Department of Electrical Engineering

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IIT Jodhpur

We show that the output beam exiting from the end facet of a single-mode–multimode–few-mode device can be designed to be a highly pure LG00 or LG01 mode. Our investigation provides a method to generate LG beams in free space using a low-cost, all-fiber solution that also shows potential for an integrated device. © 2021 Optical Society of America

Journal of the Optical Society of America B: Optical Physics

Generation of highly pure lower-order Laguerre–Gaussian radial beams using an all-fiber multimode interference method

Logic gates are designed using symmetric lateral doping-free bipolar junction transistor (BJT) on silicon on insulator (SOI) using differential pass transistor logic, and their performance matrices are presented. Charge carriers are induced in lightly doped emitter and collector regions using two unique approaches. i.e., the charge plasma (CP) and polarity control (PC). AND, OR and XOR gates are designed using four types of devices (CP-NPN, CP-PNP, PC-NPN, and PC-PNP) and transient and noise margin analysis are performed. The transient response shows rise and fall time less than 100 ps while worst-case noise margin of 0.25 V observed for an input voltage of 1 V. Moreover, 2:1 multiplexer is also designed and explored for output transient and voltage levels. The delay of less than 2.2 ns is achieved with a nominal deviation of 0.1 V and 0.04 V for high and low output levels respectively. © 2021 Elsevier Ltd

World University root node

Solid-State Electronics

Exploration of logic gates and multiplexer using doping-free bipolar junction transistor

Lowering the processing temperature is a crucial factor in the development of flexible electronic devices. Here we report the fabrication of high-performance OFETs based on room temperature deposited Ba0.5Sr0.5TiO3 (BST) as a high-k dielectric layer. The fabricated devices exhibited excellent performance while operating at a low voltage of -3 V along with demonstrating high operational stability when tested for 1 h bias stress and continuous transfer measurement cycles. In addition, inverter circuit performance is also investigated with these devices by connecting them to external loads. © 2021 IEEE.

FLEPS 2021 - IEEE International Conference on Flexible and Printable Sensors and Systems

Low Voltage Organic Field-Effect Transistors with Room Temperature Deposited Dielectric Layer

Arc welding is an indirectly controlled process where the electrical variables of arc are controlled to create joints of requisite mechanical and metallurgical characteristics after maintaining workable environment for the welder. Constant voltage arc types are mostly used in industry because they are energy efficient, more productive and welder friendly, these processes could be easily automated. However, the nature of arc types for CV processes appears drastically different for different metal transfer modes, input conditions, and process settings. The nonlinear arc itself poses as altogether different loads to power controller. Moreover, the process consists of several dynamic activities, each having different response time, their interaction with control variables add extra burden to controller. To simplify controller design, the input conditions of the process are defined in such a way that minimally defined two-input process could be controlled by controlling two independent dynamic activities. To meet that purpose with increased robustness this article proposes to use two independent easily implementable yet superior SOSM controllers—one for control of arc and another for control of wire feed speed. Robust control of wire feeding would reduce disturbance burden on the arc controller. The approach would be experimentally validated by practically designing both controllers along with creating requisite joints for wide range use suitable for ready-to-use in industrial applications. © 2021, Springer Nature Singapore Pte Ltd.

Studies in Systems, Decision and Control

Industry-Grade Robust Controller Design for Constant Voltage Arc Welding Process

A novel unknown input observer (UIO) using sliding modes is proposed for a general class of uncertain, nonlinear systems. The system generalization over-comes requirement of observability matching condition for the uncertainties and also does not rely on any transformation techniques, typically used for nonlinear systems. The UIO philosophy of disturbance decoupling is used for compensating the matched disturbances and overall robustness is engineered using sliding modes. Fault detection is proposed using the estimations. The efficacy of the method is illustrated through simulations on a quadruple tank process (QTP) plant. © 2021 IEEE.

IECON Proceedings (Industrial Electronics Conference)

Robust Unknown Input Observer for Uncertain Non-Linear Systems using Sliding Modes with Fault Detection

This brief introduces a practical sliding mode using state depended intermittent control strategy. Robust stabilization of the linear time-invariant system is achieved by rejecting the effect of matched and bounded input disturbances using the proposed state dependent intermittent sliding mode control (SDI-SMC). The system trajectories are driven to a predesigned practical sliding mode band by the proposed control to establish a practical sliding mode. The salient feature of the proposed control strategy is that the control is turned off whenever it is not necessary, which will result in a considerable saving in the control effort and other resources. The proposed SDI-SMC is simulated on the model of an industrial plant emulator and a detailed comparison is done with sliding mode control (SMC), event-triggered sliding mode control (ET-SMC) and adaptive sliding mode control (Adp-SMC). © 2004-2012 IEEE.

IEEE Transactions on Circuits and Systems II: Express Briefs

Practical Sliding Mode Using State Depended Intermittent Control

Typically, if the system is right-invertible only, then this implies that the number of inputs is more than that of outputs as well as states of the system. Over-actuated systems belong to such class. In this paper, a systematic design of a reduced-order super-twisting control is proposed to track arbitrary reference signals for uncertain non-minimum phase over-actuated systems. The proposed method involves the transformation that resolves the redundancy in the control inputs so that system can be represented as a normally-actuated system with virtual control inputs. Further, unstable zero dynamics are virtually stabilized through one more transformation so that stable and virtually stable zero dynamic states can be excluded from the super-twisting control design. Finally, the computed virtual control magnitude is spread across all the actuators via a redistributed pseud-inverse type of control allocation so that the system can be operated within the actuator saturation limits. © 2021 Elsevier Ltd

Automatica

Robust output tracking for the non-minimum phase over-actuated systems

This article aims to present a new formulation of the 'Linear Control' in sliding mode controller design. It is shown here that the linear control which is frequently augmented with the discontinuous control can be parameterized. The parameterized linear control provides flexibility in the total control law applied to the system and further the flexibility of the linear control is used to obtain the sliding mode control with less chattering magnitude and smaller controller gains. © 2021 IEEE.

2021 6th International Conference for Convergence in Technology, I2CT 2021

A New Formulation of Sliding Mode Control and its Applications

This paper proposes a sliding surface which renders the system dynamics to start directly from itself without a reaching phase. More specifically, the system dynamics is insensitive to matched disturbances/uncertainties throughout the entire system response. The controller design based on reduced-order subsystem is still preserved. It is different from integral sliding mode in which the design is based on the full order of the system to reach the same objective. The simulation results of its application to a fractional inverted pendulum system is demonstrated. © 2019 Chinese Automatic Control Society and John Wiley & Sons Australia, Ltd

Fulltext

Asian Journal of Control

Sliding mode control of uncertain fractional-order systems: A reaching phase free approach

The visualization of band alignment for designing heterostructures between transition metal dichalcogenides and germanium plays a vital role in a deeper understanding of carrier dynamics at the heterointerface. Here, to study the band alignment across the MoS2/Ge heterojunction, we have deposited a wafer-scale highly crystalline few atomic layers MoS2 film via a highly controllable and scalable sputtering technique coupled with a post sulfurization process in a sulfur-rich environment. The Raman and XRD spectra of as-fabricated MoS2/Ge heterojunction expose the presence of highly crystalline few atomic layer MoS2 on top of Ge substrate. Interestingly, we found a type-II band alignment at the MoS2/Ge heterointerface having valence band, and conduction band offset values of 0.88 and 0.21 eV, which can provide very efficient recombination through spatially confining charge carriers. The calculation of band offset parameters offers a promising way for device engineering across the MoS2/Ge heterojunction interface. Moreover, to demonstrate the practicability of the fabricated heterostructure, we explored the suitability of our device for broadband photodetection applications. © 2021 IOP Publishing Ltd.