Improving wheelset stability of railway vehicles by using an H∞/LPV active wheelset system

The complexity of railway vehicle structures has been part of an evolutionary process for almost two hundred years. Challenges such as increased weight, increased maintenance, higher costs and energy consumption have become common. The vision for future railway vehicles is to reduce complexity, hence enable simpler structures and reduce maintenance and cost, and of course various research challenges arise from this. In fact, a number of papers in the railway engineering literature have presented practical ways to control steering of railway vehicles to improve performance. The model of the railway wheelset is highly nonlinear, mainly due to the nature of the wheelset structure and the related wheel-rail contact forces involved during operation. In this paper, the simplest design in terms of retrofitting, the actuated solid-axle wheelset is considered, we investigate actively controlled wheelsets from a Linear Parameter Varying (LPV) control aspect. We use the grid-based LPV approach to synthesize the H∞/LPV controller, which is self-scheduled by the forward velocity, as well as the longitudinal and lateral creep coefficients. The aim of the controller is to reduce the lateral displacement and yaw angle of the wheelset. Simulation results show that the proposed controller ensures the achievement of the above targets in the considered frequency domain up to 100 rad/s. © 2021 Budapest University of Technology and Economics. All rights reserved

Designing LQR controllers for an active anti-roll bar system with a flexible frame model of a single unit heavy vehicle

Rollover accidents of heavy vehicles often cause serious consequences both in terms of vehicle and environmental damage as well the loss or injury of drivers, passengers and ordinary civilians. Currently, the active anti-roll bar system is considered as the most effective solution in enhancing vehicle roll stability. In this paper, we firstly investigated the role of a flexible frame of a single unit heavy vehicle in the rollover process. This approach is an important step forward in the research of the active anti-roll bar system. Then, the LQR control method is applied in designing controllers for the active anti-roll bar control system with this frame model. The active torque of the anti-roll bar system is considered as the control signal. The simulation results in the frequency and time domains with a double lane change maneuver show that the vehicle's roll stability is improved by over 30 % compared to a vehicle using a passive anti-roll bar system. © 2021 Budapest University of Technology and Economics. All rights reserved

Dielectric properties of conducting polymer

The dielectric properties of conducting polymer composites containing polypyrrole (PPy) crushed films, PPy powder, polyaniline (PAn) base and acid powders as the dispersants and silicone rubber and vinyl ester as matrix materials have been investigated in the frequency range 2-18 GHz. The dielectric parameters such as the real part, epsiprime, and imaginary part, epsiPrime, of the permittivity and loss tangent, tandelta, increase with increasing conductivity and concentration of the dispersant. The geometrical shape of the dispersant governs the ability of conductive network formation which is indicated by a large drop in the resistivity of the composite. Also, dispersant/matrix interactions and physical properties of the matrix influence the agglomeration of the dispersant phase which, in turn, affects the dielectric properties of the composites. Flakes of PPy obtained by crushing highly conductive films and large PAn powder aggregates were unable to form a conducting network. The composites without a network of dispersant exhibit low dielectric parameters. On the other hand, high values of tan delta ranging from 0.7&ndash;1.1 were achieved for the PPy powder (15 parts)/silicone rubber composites where a conducting network was observed. <br /

Structural Characterization of Conducting Polypyrrole Using C-13Cross-Polarization Magic-Angel-Spining Solid-State Nuclear-Magnetic-Resonance Spectroscopy

C-13 nuclear magnetic resonance (n.m.r.) has been used to study polypyrrole and N-substituted polypyrrole in the solid state. The extent of oxidation appears to be counterion-dependent; in particular, the quinoid structure appears favoured in the films prepared with dodecyl sulfate. Resonances associated with the quinoid unit are lost upon reduction of the polypyrrole film, which supports the idea that the quinoid structure is associated with the oxidized form of polypyrrole. N-substituted polypyrroles have a more distinct resonance at 110 ppm, which is linked to lower degrees of oxidation or charge delocalization in these systems. The decrease in conductivity of polypyrrole upon thermal ageing in air is associated with both the loss of counterion ('thermal dedoping') and the decomposition of the quinoid structure in the polymer backbone. There is no indication of carbonyl formation in the solid-state n.m.r. spectra obtained in the present study

Synthesis and biological evaluation of novel phane-structured diazacrowns containing γ-piperidone and pyridine rings

Six novel phane-structured diazacrowns containing γ-piperidone and pyridine rings were synthesized from podand 2-+,6-bis(2-formylphenoxymethyl)pyridine, with the γ-piperidone moiety having been constructed in the course of its domino condensation with simple ketones and ammonium acetate. The compounds were tested in vitro for antimicrobial and cytotoxic activity against four human cancer cell lines (Hep-G2, RD, MCF-7, Lu-1) and the Vero cell line. X-Ray structure study of one representative compound revealed its rac-1RS,23SR,24RS,26SR configuration. © 202

Crystal structure of 22,24,25-trimethyl-8,11,14-trioxa-25-azatetracyclo[19.3.1.02,7.015,20]pentacosa-2,4,6,15(20),16,18-hexaen-23-one

The title compound, C24H29NO4, is the product of a Petrenko-Kritchenko condensation of 1,5-bis(2-formylphenoxy)-3-oxapentane, pentan-3-one and methylammonium acetate in ethanol. The molecule has mirror symmetry. The aza-14-crown-3 ether ring adopts a bowl conformation stabilized by a weak intramolecular C - H⋯O hydrogen bond. The conformation of the C - O - C - C - O - C - C - O - C polyether chain is t-g+-t-t-g--t (t = trans, 180°; g = gauche, ±60°). The dihedral angle between the benzene rings fused to the aza-14-crown-4-ether moiety is 72.68(4)°. The piperidinone ring adopts a chair conformation. The nitrogen atom has a trigonal-pyramidal geometry, the sum of the bond angles being 335.9°. In the crystal, the molecules are linked by weak C - H⋯O interactions, forming zigzag chains propagating along the [100] direction

Crystal structure of 22,24,25-trimethyl-8,11,14-trioxa-25-azatetracyclo[19.3.1.02,7.015,20]pentacosa-2,4,6,15(20),16,18-hexaen-23-one

The title compound, C24H29NO4, is the product of a Petrenko-Kritchenko condensation of 1,5-bis(2-formylphenoxy)-3-oxapentane, pentan-3-one and methylammonium acetate in ethanol. The molecule has mirror symmetry. The aza-14-crown-3 ether ring adopts a bowl conformation stabilized by a weak intramolecular C - H⋯O hydrogen bond. The conformation of the C - O - C - C - O - C - C - O - C polyether chain is t-g+-t-t-g--t (t = trans, 180°; g = gauche, ±60°). The dihedral angle between the benzene rings fused to the aza-14-crown-4-ether moiety is 72.68(4)°. The piperidinone ring adopts a chair conformation. The nitrogen atom has a trigonal-pyramidal geometry, the sum of the bond angles being 335.9°. In the crystal, the molecules are linked by weak C - H⋯O interactions, forming zigzag chains propagating along the [100] direction