• pp.904-913
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• 2002

In this study, a dynamic analysis of the reciprocating compression mechanism considering viscous friction force of a piston used in small refrigeration compressors is performed. The length of cylinder in this class of compressors is shortening to diminish the frictional losses of the piston-cylinder system. So, the contacting length between piston and cylinder liner is in variable with the rotating crank angle around the BDC of the reciprocating piston. In the problem formulation of the compression mechanism dynamics, the change in bearing length of the piston and all corresponding viscous forces and moments are considered in order to determine the trajectories of piston and crankshaft. The piston orbits for viscous friction model and Coulomb friction model were used to compare the effect of the friction forces of piston on the dynamic trajectories of piston. To investigate the effect of friction force acting on the piston for the dynamic characteristics of crankshaft, comparison of the crankshaft loci is given in both viscous model and Coulomb model. Results show that the viscous friction force of piston must be considered in calculating for the accurate dynamic characteristics of the reciprocating compression mechanism.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.12
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• pp.89-99
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• 2008

In this paper, the position tracking control problem of the servo system with nonlinear dynamic friction is issued. The nonlinear dynamic friction contains a directly immeasurable friction state variable and the uncertainty caused by incomplete parameter modeling and its variations. In order to provide the efficient solution to these control problems, we propose the composite control scheme, which consists of the robust friction state observer, the FNN approximator and the approximation error estimator with sliding mode control. In first, the sliding mode controller and the robust friction state observer is designed to estimate the unknown internal state of the LuGre friction model. Next, the FNN estimator is adopted to approximate the unknown lumped friction uncertainty. Finally, the adaptive approximation error estimator is designed to compensate the approximation error of the FNN estimator. Some simulations and experiments on the servo system assembled with ball-screw and DC servo motor are presented. Results show the remarkable performance of the proposed control scheme. The robust friction state observer can successfully identify immeasurable friction state and the FNN estimator and adaptive approximation error estimator give the robustness to the proposed control scheme against the uncertainty of the friction parameters.