Today city planners are confronted with two global trends:on one hand,living space is getting less due to urbanization;on the other hand,demands on living space are constantly rising as for example through stricter cl...Today city planners are confronted with two global trends:on one hand,living space is getting less due to urbanization;on the other hand,demands on living space are constantly rising as for example through stricter climate and energy political objectives based on the Paris Agreement.Therefore,it will be necessary to take into account—near urban planning and social aspects—also the climate compatibility as one central aspect in the construction of buildings,settlements,districts or neighborhoods.To identify and to push successful concepts,Austria has developed a planning tool that allows planning,assessing and ensuring high quality standards of neighborhoods.As the tool has been highly successful,additional planning tools are being developed for specific topics such as“PED—Positive Energy Districts”,“NEB—New European Bauhaus”and“CND—Climate Neutral Districts”.Central quantitative and qualitative criteria—which have been elaborated in the recent years—will be presented in this paper.展开更多
The historic centres revitalization addresses the challenges related to the preservation of fundamental heritage values. At a time, when everyone looks with concern to our cities＇ future, it is important to reflect o...The historic centres revitalization addresses the challenges related to the preservation of fundamental heritage values. At a time, when everyone looks with concern to our cities＇ future, it is important to reflect on the received heritage, seeking the most appropriate answers to the planning of the historic centres. These fabrics are reference places in the urban space, due to their role of memorial testimony and of generators of cultural and economic dynamics. However, often times, inherited urban fabrics are affected by the limitations of the heritage policies which, for being too general and based on theoretical and abstract frameworks, have difficulty incorporating the characteristics of each area and neglect the formulation of specific criteria and intervention methods. The purpose of this paper is to provide a comparative reading of the levels of urban renewal allowed by the planning tools. This study chooses two historic centers in Portugal： Oporto and Guimarfies historic centres （World Heritage Sites since 1996 and 2001, respectively, and were the last to get this classification in Portugal）. This reflection is a contribution to peer trends and raise the discussion on the role that the different heritage policies have to the revitalization of the historic centres.展开更多
Trochoidal milling is known for its advantages in machining difficult-to-machine materials as it facilitates chip removal and tool cooling.However,the conventional trochoidal tool path presents challenges such as lowe...Trochoidal milling is known for its advantages in machining difficult-to-machine materials as it facilitates chip removal and tool cooling.However,the conventional trochoidal tool path presents challenges such as lower machining efficiency and longer machining time due to its time-varying cutter-workpiece engagement angle and a high percentage of non-cutting tool paths.To address these issues,this paper introduces a parameter-variant trochoidal-like(PVTR)tool path planning method for chatter-free and high-efficiency milling.This method ensures a constant engagement angle for each tool path period by adjusting the trochoidal radius and step.Initially,the nonlinear equation for the PVTR toolpath is established.Then,a segmented recurrence method is proposed to plan tool paths based on the desired engagement angle.The impact of trochoidal tool path parameters on the engagement angle is analyzed and coupled this information with the milling stability model based on spindle speed and engagement angle to determine the desired engagement angle throughout the machining process.Finally,several experimental tests are carried out using the bull-nose end mill to validate the feasibility and effectiveness of the proposed method.展开更多
The problem of finished surface being not first-order continuous commonly exists in machining sculptured surfaces with a torus cutter and some other types of cutters. To solve this problem, a dual drive curve tool pat...The problem of finished surface being not first-order continuous commonly exists in machining sculptured surfaces with a torus cutter and some other types of cutters. To solve this problem, a dual drive curve tool path planning method is proposed in this article. First, the maximum machining strip width of a whole tool path can be obtained through optimizing each tool position with multi-point machining （MPM） method. Second, two drive curves are then determined according to the obtained maximum machining strip width. Finally, the tool is positioned once more along the dual drive curve under the condition of tool path smoothness. A computer simulation and cutting experiments are carried out to testify the performance of the new method. The machined surface is measured with a coordinate measuring machine （CMM） to examine the machining quality. The results obtained show that this method can effectively eliminate sharp scallops between adjacent tool paths, keep tool paths smooth, and improve the surface machining quality as well as machining efficiency.展开更多
Based on the object oriented data structure of Voronoi diagram, the algorithm of the trimmed offset generating and the optimal too l path planning of the pocket machining for multiply connected polygonal domains are ...Based on the object oriented data structure of Voronoi diagram, the algorithm of the trimmed offset generating and the optimal too l path planning of the pocket machining for multiply connected polygonal domains are studied. The intersection state transition rule is improved in this algorithm. The intersection is between the trimmed offsets and Voronoi polygon. On this basis, the trimmed offset generating and the optimal tool path planning are mad e with three stacks(I stack, C stack and P stack)in different monotonous pouches of Voronoi diagram. At the same time, a merging method of Voronoi diagram an d offsets generating for multiply connected polygonal domains is also presented. The above algorithms have been implemented in NC machining successfully, and the efficiency is fully verified.展开更多
The expression didactic innovation has recently assumed an implicit reference to Distance Learning.For scholars,however,it was above all the critical questioning on learning models.The article explores the use of the ...The expression didactic innovation has recently assumed an implicit reference to Distance Learning.For scholars,however,it was above all the critical questioning on learning models.The article explores the use of the podcast as a stimulus for engineering students to achieve new soft skills:to learn multidisciplinary contents related to planning and to acquire professional competences in digital aspects and feedbacks attribution.Experience took place over two years:this gave the opportunity to compare the activity carried out totally in presence and totally remotely(through online lessons and reviews),to draw from them issues for discussion and future implementations.展开更多
For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be...For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be confined to the boundary of feasible domains.In this paper,according to the principle demanding that the tool should be fitted to a surface as close as possible and relevant processing parameters,a feasible domain of tool orientation for each cutter contact is planned in the local feed coordinates system.Then,these feasible domains of the tool orientation are transformed into the same coordinates system of the machine tool by the inverse kinematics transformation.The linear equations based feasible domain method and Rosen gradient projection algorithm are used to improve the optimization process in precision and efficiency of the algorithm.It constructs the variation of tool orientation optimization model and ensures the smoothness of tool orientation globally.Simulation and analysis of examples show that the proposed method has good kinematics performance and greatly improves the efficiency.展开更多
Objective:In robot-assisted minimally invasive surgery,proper port positioning ensures that surgical tools have adequate access to the surgical site and avoids mid-surgery collisions of robotic arms.To date,several gu...Objective:In robot-assisted minimally invasive surgery,proper port positioning ensures that surgical tools have adequate access to the surgical site and avoids mid-surgery collisions of robotic arms.To date,several guidelines have been proposed for more accurate port placement.However,challenges remain due to variations in patient morphology,anatomy,and,in particular,organ displacement due to insuf-flation in certain laparoscopic procedures.The objective of this study was to design and develop a de-cision aid for optimal port placement in robot-assisted hysterectomy that accounts for patient variability and organ displacement due to insufflation.Methods:Three components were constructed:a robot model,a patient-specific model,and an opti-mization algorithm.The three components were integrated,and the system was verified using four different patients who underwent robotic hysterectomy.Once verified,two expert surgeons were asked to evaluate the decision aid for face and construct validity.A usability test was conducted using a torso phantom with target organs located in three different locations.Two expert surgeons performed a simulated hysterectomy task with and without the decision aid to evaluate performance and satisfaction.Results:The optimization algorithm was sensitive to individual differences in anatomy in the four pa-tients.Expert surgeons successfully established face and construct validity.Usability test results showed a 28%-40% reduction in time to task completion with the optimized ports compared to expert-determined port locations without using the decision aid.Conclusions:The decision aid,based on an individualized patient-specific model,robot model,and optimization algorithm,was shown to be effective at addressing the challenges of displaced organs due to insufflation in robot-assisted hysterectomy.The face and construct validity of the decision aid was established by expert surgeons,while efficiency gains in task performance were demonstrated experimentally.展开更多
Motivated by the definition of the machining errors induced by tool path planning methods, a mapping curve of the tool axis of a cylindrical cutter is constructed on the tool surface. The mapping curve is a typical on...Motivated by the definition of the machining errors induced by tool path planning methods, a mapping curve of the tool axis of a cylindrical cutter is constructed on the tool surface. The mapping curve is a typical one that can be used to express the closeness between the tool surface and the surface to be machined. A novel tool path planning method is proposed for flank or plunge milling ruled surfaces based on the minimization of the one-sided Hausdorff distance （HD） from the mapping curve to the surface to be machined. It is a nonlinear optimization problem in best uniform approximation （BUA） or Chebyshev sense. A mathematical programming model for computing the minimum one-sided HD is proposed. The linearization method of the programming model is provided and the final optimal solutions are obtained by simplex method. The effectiveness of the proposed BUA method is verified by two numerical examples and compared with the least squares （LS） and double point offset （DPO） methods. The variation in tool orientation induced by the optimization of the tool positions is also evaluated.展开更多
Tool path generation is a fundamental problem in 5-axis CNC machining, which consists of tool orientation planning and cutter-contact(CC) point planning. The planning strategy highly depends on the type of tool cutter...Tool path generation is a fundamental problem in 5-axis CNC machining, which consists of tool orientation planning and cutter-contact(CC) point planning. The planning strategy highly depends on the type of tool cutters. For ball-end cutters, the tool orientation and CC point location can be planned separately;while for flat end cutters, the two are highly dependent on each other. This paper generates a smooth tool path of workpiece surfaces for flat end mills from two stages: Computing smooth tool orientations on the surface without gouging and collisions and then designing the CC point path. By solving the tool posture optimization problem the authors achieve both the path smoothness and the machining efficiency. Experimental results are provided to show the effectiveness of the method.展开更多
This study determined the issues of Planning Support System(PSS)implementation in the field of urban disaster mitigation in Japan by understanding its analytical perspective through a review of Western literature,a qu...This study determined the issues of Planning Support System(PSS)implementation in the field of urban disaster mitigation in Japan by understanding its analytical perspective through a review of Western literature,a questionnaire survey of urban planning consultant companies,and PSS implementation for a practical project in a municipality.Regarding the instrum ental perspective,there was difficulty in conducting the simulationbased PSS due to the enormous simulation time required.Regarding the transfer perspective,the importance of the municipality^decision of adopting the PSS to a project,securing the budget and continuous running costs,track record of the practical project,and lack of human resource for the PSS use were clarified.Regarding the user perspective,the difficulty in data collection and update as well as im portance of the cooperative system/support from the developer in the initial period were clarified.Especially,considering the low number of implementations,a platform may be important for the promotion of PSS awareness.This may be also useful for the diffusion of PSS.It is necessary for the developers to fully comm unicate the benefits of PSS adoption.It is thought that a close cooperative system and support are required in the initial stage.For prom oting and understanding the benefits of PSS adoption,a guideline or manual seems to be useful.This is effective for ensuring the budget and providing an explanation to high-level members of the organizations about the effect of utilizing these tools.For the final implementation,the possibility of installation,maintenance,and operation of the PSS by the municipality was discussed.展开更多
For rough machining of a complex narrow cavity,e.g.,a complex blisk channel on an aero-engine,the typically used cutting tools are the slender cylindrical cutter and conical cutter.Nevertheless,as neither of the two i...For rough machining of a complex narrow cavity,e.g.,a complex blisk channel on an aero-engine,the typically used cutting tools are the slender cylindrical cutter and conical cutter.Nevertheless,as neither of the two is particularly suited for rough machining,wherein the main purpose is to remove a large volume as quickly as possible,the machining efficiency is low,especially when the part materials are of hard-to-cut types(e.g.,Titanium-alloy)for which it often takes days to rough machine a blisk.Fortunately,disc machining provides a new and efficient roughing solution,since a disc cutter with a large radius enables a much larger cutting speed and thus a larger material removal rate.However,due to the large radius of the disc cutter,its potential collision with narrow and twisted channels becomes a serious concern.In this paper,we propose a novel twophase approach for efficiently machining a complex narrow cavity workpiece using a disc-shaped cutter,i.e.,3+2-axis disc-slotting of the channel by multiple layers(rough machining)+five-axis disc-milling of the freeform channel side surfaces(semi-finish machining).Both simulation and physical cutting experiments are conducted to assess the effectiveness and advantages of the proposed method.The experimental results show that,with respect to a same cusp-height threshold on the channel side surfaces,the total machining time of the tested part by the proposed method is about only 36%of that by the conventional approach of plunging-milling(for roughing)plus milling by a slender cylindrical cutter(for semi-finishing).展开更多
In CNC machining,the tool path planning of the cutter plays an important role.In this paper,we generate a space-filling and continuous tool path for free-form surface represented by the triangular mesh with a confined...In CNC machining,the tool path planning of the cutter plays an important role.In this paper,we generate a space-filling and continuous tool path for free-form surface represented by the triangular mesh with a confined scallop height.The tool path is constructed from connected Fermat spirals(CFS)but with fewer inflection points.Comparing with the newly developed CFS method,only about half of the number of inflection points are involved.Moreover,the kinematic constraints are simultaneously taken into account to increase the feedrates in machining.Finally,we use a micro-line trajectory technique to smooth the tool path.Experimental results and physical cutting tests are provided to illustrate and clarify our method.展开更多
The computation of polyline-sourced geodesic offset holds significant importance in a variety of applications,including but not limited to solid modeling,tool path generation for computer numerical control(CNC)machini...The computation of polyline-sourced geodesic offset holds significant importance in a variety of applications,including but not limited to solid modeling,tool path generation for computer numerical control(CNC)machining,and parametrization.The traditional approaches for geodesic offsets have typically relied on the availability of an exact geodesic metric.Nevertheless,the computation of exact geodesics is characterized by its time-consuming nature and substantial memory usage.To tackle the limitation,our study puts forward a novel approach that seeks to circumvent the reliance on exact geodesic metrics.The proposed method entails a reformulated graph method that incorporates Steiner point insertion,serving as an effective solution for obtaining geodesic distances.By leveraging the aforementioned strategies,we present an efficient and robust algorithm designed for the computation of polyline-sourced geodesic offsets.The experimental evaluation,conducted on a diverse set of three-dimensional models,demonstrates significant improvements in computational speed and memory requirements compared to established state-of-the-art methods.展开更多
This paper describes the implementation and performance of the virtual assembly support sys-tem (VASS), a new system that can provide designers and assembly process engineers with a simulation and visualization enviro...This paper describes the implementation and performance of the virtual assembly support sys-tem (VASS), a new system that can provide designers and assembly process engineers with a simulation and visualization environment where they can evaluate the assemblability/disassemblability of products, and thereby use a computer to intuitively create assembly plans and interactively generate assembly process charts. Subassembly planning and assembly priority reasoning techniques were utilized to find heuristic information to improve the efficiency of assembly process planning. Tool planning was imple-mented to consider tool requirements in the product design stage. New methods were developed to reduce the computation amount involved in interference checking. As an important feature of the VASS, human interaction was integrated into the whole process of assembly process planning, extending the power of computer reasoning by including human expertise, resulting in better assembly plans and better designs.展开更多
文摘Today city planners are confronted with two global trends:on one hand,living space is getting less due to urbanization;on the other hand,demands on living space are constantly rising as for example through stricter climate and energy political objectives based on the Paris Agreement.Therefore,it will be necessary to take into account—near urban planning and social aspects—also the climate compatibility as one central aspect in the construction of buildings,settlements,districts or neighborhoods.To identify and to push successful concepts,Austria has developed a planning tool that allows planning,assessing and ensuring high quality standards of neighborhoods.As the tool has been highly successful,additional planning tools are being developed for specific topics such as“PED—Positive Energy Districts”,“NEB—New European Bauhaus”and“CND—Climate Neutral Districts”.Central quantitative and qualitative criteria—which have been elaborated in the recent years—will be presented in this paper.
文摘The historic centres revitalization addresses the challenges related to the preservation of fundamental heritage values. At a time, when everyone looks with concern to our cities＇ future, it is important to reflect on the received heritage, seeking the most appropriate answers to the planning of the historic centres. These fabrics are reference places in the urban space, due to their role of memorial testimony and of generators of cultural and economic dynamics. However, often times, inherited urban fabrics are affected by the limitations of the heritage policies which, for being too general and based on theoretical and abstract frameworks, have difficulty incorporating the characteristics of each area and neglect the formulation of specific criteria and intervention methods. The purpose of this paper is to provide a comparative reading of the levels of urban renewal allowed by the planning tools. This study chooses two historic centers in Portugal： Oporto and Guimarfies historic centres （World Heritage Sites since 1996 and 2001, respectively, and were the last to get this classification in Portugal）. This reflection is a contribution to peer trends and raise the discussion on the role that the different heritage policies have to the revitalization of the historic centres.
基金supported by the National Natural Science Foundation of China(Grant Nos.U22A20202 and 52275477).
文摘Trochoidal milling is known for its advantages in machining difficult-to-machine materials as it facilitates chip removal and tool cooling.However,the conventional trochoidal tool path presents challenges such as lower machining efficiency and longer machining time due to its time-varying cutter-workpiece engagement angle and a high percentage of non-cutting tool paths.To address these issues,this paper introduces a parameter-variant trochoidal-like(PVTR)tool path planning method for chatter-free and high-efficiency milling.This method ensures a constant engagement angle for each tool path period by adjusting the trochoidal radius and step.Initially,the nonlinear equation for the PVTR toolpath is established.Then,a segmented recurrence method is proposed to plan tool paths based on the desired engagement angle.The impact of trochoidal tool path parameters on the engagement angle is analyzed and coupled this information with the milling stability model based on spindle speed and engagement angle to determine the desired engagement angle throughout the machining process.Finally,several experimental tests are carried out using the bull-nose end mill to validate the feasibility and effectiveness of the proposed method.
基金National Natural Science Foundation of China (50875012)National High-tech Research and Development Program (2008AA04Z124)+1 种基金National Science and Technology Major Project (2009ZX04001-141)Joint Construction Project of Beijing Municipal Commission of Education
文摘The problem of finished surface being not first-order continuous commonly exists in machining sculptured surfaces with a torus cutter and some other types of cutters. To solve this problem, a dual drive curve tool path planning method is proposed in this article. First, the maximum machining strip width of a whole tool path can be obtained through optimizing each tool position with multi-point machining （MPM） method. Second, two drive curves are then determined according to the obtained maximum machining strip width. Finally, the tool is positioned once more along the dual drive curve under the condition of tool path smoothness. A computer simulation and cutting experiments are carried out to testify the performance of the new method. The machined surface is measured with a coordinate measuring machine （CMM） to examine the machining quality. The results obtained show that this method can effectively eliminate sharp scallops between adjacent tool paths, keep tool paths smooth, and improve the surface machining quality as well as machining efficiency.
文摘Based on the object oriented data structure of Voronoi diagram, the algorithm of the trimmed offset generating and the optimal too l path planning of the pocket machining for multiply connected polygonal domains are studied. The intersection state transition rule is improved in this algorithm. The intersection is between the trimmed offsets and Voronoi polygon. On this basis, the trimmed offset generating and the optimal tool path planning are mad e with three stacks(I stack, C stack and P stack)in different monotonous pouches of Voronoi diagram. At the same time, a merging method of Voronoi diagram an d offsets generating for multiply connected polygonal domains is also presented. The above algorithms have been implemented in NC machining successfully, and the efficiency is fully verified.
文摘The expression didactic innovation has recently assumed an implicit reference to Distance Learning.For scholars,however,it was above all the critical questioning on learning models.The article explores the use of the podcast as a stimulus for engineering students to achieve new soft skills:to learn multidisciplinary contents related to planning and to acquire professional competences in digital aspects and feedbacks attribution.Experience took place over two years:this gave the opportunity to compare the activity carried out totally in presence and totally remotely(through online lessons and reviews),to draw from them issues for discussion and future implementations.
基金supported by the National Key Basic Research Project of China under Grant No.2011CB302400the National Natural Science Foundation of China under Grant Nos.50975274 and 50975495
文摘For the geometry characteristics of open free-form surfaces,it is hard to consider global interference during the planning of feasible domains.Therefore,the optimal kinematic orientation of tool axis will no longer be confined to the boundary of feasible domains.In this paper,according to the principle demanding that the tool should be fitted to a surface as close as possible and relevant processing parameters,a feasible domain of tool orientation for each cutter contact is planned in the local feed coordinates system.Then,these feasible domains of the tool orientation are transformed into the same coordinates system of the machine tool by the inverse kinematics transformation.The linear equations based feasible domain method and Rosen gradient projection algorithm are used to improve the optimization process in precision and efficiency of the algorithm.It constructs the variation of tool orientation optimization model and ensures the smoothness of tool orientation globally.Simulation and analysis of examples show that the proposed method has good kinematics performance and greatly improves the efficiency.
文摘Objective:In robot-assisted minimally invasive surgery,proper port positioning ensures that surgical tools have adequate access to the surgical site and avoids mid-surgery collisions of robotic arms.To date,several guidelines have been proposed for more accurate port placement.However,challenges remain due to variations in patient morphology,anatomy,and,in particular,organ displacement due to insuf-flation in certain laparoscopic procedures.The objective of this study was to design and develop a de-cision aid for optimal port placement in robot-assisted hysterectomy that accounts for patient variability and organ displacement due to insufflation.Methods:Three components were constructed:a robot model,a patient-specific model,and an opti-mization algorithm.The three components were integrated,and the system was verified using four different patients who underwent robotic hysterectomy.Once verified,two expert surgeons were asked to evaluate the decision aid for face and construct validity.A usability test was conducted using a torso phantom with target organs located in three different locations.Two expert surgeons performed a simulated hysterectomy task with and without the decision aid to evaluate performance and satisfaction.Results:The optimization algorithm was sensitive to individual differences in anatomy in the four pa-tients.Expert surgeons successfully established face and construct validity.Usability test results showed a 28%-40% reduction in time to task completion with the optimized ports compared to expert-determined port locations without using the decision aid.Conclusions:The decision aid,based on an individualized patient-specific model,robot model,and optimization algorithm,was shown to be effective at addressing the challenges of displaced organs due to insufflation in robot-assisted hysterectomy.The face and construct validity of the decision aid was established by expert surgeons,while efficiency gains in task performance were demonstrated experimentally.
基金supported by the National Natural Science Foundation of China (51175065)
文摘Motivated by the definition of the machining errors induced by tool path planning methods, a mapping curve of the tool axis of a cylindrical cutter is constructed on the tool surface. The mapping curve is a typical one that can be used to express the closeness between the tool surface and the surface to be machined. A novel tool path planning method is proposed for flank or plunge milling ruled surfaces based on the minimization of the one-sided Hausdorff distance （HD） from the mapping curve to the surface to be machined. It is a nonlinear optimization problem in best uniform approximation （BUA） or Chebyshev sense. A mathematical programming model for computing the minimum one-sided HD is proposed. The linearization method of the programming model is provided and the final optimal solutions are obtained by simplex method. The effectiveness of the proposed BUA method is verified by two numerical examples and compared with the least squares （LS） and double point offset （DPO） methods. The variation in tool orientation induced by the optimization of the tool positions is also evaluated.
基金supported by the National Natural Science Foundation of China under Grant No.11688101,61872332Beijing National Natural Science Foundation under Grant No.Z190004+1 种基金National Center for Mathematics and Interdisciplinary SciencesYouth Innovation Promotion Association of the Chinese Academy of Sciences。
文摘Tool path generation is a fundamental problem in 5-axis CNC machining, which consists of tool orientation planning and cutter-contact(CC) point planning. The planning strategy highly depends on the type of tool cutters. For ball-end cutters, the tool orientation and CC point location can be planned separately;while for flat end cutters, the two are highly dependent on each other. This paper generates a smooth tool path of workpiece surfaces for flat end mills from two stages: Computing smooth tool orientations on the surface without gouging and collisions and then designing the CC point path. By solving the tool posture optimization problem the authors achieve both the path smoothness and the machining efficiency. Experimental results are provided to show the effectiveness of the method.
文摘This study determined the issues of Planning Support System(PSS)implementation in the field of urban disaster mitigation in Japan by understanding its analytical perspective through a review of Western literature,a questionnaire survey of urban planning consultant companies,and PSS implementation for a practical project in a municipality.Regarding the instrum ental perspective,there was difficulty in conducting the simulationbased PSS due to the enormous simulation time required.Regarding the transfer perspective,the importance of the municipality^decision of adopting the PSS to a project,securing the budget and continuous running costs,track record of the practical project,and lack of human resource for the PSS use were clarified.Regarding the user perspective,the difficulty in data collection and update as well as im portance of the cooperative system/support from the developer in the initial period were clarified.Especially,considering the low number of implementations,a platform may be important for the promotion of PSS awareness.This may be also useful for the diffusion of PSS.It is necessary for the developers to fully comm unicate the benefits of PSS adoption.It is thought that a close cooperative system and support are required in the initial stage.For prom oting and understanding the benefits of PSS adoption,a guideline or manual seems to be useful.This is effective for ensuring the budget and providing an explanation to high-level members of the organizations about the effect of utilizing these tools.For the final implementation,the possibility of installation,maintenance,and operation of the PSS by the municipality was discussed.
基金supported in part by Foshan HKUST Projects(Project ID:FSUST20-SRI09E–FSPM02202007-1)the Project of Hetao Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone(Project ID:HZQB-KCZYB-2020083)the National Science and Technology Major Project(Grant No.J2019-VII-0001-0141)。
文摘For rough machining of a complex narrow cavity,e.g.,a complex blisk channel on an aero-engine,the typically used cutting tools are the slender cylindrical cutter and conical cutter.Nevertheless,as neither of the two is particularly suited for rough machining,wherein the main purpose is to remove a large volume as quickly as possible,the machining efficiency is low,especially when the part materials are of hard-to-cut types(e.g.,Titanium-alloy)for which it often takes days to rough machine a blisk.Fortunately,disc machining provides a new and efficient roughing solution,since a disc cutter with a large radius enables a much larger cutting speed and thus a larger material removal rate.However,due to the large radius of the disc cutter,its potential collision with narrow and twisted channels becomes a serious concern.In this paper,we propose a novel twophase approach for efficiently machining a complex narrow cavity workpiece using a disc-shaped cutter,i.e.,3+2-axis disc-slotting of the channel by multiple layers(rough machining)+five-axis disc-milling of the freeform channel side surfaces(semi-finish machining).Both simulation and physical cutting experiments are conducted to assess the effectiveness and advantages of the proposed method.The experimental results show that,with respect to a same cusp-height threshold on the channel side surfaces,the total machining time of the tested part by the proposed method is about only 36%of that by the conventional approach of plunging-milling(for roughing)plus milling by a slender cylindrical cutter(for semi-finishing).
基金supported by Beijing Natural Science Foundation under Grant Z190004National Key Research and Development Program of China under Grant 2020YFA0713703,NSFC(Nos.11688101,61872332)and Fundamental Research Funds for the Central Universities.
文摘In CNC machining,the tool path planning of the cutter plays an important role.In this paper,we generate a space-filling and continuous tool path for free-form surface represented by the triangular mesh with a confined scallop height.The tool path is constructed from connected Fermat spirals(CFS)but with fewer inflection points.Comparing with the newly developed CFS method,only about half of the number of inflection points are involved.Moreover,the kinematic constraints are simultaneously taken into account to increase the feedrates in machining.Finally,we use a micro-line trajectory technique to smooth the tool path.Experimental results and physical cutting tests are provided to illustrate and clarify our method.
基金supported in part by the National Natural Science Foundation of China(No.62302124)the Natural Science Foundation of Shandong Province(No.ZR2023QF122)in part by the Youth Teacher Development Foundation of Harbin Institute of Technology(No.IDGA10002143).
文摘The computation of polyline-sourced geodesic offset holds significant importance in a variety of applications,including but not limited to solid modeling,tool path generation for computer numerical control(CNC)machining,and parametrization.The traditional approaches for geodesic offsets have typically relied on the availability of an exact geodesic metric.Nevertheless,the computation of exact geodesics is characterized by its time-consuming nature and substantial memory usage.To tackle the limitation,our study puts forward a novel approach that seeks to circumvent the reliance on exact geodesic metrics.The proposed method entails a reformulated graph method that incorporates Steiner point insertion,serving as an effective solution for obtaining geodesic distances.By leveraging the aforementioned strategies,we present an efficient and robust algorithm designed for the computation of polyline-sourced geodesic offsets.The experimental evaluation,conducted on a diverse set of three-dimensional models,demonstrates significant improvements in computational speed and memory requirements compared to established state-of-the-art methods.
基金Supported by the National High-Tech Research and Development (863) Program of China (Nos. 863-511-910-405 and 863-511-030-003)
文摘This paper describes the implementation and performance of the virtual assembly support sys-tem (VASS), a new system that can provide designers and assembly process engineers with a simulation and visualization environment where they can evaluate the assemblability/disassemblability of products, and thereby use a computer to intuitively create assembly plans and interactively generate assembly process charts. Subassembly planning and assembly priority reasoning techniques were utilized to find heuristic information to improve the efficiency of assembly process planning. Tool planning was imple-mented to consider tool requirements in the product design stage. New methods were developed to reduce the computation amount involved in interference checking. As an important feature of the VASS, human interaction was integrated into the whole process of assembly process planning, extending the power of computer reasoning by including human expertise, resulting in better assembly plans and better designs.
