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Yazhou Sun,Quanhui Wu,Wanqun Chen,Xichun Luo,Guoda Chen 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.1
Air bearing spindles (ABS) can meet high accuracy demands for the precise rotation motion, which adopt air bearings to support spindle shaft, and the spindle shaft directly connects the motor rotor. The unbalanced electromagnetic force caused by motor rotor eccentricity (MRE) and air pressure fluctuation (APF) are two important influential factors to the dynamic performance of the spindle system and machining surface quality. This paper addresses the problems of measuring the MRE and APF in an ABS through testing machining surface topography. A permanent magnet synchronous motor (PMSM) was modelled by finite element simulation (FES). Through FES it found that the MRE between the motor rotor and stator hole produced a radial magnetic force (RMF), which could cause ABS to periodically vibrate in the axial direction. Besides, the change of the air supply caused the stiff ness variation of ABS and result in the tilt error motions of the spindle shaft. A theoretical model of machining surface topography considering MRE and APF was then proposed for the first time, which revealed that the MRE and APF resulted in the periodic fluctuations of the machining surface topography. The overall surface topography then became grooved surfaces. The above findings were finally validated by measurement results of ultraprecision diamond turning experiments.
Yazhou Tian,Yuangong Sun,Fanwei Meng 제어로봇시스템학회 2017 제어로봇시스템학회 국제학술대회 논문집 Vol.2017 No.10
The state estimation for switched systems with nonlinear disturbances and the bounded exogenous input is investigated in this paper. By using the generalized Gronwall-Bellman inequality, we obtain some estimation results for the solutions of the systems under arbitrary switching laws, which extend some existing results in the literature to the more general nonlinear case. Finally, an example is provided to illustrate the effectiveness of our results.
Stability of switched positive homogeneous nonlinear systems with mode-dependent average dwell time
Yazhou Tian,Yuangong Sun 제어로봇시스템학회 2018 제어로봇시스템학회 국제학술대회 논문집 Vol.2018 No.10
This paper addresses stability of switched positive nonlinear systems (SPNS) by using mode-dependent average dwell time (MDADT) approach. Compared with the average dwell time (ADT) switching, the switching signal used in this paper is more general, which allows each mode has its own average dwell time. Based on non-Lyapunov function method in terms of positive system, several stability criteria are derived. An example is given to illustrate the effectiveness of the theoretical results.
Sun Chuang,Li Wei,Li Yanhong,Chen Jian,An Huixian,Zeng Guangwei,Wang Tingting,Guo Yazhou,Wang Changying 대한면역학회 2022 Immune Network Vol.22 No.6
Exosomes derived from mesenchymal stem cells (MSCs) could protect against myocardial infarction (MI). TLR4 is reported to play an important role in MI, while microRNA-182-5p (miR-182-5p) negatively regulates TLR4 expression. Therefore, we hypothesize that MSCs-derived exosomes overexpressing miR-182-5p may have beneficial effects on MI. We generated bone marrow mesenchymal stem cells (BM-MSCs) and overexpressed miR-182-5p in these cells for exosome isolation. H2O2-stimulated neonatal mouse ventricle myocytes (NMVMs) and MI mouse model were employed, which were subjected to exosome treatment. The expression of inflammatory factors, heart function, and TLR4 signaling pathway activation were monitored. It was found that miR-182-5p decreased TLR4 expression in BM-MSCs and NMVMs. Administration of exosomes overexpressing miR-182-5p to H2O2-stimulated NMVMs enhanced cell viability and suppressed the expression of inflammatory cytokines. In addition, they promoted heart function, suppressed inflammatory responses, and de-activated TLR4/NF-κB signaling pathway in MI mice. In conclusion, miR-182-5p transferred by the exosomes derived from BM-MSCs protected against MI-induced impairments by targeting TLR4.
An Mechatronics Coupling Design Approach for Aerostatic Bearing Spindles
Quanhui Wu,Yazhou Sun,Wanqun Chen,Haitao Liu,Xichun Luo 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.7
In this paper, a new design approach for aerostatic bearing spindles (ABS) is firstly proposed which takes into account of the interactions between the mechanical and the servo subsystems, including the integration of electromagnetic effects, static pressure characteristics, servo control and mechanical characteristics. According to the air bearing design principle, the geometry of the spindle rotor is designed. The fluid software is used to analyze the influence of the bearing capacity and stiffness on the stability of the spindle. The simulation shows when the air film thickness is 12 μm, the bearing has good load carrying capacity and rigidity. In addition, the influence of motor harmonics on the spindle shaft modes is considered to avoid the resonance of ABS, and to ensure ABS anti-interference capability, proper inertia of ABS is calculated and analyzed. Finally, ABS has a good follow-up effect on the servo control and machining performance through the experimental prototype. The electromechanical coupling design approach for ABS proposed in this paper, can achieve a peak value better than 0.8 μm (surface size: 9 mm × 9 mm) and a surface roughness better than 8 nm in end face turning experiments.