Adaptive terminal sliding mode control for rigid robotic manipulators

In order to apply the terminal sliding mode control to robot manipulators, prior knowledge of the exact upper bound of parameter uncertainties, and external disturbances is necessary. However, this bound will not be easily determined because of the complexity and unpredictability of the structure of uncertainties in the dynamics of the robot. To resolve this problem in robot control, we propose a new robust adaptive terminal sliding mode control for tracking problems in robotic manipulators. By applying this adaptive controller, prior knowledge is not required because the controller is able to estimate the upper bound of uncertainties and disturbances. Also, the proposed controller can eliminate the chattering effect without losing the robustness property. The stability of the control algorithm can be easily verified by using Lyapunov theory. The proposed controller is tested in simulation on a two-degree-of-freedom robot to prove its effectiveness.     

Can LDH activity in spermatic vein indicate testicular damage? A preliminary report

Extradural drainage systems connected to a vacuum device for preventing postoperative haematoma formation are often used in neurosurgical practice. Cardiovascular complications, including bradycardia or low arterial pressure caused by intracranial hypotension, have been described associated with their use. We have investigated the relationship between the negative pressure applied to extradural drainage systems and intracranial pressure (ICP), and analysed the effects of negative pressure of the drains on systolic (SAP), diastolic (DAP) and mean (MAP) arterial pressures and on heart rate (HR). We studied prospectively 15 patients undergoing neurosurgery for supratentorial tumours or aneurysms. Transient decreases in ICP (P < 0.001) and HR (P < 0.001), with no clinical effects, were observed after connecting the vacuum device to the drain. There were no significant changes in SAP, DAP or MAP.     

A novel design procedure for tractor clutch fingers by using optimization and response surface methods

This paper presents a methodology for re-designing a failed tractor transmission component subjected to cyclic loading. Unlike other vehicles, tractors cope with tough working conditions. Thus, it is necessary to re-design components by using modern optimization techniques. To extend their service life, we present a design methodology for a failed tractor clutch power take-off finger. The finger was completely re-designed using topology and shape optimization approach. Stress-life based fatigue analyses were performed. Shape optimization and response surface methodology were conducted to obtain optimum dimensions of the finger. Two design parameters were selected for the design of experiment method and 15 cases were analyzed. By using design of the experiment method, three responses were obtained: Maximum stresses, mass, and displacement depending on the selected the design parameters. After solving the optimization problem, we achieved a maximum stress and mass reduction of 14% and 6%, respectively. The stiffness was improved up to 31.6% compared to the initial design.     

Robust adaptive control for mobile manipulators

This paper addresses the trajectory tracking control of a nonholonomic wheeled mobile manipulator with parameter uncertainties and disturbances. The proposed algorithm adopts a robust adaptive control strategy where parametric uncertainties are compensated by adaptive update techniques and the disturbances are suppressed. A kinematic controller is first designed to make the robot follow a desired end-effector and platform trajectories in task space coordinates simultaneously. Then, an adaptive control scheme is proposed, which ensures that the trajectories are accurately tracked even in the presence of external disturbances and uncertainties. The system stability and the convergence of tracking errors to zero are rigorously proven using Lyapunov theory. Simulations results are given to illustrate the effectiveness of the proposed robust adaptive control law in comparison with a sliding mode controller.     

Progressive fatigue failure behavior of glass/epoxy (±75)2 filament-wound pipes under pure internal pressure

Fatigue failure behaviors of filament-wound composite pipes under pure internal pressure were investigated. The filament-wound pipes are made of E-glass/epoxy and have four layers which have ±75° winding angle. The fatigue tests have been done in accordance with ASTM D-2992, which stipulate 0.42 Hz frequency and R = 0.05 stress ratio. Tests have been performed at different load levels from 30% to 70% of ultimate tangential strength of the pipe, the damage progression such as whitening, leakage and final failure have been observed, and S–N curves of these damages were obtained.     

Thermal Conductivity Variation with Temperature for Lead-Free Ternary Eutectic Solders

The variations of the thermal conductivity with temperature for the lead-free ternary eutectic solders Bi-42.73 wt.%Sn-1.03 wt.%Ag (Bi-Sn-Ag), Sn-3.5 wt.%Ag-0.9 wt.%Cu (Sn-Ag-Cu), Sn-6 wt.%Sb-5 wt.%Ag (Sn-Sb-Ag), Sn-42.8 wt.%Bi-0.04 wt.%Cu (Sn-Bi-Cu), and In-48.4 wt.%Sn-2.31 wt.%Ag (In-Sn-Ag) were measured using a linear heat flow apparatus. It was observed that the thermal conductivities of solid phases for the Bi-Sn-Ag, Sn-Ag-Cu, Sn-Sb-Ag, Sn-Bi-Cu, and In-Sn-Ag solders decrease linearly with increasing temperature. The thermal conductivities of the Bi-Sn-Ag, Sn-Ag-Cu, Sn-Sb-Ag, Sn-Bi-Cu, and In-Sn-Ag solders at their melting temperature were obtained as 17.89 ± 1.6 W/K-m, 49.89 ± 4.5 W/K-m, 41.96 ± 3.8 W/K-m, 20.03 ± 1.8 W/K-m, and 70.21 ± 6.3 W/K-m, respectively. The thermal temperature coefficients for the Bi-Sn-Ag, Sn-Ag-Cu, Sn-Sb-Ag, Sn-Bi-Cu, and In-Sn-Ag solders were also determined to be ?2.894 × 10^?3 K^?1, ?0.907 × 10^?3 K^?1, ?1.246 × 10^?3 K^?1, ?2.638 × 10^?3 K^?1, and ?1.250 × 10^?3 K^?1, respectively, from plots of thermal conductivity versus temperature.     

Investigation of the effects of different heat treatment parameters on the corrosion and mechanical properties of the AlSi10Mg alloy produced with direct metal laser sintering

In this study, AlSi10Mg samples produced by the direct metal laser sintering (DMLS) method were applied to heat treatment with different parameters (stress relief and T6). Heat-treated and as-built samples were subjected to intergranular corrosion test according to BS EN ISO 11846 standard. Hardness, tensile, electrical conductivity, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and weight loss tests were applied to the samples. The corrosion, electrical conductivity, and mechanical properties of the DMLS-AlSi10Mg material were investigated in detail depending on the heat-treatment parameters.     

Fatty acid composition in some wild edible mushrooms growing in the middle Black Sea region of Turkey

The fatty acids in Agaricus bisporus, Agaricus campestris, Boletus edulis, Coprinus comatus, Pleurotus ostreatus, Oudemansiella radicata and Armillaria mellea species were obtained by a Soxtec system extracted with chloroform/methanol (2:1) and derivation of their methyl ester forms. The fatty acids were identified and quantified by gas chromatography. The fatty acid compositions mushrooms were studied using fruit body and stems. Fatty acid composition varied among species. The dominant fatty acid in fruit body and stem of all mushroom species was linoleic acid (18:2). Percentage of linoleic acid in species varied from 13% to 59%. Linoleic acid levels were higher in the stem of O. radicata than in the stems of other mushroom species. The other major fatty acids were, respectively, palmitic, oleic, stearic and arachidic acids. Linolenic acid levels were low in all species. Fatty acids analysis of the mushrooms showed that the unsaturated fatty acids were at higher concentrations than saturated fatty acids.     

The Experimental Determination of Interfacial Energies for Solid Cd in Equilibrium with Sn-Cd-Sb Liquid

The equilibrated grain boundary groove shapes of solid Cd in equilibrium with Sn-Cd-Sb liquid were observed from a quenched sample by using a radial heat flow apparatus. The Gibbs–Thomson coefficient, solid–liquid interfacial energy, and grain boundary energy of the solid Cd were determined from the observed grain boundary groove shapes. The thermal conductivity of the eutectic solid phase for Sn-35.80 at. pct Cd-6.71 at. pct Sb alloy and the thermal conductivity ratio of the liquid phase to the solid phase for Sn-35.80 at. pct Cd-6.71 at. pct Sb alloy at eutectic temperature were also measured with a radial heat flow apparatus and a Bridgman-type growth apparatus, respectively.     

Exergetic Analysis of Textile Convective Drying with Stenters by Subsystem Models: Part 2—Parametric Study on Exergy Analysis

In this study, the effects of exhaust air humidity ratio, the residual moisture content of fabric outlet, and the temperature of the drying air on the exergy destruction and efficiency of stenters were investigated. The exergy efficiencies of the direct gas heated stenter (DGHS) and hot oil heated stenter (HOHS) were calculated to be varying from 8.5 to 17.5% and from 6.8 to 14.0%, depending on the exhaust air humidity ratio, respectively. The increase in the drying air temperature led to an increase in the exergy efficiency, especially in the constant rate and second rate period of the drying. On the other hand, the application of the gradual temperature method caused the highest total exergy efficiency due to the highest drying rates in the first chambers where considerably high air temperatures were set. Overdrying resulted in the higher irreversibility due to the increase in the fuel consumption in the falling rate period of drying. Thus, the exergy efficiency decreased drastically.