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Kinematic Calibration and Forecast Error Compensation of a 2-DOF Planar Parallel Manipulator

Chinese Journal of Mechanical Engineering 2011年第6期24卷 992-998页

作者： CHANG Peng li chengrong li Tiemin Hi-tech Innovation Center Institute of AutomationChinese Academy of SciencesBeijing 100190China Department of Precision Instruments and Mechanology Tsinghua UniversityBeijing 100084China

Due to large workspace,heavy-duty and over-constrained mechanism,a small deformation is caused and the precision of the 2-DOF planar parallel manipulator is *** kinematic calibration cannot compensate the end-effector errors caused by the small *** paper presents a method combined step kinematic calibration and linear forecast real-time error compensation in order to enhance the precision of a two degree-of-freedom(DOF) planar parallel manipulator of a hybrid machine *** the step kinematic calibration phase of the method,the end-effector errors caused by the errors of major constant geometrical parameters is *** step kinematic calibration is based on the minimal linear combinations(MLCs) of the error *** simple and feasible measurements in practice are given,and identification analysis of the set of the MLCs for each measurement is carried *** to identification analysis results,both measurement costs and observability are considered,and a step calibration including step measurement,step identification and step error compensation is *** linear forecast real-time error compensation is used to compensate the end-effector errors caused by other parameters after the step kinematic *** the advantages of the step kinematic calibration and the linear forecast real-time error compensation,a method for improving the precision of the 2-DOF planar parallel manipulator is *** results show that the proposed method is robust and effective,so that the position errors are kept to the same order of the measurement *** presented method is attractive for the 2-DOF planar parallel manipulator and can be also applied to other parallel manipulators with fewer than six DOFs.

关键词： parallel manipulator kinematic calibration error compensation minimal linear combinations (MLCs)

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Gait Definition and Successive Gait-transition Method Based on Energy Consumption for a Quadruped

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Chinese Journal of Mechanical Engineering 2012年第1期25卷 29-37页

作者： ZHAO Danpu XU Jing WU Dan CHEN Ken li chengrong Institute of Automation Chinese Academy of SciencesBeijing 100190China Department of Precision Instruments and Mechanology Tsinghua UniversityBeijing 100084China

In nature, to realize the smooth motion for different speeds, the continuous gait transition is usually required for the quadrupeds. Thus, the gait simulation of quadrupeds is a requisite step to obtain the stable and energy-efficient gait for the walking machines. In this paper, the definitions of the two gait parameters, phasic difference and duty factor are presented, which can determine the gait of the quadrupeds. Then, several typical gaits of the quadrupeds are analyzed such that the seven standard gaits and corresponding parameters are summarized. Additionally, the variance law of the two parameters, which determine the relationship of gait transition, is analyzed. Furthermore, the quadruped gait derivative spectrum (QGDS) is proposed and the gait definition of the quadrupeds is presented. To minimize the power consumption, the choice criterion of gait, the optimal gait in terms of the motion speed, duty factory, and power consumption for the walking machines, is developed. Last, the continuous variance of the gait is implemented by the simulation of the gait transition from walk to trot, which evaluate the choice criterion and transition of gait.

关键词： gait definition standard gaits quadruped gait-transition

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Metal-free Optical Pressure Sensor with High Sensitivity and Extensive Range

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1291-1300页

作者： Mao Ji Meng Huang Haomin Lyu Sheng Shi Bo Qi chengrong li State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijing 102206China IEEE CSEE

Pressure monitoring of a transformer oil tank can grasp the pressure change process caused by gas production when severe internal defects occur and take timely measures to ensure the safe operation of the *** pressure sensors generally use metal encapsulation or have an air cavity structure,threatening the transformer’s insulation if it is directly used inside the *** this end,this paper proposes a method for developing a high-sensitivity,large-range,and metallizationfree optical pressure sensing device with temperature *** grating is encapsulated by fluorosilicone rubber and supplemented by an epoxy resin shielding shell on the *** the same time,a double-grating vertical arrangement is adopted to improve pressure measurement sensitivity,further avoiding the influence of temperature rise caused by a defect of the transformer on the measurement result of the *** addition,by optimizing the geometric structure of the internal sensitizing element,pre-stretching length of the fiber grating,gap distance,and other parameters,probe size can be reduced while ensuring the sensor’s *** show the proposed method can meet the requirements of sensor fabrication with different sensitivities and ranges,and to a certain extent,both high sensitivity and extensive ranges can be taken into *** sensitivity of the fabricated prototype is 15 pm/kPa,and the range is about 0.2 *** the same time,the metal-free feature of the sensor makes it suitable for use in various oil-immersed power *** records oil pressure changes caused by oil discharge breakdown,making it sensitive to small pressure changes in early failures.

关键词： Highly sensitive extensive range optical sensing no metallization pressure perception temperature compensation transformer

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Insulation Design Rule for a Spacer in SF_(6)/N_(2)-filled DC Gas Insulated Apparatus

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 727-735页

作者： Hongyang Zhou Guoming Ma Meng Zhang Cong Wang Youping Tu chengrong li State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources and the Beijing Key Laboratory of High Voltage and EMC North China Electric Power UniversityBeijing 102206China

A recurring challenge of a DC SF_(6)/N_(2)-filled GIS/GIL apparatus is the charge accumulation at DC *** conventional design rules and knowledge of AC spacers may not be applicable for this new type of apparatus.A novel design rule is proposed considering the effect of accumulated charge on the threshold of electric field strength being resistant to the superposed voltage.A surface charge accumulation simulation model is introduced,and the key parameters in the simulation model are *** addition,an experimental platform for a 100 kV spacer flashover test is *** flashover tests under superimposed voltage with opposing polarities are carried out,and the withstanding voltage of the spacer is ***,based on the proposed model,the threshold of the surface electric field strength(tangential component)on the DC spacer in SF_(6)/N_(2) mixed gases is *** a reliable insulation design of a DC GIS/GIL apparatus filled with 0.7 MPa SF_(6)/N_(2),the threshold of surface electric field strength on the DC spacer is 12 kV/*** insulation design rule can be referenced in the design of a high-voltage DC SF_(6)/N_(2)-filled GIS/GIL apparatus.

关键词： Charge accumulation DC spacer flashover voltage SF_(6)/N_(2) threshold of surface electric field strength

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Review of Charge Accumulation on Spacers of Gas Insulated Equipment at DC Stress

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CSEE Journal of Power and Energy Systems 2020年第3期6卷 496-517页

作者： Hongyang Zhou Guoming Ma Cong Wang Jue Wang Guixin Zhang Youping Tu chengrong li State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources and the Beijing Key Laboratory of High Voltage and EMC North China Electric Power UniversityBeijing 102206China Institute of Electrical Engineering Chinese Academy of SciencesBeijingChina Department of Electrical Engineering Tsinghua UniversityBeijing 100084China

Charge accumulation on the spacer surface in gas insulated equipment is very severe in the DC field,leading to easy flashover,which restricts the application of DC GIS/***,knowledge about the charge accumulation characteristics of gas insulated equipment at DC stress is *** this paper,we reviewed the research methods and the characteristics of charge accumulation on spacers.A summary of charge measurement methods and setups are *** the surface charge inversion algorithms are *** the simulation model for charge accumulation in the DC field is ***,the charge accumulation mechanisms and phenomenon,the influence factor of surface charge accumulation and the influence of accumulated charge on spacer insulation characteristics are *** addition,some suppression methods of surface charge accumulation are ***,based on the understanding of charge accumulation on spacers,some suggestions on further studies are presented to aid in the design of a better spacer free from surface charges.

关键词： Charge accumulation DC gas insulated equipment review spacer

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A simple method considering the synergetic effect of space charge and inhomogeneous material conductivity for DC electric field computation

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High Voltage 2022年第6期7卷 1141-1152页

作者： Xiao Yang Yi Zhang Zhuodong Yang Hao Dong chengrong li Bo Qi licheng Lu State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijingChina Global Energy Interconnection Research Institute Co. Ltd.BeijingChina

The current continuity equation is usually applied to solve DC electric field distribution when there is inhomogeneous material conductivity due to temperature gradient or multi-layer ***,in the presence of charge accumulation,which may result from the process of electrode injection,impurity ionisation or charge trapping,the material conductivity is in tangled relationship with local field strength,and the current continuity equation can be hardly applied due to the ignorance of conductivity ***,quantitative analysis on the effect of space(surface)charge for DC apparatus with inhomogeneous material conductivity has been a difficult problem,which requires a complicated physical model to *** paper has proposed a simple method to compute the synergetic influence of inhomogeneous conductivity and the space charge on the DC field distribution;through assigning bulk(interface)charge as functions of local material conductivity and field strength,the effect of inhomogeneous conductivity can be incorporated in Gauss'law and the space charge accumulation can be further included in the *** effect of space(surface)charge on electric field distribution in DC apparatus with temperature gradient as well as multiple-layer dielectrics is simulated through the proposed method,which shows that the method has offered a convenient approach for investigating the effect of charge accumulation on DC field distribution under various insulation structure and working conditions.

关键词： equation conductivity inhomogeneous

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Influence of moisture on the interface charge of oil-pressboard composite insulation under DC voltage

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High Voltage 2018年第1期3卷 73-77页

作者： Bo Qi Yanqiu Jiao Chunjia Gao Shuqi Zhang Xiaolin Zhao chengrong li State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityNo.2 Beinong RoadBeijingPeople's Republic of China Beijing Key Laboratory of High Voltage&EMC North China Electric Power UniversityNo.2 Beinong RoadBeijingPeople's Republic of China High Voltage Department China Electric Power Research InstituteNo.15 Xiaoying East RoadBeijingPeople's Republic of China

The distortion of the electric field in the oil–pressboard composite insulation caused by the accumulation of the interface charge is detrimental to both the insulation design and operation of converter *** influence of moisture content on the surface charge accumulation of oil–pressboard insulation under DC voltage was studied in this *** accordance with the Kerr electro-optic effect,the electric field strengths in transformer oil and the surface charge density were acquired after applying the positive and negative DC voltages in three oil–pressboard insulation models with different moisture content,*** resistivities of the oil and pressboard in three models,namely Model 1#with 3.8–4.2 ppm moisture in oil and 0.35–0.37%moisture in pressboard,Model 2#with 7.6–7.9 ppm moisture in oil and 0.79–0.82%moisture in pressboard and Model 3#with 14.9–15.4 ppm moisture in oil and 1.39–1.42%moisture in pressboard,was also *** results indicate that:(i)as negative charges in oil accumulated on the pressboard surface in a much greater speed than the positive ones,the electric field in transformer oil under negative DC voltage decreases more rapidly with time than that under positive DC voltage;(ii)the increase of the moisture content in both oil and pressboard,under either positive or negative DC voltage,leads to the decrease of both the electric field strength in transformer oil and the charge density with time;and(iii)the increase of moisture content could not only decrease the resistivity of both oil and pressboard,but also the ratio of the resistivity between the pressboard and the *** the basis of the Maxwell–Wagner theory,the decrease of the ratio between the pressboard and oil could lead to the decrease of the interfacial charge density,leading to the slow transient process of the electric field in transformer oil under DC voltage.

关键词： moisture insulation composite

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Enhanced voltage distribution and breakdown strength performances of oil‐paper composite insulation by adding TiO_(2)nanoparticles

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High Voltage 2021年第1期6卷 42-50页

作者： Meng Huang Yupeng Ying Baixin liu Yuzhen Lv Bo Qi chengrong li State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijingChina Beijing Key Laboratory of High Voltage&EMC North China Electric Power UniversityBeijingChina School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijingChina

Oil-paper composite insulation(OPCI)is used as the main insulation material in the converter ***,the dielectric properties of insulating oil and oil‐impregnated paper are markedly mismatched under direct current(DC)voltage,resulting in an unbalanced distribution of voltage,which is considered to be a major cause of large insulation margin but frequent ***,it is necessary to adjust the voltage distribution in OPCI to enhance its breakdown *** this work,surface‐treated TiO_(2) nanoparticles were employed to modify *** polarisation current tests revealed that by changing the additive amount of nano-particles,the polarisation intensities of both oil and oil‐impregnated paper could be *** on this,a model taking relaxation polarisations into full consideration was established to analyse the voltage distribution in OPCI and predict the optimal *** prepared OPCI with the concentration of 0.02 g/L has desired balanced voltage distribution due to the influence of nanoparticles on interface charge,and therefore high breakdown strengths under both DC voltage and polarity reversal voltage,which can be increased by 22.6%at *** work puts forward a novel idea to improve insulation property of OPCI and provides a reference for broader application of nanomaterial in power equipment.

关键词： insulation distribution breakdown

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Modelling on thermal-fluid field in SF_(6)insulated high voltage direct current bushing with its influence on electric field distribution and metal particle motion

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High Voltage 2023年第2期8卷 380-389页

作者： Xiao Yang Yi Zhang Zhuodong Yang Hao Dong chengrong li Bo Qi licheng Lu Caixin Sun State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijingChina Global Energy Interconnection Research Institute Co Ltd BeijingChina China Huaneng Group Co Ltd BeijingChina

The insulation performance of SF_(6)insulated high voltage direct current apparatus are often analysed in a pure electric field or electro-thermal coupled field while the fluid behaviour of SF_(6)gas flow is often ***,frequent flashover along the support insulators inside the SF_(6)insulated wall bushing indicates that the fluid characteristics of SF_(6)may have considerable influence on the interior insulation performance of the *** paper has simulated the thermo-fluid coupled field in the SF_(6)insulated wall bushing based on the finite element method *** result shows that buoyant flow of SF_(6)has evident influence on the temperature distribution in the *** this basis,the effect of the thermo-fluid field on the electric field distribution along the insulator as well as on the motion behaviour of the metallic particles is ***,the effect of different thermal boundary conditions on analysis of the multiphysics field in the bushing is discussed and the most suitable one for simulation and experiment is *** are made between different supporting structures and modification advices are *** paper can serve as a good reference for subsequent research studies on SF_(6)insulated apparatus in which the temperature gradient or the motion of the micro-sized metallic particles shall be considered.

关键词： distribution thermal field

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Comparison of Parameter Estimation Methods for Transformer Weibull lifetime Modelling

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高电压技术 2013年第5期39卷 1170-1177页

作者： ZHOU Dan li chengrong WANG Zhongdong Beijing Key Laboratory of High Voltage and Electromagnetic Compatability School of Electric and Electronic EngineeringNorth China Electric Power UniversityBeijing 102206China The University of Manchester Manchester M13 9PLUnited Kingdom

Two-parameter Weibull distribution is the most widely adopted lifetime model for power *** appropriate parameter estimation method is essential to guarantee the accuracy of a derived Weibull lifetime *** popular parameter estimation methods(*** maximum likelihood estimation method,two median rank regression methods including the one regressing X on Y and the other one regressing Y on X,the Kaplan-Meier method,the method based on cumulative hazard plot,and the li ’ s method) are reviewed and compared in order to find the optimal one that suits transformer ’ s Weibull lifetime *** comparison took several different scenarios into consideration : 10 000sets of lifetime data,each of which had a sampling size of 40~1 000and a censoring rate of 90%,were obtained by Monte-Carlo simulations for each *** and shape parameters of Weibull distribution estimated by the six methods,as well as their mean value,median value and 90% confidence band are *** cross comparison of these results reveals that,among the six methods,the maximum likelihood method is the best one,since it could provide the most accurate Weibull parameters,*** having the smallest bias in both mean and median values,as well as the shortest length of the 90% confidence *** maximum likelihood method is therefore recommended to be used over the other methods in transformer Weibull lifetime modelling.

关键词：电力变压器寿命模型电力技术估计方法

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