Application of inverse linear parametric models in the identification of rail track irregularities

Requirements for current trains to be increasingly available have created the need to develop systems that can predict the quality of both trains and infrastructure components. The paper presents a new approach to the detection of rail truck irregularities, based on the measurements of bearing box acceleration during the operation of rail vehicles. The proposed procedure is based on an inverse problem solution, estimating track irregularities from measured acceleration of the applied model of vehicle dynamics. The simulation study of the proposed method, as well as its implementation, is presented. The method has been successfully applied for the identification of rail irregularities on a typical Polish railroad and vehicle.     

Control of underactuated mechanical systems with servo-constraints

This paper deals with a class of controlled mechanical systems in which the number of control inputs, equal to the number of desired system outputs, is smaller than the number of degrees of freedom. The related inverse dynamics control problem, i.e., the determination of control input strategy that force the underactuated system to complete the partly specified motion, is a challenging task. In the present formulation, the desired system outputs, expressed in terms of the system states, are treated as servo-constraints on the system, and the problem is viewed from the constrained motion perspective. Mixed orthogonal-tangent realization of the constraints by the available control reactions is stated, and a specialized methodology for solving the “singular” control problem is developed. The governing equations are manipulated to index three differential-algebraic equations, and a simple numerical code for solving the equations is proposed. The feedforward control law obtained as a solution to these equations can then be enhanced by a closed-loop control strategy with feedback of the actual servo-constraint violations to provide stable tracking of the reference motion in the presence of perturbations and modeling uncertainties. An overhead trolley crane executing a load-prescribed motion serves as an illustration. Some results of numerical simulations are reported.     

Chatter Vibration Surveillance by the Optimal-linear Control of Spindle Speed and Randomly Varying Spindle Speed

Tool-workpiece relative vibration plays principal role during the process of milling with slender ball end mills. Due to certain conditions, a loss of stability and generation of self-excited chatter vibration will appear. The paper is devoted to a new approach towards vibration surveillance of rotating tools in modern milling machines. Dynamic analysis of a slender ball end milling process has been performed and dynamics of controlled structure is described. In order to reduce vibration level, instantaneous change in the spindle speed appears as control command, and thus the method of vibration surveillance by the spindle speed optimal-linear control has been developed. Due to quality of machined surface being worse while milling with high tilting angle of the tool, the other method of milling with randomly varying spindle speed is presented. It allows us to maintain a high efficiency of surveillance without worsening of the machining quality. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

General Construction of Non-Dense Disjoint Iteration Groups on the Circle

Let be a disjoint iteration group on the unit circle , that is a family of homeomorphisms such that F ^v1 ○ F ^v2 = F ^v1+v2 for v ₁, v ₂ ∈ V and each F ^v either is the identity mapping or has no fixed point ((V, +) is a 2-divisible nontrivial Abelian group). Denote by the set of all cluster points of {F ^v (z), v ∈ V} for . In this paper we give a general construction of disjoint iteration groups for which .     

The effect of structure on the thermoresponsive nature of well‐defined poly(oligo(ethylene oxide) methacrylates) synthesized by ATRP

Statistical copolymers of di(ethylene glycol) methyl ether methacrylate (MEO₂MA) and tri(ethylene glycol) methyl ether methacrylate (MEO₃MA) were synthesized by atom transfer radical polymerization (ATRP) providing copolymers with controlled composition and molecular weights ranging from M_n = 8,300–56,500 with polydispersity indexes (M_w/M_n) between 1.19 and 1.28. The lower critical solution temperature (LCST) of the copolymers increased with the mole fraction of MEO₃MA in the copolymer over the range from 26 to 52 °C. The average hydrodynamic diameter, measured by dynamic light scattering, varied with temperature above the LCST. These two monomers were also block copolymerized by ATRP to form polymers with molecular weight of M_n = 30,000 and M_w/M_n from 1.12 to 1.21. The LCST of the block copolymers shifted toward the LCST of the major segment, as compared to the value measured for the statistical copolymers at the same composition. As temperature increased, micelles, consisting of aggregated PMEO₂MA cores and PMEO₃MA shell, were formed. The micelles aggregated upon further heating to precipitate as larger particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 194–202, 2008     

Formation of poly(ethylene phosphates) in polycondensation of H3PO4 with ethylene glycol. Kinetic and mechanistic study

Conditions of synthesis of poly(ethylene phosphates) in reaction of H₃PO₄ with HOCH₂CH₂OH (EG), the actual path of polycondensation, and structure of the obtained polymers (mostly oligomers) and kinetics of reaction are described. Preliminary kinetic information, based on the comparison of the MALDI‐TOF‐ms and ³¹P{¹H} NMR spectra as a function of conversion is given as well. Because of the dealkylation process fragments derived from di‐ and triethylene glycols are also present in the repeating units. Structures of the end groups (? CH₂CH₂OH or ? OP(O)(OH)₂) depend on the starting ratio of [EG]₀/[H₃PO₄]₀, although even at the excess of EG the acidic end groups prevail because of the dealkylation process. In MALDI‐TOF‐ms products with P_n equal up to 21 have been observed. The average polymerization degrees (P_n) are lower and have been calculated from the proportion of the end groups. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 830–843, 2008     

Tripodal imidazole containing ligands for copper catalyzed ATRP

Tripodal imidazole containing ligands, bis((2‐pyridyl)methyl)(1‐methylimidazole‐2‐yl)methyl)amine (BPIA) and bis(1‐methylimidazole‐2‐yl)methyl)((2‐pyridyl)methyl)amine (BIPA), were synthesized and used for copper catalyzed atom transfer radical polymerization (ATRP) of n‐butyl acrylate (nBA). The molecular weights of poly(n‐butyl acrylate) (PnBA) catalyzed by CuBr/BPIA and CuBr/BIPA complexes increased linearly with nBA conversions and they were close to theoretical values with low polydispersities. ATRP equilibrium rate constant (K_ATRP) measurements showed that bothCuBr/BPIA and CuBr/BIPA complexes had high K_ATRP values, similar to that of CuBr/tri(2‐pyridylmethyl)amine (TPMA), which is one of the ATRP most active ligands. Activators regenerated by electron transfer (ARGET) ATRP of nBA with CuBr₂/BPIA and CuBr₂/BIPA complexes were also conducted and polymerization reached high nBA conversions, resulting in PnBA with low polydispersities. This suggests that the copper complexes with BPIA and BIPA were sufficiently stable and active to conduct ATRP when catalyst concentration was low. ARGET ATRP to form high molecular weight PnBA with CuBr₂/BPIA and CuBr₂/BIPA complexes was also successful. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2015–2024, 2008     

Decomposability of Polytopes

A known characterization of the decomposability of polytopes is reformulated in a way which may be more computationally convenient, and a more transparent proof is given. New sufficient conditions for indecomposability are then deduced, and illustrated with some examples.