• Tribology and Lubricants
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• v.8 no.2
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• pp.20-25
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• 1992

Friction and wear behavior of hot isostatic pressed $Al_2O_3-TiC$ was experimentally examined. Pin-on-disk type friction and wear apparatus was designed and manufactured for the experiment. The experiments were conducted under unlubricated sliding motion in both low and high humidity for three kinds of sliding speed. $Al_2O_3-TiC$ and bearing steel were used as counterface materials. Friction coefficient, wear rate, and surface roughness were measured. Wear surface and wear debris were observed through optical microscope and SEM and analyzed by EDAX. The results showed that the counterface materials, the sliding speed, and the moisture at the sliding surface have significant influence on the friction coefficient and wear rate of $Al_2O_3-TiC$.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.4
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• pp.126-135
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• 1992

Up to now, there has been a lot of researches on the sliding mode control which has the insensitive characteristics to the variations of plant parameters, nonlinearities and external disturbances. One difficulty in applying the sliding mode control is the need for the knowledge of the full-state vector. The use of state observer is a natural step towards the relaxation of this condition. However, the exact plant-modeling is assumed to be known. Recently, there has been a remarkable advance in the microprocessor and one can construct the controller which could not realize due to hardware restriction in the past. Therefore in this paper, the PID sliding mode controller which has only one output feedback signal is suggested by means of microprocessor and the performance of electro-hydraulic servosystem compensated with this controller is proved.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.165-171
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• 2002

The conventional sliding mode control(SMC) technique requires a priori knowledge of the upperbounds of disturbances or/and modeling uncertainties to assure robustness. This, however, may not to be easy to obtain in practical situation. This paper presents a new methodology, sliding mode control with disturbance estimator(SMCDE), which offers a robust control performance without a priori knowledge about the disturbance. The proposed technique is featured by an average value of the imposed disturbance over a certain period. A nonlinear spring-mass-damper system is adopted as an illustrative example, and a comparative work between the conventional technique and the present one is undertaken.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.4
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• pp.228-234
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• 2005

In this paper, we proposed a self tuning adaptive fuzzy sliding control algorithms using gadient descent method to reduce chattering phenomenon which is viewed in variable control system. In design of FLC, fuzzy control rules are obtained from expert's experience and intuition and it is very difficult to obtain them. We proposed an adaptive algorithm which is automatically updated by consequence part parameter of control rules in order to reduce chattering phenomenon and simultaneously to satisfy the sliding mode condition. The proposed algorithm has the characteristics which are viewed in conventional VSC, e.g. insensitivity to a class of disturbance, parameter variations and uncertainties in the sliding mode. To demonstrate its performance, the proposed control algorithm is applied to an inverted pendulum system. The results show that both alleviation of chattering and performance are achieved.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.1
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• pp.65-75
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• 1996

A pilot plant, which is simplified the hot water heating control system of a large scale residential building, is used to investigate the effects of control methods and operating conditions on the system performance and to compare control characteristics. Digital variable structure controller(DVSC) and digital PI controller are implemented to control the speed of the circulating pump for the pilot plant using PC. For the DVSC, a control algorithm is suggested, which using a nonlinear sliding surface and a PID sliding surface outside and inside of output error boundary layer, respectively. Smith predictor algorithm is used for the compensation of long dead time. The suggested DVSC yields improved control performance compared with existing DVSC using linear sliding surface only. the system responses with the suggested DVSC shows good responses without overshoot for various operating conditions and robust under external disturbances compared with digital PI controller.

• Journal of Power Electronics
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• v.6 no.2
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• pp.172-177
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• 2006

This paper presents the sliding mode observer of an induction motor for the fuel cell electric vehicles. The exact rotor flux estimation of the induction motor is important for achieving the best performance from the fuel cell electric vehicle system. However, the flux estimator of the induction motor control is highly sensitive to the voltage sensor output characteristics and system parameter variation influenced by external factors. In order to eliminate these problems, this paper investigates the electric vehicle performance due to parameter variation of the induction motor. A new method to estimate the fuel cell electric vehicle system is proposed based on the sliding mode observer.

• Journal of Power Electronics
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• v.13 no.6
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• pp.1000-1007
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• 2013

This paper proposes a sliding-mode-based direct power control (DPC) method in a three-phase boost rectifier without the use of a voltage sensor. This sliding-mode-based DPC is used to improve transient-state response characteristics. This DPC can eliminate voltage sensors by calculating a voltage using a sensorless method, thus considerably reducing cost. This DPC first presents an effective algorithm that does not significantly affect the previous performance and does not need a voltage sensor. Thereafter, the effectiveness of the algorithm is verified by simulations and experiments.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.80-88
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• 2000

The plasma spray technics has known as one of the surface modification methods to improve the mechenical properties or the functional charactristics of materials. This paper has been aimed to investigate the effects of plasma sprayed conditions, such as spray distance and arc power level, on sliding wear properties of plasma sprayed $Al_2$O$_3$-40%TiO$_2$coating layer. The sliding wear test using pin-on-disc type wear machine, has been conducted in several sliding speed for coating layer sparyed under different conditions. The result of this paper is that the wear resistance of plasma sprayed $Al_2$O$_3$-40%TiO$_2$coating layer is fluctuated with tile spray distance and the arc power level. The wear resiatance could be improved with decreasing the spray distance and with increasing the arc power level.

• Tribology and Lubricants
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• v.16 no.3
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• pp.194-200
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• 2000

In order to evaluate the effect of Nb on wear properties of high speed steel(HSS) by powder metallurgy, niobium-alloyed HSS have been prepared by adding 0%, 1%, 3% and 5%Nb to HSS of 6%W-5%Mo-4 %Cr-5%V-5%Co. Sliding wear tests were conducted at various sliding speed conditions under the constant pressure using a pin-on-disc type machine. The results of this study show that the wear resistance of HSS by powder metallurgy was increased by the addition of Nb within the range of sliding speed used in this experimental study. However, the amount of Nb did not improve the wear resistance. It may be due to the thermal stability of carbide and high temperature properties of the matrix containing Nb comparing to that without Nb.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.640-644
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• 2013

The present study provides the characteristics of friction noise under reciprocating sliding. The friction contact is generated between the aluminum plate and plastic, which results in friction noise. The experimental results reveal that the friction noise under reciprocating sliding can be produced as the friction coefficient increases. It is also shown that the vibration modes of the pin with dominant deflection in the sliding direction is participated on the friction noise.