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European Control Conference (ECC)

作者： A. Varga DLR Oberpfaffenhofen German Aerospace Research Establishment Institute of Robotics and System Dynamics D-82234 Wessling Germany

The discrete-time positive periodic Lyapunov equations have important applications in the balancing and potentially also in the model reduction of discrete-time periodic systems. Efficient numerically reliable algorithms based on periodic Schur decomposition are proposed for the solution of these equations. The proposed algorithms are extensions of the method of Hammarling for the case of positive semidefinite solution. Special methods were developed to solve efficiently small order periodic Lyapunov and Sylvester equations.

关键词： Mathematical model Standards Iterative methods Matrix decomposition Eigenvalues and eigenfunctions Accuracy

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Robust controller for multiplicative uncertainty: the time-varying discrete case

Robust controller for multiplicative uncertainty: the time-v...

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American Control Conference (ACC)

作者： V. Ionescu C. Oara Faculty of Automatic Control and Computers University Politehnica of Bucharest Bucharest Romania Institute for Robotics and System Dynamics DLR-Oberpfaffenhofen Wessling Germany

The robust stabilization problem for time-varying discrete linear systems subject to multiplicative uncertainties is considered. An evaluation of the stability margin and explicit formulae for the robust controller ar... 详细信息

关键词： Robust control Uncertainty Computer aided software engineering Automatic control Time varying systems Linear systems Robust stability Riccati equations Robustness Linear matrix inequalities

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Fast planning of precision grasps for three-dimensional objects

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Advanced robotics 1997年第5期12卷 535-549页

作者： Fischer, Max Hirzinger, Gerd German Aerospace Center (DLR) Institute of Robotics and System Dynamics Wessling 82230 PO Box 1116 Germany

—In the near future, more and more robots will be used for servicing tasks, tasks in hazardous environments or space applications. Dextrous hands are a powerful and flexible tool to interact with these real world environments that are not specially tailored for robots. In orderto grasp and manipulate real world objects, grasp planning systems are required. Grasp planning for general three-dimensional (3-D) objects is quite a complex problem requiring a large amount of computing time. Fast algorithms are required to integrate grasp planners in online planning systemsfor robots. This paper presents a heuristic approach towards fast planning of precision grasps for realistic, arbitrarily shaped 3-D objects. In this approach a number of feasible grasp candidates are generated heuristically. These grasp candidates are qualified using an efficiently computablegrasp quality measure and the best candidate is chosen. It is shown that only a relatively small number of grasp candidates has to be generated in order to obtain a good — although not optimal — grasp. In Sections I and 2 an introduction to the problem field is given and the DLRHand is presented. Section 3 describes the grasp quality measure used. In Sections 4 and 5 the planning strategy is presented, i.e. how to generate and test grasp candidates. The paper closes with some results (Section 6) and an outlook (Section 7). © VSP and robotics Society of Japan 1997.

关键词： Grasp planning Online planner Planning heuristics Precision grasp

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An extension of Redheffer's theorem for time-varying systems

An extension of Redheffer's theorem for time-varying systems

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American Control Conference (ACC)

作者： V. Ionescu C. Oara Faculty of Automatic Control and Computers University Politehnica of Bucharest Bucharest Romania DLR-O berpfaffenhofen Institute for Robotics and System Dynamics Wessling Germany

It is well known that the Redheffer theorem is a key tool in the technical machinery of the H/sub /spl infin// theory. The time-varying version of this theorem has been considered first in Ravi et al. (1991). In the present paper we generalise Redheffer's theorem for time-varying systems by considering relaxed assumptions. More precisely, the exponential stability assumption is relaxed to that of exponential dichotomy while the stability and detectability conditions imposed on the closed loop system are removed.

关键词： Time varying systems Stability Automatic control Machinery Closed loop systems Hilbert space Orbital robotics Equations

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Indefinite sign Riccati theory for descriptor systems

Indefinite sign Riccati theory for descriptor systems

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European Control Conference (ECC)

作者： V. Ionescu C. Oară Faculty of Automatic Control and Computers University Polytechnica Bucharest Bucharest Romania DLR-Oherpfaffenhofen Institute for Robotics and System Dynamics D-82239 Wessling Germany

We present a general Riccati theory for systems in descriptor form considered under the weakest possible assumptions imposed on the coefficent matrices. A Riccati-like equation of descriptor form is introduced and its stabilizing solution is characterized in terms of the associated extended Hamiltonian pencil (EHP) whilst the computation of such a solution is reduced to solving a generalized eigenvalue problem for a singular EHP. The results exposed in the paper are generalizations to the game-theoretic (sign indefinite) and singular cases of the (positivity) Riccati theory developed by several authors in the framework of descriptor systems. Possible applications range from various nonstandard and J-spectral factorizations to H 2 and H ∞ control of descriptor systems.

关键词： Riccati equations Eigenvalues and eigenfunctions Xenon Postal services Games Standards Manganese

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Torque maximization for permanent magnet synchronous motors

Torque maximization for permanent magnet synchronous motors

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European Control Conference (ECC)

作者： A. Verl M. Bodson Institute for Robotics and System Dynamics German Aerospace Research Establishment (DLR) D-82234 Wessling Germany University of Utah Salt Lake City UT US

The paper discusses the problem of maximizing the torque of permanent magnet synchronous motors in the presence of voltage and current constraints. Formulas are given that are suitable to operation with voltage and current source inverters and to real-time computation. Generally, the available torque is limited by current constraints at low speeds and by voltage constraints at high speeds, but there is also often an intermediate range of speeds where both the voltage and the current constraints are active. The paper specifies how optimal operation can be achieved in all three ranges, and at what speeds the optimal operation transitions from one mode to another. A numerical example for a typical permanent magnet stepper motor is discussed to illustrate the contributions of the paper.

关键词： Torque Permanent magnet motors Synchronous motors Mathematical model Induction motors DC motors Lead

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Development of Semi-Active Truck Suspension

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IFAC Proceedings Volumes 1997年第8期30卷 467-472页

作者： M. Valasek M. Babic Z. Sika L. Magdolen Department of Mechanics Faculty of Mechanical Engineering Czech Technical University in Prague CZ Institute for Robotics and System Dynamics German Aerospace Research Establishment DLR Wessling FRG Department of Technical Mechanics Faculty of Mechanical Engineering Slovak Technical University Bradslava SK

Within the EC project Copernicus SADTS (Semi-Active Damping of Truck’s Suspension and Its Influence on Driver and Road Loads) the semi-active suspension for Liaz truck prototype is being developed. The objective is to decrease the dynamic road-tyre forces in order to reduce the road damage. It was necessary to develop a suitable truck prototype, its simulation model, different control concepts and to implement the semi-active suspension. The paper describes the development stages and the so far achieved results. The full mathematical model was the basis for simplified models for control designs and served as a reference model for comparison of different control concepts. The spatial three dimensional simulation model has been developed and verified. The base model includes also the reference inputs of excitation and the different criteria for performance evaluation. The purpose of the model was to investigate the vertical dynamics though with the influence of antisymmetry of uneveness and lateral motion. A number of different control concepts have been considered. Possible suitable control concepts have been selected from existing classical as well as advanced control design methods. Also several within this project newly developed approaches have been added. There have been considered the control concepts of simple approaches (sky hook), classical approaches (LQR), multi-objective multi-parameter optimization (ΜΟΡΟ), fuzzy and neural networks, robust control design. The newly developed control concepts are ground-hook and combination sky/ground-hook, robust multi-objective optimization based on Taguchi approach, fuzzy control based on optimization, structural approach (separate control of frame and cabine suspension). The performance criteria for evaluation have been road forces, driver’s seat and load accelerations, robustness against change of parameters. The comparison has been done on the simulation model in SIMPACK program package connected with MAT-LAB/SIMULI

关键词： semi-active damping road-tyre force truck road friendliness

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Learning shape from shading by a multilayer network

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IEEE TRANSACTIONS ON NEURAL NETWORKS 1996年第4期7卷 985-995页

作者： Wei, GQ Hirzinger, G Institute of Robotics and System Dynamics German Aerospace Research Establishment Oberpfaffenhofen Germany

The multilayer feedforward network has been usually used for learning a nonlinear mapping based on a set of examples of the input-output data, In this paper, we present a novel use of the network, in which the example data are not explicitly given, We consider the problem of shape from shading in computer vision, where the input (image coordinates) and the output (surface depth) satisfy only a known differential equation, We use the feedforward network as a parametric representation of the object surface and reformulate the shape from shading problem as the minimization of an error function over the network weights, The stochastic gradient and conjugate gradient methods are used for the minimization, Boundary conditions for either surface depth or surface normals (or both) can be imposed by adjusting the same network at different levels, It is further shown that the light source direction can be estimated, based on an initial guess, by integrating the source estimation with the surface estimation, Extensions of the method to a wider class of problems are discussed, The efficiency of the method is verified by examples of both synthetic and real images.

关键词： Shape Nonhomogeneous media Computer vision Differential equations Computer errors Stochastic processes Gradient methods Minimization methods Boundary conditions Light sources

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A multishift Hessenberg method for pole assignment of single-input systems

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IEEE TRANSACTIONS ON AUTOMATIC CONTROL 1996年第12期41卷 1795-1799页

作者： Varga, A DLR-Oberpfaffenhofen Institute for Robotics and System Dynamics German Aerospace Research Establishment (DLR) Wessling Germany

A new algorithm is proposed for the pole assignment of single-input linear time-invariant systems, The proposed algorithm belongs to the family of Hessenberg methods and is based on an implicit multishift QR-like technique, The new method compares favorably in many respects (speed, memory usage) with existing numerically stable methods, Its improved vectorizability guarantees good opportunities for parallel implementation on high-performance computers.

关键词： Eigenvalues and eigenfunctions Symmetric matrices Aerodynamics Concurrent computing State feedback Control systems Controllability Robot kinematics Costs

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Investigating the Synthesis of RBF Networks

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Journal of systems Engineering and Electronics 1996年第3期7卷 25-29页

作者： V. David Sanchez A.(German Aerospace Research Establishment, DLR Oberpfaffenhofeninstitute for Robottes and system dynamicsD-82230 Wessling, Germany) German Aerospace Research Establishment DLR Oberpfaffenhofen Institute for Robotics and System Dynamics D-82230 Wessling Germany

The approximation capability of RBF networks is investigated using a test function and a fixed finite number of training data. The test function used allows to confirm the recently introducedconcept of second derivative dependent placement of RBF centers. Different Gaussian RBF networksare trained varying the width and the number of centers (number of hidden units). The dependenceof the approximation error on these network parameters is studied experimentally.

关键词： Approximation error Function approximation Neural network synthesis Number of hidden units Radial basis functions.

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