We present a canonical frame construction for determining projectively invariant indexing functions for non-algebraic smooth plane curves. These invariants are semi-local rather than global, which promotes tolerance t...
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Parametric transfer-function matrix (T.F.M.) models are derived from the differential equations describing the variation of liquid and vapour compositions within symmetrical distillation columns separating binary mixt...
Parametric transfer-function matrix (T.F.M.) models are derived from the differential equations describing the variation of liquid and vapour compositions within symmetrical distillation columns separating binary mixtures. Both packed and tray-type columns are considered, the models developed having minimal order 6 and 4, respectively, (implying perfectly-stirred mixtures and minimum number of trays in each column section), so removing the complications introduced by spatial variations encountered in earlier studies by Edwards and Tabrizi [1] and Tabrizi [2] of longer columns. The T.F.M.'s obtained are again shown to be diagonal with the same choice of input and output vectors as were employed in the "long" column studies. Furthermore, the fundamental behavioural differences between packed and tray-type columns are again revealed using these low-order physical models as were demonstrated in the previous studies. In particular, the sign of the static gain of packed-columns, responding to total flow changes, is again shown to be parameter-sensitive and the sign of the total-flow gain at high-frequency is shown to be the reverse of that for tray-type columns, so again causing non-minimum-phase behaviour in packed-columns in some circumstances. Because of their behavioural and parametric similarities, it is proposed that the minimal-order models developed in this paper be used as a future basis for control system design studies for spatially-distributed and multi-tray columns in situations where travelling-wave phenomena are unimportant. The present paper has revealed a precise diagonal dynamic structure for symmetrical columns using the same inputs and outputs. This deduction accords well with the findings of previous authors based on part impirical by McMoran [3], Shinskey [4], and Stainthorp [5], approximate analytical by Edwards [6], or purely simulation methods Rosenbrock [7]. Near first-order-lag behaviour is also a feature common to the findings of these earlier
Recognising a curved surface from its outline in a single view is a major open problem in computer vision. This paper shows techniques for recognising a significant class of surfaces from a single perspective view. Th...
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Harmonic functions are used in conjunction with velocity-based control to implement a robot system that is flexible in coping with errors in the environment model and in robot positions. Harmonic functions provide a m...
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Harmonic functions are used in conjunction with velocity-based control to implement a robot system that is flexible in coping with errors in the environment model and in robot positions. Harmonic functions provide a method for implementing potential-field path planning. Since they produce smooth vector fields that are free of spurious local minima, they also provide an ideal mechanism for implementing velocity-based control. The resulting control system is termed harmonic control. The strategy described provides a robust means of controlling a manipulator in the presence of external forces. A system that simulates velocity control of a two-link revolute robot arm is presented.< >
The problem of dual-arm manipulation planning is to plan the path of two cooperating robot arms to carry a moveable object from a given initial configuration to a given goal configuration amidst obstacles. The authors...
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The problem of dual-arm manipulation planning is to plan the path of two cooperating robot arms to carry a moveable object from a given initial configuration to a given goal configuration amidst obstacles. The authors survey previous work in manipulation planning and relate it to this analysis. A formal configuration space presentation of the problem is given. Three implemented planners are described. These three planners operated in a two-dimensional workspace and addressed increasingly difficult versions of the dual-arm manipulation problem. They were implemented in the C language. Execution times given were obtained by running them on a DEC 5000 workstation.< >
The problem of partitioning an assembly of polyhedral objects into two subassemblies that can be separated arises in assembly planning. The authors describe an algorithm to compute the set of all translations separati...
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The problem of partitioning an assembly of polyhedral objects into two subassemblies that can be separated arises in assembly planning. The authors describe an algorithm to compute the set of all translations separating two polyhedra with n vertices in O(n/sup 4/) steps and show that this is optimal. Given an assembly of k polyhedra with a total of n vertices, an extension of this algorithm identifies a valid translation and removable subassembly in O(k/sup 2/n/sup 4/) steps if one exists. Based on the second algorithm, a polynomial time method for finding a complete assembly sequence consisting of single translations is derived. An implementation incorporates several changes to achieve better average-case performances. Experimental results obtained for composite objects consisting of isothetic polyhedra are described.< >
A method for converting a series of line segments generated by a high-level path planner for an AGV to a combination of continuous smooth curves and straight line paths is presented. Ideally, the straight line path se...
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A method for converting a series of line segments generated by a high-level path planner for an AGV to a combination of continuous smooth curves and straight line paths is presented. Ideally, the straight line path segments should be connected by circular arcs. The AGV's angular velocity along the straight paths is zero and will not smoothly connect the angular velocity moments required to traverse the circular arcs. Therefore, a transition curve (clothoid) needs to be generated to smoothly connect these angular moments. A technique for computing the clothoid transition curves for an AGV to execute is given. The method was implemented on a Macintosh II computer and was used to control a mobile robot.< >
Motivation for using harmonic functions as solutions to Laplace's equation arose from the resulting prevention of spurious local minima. Harmonic functions are shown to have several more useful properties that mak...
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Motivation for using harmonic functions as solutions to Laplace's equation arose from the resulting prevention of spurious local minima. Harmonic functions are shown to have several more useful properties that make them well suited for robotics applications such as fast surface normal computation, completeness, ability to exhibit different modes of behavior, and robust control in the presence of unanticipated obstacles and errors. A system that demonstrates this usefulness for control of a revolute robot arm is discussed.< >
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