Control of Towing Kites for Seagoing Vessels

In this paper we present the basic features of the flight control of the SkySails towing kite system. After introduction of coordinate definitions and basic system dynamics we introduce a novel model used for controller design and justify its main dynamics with results from system identification based on numerous sea trials. We then present the controller design which we successfully use for operational flights for several years. Finally we explain the generation of dynamical flight patterns.Comment: 12 pages, 18 figures; submitted to IEEE Trans. on Control Systems Technology; revision: Fig. 15 corrected, minor text change

Sensors and Navigation Algorithms for Flight Control of Tethered Kites

We present the sensor setup and the basic navigation algorithm used for the flight control of the SkySails towing kite system. Starting with brief summaries on system setup and equations of motion of the tethered kite system, we subsequently give an overview of the sensor setup, present the navigation task and discuss challenges which have to be mastered. In the second part we introduce in detail the inertial navigation algorithm which has been used for operational flights for years. The functional capability of this algorithm is illustrated by experimental flight data. Finally we suggest a modification of the algorithms as further development step in order to overcome certain limitations.Comment: 6 pages, 9 figures, submitted to European Control Conference (ECC) 201

Sloshing-aware attitude control of impulsively actuated spacecraft

Upper stages of launchers sometimes drift, with the main engine switched-off, for a longer period of time until re-ignition and subsequent payload release. During this period a large amount of propellant is still in the tank and the motion of the fluid (sloshing) has an impact on the attitude of the stage. For the flight phase the classical spring/damper or pendulum models cannot be applied. A more elaborate sloshing-aware model is described in the paper involving a time-varying inertia tensor. Using principles of hybrid systems theory we model the minimum impulse bit (MIB) effect, that is, the minimum torque that can be exerted by the thrusters. We design a hybrid model predictive control scheme for the attitude control of a launcher during its long coasting period, aiming at minimising the actuation count of the thrusters

Genetical and functional investigation of fliC genes encoding flagellar serotype H4 in wildtype strains of Escherichia coli and in a laboratory E. coli K-12 strain expressing flagellar antigen type H48

BACKGROUND: Serotyping of O-(lipopolysaccharide) and H-(flagellar) antigens is a wideley used method for identification of pathogenic strains and clones of Escherichia coli. At present, 176 O- and 53 H-antigens are described for E. coli which occur in different combinations in the strains. The flagellar antigen H4 is widely present in E. coli strains of different O-serotypes and pathotypes and we have investigated the genetic relationship between H4 encoding fliC genes by PCR, nucleotide sequencing and expression studies. RESULTS: The complete nucleotide sequence of fliC genes present in E. coli reference strains U9-41 (O2:K1:H4) and P12b (O15:H17) was determined and both were found 99.3% (1043 of 1050 nucleotides) identical in their coding sequence. A PCR/RFLP protocol was developed for typing of fliC-H4 strains and 88 E. coli strains reacting with H4 antiserum were investigated. Nucleotide sequencing of complete fliC genes of six E. coli strains which were selected based on serum agglutination titers, fliC-PCR genotyping and reference data revealed 96.6 to 100% identity on the amino acid level. The functional expression of flagellin encoded by fliC-H4 from strain U9-41 and from our strain P12b which is an H4 expressing variant type was investigated in the E. coli K-12 strain JM109 which encodes flagellar type H48. The fliC recombinant plasmid carrying JM109 strains reacted with both H4 and H48 specific antisera whereas JM109 reacted only with the H48 antiserum. By immunoelectron microscopy, we could show that the flagella made by the fliC-H4 recombinant plasmid carrying strain are constituted of H48 and H4 flagellins which are co-assembled into functional flagella. CONCLUSION: The flagellar serotype H4 is encoded by closely related fliC genes present in serologically different types of E. coli strainswhich were isolated at different time periods and geographical locations. Our expression studies show for the first time, that flagellins of different molecular weigth are functionally expressed and coassembled in the same flagellar filament in E. coli

A Hybrid Model Predictive Control Approach to Attitude Control with Minimum-Impulse-Bit Thrusters

This paper studies an important aspect of attitude control for a launcher's upper stage: the minimum impulse bit (MIB), that is, the minimum torque that can be exerted by the thrusters. We model this effect using principles of hybrid systems theory and we design a hybrid model predictive control scheme for the attitude control of a launcher during its long coasting period, aiming at minimizing the number of thrusters' actuations. We apply the proposed methodology to a nonlinear model of a typical upper stage with multi-payload capability

Water quality and water-rock interaction in the Harz Mountains (Germany)

The Harz Mountains, known for ancient silver and base metal mining, are an important drinking water supply region for northern Germany today. The water quality of the Harz Mountains is mainly influenced by atmospheric depositions, water-rock inter- actions and biological activities. Anthropogenic influences are minor. Springs, creeks, lakes and reservoirs have relatively low mineralisation. Measured as specific electrical conductivity, the mineralisation of the different water bodies ranges from about 15 to 650 µS/cm. Only deep springs and mine waters reach higher values. Despite dilution effects due to different rainwater amounts, water-rock interaction can be retraced by the chemical water composition, especially by trace metals and rare earth element concentrations. Examples of water-rock interaction are discussed for granite, greywacke and limestone