B1: Global Optimization of Structures and Control Systems

The objective of project B1 is the development of concepts for the modelling, the analysis and the optimization of adaptive structures.  Since elements of these structures fulfill several functions simultaneously, e.g., adaptive and structural functions, a separate optimization of structures and control systems may lead to sub-optimal results.  The concepts of global optimization, therefore, consider parameters of the active and passive parts of the system simultaneously for optimization.

In order to improve the evaluation of criteria- and sensitivity functions and the handling of extensive optimization problems special attention is given to mathematical and numerical methods used in the optimization algorithms.  In particular, point- and piecewise defined optimization criteria prove to be of great advantage for the evaluation of dynamical behaviours.  Since the sensitivities of such criteria may be discontinuous and cannot be computed by standard methods, Automatic Differentiation techniques are used.

The approach is applied to a tethered satellite system (TSS) with the objective of damping structural vibrations in the tether.  The TSS is therefore modelled as a multibody system with a chain of point-masses connected by massless springs and dampers representing the massive, flexible tether. This model complements the model of project B3 which considers a deployable, massless, inextensible tether. By controlling the tether winch using optimized control parameters, the damping of the longitudinal tether vibrations can be improved significantly.

Further investigations on the parameterization of adaptive structures and the application of the approach of global optimization will be conducted in cooperation with project B2  considering a lightweight truss structure and with project A5 dealing with a flexible helicopter rotor blade.

Prof. Dr.-Ing. Werner Schiehlen
Dr.-Ing. Peter Eberhard
Dipl.-Ing. Florian Dignath
Institute of Engineering and Computational Mechanics
University of Stuttgart
Pfaffenwaldring 27
70550 Stuttgart
email: [wos,pe,fd]@itm.uni-stuttgart.de

http://www.isd.uni-stuttgart.de/sfb409/                         sfb409@isd.uni-stuttgart.de