15 Fakultätsübergreifend / Sonstige Einrichtung

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16

Browse

Filter results by typing the first few letters
Now showing 1 - 5 of 5
  • Thumbnail Image
    ItemOpen Access
    Design of robustly performing controllers for a class of practical control problems
    (1993) Amann, Notker; Allgöwer, Frank
    The design of robustly performing controllers for a class of practical control problems is considered, involving both parametric and unstructured uncertainty. The problem is dealt with in the structured singular value (μ)-framework. An iterative approach comprising both μ-analysis of the detailed problem and D-K-iteration for a modified problem is proposed, as no direct solution to the detailed μ-synthesis problem is known to date. With a practical MIMO process control example it is shown that this approach leads to controllers that exhibit robust performance.
  • Thumbnail Image
    ItemOpen Access
    H∞-control of differential-algebraic-equation systems
    (1998) Rehm, Ansgar; Allgöwer, Frank
    In this paper H∞ control of high index and non-regular linear differential-algebraic-equation systems is addressed. Based on a generalization of the bounded real lemma (BRL) to index one systems, all linear output feedback controllers in standard, ie non-descriptor, state space form solving the H∞ control problem can be characterized via biaffine matrix inequalities (BMIs). In a second step a congruence transformation and a subsequent change of variables show that certain linear matrix inequalities (LMIs) necessarily must hold in order to admit a solution of the H∞ control problem. However, these conditions are not sufficient. Necessary and sufficient conditions for the existence of a controller solving the H∞ control problem are derived as BMIs of reduced order compared to the original characterization via the BRL. The approach is illustrated by a simple example.
  • Thumbnail Image
    ItemOpen Access
    On nonlinear systems with poorly behaved zero dynamics
    (1992) Doyle, Frank J.; Allgöwer, Frank; Oliveira, Simone Loureiro de; Gilles, Ernst Dieter; Morari, Manfred
    The present work adresses the problem of synthesizing nonlinear state feedback controllers for nonlinear, nonminimum-phase processes in three different ways. The first approach consists of a partial linearization which preserves stability by using an approximate stable/anti-stable factorization. The second technique can be viewed as an inner-outer factorization based approach. And, finally, in the single-output case, it is shown (through an example) that stabilization of the internal dynamics of a nonminimum-phase system can be achieved by using an additional input if this is feasible in practice. In this case, the manipulated variables have different roles, i.e., one is chosen such as to input/output feedback linearize the system and the second is used to locally stabilize the resulting nonminimum-phase internal dynamics.
  • Thumbnail Image
    ItemOpen Access
    Robust control of a catalytic fixed bed reactor
    (1994) Kremling, Andreas; Allgöwer, Frank
    Catalytic fixed bed reactors exhibit interesting control problems due to their nonlinear behaviour and their sensitivity to load changes and other disturbances. Because detailed nonlinear models of such reactors are too complex for use in controller design, a linear model description is identified here along with an appropriate structured uncertainty description. The controller is designed based on the μ-paradigm to guarantee robust stability and robust performance. A comparison with an H∞-optimal controller is also given. For the H∞-design the structured uncertainties are converted into a single multivariable unstructured uncertainty. As expected the H∞-controller can only achieve a much less demanding performance because of the conservatism of the unstructured uncertainty description. Experimental results involving a real reactor are given.
  • Thumbnail Image
    ItemOpen Access
    Validation and analysis of linear distillation models for controller design
    (1993) Amrhein, Michael; Allgöwer, Frank; Marquardt, Wolfgang
    It is a nontrivial task to decide whether a model describes the main dynamic characteristics of a process and to determine which model is to be preferred for controller design. Techniques for examining lineal models for controller design are described in Section 2. One focus of this paper is on tools for analysing multivariable processes in the frequency domain, for example, condition number and dynamic relative gain array (RGA) analysis. The latter tool is extended by the phase information of the RGA. A novel evaluation tool involving the singular directions over frequency of the respective processes is introduced. In Section 3, a new linear low-order model is compared to five models from the literature using the analysis tools introduced in Section 2. The new model directly exploits wave propagation phenomena, and, therefore, will be called the wave model. Finally, Section 4 shows briefly result of the H∞-coutrolled column where the controller is designed on the basis of the wave model. Simulations with a detailed nonlinear distillation model show that very good control action can be achieved with this model. Moreover, the linear model allows to predict the nonlinear closed loop behavior quite accurately.