Commutation Compensation Strategy for Brushless DC Motor Based on Terminal Voltage Reconstruction

Li Guidan,Zhang Tianqi,Li Bin,Fu Tongling,Duan Peihua 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.4

In the sensorless brushless DC (BLDC) motor control system, the commutation signal is the key to measure the system performance. To improve the commutation accuracy, a commutation compensation strategy based on terminal voltage reconstruction is proposed. By analyzing the commutation process, the integral of ideal terminal voltage is adopted to determine the commutation error. Then considering the voltage clamping of the freewheel diode, the actual terminal voltage is analyzed in diff erent periods. In the non-commutation period, a PWM cycle is divided into three regions, and the corresponding duration can be calculated by fl oating phase current, and then the equality of actual and ideal terminal voltage integrals is revealed. In the commutation period, the instantaneous value of back-electromotive force (back-EMF) at commutation point is used to construct the ideal terminal voltage and the commutation time is determined by the edge detection. In this way, the integral of terminal voltage can be calculated precisely. Then the error index is introduced and the relationship between the commutation error and the error index is presented. To eliminate the commutation error, the PI controller is adopted which outputs the compensation angle. The proposed strategy avoids the phase shift errors and the accumulation of integral errors, moreover the feasibility and eff ectiveness are verifi ed by simulations and experiments under diff erent conditions. In addition, the strategy can also be used to correct the installation error of Hall sensor

Parametric Study of Dynamic Vibration Absorber with Negative Stiffness Applied to Floating Slab Track

Li Zhou,Tianqi Zhang,Yanyun Luo 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.9

In terms of the traditional dynamic vibration absorber (DVA), the vibration damping effect improves with the mass ratio of DVA increasing, and the vibration level of target system is effectively controlled in the case that the mass ratio of DVA is large. This characteristic restricts the application of DVA to the track because of the limited available space. This study proposes one type of DVA with negative stiffness (NSDVA) applied to floating slab track to reduce the track vibration under the condition of small mass ratio and presents a design methodology of NSDVA attached on flexible system. Firstly, the mechanical model of floating slab with NSDVA is simplified to a two-degree-of-freedom system, and theoretical expressions of NSDVA’s optimal parameters, i.e., ratio of frequency, damping and stiffness are deduced according to the fixed-point expansion theory and stability condition. Secondly, with the combination of the multi-modal control theory and the finite element method, optimal parameters of NSDVA applied to a multi-degree of freedom (MDOF) system are calculated. 3-D finite element model of floating slab-NSDVA is built in ABAQUS software, and the modal analysis of floating slab is conducted to determine the target modal and equivalent mass. Compared with the traditional Voigt type DVA, the NSDVA adopted in this paper is proved to be more effective to reduce the both floating slab and rail vibration level. The design methodology of NSDVA attached to a MDOF system presented in this paper is feasible.

Recent developments in the utilization of modified graphene oxide to adsorb dyes from water: A review

Tianqi Liu,Chukwunonso O. Aniagor,Marcel I. Ejimofor,Matthew C. Menkiti,Yakubu M. Wakawa,Jie Li,Rachid Ait Akbour,Pow-Seng Yap,Sie Yon Lau,Jaison Jeevanandam 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.117 No.-

Recently, there is an increasing concern on dye contamination in the aquatic environment. Elimination ofdye contaminants has gained significant attention among researchers due to their potential deleteriousrisk to human health and the ecosystem. Among the treatment technologies for dye removal from thewater system, the utilization of modified graphene oxide as an adsorbent has garnered increasingresearch interest due to its superior dye adsorption capacity. Hence, this review aims to comprehensivelypresent the classifications and hazards of dyes, types of preparation methods for modified graphene oxideand recent developments in the employment of modified graphene oxide to adsorb dyes from water. Additionally, the primary objective of this review is to emphasize on adsorption performances of modifiedgraphene oxide for dye removal in an aqueous medium, specifically focusing on the adsorption kinetics,adsorption isotherms and the effect of experimental parameters. Furthermore, the pertinentchallenges, tremendous opportunities and the future outlook of modified graphene oxide to be employedas a potential aqueous dye adsorbent were also discussed.

Experimental Study on Mechanical Properties of Q690 High Strength Steel in Marine Corrosive Environment

Hongchao Guo,Tianqi Lei,Jinguang Yu,Defa Wang,Xiaolei Li 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.2

In order to study the mechanical property degradation rule of Q690 high-strength steel in the ocean wave splash area, the rusted specimen is obtained by indoor damp heat surrounding soaking environment corrosion test. The scanning electron microscopy, uniaxial tensile and cyclic loading tests of corroded steel are performed. This paper analyzes the steel from elastic modulus, yield strength, ductility and law of hysteresis degradation under diff erent corrosion cycles and establishes the constitutive model of HSS. The results show that the appearance of HSS is obviously aff ected by the corrosion cycle. With the increase of the corrosion cycle, reddish-brown fl aky corrosion products are formed on the surface of the steel and there are obvious corrosion pits. After 100 days of corrosion, the corrosion rate of steel reached 7.21%; the elastic modulus and yield strength under uniaxial tension load decreased by 10.2% and 4.9%. Under the eff ect of cyclic reciprocating load, the hysteretic energy is reduced by 15.3%; at the same time, the test curve is fi tted by the secondary plastic fl ow model and the Ramberg–Osgood model and it is found that the shape parameter S 1 and the cyclic strengthening coeffi cient K’ are reduced by 20.1% and 10.2%, While the shape parameter S 2 and the cycle strengthening index n’ have no obvious changes.

Laser Vision-Based Automatic Trajectory Planning Technology for Spatial Intersecting Joint Weld

Zhenwei Jia,Tianqi Wang,Liangyu Li,Junjie He 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.1

This paper studies the laser vision-based automatic trajectory planning technology for spatial intersecting joint weld. Firstly, the mathematical model of T-type off-axis non-groove intersecting joint is established, and the welding seam characteristics of the intersecting joint are analyzed. Secondly, a triangular pseudo-rotation feature pixel detection algorithm based on monocular structured light vision is proposed to realize the rapid extraction and location of spatial intersecting joint weld. Then, a laser vision-based calibration method for the workpiece coordinate system of the T-type intersecting joint is proposed, the relationship between intersecting joint workpiece coordinate system and robot base coordinate system is established, and the trajectory equation is obtained. At last, a searching discrete of chord error interpolation control algorithm is proposed to automatically discrete and plan welding torch gesture data. Experiments show that the technology can achieve higher precision location and better intersecting joint weld trajectory planning, and realize high-quality automatic weld of intersecting joint.

Identification of onlline users' type based on clustering

Geng Peng,Tianqi Li,Fan Liu,Ying Liu,Benfu Lv 인하대학교 정석물류통상연구원 2009 인하대학교 정석물류통상연구원 학술대회 Vol.2009 No.10

User’s browsing on shopping websites is a complicated process which is affected by many factors. The users with different purposes and backgrounds tend to show different behavioral characteristics and shopping intentions, which areal hidden in weblog data of the sites. In this paper, we firstly introduce the method of data mining to cluster a month weblog data of a publishing house website, and then identify four types of online users: purchasing, browsing, information accumulating, and superficiality. Finally, we give an explanation for each type user in detail. The study of this paper could be used to improve marketing plans and shopping experiences of sites.

MicroRNA-301b promotes cell proliferation and apoptosis resistance in triple-negative breast cancer by targeting CYLD

( Hongming Song ),( Dengfeng Li ),( Tianqi Wu ),( Dan Xie ),( Kaiyao Hua ),( Jiashu Hu ),( Xiaochong Deng ),( Changle Ji ),( Yijun Deng ),( Lin Fang ) 생화학분자생물학회(구 한국생화학분자생물학회) 2018 BMB Reports Vol.51 No.11

Aberrant expression of microRNAs (miRNAs) plays important roles in carcinogenesis and tumor progression. However, the expression and biological role of miR-301b in triple-negative breast cancer (TNBC) remains unclear. Here we aimed to evaluate the roles and mechanisms of miR-301b in TNBC cells. miR-301b expression was assessed in TNBC specimens and cell lines by quantitative Real-Time PCR (qRT-PCR). TNBC cells were transfected with miR-301b mimics, inhibitors or Cylindromatosis (CYLD) small interfering RNA (siRNA) using Lipofectamine 2000. The functional roles of miR-301b were determined by cell proliferation, colony formation, and apoptosis assays. Western blots and qRT-PCR were used to measure the expression of mRNAs and proteins in the cells. We found that miR-301b was upregulated in TNBC specimens and cell lines. Overexpression of miR-301b promoted cell proliferation in TNBC cells, while inhibited the apoptosis induced by 5-FU. CYLD was downregulated by miR-301b at both mRNA and protein levels in TNBC cells. Dual-luciferase report assay confirmed that miR-301b downregulated CYLD by direct interaction with the 3’-untranslated region(3’-UTR) of CYLD mRNA. NF-κB activation was mechanistically associated with miR-301b-mediated downregulation of CYLD. However, inhibition of miR-301b reversed all the effects of miR-301b. In conclusion, miR-301b plays an oncogenic role in TNBC possibly by downregulating CYLD and subsequently activating NF-κB p65, and this may provide a novel therapeutic approach for TNBC. [BMB Reports 2018; 51(11): 602-607]

Manufacture and Characterization on Three-Dimensional Random Resonators of Porous Silicon/TiO2 Nanowires for Continuous Light Pumping Lasing of Perovskite Quantum Dots

Yining Mu,Tuo Zhang,Tianqi Chen,Fanqi Tang,Jikai Yang,Chunyang Liu,Zhangxiaoxiong Chen,Yiming Zhao,Peng Du,Haibo Fan,Yan Zhu,Guozhen Liu,Ping Li 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2020 NANO Vol.15 No.03

In recent years, all inorganic bismuth lead-halide perovskite nanocrystals [CsPbX3 (X=Cl, Br, I)] have received extensive attention due to their high performance in fluorescence quantum yield, narrow emission spectrum, and adjustable emission range. However, the disadvantages of high cost and poor stability have greatly limited the development prospects of the material. Here, in order to develop a perovskite quantum dot lasing cavity with high chemical stability, high quality factor and low fabrication cost, we have successfully fabricated a 3D random cavity device based on porous silicon/TiO2 nanowires. A TiO2 nanowire is grown on the porous silicon to form a 3D resonant cavity, and a perovskite quantum dot is spin-coated on the surface of the 3D resonant cavity to form a novel 3D complex film. The novel structure enhances the chemical stability and lasing quality factor of the resonant cavity while the fluorescence generated by the large quantum dots in the spatial interference structure constitutes the feedback loop, which will provide favorable support for the development of information optics.

Analysis and improvement of output power drop of dynamic wireless power transfer systems with transmitting coil switching for inspection robots

Yishuo Ding,Jiangui Li,Longyang Wang,Chen Wang,Guofu Zhu,Yuying Cheng,Tianqi Yu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.12

Dynamic wireless power transfer (DWPT) has received extensive attention due to its advantages of high security, high convenience, and high efficiency. To solve the problems of the mutual inductance and output power drop of DWPT systems for inspection robots, a new DWPT system with a trapezoidal-rectangular coupler has been proposed. First, the DWPT system topology and the switching strategy of the transmitting coil are introduced. Second, the real-time mutual inductances of the coupler in linear and curved motion are derived. Third, a new trapezoidal transmitting coil is presented. Finally, the performance of the DWPT system with the trapezoidal-rectangular coupler (TRC) is tested and compared to the DWPT system with the rectangular-rectangular coupler (RRC). Experimental results show that the minimum mutual inductance of the TRC is increased by 58.71%, and that the minimum output power is more than doubled in curved motion. Moreover, the mutual inductance drop rates of the TRC in linear and curved motion are reduced by 21.23% and 18.42%, respectively. The output power drop rates of the TRC-DWPT system are reduced by 18.99% and 16.12%, respectively. In addition, the Litz wire consumption is reduced by 8.28% in linear motion.

Damping Applications of Ferrofluids

Chuan Huang,Jie Yao,Tianqi Zhang,Yibiao Chen,Huawei Jiang,Decai Li 한국자기학회 2017 Journal of Magnetics Vol.22 No.1

Ferrofluids are a special category of smart nanomaterials which shows normal liquid behavior coupled with superparamagnetic properties. One of the earliest and most prospective applications of ferrofluids is in damping, which has prominent advantages compared with conventional damping devices: simplicity, flexibility and reliability. This paper presents the basic principles that play a major role in the design of ferrofluid damping devices. The characteristics of typical ferrofluid damping devices including dampers, vibration isolators, and dynamic vibration absorbers are compared and summarized, and then recent progress of vibration energy harvesters based on ferrofluid is briefly described. Additionally, we proposed a novel ferrofluid dynamic vibration absorber in this paper, and its damping efficiency was verified with experiments. In the end, the critical problems and research directions of the ferrofluid damping technology in the future are raised.