Serial robots are used to handle workpieces with large dimensions, and calibrating kinematic parameters is one of the most efficient ways to upgrade their accuracy. Many models are set up to investigate how many kinem...Serial robots are used to handle workpieces with large dimensions, and calibrating kinematic parameters is one of the most efficient ways to upgrade their accuracy. Many models are set up to investigate how many kinematic parameters can be identified to meet the minimal principle, but the base frame and the kinematic parameter are indistinctly calibrated in a one-step way. A two-step method of calibrating kinematic parameters is proposed to improve the accuracy of the robot's base frame and kinematic parameters. The forward kinematics described with respect to the measuring coordinate frame are established based on the product- of-exponential (POE) formula. In the first step the robot's base coordinate frame is calibrated by the unit quaternion form. The errors of both the robot's reference configuration and the base coordinate frame's pose are equivalently transformed to the zero-position errors of the robot's joints. The simplified model of the robot's positioning error is established in second-power explicit expressions. Then the identification model is finished by the least square method, requiring measuring position coordinates only. The complete subtasks of calibrating the robot' s 39 kinematic parameters are finished in the second step. It's proved by a group of calibration experiments that by the proposed two-step calibration method the average absolute accuracy of industrial robots is updated to 0.23 mm. This paper presents that the robot's base frame should be calibrated before its kinematic parameters in order to upgrade its absolute positioning accuracy.展开更多
In order to realize high precision industrial operations,based on the POE formula,an effective approach to calibrate the robot's actual base frame(ABF) is proposed. Due to the existence of manufacturing errors,the...In order to realize high precision industrial operations,based on the POE formula,an effective approach to calibrate the robot's actual base frame(ABF) is proposed. Due to the existence of manufacturing errors,the ABF deviates slightly from nominal base frame( NBF). Using external precision measurement,the ABF can be established only through the three dimension(3D) position of the robot's end-effector.To ensure the orthonormal constraints of rotation matrix as well as the precise solutions,Procrustes Analysis is introduced,where an optimal orthogonal matrix is solved out by the Lagrange Multiplier method and Singular Value Decomposition(SVD). Furthermore,calibration experiment on a serial 6-DOF robot is performed,where a FARO laser tracker is utilized to measure the 3D position. Finally, calibration result indicates that the positioning accuracy has been significantly improved after calibration. The calibration method is also applicable to other similar problems,such as multi-robot coordination and robot hand-eye system calibration.展开更多
In this paper,a fast approach to generate time optimal and smooth trajectory has been developed and tested.Minimum time is critical for the productivity in industrial applications.Meanwhile,smooth trajectories based o...In this paper,a fast approach to generate time optimal and smooth trajectory has been developed and tested.Minimum time is critical for the productivity in industrial applications.Meanwhile,smooth trajectories based on cubic splines are desirable for their ability to limit vibrations and ensure the continuity of position,velocity and acceleration during the robot movement.The main feature of the approach is a satisfactory solution that can be obtained by a local modification process among each interval between two consecutive via-points.An analytical formulation simplifies the approach to smooth trajectory and few iterations are enough to determine the correct values.The approach can be applied in many robot manipulators which require high performance on time and smooth.The simulation and application of the approach on a palletizer robot are performed,and the experimental results provide evidence that the approach can realize the robot manipulators more efficiency and high smooth performance.展开更多
In this work,we have developed a new method for manipulating and transferring up to 5 mm×10 mm epitaxial oxide thin films.The method involves fixing a PET frame onto a PMMA attachment film,enabling transfer of ep...In this work,we have developed a new method for manipulating and transferring up to 5 mm×10 mm epitaxial oxide thin films.The method involves fixing a PET frame onto a PMMA attachment film,enabling transfer of epitaxial films lifted-off by wet chemical etching of a Sr3Al2O6 sacrificial layer.The crystallinity,surface morphology,continuity,and purity of the films are all preserved in the transfer process.We demonstrate the applicability of our method for three different film compositions and structures of thickness~100 nm.Furthermore,we show that by using epitaxial nanocomposite films,lift-off yield is improved by~50% compared to plain epitaxial films and we ascribe this effect to the higher fracture toughness of the composites.This work shows important steps towards large-scale perovskite thin-film-based electronic device applications.展开更多
The installation of wind energy has increased rapidly around the world. The grid codes about the wind energy require wind turbine (WT) has the ability of fault (or low voltage) ride-through (FRT). To study the FRT ope...The installation of wind energy has increased rapidly around the world. The grid codes about the wind energy require wind turbine (WT) has the ability of fault (or low voltage) ride-through (FRT). To study the FRT operation of the wind farms, three methods were discussed. First, the rotor short current of doubly-fed induction generator (DFIG) was limited by introducing a rotor side protection circuit. Second, the voltage of DC bus was limited by a DC energy absorb circuit. Third, STATCOM was used to increase the low level voltages of the wind farm. Simulation under MATLAB was studied and the corresponding results were given and discussed. The methods proposed in this paper can limit the rotor short current and the DC voltage of the DFIG WT to some degree, but the voltage support to the power system during the fault largely depend on the installation place of STATCOM.展开更多
Mathematical simulation method can be adopted to check flight characteristic of UAV, also can be adopted to simulate hardware experiments of unmanned aerial vehicle (UAV), then related flight experiments can be perfor...Mathematical simulation method can be adopted to check flight characteristic of UAV, also can be adopted to simulate hardware experiments of unmanned aerial vehicle (UAV), then related flight experiments can be performed. The simulation method can reduce the flight periods, cost and risk. UAV flight model research play an important role in simulation and modeling in initialize periods of the UAV producing. The study of the paper focuses on the aerodynamic force modeling work of UAV based on Simulink. The designed model not only can afford mathematics simulation experiment but also will do benefits to the research of flight control, navigation guidance of UAV.展开更多
Herein,melt-quenching and Er^(3+) doping were used to synthesize fluoride glass specimens with low phonon energies(582 cm^(-1)).These glass specimens exhibit intense 3.1 μm mid-infrared band emission when they are ex...Herein,melt-quenching and Er^(3+) doping were used to synthesize fluoride glass specimens with low phonon energies(582 cm^(-1)).These glass specimens exhibit intense 3.1 μm mid-infrared band emission when they are excited by a 980 nm laser diode,achieving a full width at half maximum(FWHM) of about166 nm.This 3.1 μm emission intensity is enhanced by the introduction of ZnF_(2) to the AlF_(3)-based fluoride glass.Up-conversion emission,strong near-infrared emission,and fluorescence lifetime are enhanced to different degrees by increasing the ZnF_(2) content.Moreover,the spectroscopic characteristics of the glass specimens and the highly efficient Er^(3+):~4S_(3/2)→~4F_(9/2) transition's energy transfer mechanism were investigated.The absorption spectra and emission spectra of these aluminum fluoride glass specimens were used to calculate their gain coefficients and maximum cross sections at 1.5 and 3.1 μm.Overall,the spectral properties of these prepared aluminum fluoride glass specimens demonstrate their high potential for use as infrared laser host materials.展开更多
Ce_(2)Fe_(14)B作为一种基于广泛而廉价的稀土(铈)的新型永磁体,低矫顽力和低最大磁能积严重限制了其在永磁领域中的应用.在这项工作中,我们报道了一种将熔融纺丝技术和电子束曝光(EBE)技术结合的新方法,旨在制造高性能Ce-Fe-B磁体.值...Ce_(2)Fe_(14)B作为一种基于广泛而廉价的稀土(铈)的新型永磁体,低矫顽力和低最大磁能积严重限制了其在永磁领域中的应用.在这项工作中,我们报道了一种将熔融纺丝技术和电子束曝光(EBE)技术结合的新方法,旨在制造高性能Ce-Fe-B磁体.值得注意的是,该方法可以在不使用任何其他重稀土元素的情况下调控出合适的晶界构型.在最佳EBE条件下,纯Ce-Fe-B合金的最大磁能积为6.5 MGOe,比常规快速热处理方法制备的合金的最大磁能积高四倍左右.这说明,使用EBE制备的Ce Fe B材料作为前驱体,经过进一步加工之后,如热变形或烧结,有望填补六角铁氧体与Nd-Fe-B磁体之间的市场空白.展开更多
基金Supported by State Key Lab of Digital Manufacturing Equipment & Technology(Grant No.DMETKF2015013)National Natural Science Foundation of China(Grant No.51305008)
文摘Serial robots are used to handle workpieces with large dimensions, and calibrating kinematic parameters is one of the most efficient ways to upgrade their accuracy. Many models are set up to investigate how many kinematic parameters can be identified to meet the minimal principle, but the base frame and the kinematic parameter are indistinctly calibrated in a one-step way. A two-step method of calibrating kinematic parameters is proposed to improve the accuracy of the robot's base frame and kinematic parameters. The forward kinematics described with respect to the measuring coordinate frame are established based on the product- of-exponential (POE) formula. In the first step the robot's base coordinate frame is calibrated by the unit quaternion form. The errors of both the robot's reference configuration and the base coordinate frame's pose are equivalently transformed to the zero-position errors of the robot's joints. The simplified model of the robot's positioning error is established in second-power explicit expressions. Then the identification model is finished by the least square method, requiring measuring position coordinates only. The complete subtasks of calibrating the robot' s 39 kinematic parameters are finished in the second step. It's proved by a group of calibration experiments that by the proposed two-step calibration method the average absolute accuracy of industrial robots is updated to 0.23 mm. This paper presents that the robot's base frame should be calibrated before its kinematic parameters in order to upgrade its absolute positioning accuracy.
基金Sponsored by the Applied Major Research Program of Science and Technology Commission Foundation of Beijing(Grant No.141100003514003)
文摘In order to realize high precision industrial operations,based on the POE formula,an effective approach to calibrate the robot's actual base frame(ABF) is proposed. Due to the existence of manufacturing errors,the ABF deviates slightly from nominal base frame( NBF). Using external precision measurement,the ABF can be established only through the three dimension(3D) position of the robot's end-effector.To ensure the orthonormal constraints of rotation matrix as well as the precise solutions,Procrustes Analysis is introduced,where an optimal orthogonal matrix is solved out by the Lagrange Multiplier method and Singular Value Decomposition(SVD). Furthermore,calibration experiment on a serial 6-DOF robot is performed,where a FARO laser tracker is utilized to measure the 3D position. Finally, calibration result indicates that the positioning accuracy has been significantly improved after calibration. The calibration method is also applicable to other similar problems,such as multi-robot coordination and robot hand-eye system calibration.
文摘In this paper,a fast approach to generate time optimal and smooth trajectory has been developed and tested.Minimum time is critical for the productivity in industrial applications.Meanwhile,smooth trajectories based on cubic splines are desirable for their ability to limit vibrations and ensure the continuity of position,velocity and acceleration during the robot movement.The main feature of the approach is a satisfactory solution that can be obtained by a local modification process among each interval between two consecutive via-points.An analytical formulation simplifies the approach to smooth trajectory and few iterations are enough to determine the correct values.The approach can be applied in many robot manipulators which require high performance on time and smooth.The simulation and application of the approach on a palletizer robot are performed,and the experimental results provide evidence that the approach can realize the robot manipulators more efficiency and high smooth performance.
基金Cambridge Trust and China Scholarship Councilthe support from the UK Royal Academy of Engineering,grant CiET1819_24,EPSRC grants EP/L011700/1,EP/N004272/1,EP/P007767/1(CAM-IES),and EP/T012218/1。
文摘In this work,we have developed a new method for manipulating and transferring up to 5 mm×10 mm epitaxial oxide thin films.The method involves fixing a PET frame onto a PMMA attachment film,enabling transfer of epitaxial films lifted-off by wet chemical etching of a Sr3Al2O6 sacrificial layer.The crystallinity,surface morphology,continuity,and purity of the films are all preserved in the transfer process.We demonstrate the applicability of our method for three different film compositions and structures of thickness~100 nm.Furthermore,we show that by using epitaxial nanocomposite films,lift-off yield is improved by~50% compared to plain epitaxial films and we ascribe this effect to the higher fracture toughness of the composites.This work shows important steps towards large-scale perovskite thin-film-based electronic device applications.
文摘The installation of wind energy has increased rapidly around the world. The grid codes about the wind energy require wind turbine (WT) has the ability of fault (or low voltage) ride-through (FRT). To study the FRT operation of the wind farms, three methods were discussed. First, the rotor short current of doubly-fed induction generator (DFIG) was limited by introducing a rotor side protection circuit. Second, the voltage of DC bus was limited by a DC energy absorb circuit. Third, STATCOM was used to increase the low level voltages of the wind farm. Simulation under MATLAB was studied and the corresponding results were given and discussed. The methods proposed in this paper can limit the rotor short current and the DC voltage of the DFIG WT to some degree, but the voltage support to the power system during the fault largely depend on the installation place of STATCOM.
文摘Mathematical simulation method can be adopted to check flight characteristic of UAV, also can be adopted to simulate hardware experiments of unmanned aerial vehicle (UAV), then related flight experiments can be performed. The simulation method can reduce the flight periods, cost and risk. UAV flight model research play an important role in simulation and modeling in initialize periods of the UAV producing. The study of the paper focuses on the aerodynamic force modeling work of UAV based on Simulink. The designed model not only can afford mathematics simulation experiment but also will do benefits to the research of flight control, navigation guidance of UAV.
基金Project supported by Shanghai Sailing Program from Science and Technology Committee of Shanghai (21YF1416200)。
文摘Herein,melt-quenching and Er^(3+) doping were used to synthesize fluoride glass specimens with low phonon energies(582 cm^(-1)).These glass specimens exhibit intense 3.1 μm mid-infrared band emission when they are excited by a 980 nm laser diode,achieving a full width at half maximum(FWHM) of about166 nm.This 3.1 μm emission intensity is enhanced by the introduction of ZnF_(2) to the AlF_(3)-based fluoride glass.Up-conversion emission,strong near-infrared emission,and fluorescence lifetime are enhanced to different degrees by increasing the ZnF_(2) content.Moreover,the spectroscopic characteristics of the glass specimens and the highly efficient Er^(3+):~4S_(3/2)→~4F_(9/2) transition's energy transfer mechanism were investigated.The absorption spectra and emission spectra of these aluminum fluoride glass specimens were used to calculate their gain coefficients and maximum cross sections at 1.5 and 3.1 μm.Overall,the spectral properties of these prepared aluminum fluoride glass specimens demonstrate their high potential for use as infrared laser host materials.
基金supported by the National Key Research and Development Program of China (2016YFB0700901)the National Natural Science Foundation of China (51731001, 11675006 and 51371009)financial support from the China Scholarship Council (CSC) by a State Scholarship Fund (201906010220)support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, SEV-2016-0686)
文摘Ce_(2)Fe_(14)B作为一种基于广泛而廉价的稀土(铈)的新型永磁体,低矫顽力和低最大磁能积严重限制了其在永磁领域中的应用.在这项工作中,我们报道了一种将熔融纺丝技术和电子束曝光(EBE)技术结合的新方法,旨在制造高性能Ce-Fe-B磁体.值得注意的是,该方法可以在不使用任何其他重稀土元素的情况下调控出合适的晶界构型.在最佳EBE条件下,纯Ce-Fe-B合金的最大磁能积为6.5 MGOe,比常规快速热处理方法制备的合金的最大磁能积高四倍左右.这说明,使用EBE制备的Ce Fe B材料作为前驱体,经过进一步加工之后,如热变形或烧结,有望填补六角铁氧体与Nd-Fe-B磁体之间的市场空白.