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COORDINATING LOCOMOTION AND MANIPULATION OF A MOBILE MANIPULATOR

IEEE TRANSACTIONS ON AUTOMATIC CONTROL 1994年第6期39卷 1326-1332页

作者： YAMAMOTO, Y YUN, XP General Robotics and Active Sensory Perception(GRASP) Laboratory University of Pennsylvania Philadelphia PA USA

A mobile manipulator in this study is a manipulator mounted on a mobile platform. Assuming the end point of the manipulator is guided, e.g., by a human operator to follow an arbitrary trajectory, it is desirable that the mobile platform is able to move as to position the manipulator in certain preferred configurations. Since the motion of the manipulator is unknown a priori, the platform has to use the measured joint position information of the manipulator for its own motion planning. This paper presents a control algorithm for the platform so that the manipulator is always positioned at the preferred configurations measured by its manipulability. Simulation results are presented to illustrate the efficacy of the algorithm. The algorithm is also implemented and verified on a real mobile manipulator system. The use of the resulting algorithm in a number of applications is also discussed.

关键词： dynamics feedback matrix algebra path planning position control feedback control joint position information locomotion coordination manipulability mobile manipulator mobile platform motion planning robots Feedback moving platform Position control feedback control computer algorithms matrix algebra dynamics Path planning POSITION INFORMATION motion planning Platform maneuverability Robot Manipulators Mobile manipulator

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FUZZY CONTROL FOR A NONLINEAR MIMO PLANT SUBJECT TO CONTROL CONSTRAINTS

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IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS 1994年第10期24卷 1565-1571页

作者： STEYN, WH Department of Electrical and Electronic Engineering University of Stellenbosch Stellenbosch South Africa

A rule based fuzzy controller is presented for attitude stabilization of a small satellite in low earth orbit. Active control is done by using 3-axis magneto-torquing. A prefered torque vector can not always be generated from the magnetic coils in certain regions of the orbit, due to an unfavourable direction of the geomagnetic field vector. The main objective of an acceptable control algorithm will then be to optimize the control effort: maximize the desired influence on the controlled axis and minimize the undesired disturbances to the other axes. It was found that a fuzzy controller can achieve these goals in a computationally effective way, compared to other more involved MIMO algorithms, while performing just as well or better under similar conditions. This fuzzy controller solves the control constraint problem by chosing the best magneto- torquer, the polarity and switching instances.

关键词： Fuzzy Constraint Controllers polarity active control magnetic coils computer algorithms small satellites FUZZY CONTROLLER multiple input multiple output systems Fuzzy control

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ROBUSTNESS OF UNMODIFIED STOCHASTIC ADAPTIVE-CONTROL algorithms

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IEEE TRANSACTIONS ON AUTOMATIC CONTROL 1994年第2期39卷 396-400页

作者： RADENKOVIC, MS BIALASIEWICZ, JT Department of Electrical Engineering University of Colorado Denver Denver CO USA

Originally, adaptive control theory was developed for the ideal system models, i.e., linear system models under the assumption that relative degree and upper bounds on the order of the systems are known. At the beginning of the last decade, adaptive control algorithms designed for such ideal system models were strongly attacked by many researchers due to ''lack of robustness'' in the presence of unmodeled dynamics and external disturbances. The purpose of the present paper is to relax existing constant pressure on the adaptive control algorithms originally designed for the ideal system models. It is shown that such adaptive control algorithms are globally stable and robust with respect to unmodeled dynamics and external disturbances without any modifications, such as isigma-modification, epsilon1-modification, relative dead-zone, projection of the parameter estimates, etc. Global stability of the unmodified algorithms is established by requiring the reference signal to be persistently exciting.

关键词： adaptive control linear systems stability stochastic systems external disturbances global stability linear system persistently exciting reference signal robustness unmodeled dynamics unmodified stochastic adaptive control algorithms external disturbance unmodeled dynamics adaptive control algorithms Linear system stochastic systems overall buckling Robustness computer algorithms

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A RECURSIVE CONCENTRATOR STRUCTURE WITH APPLICATIONS TO SELF-ROUTING SWITCHING-NETWORKS

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IEEE TRANSACTIONS ON COMMUNICATIONS 1994年第2-4期42卷 896-898页

作者： NARASIMHA, MJ STAR Laboratory Department of Electrical Engineering University of Stanford Stanford CA USA

A technique for constructing an N-input concentrator from two (N/2)-input concentrators and a stage of 2x2 switching elements is described. Recursive decomposition of each of the (N/2)-input concentrators yields a log2N-stage switching network similar in topology to the inverse omega network. The control algorithm for setting the switching elements is shown to be a simple logic function of the activity bits of the inputs. An iterative cell that combines the functions of the control logic and the 2x2 switching element can be used as a building block to realize the entire concentrator. Applications of the concentrator structure as an interconnection fabric in fast packet switching is explored. This leads to an efficient self-routing network, similar in topology to the transposed Batcher-banyan network.

关键词： topology Switching networks concentrators(telecommunications) control logic multistage interconnection networks Switch elements Recursive Network computer algorithms

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STRICTLY NONBLOCKING 512X512 OPTICAL-FIBER MATRIX SWITCH BASED ON 3-STAGE CLOS NETWORK

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IEEE PHOTONICS TECHNOLOGY LETTERS 1994年第6期6卷 764-766页

作者： TACHIKURA, M KATAGIRI, T KOBAYASHI, H NTT Telecommunication Field Systems Research and Development Center Tokaimura Ibaraki Japan

This letter describes a novel structure for large-matrix connector-type optical switches. The dimensions of the apparatus designed for 512 x 512 switching were 0.8 m(W) x 0.6 m(D) x 1.85 m(H). It is based on the three-stage Clos network. Switching is accomplished by the mechanical reconnection of fibers. The fiber tangling is avoided by using an intelligent zigzag transfer method for the connector plugs. The mean insertion loss is less than 1 dB for SM fibers. The most appropriate internal fiber link is chosen by a computer algorithm from all possible candidates. The mean switching time is estimated at about 1 min.

关键词： Strictly Fiber Optical Fibers multistage interconnection networks computer algorithms tangling Connector Device Component fiber optic link Switches

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OPTIMAL FLOW-CONTROL OF AN M/M/1 QUEUE WITH A BALANCED BUDGET

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IEEE TRANSACTIONS ON AUTOMATIC CONTROL 1994年第9期39卷 1918-1921页

作者： CHAKRAVORTI, B BELLCORE INFORMAT SCI & TECHNOL LABECON RES GRPMORRISTOWNNJ

The following problem is considered. There are several users who send jobs to an M/M/1 queue and have privately observed information relating to their benefits from the rate of job submissions and their costs due to waiting in the queue. Each user's benefits and costs are unknown to the queue manager and to other users. The manager's objective is to achieve ''optimal'' flow control, where the optimality depends on arriving at an appropriate trade-off between delay and the job arrival rate assigned to each user: the allocations should be such that no user can be made better off by a reallocation without hurting at least one other user. Since the optimality calculation requires knowledge of the users' private information, we propose an algorithm that converges to the optimum, while inducing users to reveal information relating to their benefits and costs truthfully, and balances the manager's budget. Earlier work on this problem [1] has produced a flow control algorithm that requires the queue manager to incur a potentially huge deficit;this leads to several theoretical and practical problems.

关键词： flow control manager jobs PLXNB2 gene Queue Budgets Cost Benefit optimality computer algorithms

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SOLVING RECURRENCE RELATIONS INVOLVING FLOOR AND CEILING FUNCTIONS

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ELECTRONICS LETTERS 1994年第17期30卷 1391-1393页

作者： THOMPSON, BC Dept. of Comput. Sci. Univ. Coll. of Swansea

A rounding lemma is presented which has applications in the field of discrete mathematics. The lemma can be used to simplify complex terms and analyse certain recurrence relations.

关键词： ALGORITHM THEORY computer algorithms

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ACCOMMODATION OF TIME-DELAY VARIATIONS IN AUTOMATIC INFUSION OF SODIUM-NITROPRUSSIDE

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IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING 1994年第11期41卷 1083-1091页

作者： DELAPASSE, JS BEHBEHANI, K TSUI, KC KLEIN, KW UNIV TEXAS DEPT BIOMED ENGNARLINGTONTX 76019 LEE MED SYST INC KERMERSVILLENC 27284 UNIV TEXAS SW MED CTRDEPT ANESTHESIOLDALLASTX 75235

A new self-tuning regulator for control of mean arterial blood pressure using sodium nitroprusside is presented. In addition to adapting to various patient response gains and time constants, the controller can accommodate variations in pure time delays, a problem that has not been addressed fully in previously proposed controllers. The control algorithm derivation is based on incorporating a self-tuning controller with an adaptive discrete time delay compensator. The derivation, however, is general and can potentially be applied to other pharmacological agents in addition to sodium nitroprusside. The a priori information required for implementation of the controller is the estimate of the order of the patient response transfer function and the range of the pure time delay. An attractive feature of the controller is its capability to optimize the level of the infused drug during the transient phase of the control without creating an output offset. This feature tends to reduce the overall level of the infused drug. Hence, it may be useful when the cost of a drug or its long-term administration side effects is of concern, such as in the case of sodium nitroprusside.

关键词： biocontrol biomedical equipment controllers haemodynamics patient treatment pressure control a priori information automatic infusion blood pressure control control algorithm infused drug output offset patient response gains patient response transfer func Sodium Nitroprusside Medical device Controllers Nitroprusside patient treatment Pressure control computer algorithms Hemodynamics

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GRAPHICAL FISHEYE VIEWS

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COMMUNICATIONS OF THE ACM 1994年第12期37卷 73-84页

作者： SARKAR, M BROWN, MH DIGITAL EQUIPMENT CORP SYST RES CTRPALO ALTOCA 94301

This article explores a fisheye lens approach to viewing and browsing graphs. A fisheye view of a graph shows an area of interest quite large and with detail and shows other areas successively smaller and in less detail. A fisheye lens seems to have all advantages of the other approaches for viewing and browsing a graph without any of drawbacks. Graphs with hundreds of vertices and edges are common in many application areas of computer science, such as network topology, and graph theory. There are literally hundreds of algorithms for positioning nodes to produce an aesthetic and informative display. Displaying all the information associated with the vertices and edges shows the global structure of the graph but has the drawback that details are typically too small to be seen. Alternatively, zooming into a part of the graph and panning to other parts does show local details but loses the overall structure of the graph. Using two or more views, one of the entire graph and the other of a zoomed portion, gives one the advantage of seeing both local detail and overall structure but has drawbacks of requiring extra screen space and forcing the viewer to mentally integrate the views.

关键词： computer algorithms Graphic methods Charts, diagrams, etc. computer science computer networks computer graphics Topology

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CRYPTANALYSIS AND PROTOCOL FAILURES

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COMMUNICATIONS OF THE ACM 1994年第11期37卷 56-65页

作者： SIMMONS, GJ P.O. Box 365 Sandia Park NM

This article presents examples of protocol failures in cryptographic operations. In many protocols, the security of the cryptographic portion is progressively weakened as a result of the protocol being exercised, for example, by reducing the size of the key space that one would have to search to identify an active cryptographic key but these are not considered examples of true protocol failures, even though they are clearly examples of potential sources of failure in the intended security function of a protocol. Finding and fixing failures of the latter type is the function of conventional analysis of cryptoalgorithms. An algorithm or protocol can be unconditionally secure, computationally secure, provably secure, or, of course, insecure. A scheme is said to be unconditionally secure if the probability of breaking it is independent of the computing resources and time an opponent is able or willing to spend. A scheme is said to be computationally secure if breaking it requires an attacker to carry out some computation that is possible in principle but for which all known methods of execution require an infeasible amount of computation.

关键词： CRYPTOGRAPHY computer network protocols computer security computer algorithms CRYPTOGRAMS COMPUTATIONAL complexity computer science

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