Volume 59, Issue 6 -

This paper gives both an overview of the concepts of structrual and strong structural controllability of structured linear systems and some new results to strong structural controllability. A system is called strongly structurally controllable if the controllability conditions are fulfilled for any nonzero system parameters.

Modeling and identification of dynamic systems are crucial in the fields of control engineering. This paper presents an approach for optimization of dynamic system models with variable structure using multi-objective evolutionary algorithms. The algorithm uses specific operators to simultaneously evolve the structure of a model and optimize its parameters. Based on input and output data of the real system the method aims at finding a set of optimal models that constitute a compromise between model quality and complexity. The method is exemplary applied to the identification of an artificial test system as well as of a hydraulic proportional valve and an elastic robot arm.

An Internal Model Control structure for nonlinear, stable single-input single-output systems with actuator saturation is proposed. The main topic is the analysis of the stability and the steady-state input-output behaviour of the IMC filter which is an integral part of the IMC structure. Despite of the actuator magnitude limitation and the plant nonlinearities, the closed IMC loop is shown to be internally stable and to possess the set-point tracking property. The performance of the approach is demonstrated by its application to the intake manifold pressure control of a combustion engine. Zusammenfassung Der Beitrag beschreibt die Eigenschaften einer IMC-Regelung für nichtlineare stabile Eingrößensysteme mit Stellgrößenbegrenzung. Der Schwerpunkt liegt bei der Analyse der Stabilität und des stationären Eingangs-Ausgangsverhaltens des IMC-Filters, das Bestandteil der IMC-Regelung ist. Es wird bewiesen, dass der IMC-Regelkreis trotz der Stellgrößenbegrenzung und der nichtlinearen Streckeneigenschaften stabil ist und die Eigenschaft der Sollwertfolge besitzt. Die Leistungsfähigkeit des Ansatzes wird anhand der Regelung des Saugrohrdrucks vor einem Verbrennungsmotor demonstriert.

This paper presents an output feedback design approach for systems with non-polynomial nonlinearities using SOS-Programming. To this end a polynomial approximation of the system is determinded and the corresponding approximation error is computed. This error is used within the SOS-programm to determine a stabilizing output feedback and a Lyapunov funktion, which yield an as large as possible region of attraction of the equilibrium of the closed-loop original system. In order to influence the dynamics of the resulting closed-loop system, the linear part of the control law is assigned, which is used to assign desired eigenvalues to the linearization of the closed-loop system. If a dynamic output feedback is required for stabilization, the design method can be rewritten as a static output feedback desgin by adding the dynamic of the controller to the system description. A simple example illustrates the presented design approach.

This paper presents an exact input-output linearization for the translational dynamics of a quadrotor helicopter. For this purpose the required attitude information is fully given by the orientation of the thrust vector (coinciding with the body-fixed z -axis), which can be described with only two degrees of freedom. To this end a special quaternion for the thrust axis is introduced in this paper. The input-output linearization then consists of two stages. First an input-output linearization relating z position to thrust is performed and followed by a second input-output linearization relating xy position to the control torques.

Continuous Annular Electro-Chromatography (CAEC) is a novel high performance continuous separation process for high value substances. A prototype is currently being developed in an EU-funded project 1 . In this paper, we describe an iterative online optimization scheme for this process based upon a rigorous 2D model of the apparatus and the gradient modification technique that has been previously applied to the online optimization of batch chromatography by Gao and Engell [7].