Department of Electrical Engineering

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IIT Jodhpur

Event-triggered sliding mode control (SMC) achieves robust performance in the presence of external disturbances. However, this triggering scheme for SMC does not have a global property even for linear time-invariant systems. Here, 'global' means that the triggering scheme ensures the stability of the system globally in the state space. Therefore, in this brief, a global event-triggering realization of SMC is proposed. In this proposed scheme, it is established that the system trajectory is attracted toward the sliding manifold and remains within a band thereafter in the presence of uncertainties. The simulation result is given to show the effectiveness of the result. © 2004-2012 IEEE.

World University root node

IEEE Transactions on Circuits and Systems II: Express Briefs

Robust sliding mode control: An event-triggering approach

We demonstrate an all-fiber multimode interference device for achieving controlled and repeatable mode launching condition in a few mode fiber. The device is easy to design, quick to customize, and require bare minimum equipments for fabrication. © OSA 2017.

Optics InfoBase Conference Papers

Multimode interference based all-fiber selective mode launcher for few mode fiber applications

In this paper, three Lorentzian based robust adaptive algorithms are proposed for identifying systems in presence of impulsive noise. The first algorithm called Lorentzian adaptive filtering (LAF) is derived from a sliding window type cost function with Lorentzian norm of past errors to combat adverse effect of impulsive noise on systems. The first and second order convergence analyses of the LAF algorithm are carried out in this paper. Then, to identify sparse systems in impulsive noise environment,l0 norm penalty is introduced to the cost function of the LAF algorithm leading to a new algorithm called Lorentzian hard thresholding adaptive filtering (LHTAF) which employs hard thresholding operator with a fixed hard thresholding parameter to obtain sparse solutions. The effect of the hard thresholding operator is further analyzed, and the analysis shows that a variable hard thresholding parameter offers significant improvement in the performance of the algorithm, and this result in the final algorithm called Lorentzian variable hard thresholding adaptive filtering (LVHTAF) where the hard thresholding parameter is adjusted adaptively. Simulation results show that the LVTHAF outperforms the existing robust sparse adaptive algorithms by producing lesser steady state mean square error. © 2004-2012 IEEE.

IEEE Transactions on Circuits and Systems I: Regular Papers

Lorentzian Based Adaptive Filters for Impulsive Noise Environments

In this paper we have proposed new physics based analytical models for transport and flicker noise in field effect transistors (FETs) working in the quasi-ballistic regime. The model is capable of accurately predicting the device current and low frequency flicker noise power spectral density for all drain and gate biases and includes short channel effects. It takes length scaling into account and can be used for the full range of devices starting from complete drift-diffusive to completely ballistic. This is the first time an analytical model of flicker noise for quasi-ballistic devices is being presented. The model is generic and can be used for any device geometry and construction. The model has been verified with experimental data from literature. © 2016 IEEE.

2016 3rd International Conference on Emerging Electronics, ICEE 2016

Modeling of flicker noise in quasi-ballistic devices

In this paper, a planar substrate integrated waveguide (SIW) cavity backed slot antenna for wideband application is presented. The proposed antenna uses SIW cavity hybrid modes to realize the wideband response which are excited by long bow tie shaped slot antenna loading at the top plate of the cavity. To excite more than two hybrid modes in the proposed design, an additional SIW cavity is placed and excited through an aperture in the common sidewall between them. As a result, three hybrid modes are excited in the design which excite the slots to radiate with wideband response. The proposed antenna is fed by simple microstrip line and exhibits a bandwidth of 1.56 GHz (15.6%) covering X-band Radio navigation, Radio location applications while maintaining unidirectional radiation pattern and a gain above 4.1 dBi throughout the operating bandwidth of the antenna. The fabricated prototype of the antenna is implemented in a thin substrate (height ∼ 0.026λ0) which makes it attractive for conformal applications. © 2016 IEEE.

Asia-Pacific Microwave Conference Proceedings, APMC

Design of SIW cavity backed slot antenna for wideband application

This paper presents a multivariable state feedback tracking control with integral sliding mode which can achieve the output tracking of a reference step signal without any overshoot by rejecting the disturbances. The control designed is able to completely reject the matched-bounded disturbances by using the integral sliding mode technique. The multivariable feedback controller is capable of achieving arbitrarily small rise time without any overshoot for square multivariable system under some mild assumptions. The proposed control is verified using a numerical example of quadruple-tank setup. © 2017 IEEE.

Proceedings IECON 2017 - 43rd Annual Conference of the IEEE Industrial Electronics Society

Robust nonovershooting tracking control for linear multivariable systems

Photo-response of solution processed flexible TIPS-pentacene organic field-effect transistors is evaluated under illumination with visible light of red, green, and blue colors having minimum wavelengths of 620, 520, and 460 nm. For - 10 V operation, pristine photo-OFETs exhibited average field-effect mobility of 0.11 cm V s, near zero threshold voltage, and current ON-OFF ratio of ∼10. These photo-OFETs exhibited prevalent photovoltaic characteristics with shift in the threshold voltage upon illumination, which was found to increase with rising intensity, illumination time, and gate bias during illumination. For low-voltage operation at - 5 V, maximum current modulation of 4 × 10 and 10, and photo-responsivity of 17 mA/W and 35 mA/W, respectively, were achieved for blue (intensity of 1.7 mW/cm) and green (intensity of 0.4 mW/cm) light illuminations. However, these photo-OFETs did not show significant response to red light. A fast dynamic response to periodic pulses of illumination was also observed. For a gate bias of +10 V and illumination time of 500 s, maximum current modulation of 10 was achieved for blue light illumination. © 2017 IEEE.

IEEE Sensors Journal

Photo-response of low voltage flexible tips-pentacene organic field-effect transistors

Perovskite LaFeO3 is regarded as one of the promising photocatalysts for solar splitting of water to hydrogen and oxygen due to its suitable band edge positions, visible light absorbance, and high chemical stability. To further improve its photocatalytic performance of LaFeO3, the effects of solute concentration in the KCl-flux growth and partial A– and B–site substitution are investigated in this work. Controlling the solute concentration in the range of 1–20 mol% is crucial to grow phase-pure LaFeO3 crystals with idiomorphic shape. With increasing the solute concentration, the flux-based growth route gradually changes to a solid state-based growth route because of a decrease in solubility and an increase in the crystallization core number. The La1−xSrxFe1−yTiyO3 (x,y = 0,0; 0,0.15; 0.15,0; 0.1125,0.0375; 0.0375,0.1125; and 0.075,0.075) crystals were also synthesized by a KCl-flux method to explore the effect of partial Sr2+-to-La3+ and/or Ti4+-to-Fe2−4+ substitution on photocatalytic performance of LaFeO3. The Sr2+–Ti4+ co-substitution is found to enhance the photocatalytic performance of LaFeO3 as compared with the corresponding individual substitution (Sr2+ or Ti4+). The highest photocatalytic hydrogen generation rate (83.2 μmol h−1) was observed for Pt-photodeposited La0.925Sr0.075Fe0.925Ti0.075O3 crystals in 5-h reaction due to the improvement of both bulk properties and photoactivity and the reduction in both grain boundaries and lattice defects stemmed from the Sr2+–Ti4+ co-substitution and KCl flux growth. © 2017 Hydrogen Energy Publications LLC

International Journal of Hydrogen Energy

Engaging the flux-grown La1−xSrxFe1−yTiyO3 crystals in visible-light-driven photocatalytic hydrogen generation

Two-dimensional materials have gained considerable attention in chemical sensing owing to their naturally high surface-to-volume ratio. However, the poor response time and incomplete recovery at room temperature restrict their application in high-performance practical gas sensors. Herein, we demonstrate ultrafast detection and reversible MoS2 gas sensor at room temperature. The sensor's performance is investigated to NO2 at room temperature, under thermal and photo energy. Incomplete recovery and high response time of ∼249 s of sensor are observed at room temperature. Thermal energy is enough to complete recovery, but it is at the expense of sensitivity. Further, under photo excitation, MoS2 exhibits an enhancement in sensitivity with ultrafast response time of ∼29 s and excellent recovery to NO2 (100 ppm) at room temperature. This significant improvement in sensitivity (∼30%) and response time (∼88%) is attributed to the charge perturbation on the surface of the sensing layer in the context of NO2/MoS2 interaction under optical illumination. Moreover, the sensor shows reliable selectivity toward NO2 against various other gases. These unprecedented results reveal the potential of 2D MoS2 to develop a low power portable gas sensor. © 2017 American Chemical Society.

ACS Sensors

UV-Activated MoS2 Based Fast and Reversible NO2 Sensor at Room Temperature

The exceedingly fragile nature of thermally grown Au-black coating makes handling and patterning a critical issue. Infrared absorption characteristics of near atmospheric, N2 ambient DC sputtered Au thin films are studied for this purpose. The thin Au films are sputtered at different chamber pressures in Ar and N2/Ar gas ambient from 4.5 to 8.0 mbar and optimized for enhanced infrared absorption. The absorber film sputtered in N2/Ar ambient at 8.0 mbar chamber pressure offers significant absorption of medium to long wave infrared radiations. The micro-patterning of sputtered Au thin film is carried out by using conventional photolithography and metal lift off methods on a prefabricated µ-infrared detector array on Si (1 0 0) substrate. The steady state temperature response of sputtered film has been examined using nondestructive thermal imaging method under external heating of the detector array. © 2017