Department of Electrical Engineering

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IIT Jodhpur

We enhance the capability of industry standard compact model BSIM6 to model the parasitic current Iedge at the shallow trench isolation edge. Accurate, efficient, and scalable model for Iedge is developed by finding the key differences between Iedge and main device drain current (Imain). It is found that Iedge has a different sub-threshold slope, body-bias coefficient, and short-channel behavior as compared to Imain. These important effects along with their dependencies on device geometry, bias conditions, and temperature are accounted for in the model. The model is in excellent agreement with experimental data verifying its scalability and readiness for production level usage. © 2015 IEEE.

World University root node

IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems

Modeling STI Edge Parasitic Current for Accurate Circuit Simulations

DC microgrid consists of cascaded power converters in which the constant power load behaviour of point-of-load converters poses challenging stability issues even if individual converters are stable. In this paper, a robust sliding mode controller has been proposed for DC/DC bidirectional buck-boost converter interfacing storage unit in an islanded DC microgrid environment. The controller is designed to ensure DC bus voltage regulation in the presence of renewable energy source and predominantly constant power loads. The performance of the proposed controller is validated through real-time simulation conducted using OPAL-RT® Digital Simulator. The controller ensures DC bus voltage regulation within tight limits and is robust with respect to wide variations in the renewable energy source power and the load. © 2015 IEEE.

2015 IEEE 1st International Conference on Direct Current Microgrids, ICDCM 2015

Sliding mode control of a bidirectional DC/DC converter with constant power load

In this paper, two approaches based on sliding mode control for controlling a single-stage grid-connected three-phase solar photovoltaic system have been presented. The sliding mode control is robust and has good disturbance rejection as compared to the conventional proportional-integral control. Another advantage is that feedback linearization is not required for controlling nonlinear systems. There are two controlled variables namely the dc-link voltage and the q-axis component of the line current of the Voltage Source Converter. In the first approach, twisting controller and first order sliding mode controller have been used. Super twisting controller has been used to control both the variables in the second approach. The propsed control scheme has been simulated to verify the results. © 2015 IEEE.

IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society

Control of single-stage grid-connected three-phase solar photovoltaic system using sliding mode control

In this paper, we discuss event-triggering scheme with sliding mode control where sensors are distributed over network. Here, a decentralized event-triggering mechanism is proposed where event is observed at each sensor nodes with local information for possible triggering and control update is done whenever a centralized event is triggered. In order to achieve this, the states are sampled at any one of the local triggering instant and then a centralized triggering condition is evaluated for possible control update. The utility of the scheme is analysed through a numerical simulation. © 2015 IEEE.

2015 10th Asian Control Conference: Emerging Control Techniques for a Sustainable World, ASCC 2015

Decentralized event-triggered sliding mode control

The paper presents a generalized algorithm for the reaching and boundedness of the sliding variable in case of discrete time sliding mode control systems. The algorithm is general as it not only comprises functions in the sliding variable, but also functions in other variables, which are known. With the help of the proposed generalized reaching law, an important problem of a reaching law with uncertainty bounded by known functions is studied. The convergence of the sliding variable to an ultimate bounding function in presence of such an uncertainty is shown by the band approach method. This is achieved by appropriately selecting the functions in the proposed generalized reaching law. © 2014 Elsevier. Ltd All rights reserved.

Automatica

A generalized reaching law for discrete time sliding mode control

This paper proposes the application of a new algorithm for the position control of a Stewart platform. The conventional integral sliding mode controller is a combination of nominal control and discontinuous feedback control hence the overall control is discontinuous in nature. The discontinuity in the feedback control is undesirable for practical applications due to chattering which causes the wear and tear of the mechanical actuators. In this paper the existing integral sliding mode control law for systems with matched disturbances is modified by replacing the discontinuous part by a continuous modified twisting control. This proposed controller is continuous in nature due to the combinations of two continuous controls. The desired position of the platform has been achieved using the proposed controller even in the presence of matched disturbances. The effectiveness of the proposed controller has been proved with the simulation results. © 2015 ISA.

ISA Transactions

Smooth integral sliding mode controller for the position control of Stewart platform

Quality control is the key issue that needs to be addressed in any gas metal arc welding (GMAW) system, especially in robotic pipeline welding system. This paper explores a second-order sliding mode control (SMC) strategy - a variable gain super-twisting control, to maximize the productivity, consistency in welding quality. This is achieved by the robust finite time output tracking of GMAW system. A nonlinear multi-input multi-output (MIMO) model of GMAW system has been considered here for the design of variable gain super-twisting (VGST) controller by which complete rejection of the bounded uncertainties/disturbances is possible and the adaptive characteristic of its gains help to use the control effort effectively. The stability of internal dynamics of the system is studied to establish the feasibility of solving the robust finite time output tracking problem. The stability of the overall system has been analyzed using Lyapunov stability criterion. The performance of the controller is demonstrated using the model of the system emulating the realistic conditions of operation. The simulation results are presented to illustrate the efficacy of the controller. Copyright © 2015 by ASME.

Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME

Variable gain super-twisting control of GMAW process for pipeline welding

The paper deals with the output stabilization of the system in the presence of unmatched uncertainties using higher order sliding mode control. Super twisting control is used to achieve second order sliding mode on the defined sliding surface. Here a sliding surface is proposed based on the information of output and observed states. Higher order sliding mode observer (HOSMO) is used to observe the states of the system. The gains of the observer are chosen in such a way that the output error goes to zero very fast before the sliding mode is enforced into the system. During this the HOSMO estimates the unmatched disturbance exactly. It is shown that once the sliding mode is established thereafter the reduced order dynamics is unaffected by unmatched uncertainties. The performance of the proposed technique is validated in the simulation and the results are very promising. © 2015 IEEE.

Output stabilization of the system with mismatched uncertainties using higher order sliding mode approach

The room temperature ferromagnetic behavior of InN nanostructures grown by molecular beam epitaxy (MBE) is explored by means of magnetization measurements. The saturation magnetization and remanent magnetization are found to be strongly dependent on the size of the nanostructures. This suggests that the ferromagnetism is essentially confined to the surface of the nanostructures due to the possible defects. Raman spectroscopy shows the existence of indium vacancies which could be the source of ferromagnetic ordering in InN nanostructures. Copyright © 2015 American Scientific Publishers.

Journal of Nanoscience and Nanotechnology

Observation of room temperature ferromagnetism in inN nanostructures

Vertically well aligned ZnO nanorods (NRs) were grown on Si(100) substrate using RF magnetron sputtering technique. Scanning electron microscopy images confirms uniform distribution of NRs on 2 in. wafer with average diameter, height and density being ∼75 nm, ∼850 nm, and ∼1.5 × 1010 cm-2, respectively. X-ray diffraction reveals that the ZnO NRs are grown along c-axis direction with wurtzite crystal structure. Cathodoluminescence spectroscopy, which shows a single strong peak around 3.24 eV with full width half maxima 130 meV, indicates the high crystalline and optical quality of ZnO and very low defect density. Vertically aligned nanosensors were fabricated by depositing gold circular Schottky contacts on ZnO NRs. Resistance responses of nanosensors were observed in the range from 50 to 150°C in 1% and 5% hydrogen in argon environment, which is below and above the explosive limit (4%) of hydrogen in air. The nanosensor's sensitivity increases from 11% to 67% with temperature from 50 to 150°C and also shows fast response time (9-16 s) and moderate recovery time (100-200 s). A sensing mechanism is proposed based on Schottky barrier changes at heterojunctions and change in depletion region of NRs. © 2015 AIP Publishing LLC.