The configuration space is a fundamental concept that is widely used in algorithmic robotics. Many applications in robotics, computer-aided design, and related areas can be reduced to computational problems in terms o...The configuration space is a fundamental concept that is widely used in algorithmic robotics. Many applications in robotics, computer-aided design, and related areas can be reduced to computational problems in terms of configuration spaces. In this paper, we survey some of our recent work on solving two important challenges related to configuration spaces： ~ how to efficiently compute an approximate representation of high-dimensional configuration spaces; and how to efficiently perform geometric proximity and motion planning queries （n high-dimensional configuration spaces. We present new configuration space construction algorithms based on machine learning and geometric approximation techniques. These algorithms perform collision queries on many configuration samples. The collision query results are used to compute an approximate representation for the configuration space, which quickly converges to the exact configuration space. We also present parallel GPU-based algorithms to accelerate the performance of optimization and search computations in configuration spaces. In particular, we design efficient GPU-based parallel k-nearest neighbor and parallel collision detection algorithms and use these algorithms to accelerate motion planning.展开更多
Let X be a topological space.In this survey the authors consider several types of configuration spaces,namely,the classical(usual)configuration spaces F_n(X)and D_n(X),the orbit configuration spaces F_n^G(X)and F_n^G(...Let X be a topological space.In this survey the authors consider several types of configuration spaces,namely,the classical(usual)configuration spaces F_n(X)and D_n(X),the orbit configuration spaces F_n^G(X)and F_n^G(X)/S_nwith respect to a free action of a group G on X,and the graph configuration spaces F_n~Γ(X)and F_n~Γ(X)/H,whereΓis a graph and H is a suitable subgroup of the symmetric group S_n.The ordered configuration spaces F_n(X),F_n^G(X),F_n~Γ(X)are all subsets of the n-fold Cartesian product ∏_1~nX of X with itself,and satisfy F_n^G(X)?F_n(X)?F_n~Γ(X)?∏_1~nX.If A denotes one of these configuration spaces,the authors analyse the difference between A and ∏_1~nXfrom a topological and homotopical point of view.The principal results known in the literature concern the usual configuration spaces.The authors are particularly interested in the homomorphism on the level of the homotopy groups of the spaces induced by the inclusionι:A-→∏_1~nX,the homotopy type of the homotopy fibre I_ιof the mapιvia certain constructions on various spaces that depend on X,and the long exact sequence in homotopy of the fibration involving I_ιand arising from the inclusionι.In this respect,if X is either a surface without boundary,in particular if X is the 2-sphere or the real projective plane,or a space whose universal covering is contractible,or an orbit space S^k/Gof the k-dimensional sphere by a free action of a Lie group G,the authors present recent results obtained by themselves for the first case,and in collaboration with Golasi′nski for the second and third cases.The authors also briefly indicate some older results relative to the homotopy of these spaces that are related to the problems of interest.In order to motivate various questions,for the remaining types of configuration spaces,a few of their basic properties are described and proved.A list of open questions and problems is given at the end of the paper.展开更多
Abstract In this paper, we explore the fixed point theory of n-vaiued maps using configuration spaces and braid groups, focusing on two fundamental problems, the Wecken property, and the computation of the Nielsen num...Abstract In this paper, we explore the fixed point theory of n-vaiued maps using configuration spaces and braid groups, focusing on two fundamental problems, the Wecken property, and the computation of the Nielsen number. We show that the projective plane （resp. the 2-sphere S2） has the Wecken property for n-valued maps for all n ∈N （resp. all n ≥ 3）. In the case n = 2 and S2, we prove a partial result about the Wecken property. We then describe the Nielsen number of a non-split n-valued map φ ： X → X of an orientable, compact manifold without boundary in terms of the Nielsen coincidence numbers of a certain finite covering q： ）→ X with a subset of the coordinate maps of a lift of the n-valued split map → q ： →X.展开更多
In this article,we investigate the orbit configuration spaces of some equivariant closed manifolds over simple convex polytopes in toric topology,such as small covers,quasi-toric manifolds and(real)moment-angle manifo...In this article,we investigate the orbit configuration spaces of some equivariant closed manifolds over simple convex polytopes in toric topology,such as small covers,quasi-toric manifolds and(real)moment-angle manifolds;especially for the cases of small covers and quasi-toric manifolds.These kinds of orbit configuration spaces have non-free group actions,and they are all noncompact,but still built via simple convex polytopes.We obtain an explicit formula of the Euler characteristic for orbit configuration spaces of small covers and quasi-toric manifolds in terms of the h-vector of a simple convex polytope.As a by-product of our method,we also obtain a formula of the Euler characteristic for the classical configuration space,which generalizes the Félix-Thomas formula.In addition,we also study the homotopy type of such orbit configuration spaces.In particular,we determine an equivariant strong deformation retraction of the orbit configuration space of 2 distinct orbit-points in a small cover or a quasi-toric manifold,which allows to further study the algebraic topology of such an orbit configuration space by using the Mayer-Vietoris spectral sequence.展开更多
A natural compactification of the virtual configuration space of N points on the Riemann sphere C is constructed by using cross-ratios. We show that this compactification is homeomorphic to the Bers＇ compactification...A natural compactification of the virtual configuration space of N points on the Riemann sphere C is constructed by using cross-ratios. We show that this compactification is homeomorphic to the Bers＇ compactification of the virtual moduli space of a punctured Riemann sphere of type N. In particular, the system of global and explicit coordinates of this standard compactification is given by cross-ratios.展开更多
Motivated by the work in Li et al.(2019),this paper deals with the theory of the braids from chromatic configuration spaces.These kinds of braids possess the property that some strings of each braid may intersect toge...Motivated by the work in Li et al.(2019),this paper deals with the theory of the braids from chromatic configuration spaces.These kinds of braids possess the property that some strings of each braid may intersect together and can also be untangled,so they are quite different from the ordinary braids in the sense of Artin(1925).This enriches and extends the theory of ordinary braids.展开更多
[Objectives]To provide a reference for the promotion of appropriate row spacing configuration modes for cotton planting in the Bortala Mongol Autonomous Prefecture of Xinjiang.[Methods]Xinluzao 63 was employed as the ...[Objectives]To provide a reference for the promotion of appropriate row spacing configuration modes for cotton planting in the Bortala Mongol Autonomous Prefecture of Xinjiang.[Methods]Xinluzao 63 was employed as the research subject to examine the effects of three different configuration modes:three rows with one film,four rows with one film,and six rows with one film,on the growth and development of cotton,as well as on yield and the amount of residual film in the field.[Results]In comparison to the configuration modes of four rows with one film and six rows with one film,the development process in the row spacing configuration mode of three rows with one film was accelerated by 1-4 d.This configuration mode exhibited variability in several agronomic traits,particularly in plant height,the number of fruiting branches per plant,and the number of leaves per plant,with the observed trend indicating T3>T2>T1.Conversely,the height of the first fruiting branch node displayed an inverse trend.In terms of yield composition,no significant differences were observed in boll weight and yield among various configuration modes.However,T3 exhibited the highest boll weight at 5.68 g and a yield of 462.67 kg/667 m 2.Additionally,significant differences were noted in harvesting density and the number of bolls per plant.T3 demonstrated the lowest harvesting density at 1.11×104 plants/666.7 m 2,the highest number of bolls per plant at 8.63,and the highest boll opening rate at 97.48%.Furthermore,T3 also resulted in the least amount of agricultural film residue during the current season.[Conclusions]Among the three planting configuration modes examined,the low-density planting configuration mode consisting of three rows and one film demonstrated a significant advantage at the individual plant level.This approach yielded results comparable to those of the high density planting configuration mode while also reducing costs.Furthermore,low density planting positively influenced the cotton boll opening rate,leading to a decreased amount of residual film and promoting ecological health within the agricultural land.展开更多
A discharge plasma reactor with a point-to-plane structure was widely studied experimentally in wastewater treatment.In order to improve the utilization efficiency of active species and the energy efficiency of this k...A discharge plasma reactor with a point-to-plane structure was widely studied experimentally in wastewater treatment.In order to improve the utilization efficiency of active species and the energy efficiency of this kind of discharge plasma reactor during wastewater treatment,the electrode configuration of the point-to-plane corona discharge reactor was studied by evaluating the effects of discharge spacing and adjacent point distance on discharge power and discharge energy density,and then dye-containing wastewater decoloration experiments were conducted on the basis of the optimum electrode configuration.The experimental results of the discharge characteristics showed that high discharge power and discharge energy density were achieved when the ratio of discharge spacing to adjacent point distance（d/s） was 0.5.Reactive Brilliant Blue（RBB） wastewater treatment experiments presented that the highest RBB decoloration efficiency was observed at d/s of 0.5,which was consistent with the result obtained in the discharge characteristics experiments.In addition,the biodegradability of RBB wastewater was enhanced greatly after discharge plasma treatment under the optimum electrode configuration.RBB degradation processes were analyzed by GC-MS and IC,and the possible mechanism for RBB decoloration was also discussed.展开更多
A robot intelligent path planning system RIPPS is developed, which can be utilized for a robot off line programming tool. The system consists of three parts: geometric modeler, kinematic modeler and path planer. The...A robot intelligent path planning system RIPPS is developed, which can be utilized for a robot off line programming tool. The system consists of three parts: geometric modeler, kinematic modeler and path planer. The geometric modeler is used to construct the robot working environment cluttered with obstacles and the robot kinematic modeler to define robot manipulators by the input parameters. Giving robot start and the goal configurations, the path planer can produce a quasi optimal path. By transforming obstacles into the C space to form C obstacles, the path searching is performed in C space. The planning simulations are performed on a SGI workstation, the future research is to implement the planer on a commercial robot manipulators.展开更多
In this paper the geometric meaning of robot systems is expounded based on the theory of multibody system. The error accumulation for the known algorithm is analyzed and the cause of ‘Energy consumption’ is revealed...In this paper the geometric meaning of robot systems is expounded based on the theory of multibody system. The error accumulation for the known algorithm is analyzed and the cause of ‘Energy consumption’ is revealed, the relationship between the coefficients of dynamic equation is derived so as to establish the canonical equations. The error accumulation of dynamics can be eliminated by using canonical equations and the symplectic integral method so that the computational accuracy can be ensured effectively. As an example, a planar robotics system is considered.展开更多
To obtain the near optimal path for the mobile robots in the present of the obstacles, where the robots are subject to both the nonholonomic constraints and the bound to the curvature of the path, a simple planning i...To obtain the near optimal path for the mobile robots in the present of the obstacles, where the robots are subject to both the nonholonomic constraints and the bound to the curvature of the path, a simple planning is applied by the heuristic searching method in which Reeds and Shepp’s shortest paths are chosen as heuristic functions. It has performed well in simulation of mobile robots moving in a cluttered environment.展开更多
This paper proposes an accurate valuable interpretation scheme to study the evolvement of the photoionization processes from the isolated to the condensed atoms by a unique ab initio method. The variations of the phot...This paper proposes an accurate valuable interpretation scheme to study the evolvement of the photoionization processes from the isolated to the condensed atoms by a unique ab initio method. The variations of the photoionization cross sections of the atomic sodium with the photoelectron energy and the boundary radius of the atomic configuration space are studied in this new scheme by the R-matrix method. The discrepancy in the photoionization spectra of the isolated and the condensed sodium has been explained quantitatively and understood successfully by this alternative view in detail for the first time.展开更多
In this paper, a new concept, i.e. Generalized Jacobian Matrix of MBS (abbreviation for multibody system) is presented which unifies three concepts of different realms, Partial (angular) velocity in MBS, first order e...In this paper, a new concept, i.e. Generalized Jacobian Matrix of MBS (abbreviation for multibody system) is presented which unifies three concepts of different realms, Partial (angular) velocity in MBS, first order effect coefficient in mechanism, Jacobian Matrix in robotics. This new concept not only enriches and developes kinematics of MBS and makes kinematics theory of MBS concise and being a formal way. but also becomes a new way to kinematic analysis of spatial mechanisms. It is also enlarged the paper that the usage of kinematics of MBS, the identical relationship between kinematics of MBS and error analysis of MBS is revealed.展开更多
This paper proposes a trajectory planning approach based on the configuration space(C-space)generated from large-scale digital twinning.Leveraging GPU-based parallelism,the C-space of a multi-degree-of-freedom(multi-D...This paper proposes a trajectory planning approach based on the configuration space(C-space)generated from large-scale digital twinning.Leveraging GPU-based parallelism,the C-space of a multi-degree-of-freedom(multi-DoF)manipulator in a complex task space with obstacles can be mapped out through extensive simulation of motion and collision of multiple virtual robot arms known as digital twins.An optimal search algorithm is incorporated with artificial potential field generated in the C-space to allow the prioritising of safety in accordance with the varying risks associated with the obstacles by means of variable repulsive potential.To extend the high-degree path to smooth and continuous joint trajectories,a spline operation is applied.Finally,a 7-DOF physical manipulator is deployed for the execution of the planned trajectory in a task space flled with ob-stacles.Results demonstrated a 16.3%improvement in success rate achieved by utilising the safety-prioritisable search algo-rithm.With this unifed formulation of the control and planning problem in the C-space,the kinematics complexity of a large DOF manipulator in obstacle-present task space could be truly relieved from the joint control loop.This simplification,in turn,opens up prospective work in dynamic reconstruction of the C-space.展开更多
This article addresses the issue of computing the constant required to implement a specific nonparametric subset selection procedure based on ranks of data arising in a statistical randomized block experimental design...This article addresses the issue of computing the constant required to implement a specific nonparametric subset selection procedure based on ranks of data arising in a statistical randomized block experimental design. A model of three populations and two blocks is used to compute the probability distribution of the relevant statistic, the maximum of the population rank sums minus the rank sum of the “best” population. Calculations are done for populations following a normal distribution, and for populations following a bi-uniform distribution. The least favorable configuration in these cases is shown to arise when all three populations follow identical distributions. The bi-uniform distribution leads to an asymptotic counterexample to the conjecture that the least favorable configuration, i.e., that configuration minimizing the probability of a correct selection, occurs when all populations are identically distributed. These results are consistent with other large-scale simulation studies. All relevant computational R-codes are provided in appendices.展开更多
Autonomous aerial refueling technology is gaining increasing attention to enhance aircraft combat capabilities.Current research on autonomous refueling focuses mainly on flight control laws,with little attention to th...Autonomous aerial refueling technology is gaining increasing attention to enhance aircraft combat capabilities.Current research on autonomous refueling focuses mainly on flight control laws,with little attention to the automation of refueling pipes.This leads to high demands on control law performance and navigation accuracy,making it difficult to ensure reliability.To address this,we propose a robotic arm system capable of automatic docking during the flexible aerial refueling process.The system uses a conical kinematic space configuration,offering enhanced stability and impact resistance.The frame-type structure achieves a lightweight design.Additionally,we establish a single-objective optimization model for the connecting rod dimensions and apply a genetic algorithm(GA)for their optimization.We also propose a trajectory-fitting calibration theory based on the robotic arm's special configuration and complete its movement accuracy calibration using a laser tracker.This calibration method reduces the robotic arm's motion error by 71%,achieving an absolute positioning accuracy better than 3.5 mm,which meets the requirements for autonomous aerial refueling.In summary,this research presents a hybrid robotic arm that meets automatic docking requirements,offering a new approach to autonomous aerial refueling.展开更多
In the context of robotics, configuration space （c- space） is widely used for non-circular robots to engage tasks such as path planning, collision check, and motion planning. In many real-time applications, it is im...In the context of robotics, configuration space （c- space） is widely used for non-circular robots to engage tasks such as path planning, collision check, and motion planning. In many real-time applications, it is important for a robot to give a quick response to the user＇s command. Therefore, a constant bound on planning time per action is severely im- posed. However, existing search algorithms used in c-space gain first move lags which vary with the size of the under- lying problem. Furthermore, applying real-time search algo- rithms on c-space maps often causes the robots being trapped within local minima. In order to solve the above mentioned problems, we extend the learning real-time search （LRTS） algorithm to search on a set of c-space generalized Voronoi diagrams （c-space GVDs）, helping the robots to incremen- tally plan a path, to efficiently avoid local minima, and to ex- ecute fast movement. In our work, an incremental algorithm is firstly proposed to build and represent the c-space maps in Boolean vectors. Then, the method of detecting grid-based GVDs from the c-space maps is further discussed. Based on the c-space GVDs, details of the LRTS and its implemen- tation considerations are studied. The resulting experiments and analysis show that, using LRTS to search on the c-space GVDs can 1） gain smaller and constant first move lags which is independent of the problem size; 2） gain maximal clear- ance from obstacles so that collision checks are much re- duced; 3） avoid local minima and thus prevent the robot from visually unrealistic scratching.展开更多
An efficient path planning algorithm based on topologic method is presented in this paper.The colli- sion free path planning for three-joint robotic arm consists of three parts:partition of C-space,construc- tion of C...An efficient path planning algorithm based on topologic method is presented in this paper.The colli- sion free path planning for three-joint robotic arm consists of three parts:partition of C-space,construc- tion of CN and search for a path in CN.We mainly solved the problems of partitioning the C-space and judging the connectivity between connected blocks,etc.For the motion planning of a robotic arm with a gripper,we developed the concepts of global planning and local planning,and discussed the basic fac- tors for constructing the planning system.In the paper,some evaluation and analysis of the complexity and reliability of the algorithm are given,together with some ideas to improve the efficiency and increase the reliability.At last,some experimental results are presented to show the efficiency and accuracy of the nigorithm.展开更多
This paper presents a direct 3D painting algorithm for polygonalmodels in 3D object-space with a metaball-based paintbrush in virtual environment.The user is allowed to directly manipulate the parameters used to shade...This paper presents a direct 3D painting algorithm for polygonalmodels in 3D object-space with a metaball-based paintbrush in virtual environment.The user is allowed to directly manipulate the parameters used to shade the surfaceof the 3D shape by applying the pigment to its surface with direct 3D manipulationthrough a 3D flying mouse.展开更多
By using the Mecke identity, we study a class of birth-death type Dirichlet forms associated with the mixed Poisson measure. Both Poincare and weak Poincare inequalities are established, while another Poincare type in...By using the Mecke identity, we study a class of birth-death type Dirichlet forms associated with the mixed Poisson measure. Both Poincare and weak Poincare inequalities are established, while another Poincare type inequality is disproved under some reasonable assumptions.展开更多
基金partially supported by the Army Research Office,the National Science Foundation,Willow Garagethe Seed Funding Programme for Basic Research at the University of Hong Kong
文摘The configuration space is a fundamental concept that is widely used in algorithmic robotics. Many applications in robotics, computer-aided design, and related areas can be reduced to computational problems in terms of configuration spaces. In this paper, we survey some of our recent work on solving two important challenges related to configuration spaces： ~ how to efficiently compute an approximate representation of high-dimensional configuration spaces; and how to efficiently perform geometric proximity and motion planning queries （n high-dimensional configuration spaces. We present new configuration space construction algorithms based on machine learning and geometric approximation techniques. These algorithms perform collision queries on many configuration samples. The collision query results are used to compute an approximate representation for the configuration space, which quickly converges to the exact configuration space. We also present parallel GPU-based algorithms to accelerate the performance of optimization and search computations in configuration spaces. In particular, we design efficient GPU-based parallel k-nearest neighbor and parallel collision detection algorithms and use these algorithms to accelerate motion planning.
基金supported by the CNRS/FAPESP programme no226555(France)and n^(o) 2014/50131-7(Brazil)FAPESP–Fundacao de Amparo a Pesquisa do Estado de Sao Paulo,Projeto Tematico Topologia Algebrica,Geometrica 2012/24454-8(Brazil)for partial supportthe Institute for Mathematical Sciences,National University of Singapore
文摘Let X be a topological space.In this survey the authors consider several types of configuration spaces,namely,the classical(usual)configuration spaces F_n(X)and D_n(X),the orbit configuration spaces F_n^G(X)and F_n^G(X)/S_nwith respect to a free action of a group G on X,and the graph configuration spaces F_n~Γ(X)and F_n~Γ(X)/H,whereΓis a graph and H is a suitable subgroup of the symmetric group S_n.The ordered configuration spaces F_n(X),F_n^G(X),F_n~Γ(X)are all subsets of the n-fold Cartesian product ∏_1~nX of X with itself,and satisfy F_n^G(X)?F_n(X)?F_n~Γ(X)?∏_1~nX.If A denotes one of these configuration spaces,the authors analyse the difference between A and ∏_1~nXfrom a topological and homotopical point of view.The principal results known in the literature concern the usual configuration spaces.The authors are particularly interested in the homomorphism on the level of the homotopy groups of the spaces induced by the inclusionι:A-→∏_1~nX,the homotopy type of the homotopy fibre I_ιof the mapιvia certain constructions on various spaces that depend on X,and the long exact sequence in homotopy of the fibration involving I_ιand arising from the inclusionι.In this respect,if X is either a surface without boundary,in particular if X is the 2-sphere or the real projective plane,or a space whose universal covering is contractible,or an orbit space S^k/Gof the k-dimensional sphere by a free action of a Lie group G,the authors present recent results obtained by themselves for the first case,and in collaboration with Golasi′nski for the second and third cases.The authors also briefly indicate some older results relative to the homotopy of these spaces that are related to the problems of interest.In order to motivate various questions,for the remaining types of configuration spaces,a few of their basic properties are described and proved.A list of open questions and problems is given at the end of the paper.
基金supported by Fundao de Amparo a Pesquisa do Estado de So Paulo(FAPESP)Projeto Temtico Topologia Algébrica,Geométrica e Diferencial(Grant No.2012/24454-8)supported by the same project as well as the Centre National de la Recherche Scientifique(CNRS)/Fundao de Amparo a Pesquisa do Estado de So Paulo(FAPESP)Projet de Recherche Conjoint(PRC)project(Grant No.275209)
文摘Abstract In this paper, we explore the fixed point theory of n-vaiued maps using configuration spaces and braid groups, focusing on two fundamental problems, the Wecken property, and the computation of the Nielsen number. We show that the projective plane （resp. the 2-sphere S2） has the Wecken property for n-valued maps for all n ∈N （resp. all n ≥ 3）. In the case n = 2 and S2, we prove a partial result about the Wecken property. We then describe the Nielsen number of a non-split n-valued map φ ： X → X of an orientable, compact manifold without boundary in terms of the Nielsen coincidence numbers of a certain finite covering q： ）→ X with a subset of the coordinate maps of a lift of the n-valued split map → q ： →X.
基金supported by National Natural Science Foundation of China(Grant Nos.11371093,11431009 and 11661131004)supported by National Natural Science Foundation of China(Grant No.11028104)。
文摘In this article,we investigate the orbit configuration spaces of some equivariant closed manifolds over simple convex polytopes in toric topology,such as small covers,quasi-toric manifolds and(real)moment-angle manifolds;especially for the cases of small covers and quasi-toric manifolds.These kinds of orbit configuration spaces have non-free group actions,and they are all noncompact,but still built via simple convex polytopes.We obtain an explicit formula of the Euler characteristic for orbit configuration spaces of small covers and quasi-toric manifolds in terms of the h-vector of a simple convex polytope.As a by-product of our method,we also obtain a formula of the Euler characteristic for the classical configuration space,which generalizes the Félix-Thomas formula.In addition,we also study the homotopy type of such orbit configuration spaces.In particular,we determine an equivariant strong deformation retraction of the orbit configuration space of 2 distinct orbit-points in a small cover or a quasi-toric manifold,which allows to further study the algebraic topology of such an orbit configuration space by using the Mayer-Vietoris spectral sequence.
基金supported by Grants-in-Aid for Scientific Research (C) (Grant No. 23540202)Grant-in-Aids for Scientific Research (B) (Grant No. 20340030)
文摘A natural compactification of the virtual configuration space of N points on the Riemann sphere C is constructed by using cross-ratios. We show that this compactification is homeomorphic to the Bers＇ compactification of the virtual moduli space of a punctured Riemann sphere of type N. In particular, the system of global and explicit coordinates of this standard compactification is given by cross-ratios.
基金supported by National Natural Science Foundation of China(Grant No.11971112)。
文摘Motivated by the work in Li et al.(2019),this paper deals with the theory of the braids from chromatic configuration spaces.These kinds of braids possess the property that some strings of each braid may intersect together and can also be untangled,so they are quite different from the ordinary braids in the sense of Artin(1925).This enriches and extends the theory of ordinary braids.
基金Supported by China Agriculture(Cotton)Research System(CARS-15-46)Intellectual Aid Xinjiang Innovation and Expansion Talent Program of Xinjiang Uygur Autonomous Region(2024500207).
文摘[Objectives]To provide a reference for the promotion of appropriate row spacing configuration modes for cotton planting in the Bortala Mongol Autonomous Prefecture of Xinjiang.[Methods]Xinluzao 63 was employed as the research subject to examine the effects of three different configuration modes:three rows with one film,four rows with one film,and six rows with one film,on the growth and development of cotton,as well as on yield and the amount of residual film in the field.[Results]In comparison to the configuration modes of four rows with one film and six rows with one film,the development process in the row spacing configuration mode of three rows with one film was accelerated by 1-4 d.This configuration mode exhibited variability in several agronomic traits,particularly in plant height,the number of fruiting branches per plant,and the number of leaves per plant,with the observed trend indicating T3>T2>T1.Conversely,the height of the first fruiting branch node displayed an inverse trend.In terms of yield composition,no significant differences were observed in boll weight and yield among various configuration modes.However,T3 exhibited the highest boll weight at 5.68 g and a yield of 462.67 kg/667 m 2.Additionally,significant differences were noted in harvesting density and the number of bolls per plant.T3 demonstrated the lowest harvesting density at 1.11×104 plants/666.7 m 2,the highest number of bolls per plant at 8.63,and the highest boll opening rate at 97.48%.Furthermore,T3 also resulted in the least amount of agricultural film residue during the current season.[Conclusions]Among the three planting configuration modes examined,the low-density planting configuration mode consisting of three rows and one film demonstrated a significant advantage at the individual plant level.This approach yielded results comparable to those of the high density planting configuration mode while also reducing costs.Furthermore,low density planting positively influenced the cotton boll opening rate,leading to a decreased amount of residual film and promoting ecological health within the agricultural land.
基金supported by China's Postdoctoral Science Foundation(No.2014M562460)the Initiative Funding Programs for Doctoral Research of Northwest A&F University(No.2013BSJJ121)National Natural Science Foundation of China(No.21107085)
文摘A discharge plasma reactor with a point-to-plane structure was widely studied experimentally in wastewater treatment.In order to improve the utilization efficiency of active species and the energy efficiency of this kind of discharge plasma reactor during wastewater treatment,the electrode configuration of the point-to-plane corona discharge reactor was studied by evaluating the effects of discharge spacing and adjacent point distance on discharge power and discharge energy density,and then dye-containing wastewater decoloration experiments were conducted on the basis of the optimum electrode configuration.The experimental results of the discharge characteristics showed that high discharge power and discharge energy density were achieved when the ratio of discharge spacing to adjacent point distance（d/s） was 0.5.Reactive Brilliant Blue（RBB） wastewater treatment experiments presented that the highest RBB decoloration efficiency was observed at d/s of 0.5,which was consistent with the result obtained in the discharge characteristics experiments.In addition,the biodegradability of RBB wastewater was enhanced greatly after discharge plasma treatment under the optimum electrode configuration.RBB degradation processes were analyzed by GC-MS and IC,and the possible mechanism for RBB decoloration was also discussed.
文摘A robot intelligent path planning system RIPPS is developed, which can be utilized for a robot off line programming tool. The system consists of three parts: geometric modeler, kinematic modeler and path planer. The geometric modeler is used to construct the robot working environment cluttered with obstacles and the robot kinematic modeler to define robot manipulators by the input parameters. Giving robot start and the goal configurations, the path planer can produce a quasi optimal path. By transforming obstacles into the C space to form C obstacles, the path searching is performed in C space. The planning simulations are performed on a SGI workstation, the future research is to implement the planer on a commercial robot manipulators.
文摘In this paper the geometric meaning of robot systems is expounded based on the theory of multibody system. The error accumulation for the known algorithm is analyzed and the cause of ‘Energy consumption’ is revealed, the relationship between the coefficients of dynamic equation is derived so as to establish the canonical equations. The error accumulation of dynamics can be eliminated by using canonical equations and the symplectic integral method so that the computational accuracy can be ensured effectively. As an example, a planar robotics system is considered.
文摘To obtain the near optimal path for the mobile robots in the present of the obstacles, where the robots are subject to both the nonholonomic constraints and the bound to the curvature of the path, a simple planning is applied by the heuristic searching method in which Reeds and Shepp’s shortest paths are chosen as heuristic functions. It has performed well in simulation of mobile robots moving in a cluttered environment.
基金Project supported by the Natural Science Foundations of Ludong University (Grant Nos 22270301 and L20072804)
文摘This paper proposes an accurate valuable interpretation scheme to study the evolvement of the photoionization processes from the isolated to the condensed atoms by a unique ab initio method. The variations of the photoionization cross sections of the atomic sodium with the photoelectron energy and the boundary radius of the atomic configuration space are studied in this new scheme by the R-matrix method. The discrepancy in the photoionization spectra of the isolated and the condensed sodium has been explained quantitatively and understood successfully by this alternative view in detail for the first time.
文摘In this paper, a new concept, i.e. Generalized Jacobian Matrix of MBS (abbreviation for multibody system) is presented which unifies three concepts of different realms, Partial (angular) velocity in MBS, first order effect coefficient in mechanism, Jacobian Matrix in robotics. This new concept not only enriches and developes kinematics of MBS and makes kinematics theory of MBS concise and being a formal way. but also becomes a new way to kinematic analysis of spatial mechanisms. It is also enlarged the paper that the usage of kinematics of MBS, the identical relationship between kinematics of MBS and error analysis of MBS is revealed.
基金State Key Laboratory(SKL)of Biobased Transportation Fuel Technology and ZJU-YST Joint Research Centre for Fundamental Science.
文摘This paper proposes a trajectory planning approach based on the configuration space(C-space)generated from large-scale digital twinning.Leveraging GPU-based parallelism,the C-space of a multi-degree-of-freedom(multi-DoF)manipulator in a complex task space with obstacles can be mapped out through extensive simulation of motion and collision of multiple virtual robot arms known as digital twins.An optimal search algorithm is incorporated with artificial potential field generated in the C-space to allow the prioritising of safety in accordance with the varying risks associated with the obstacles by means of variable repulsive potential.To extend the high-degree path to smooth and continuous joint trajectories,a spline operation is applied.Finally,a 7-DOF physical manipulator is deployed for the execution of the planned trajectory in a task space flled with ob-stacles.Results demonstrated a 16.3%improvement in success rate achieved by utilising the safety-prioritisable search algo-rithm.With this unifed formulation of the control and planning problem in the C-space,the kinematics complexity of a large DOF manipulator in obstacle-present task space could be truly relieved from the joint control loop.This simplification,in turn,opens up prospective work in dynamic reconstruction of the C-space.
文摘This article addresses the issue of computing the constant required to implement a specific nonparametric subset selection procedure based on ranks of data arising in a statistical randomized block experimental design. A model of three populations and two blocks is used to compute the probability distribution of the relevant statistic, the maximum of the population rank sums minus the rank sum of the “best” population. Calculations are done for populations following a normal distribution, and for populations following a bi-uniform distribution. The least favorable configuration in these cases is shown to arise when all three populations follow identical distributions. The bi-uniform distribution leads to an asymptotic counterexample to the conjecture that the least favorable configuration, i.e., that configuration minimizing the probability of a correct selection, occurs when all populations are identically distributed. These results are consistent with other large-scale simulation studies. All relevant computational R-codes are provided in appendices.
基金Supported by National Natural Science Foundation of China(Grant Nos.U21B6002 and 52025054)。
文摘Autonomous aerial refueling technology is gaining increasing attention to enhance aircraft combat capabilities.Current research on autonomous refueling focuses mainly on flight control laws,with little attention to the automation of refueling pipes.This leads to high demands on control law performance and navigation accuracy,making it difficult to ensure reliability.To address this,we propose a robotic arm system capable of automatic docking during the flexible aerial refueling process.The system uses a conical kinematic space configuration,offering enhanced stability and impact resistance.The frame-type structure achieves a lightweight design.Additionally,we establish a single-objective optimization model for the connecting rod dimensions and apply a genetic algorithm(GA)for their optimization.We also propose a trajectory-fitting calibration theory based on the robotic arm's special configuration and complete its movement accuracy calibration using a laser tracker.This calibration method reduces the robotic arm's motion error by 71%,achieving an absolute positioning accuracy better than 3.5 mm,which meets the requirements for autonomous aerial refueling.In summary,this research presents a hybrid robotic arm that meets automatic docking requirements,offering a new approach to autonomous aerial refueling.
文摘In the context of robotics, configuration space （c- space） is widely used for non-circular robots to engage tasks such as path planning, collision check, and motion planning. In many real-time applications, it is important for a robot to give a quick response to the user＇s command. Therefore, a constant bound on planning time per action is severely im- posed. However, existing search algorithms used in c-space gain first move lags which vary with the size of the under- lying problem. Furthermore, applying real-time search algo- rithms on c-space maps often causes the robots being trapped within local minima. In order to solve the above mentioned problems, we extend the learning real-time search （LRTS） algorithm to search on a set of c-space generalized Voronoi diagrams （c-space GVDs）, helping the robots to incremen- tally plan a path, to efficiently avoid local minima, and to ex- ecute fast movement. In our work, an incremental algorithm is firstly proposed to build and represent the c-space maps in Boolean vectors. Then, the method of detecting grid-based GVDs from the c-space maps is further discussed. Based on the c-space GVDs, details of the LRTS and its implemen- tation considerations are studied. The resulting experiments and analysis show that, using LRTS to search on the c-space GVDs can 1） gain smaller and constant first move lags which is independent of the problem size; 2） gain maximal clear- ance from obstacles so that collision checks are much re- duced; 3） avoid local minima and thus prevent the robot from visually unrealistic scratching.
文摘An efficient path planning algorithm based on topologic method is presented in this paper.The colli- sion free path planning for three-joint robotic arm consists of three parts:partition of C-space,construc- tion of CN and search for a path in CN.We mainly solved the problems of partitioning the C-space and judging the connectivity between connected blocks,etc.For the motion planning of a robotic arm with a gripper,we developed the concepts of global planning and local planning,and discussed the basic fac- tors for constructing the planning system.In the paper,some evaluation and analysis of the complexity and reliability of the algorithm are given,together with some ideas to improve the efficiency and increase the reliability.At last,some experimental results are presented to show the efficiency and accuracy of the nigorithm.
文摘This paper presents a direct 3D painting algorithm for polygonalmodels in 3D object-space with a metaball-based paintbrush in virtual environment.The user is allowed to directly manipulate the parameters used to shade the surfaceof the 3D shape by applying the pigment to its surface with direct 3D manipulationthrough a 3D flying mouse.
基金Supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130141120036)the International Postdoctoral Exchange Fellowship Program(2013)the Fundamental Research Funds for the Central Universities
文摘By using the Mecke identity, we study a class of birth-death type Dirichlet forms associated with the mixed Poisson measure. Both Poincare and weak Poincare inequalities are established, while another Poincare type inequality is disproved under some reasonable assumptions.
