Trajectory-tracking of 6-RSS Stewart-Gough manipulator by feedback-linearization control using a novel inverse dynamic model based on the force distribution algorithm

ABSTRACT

6-RSS Stewart-Gough parallel manipulator contains six crank-rod limbs connecting the base and moving platforms to each other, forming a 6DOF manipulator. In this paper, we introduce a novel decoupled inverse dynamic model for this manipulator based on the Force Distribution Algorithm. The performance of the proposed model was evaluated in tracking a complex trajectory (of multiple segments with simultaneous translational and rotational motions) using feedback-linearization control in the joint space and compared with that of the Lagrangian inverse dynamic model. Results showed that this model leads to a better performance in feedback-linearization control, especially when the reference trajectory is quantized, and with less calculation burden in comparison with the Lagrangian model. The control system employing both models showed robustness against payload uncertainty on the moving platform (150% of the moving platform’s mass). The performance assessment and the robustness approval were performed in simulation using a Simscape model specifically built for this purpose in the Simulink environment.     

On the determination of solutions of simultaneous Pell equations $$x^{2}-(a^{2}-1)y^{2}=y^{2}-pz^{2}=1$$ x 2 - ( a 2 - 1 ) y 2 = y 2 - p z 2 = 1

Periodica Mathematica Hungarica - In this paper, we consider the simultaneous Pell equations 0.1 $$\begin{aligned} x^{2}-(a^{2}-1)y^{2}= & {} 1, \nonumber \\ y^{2}-pz^{2}= & {} 1,...     

Basic sequences in some regular Köthe spaces

In this paper (closed, linear) subspaces of nuclear Köthe spaces are investigated. This has been the topic of various papers by E. Dubinsky, D. Vogt, M. Alpseymen etc. We give complete characterizations for subspaces with basis of unstable Köthe spaces of type D₁, in particular unstable L_f (Drafilev) spaces of type d₁, and regular subspaces of L_f spaces of infinite type without any assumptions on the defining exponent sequence. The method used depends on applying a stability theorem on embeddings of L. Schwartz [17] and the Hall-Koenig theorem [10] on selection of distinct representatives as well as some construction methods of E. Dubinsky [9].     

A study on thermal behaviors of mono ethyl ester azocalix[4]arene derivatives

In the present study, thermal stabilities of five new family of azocalix[4]arene mono ethyl ester derivatives, 4a–e, were investigated using thermogravimetry, differential thermogravimetry, and differential thermal analysis methods. It was found that all compounds showed thermal stability up to 236 °C averagely. After this temperature, decomposition of compounds starts gradually. The decomposition routes of 4a–c compounds are similar and occur with two stages. Ester alkyl groups decompose and remove from the structure in the first stage. Second stage corresponds to rest of structure decomposition. The decomposition routes of the 4d–e compounds are different from the decomposition routes of the 4a–c compounds. These compounds include halogen, and decomposition reactions realize with three and four stages respectively.     

Synthesis, spectral and thermal properties, and crystal structure of catena-poly-μ-ethylenediamine(dipicolinato)zinc(II) trihydrate, {[Zn(dipic)(μ-en)]·3H2O}n

A novel metal–organic coordination polymer framework formulated as {[Zn(dipic)(μ-en)]·3H₂O} _n (1) (catena-poly-μ-ethylenediamine(dipicolinato)zinc(II) trihydrate) has been synthesized and characterized by spectral method (IR), elemental analysis, thermal analysis (TG, DTG, DTA) and single crystal X-ray diffraction techniques. It crystallizes in the triclinic system, space group P−1. The asymmetric unit contains three hydrogen-bonded water molecules and the Zn atom is five-coordinated by three N and two O atoms. In fact, it is a new one-dimensional zinc complex with the peculiarity of having the ethylenediamine ligand very unusually acting as bridge to form polymeric chains. In the crystal structure, intramolecular O–H···O and intermolecular O–H···O and N–H···O hydrogen bonds result in the formation of a supramolecular structure, in which they seem to be effective in the stabilization of the structure.     

Synthesis of new benzothiazole derivatives bearing thiadiazole as monoamine oxidase inhibitors

Monoamine oxidases (MAO) are enzymes that catalyze the oxidative deamination of monoamines such as dopamine, noradrenaline, adrenaline, and serotonin. Recent studies have shown that numerous benzothiazole derivatives exhibit hMAO inhibitory activity in the micromolar concentration range. In this study, a novel series of benzothiazole-thiadiazole (5a-5l ) was synthesized and characterized their chemical structures by ¹H-NMR, ¹³C-NMR, and Mass spectroscopy. These compounds were evaluated as inhibitors for types A and B MAO enzymes. Compounds 5f and 5l were the most active derivatives in the series with an IC₅₀ values of 0.107 ± 0.003 and 0.128 ± 0.004, respectively. Furthermore, cytotoxicity of compounds 5f and 5l were investigated and found as non-cytotoxic.     

Controlling nonclassical content of clathrate hydrates through the choice of molecular guests and temperature

Low-temperature, low-pressure studies of clathrate hydrates (CHs) have revealed that small ether and other proton-acceptor guests greatly enhance rates of clathrate hydrate nucleation and growth; rapid formation and transformations are enabled at temperatures as low as 110 K, and cool moist vapors containing small ether molecules convert to mixed-gas CHs on a subsecond time scale. More recently, FTIR spectroscopic studies of the tetrahydrofuran (THF)-HCN double clathrate hydrate revealed a sizable frequency shift accompanied by a four-fold intensification of the C-N stretch-mode absorption of the small cage HCN, behavior that is enhanced by cooling and which correlates precisely with similar significant changes of the ether C-O/C-C stretch modes. These temperature-dependent correlated changes in the infrared spectra have been attributed to equilibrated extensive hydrogen bonding of neighboring large- and small-cage guest molecules with water molecules of the intervening wall. An ether guest functions as a proton acceptor, particularly so when complemented by the action of a proton-donor (HCN)/electron-acceptor (SO(2)) small-cage guest. Because guest molecules of the classic clathrate hydrates do not participate in hydrogen bonds with the host water, this H-bonding of guests has been labeled "nonclassical". The present study has been enriched by comparing observed FTIR spectra with high-level molecular orbital computational results for guests and hydrogen-bonded guest-water dimers. Vibrational frequency shifts, from heterodimerization of ethers and water, correlate well with the corresponding observed classical to nonclassical shifts. The new spectroscopic data reveal that the nonclassical structures can contribute at observable levels to CH infrared spectra for a remarkable range of temperatures and choice of guest molecules. By the choice of guest molecules, it is now possible to select the abundance levels of nonclassical configurations, ranging from ～0 to 100%, for a given temperature. This ability is expected to hasten understanding of the role of guest-induced nonclassical structures in the acceleration or inhibition of the rates of CH formation and transformation.     

One-dimensional coordination polymers of Co(II) and Cd(II)-squarate with 2-methylimidazole and 4(5)-methylimidazole ligands

Two new mixed-ligand coordination polymers, {[Co(μ_1,3-sq)(H₂O)₂(2-Meim)₂]·2(2-Meim)}_n (1) and [Cd(μ_1,3-sq)(H₂O)₂(4(5)-Meim)₂]_n (2), (sq = squarate, 2-Meim = 2-methylimidazole, 4(5)-Meim = 5-methylimidazole) have been synthesized and structurally characterized by X-ray crystallography. The spectral (IR and UV–Vis) and thermal analyses are also reported. The Co(II) and Cd(II) ions are distorted octahedrally coordinated by four oxygen atoms of two O¹–O³-bridging squarate ligands and two trans-aqua ligands, and by two nitrogen atoms of the trans-imidazole (2-Meim or 4(5)-Meim) ligands. The structures of 1 and 2 consist of one-dimensional chains of μ-1,3-squarato bridged metal(II) complex units. These chains are held together by hydrogen bonding interactions, forming three-dimensional framework.