Crawler robot kinematics modeling by using a two-wheeled approach

The aim of this paper is to analyze the kinematics of a small crawler robot. A mathematical model of kinematics based on a two-wheeled approach is proposed. This model is experimentally verified using vision-based motion measurements of a crawler vehicle equipped with encoders and a remote control system. It is assumed that the vehicle moves along a few curves with different angular speeds of its wheels. Based on the model of motion and the values of these speeds, numerical simulations are investigated. The results obtained from numerical and experimental validation are presented and discussed. The comparison delivered some important conclusions.

     

Numerical assessment of springback for the deep drawing process by level set interpolation using shape manifolds

In this paper, we introduce an original shape representation approach for post-springback characterization based on the automatic generation of parameterized level set functions. The central idea is the concept of the shape manifold representing the design domain in the reduced-order shape-space. Performing Proper Orthogonal Decomposition on the shapes followed by using the Diffuse Approximation allows us to efficiently reduce the problem dimensionality and to interpolate uniquely between admissible input shapes, while also determining the smallest number of parameters needed to characterize the final formed shape. We apply this methodology to the problem of springback assessment for the deep drawing operation of metal sheets.     

Performance optimization of polymer electrolyte membrane fuel cells using the Nelder-Mead algorithm

The direct-search simplex method for function optimization has been adapted to performance optimization of polymer electrolyte membrane fuel cells (PEMFCs). The established method is strongly application oriented and uses only experimentally determined data for optimization. It is not restricted to discrete parameters optimums and does not require the use of third-party software or computational resources. Hence, it is easy to implement in fuel cell testing stations. The optimization consists of finding, for a given fuel cell load, an optimum set of values of the 7 fuel cell operating parameters: the fuel cell temperature, the reactants' stoichiometric ratios, the reactants' inlet relative humidity, and the reactants' outlet pressures, resulting in the highest fuel cell performance. The performance is measured using a scalar function of the operating parameters and the load and can be defined according to needs.Two PEMFC performance functions: the fuel cell voltage and the system-related fuel cell efficiency were optimized using the procedure for practically sized PEMFC stacks of two designs. With respect to the nominal operating conditions defined as optimal for each stack design by its manufacturer, the gains from the optimization procedure were up to over 12% and up to over 7% for the stack voltage and efficiency, respectively. The validation of the procedure involved 5 stack specimens and four laboratories and consistent results were obtained.     

Effect of plasma treatment on the surface properties of polydimethylsiloxane

In this work, the analysis of the plasma modification of polydimethylsiloxane (PDMS) substrates was conducted. The influence of the modification onto the changes occurred within the geometrical structure and chemical composition of the surface was analyzed. Due to the study of the atomic force microscopy, it was possible to determine the relationships between the surface development and applied process parameters, defining the conditions facilitating to obtain isotropic or anisotropic orientations of wrinkles. A precise analysis of the chemical composition of the surface, executed before and after the modification processes, enabled to define the changes in their elementary composition. Moreover, the modification influence onto the changes of the contact angle and the surface free energy were also analyzed. So, based on the research it was stated that the increase of value of the surface free energy is proportional to the sp³ phase contents in the DLC coatings. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41635.     

The improvement of ecological characteristics of coatings from cured epoxy resins by hot water extraction

Amine curing agents pose serious health hazards and controlling their release is crucially important. Extraction of unbounded amine from cured epoxy polymers can improve the ecological characteristics of such products. Even 1 min exposure of cured epoxy resins to hot water reduces three- to ten-fold the residual amount of amine present in the epoxy polymer. Different temperatures and extraction times were tested, enabling the selection of the most optimal extraction conditions, which correspond to 5 min of heating in 100°C. This additional cost-effective extraction step is very easy to perform and leads to a significant reduction of unbounded curing agent, making cured epoxy resins much more eco-friendly products. The documented positive and linear trends of logarithms of viscosity and the amount of released amine suggest the selection from such curing agents and such epoxy resins that are characterized by lowest possible viscosities, which guarantees that there is only a low amount of unbounded amine that needs to be released from the polymer.     

Nonlinear Absorption of Submicrometer Grain‐Size Cobalt‐Doped Magnesium Aluminate Transparent Ceramics

Transparent cobalt‐doped magnesium aluminate spinel (Co:MgAl₂O₄) ceramics with a submicrometer grain size were prepared by spark plasma sintering. For the first time, the nonlinear absorption of Co:MgAl₂O₄ transparent ceramics was experimentally demonstrated. Both ground state absorption (σ_GSA) and excited state absorption (σ_ESA) were estimated using the solid‐state slow saturable absorber model based on absorption saturation measurements performed at 1.535 μm. σ_GSA and σ_ESA for 0.03 at.% Co:MgAl₂O₄ were found to be 4.1 × 10^?19 cm² and 4.0 × 10^?20 cm², respectively. In the case of 0.06 at.% Co:MgAl₂O₄ ceramics, σ_GSA = 2.6 × 10^?19 cm² and σ_ESA= 5.3 × 10^?20 cm² were determined.     

Polymerization of β-butyrolactone initiated with Al(OiPr)3

Polymerization of β-butyrolactone has been studied in toluene with Al(OⁱPr)₃ as an initiator. The ring-opening polyaddition proceeds through a coordination–insertion mechanism at a very low rate. Well defined α-isopropylester, ω-hydroxy poly(β-butyrolactone)s (PBL) are formed with a narrow molecular weight distribution at low monomer-to-initiator molar ratios, When this ratio is higher (ca. 170), a competition occurs between propagation and side reactions, i.e. elimination, inter- and intra-molecular transesterifications and thermal degradation, which is responsible for a loss of control of the PBL molecular charcteristics. The addition of a Lewis base (1 equivalent of nicotine/Al) to the Al-alkoxide initiator has no significant effect on the polymerization rate, although the chain microstructure is deeply affected since predominantly syndiotactic PBL chains are formed (63% syndio-diads) in contrast to a completely atactic polymer in the absence of nicotine.     

Experimental verification of the kinetic model for the reaction yielding linear polyurethanes,claiming dependence of oligomer reactivities on molecular weights. III

Taking advantage of the algorithm developed earlier which makes it possible to calculate rate constants for the parallel-subsequent reactions of the kinetic model for the diisocyanate and diol polyaddition process, a mathematical model was developed for this process which then was subjected to mathematical decomposition. The procedure adopted allowed me to numerically resolve the obtained system of differential equations and to perform the numerical simulation of the polymerization process studied. For the reactions of 2,4-TDI and 1,4-butanediol, the results obtained were compared to experimental concentrations of urethane oligomer fractions found by means of GPC. It was found that the model suggested provides a better fit than does the model claiming dependence of chemical activity of oligomers solely on reactivity specifications for their functional groups. © 1996 John Wiley & Sons, Inc.