A feature-constrained stereo matching algorithm for lunar rover navigation is presented based on the analysis of the stereo vision system and working environments of lunar rover. In feature-matching phase, edge points...A feature-constrained stereo matching algorithm for lunar rover navigation is presented based on the analysis of the stereo vision system and working environments of lunar rover. In feature-matching phase, edge points are extracted with wavelet transform and are used as the primitives for matching. Then three criterions are utilized in turn to select the correct matching points with the pyramidal searching strategy. As a result,the algorithm finds corresponding points successfully for large numbers of edge points. Area-matching is accomplished under the constraint of edge-matching results,and the correlation is selected as the criterion.Experimental results with real images of natural terrain indicate that the algorithm provides dense disparity maps with fairly high accuracy.展开更多
By using the conformal method, solutions of the Einstein-scalar ficld gravitational constraint equations are obtained. Handling scalar fields is a bit more challenging than handling matter fields such as fluids, Maxwe...By using the conformal method, solutions of the Einstein-scalar ficld gravitational constraint equations are obtained. Handling scalar fields is a bit more challenging than handling matter fields such as fluids, Maxwell fields or Yang-Mills fields, because the scalar field introduces three extra terms into the Lichnerowicz equation, rather than just one. The proofs are constructive and allow for arbitrary dimension （〉 2） as well as low regularity initial data.展开更多
Inflatable membrane antennas have been extensively applied in space missions;however,the simulation methods are not perfect,and many simulation methods still have many difficulties in accuracy,efficiency,and stability...Inflatable membrane antennas have been extensively applied in space missions;however,the simulation methods are not perfect,and many simulation methods still have many difficulties in accuracy,efficiency,and stability.Therefore,the extended position-based dynamics(XPBD)method is employed and improved for the simulation of folded inflatable structures in this paper.To overcome the problem that the original XPBD method with only geometric constraints does not contain any mechanical information and cannot reflect the mechanical characteristics of the structure,we improve the XPBD method by introducing the strain energy constraint.Due to the complicated nonlinear characteristics of the membrane structures,the results with the traditional finite element method(Abaqus)cannot converge,while the tension field theory(TFT)can,but some pretreatments are needed.Compared with them,the method in this paper is simple and has better stability to accurately predict the displacement,stress,and wrinkle region of the membrane structure.In addition,the present method is also compared with the experiment in the reference to verify the feasibility of the folded tube simulation.Finally,the present method is applied to simulate inflatable membrane antennas and analyze the deployable driving force and deployable process sequence of each component.展开更多
文摘A feature-constrained stereo matching algorithm for lunar rover navigation is presented based on the analysis of the stereo vision system and working environments of lunar rover. In feature-matching phase, edge points are extracted with wavelet transform and are used as the primitives for matching. Then three criterions are utilized in turn to select the correct matching points with the pyramidal searching strategy. As a result,the algorithm finds corresponding points successfully for large numbers of edge points. Area-matching is accomplished under the constraint of edge-matching results,and the correlation is selected as the criterion.Experimental results with real images of natural terrain indicate that the algorithm provides dense disparity maps with fairly high accuracy.
基金Project supported by NSF Grant PHY-0354659 at the University of Oregonby NSF Grant DMS-0305048 at the University of Washington.
文摘By using the conformal method, solutions of the Einstein-scalar ficld gravitational constraint equations are obtained. Handling scalar fields is a bit more challenging than handling matter fields such as fluids, Maxwell fields or Yang-Mills fields, because the scalar field introduces three extra terms into the Lichnerowicz equation, rather than just one. The proofs are constructive and allow for arbitrary dimension （〉 2） as well as low regularity initial data.
基金supported by the National Natural Science Foundation of China(Grant Nos.11922203 and 11772074).
文摘Inflatable membrane antennas have been extensively applied in space missions;however,the simulation methods are not perfect,and many simulation methods still have many difficulties in accuracy,efficiency,and stability.Therefore,the extended position-based dynamics(XPBD)method is employed and improved for the simulation of folded inflatable structures in this paper.To overcome the problem that the original XPBD method with only geometric constraints does not contain any mechanical information and cannot reflect the mechanical characteristics of the structure,we improve the XPBD method by introducing the strain energy constraint.Due to the complicated nonlinear characteristics of the membrane structures,the results with the traditional finite element method(Abaqus)cannot converge,while the tension field theory(TFT)can,but some pretreatments are needed.Compared with them,the method in this paper is simple and has better stability to accurately predict the displacement,stress,and wrinkle region of the membrane structure.In addition,the present method is also compared with the experiment in the reference to verify the feasibility of the folded tube simulation.Finally,the present method is applied to simulate inflatable membrane antennas and analyze the deployable driving force and deployable process sequence of each component.
