Dynamical adaptive integral backstepping variable structure controller design for uncertain systems and experimental application

In this study, a dynamical adaptive integral backstepping variable structure control (DAIBVSC) system based on the Lyapunov stability theorem is proposed for the trajectory tracking control of a nonlinear uncertain mechatronic system with disturbances. In this control scheme, no prior knowledge is required on the uncertain parameters and disturbances because it is estimated by two types of dynamical adaptive laws. These adaptive laws are integrated into the dynamical adaptive integral backstepping control and variable structure control (VSC) parts of the DAIBVSC. The dynamical adaptive law in the dynamical adaptive integral backstepping control part updates parametric uncertainties, while the other in the VSC part adapts upper bounds of non‐parametric uncertainties and disturbances. In order to achieve a more robust output tracking and better parameter adaptation, the control system is extended by one integrator and sliding surface is augmented by an integral action. Experimental evaluation of the DAIBVSC is conducted with respect to performance and robustness to parametric uncertainties. Experimental results of the DAIBVSC are compared with those of a traditional VSC. The proposed DAIBVSC exhibits satisfactory output tracking performance, good estimation of the uncertain parameters and can reject disturbances with a chattering free control law. Copyright © 2017 John Wiley & Sons, Ltd.     

Sliding mode PI control with backstepping approach for MIMO nonlinear cross‐coupled tank systems

The control of tank systems in industrial applications is an important issue for monitoring the chemical processes involved in the manufacture and delivery of product. The most important reason to control the tank systems is to keep the liquid level in the tanks constant and at the desired level for a specified period of time. In this study, the sliding mode control (SMC) with a repetitive approach called backstepping that is insensitive to uncertainties in system parameters and input disturbances is proposed and experimentally applied to a quadruple, cross‐coupled, uncertain, nonlinear, and multiple‐input/multiple‐output tank system. A proportional‐integral (PI) control is used to reduce the steady‐state error caused by the parameter variations and external noises. The traditional way of introducing PI usually leads to sliding surfaces. In this paper, the PI action is introduced to the control signal. The proposed backstepping sliding mode PI control (BSMPIC) is applied to such a complex tank system for the first time. The experimental results are compared with those of the SMC, sliding mode PI control, and backstepping sliding mode control to see the effect of the proposed BSMPIC on the system. As a result of the comparison, it is observed that less overshoot and tracking error, better tracking performance, and faster rise time in the transient regime is obtained by the BSMPIC.     

Hydrogenolysis and hydrocracking of the carbonoxygen bond. 3. Thermolysis in tetralin of substituted anisoles

Mild pyrolysis and hydrogenolysis products of coal contain substantial amounts of pyrocatechol and resorcinol and their homologues whereas hydroquinone and its homologues are absent or present in only low amounts. In the present work the model compounds anisole and methyl-, methoxy- or hydroxy-substituted anisoles were studied to elucidate substituent effects on the carbon—oxygen bond cleavage in the presence of tetralin. The experiments were carried out at 618 K and 6 MPa (H₂). The major reaction is demethylation to the corresponding phenols. A steric effect can be seen in the ortho compounds and an electronic effect when the substituent is a strongly electron-releasing group. In compounds with oxygen substituents para to each other little or no hydroquinone can be isolated whereas the ortho and meta compounds, respectively, give pyrocatechol and resorcinol. It is suggested that the low yield or absence of hydroquinone in this work and in coal pyrolysis is due to the high reactivity of the intermediate p-hydroxyphenoxy radical, which gives rise to adducts and other compounds of high molar mass. The ortho radical is sterically hindered and the meta radical has a lower reactivity and are hence abstracting hydrogen from the hydrogen donor or coal.     

Multi‐scroll chaotic attractors from a generalized time‐delay sampled‐data system

In this paper, the first generalization for time‐delay sampled‐data chaotic system in order to generate multi‐scroll attractor is introduced with its circuit implementation. An efficient delay‐line with binary priority encoding, parallel shifting, and binary decoding is also suggested and implemented to overcome the delay line realization drawback in such systems. The proposed system enhances the complexity of chaotic behavior by means of multi‐scroll feature and exemplifies the simplification of chaotic systems for better realizations. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of functionalized PET fibers by grafting and modification and their application for Cr(VI) ion removal

A new fiber adsorbent for removing Cr(VI) ions from aqueous solution was prepared by grafting and modification. The grafted fiber and modified fiber were characterized by SEM, FTIR, and TGA. FTIR analysis indicated that acrylonitrile monomer was grafted onto the PET surface and that new groups were present on the surface after the modification. Scanning electron microscopy showed that the PET fiber was wider after grafting and especially modification. The TGA results showed that the degradation steps and the thermal behavior of the PET fiber changed after modification. The effects of the pH, ion concentration, and temperature on the amount of Cr(VI) adsorbed were investigated. The fiber showed its maximum adsorption capacity in acidic medium. Isotherm studies indicated that the experimental results were best fitted to the Langmuir isotherm. The adsorption capacity of the modified fiber was found to be 25.77, 38.17, and 44.84 mg/g fiber at 25, 35, and 45 °C, respectively. Kinetic results indicated that the adsorption of Cr(VI) onto the modified fiber followed a pseudo-second-order kinetic model. Calculated thermodynamic parameters demonstrated that the adsorption of Cr(VI) ions on the modified fiber is an endothermic, feasible, and spontaneous process.     

Design and implementation of an Internet based effective controlling and monitoring system with wireless fieldbus communications technologies for process automation--an experimental study

The network requirements of control systems in industrial applications increase day by day. The Internet based control system and various fieldbus systems have been designed in order to meet these requirements. This paper describes an Internet based control system with wireless fieldbus communication designed for distributed processes. The system was implemented as an experimental setup in a laboratory. In industrial facilities, the process control layer and the distance connection of the distributed control devices in the lowest levels of the industrial production environment are provided with fieldbus networks. In this paper, the Internet based control system that will be able to meet the system requirements with a new-generation communication structure, which is called wired/wireless hybrid system, has been designed on field level and carried out to cover all sectors of distributed automation, from process control, to distributed input/output (I/O). The system has been accomplished by hardware structure with a programmable logic controller (PLC), a communication processor (CP) module, two industrial wireless modules and a distributed I/O module, Motor Protection Package (MPP) and software structure with WinCC flexible program used for the screen of Scada (Supervisory Control And Data Acquisition), SIMATIC MANAGER package program ("STEP7") used for the hardware and network configuration and also for downloading control program to PLC.     

Spectrophotometric determination of low levels arsenic species in beverages after ion-pairing vortex-assisted cloud-point extraction with acridine red

A new, low-cost, micellar-sensitive and selective spectrophotometric method was developed for the determination of inorganic arsenic (As) species in beverage samples. Vortex-assisted cloud-point extraction (VA-CPE) was used for the efficient pre-concentration of As(V) in the selected samples. The method is based on selective and sensitive ion-pairing of As(V) with acridine red (ARH⁺) in the presence of pyrogallol and sequential extraction into the micellar phase of Triton X-45 at pH 6.0. Under the optimised conditions, the calibration curve was highly linear in the range of 0.8–280 µg l^?1 for As(V). The limits of detection and quantification of the method were 0.25 and 0.83 µg l^?1, respectively. The method was successfully applied to the determination of trace As in the pre-treated and digested samples under microwave and ultrasonic power. As(V) and total As levels in the samples were spectrophotometrically determined after pre-concentration with VA-CPE at 494 nm before and after oxidation with acidic KMnO₄. The As(III) levels were calculated from the difference between As(V) and total As levels. The accuracy of the method was demonstrated by analysis of two certified reference materials (CRMs) where the measured values for As were statistically within the 95% confidence limit for the certified values.     

Stability Analysis of MIMO Microgrid Systems in d–q Axis Platform with Constant Power Loads Based on Popov Absolute Stability Criterion

Microgrid has several advantages over the conventional utility grid system, thus naturally being the gateway to implement the renewable energy resources. Now it is considered as the primary solution to solve the next generation power demand. However, in practice, it is very challenging to retain the microgrid operational stability due to the dense presence of constant power loads in the system. In this article, we considered a technique of compensating the load side to mitigate the instability issues introduced by CPL. Adopting this technique, a stability analysis was presented here for MIMO (multiple input, multiple output) AC microgrid system in dq axis platform by Popov Absolute Stability Criterion using the sector conditions and Popov plots. Besides the recent researches regarding the microgrid stability techniques and the previous analysis using Popov Absolute Stability Criterion, the modeling of the energy storage-based load side compensated microgrid system is also provided in this article. All the cases and results are rigorously scrutinized in virtual platform such as MATLAB/Simulink and verified through experimental results as well.     

Fire resistance of geopolymer concrete produced from Elazığ ferrochrome slag

This paper presents the effect of elevated temperatures up to 700 °C on compressive strength and water absorption of two alkali‐activated aluminosilicate composites (one of them is river sand aggregate geopolymer concrete; the other one is crushed sand aggregate geopolymer concrete) and ordinary Portland cement based concretes. To obtain binding geopolymer material, Elaz?? ferrochrome slag was ground as fine as cement, and then it was alkali activated with chemical (NaOH and Na₂SiO₃). Geopolymer concrete samples were produced by mixing this binding geopolymer material with aggregates. At each target temperature, concrete samples were exposed to fire for the duration of 1 h. Fire resistance and water absorption of geopolymer and ordinary Portland cement concrete samples were determined experimentally. Experimental results indicated that compressive strength of geopolymer concrete samples increased at 100 °C and 300 °C temperatures when compared with unexposed samples. In geopolymer concrete samples, the highest compressive strength was obtained from river aggregates ones at 300 °C with 37.06 MPa. Water absorption of geopolymer concrete samples increased at 700 °C temperature when compared with unexposed samples. However, a slight decrease in water absorption of concrete samples was observed up to 300 °C when compared with unexposed samples. SEM and X‐ray diffraction tests were also carried out to investigate microstructure and mineralogical changes during thermal exposure. Copyright © 2016 John Wiley & Sons, Ltd.