The existing research of the motion optimization of multi-axis machine tools is mainly based on geometric and kinematic constraints, which aim at obtaining minimum-time trajectories and finding obstacle-free paths. In...The existing research of the motion optimization of multi-axis machine tools is mainly based on geometric and kinematic constraints, which aim at obtaining minimum-time trajectories and finding obstacle-free paths. In motion optimization, the stiffness characteristics of the whole machining system, including machine tool and cutter, are not considered. The paper presents a new method to establish a general stiffness model of multi-axis machining system. An analytical stiffness model is established by Jacobi and point transformation matrix method. Based on the stiffness model, feed-direction stiffness index is calculated by the intersection of force ellipsoid and the cutting feed direction at the cutter tip. The stiffness index can help analyze the stiffness performance of the whole machining system in the available workspace. Based on the analysis of the stiffness performance, multi-axis motion optimization along tool paths is accomplished by mixed programming using Matlab and Visual C＋＋. The effectiveness of the motion optimization method is verified by the experimental research about the machining performance of a 7-axis 5-linkage machine tool. The proposed research showed that machining stability and production efficiency can be improved by multi-axis motion optimization based on the anisotropic force ellipsoid of the whole machining system.展开更多
The contour error was analyzed based on CNC multi-axis motion control, the contour error model was obtained focused on beeline and different radius of curvature and common contour of curve, for a CNC biaxial motion co...The contour error was analyzed based on CNC multi-axis motion control, the contour error model was obtained focused on beeline and different radius of curvature and common contour of curve, for a CNC biaxial motion control system and the mechanism of producing contour error and the relationship between tracking error and contour error were presented. The theoretical and practical significance of modeling error and controlling error in motion control systems was carried out.展开更多
When the membrane material in the air field vibrates, it will drive the movement of the surrounding air. The aerodynamic force generated by the moving air will act on the membrane material in turn, resulting in the ch...When the membrane material in the air field vibrates, it will drive the movement of the surrounding air. The aerodynamic force generated by the moving air will act on the membrane material in turn, resulting in the change of dynamic characteristics such as membrane vibration frequency. In this paper, the additional air mass produced by membrane vibration in air is studied. Firstly, under the assumption that the incoming flow is uniform and incompressible ideal potential flow, the additional air mass acting on the surface is derived by using the thin airfoil theory and potential flow theory respectively. Then, according to the first law of thermodynamics and the principle of aeroelasticity, the analytical expression of the additional air mass is derived. Finally, through a specific example, the variation of the additional air mass with the membrane material parameters and pretension, as well as the influence of the aerodynamic force on the vibration frequency and amplitude of the membrane is obtained.展开更多
A mathematical model has been developed to analyze the flow patterns and subsurface trajectories of spherical shaped particles (alloy additions) in gas stirring ladles. First, a numerical method to solve fluid flow ...A mathematical model has been developed to analyze the flow patterns and subsurface trajectories of spherical shaped particles (alloy additions) in gas stirring ladles. First, a numerical method to solve fluid flow problems in conjunction with a curvilinear coordinate system is proposed. The internal boundary in flow field, which must be designated in the cylindrical polar coordinate system, can be avoided by using body- fitted coordinate system (BFC). Consequently, computed flow of molten steel and paths of alloying additions are able to cross smoothly the geometric centerline of cylindrical vessel. Second, motion of particles is calculated in the three-dimensional coordinate system, the modification of parameters, such as the drag coefficient and density in the gas plume region, is examined. When the density of sphere is closer and closer to that of fluid, the path of motion is longer and longer. If the plug is moved off-centered to the half of radius, the path of sphere is prolonged, and the sphere may go through the geometric centerline of vessel, reach the deeper region. The immersed depths increase with increasing entry velocities.展开更多
While laser surface texturing(LST)is a promising manufacturing technique for surface functionalization,simultaneously realizing high precision and high efficiency in the LST of complex curved surface is challenging,du...While laser surface texturing(LST)is a promising manufacturing technique for surface functionalization,simultaneously realizing high precision and high efficiency in the LST of complex curved surface is challenging,due to continuously varied geometries of laser-matter incidence.In the present work,we propose a novel manufacturing system of 7-axis on-the-fly LST for complex curved surface,based on the integrated synchronization of 5-axis linkage motion platform with 2-axis galvanometer.Specifically,the algorithm for decomposing spatial texture trajectory on curved surface into low-frequency and high-frequency parts is established,based on which the kinematic model of synchronized 7-axis system is developed to derive the motion of each axis in both 5-axis linkage motion platform and 2-axis galvanometer simultaneously.Subsequently,the synchronized 7-axis LST system is experimentally realized,including the setup of mechanical stages integrated with optical path,the configuration of numerical control unit,and the development of processing software.Finally,case study of 7-axis on-the-fly LST of freeform aluminum surface is performed,and the advantages in terms of processing efficiency and texturing accuracy over 5-axis linkage LST are demonstrated.The correlation of reduced following errors between mechanical stages with the promoted performance of curved surface texturing by the 7-axis on-the-fly LST is further analyzed.Current work provides a feasible solution for establishing the manufacturing system for high performance LST of complex curved surface.展开更多
Binder jet additive manufacturing is used for producing molds and cores for sand casting,by using granular material and proper binder.The conventional system uses a layer-by-layer gantry motion.The new continuous prin...Binder jet additive manufacturing is used for producing molds and cores for sand casting,by using granular material and proper binder.The conventional system uses a layer-by-layer gantry motion.The new continuous printing machine is a helical motion system.It includes a recoating blade for the granular material which has been investigated.This study focuses on analysing the behaviour of the recoating blade when it moves in a circular or the helical motion,as well as assessing the quality of the layer surface.Discrete Element Method(DEM)simulations was conducted using various blade geometry,and the results were compared with experimental models.The input parameters of the sand material were calibrated using a reverse calibration model,which iteratively adjusts the parameter values until they match the bulk response observed in real experiments.This research study employed experimental testing and DEM modeling,initially using a normal blade to produce an annular disc,and then optimizing the blade shape to achieve full disc printing.展开更多
Approximate theorem of positive continuous additive functionals is discussed and then used to give a d-dimensional analogue to the representation of additive functiouals of one-dimensional Brownian Motion with respect...Approximate theorem of positive continuous additive functionals is discussed and then used to give a d-dimensional analogue to the representation of additive functiouals of one-dimensional Brownian Motion with respect to local time.展开更多
In the cotton factories ginning process bales of raw cotton in cotton tube transporting through the air has written in the article. As a result, cotton with cotton in the air separated by a separator device with air t...In the cotton factories ginning process bales of raw cotton in cotton tube transporting through the air has written in the article. As a result, cotton with cotton in the air separated by a separator device with air traffic, has an important theoretical study. First of all, the air flow that affects the dynamic pressure and laws is based on the model established in this study and the results are obtained.展开更多
Polar motion depicts the slow changes in the locations of the poles due to the earth's internal instantaneous axis of rotation. The LS+AR model is recognized as one of the best models for polar motion prediction.T...Polar motion depicts the slow changes in the locations of the poles due to the earth's internal instantaneous axis of rotation. The LS+AR model is recognized as one of the best models for polar motion prediction.Through statistical analysis of the time series of the LS+AR model's short-term prediction residuals,we found that there is a good correlation of model prediction residuals between adjacent terms.These indicate that the preceding model prediction residuals and experiential adjustment matrixes can be used to correct the next prediction results,thereby forming a new LS+AR model with additional error correction that applies to polar motion prediction.Simulated predictions using this new model revealed that the proposed method can improve the accuracy and reliability of polar motion prediction.In fact,the accuracies of ultra short-term and short-term predictions using the new model were equal to the international best level at present.展开更多
As the effective capture region of optical motion capture system is limited by quantity,installation mode,resolution and focus of infrared cameras,the reflective markers on certain body parts(such as wrists,elbows,etc...As the effective capture region of optical motion capture system is limited by quantity,installation mode,resolution and focus of infrared cameras,the reflective markers on certain body parts(such as wrists,elbows,etc.)of multi-actual trainees may be obscured when they perform the collaborative interactive operation.To address this issue,motion data compensation method based on the additional feature information provided by the electromagnetic spatial position tracking equipment is proposed in this paper.The main working principle and detailed realization process of the proposed method are introduced step by step,and the practical implementation is presented to illustrate its validity and efficiency.The results show that the missing capture data and motion information of relevant obscured markers on arms can be retrieved with the proposed method,which can avoid the simulation motions of corresponding virtual operators being interrupted and deformed during the collaborative interactive operation process performed by multiactual trainees with optical human motion capture system in a limited capture range.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 51075168)National Basic Research Program of China (973 Program, Grant No. 2011CB706803)National Hi-tech Research and Development Program of China (863 Program, Grant No. 2009AA04Z149)
文摘The existing research of the motion optimization of multi-axis machine tools is mainly based on geometric and kinematic constraints, which aim at obtaining minimum-time trajectories and finding obstacle-free paths. In motion optimization, the stiffness characteristics of the whole machining system, including machine tool and cutter, are not considered. The paper presents a new method to establish a general stiffness model of multi-axis machining system. An analytical stiffness model is established by Jacobi and point transformation matrix method. Based on the stiffness model, feed-direction stiffness index is calculated by the intersection of force ellipsoid and the cutting feed direction at the cutter tip. The stiffness index can help analyze the stiffness performance of the whole machining system in the available workspace. Based on the analysis of the stiffness performance, multi-axis motion optimization along tool paths is accomplished by mixed programming using Matlab and Visual C＋＋. The effectiveness of the motion optimization method is verified by the experimental research about the machining performance of a 7-axis 5-linkage machine tool. The proposed research showed that machining stability and production efficiency can be improved by multi-axis motion optimization based on the anisotropic force ellipsoid of the whole machining system.
基金supported by the Science Foundation of the Education Office of Gansu Province of Chinaunder Grant No.0914-01
文摘The contour error was analyzed based on CNC multi-axis motion control, the contour error model was obtained focused on beeline and different radius of curvature and common contour of curve, for a CNC biaxial motion control system and the mechanism of producing contour error and the relationship between tracking error and contour error were presented. The theoretical and practical significance of modeling error and controlling error in motion control systems was carried out.
文摘When the membrane material in the air field vibrates, it will drive the movement of the surrounding air. The aerodynamic force generated by the moving air will act on the membrane material in turn, resulting in the change of dynamic characteristics such as membrane vibration frequency. In this paper, the additional air mass produced by membrane vibration in air is studied. Firstly, under the assumption that the incoming flow is uniform and incompressible ideal potential flow, the additional air mass acting on the surface is derived by using the thin airfoil theory and potential flow theory respectively. Then, according to the first law of thermodynamics and the principle of aeroelasticity, the analytical expression of the additional air mass is derived. Finally, through a specific example, the variation of the additional air mass with the membrane material parameters and pretension, as well as the influence of the aerodynamic force on the vibration frequency and amplitude of the membrane is obtained.
文摘A mathematical model has been developed to analyze the flow patterns and subsurface trajectories of spherical shaped particles (alloy additions) in gas stirring ladles. First, a numerical method to solve fluid flow problems in conjunction with a curvilinear coordinate system is proposed. The internal boundary in flow field, which must be designated in the cylindrical polar coordinate system, can be avoided by using body- fitted coordinate system (BFC). Consequently, computed flow of molten steel and paths of alloying additions are able to cross smoothly the geometric centerline of cylindrical vessel. Second, motion of particles is calculated in the three-dimensional coordinate system, the modification of parameters, such as the drag coefficient and density in the gas plume region, is examined. When the density of sphere is closer and closer to that of fluid, the path of motion is longer and longer. If the plug is moved off-centered to the half of radius, the path of sphere is prolonged, and the sphere may go through the geometric centerline of vessel, reach the deeper region. The immersed depths increase with increasing entry velocities.
基金the support by the Harbin Manufacturing Science and Technology Innovation Talent Project(No.2023CXRCGD035)the Open Research Foundation of State Key Laboratory of Digital Manufacturing Equipment and Technology in Huazhong University of Science and Technology,China(No.IMETKF2023012).
文摘While laser surface texturing(LST)is a promising manufacturing technique for surface functionalization,simultaneously realizing high precision and high efficiency in the LST of complex curved surface is challenging,due to continuously varied geometries of laser-matter incidence.In the present work,we propose a novel manufacturing system of 7-axis on-the-fly LST for complex curved surface,based on the integrated synchronization of 5-axis linkage motion platform with 2-axis galvanometer.Specifically,the algorithm for decomposing spatial texture trajectory on curved surface into low-frequency and high-frequency parts is established,based on which the kinematic model of synchronized 7-axis system is developed to derive the motion of each axis in both 5-axis linkage motion platform and 2-axis galvanometer simultaneously.Subsequently,the synchronized 7-axis LST system is experimentally realized,including the setup of mechanical stages integrated with optical path,the configuration of numerical control unit,and the development of processing software.Finally,case study of 7-axis on-the-fly LST of freeform aluminum surface is performed,and the advantages in terms of processing efficiency and texturing accuracy over 5-axis linkage LST are demonstrated.The correlation of reduced following errors between mechanical stages with the promoted performance of curved surface texturing by the 7-axis on-the-fly LST is further analyzed.Current work provides a feasible solution for establishing the manufacturing system for high performance LST of complex curved surface.
文摘Binder jet additive manufacturing is used for producing molds and cores for sand casting,by using granular material and proper binder.The conventional system uses a layer-by-layer gantry motion.The new continuous printing machine is a helical motion system.It includes a recoating blade for the granular material which has been investigated.This study focuses on analysing the behaviour of the recoating blade when it moves in a circular or the helical motion,as well as assessing the quality of the layer surface.Discrete Element Method(DEM)simulations was conducted using various blade geometry,and the results were compared with experimental models.The input parameters of the sand material were calibrated using a reverse calibration model,which iteratively adjusts the parameter values until they match the bulk response observed in real experiments.This research study employed experimental testing and DEM modeling,initially using a normal blade to produce an annular disc,and then optimizing the blade shape to achieve full disc printing.
文摘Approximate theorem of positive continuous additive functionals is discussed and then used to give a d-dimensional analogue to the representation of additive functiouals of one-dimensional Brownian Motion with respect to local time.
文摘In the cotton factories ginning process bales of raw cotton in cotton tube transporting through the air has written in the article. As a result, cotton with cotton in the air separated by a separator device with air traffic, has an important theoretical study. First of all, the air flow that affects the dynamic pressure and laws is based on the model established in this study and the results are obtained.
基金supported by the National Natural Science Foundation of China(Grant Nos.41021061&41174012)
文摘Polar motion depicts the slow changes in the locations of the poles due to the earth's internal instantaneous axis of rotation. The LS+AR model is recognized as one of the best models for polar motion prediction.Through statistical analysis of the time series of the LS+AR model's short-term prediction residuals,we found that there is a good correlation of model prediction residuals between adjacent terms.These indicate that the preceding model prediction residuals and experiential adjustment matrixes can be used to correct the next prediction results,thereby forming a new LS+AR model with additional error correction that applies to polar motion prediction.Simulated predictions using this new model revealed that the proposed method can improve the accuracy and reliability of polar motion prediction.In fact,the accuracies of ultra short-term and short-term predictions using the new model were equal to the international best level at present.
基金the project supported by the National Natural Science Foundation of China(Grant No.61702524)the Natural Science Foundation of Shaanxi Province(Grant No.2016JQ6052).
文摘As the effective capture region of optical motion capture system is limited by quantity,installation mode,resolution and focus of infrared cameras,the reflective markers on certain body parts(such as wrists,elbows,etc.)of multi-actual trainees may be obscured when they perform the collaborative interactive operation.To address this issue,motion data compensation method based on the additional feature information provided by the electromagnetic spatial position tracking equipment is proposed in this paper.The main working principle and detailed realization process of the proposed method are introduced step by step,and the practical implementation is presented to illustrate its validity and efficiency.The results show that the missing capture data and motion information of relevant obscured markers on arms can be retrieved with the proposed method,which can avoid the simulation motions of corresponding virtual operators being interrupted and deformed during the collaborative interactive operation process performed by multiactual trainees with optical human motion capture system in a limited capture range.
