Dynamics of digitally controlled forced vibration of suspended cables

Dynamics of suspended cables with active vibration control is studied. The control device is an electrical vibration absorber that is driven by a motor and that may be fixed at any position along the cable. The absorber applies a control force that reduces vibration amplitude at the position where it is placed. The methodology is efficient for attenuating high-frequency, low-amplitude vibration due to periodic excitation that may consider wind effect. The dynamic behavior is described by a mechanical model of the absorber and the cable at the location where the absorber is attached. The model takes into account such practical problems as time delay and backlash at the driving, which lead to limitation in the applicability of control. Time delay occurs in digital control, because samples of data are taken at discrete time intervals and response is provided after the sampling delay. Backlash influences control when the direction of control force changes, since the control force is not transmitted in the small domain of backlash. The present research examines the effects of time delay and backlash on the local control of cable vibration, and assesses the range of time delay and backlash when the control can be applied successfully. Moreover, the presence of time delay and backlash together results in a motion with some irregularity what justifies the detailed study of the dynamic behavior in order to evaluate the types of motion that may arise in such systems

Csatolt diszkrét és folytonos dinamikai rendszerek stabilitása és nemlineáris rezgései = Stability and nonlinear vibrations of coupled discrete and continuous dynamical systems

Gépészmérnöki feladatok megoldásakor, ahol mozgások leírása, tervezése a cél, hagyományosan folytonos szemlélet dominál. A műszaki-technológiai fejlesztés azonban sok olyan rezgési problémába ütközött az utóbbi évtizedben, ahol a fejlődés további korlátját jelentő rezgéseket diszkrét hatások okozzák. Ennek alappéldái a robotika rezgési jelenségei, ahol a newtoni dinamikával leírható, folytonosan viselkedő rendszert mikroprocesszorok segítségével szabályoznak, és így a mintavételezésen és kerekítési hibákon keresztül időbeli és térbeli digitális hatásokat kapcsolnak hozzá. Diszkrét és folytonos rendszerek dinamikájának együttes vizsgálatára szükség van akkor is, ha a fizikai rendszer maga szabályozza a folytonos rendszert diszkrét módon, mint a nagy amplitúdójú szerszámgéprezgések, a gyorsan forgó tengelyek rubbing jelensége, vagy a kerekek térbeli gördülése és csúszása során jelentkező kapcsolgatás esetén. Olyan algoritmusokat dolgoztunk ki, amelyek a lehető legkevesebb numerikus közelítést tartalmazva, pontosan és egyszerűen adják meg az ilyen rendszerek stabilitásának feltételeit, illetve a stabilitásvesztéskor kialakuló rezgések jellegét, frekvenciáit, amplitúdóit. Ezekkel a módszerekkel sikerült pl. robotok emberekkel való érintkezéséhez szükséges erőszabályozásokat terveznünk az EU rehabilitációs robot projektjében, új nagysebességű marási technológiákat javasolnunk, magyarázatot adnunk kerekek fékezéskor kialakuló laterális (simmiző) rezgésére. | Time-continuous approach dominates the solution of those problems of mechanical engineering where the goal is the analysis or design of certain motions. The technological development, however, has often been set back during the last decade by vibration problems originated in discrete effects. Basic example is the vibration phenomenon of robots, where the continuous physical system described the Newtonian laws is subjected to control by means of microprocessors. These introduce digital effects both in time and space via the sampling and the round-off, respectively. The coupled discrete and continuous systems dynamics are in the focus of critical vibration phenomena also in those cases when the physical system regulates itself in a discrete way. This happens during the large amplitude oscillations of machine tools, the rubbing phenomenon of rotors, or the subsequent switches between the rolling and sliding dynamics of wheels. We developed algorithms that give the stability conditions of these systems in a reliable, efficient and still simple way. Moreover, these methods also describe the nature of these vibrations, provide their frequency content and amplitude range. This way, for example, we designed the force control of rehabilitation robots in an EU project where human and robot must interact by touching each other, suggested new technological parameter domains for high-speed milling, or explained the lateral vibrations (shimmy) of wheels during braking

Analytical and Experimental Study of Beam Bending Vibration

This study presents free bending vibration analysis of beams of glass epoxy material. The analytical and the modal model (experimental) methods were used to conduct the investigation. The experiment represents basic concepts of the modal model analysis method, which allows us to find the beam's natural frequencies and vibrational mode shapes. The analytical solution was found using Maple and compared to the frequencies obtained experimentally

Synthesis, Characterization and Application of Platinum(II) Complexes Incorporating Racemic and Optically Active 1-Phenyl-1,2,3,6-Tetrahydrophosphinine Ligand

An efficient resolution method was elaborated for the preparation of (+)-4-chloro-5-methyl-1-phenyl-1,2,3,6-tetrahydrophosphinine oxide using the acidic Ca2+ salt of (–)-O,O-di-p-toluoyl-(2R,3R)-tartaric acid. Crystal structure of the diastereomeric complex was evaluated by single crystal X-ray analysis. Beside this, the absolute P-configuration was also determined by a CD spectroscopic study including theoretical calculations. The tetrahydrophosphinine oxide was then converted to the corresponding platinum complex whose stereostructure was investigated by high level quantum chemical calculations. The Pt-complex was tested as catalyst in the hydroformylation of styrene

Intramolecular Cooperative Effects in Multichromophoric Cavitands Exhibiting Nonlinear Optical Properties

We report on the design, synthesis, and characterization of a new class of multichromophoric cavitands based on resorcin[4]arenes. The novel compounds have exhibited high values of second-order nonlinear optical (NLO) properties, as evidenced by electric-field-induced second harmonic generation (EFISHG) measurements. Theoretical calculations indicate the presence of edge-to-face T-shaped interactions between the aromatic building blocks within these multichromophoric systems, which is further supported by the detection of hypsochromic shifts in UV-vis and upfield aromatic chemical shifts in 1H NMR. We proved for the first time that the gain in the quadratic hyperpolarizabilities of multichromophoric NLO macrocycles, originating from the near parallel orientations of the subchromophores, can be partially suppressed if the distance between the dipolar subunits falls into a specific range, where intramolecular cooperative and/or collective effects are operative. Our finding will contribute to the better understanding of the phenomenon of cooperativity in new molecular materials with promising NLO properties. (Figure Presented). © 2015 American Chemical Society