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Deformation analysis of the flexspline of harmonic drive gears considering the driving speed effect using laser sensors

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Science China(Technological Sciences) 2017年第8期60卷 1175-1187页

作者： MA DongHui WU JiaNing LIU tao YAN ShaoZe State Key Laboratory of Tribology Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Accurate description of the elastic deformation of the flexspline is the foundation for optimization design of the structure and conjugate profiles of the harmonic drive gear. This paper proposed an experimental method to investigate the effect of the driving speed on the deformation characteristics of the flexspline. First, an experimental apparatus that integrates a special-fabricated micro-displacement platform and a pair of laser displacement sensors is developed, and the radial displacement of the flexspline is measured in vertical and horizontal directions. Next, the deformation analyses of the flexspline at different driving speeds are performed with our method and the conventional method, and the comparison results reveal that the radial displacement of the flexspline is actually composed of both harmonic and random components, and the amplitude decreases and tends to zero with the increase of the driving speed, especially near the closed end of the flexspline. Last, the mechanisms of the inherent multi-frequency and amplitude attenuation characteristics of the radial displacement of the flexspline are discussed. It is indicated that the impact and friction existing in the flexible bearing of the wave generator is likely responsible for the existence of the random component, and the assumption of linear distribution of the ftexspline deformation along the rotating axis is invalid under high speed condition. Our research promotes the further study on the contact-impact problem of the flexible bearing of the wave generator and the transfer characteristic of the elastic deformation of the flexspline.

关键词： harmonic drive gear flexspline radial displacement driving speed laser displacement sensor flexible bearing

Production of TiO_2 from CaTiO_3 by alkaline roasting method

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Rare Metals 2010年第2期29卷 162-167页

作者： WANG Yuanbo QI tao CHU Jinglong ZHAO Wei Graduate School of Chinese Academy of Sciences Beijing 100039 China Key laboratory of Green Process and Engineering Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 China

CaTiO3 was decomposed by alkaline roasting method for the production of *** process included alkaline roasting, water leaching and acid leaching *** the alkaline roasting step, the factors such as roasting temperature and NaOH/CaTiO3 molar ratio were investigated and 99.5% TiO2 could be extracted from *** addition, it is believed that only ion-exchange between Ca2＋ and Na＋ takes place, while the structure of TiO 32-in CaTiO3 was not destroyed during the roasting *** the acid leaching step, Ca（OH）2 could be completely leached at pH = 6-7 and Na2TiO3 was completely hydrolyzed *** crystal structure of the leached sample seemed to be affected by pH and sequent calcination ***, a flowsheet was proposed for the extraction of TiO2 from perovskite.

关键词： titanium dioxide roasting perovskite acid leaching

Influence of Temperature on the Inverse Hall-Petch Effect in Nanocrystalline Materials:Phase Field Crystal Simulation

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Acta Metallurgica Sinica(English Letters) 2014年第1期27卷 81-86页

作者： Yulong Zhao Zheng Chen Jian Long tao Yang State Key Laboratory of Solidification Processing Northwestern Polytechnical University

The influence of temperature on the inverse Hall-Petch effect in nanocrystalline （NC） materials is investigated using phase field crystal simulation method. Simulated results indicate that the inverse Hall-Petch effect in NC materials becomes weakened at low temperature. The results also show that the change in microscopic deformation mechanism with temperature variation is the main reason for the weakening of the inverse Hall-Petch effect. At elevated temperature, grain rotation and grain boundary （GB） migration seriously reduce the yield stress so that the NC materials exhibit the inverse Hall-Petch effect. However, at low temperature, both grain rotation and GB migration occur with great difficulty, instead, the dislocations nucleated from the cusp of serrated GBs become active. The lack of grain rotation and GB migration during deformation is mainly responsible for the weakening of the inverse Hall-Petch effect. Furthermore, it is found that since small grain size is favorable for GB migration, the degree of weakening decreases with decreasing average grain size at low temperature.

关键词： Phase field crystal (PFC) Nanocrystalline (NC) material Temperature Microscopic deformation mechanism Inverse Hall-Petch effect

Pressure observer based adaptive robust trajectory tracking control of a parallel manipulator driven by pneumatic muscles

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第12期8卷 1928-1937页

作者： ZHU Xiao-cong tao Guo-liang CAO Jian The State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

This paper presents a pressure observer based adaptive robust controller (POARC) for posture trajectory tracking of a parallel manipulator driven by three pneumatic muscles without pressure sensors. Due to model errors of the static forces and friction forces of pneumatic muscles, simplified average flow rate characteristics of valves, unknown disturbances of entire system, and unmeasured pressures, there exist rather severe parametric uncertainties, nonlinear uncertainties and dynamic uncertainties in modeling of the parallel manipulator. A nonlinear pressure observer is constructed to estimate unknown pressures on the basis of a single-input-single-output (SISO) decoupling model that is simplified from the actual multiple-input-multiple-output (MIMO) coupling model of the parallel manipulator. Then, an adaptive robust controller integrated with the pressure observer is developed to accomplish high precision posture trajectory tracking of the parallel manipulator. The experimental results indicate that the system with the proposed POARC not only achieves good control accuracy and smooth movement but also maintains robustness to disturbances.

关键词： Pneumatic muscle Parallel manipulator Pressure observer Adaptive robust control Trajectory tracking

Probability estimation based on grey system theory for simulation evaluation

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Journal of Systems Engineering and Electronics 2016年第4期27卷 871-877页

作者： Jianmin Wang Jinbo Wang tao Zhang Yunjie Wu Technology and Engineering Center for Space Utilization Chinese Academy of Sciences School of Automation Science and Electrical Engineering Beihang University

In the evaluation of some simulation systems, only small samples data are gotten due to the limited conditions. In allusion to the evaluation problem of small sample data, an interval estimation approach with the improved grey confidence degree is *** the basis of the definition of grey distance, three kinds of definition of the grey weight for every sample element in grey estimated value are put forward, and then the improved grey confidence degree is designed. In accordance with the new concept, the grey interval estimation for small sample data is deduced. Furthermore,the bootstrap method is applied for more accurate grey confidence interval. Through resampling of the bootstrap, numerous small samples with the corresponding confidence intervals can be obtained. Then the final confidence interval is calculated from the union of these grey confidence intervals. In the end, the simulation system evaluation using the proposed method is conducted. The simulation results show that the reasonable confidence interval is acquired, which demonstrates the feasibility and effectiveness of the proposed method.

关键词： small sample interval estimation simulation system evaluation probability grey system theory

Synthesis of azobenzene-containing liquid crystalline gelator for use in liquid crystal gels

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Chinese Chemical Letters 2008年第5期19卷 521-524页

作者： Guang Wang Xiao Liang Zhao yue Zhao Faculty of Chemistry Northeast Normal University Changchun 130024 China Department of Chemistry University of Sherbrooke Sherbrooke Canada JIK 2

A liquid crystalline gelator containing the azobenzene chromophore was synthesized for the first time; it was used to form self- assembled network in nematic liquid crystals resulting in liquid crystal gels with disti... 详细信息

关键词： Gelator Azobenzene Synthesis Liquid crystal

Influence of Al addition on solidification path and hot tearing susceptibility of Mg-2Zn-(3+0.5 x)Y-x Al alloys

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Journal of Magnesium and Alloys 2019年第2期7卷 272-282页

作者： Guojia Zhang yue Wang Zheng Liu Shimeng Liu School of Materials Science and Engineering Shenyang University of technologyShenyang 110870P.R.China

Hot tearing susceptibility(HTS)of Mg-2Zn-(3+0.5 x)Y-x Al(x=0,2 and 3 at%)alloys is predicted by using modified Clyne-Davies’model(CSC^(∗)).The solidification path,solidification characteristic temperatures and dendritic coherency solid fraction have been studied by double-thermocouple thermal *** solidification contraction stress ***(and time)curves are measured by using a“T”type hot tearing *** results reveal that the CSC^(∗)prediction values are in good agreement with the experimental ***,Al_(2)Y phase acts as the heterogeneous nucleation core ofα-Mg and significantly influences the grain *** has been observed that minimum grain size,optimal dendritic coherency and minimum HTS are exhibited by Mg-2Zn-(3+0.5 x)Y-x Al alloy(x=2).Furthermore,when Al content was increased to 3 at%,Al_(2)Y phase exhibited a peritectic reaction and transformed into a mixed structure of Al_(2)Y and Al+Al_(3)Y phases,which increased the HTS of the alloy due to reduced fine-grained Al_(2)Y content.

关键词： Mg-Zn-Y-Al alloys Hot tearing susceptibility(HTS) Solidification path Clyne-Davies’model(CSC^(∗)) Dendritic coherency

Flexible impedance sensor based on Ti_(3)C_(2)T_(x)MXene and graphitic carbon nitride nanohybrid for humidity-sensing application with ultrahigh response

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Rare Metals 2023年第7期42卷 2204-2213页

作者： Yang Lu Meng-Yu Wang Dong-yue Wang yue-Hang Sun Zi-Hao Liu Rong-Ke Gao Lian-Dong Yu Dong-Zhi Zhang College of Control Science and Engineering China University of Petroleum(East China)Qingdao266580China

This paper reported the impedance-type humidity sensor based on Ti_(3)C_(2)T_(x)/g-C_(3)N_(4)nanomaterials which was fabricated on a flexible polyethylene terephthalate(PET)*** scanning electron microscopy(SEM),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS)measurements were used to demonstrate the successful synthesis and combination of Ti_(3)C_(2)T_(x)and g-C_(3)N_(4)*** performance of the humidity sensor was tested at room *** experimental results showed that the Ti_(3)C_(2)T_(x)nanosheets with g-C_(3)N_(4)nanosheets endowed the humidity sensor with an ultra-high response,rapid response/recovery time,and negligible *** complex impedance spectroscopy(CIS)and bode diagrams were used to further analyze the sensing mechanism of the Ti_(3)C_(2)T_(x)/g-C_(3)N_(4)humidity *** Ti_(3)C_(2)T_(x)/g-C_(3)N_(4)humidity sensor can monitor skin humidity and high-humidity alarm,which demonstrates great potential applications in various fields.

关键词： Ti_(3)C_(2)T_(x)MXene Graphitic carbon nitride Flexible humidity sensor Humidity detection Alarm application

Robust and fast iterative sparse recovery method for space-time adaptive processing

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Science China(Information Sciences) 2016年第6期59卷 199-211页

作者： Xiaopeng YANG Yuze SUN tao ZENG Teng LONG Beijing Key Laboratory of Embedded Real-time Information Processing Technology School of Information and Electronics Beijing Institute of Technology

Conventional space-time adaptive processing(STAP) requires large numbers of independent and identically distributed(i.i.d) training samples to ensure the performance of clutter suppression, which is hard to be achieved in practical complex nonhomogeneous environment. In order to improve the performance of clutter suppression with small training sample support, a robust and fast iterative sparse recovery method for STAP is proposed in this paper. In the proposed method, the sparse recovery of clutter spatial-temporal spectrum and the calibration of space-time overcomplete dictionary are achieved iteratively. Firstly, the robust solution of sparse recovery is derived by regularized processing, which can be calculated recursively based on the block Hermitian matrix property, afterwards the mismatch of space-time overcomplete dictionary is calibrated by minimizing the cost function. The proposed method can not only alleviate the effect of noise and dictionary mismatch, but also reduce the computational cost caused by direct matrix inversion. Finally, the proposed method is verified based on the simulated and the actual airborne phased array radar data, which shows that the proposed method is suitable for practical complex nonhomogeneous environment and provides better performance compared with conventional STAP methods.

关键词： space-time adaptive processing(STAP) sparse recovery robust iteration computational complexity