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51.
In this paper, we present a general method to calculate the inverse and direct dynamic models of parallel robots. The models
are expressed in a closed form by a single equation in which all the elements needed are expressed. The solution is given
in terms of the dynamic models of the legs, the dynamics of the platform and some Jacobian matrices. The proposed method is
applied in this paper on two parallel robots with different structures.
Categories (2), (3). 相似文献
52.
Average consensus in networks of dynamic agents with switching topologies and multiple time-varying delays 总被引:5,自引:0,他引:5
In this paper, we discuss average consensus problem in undirected networks of dynamic agents with fixed and switching topologies as well as multiple time-varying communication delays. By employing a linear matrix inequality method, we prove that all the nodes in the network achieve average consensus asymptotically for appropriate communication delays if the network topology is connected. Particularly, several feasible linear matrix inequalities are established to determine the maximal allowable upper bound of time-varying communication delays. Numerical examples are given to demonstrate the effectiveness and the sharpness of the theoretical results. 相似文献
53.
Akiyoshi Wakatani 《Parallel Computing》2004,30(12):1345-1359
It is hard to implement the ADI method in an efficient way on distributed-memory parallel computers. We propose “P-scheme” which parallelizes a tridiagonal linear system of equations for the ADI method, but its effectiveness is limited to the cases where the problem size is large enough mainly because of the communication cost of the propagation phase of the scheme.
In order to overcome this difficulty, we propose an improved version of the P-scheme with “message vectorization” which aggregates several communication messages into one and alleviates the communication cost. Also we evaluate the effectiveness of message vectorization for the ADI method and show that the improved version of the P-scheme works well even for smaller problems and linear and super-linear speedups can be achieved for 8194 × 8194 and 16,386 × 16,386 problems, respectively. 相似文献
54.
55.
The fracture toughness of brittle thermoset resins could be improved significantly by perfectly bonded tough, short fibers through both crack trapping and bridging effects. In this paper, the crack trapping effect was studied through the analysis of the change of strain energy associated with the crack propagation across a regular array of fibers, and the bridging effect was discussed based on the Andersson–Bergkvist model. The fracture resistance increases with the fiber volume fraction, and is independent of the elastic properties of the matrix, the crack length, and the cross-sectional diameter of the fibers. 相似文献
56.
可拓学、灰色系统、界壳论、集对分析和消错学这五大新兴智能基础学科都是我国首创的理论。本文首先简单介绍了五大学科,随后给出了五大学科的关系矩阵并讨论了其交叉应用的发展概况,最后对其交叉所产生的空白领域追行了初步的探讨,然后对其未来发展进行了展望。 相似文献
57.
Discussed in this paper is the Cartesian stiffness matrix, which recently has received special attention within the robotics
research community. Stiffness is a fundamental concept in mechanics; its representation in mechanical systems whose potential
energy is describable by a finite set of generalized coordinates takes the form of a square matrix that is known to be, moreover,
symmetric and positive-definite or, at least, semi-definite. We attempt to elucidate in this paper the notion of “asymmetric
stiffness matrices”. In doing so, we show that to qualify for a stiffness matrix, the matrix should be symmetric and either
positive semi-definite or positive-definite. We derive the conditions under which a matrix mapping small-amplitude displacement
screws into elastic wrenches fails to be symmetric. From the discussion, it should be apparent that the asymmetric matrix
thus derived cannot be, properly speaking, a stiffness matrix. The concept is illustrated with an example. 相似文献
58.
利用美国SSI公司研制的COMPN模拟软件对双重孔隙介质油藏一种重要的开采机理 吸渗排油进行了模拟研究,考察了一个基质岩块为四周裂缝所包围时.在驱动压力和毛管压力的不同平衡(驱动压力和毛管压力的相对大小)关系下的水驱油采收率和水驱油效率的变化规律. 相似文献
59.
60.
The effect of particle distribution on damage formation in particulate reinforced metal matrix composites deformed in compression 总被引:1,自引:0,他引:1
P.B. Prangnell S.J. Barnes S.M. Roberts P.J. Withers 《Materials Science and Engineering: A》1996,220(1-2):41-56
Image analysis results are reported on the generation of damage in particulate reinforced metal matrix composites during compressive deformation. The technique allows the automated collection of data on the incidence of particle fracture and void formation in the matrix as a function of important microstructural parameters such as local particle volume fraction and particle size. There is a strong relationship between damage and the local volume fraction of the reinforcement proving that damage formation is accentuated in regions of particle clustering. With the SiC reinforced materials examined, there was observed to be a change in dominance of damage mechanism from particle fracture at low local volume fractions to void formation in the matrix within strongly clustered regions. The results are compared with finite element (FE) modelling of the compressive deformation of clustered particles using a simple cluster of equi-spaced particles. The FE results suggest that plastic flow is generally inhibited in clustered regions. In certain highly clustered configurations shielding is such that flow does not occur in the heart of the cluster even at high levels of average plastic strain. The modelling suggests that the change in dominance of damage mechanism is related to the dramatic increase in tensile hydrostatic stresses in the matrix with higher levels of particle clustering. 相似文献