70,076 research outputs found
Enhanced LFR-toolbox for MATLAB and LFT-based gain scheduling
We describe recent developments and enhancements of the LFR-Toolbox for MATLAB for building LFT-based uncertainty models and for LFT-based gain scheduling. A major development is the new LFT-object definition supporting a large class of uncertainty descriptions: continuous- and discrete-time uncertain models, regular and singular parametric expressions, more general uncertainty blocks (nonlinear, time-varying, etc.). By associating names to uncertainty blocks the reusability of generated LFT-models and the user friendliness of manipulation of LFR-descriptions have been highly increased. Significant enhancements of the computational efficiency and of numerical accuracy have been achieved by employing efficient and numerically robust Fortran implementations of order reduction tools via mex-function interfaces. The new enhancements in conjunction with improved symbolical preprocessing lead generally to a faster generation of LFT-models with significantly lower orders. Scheduled gains can be viewed as LFT-objects. Two techniques for designing such gains are presented. Analysis tools are also considered
The Secant Conjecture in the real Schubert calculus
We formulate the Secant Conjecture, which is a generalization of the Shapiro
Conjecture for Grassmannians. It asserts that an intersection of Schubert
varieties in a Grassmannian is transverse with all points real, if the flags
defining the Schubert varieties are secant along disjoint intervals of a
rational normal curve. We present theoretical evidence for it as well as
computational evidence obtained in over one terahertz-year of computing, and we
discuss some phenomena we observed in our data.Comment: 19 page
- …