Tracking Control of Robotic Manipulators based on the All-Coefficient Adaptive Control Method

Yongjun Lei,Hongxin Wu 대한전기학회 2006 International Journal of Control, Automation, and Vol.4 No.2

A multi-variable Golden-Section adaptive controller is proposed for the tracking control of robotic manipulators with unknown dynamics. With a small sample time, the unknown dynamics of the robotic manipulator are denoted equivalently by a characteristic model of a 2-order multi variable time-varying difference equation. The coefficients of the characteristic model change slowly with time and some of their valuable characteristic relationships emerge. Based on the characteristic model, an adaptive algorithm with a simple form for the control of robotic manipulators is presented, which combines the multi-variable Golden-Section adaptive control law with the weighted least squares estimation method. Moreover, a compensation neural network law is incorporated into the designed controller to reduce the influence of the coefficients estimation error on the control performance. The results of the simulations indicate that the developed control scheme is effective in robotic manipulator control.

A recyclable Pd colloidal catalyst for liquid phase hydrogenation of a-pinene

Yongjun Yang,Xianxiang Liu,Dulin Yin,Zehui Zhang,Dichen Lei,Jing Yang 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.26 No.-

A recyclable Pd colloidal catalyst was found to be effective for the liquid phase hydrogenation of apinene. Under optimal conditions, a-pinene conversion of 99.4% and cis-pinane selectivity of 81.3% were obtained. Furthermore, the Pd colloidal catalyst could be recovered conveniently and reused for eight runs without significant loss of the catalytic activity and selectivity.

Enhanced catalyst activity by decorating of Au on Ag@Cu₂O nanoshell

Chen, Lei,Liu, Maomao,Zhao, Yue,Kou, Qiangwei,Wang, Yaxin,Liu, Yang,Zhang, Yongjun,Yang, Jinghai,Jung, Young Mee Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.435 No.-

<P><B>Abstract</B></P> <P>We successfully synthesized Au-decorated Ag@Cu<SUB>2</SUB>O heterostructures via a simple galvanic replacement method. As the Au precursor concentration increased, the density of the Au nanoparticles (NPs) on the Ag@Cu<SUB>2</SUB>O surface increased, which changed the catalytic activity of the Ag@Cu<SUB>2</SUB>O-Au structure. The combination of Au, Ag, and Cu<SUB>2</SUB>O exhibited excellent catalytic properties, which can further effect on the catalyst activity of the Ag@Cu<SUB>2</SUB>O-Au structure. In addition, the proposed Ag@Cu<SUB>2</SUB>O-Au nanocomposite was used to transform the organic, toxic pollutant, 4-nitrophenol (4-NP), into its nontoxic and medicinally important amino derivative via a catalytic reduction to optimize the material performance. The proposed Au-decorated Ag@Cu<SUB>2</SUB>O exhibited excellent catalytic activity, and the catalytic reduction time greatly decreased (5 min). Thus, three novel properties of Ag@Cu<SUB>2</SUB>O-Au, i.e., charge redistribution and transfer, adsorption, and catalytic reduction of organic pollutants, were ascertained for water remediation. The proposed catalytic properties have potential applications for photocatalysis and localized surface plasmon resonance (LSPR)- and peroxidase-like catalysis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Au-decorated Ag@Cu<SUB>2</SUB>O heterostructures via a simple galvanic replacement method were designed. </LI> <LI> We can easily control the density of the Au NPs on Ag@Cu<SUB>2</SUB>O by changing the concentration of the Au precursor. </LI> <LI> Ag@Cu<SUB>2</SUB>O-Au nanomaterials with high absorption exhibited significantly enhanced catalytic activity for 4-NP. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

SERS study of surface plasmon resonance induced carrier movement in Au@Cu₂O core-shell nanoparticles

Chen, Lei,Zhang, Fan,Deng, Xin-Yu,Xue, Xiangxin,Wang, Li,Sun, Yantao,Feng, Jing-Dong,Zhang, Yongjun,Wang, Yaxin,Jung, Young Mee Elsevier 2018 Spectrochimica acta. Part A, Molecular and biomole Vol.189 No.-

<P><B>Abstract</B></P> <P>A plasmon induced carrier movement enhanced mechanism of surface-enhanced Raman scattering (SERS) was investigated using a charge-transfer (CT) enhancement mechanism. Here, we designed a strategy to study SERS in Au@Cu<SUB>2</SUB>O nanoshell nanoparticles with different shell thicknesses. Among the plasmonically coupled nanostructures, Au spheres with Cu<SUB>2</SUB>O shells have been of special interest due to their ultrastrong electromagnetic fields and controllable carrier transfer properties, which are useful for SERS. Au@Cu<SUB>2</SUB>O nanoshell nanoparticles (NPs) with shell thicknesses of 48–56nm are synthesized that exhibit high SERS activity. This high activity originates from plasmonic-induced carrier transfer from Au@Cu<SUB>2</SUB>O to 4-mercaptobenzoic acid (MBA). The CT transition from the valence band (VB) of Cu<SUB>2</SUB>O to the second excited π-π* transition of MBA, and is of b<SUB>2</SUB> electronic symmetry, which was enhanced significantly. The Herzberg-Teller selection rules were employed to predict the observed enhanced b<SUB>2</SUB> symmetry modes. The system constructed in this study combines the long-range electromagnetic effect of Au NPs, localized surface plasmon resonance (LSPR) of the Au@Cu<SUB>2</SUB>O nanoshell, and the CT contribution to assist in understanding the SERS mechanism based on LSPR-induced carrier movement in metal/semiconductor nanocomposites.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We designed a shell-dependent Au@Cu<SUB>2</SUB>O nanoshell for SERS study. </LI> <LI> SERS contribution enables us to understand the possible enhancement of hybrid nanostructures. </LI> <LI> LSPR-induced carrier movement in Au@Cu<SUB>2</SUB>O nanocomposites. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>We designed the shell-dependent Au@Cu<SUB>2</SUB>O core-shell nanoparticles (NPs) for SERS study. For the electron-hole pairs in the Cu<SUB>2</SUB>O, the plasmon induced resonant energy transfer from Au to the Cu<SUB>2</SUB>O and the direct electron transfer simultaneously which can be observed from the SERS intensity.</P> <P>[DISPLAY OMISSION]</P>

Lightweight Design of an Automotive Battery-Pack Enclosure via Advanced High-Strength Steels and Size Optimization

Pan Yongjun,Xiong Yue,Wu Lei,Diao Keshan,Guo Wei 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.5

The battery packs are crucial components of electric vehicles and may severely affect the continue voyage course and vehicle safety. Therefore, design optimization of the battery-pack enclosure (BPE) is critical for enhanced mechanical and crashwrothiness performances. In this study, a lightweight design of an automotive BPE under the loading conditions is presented based on the advanced high-strength steels (AHSSs) and size optimization. A numerical analysis procedure is also introduced for the lightweight design. First of all, a nonlinear finite element (FE) BPE model was established and validated through the modal test. Secondly, the random vibration simulation was performed based on the sensitivity analysis to initially determine the AHSSs and thickness for the components of the BPE. Next, the material and thickness were determined by the fixed frequency vibration analysis. Moreover, the mechanical shock and fatigue life were analyzed numerically. Finally, the crashworthiness of the optimized BPE model was verified by crash and crush simulations. The results show that the optimized BPE structure has a 10.41 % lightweight gain, while assuring enhanced dynamic performances. The introduced numerical procedure could be used to quickly determine the material and thickness of each component of BPE. The design optimization process was found beneficial to reduce the number of physical tests and product development cost and shorten product development cycles.

Enriched finite element method for 2-D and 3-D blunt crack problems in a viscoelastic medium

Jingbo Duan,Yongjun Lei,Daokui Li 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.3

The analysis of two-dimensional and three-dimensional blunt crack problems in a linear viscoelastic medium is numerically investigated using the enriched finite element method. The enriched crack-tip elements are established by enriching the asymptotic displacement fields at the blunt crack front to the regular elements. The corresponding transition elements are formulated to eliminate displacement field incompatibility. The viscoelastic incremental formulations for the enriched finite element method in time domain are derived according to the Boltzmann superposition principle. The time-dependent deformations of crack are presented and the stress intensity factors are directly obtained from the enriched degree of freedoms. The numerical examples indicate that the enriched finite element method is extremely suitable for dealing with complicated blunt crack problems.

Hybrid Precoding for mmWave Massive MU-MIMO Systems with Overlapped Sub-array: A Modified GLRAM Approach.

Ting Ding,Yongjun Zhao,Lei Zhang 한국통신학회 2021 ICT Express Vol.7 No.4

Mmillimeter-wave (mmWave) massive multiuser multiple-input multiple-output (MU-MIMO) system usually utilizes hybrid precoding to reduce complex hardware and high energy consumption. However, most hybrid precoding scheme consider the fully connected architecture, which may result in a significant loss of energy efficiency. In this paper, we propose a hybrid precoding scheme based on the overlapped subarray architecture (OSA), where the analog part of the MU-MIMO system is realized by a OSA network. Based on the OSA architecture, a modified generalized low rank approximation of matrices (GLRAM) based hybrid precoding scheme is designed to maximize the achievable sum-rate, where the analog precoding algorithm apply the phase alignment technology and GLRAM approach to obtain RF precoder/combiner with high array gain provided by massive MIMO system. Then, the block diagonalization (BD) technology is performed to obtain the digital precoding matrix for the multiplexing gain. Simulation results show that the modified GLRAM based hybrid precoding algorithm for OSA architecture can reduce the number of iterations. Compared with the existing hybrid precoding algorithm, it achieves higher spectral efficiency and lower complexity.

Enriched finite element method for three-dimensional viscoelastic interfacecrack problems

Junhui Yang,Yongjun Lei,Junli Han,Shangyang Meng 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.2

The enriched finite element method is developed for three-dimensional problems of an interface crack between elastic and viscoelastic (including dissimilar viscoelastic) materials. According to the displacement fields of elastic interface crack, the displacement fields of viscoelastic interface crack are derived through the correspondence principle. By incorporating the displacement expressions into the displacement model of regular element, the incremental formulations of enriched element are derived. The stress intensity factor, and strain energy release rates can be solved based on the enriched degree of freedoms. A 3-D through interface crack at the center of jointed dissimilar viscoelastic plate subjected to remote tension and a quarter-circular viscoelastic interface corner crack subjected to uniform thermal loading was investigated using the enriched finite element method. It is shown that the present solutions are consistent with the analytical solutions, which indicates the present method is correct and efficient.

Transfer function modeling of structural vibration of complex aerospace structures based on finite element analysis

Xin Feng Wu,Yongjun Lei,Daokui Li,Yan Xie 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.5

An approach to establish the transfer function of complex aerospace structures to express their structural vibration behavior through finite element modeling is proposed. The fundamental idea of the approach is to characterize the vibrations of complicated structures through the transfer function model for an advanced control system design, while the parameters of the model are identified from the response data obtained through finite element analysis. The proposed method comprises four steps, namely, finite element modeling and validation, data preparation based on the finite element analysis, parameter identification of the transfer function, and model validation,and is presented from both frequency and time domains. The developed approach is applied to a cantilever beam, a strap-on launch vehicle,and a local part of the aerospace structure to demonstrate the method’s effectiveness and satisfactory performance.

SERS study of Ag/FeS/4-MBA interface based on the SPR effect

Ma, Ning,Zhang, Xin-Yuan,Fan, Wenyue,Guo, Shuang,Zhang, Yongjun,Liu, Yang,Chen, Lei,Jung, Young Mee Elsevier 2019 Spectrochimica acta. Part A, Molecular and biomole Vol.219 No.-

<P><B>Abstract</B></P> <P>In this work, an ordered metal-semiconductor molecular system was introduced, and 4-mercaptobenzoic acid (4-MBA) was employed to study the charge transfer (CT) at the metal-semiconductor interface based on surface-enhanced Raman scattering (SERS) spectra. The thickness of the sputtered FeS was controlled so that the surface plasmon resonance (SPR) of Ag underwent a displacement change, and the contribution of the SPR to the CT was studied through surface plasmon (SP) absorption. Furthermore, SERS spectra obtained at different excitation wavelengths were used to calculate the degree of CT in the layer-by-layer sputtering system. When Ag was irradiated with incident light, the strong SPR of Ag was excited, generating an increased electromagnetic field (EM). This amplified EM generated hot electrons at the interface between the FeS and Ag, and then the hot electrons were rearranged. Therefore, we established a simple and effective method for studying the impact of SPR on interfacial CT and analyzed the SERS spectra in accordance with Lombardi's basic theory and the physical effects associated with SPR. This theory is in good agreement with the experimental results. On this basis, we also proposed a mechanism by which SPR impacts the CT, which is beneficial for studying interfacial CT and obtaining an in-depth understanding of the CT mechanism in SERS. This work also enables the expansion of the applications of the SERS technique in the field of nanomaterials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SERS substrate was designed based on the layer-by-layer sputtering of Ag/FeS. </LI> <LI> 4-MBA was employed to study the CT at the metal-semiconductor interface. </LI> <LI> The SPR of Ag promotes the electron transfer process of the Ag/FeS/4-MBA system. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>In this paper, we designed a layer-by-layer sputtering of Ag and FeS on the PS template. FeS, as an ultranarrow bandgap semiconductor with a bandgap width of only 0.1 eV, exhibited different properties for SERS. The SPR of Ag can be tuned by controlling the FeS film thickness, which is beneficial for studying interface CT and obtaining an in-depth understanding of the CT mechanism in SERS.</P> <P>[DISPLAY OMISSION]</P>