A Modifed Finite Control Set Model Predictive Control for 3L−NPC Grid−Connected Inverters Using Virtual Voltage Vectors

Jianguo Lyu,Binghui Ma,Han Yan,Zhendong Ji,Jinyong Ding 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.1

In order to improve the performance of a 3−level neutral point clamped (3L−NPC) grid−connected inverter with fnite control set model predictive control (FCS−MPC), this paper proposes a modifed FCS−MPC algorithm based on the rearranged control set (MFCS−MPC). By adding synthetic virtual voltage vectors to rearrange the fnite control set (FCS) of the 3L−NPC inverter, the frequency spectrum of output leg voltage becomes concentrated, which is benefted for decreasing total harmonic distortion (THD) of grid currents and makes it easier to design output flters for the grid−connected inverter. Moreover, based on switching state sequences of virtual voltage vectors, the modifed predictive model of the proposed method is established considering capacitor voltage diference. Besides, according to the location of the reference output voltage vector, a preselection step is incorporated into MFCS−MPC to narrow the control set for predictions, which avoids evaluating all candidate voltage vectors in the control set, and hence, the online computational burden is signifcantly reduced. A prototype of 3L−NPC grid−connected inverter is established to validate the proposed MFCS−MPC method and the experimental results show that this method has excellent static and dynamic performance, with a low THD for a wide range of modulation indexes.

Attitude Control Design for Hypersonic Reentry Vehicles Subject to Control Direction Reversal via Sliding Mode Approach

Yixin Ding,Zongyi Guo,Yonglin Han,Jiaqi Wang,Jianguo Guo,Zequn Liu,Jinlong Zhao 한국항공우주학회 2024 International Journal of Aeronautical and Space Sc Vol.25 No.2

This paper investigates the control direction reversal issue for the attitude control design for hypersonic reentry vehicles, and proposes a novel sliding mode control law which addresses the control direction switching and strong robustness requirement simultaneously. Firstly, the disturbance observer is introduced to estimate the unmatched uncertainties in the attitude model of hypersonic reentry vehicles, and then a periodic function-involved sliding mode control is presented and the bounded stability of the closed-loop system is guaranteed via Lyapunov stability theory. The merits of the proposed method lie in that the closed-loop system is stable even under the unknown control direction reversal, and the unmatched uncertainties can be addressed by the disturbance observer. Finally, the simulation verifies the effectiveness and superiority of the proposed control.

Effect of Surface Waviness on the Performances of an Aerostatic Thrust Bearing with Orifice-Type Restrictor

Hui Zhuang,Jianguo Ding,Peng Chen,Yu Chang,Xiaoyun Zeng,Hong Yang,Xingbao Liu,Wei Wei 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.10

In this paper, four waviness types are presented to investigate the effect of surface waviness on the static performance, dynamic performance and stability of an aerostatic thrust bearing with orifice-type restrictor. The influences of wave amplitude and rotational speed on the bearing performances are studied. The Reynolds equation is first solved through small perturbation method to obtain the static and dynamic characteristics. Subsequently, by adopting an iterative method based on the acquired dynamic coefficients, a numerical method is proposed to analyze the bearing stability. The calculated critical supply pressure is compared with that obtained by the traditional orbit method and it indicates that the proposed method has higher computational efficiency. The results show that the surface waviness has great influence on the bearing performances and the effect becomes increasingly pronounced with the growth of wave amplitude. The performances are more sensitive to the waviness arranged in bearing radial direction than circumferential direction. The enhancement of certain performance is always accompanied by the decline of another performance for the bearing with wave pattern on the surface, which leads to the fact that the bearing performances cannot be comprehensively improved in static characteristic, dynamic characteristic and stability. Besides, high rotational speed will cause pneumatic instability more readily. Finally, a stiff ness measuring experiment and a modal test are performed to verify the accuracy of computational analysis and results.

Interfacial micromechanics modeling for bolted joints in ultra-precision machine tools

Yu Chang,Jianguo Ding,Hui Fan,Yuanyuan Ding,Hui Zhuang,Peng Chen 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

Bolted joints are widely adopted in various mechanical structures. However, the uncertainty and complexity of the contact surfaces affect accurate modeling. Herein, an interfacial micromechanics model is proposed to characterize the contact behaviors of bolted joints in an ultra-precision machine tool (UMT). The bolted joint is modeled as a virtual material layer with transversely isotropic behaviors, whose constitutive relation is identified by fractal theory. The proposed model accurately formulates the multi-scale contact characteristics and allows convenient integration with the structural dynamic modeling of UMT. Dynamic analysis of the simulation results and the experimental measurements in the time and frequency domains was conducted to identify the most sensitive factor affecting the tool tip vibration. On this basis, the structural optimization for the UMT was further implemented, which effectively reduced vibration by 15.5 %. The dynamic predictions were validated by modal and vibration response tests.

Preliminary Correlation Between Warm Needling Treatment for Knee Osteoarthritis of Deficiency-Cold Syndrome and Metabolic Functional Genes and Pathways

Conge Tan,Weijun Ding,Wenzhe Feng,Jianguo Wang,Miqu Wang 사단법인약침학회 2010 Journal of Acupuncture & Meridian Studies Vol.3 No.3

The warm needling technique used in traditional Chinese medicine has been shown to be effective in the treatment and prevention of knee osteoarthritis (OA), but the biological mechanisms behind this action have not been well explored. This study investigated the molecular mechanisms behind warm needling using cDNA microarray technology, thus providing further scientific evidence for its efficacy. Ten patients with knee OA of deficiency-cold syndrome were selected for 2 weeks of warm needling treatment. This treatment involved stimulating the selected acupoints using needles with a burning moxa stick on their handle for 40 minutes per session. Pain intensity and accumulated clinical scores of deficiency-cold syndrome were assessed pretreatment and posttreatment using a 40-factor questionnaire of OA with deficiency-cold syndrome. Four patients with the best therapeutic efficacy were selected for cDNA microarray testing. Among the four patients, 41, 246,57 and 70 differentially expressed genes were obtained, with more than 50% of these differentially expressed genes functionally linked to primary, cellular and energy metabolism pathways. This work demonstrates that the molecular mechanism behind warm needling treatment may be associated with the regulation of metabolism-related genes and pathways.

Correlation between in vitro fertilization and artificial insemination in Holstein bulls

Sun Wei,Li Yunxia,Su Jie,Bao Xiangnan,Ding Rui,Zhao Gaoping,Cao Guifang,Hu Shuxiang,Wang Jianguo,Sun Qingyuan,Yu Haiquan,Li Xihe 아세아·태평양축산학회 2021 Animal Bioscience Vol.34 No.12

Objective: Owing to the lack of a breeding index for efficient and quick fertility evaluations of Holstein bulls when using traditional or genome-wide detection methods, this study aimed to determine whether in vitro fertilization (IVF) could be used as an indicator of conception rate of artificial insemination (AI).Methods: Conventional and sexed frozen semen from nine bulls were used for IVF and AI.Results: The IVF and AI conception rates of each bull were confirmed to be positively correlated between the conventional frozen and sexed frozen semen. The correlation coefficient R values of nine bulls between IVF and AI methods were 0.73 and 0.97 for the conventional frozen and sexed frozen semen, respectively. The average conception rate of three bulls undergoing AI was 69.5% and 64.2%, 61.8% and 58.8%, and 48.2% and 46.2% in first-, second-, and third-born cows when conventional frozen and sexed frozen semen were used, respectively, which showed a positive correlation with the fertilization rate in the same parity. We propose an evaluation standard to assess the fertilization ability of bulls based on their IVF test results, which is categorized into three grades: grade one, normal fertility bull with an AI conception rate of 40%±5% and IVF rate of 45% to 60%; grade two, higher fertility bull with an AI conception rate of 50%±5% and IVF rate of 61% to 80%; and grade three, highest fertility bull with an AI conception rate of 60%±5% and IVF rate of >80%.Conclusion: These findings reveal that IVF results can be used as a breeding index for bulls to evaluate their AI conception ability, which may shorten the time required to select bulls for breeding. Objective: Owing to the lack of a breeding index for efficient and quick fertility evaluations of Holstein bulls when using traditional or genome-wide detection methods, this study aimed to determine whether in vitro fertilization (IVF) could be used as an indicator of conception rate of artificial insemination (AI). Methods: Conventional and sexed frozen semen from nine bulls were used for IVF and AI. Results: The IVF and AI conception rates of each bull were confirmed to be positively correlated between the conventional frozen and sexed frozen semen. The correlation coefficient R values of nine bulls between IVF and AI methods were 0.73 and 0.97 for the conventional frozen and sexed frozen semen, respectively. The average conception rate of three bulls undergoing AI was 69.5% and 64.2%, 61.8% and 58.8%, and 48.2% and 46.2% in first-, second-, and third-born cows when conventional frozen and sexed frozen semen were used, respectively, which showed a positive correlation with the fertilization rate in the same parity. We propose an evaluation standard to assess the fertilization ability of bulls based on their IVF test results, which is categorized into three grades: grade one, normal fertility bull with an AI conception rate of 40%±5% and IVF rate of 45% to 60%; grade two, higher fertility bull with an AI conception rate of 50%±5% and IVF rate of 61% to 80%; and grade three, highest fertility bull with an AI conception rate of 60%±5% and IVF rate of >80%. Conclusion: These findings reveal that IVF results can be used as a breeding index for bulls to evaluate their AI conception ability, which may shorten the time required to select bulls for breeding.