• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.10
• /
• pp.67-76
• /
• 2008

In this research, a simple technique for designing PID controller, which guarantees robust stability for two-mass systems with parameter uncertainties as well as rigid-body behavior and zero steady-state error,is described. As well, such a PID controller is designed to mate two important frequencies, at which the given system is excited, very close so that an appropriate reference profile generated by using command shaping techniques can cover those two frequencies. Root-locus analysis. which shows traces of closed-loop poles for the given system, is used to design this PID controller. Finally, feedforward controller is added to improve tracking performance of the closed-loop system. Simulation for a system with a flexible mode and parameter uncertainties is executed to prove the feasibility of this technique.

• Journal of IKEEE
• /
• v.26 no.4
• /
• pp.553-559
• /
• 2022

In this paper, RC snubber circuit design technology for oscillation suppression in half-bridge configuration of cascode gallium nitride (GaN) field effect transistors (FETs) is analyzed. A typical wide band-gap (WBG) device, cascode GaN FET, has excellent high-speed switching characteristics. However, due to such high-speed switching characteristics, a false turn-off problem is caused, and an RC snubber circuit is essential to suppress this. In this paper, the commonly used experimental-based RC snubber design technique and the RC snubber design technique using the root locus method are compared and analyzed. In the general method, continuous circuit changes are required until the oscillation suppression performance requirement is met based on experimental experience . However, in root locus method, the initial value can be set based on the non-oscillation R-C map. To compare the performance of the two aforementioned design methods, a simulation experiment and a switching experiment using an actual double pulse circuit are performed.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.7
• /
• pp.29-35
• /
• 2002

Aeroelastic characteristics of a deployable missile control fin have been investigated. A deployable missile control fin is modeled by a 2-dimensional typical section. Supersonic Doublet-Point method is used for the computation of supersonic unsteady aerodynamic forces and Karpel's Minimum-State approximation is used for the aerodynamic approximation. Root-locus method and time-integration method are used for the linear and nonlinear flutter analyses. For the nonlinear flutter analysis the deployable hinge is represented by a asymmetric bilinear spring and is linearized by using the describing function method. From the flutter analyses, the effects of nonlinear parameters on the aeroelastic characteristics are investigated.

• Proceedings of the Plant Resources Society of Korea Conference
• /
• 2018.04a
• /
• pp.17-17
• /
• 2018

Panax ginseng Meyer is a perennial medicinal plant, the roots of which has been used in the traditional formulations in Oriental countries. To understand its floral transition, we isolated Flowering Locus T (FT) from ginseng, the bioinformatics analysis of PgFT has revealed a considerable homology to the higher plants, with the essential amino acids for FT function are conserved. The phylogenetic analysis has shown that the PgFT is belonged to the shrub classes of plants and closest kin to Jatropha curcas FT. The expression profiling from juvenile (2-year-old) were abundant in leaves as well as in root and was concentrated in the secondary leaflet and stem bottom in adult (4-year-old) ginseng plant tissues, moreover PgFT transcript displayed photoperiod dependent oscillation. The ectopic expression of PgFT in Arabidopsis thaliana, exhibit precocious flowering and several floral pathway integrators were up-regulated, interestingly their root length was increased in the transgenic seedlings. Therefore, we could conclude that PgFT encodes a florigen that acts as a key regulator in the flowering pathway in ginseng and hypothesize that, it might involve in the underground organ development as well. We believe our finding could provoke future studies on the physiology and development in P. ginseng.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.1
• /
• pp.209-215
• /
• 2002

A study of the guideway vehicle was made for a comparison of ride stabilities between its two primary steering types; one is the front wheel steering and the other the front-rear wheel. A numerical model as a closed loop system was built for an investigation of various factors to have an influence on the vehicular critical speed which is closely associated with ridabilities. It was shown that dynamics stabilities of the front steering type was much better over a large value of steering gain and the longer distance between front axle and guide link for both types provided better stabilities as well. A large steering gain ratio of the front to the rear significantly plays an important role in an improvement of stability in the front-rear steering. To observe a qualitative trend on stability behaviors, the root locus was obtained by considering a time lag which may be frequently caused by the complicated steering mechanism. In performing so, the appropriate selection of steering gain had a greater effect on the front-rear steering vehicle far more ride comfort. In addition, the dynamics model proposed here can be utilized for a more accurate evaluation on the vehicle design in lateral or yawing absorber and moreover expanded for the analysis of independent four-wheel steering vehicle.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.3
• /
• pp.248-257
• /
• 2016

Recently, researches on the free-piston Stirling engines(FPSEs) are actively investigated. FPSEs have merits in its light weight, simple structure, and little need for maintenance, thus becoming a promising solution for the power conversion of renewable energy and waste heat recycle. This paper presents the methodology that estimates damping coefficients using analytical models of linear and nonlinear dynamics for FPSEs, and validates the methodology by comparing with existing experimental results. The analysis model predicts an operable range of linear damping coefficients forming limit cycles by using the root locus, and time responses obtained by numerical integration determines nonlinear damping coefficients. The model predictions are compared with experimental results of the well-known FPSE B-10B. We also investigate the damping characteristics regarding heater temperatures and power piston motions.

• Korean journal of applied entomology
• /
• v.46 no.1 s.145
• /
• pp.169-173
• /
• 2007

Root-knot nematode damage was found on yam, Dioscorea bulbifera in Andong Korea. From the root-knots, female nematodes were isolated and subjected to DNA sequence analysis. Sequence of cytochrome oxidase subunit II (COII) was analyzed from the genomic DNA of the isolate. COII locus size and sequence of the nematode isolate were similar to those of Meloidogyne javanica or M. incognita. However, an analysis of HinfI restriction site, a species-specific character between these two species, showed that the isolate did not match to either M. javanica or M. incognita.

• Proceedings of the KIPE Conference
• /
• 2016.07a
• /
• pp.243-244
• /
• 2016

A discrete time domain modeling for the duty-cycle-controlled buck LED driver is presented in this paper. Based on the modeling result, a root locus analysis for the buck LED driver is done to derive the stability boundaries of feedback gains.

• Proceedings of the KIEE Conference
• /
• 1998.11b
• /
• pp.445-447
• /
• 1998

This paper shows simulation results for stability and performance of two INS/GPS integration systems. First, the code tracking error of GPS receiver is analyzed by spectrum analysis and simulated for the tight and loose INS/GPS integrations. Next, stability of the integrated systems are simulated using root locus method. As loop filter in the GPS receiver, passive filter and active filter are used and compared.

• Proceedings of the KIPE Conference
• /
• 2017.07a
• /
• pp.98-99
• /
• 2017

A discrete time domain modeling for the current-mode-controlled buck LED driver is presented in this paper. Based on the modeling result, a root locus analysis for the buck LED driver with slope compensation is done to derive the stability boundaries of feedback gains.