MINES ParisTech CAS - Centre automatique et systèmes


30 octobre 2007, Salle L 106, à l'Ecole des Mines, Paris
10h00 : Prof. Michael ZEITZ, Institut für Systemdynamik, Universität Stuttgart, Allemagne.
The concept of affine flat inputs to an uncontrolled system with a given output is introduced. This approach can be seen as dual to the search of a flat output of a control system with a given input. In the SISO case, the construction of the vector field associated to the flat input is based on the equations defining an output of relative degree n. For nonlinear multi-output systems, the problem of finding flat inputs is more challenging than the SISO case. This is related to the fact that general conditions for the construction of flat outputs of nonlinear MIMO systems are difficult to apply. The vector field associated to a flat input has been found by Steffen Waldherr through a new view of a fictitious vector field which has been used in the nonlinear normal form observer design for a long time.
The determination of flat inputs is of practical relevance if the actuators or their positions in a plant are not yet fixed. The actuation via a flat input enables the use of flatness-based analysis and design techniques. However, some constraints on the implementation of flat input vector fields have to be considered if there is no complete freedom for input injection in the system. In the seminar talk, the state of the art concerning existence, determination, and application of flat inputs is addressed in order to carry on a discussion with experts on flat outputs.