• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10B
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• pp.855-864
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• 2008

Optical link techniques compensating chromatic dispersion and nonlinear effects, which affect distortion of optical signals, generated in single mode fiber are investigated through computer simulation and design rule of these link techniques is proposed for implementation of wideband and long-haul WDM ($24{\times}40$ Gbps) transmission system. The optical link consist of dispersion management (DM) compensating the cumulated dispersion through total transmission line and optical phase conjugation in middle of total transmission line for compensating distorted signals by frequency inversion. DM schemes considered in this research are lumped DM and inline DM. It is confirmed that eye opening penalty (EOP) of overall WDM channels are more improved than those in WDM transmission systems with only optical phase conjugator (OPC), if DM is additionally applied to these systems. And, design rule in both DM schemes are proposed by using effective residual dispersion range. It is confirmed that inline DM is better than lumped DM in the improving EOP of total WDM channels and in effective residual dispersion range.

• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.134-141
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• 1997

We design the single mode dispersion-compensating fibers (DCF) which may be necessary for upgrading the previously installed 1.31 ${\mu}{\textrm}{m}$ optical communication system to the 1.55 ${\mu}{\textrm}{m}$ system. To obtain the optimum index profile that allows large negative dispersion at 1.55 ${\mu}{\textrm}{m}$, parabolic-index, double-clad fibers are analyzed by applying the 1-D FEM to the scalar wave equation of optical fibers. In constideration of macro-bending loss, the fibers are designed so that the cutoff wavelength of the $LP_{01}$ mode is greateer than 1.80 ${\mu}{\textrm}{m}$. The computer simulations show that the lower bound of the dispersion at 1.55 ${\mu}{\textrm}{m}$ is limited to about -120 ps/nm . km for the fiber index profiles satisfying the $LP_{01}$'s cutoff condition.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.35-42
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• 2004

The control systems with friction cause the steady state error and slow response, because friction is a sensitive to the change of system condition and has highly nonlinear characteristics. To overcome these problems and do precise position control for a ball-screw system, we use Coulomb friction estimator and the sliding mode control(SMC) to compensate its negative effect. The applied SMC for tracking position has a characteristics of robust stability and reducing chattering, and is derived from the Lyapunov stability theorem and reaching condition. Compensating the estimated friction torque to the bounded disturbance term of the SMC's equivalent control input, it has a tracking performance better than the PID from the experimental results.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.3
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• pp.93-101
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• 2002

The effect of nonlinear friction in the low velocity is dominant in precise controlled mechanisms and it is difficult to identify the friction effect. The friction model which Canudas suggested so called, LuGre model is well expressed the friction effect as Streibeck in the law velocity. But it\`s model parameters were estimated continuously in operation for precise control. This paper suggests the sliding mode controller and observer for compensating the friction effect. Experimental results for a ball-screw system show that the proposed method has a good performance especially in the low velocity.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1158-1168
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• 1994

A variable structure control scheme(VSCS) with sliding mode that can be applied to the process with input/output(I/O) delay is proposed and its control performances is evaluated. The proposed VSCS with and output feedback scheme comprises a variable structure controller, a servo dynamic for tracking the set-poing, and a Smith predictor for compensating the effects of time delay. The robustness against the parameter variations and external disturbances can be achieved by the proposed VSCS even when the controlled process includes I/O delay. And the desired transient response is obtained by simple adjustment of the coefficients of the switching surface equation.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.506-506
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• 2000

To improve control performance of a non-linear system, many other researches have used the sliding mode control algorithm. The sliding mode controller is known to be robust against nonlinear and unmodeled dynamic terms. However. this algorithm raises the inherent chattering caused by excessive switching inputs around the sliding surface. Therefore, in order to solve the chattering problem and improve control performance, this study has developed the sliding mode controller with a perturbation estimator using the observer-based fuzzy adaptive network generates the control input for compensating unmodeled dynamics terms and disturbance. And, the weighting parameters of the fuzzy adaptive network are updated on-line by adaptive law in order to force the estimation errors to converge to zero. Therefore, the combination of sliding mode control and fuzzy adaptive network gives rise to the robust and intelligent routine. For evaluating control performance of the proposed approach. tracking control simulation is carried out for the hydraulic motion simulator which is a 6-degree of freedom parallel manipulator.

• Journal of Information Processing Systems
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• v.20 no.1
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• pp.105-115
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• 2024

The hybrid teaching approach of "MOOC + SPOC + Flipped Classroom" overcomes the constraints of time and space that are typically associated with traditional teaching methods, thus compensating for the shortcomings of traditional approaches. These changes in education are driven by the "Internet+" wave and the growing popularity of online teaching. The "MOOC + SPOC + Flipped Classroom" hybrid teaching mode can successfully compensate for the drawbacks of traditional teaching methods, thereby overcoming their restrictions. By defining relevant concepts, one can distill the key characteristics of the "MOOC + SPOC + Flipped Classroom" hybrid teaching mode. Formative assessment was employed to thoroughly evaluate the effectiveness of this teaching approach. By leveraging the advantages of massive open online course (MOOC), small private online course (SPOC), and flipped classroom, the "MOOC +SPOC + Flipped Classroom" teaching mode incorporates real-time student assessment through peer evaluation, computer-aided evaluation, and teacher evaluation. This mode promotes the simultaneous development of theoretical knowledge and practical skills, helping students to establish strong foundations while fostering their practical abilities. While the traditional teaching method remains fruitful, the convenience of today's network allows the teaching profession to continually evolve. The traditional teaching mode heavily relies on teachers, making it impossible to conduct lessons without them. However, the development of MOOC enables students to seek knowledge online from their preferred teachers, rather than solely relying on their assigned instructors.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.1
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• pp.71-81
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• 1995

In this paper, a new speed control scheme for induction motor drives that regular sampled PWM and harmonic elimination switching pattern over the full range of output speed is presented. The proposed scheme(hybrid scheme) provides three mode and guarantees smooth voltage boost. A detailed description of the scheme, along with the relalization aspect, is described. Moreover, methods of compensating for dead time and optical transmission system of drive signal are proposed and investigated. Finally, experimental investigation of hybrid scheme is presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.997-1005
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• 2008

Linear motor stage is a useful device in precision engineering field because of its simple power transmission mechanism and accurate positioning. Even though linear motor stage shows fine positioning accuracy along travel axis, geometric dependent errors which relay on machining and assembling accuracy should be addressed to increase total positioning performances. In this paper, we suggests a cost effective yaw error compensation servo-system which is mounted on platform of the stage and nullify travel position dependent yaw error. This paper also provides a method of designing a sliding mode control which is robust to existing friction disturbance and model uncertainties. The reachability condition of slinding mode control for the yaw error compensating servo-system has been established. From some experimental results by using an experimental set-up, the sliding mode control showed its effective in disturbance rejection and its performance was superior to conventional linear controls.

• Journal of the Korean Wood Science and Technology
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• v.40 no.5
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• pp.327-334
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• 2012

Wood and concrete show significantly different physical properties, and it need to be firstly understood for using wood-concrete composite. This study is performed for compensating this and effective hybridization of wood and concrete. This research in planned for wood-concrete composite after previous research which deals the shear performance with different anchorage length of steel rebar in wood. Yield mode and reference design value (Z) were derived using EYM (European Yield Model). And the yield mode changed before and after anchorage length of 10~15 mm - $I_s$ mode to IV mode. There was not increasing tendency of shear performance with increased anchorage length for over 20 mm of anchorage in concrete. And wood composite shows 65% and 93% on initial stiffness and yield load respectively compared with the wood-concrete composite. Wood-concrete composite showed brittle failure after yield point while wood-to-wood composite showed ductile failure.