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Research on Nonlinear Friction Compensation of Harmonic Drive in Gimbal Servo-system of DGCMG
Bangcheng Han,Haitao Li,Jijun Ma 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.3
The purpose of this paper is to present our results in overcoming the influence of the nonlinear frictionafforded by harmonic drive to the gimbal servo-system of double-gimbal control momentum gyro (DGCMG). Theexistence of compliance and oscillation inherent in harmonic drive systems, and the lack of any technical informationon the internal dynamics of the transmission, make the development of friction compensation in harmonic drivesystem extremely challenging. In this paper, the modeling of nonlinear friction in harmonic drive gear transmissionin gimbal servo-system of the DGCMG is proposed. The relationship among the nonlinear friction, the angularvelocity and the angular position with an improved Coulomb-Viscous model is derived, and the experiments toidentify the various parameters of the improved model are given. At last a feed-forward compensation controllerbased on the improved model is designed to carry out the friction compensation study.
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Xing Li,Hong-Liang Lu,Hong-Ping Ma,Jian-Guo Yang,Jin-Xin Chen,Wei Huang,Qixin Guo,Jijun Feng,David Wei Zhang 한국물리학회 2019 Current Applied Physics Vol.19 No.2
Thin Ga2O3 films were grown on Si (100) using trimethylgallium (TMG) and oxygen as the precursors through plasma-enhanced atomic layer deposition. The depositions were made over a temperature range of 80–250 °C with a growth per cycle of around 0.07 nm/cycle. Surface self-saturating growth was obtained with TMG pulse time ≥20 ms at a temperature of 150 °C. The root mean square surface roughness of the obtained Ga2O3 films increased from 0.1 nm to 0.3 nm with increasing the growth temperature. Moreover, the x-ray photoelectron spectroscopy analysis indicated that the obtained film was Ga-rich with the chemical oxidation states Ga3+ and Ga1+, and no carbon contamination was detected in the films after Ar+ sputtering. The electron density of films measured by x-ray reflectivity varied with the growth temperature, increasing from 4.72 to 5.80 g/cm3 . The transmittance of Ga2O3 film deposited on a quartz substrate was obtained through ultraviolet visible (UV–Vis) spectroscopy. An obvious absorption in the deep UV region was demonstrated with a wide band gap of 4.6–4.8 eV. The spectroscopic ellipsometry analysis indicated that the average refractive index of the Ga2O3 film was 1.91 at 632.8 nm and increased with the growth temperature due to the dense structure of the films. Finally, the I-V and C-V characteristics proved that the Ga2O3 films prepared in this work had a low leakage current of 7.2 × 10−11 A/cm2 at 1.0 MV/cm and a high permittivity of 11.9, suitable to be gate dielectric.
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Huixin Xiu,Yang Zhang,Jiajia Fu,Zhanhong Ma,Lixia Zhao,Jijun Feng 한국물리학회 2019 Current Applied Physics Vol.19 No.1
Degradation mechanism of 265-nm deep ultraviolet light emitting diodes (UV-LEDs) has been investigated by means of electroluminescence, current-voltage measurement, capacitance-voltage measurement, and transmission electron microscopy (TEM) equipped with energy dispersive X-ray spectrometer (EDAX). It is revealed that a major degradation mode of UV-LEDs may be the leakage current induced optical degradation. The current pathway is demonstrated by TEM with EDAX, indicating that the contact metals can partially interact with ptype materials, which accelerate the degradation of LEDs. The presented results can help to understand the degradation mechanisms and improve the reliability of deep UV-LEDs.
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