Duality-based robust polynomial matrix controller

Summary Complex dynamic processes partly contain unknown parameters (in the controller) and known parameters (in the process). The latter are frequently deteriorated by uncertainties. The inverse problem results from the challenge to find the unknown system parameters such that the over-all input output behaviour turns out close to some given performance. As the index of performance the stability margin is selected. In this paper, a computer-assisted gradient approach is presented which improves the stability margin of a multivariable control system in the presence of spherical uncertainties. Following the appropriate gradient and observing a heuristic stopping condition from the viewpoint of design engineering, the method provides a unified approach both for controller design and robustification.      

Temporal Upsampling of Point Cloud Sequences by Optimal Transport for Plant Growth Visualization

Plant growth visualization from a series of 3D scanner measurements is a challenging task. Time intervals between successive measurements are typically too large to allow a smooth animation of the growth process. Therefore, obtaining a smooth animation of the plant growth process requires a temporal upsampling of the point cloud sequence in order to obtain approximations of the intermediate states between successive measurements. Additionally, there are suddenly arising structural changes due to the occurrence of new plant parts such as new branches or leaves. We present a novel method that addresses these challenges via semantic segmentation and the generation of a segment hierarchy per scan, the matching of the hierarchical representations of successive scans and the segment-wise computation of optimal transport. The transport problems' solutions yield the information required for a realistic temporal upsampling, which is generated in real time. Thereby, our method does not require shape templates, good correspondences or huge databases of examples. Newly grown and decayed parts of the plant are detected as unmatched segments and are handled by identifying corresponding bifurcation points and introducing virtual segments in the previous, respectively successive time step. Our method allows the generation of realistic upsampled growth animations with moderate computational effort.     

Buchbesprechungen

Ohne Zusammenfassung     

Polarization-independent and ultra-high bandwidth electroabsorption modulator in multiquantum-well deep-ridge waveguide technology

Electroabsorption modulators with polarization-independence of transmission (TE/TM sensitivity <0.4 dB at 1550 nm) over a wide wavelength range from 1540-1560 nm have been realized using tensile-strained InGaAs and InGaAsP quantum wells. Both designs show 42-GHz modulation bandwidth with a high bandwidth-to-drive-voltage ratio of >23 GHz/V. Polarization insensitivity of modulator transmission and chirp is demonstrated. Technical realization has been done in ridge waveguide technology with low-pressure MOVPE, reactive ion etching (RIE) for semiconductor etching and polyimide for planarization.     

Admissible short-time uncertainty in networked control systems

Increasing in number, busses and wireless networks are used as signal transmission in control systems. Networked control systems of this kind are characterized by occasional or arbitrary time delay or interruptions of minor loops. These influences are modelled as short-time uncertainties, in contrast to robust control systems in the literature, which are mainly studied as families with time-invariant uncertainties. Severe uncertainties are taken into consideration even if they cause short-time instability. An uncertainty can be valuated admissible if the accompanying signal amplitude or energy increase remains bounded. A third-order example with unstable behavior in a short-time interval is carried out in detail. I dedicate this article to my fellow professor O. Univ.-Prof. Dr. Gerfried Zeichen. Very affectionately yours, A. W.