Synchronization of Chaotic Gyros Based on Robust Nonlinear Dynamic Inversion

Yang, Inseok,Lee, Dongik Hindawi Limited 2013 Journal of applied mathematics (JAM) Vol.2013 No.-

<P>A robust nonlinear dynamic inversion (RNDI) technique is proposed in order to synchronize the behavior of chaotic gyros subjected to uncertainties such as model mismatches and disturbances. Gyro is a crucial device that measures and maintains the orientation of a vehicle. By Leipnik and Newton in 1981, chaotic behavior of a gyro under specific conditions was established. Hence, controlling and synchronizing a gyro that shows irregular (chaotic) motion are very important. The proposed synchronization method is based on nonlinear dynamic inversion (NDI) control. NDI is a nonlinear control technique that removes the original system dynamics into the user-defined desired dynamics. Since NDI removes the original dynamics directly, it does not need linearizing and designing gain-scheduled controllers for each equilibrium point. However, achieving perfect cancellation of the original nonlinear dynamics is impossible in real applications due to model uncertainties and disturbances. This paper proposes the robustness assurance method of NDI based on sliding mode control (SMC). Firstly, similarities of the conventional NDI control and SMC are provided. And then the RNDI control technique is proposed. The feasibility and effectiveness of the proposed method are demonstrated by numerical simulations.</P>

Preparation of primary reference material of argon in oxygen by the gravimetric method for application to thermometry

Yang, Inseok,Lee, Jin Bok,Moon, Dong Min,Kim, Jin Seog IOP 2017 Metrologia Vol.54 No.2

<P>Three mixtures of argon in oxygen with (1000, 350, 120) μmol mol<SUP>−1</SUP> amount fractions of argon were prepared by the gravimetric method for application to thermometry. The mixtures are to be used to study the effects of argon impurity in oxygen on the temperature of the triple point of oxygen. From an uncertainty assessment compliant with the international standards, the relative uncertainty of the amount fraction of argon in the two-step dilution method used in this work ranged from 0.040% to 0.072%. The uncertainty was dominated by the uncertainties in weighing the mass of argon in the pre-mixture and weighing the mass of the pre-mixture in the final mixture. The internal consistency of the amount fraction of argon given by the gravimetric method was verified to be within 0.025% by measurements via gas chromatography with a thermal conductivity detector. The resultant uncertainty in the amount fraction of argon corresponds to less than 5 μK in the effect of argon impurity on the triple point of oxygen. Therefore, the mixtures have sufficient precision for the thermal study of the argon-in-oxygen mixtures.</P>

Design of the Reconfigurable Load Distribution Control Allocator

Yang, Inseok,Kang, Myungsoo,Sung, Jaemin,Kim, Chong-Sup,Cho, Inje The Society for Aerospace System Engineering 2017 International Journal of Aerospace System Engineer Vol.4 No.1

This paper proposes the load distribution control allocation technique. The proposed method is designed by combining a conventional control allocation method with load distribution ability in order to reduce the stress acting on ailerons. By designing the weighting matrix as a function of the load distribution rule, the optimal deflection angles of each surface to satisfy both control goal and load distribution can be achieved. Moreover, rule based fault-tolerant control technique is also proposed. The rules are generated by considering both dominant control surfaces and the ratio of load distribution among surfaces. The performance of the proposed method is evaluated through numerical simulations.

The potential for using the hypereutectoid transition in Fe–C in thermocouple thermometry

Yang, Inseok,Kim, Yong-Gyoo BUREAU INTERNATIONAL DES POIDS ET MESURES 2007 METROLOGIA -BERLIN- Vol.44 No.2

<P>The eutectoid transition in the iron–carbon system around 730 ?C has been tested as a potential fixed point for use in thermocouple thermometry. Using a heating rate ≤ 1.5 ?C min<SUP>−1</SUP>, the α–γ transition showed a short, but repeatable, plateau with a repeatability of 0.07 ?C. However, the γ–α transition only exhibited a small discontinuity in a plot of emf versus time. Although only preliminary results were obtained here, once the thermodynamic (or the ITS-90) temperature, as well as its uncertainty, is assigned to this eutectoid transition, then the hypereutectoid transition in the iron–carbon system is potentially very useful, in that this fixed point can be obtained additionally while realizing the iron–carbon eutectic point.</P>

Construction and calibration of a large-area heat flow meter apparatus

Yang, Inseok,Kim, Daeho,Lee, Sanghyun,Jang, Hyunmin Elsevier Sequoia S.A 2019 Energy and buildings Vol.203 No.-

<P><B>Abstract</B></P> <P>A large-area heat flow meter apparatus that can measure the thermal conductivity of a 900 mm × 900 mm insulating specimen was constructed in this work with a relative expanded uncertainty of 1.4%. By the use of a reference material certified with an assigned value of thermal conductivity, the heat flux transducers in the apparatus were calibrated in the mean temperature range of −10 °C to +50 °C. The following three tests on the robustness of measurement results were conducted: (1) assessment of the reproducibility upon reloading the specimen a few times into the apparatus, (2) use of various temperature differences on the two surfaces of the specimen, and (3) configuration of the vertical temperature profile around the specimen differently while maintaining the temperatures on the specimen surface and their difference the same. The results of the three robustness tests supported that the measurements were consistent and the uncertainty assessment for the thermal conductivity measurement using the constructed heat flow meter apparatus was valid.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A heat flow meter apparatus for a 900 mm × 900 mm insulation specimen was constructed. </LI> <LI> The apparatus was calibrated using a certified material from −10 °C to +50 °C. </LI> <LI> The thermal conductivity measurement was tested to be reproducible and robust. </LI> <LI> The expanded uncertainty of the thermal conductivity measurement was 1.4%. </LI> </UL> </P>

Investigating the adequacy of a low-cost vector network analyser for microwave measurements in quasispherical resonators

Yang, Inseok,Underwood, Robin,de Podesta, Michael IOP Pub 2018 Measurement science & technology Vol.29 No.7

<P>Microwave measurements in quasispherical resonators (QSRs) have enabled remarkable improvements in primary gas thermometry, but the expense of vector network analysers (VNAs) restricts wider use of the technique. In this work we compare the performance of a commercially available, low-cost VNA with a fully-featured VNA in microwave resonance measurements in a QSR. For acoustic gas thermometry (AGT) where a relative uncertainty in frequency measurement in an order of 10<SUP>−7</SUP> is required, we have found that the accuracy of the low-cost VNA is easily sufficient. The use of a  +20 dB amplifier was also tested for both VNAs and allowed statistical uncertainties to be reduced by a factor of 5 to 12. The two VNAs showed agreement within 20  ×  10<SUP>−9</SUP> of the absolute frequency of microwave resonances. However, when the low-cost VNA was used with the amplifier, some spurious systematic effects were found which biased the measured resonance frequency at levels below 20  ×  10<SUP>−9</SUP>. These effects were apparent only when the amplifier was used with the low-cost VNA, because, when the amplifier was not used, the statistical uncertainty was much larger than the magnitude of these effects. While the physical cause of these systematic effects is not investigated in the present work, we made observations that could help to estimate their magnitudes. The comparison showed that the low-cost VNA, although being perfectly suitable for the AGT, may not be sufficiently accurate for applications where the required relative uncertainty in the frequency determination is of an order of 10<SUP>−9</SUP>.</P>

Reconfiguration Criterion for Fault-Tolerant Control

Yang, Inseok,Lee, Dongik,Han, Dong Seog Hindawi Limited 2015 Mathematical problems in engineering Vol.2015 No.-

<P>The reconfiguration criterion for tolerating actuator fault is proposed. The proposed reconfiguration criterion analyzes the relationship between normal actuators and the system states that are directly affected by faulty actuators. So the proposed criterion provides the possibilities of fault-tolerance. Moreover, it also provides the required number of redundant normal actuators.</P>

Designing a Robust Nonlinear Dynamic Inversion Controller for Spacecraft Formation Flying

Yang, Inseok,Lee, Dongik,Han, Dong Seog Hindawi Limited 2014 Mathematical problems in engineering Vol.2014 No.-

<P>The robust nonlinear dynamic inversion (RNDI) control technique is proposed to keep the relative position of spacecrafts while formation flying. The proposed RNDI control method is based on nonlinear dynamic inversion (NDI). NDI is nonlinear control method that replaces the original dynamics into the user-selected desired dynamics. Because NDI removes nonlinearities in the model by inverting the original dynamics directly, it also eliminates the need of designing suitable controllers for each equilibrium point; that is, NDI works as self-scheduled controller. Removing the original model also provides advantages of ease to satisfy the specific requirements by simply handling desired dynamics. Therefore, NDI is simple and has many similarities to classical control. In real applications, however, it is difficult to achieve perfect cancellation of the original dynamics due to uncertainties that lead to performance degradation and even make the system unstable. This paper proposes robustness assurance method for NDI. The proposed RNDI is designed by combining NDI and sliding mode control (SMC). SMC is inherently robust using high-speed switching inputs. This paper verifies similarities of NDI and SMC, firstly. And then RNDI control method is proposed. The performance of the proposed method is evaluated by simulations applied to spacecraft formation flying problem.</P>

Long-term stability of standard platinum resistance thermometers in a range between 0.01 °C and 419.527 °C

Yang, Inseok,Song, Chang Ho,Gam, Kee Sool,Kim, Yong-Gyoo Springer-Verlag 2012 METROLOGIA -BERLIN- Vol.49 No.6

<P>The long-term stability of standard platinum resistance thermometers (SPRTs) in a temperature range between 0.01 °C and 419.527 °C was investigated from 352 samples of data accumulated from fixed-point calibration conducted during a period of eleven years. The rates of change of resistance R<SUB>TPW</SUB> at the triple point of water and the resistance ratio at the freezing point of Sn (W<SUB>Sn</SUB>) and Zn (W<SUB>Zn</SUB>) were analysed. For 75% of the samples investigated, the rate of change of R<SUB>TPW</SUB> was within 5.17 mK/year in magnitude. For the same portion of SPRTs, the rates of change in W<SUB>Sn</SUB> and W<SUB>Zn</SUB> were within 0.82 mK/year and 1.69 mK/year, respectively. Further statistical investigation showed that measurement at the triple point of water only was not a sufficient test to identify the change in W<SUB>Sn</SUB> or W<SUB>Zn</SUB>. However, due to the strong correlation between the changes in W<SUB>Sn</SUB> and W<SUB>Zn</SUB>, measurement of the resistance ratio at one of the fixed points in the range of usage is adequate to identify possible change in the entire range of usage.</P>

Improving acoustic determinations of the Boltzmann constant with mass spectrometer measurements of the molar mass of argon

Yang, Inseok,Pitre, Laurent,Moldover, Michael R,Zhang, Jintao,Feng, Xiaojuan,Kim, Jin Seog BUREAU INTERNATIONAL DES POIDS ET MESURES 2015 METROLOGIA -BERLIN- Vol.52 No.5

<P>We determined accurate values of <I>ratios</I> among the average molar masses <I>M</I><SUB>Ar</SUB> of 9 argon samples using two completely-independent techniques: (1) mass spectrometry and (2) measured ratios of acoustic resonance frequencies. The two techniques yielded mutually consistent ratios (RMS deviation of 0.16   ?   10<SUP>−6</SUP> <I>M</I><SUB>Ar</SUB> from the expected correlation) for the 9 samples of highly-purified, commercially-purchased argon with values of <I>M</I><SUB>Ar</SUB> spanning a range of 2   ?   10<SUP>−6</SUP> <I>M</I><SUB>Ar</SUB>. Among the 9 argon samples, two were traceable to recent, accurate, argon-based measurements of the Boltzmann constant <I>k</I><SUB>B</SUB> using primary acoustic gas thermometers (AGT). Additionally we determined our absolute values of <I>M</I><SUB>Ar</SUB> traceable to two, completely-independent, isotopic-reference standards; one standard was prepared gravimetrically at KRISS in 2006; the other standard was isotopically-enriched <SUP>40</SUP>Ar that was used during NIST’s 1988 measurement of <I>k</I><SUB>B</SUB> and was sent to NIM for this research. The <I>absolute</I> values of <I>M</I><SUB>Ar</SUB> determined using the KRISS standard have the relative standard uncertainty <I>u</I><SUB>r</SUB>(<I>M</I><SUB>Ar</SUB>)  =  0.70   ?   10<SUP>−6</SUP> (Uncertainties here are one standard uncertainty.); they agree with values of <I>M</I><SUB>Ar</SUB> determined at NIM using an AGT within the uncertainty of the comparison <I>u</I><SUB>r</SUB>(<I>M</I><SUB>Ar</SUB>)  =  0.93   ?   10<SUP>−6</SUP>. If our measurements of <I>M</I><SUB>Ar</SUB> are accepted, the difference between two, recent, argon-based, AGT measurements of <I>k</I><SUB>B</SUB> decreases from (2.77   ?   1.43)  ?  10<SUP>−6</SUP> <I>k</I><SUB>B</SUB> to (0.16   ?   1.28)  ?  10<SUP>−6</SUP> <I>k</I><SUB>B</SUB>. This decrease enables the calculation of a <I>meaningful</I>, weighted average value of <I>k</I><SUB>B</SUB> with a uncertainty <I>u</I><SUB>r</SUB>(<I>k</I><SUB>B</SUB>)  ≈  0.6   ?   10<SUP>−6</SUP>.</P>