Per Søgaard-Andersen

Technical University of Denmark

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Henrik Niemann

Technical University of Denmark

Jakob Stoustrup

Aalborg University

Erik Trostmann

Fraunhofer Institute for Factory Operation and Automation

Finn Conrad

National Centre for Product Design and Development Research

Paul Haase Sørensen

Parabon Computation (United States)

HANS HENRIK NTEMANN

Technical University of Denmark

Cooperative Institutions

Technical University of Denmark

Ørsted (Denmark)

Aalborg University

Fraunhofer Institute for Factory Operation and Automation

Walter de Gruyter (Germany)

Japan Science and Technology Agency

Naver (South Korea)

FZI Research Center for Information Technology

Parabon Computation (United States)

Creare (United States)

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Eigenstructure/LTR Feedback Design For Non-Minimum Phase Plants

American Control Conference (1990)

Per Søgaard-Andersen Henrik Niemann

In this paper we derive ney results on feedback design for non-minimum phase systems based on an eigenstructure interpretation of the LTR-concept. To facilitate this a modification of the recovery principle is formulated.

Minimum phase

10.23919/acc.1990.4790869

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Loop transfer recovery with minimal-order observers

Per Søgaard-Andersen

A solution to the problem of loop transfer recovery with minimal order observers is obtained for the control loop broken at the plant input. Three distinct cases are treated - depending on the properties of the first Markov parameter of the plant model. For two of these cases a LQG-type design method is outlined. If the first Markov parameter is of full rank exact loop transfer recovery can be achieved.

Rank (graph theory)

10.1109/cdc.1987.272530

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Citations (9)

H-infinity Optimization of the Recovery Matrix

Henrik Niemann Per Søgaard-Andersen Jakob Stoustrup

Infinity

Matrix (chemical analysis)

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Robustness analysis of sampled-data feedback systems

Control, 1988. CONTROL 88., International Conference on (1988)

Per Søgaard-Andersen Henrik Niemann

Presents a procedure for analyzing the robustness properties of closed-loop systems with sampled-data controllers. Beyond the outline of the theoretical results for discrete-time mu -analysis the major result of the paper is the investigation of the choice of weights for the sectors of the samplers. It is shown in the examples how the weights can be chosen so that the impact of the approximation errors are reduced significantly. Hence conic sectors for robustness evaluations need not be conservative. The results of the paper presents a first step towards systematic procedures for the selection of sampling-rate and of discretization methods for discrete-time implementation of continuous-time controllers in the face of structured uncertainties. >

Robustness

Conic section

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Eigenstructure Conditions for Loop Transfer Recovery

American Control Conference (1988)

Per Søgaard-Andersen

Conditions for loop transfer recovery based on eigenstructure assignment are derived. These conditions imply constraints on the eigenvalues and certain parameter vectors of the controller. Three cases emerge - depending on the geometric stucture of the plant. For all cases explicit design rules are derived. The eigenstructure-LTR approach provides - beyond insight into mechanisms of LTR - improved flexibility in selecting the controller gains and faster recovery convergence as compared with the LQG-based LTR method. These issues are illustrated in an example.

10.23919/acc.1988.4789913

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Eigenstructure and residuals in multivariable state-feedback design

International Journal of Control (1986)

Per Søgaard-Andersen Erik Trostmann Finn Conrad

Abstract In this paper it is shown that all residuals assignable by state feedback must belong to certain well-defined subspaces defined by the freely selectable closed-loop eigenvalues. These subspaces are straightforward to compute, and the computational requirements are modest. The applicability of this result is facilitated by the fact that fundamental control design objectives like I/O response and robustness can be expressed in terms of residuals. A design procedure is outlined and illustrated by an example. The method is applicable to square and non-square systems.

Robustness

10.1080/00207178608933610

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Citations (6)

Loop transfer recovery for general observer architectures

International Journal of Control (1991)

HANS HENRIK NTEMANN Per Søgaard-Andersen Jakob Stoustrup

A general and concise formulation is given of the loop transfer recovery (LTR) design problem based on recovery errors. Three types of recovery errors are treated, open loop recovery, sensitivity recovery and input-output recovery errors. The three corresponding versions of the asymptotic recovery problem turn out to be equivalent, since the minimization of the recovery errors all amount to the minimization of a certain matrix, the recovery matrix. Using the recovery error definitions, simple necessary and sufficient conditions for the controllers are derived both for the exact and asymptotic recovery cases. This general recovery formulation covers all known observer based compensator types as special cases. The conditions given in this setting are effectively the aim of all known LTR design methods. The recovery formulation is interpreted in terms of a model-matching problem as well, which is examined by means of the Q-parametrization. It is shown how the general controller obtained by the Q-parametrization can be written as a Luenberger observer based controller. In all cases, n controller states suffice to achieve recovery. The compensators are characterized for errors both on the input- and on the output-node (dual case).

Observer (physics)

Minification

Parametrization (atmospheric modeling)

10.1080/00207179108953669

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Citations (45)

General Conditions for Loop Transfer Recovery

American Control Conference (1991)

Henrik Niemann Jakob Stoustrup Per Søgaard-Andersen

This paper gives a general and concise formulation of the Loop Transfer Recovery (LTR) design problem. Necessary and sufficient conditions are given for obtaining LTR for non-strictly proper systems when general observer-based controllers or general output feedback controllers are applied. The connection between these two controller types is also described in the light of LTR.

Feedback loop

Observer (physics)

10.23919/acc.1991.4791382

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Robust stability assessment of a 2-DOF manipulator based on mu -analysis

Control, 1988. CONTROL 88., International Conference on (1988)

Per Søgaard-Andersen Paul Haase Sørensen

From a feedback control perspective two of the major concerns in manipulator-design are the dynamical couplings between the individual links, and the parameter-variations of the coefficients in the model as the manipulator is following a trajectory in the workspace. The first concern is basically related to the multivariable nature of the manipulator, and the second concern gives rise to robustness considerations-i.e. is the system stable along a class of trajectories? The latter concern is made more complicated by the existence of cross-coupling uncertainties. In the paper an approach to the analysis of such multivariable robustness issues is presented. The approach is based on structured singular value analysis ( mu -analysis). This technique has been shown to be very powerful in analyzing the robustness of a number of industrial processes. However, no studies of mu -analysis of manipulator robustness have been presented. The paper addresses the modelling of the 2-DOF manipulator. Essentially this is a model of the upper and fore arm of an industrial robot (the Hitachi PW10).

Robustness

Work space

Robot manipulator

Manipulator (device)

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Citations (1)

New Results in Discrete-Time Loop Transfer Recovery

American Control Conference (1988)

Henrik Niemann Per Søgaard-Andersen

For discrete-time compensators incorporating prediction observers asymptotic loop transfer recovery is not feasible. Instead loop transfer recovery objectives must be satisfied via exact recovery techniques. In this note the model-based compensators which achieves exact recovery are parametrized in terms of the system zeros and the corresponding zero-directions. Full-order as well as minimal-order observers are treated. Further it is shown how exact recovery is also applicable to non-minimum phase plants. In this case the achievable performance is parameterized explicitly.

Pole–zero plot

10.23919/acc.1988.4790142

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Citations (12)