• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.1-8
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• 2013

This study presents relations between the time lag and interaction index of the impinging-jet injectors using the time lag model in a model chamber. The response of the flame is analyzed to artificial perturbation with 5% amplitude of oxidizer speed at a resonance frequency. At the mixing point of fuel and oxidizer, which determines the characteristic length, the relationship between velocity perturbation and heat release rate is quantified by combustion parameters of interaction index and time lag. In this method, time lag or delay is calculated by the characteristic length and the average velocity obtained from numerical results. The tendency that the time delay decreases with axial jet velocity has been observed.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.426-429
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• 1988

A Microprocessor Based Digital Control System is inherently contained a control lag for processing the control program and a data detection time lag. This two types of time lag may cause the system to become unstable. In this paper proposed predictive state observer is used to solve the two time lag problems. I-P control algorithm is used to attain deadbeat response by adjusting the observer gain to overcome the parameter variation or with disturbance. The speed response shows good performance through computer simulation.

• Nuclear Engineering and Technology
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• v.49 no.1
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• pp.141-147
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• 2017

Mechanical shim is an advanced technology for reactor power and axial offset control with control rod assemblies. To address the adverse accuracy impact on the ex-core power range neutron flux measurements-based axial offset control resulting from the variable positions of control rod assemblies, the lead-lag-compensated in-core self-powered vanadium detector signals are utilized. The prompt ${\gamma}$ current of self-powered detector is ignored normally due to its weakness compared with the delayed ${\beta}$ current, although it promptly reflects the flux change of the core. Based on the features of the prompt ${\gamma}$ current, a method for configuration of the lead-lag dynamic compensator is proposed. The simulations indicate that the method can improve dynamic response significantly with negligible adverse effects on the steady response. The robustness of the design implies that the method is of great value for engineering applications.

• Structural Engineering and Mechanics
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• v.49 no.3
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• pp.297-309
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• 2014

Under lateral loads Framed Tube (FT) system exhibits reduction of cantilever efficiency due to the effect of shear lag. Braced Tube (BT) represents a valuable solution to overcome shear lag problems by stiffening the exterior frame with diagonal braced members. This study investigates the effect of shear lag on BT and FT under wind load. Shear lag and top-level displacement results are compared with previous findings by researchers on FT and BT systems. The investigation of the effect of various configurations in BT on the reduction the shear lag is another objective of this study. The efficiency of each structure is evaluated using the linear response spectrum analysis to obtain shear lag. STADD Pro software is used to run the dynamic analysis of the models. Results show there is relatively less shear lag in all the BT configurations compared to the FT structural system. Moreover, the comparison of the obtained result with those derived by previous studies shows that shear lag is not proportional to lateral displacement. With respect to results, optimum BT configuration in term of lower shear lag caused by lateral loads is presented.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.9
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• pp.807-810
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• 2015

In this paper, a finite impulse response(FIR) fixed-lag smoother is proposed for discrete-time nonlinear systems. If the actual state trajectory is sufficiently close to the nominal state trajectory, the nonlinear system model can be divided into two parts: The error-state model and the nominal model. The error state can be estimated by adapting the optimal time-varying FIR smoother to the error-state model, and the nominal state can be obtained directly from the nominal trajectory model. Moreover, in order to obtain more robust estimates, the linearization errors are considered as a linear function of the estimation errors. Since the proposed estimator has an FIR structure, the proposed smoother can be expected to have better estimation performance than the IIR-structured estimators in terms of robustness and fast convergence. Additionally the proposed method can give a more general solution than the optimal FIR filtering approach, since the optimal FIR smoother is reduced to the optimal FIR filter by setting the fixed-lag size as zero. To illustrate the performance of the proposed method, simulation results are presented by comparing the method with an optimal FIR filtering approach and linearized Kalman filter.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1488-1495
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• 2002

The response time represents how fast a system responds to a given disturbance at the system boundary. Flow restricting devices for controlling transients can result in a decrease in the peakm pressure, but may change response time. Response lag in a hydraulic system leads to inefficient working cycle and operator discomfort. The experiments were conducted in order to get information on the parameters which exert appreciable influence on the response time. The experimental apparatu including a hydraulic actuator, orifice and a hydraulic pump was an idealization of a bucket hydraulic shifting system. Experimental results show that the response time depends on operating pressure and flow rate. The effects of orifice type and size on the response time are quantified.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.4
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• pp.403-410
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• 2012

Purpose: The purposes of this study are to investigate accommodative response among emmetropes, spectacle wearer and contact lens wearer, and correlation between refractive error and accommodative respons for each group. Methods: The 72 subjects(144 eyes) who do not have any ocular diseases were participate in this study. Subjects were categorized into emmetropes, spectacle wearer and contact lens wearer by refractive error using closed-field auto-refractometer. We measured dominant eye, naked/habitual visual acuity and refractive error of monocular/binocular vision of refractive error for far/near distance with open-field auto-refractometer and calculated accommodative lag. Results: There were no significant difference of accommodative lag between right and left eye dominant and non-dominant eye, monocular and binocular vision, and spectacle lens wearer and contact lens wearer, However the accommodative lag of binocular vision was severe than monocular vision at near. The lag of myopia was larger than emmetropes, and male was larger than female. Significant correlation was found between refractive error and accommodative lag in total subjects and the same result was found in emmetropes and contact lens wearer. However there were no significant correlation in the spectacle wearer. Conclusions: There were significant difference between emmetrops and myopes in terms of accommodative lag, however accommodative lag of spectacle wearer was not different with contact lens wearer in myopes. There were also significant correlation between refractive error and accommodative lag in emmetropes and contact lens wearer, but the accommodative lag of spectacle wearer was not significantly correlated with refractive error.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.720-725
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• 1991

In this thesis, the lead-lag compensator is designed to improve output characteristics of flyback zero voltage switching quasi-resonant converters. The switch and the diode are assumed ideally. And the SMPS is modelled by state equations with four operation modes. And the model for controller design is also achived by using a state space averaging method, which is continuous time average of state variables every period. The lag, the lead and the lead-lag compensator is designed the SMPS respectively. The time domain analysis and the frequency domain analysis are done for each compensated circuit. It is possible increasing the phase margin and improving the transient response by the compensators. The phase lag compensator has small overshoot comparatively. But the bandwidth is narrower than the others, so it has longest settling time. For the phase lead compensator, the response come to steady-state within short period. But the overshoot is the largest due to its large peak gain. Finally, the phase lead-lag compensator has medium characteristics in the overshoot and the settling time.

• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.399-407
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• 2013

Spatial structures have the different dynamic characteristics from general rahmen structures. Therefore, it is necessary to accurately analyze dynamic characteristics and seismic response for seismic design of spatial structure. Keel arch structure is used as an example structure because it has primary characteristics of spatial structures. In case of spatial structures with different ground condition and time lag, multiple support excitation may be subjected to supports of a keel arch structure. In this study, the response of the keel arch structure under multiple support excitation and with time lag are analyzed by means of the pseudo excitation method. Pseudo excitation method shows that the structural response is divided into two parts, ground displacement and structural dynamic response due to ground motion excitation. It is known that the seismic responses of spatial structure under multiple support excitation are different from those of spatial structure under simple excitation. And the seismic response of spatial structure with time lag are different from those of spatial structure without time lag. Therefore, it has to be necessary to analyze the seismic response of spatial structure under multiple support excitation and time lag because the spatial structure supports may be different and very long span. It is shown that the seismic response of spatial structure under multiple support seismic excitation are different from those of spatial structure under unique excitation.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2532-2537
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• 2005

FIR(Finite Impulse Response) filter is well known to be ideal for the finite time state-space model, but it requires much computation due to its inherent non-recursive structure especially when the measurement interval grows to a large extent. And often a fixed-lag smoother based on the finite time interval is needed to monitor the soundness of the system model and the measurement model, but the computation burden of FIR-type smoother imposes much restriction of its usage for real-time application. Conventional recursive forms of FIR estimator[1]-[4] could not be used for real time applications, since they are numerically unstable in their recursive equations. To cope with this problem, we suggest a stable recursive form FIR estimator(SRFIR) and its usefulness is demonstrated for designing the real-time fixed-lag smoother on the finite time window through an example of detection of rate bias in the anti-aircraft gun fire control system.