The objective of this study is to develop a method for mobile robot motion planning in the presence of moving obstacles. The concept of traversability vectors is used to analyze the spatial relationship between the ro...
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The objective of this study is to develop a method for mobile robot motion planning in the presence of moving obstacles. The concept of traversability vectors is used to analyze the spatial relationship between the robot and moving obstacles. Given a predefined path, the occupancy of the path by moving obstacles can be detected and registered on the constraint map. Obstacles on this map represent time constraints on the robot motion along the path. A search algorithm is then developed to coordinate the robot motion. Simulation results for this approach are discussed.< >
The advantages of the object-oriented data model Cosmos as a conceptual modeling facility for distributed database architectures are highlighted. It is shown that this data model not only offers the possibility of def...
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The advantages of the object-oriented data model Cosmos as a conceptual modeling facility for distributed database architectures are highlighted. It is shown that this data model not only offers the possibility of defining highly structured abstract constructs but also provides a general-purpose programming environment for the definition of additional operations upon already existing heterogeneous data. The problem of extracting information from existing heterogeneous data representations is also addressed, and the use of a two-layered approach is suggested. In the two-layered quintessence model architecture the user can utilize highly structured objects at the upper layer, while all interschema and interlanguage transformations are performed in a transparent manner at the lower layer. A two-layered model configuration is introduced for the case of semidecentralized distributed heterogeneous information systems and it is explained how its lower layer is in a position to map heterogeneous host schemas to each other.< >
The authors extend their previous effort in visualizing the spatial aspect of relativistic effects, and treat the phenomenon of time dilation, an inherent temporal effect of special relativity. Here, the authors demon...
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The authors extend their previous effort in visualizing the spatial aspect of relativistic effects, and treat the phenomenon of time dilation, an inherent temporal effect of special relativity. Here, the authors demonstrate through still-frame images and live animations that, in observing the viewing-independent time dilation, the finite light transit time involved in performing the observation makes the observed time dilation also depend on the viewing condition. As the authors introduce the physics of special relativity into ray-tracing and make time to pass as a ray travels through space, they are able to link the spatial and temporal dimensions in a fundamental and consistent way in their simulations, and generate images that reveal the spatial and temporal properties of the 4D geometry of spacetime. The present exploration highlights the interplay of the imaging process and the imaged physical events in producing the final images.< >
作者：
JOU, JYBOVIK, ACLaboratory for Vision Systems
Computer and Vision Research Center Department of Electrical and Computer Engineering The University of Texas at Austin Austin Texas 78712-1084 USA
Techniques are described for improving the speed and accuracy of iterative visible-surface reconstruction algorithms. In particular, the importance of obtaining accurate early information is emphasized, both in the in...
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Techniques are described for improving the speed and accuracy of iterative visible-surface reconstruction algorithms. In particular, the importance of obtaining accurate early information is emphasized, both in the initial surface approximation and in the early localization of surface discontinuities. The first of these goals is attained using a simple technique known as constraint expansion , which yields a good initial approximation while accounting for detected discontinuities. The second goal is attained by using the locations of the image irradiance edges as a guide in locating potential discontinuities. Discontinuity detection in later stages of computation is augmented by a double-thresholding strategy and discontinuity backtracking.
作者：
CLARK, MBOVIK, ACLaboratory for Vision Systems
Computer and Vision Research Center Department of Electrical and Computer Engineering The University of Texas at Austin Austin TX 78712-1084 U.S.A
In this paper we apply a previously developed model of texture segmentation using multiple spatially and spectrally localized filters, known as Gabor filters, to the analysis of textures composed of elementary image f...
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In this paper we apply a previously developed model of texture segmentation using multiple spatially and spectrally localized filters, known as Gabor filters, to the analysis of textures composed of elementary image features known as textons. It is found that for regularly- or irregularly-spaced texton patterns, the segmentation approach works well, in the sense that it is in accordance with visual segmentation. Differences in texton spacing, size, orientation, and phase are all found to lead to successful segmentations.
In this paper, a heuristic and learning, algorithmic scheme for collision-free navigation is presented. This scheme determines an optimum collision-free navigation path of an autonomous platform by using a 'trial ...
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In this paper, a dynamic model of a robot manipulator is first derived based on the Euler-Lagrange equation and a state-space representation is derived for it. A number of non-adaptive robot control schemes are then r...
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In this paper, a dynamic model of a robot manipulator is first derived based on the Euler-Lagrange equation and a state-space representation is derived for it. A number of non-adaptive robot control schemes are then reviewed. A robust decentralized control is then proposed for a 5-axis robot manipulator. Numerical simulation results are presented to verify the theory.
The robust controller has very simple structures and can be divided into two separate parts: a servo controller and an auxiliary controller. The two controllers are designed independently. The function of the auxiliar...
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The robust controller has very simple structures and can be divided into two separate parts: a servo controller and an auxiliary controller. The two controllers are designed independently. The function of the auxiliary controller is to cancel out the plant uncertainties directly without the use of the high loop gain principle. Interpretation of robot controller as a signal-synthesis adaptive controller is given. Practical implementation issues of the auxiliary controller are discussed. Simulations of a design example with large parameter uncertainty, nonlinearity, and external disturbance are presented to demonstrate the effectiveness of the design technique. This technique is further tested with success in an experimental study of joint position control of a PUMA 560 robot arm.< >
Control of tool-workpiece interaction force is of vital importance in automated assembly. Using a simple linear continuous model of an edge-following system to predict the appropriate accomodation gains in a force con...
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Control of tool-workpiece interaction force is of vital importance in automated assembly. Using a simple linear continuous model of an edge-following system to predict the appropriate accomodation gains in a force control loop, previous work has shown that force control by accomodation is feasible. Following up this work, this paper describes the analysis, simulation and implementation of an adaptive force control in a two-dimensional edge-following task with a PUMA 560 robot and wrist force sensor. First, a discrete-time model of an edge-following system is developed and then used as the plant; second, a model reference adaptive control (MRAC) scheme is applied to achieve both tracking and regulation purposes. The reference (tracking) model can be determined by experimental reference input and desired model output information; the reference (regulation) model can be obtained by simulation to smooth out the plant output and improve the augmented filtered plant-model error. Study is done on the values of the adaptation gains in the adaptive mechanism, and hence can be adjusted to insure the best plant output performance.
A hardware and software methodology for the design of the three interactive levels of intelligent robotic systems is proposed. The organization level is modeled as an expert system, the coordination level as a loosely...
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