Motion planning and actuator specialization in the control of active-flexible link robots

Trajectory planning is a well-known open-loop control strategy to minimize residual vibrations in point-to-point tasks of systems featuring mechanical flexibility. However, the major drawback of open-loop control is its limitation in coping with modeling uncertainty. In this paper a novel approach to trajectory planning based on LQR theory is proposed and applied to a single flexible link robot. To improve performance under parameter uncertainty the strategy is combined with collocated vibration control through piezoelectric actuation of the link. This combination raises the issue of the roles and the contribution of each actuator type to the overall performance of the maneuver. An actuator specialization is proposed where the joint controller is responsible for the gross vibrationless motion of the link, while the link actuators are expected to deal only with residual vibrations that may arise from modeling errors. Simulation and experimental results validate the trajectory planning methodology and the combination of the open-loop strategy with collocated vibration control.     

Synthesis and Characterization of N‐methylenephenyl Phosphonic Chitosan

Chitosan is a natural based polymer obtained by alkaline deacetylation of chitin, exhibiting excellent properties such as non‐toxicity, biocompatibility and biodegradability. N‐Methylenephenyl phosphonic chitosan (NMPPC) is synthesized from chitosan by reacting with phenyl phosphonic acid using formaldehyde. The NMPPC was characterized by FTIR, ³¹P‐NMR, X‐ray diffraction, scanning electron microscopy, thermogravimeteric analysis and solubility studies. A significant decrease of molecular weight was observed in the NMPPC. The TGA studies suggested that NMPPC has less thermal stability than chitosan. The X‐ray diffraction analysis showed that NMPPC was amorphous in nature. The solubility property of the polymer was improved after the incorporation of a phenyl phosphonic group.     

Comparative study of the oxidative and thermal stability of vegetable oils to be used as lubricant bases

Demand for lubricating oils is increasing in the growing Brazilian economy. The use of vegetable bases in exchange of minerals can bring socio-economic and environmental benefits for Brazil. The purpose of this study is to compare the thermal and oxidative stability of vegetable oils related to the bases commonly used as lubricants. In this study, thermogravimetric analysis of castor oil, cotton oil, macauba’s almond oil, passion oil, paraffinic mineral oil, naphthenic oil (NH-140) and synthetic oil (Etro) was performed in inert and oxidative atmosphere to study the thermal and oxidative degradation of the vegetable oils related to the most common lubricants’ oils base. These oils’ oxidation stability were determined by standard procedures (ISO 6886). The use of mineral oil’s additives in these vegetable oils was tested to verify the viability of these additives to improve the oxidative stability of the vegetable oils. The castor oil and the cotton oil presented results of thermal analysis similar to the mineral and synthetic bases values. The castor oil was the only vegetable oil that showed a great oxidative stability. All other vegetable oils had their oxidative stability significantly increased by the additives.     

Electrochemical Oxidation of Ibuprofen and Its Voltammetric Determination at a Boron‐Doped Diamond Electrode

The electrochemical oxidation of ibuprofen at a boron‐doped diamond electrode (BDDE) and its voltammetric determination is reported for the first time. A well‐defined oxidation peak was observed at around 1.6 V in 0.1 mol L^?1 H₂SO₄ solution with 10 % (v/v) ethanol at the BDDE surface activated by either cathodic or anodic pretreatments. A differential‐pulse voltammetric method for the determination of ibuprofen in pharmaceutical formulations was optimized with a detection limit of 5 µmol L^?1 and compared with the British Pharmacopeia method.     

One-Step Protection-Free Synthesis of 3-Aryl-5-hydroxyalkyl-1,2,4-oxadiazoles as Building Blocks

A simple and straightforward synthesis of 3-aryl-5-hydroxyalkyl-1,2,4-oxadiazoles is described. The reaction among arylamidoximes, ethyl glycolate or ethyl lactate, and potassium carbonate in refluxing toluene afforded the desired 1,2,4-oxadiazoles in moderate to good yields. The synthesis has been accomplished in a single step, avoiding protection–deprotection protocols.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Synthesis of New Tetrazole Derivatives of α,α‐Trehalose

Five new nitrogen heterocycles, mono‐and disubstituted tetrazoles with potential synthetic and pharmacological interest, were synthesized from α, α‐trehalose via the alkylation of commercial tetrazoles. This method appears to have broad scope with respect to the variations at positions 1 and 2 of tetrazole.     

An unexpected formation of pyrazolopyrimidines during the attempted to obtain 5-substituted tetrazoles from carbonitriles

In this Letter, we described the synthesis of new 5-(5-amino-1-aryl-1H-pyrazole-4-yl)-1H-tetrazoles 2a–c from 5-amino-1-aryl-1H-pyrazole-4-carbonitriles 1a–c as well as the unexpected 1H-pyrazolo[3,4-d]pyrimidine derivatives 6a–c from 5-amino-1-aryl-3-methyl-1H-pyrazole-4-carbonitriles 4a–c, instead of 5-(5-amino-1-aryl-3-methyl-1H-pyrazole-4-yl)-1H-tetrazoles 5a–c as desired. In an attempt to obtain these tetrazole derivatives containing the methyl group at C3-position in the pyrazole ring, the amino group in 5-amino-1-(4-methoxyphenyl)-3-methyl-1H-pyrazole-4-carbonitrile 4c was protected by the reaction with sodium hydride and di-tert-butyl-dicarbonate (Boc). The tetrazole derivative 5c was synthesized from the protected compound 7c using analogue methodology to obtain 2a–c and 6a–c.