A general two-phase coordinated planning and control algorithm is developed to determine optimal motions among obstacles and dynamic objects in a shared environment. The algorithm consists of a two-phase approach: pla...
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(纸本)0818685484
A general two-phase coordinated planning and control algorithm is developed to determine optimal motions among obstacles and dynamic objects in a shared environment. The algorithm consists of a two-phase approach: planning a global path for each object subject to the constraints of the workspace and then locally optimizing along each global path to minimize some process dependent cost function. The order in which objects are planned will also affect the overall performance of the system. The algorithm is applied to a simulated surface-mount assembly system. The results show an improvement over other planning and control methods.
Existing data models and design principles for temporal databases are based on the assumption that a temporal data is associated with an interval as well as its sub-intervals. This type of temporal data is called homo...
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Existing data models and design principles for temporal databases are based on the assumption that a temporal data is associated with an interval as well as its sub-intervals. This type of temporal data is called homogeneous data. A temporal data which is associated with an interval, but not its sub-intervals, is called a non-homogeneous data. Existing data models cannot capture non-homogeneous data accurately, and the existing design principles are not applicable in temporal databases that contain non-homogeneous data. In this dissertation, the relational data model is extended to support both homogeneous and non-homogeneous data. A design principle which avoids inconsistency in temporal databases, that contain homogeneous data as well as non-homogeneous data, is studied. In the proposed extension of the relational data model, temporal relations are classified into two types; property relations and representative relations. A tuple in a property relation is associated with the valid time and its sub-intervals, while a tuple in a representative relation is associated with only the whole interval of its valid time. Thus, the valid time in a property relation is decomposable, but the valid time in a representative relation is not. Based on this characteristics, the valid time in a property relation and that in a representative relation cannot be used in the same manner. In the extension of relational algebra for temporal relations, the calculation of the valid time in a relation, created by relational operators, is determined by the types of the temporal relations. Thus, it guarantees proper use of the valid time. A type of inconsistency, called P-inconsistency, can occur in temporal databases with homogeneous and non-homogeneous data. A normal form, called P-consistency Normal Form (PCNF), which avoids P-inconsistency, is proposed in this dissertation. PCNF is based on types of attributes, functional dependencies, and property dependencies (P-dependencies), in tempor
A new computer algorithm for the reliable calculation of an ill-conditioned van der Mend matrix (VDMM) is presented where the determinant of the VDMM is found by calculation of its miners. Two numerical examples illus...
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A new computer algorithm for the reliable calculation of an ill-conditioned van der Mend matrix (VDMM) is presented where the determinant of the VDMM is found by calculation of its miners. Two numerical examples illustrate the method's application. One, where the determinant of a third-order equation is analyzed, gives a simple illustration of the technique. The second, where the order of the equation analyzed is raised to 40, shows the advantages of the proposed method compared to the standard one. (C) 1997 Elsevier Science Limited.
A discrete-time adaptive sliding mode controller for linear systems represented by the state space is presented. The controller is developed using the delta operator, which is better for approximating continuous-time ...
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A discrete-time adaptive sliding mode controller for linear systems represented by the state space is presented. The controller is developed using the delta operator, which is better for approximating continuous-time systems than the shift operator. The use of the delta model allows the selection of the sliding surface to be similar to that for the continuous-time case. It is shown that the adaptive control algorithm leads to a stable closed-loop system. Simulation results are presented to illustrate the features of the proposed control scheme.
Software visualization is the systematic and imaginative use of the technology of interactive computer graphics and the disciplines of graphic design, typography, color, cinematography, animation, and sound design to ...
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Software visualization is the systematic and imaginative use of the technology of interactive computer graphics and the disciplines of graphic design, typography, color, cinematography, animation, and sound design to enhance the comprehension of algorithms and computer programs. This article demonstrate that, graphical and auditory representations of programs' are useful in debugging and can enliven and enrich programming as a cognitively accessible multimedia experience. To illustrate these ideas, authors present three visualization approaches -- algorithm animation, typographic source code presentation, and interactive auralization for debugging. The three software visualization approaches described here are useful for debugging. Carefully crafted algorithm animations can show how programs work; enhanced typographic representations can improve the readability and comprehensibility of source code; and an interactive environment can let programmers specify software visualizations, including audio portraits of running programs.
In this article, the system dynamics of a realistic plastic extrusion process is identified by least squares approximation associated with loss and covariance function criteria applied to a set of experimentally measu...
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In this article, the system dynamics of a realistic plastic extrusion process is identified by least squares approximation associated with loss and covariance function criteria applied to a set of experimentally measured data of true single-screw extrusion processes. The system identification yields a third-order mathematical model of the process with a single-input/single-output nature. This modeling approach leads to a reliable and effective system model which facilitates the control design. In designing the control algorithm, the derived dynamic model is formulated in the state-space form to obtain the required Riccati equation. Then, an integral observer control methodology is performed. To reduce the computation time, a program which simulates deterministic model and controller design is proposed. In addition, a steady-state matrix based on the algebraic Riccati equations is utilized to design the controller gain matrices. Finally, the observer design methodology employing the observer characteristic equation corresponding to each system matrix is elaborated. The simulation results show that the two controller output data, namely pressure and temperature responses, track the desired values satisfactorily.
Implementation issues represent an unfamiliar challenge to most control engineers, and many techniques for controller design ignore these issues outright. Consequently, the design of controllers for smart structural s...
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Implementation issues represent an unfamiliar challenge to most control engineers, and many techniques for controller design ignore these issues outright. Consequently, the design of controllers for smart structural systems usually proceeds without regard for their eventual implementation, thus resulting either in serious performance degradation or in hardware requirements that squander power, complicate integration, and drive up cost. The level of integration assumed by the smart patch further exacerbates these difficulties, and any design inefficiency may render the realization of a single-package sensor-controller-actuator system infeasible. The goal of this research is to automate the controller implementation process and to relieve the design engineer of implementation concerns like quantization, computational efficiency, and device selection. Field programmable gate arrays (FPGA) are specifically targeted as a hardware platform because these devices are highly flexible, power efficient, and reprogrammable. The current study develops an automated implementation sequence that minimizes hardware requirements while maintaining controller performance. Beginning with a state space representation of the controller, the sequence automatically generates a configuration bitstream for a suitable FPGA implementation. MATLAB functions optimize and simulate the control algorithm before translating it into the VHSIC hardware description language (VHDL). These functions improve power efficiency and simplify integration in the final implementation by performing a linear transformation that renders the controller computationally friendly. The transformation favors sparse matrices in order to reduce multiply operations and the hardware necessary to support them;simultaneously, the remaining matrix elements take on values that minimize limit cycles and parameter sensitivity. The proposed controller design methodology is implemented on a simple cantilever beam test structure using
An experimental method is presented to optimize the control algorithm for a closed-loop adaptive-optics system employed with an astronomical telescope. The technique uses wave-front sensor measurements from an indepen...
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An experimental method is presented to optimize the control algorithm for a closed-loop adaptive-optics system employed with an astronomical telescope. The technique uses wave-front sensor measurements from an independent scoring sensor to calculate adjustments to the wave-front reconstruction algorithm and the bandwidth of the adaptive-optics control loop that will minimize the residual mean-square phase distortion as measured by this sensor. Specifying the range of possible adjustments defines the class of control algorithms over which system performance will be optimized. In particular, the technique can be used to compute an optimized wave-front reconstruction matrix for use with a prespecified adaptive-optics control-loop bandwidth, optimize the control-loop bandwidth for a given reconstruction matrix, optimize the individual modal control bandwidths for a fixed modal reconstructor, or simultaneously optimize both the wave-front modes and their associated control bandwidths for a fully optimized modal control algorithm. The method applies to closed loop adaptive-optics systems that incorporate one or more natural or laser guide stars and one or more deformable mirrors that are optically conjugate to distinct ranges along the propagation path. Initial experimental results are reported for the case of a hybrid adaptive-optics system incorporating one natural guide star, one laser guide star, and one deformable mirror. These results represent what is to the authors' knowledge the first stable closed-loop operation of an adaptive-optics system using multiple guide stars. (C) 1997 Optical Society of America.
This article focuses on a study which presented an improved algorithm for solving the economic lot size problem. S. G. Davis, in his study An improved algorithm for solving the economic lot size problem, presents an a...
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This article focuses on a study which presented an improved algorithm for solving the economic lot size problem. S. G. Davis, in his study An improved algorithm for solving the economic lot size problem, presents an algorithm for solving the single-facility, multi-product lot scheduling problem minimizing setup and inventory costs subject to a capacity constraint. The example of the ten-product Bomberger problem, which has already been investigated quite often for over 40 years, indicates that his two-stage procedure can lead to solutions with lower costs than those of earlier analyses in acceptable computation times. The three following modifications of Davis' original idea permit a more a more efficient programming. These modifications are active consideration of setup times in step 3 of stage 1, use of a heap structure in step 3 of stage 1 and direct construction of the optimal solution of model 2b in stage 2. To demonstrate the saving in computation time by the suggested modifications a 100-product problem was created by replacing each of the original products by ten equal products having 10% of the original demand each. The results demonstrate the improvement of the procedure suggested by Davis concerning the computation time.
Pneumatic robot manipulators are characterized by high-order, time-variant actuator dynamics, nonlinearities due to compressibility of air;external disturbances such as static and Coulomb friction, and wide range of p...
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Pneumatic robot manipulators are characterized by high-order, time-variant actuator dynamics, nonlinearities due to compressibility of air;external disturbances such as static and Coulomb friction, and wide range of payload variations. Conventional PID controllers suffer from problems of gain tuning under these conditions. In this paper a new control algorithm is proposed for the position and trajectory control of pneumatic actuators based on the sliding mode control approach. The stability of motion is proved for the case of a linear, time-invariant switching surface. A disadvantage of using sliding mode control for third-and higher-order mechanical systems is the need for acceleration feedback. In this paper to overcome this difficulty we propose the use of differential pressure. The proposed controller is simple, easy to implement, and robust to payload and parametric variations. The effectiveness of the new scheme for position and trajectory control is illustrated by experiments on an industrial piston-driven cylindrical actuator with proportional valves.
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