The formation control of satellites for remote sensing applications has received considerable attention during the past decade. This work deals with the development of a formation control strategy for the circular formation of a group of satellites. In this paper, artificial potential field method is used for path planning, and sliding mode control (SMC) technique is used for designing a robust controller. A fuzzy inference mechanism is utilized to reduce the chattering phenomenon inherent in the conventional SMC. An adaptive tuning algorithm is also derived based on Lyapunov stability theory to tune the fuzzy parameter. The proposed fuzzy-SMC-based technique is intended to compensate for the modeling uncertainties existing in practical applications. The results of simulations done for a group of five satellites making a circular formation confirm the stability and robustness of the present scheme.
Depth-dependent hardness variation of dimethylamine borane-reduced electroless Ni–5 wt-%B deposits has been examined using the nanoindentation technique. The deposits were characterised using ICP-OES, FESEM, XRD and DSC for evaluating the composition, morphology, structure and phase transformation behaviour, respectively. Coatings were also analysed for hardness and wear resistance. The surface of the as-plated deposit exhibits a typical nodular morphology. DSC traces show the presence of a single exothermic peak at 313°C conforming to its phase transformation. X-ray diffraction pattern of as-prepared deposit contains a mixture of amorphous and sharp microcrystalline nickel peaks. Heat-treated coating exhibits improved hardness and wear resistance. Depth-dependent nanohardness profile of as-deposited film neither obeys Nix–Gao nor the Lam–Chong model of indentation.
An intramolecular, alkyne iminium ion cyclization of vinylogous carbamates derived from o-alkynyl anilines and N-protected homopropargyl amines is developed for the stereoselective construction of trans-2,3-disubstituted indolines and pyrrolidine derivatives, respectively. The regioselectivity of the alkyne iminium ion cyclization could be switched using a hydroxy group as an internal nucleophile resulting in cyclic ether-fused 1,2-dihydroquinolines. The entire process of nitrogen heterocycle formation can also be carried out in a 'one-pot' manner starting from o-iodo aniline derivatives.
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