Department of Electrical Engineering

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IIT Jodhpur

The paper presents a method for the design of a sliding mode controller for a class of mismatched uncertain systems. A new state dependent nonlinear switching surface is proposed. A control problem for slosh free-motion of a container is considered as the representative of a typical class of systems. A simple pendulum model is considered to represent the lateral slosh. The validity of the proposed scheme is demonstrated by simulation results. © 2009 EUCA.

World University root node

2009 European Control Conference, ECC 2009

Sliding mode control for slosh-free motion using nonlinear sliding surface

This tutorial paper presents the concepts of sliding mode controller (SMC) and sliding mode observer(SMO) design for different DC/DC converters. Design and implementation aspects, using FPGA, of sliding mode controller and sliding mode observer for three basic topologies of DC/DC converters are discussed. Sliding Mode Control, an established technique for control and estimation, is implemented for three different converters. To make the system sensor-less hence, cost effective, Sliding Mode Observer is used. FPGA tool is used to implement the sliding mode controller along with sliding mode observer. © 2014 IEEE.

IECON Proceedings (Industrial Electronics Conference)

A tutorial on implementation of sliding mode observer for DC/DC power converters using FPGA

The low and medium voltage renewable energy based dc distribution systems are catching increased attention world-wide due to their inherent benefits over ac systems. Higher efficiency, simple control, more suitable for integration of the sources producing dc power, are some of the main benefits of the dc systems. However, these systems are prone to serious stability issues caused by the constant power load (CPL) nature of the point-of-load converters (POLs). This paper deals with the stabilization and voltage regulation of dc/dc buck converter feeding a combination of the constant voltage resistive load (CVL) and CPL in a dc micro-grid application. A sliding mode controller is proposed which ensures supply of constant power demanded by the CPL and tight voltage regulation (error less than 0.1 V) of the output voltage. The effectiveness of the controller is validated through simulation results under different operating conditions. It is shown that the controller is robust to the large changes in supply voltage and the load. © 2014 IEEE.

2014 IEEE International Conference on Power Electronics, Drives and Energy Systems, PEDES 2014

Voltage regulation and stabilization of DC/DC buck converter under constant power loading

The bias-stress stability of low-voltage organic p-channel and n-channel thin-film transistors (TFTs) based on five promising organic semiconductors and fabricated on flexible polyethylene naphthalate (PEN) substrates has been investigated. In particular, it has been studied to which extent the bias-stress-induced decay of the on-state drain current of the TFTs is affected by the choice of the semiconductor and by the gate-source and drain-source voltages applied during bias stress. It has been found that for at least some of the organic p-channel TFTs investigated in this study, the bias-stress stability is comparable to that of a-Si:H and metal oxide TFTs, despite the fact that the organic TFTs were fabricated at significantly lower process temperatures, which is important in view of the fabrication of these devices on plastic substrates. © 2014 Elsevier B.V. All rights reserved.

Organic Electronics

Bias-stress stability of low-voltage p-channel and n-channel organic thin-film transistors on flexible plastic substrates

It has been an established fact that the presence of Constant Power Load (CPL) in DC micro-grid causes instability as it has negative impedance characteristic. This poses a serious challenge for the stability of the DC micro-grid in spite of ensuring stability of individual converters. Some efforts are made by the community to address the issue. In this paper, we have proposed a sliding-mode controller with a non-linear sliding surface to ensure large signal stability. The proposed non-linear surface ensures that constant power is maintained by the converter. The proposed controller is able to mitigate CPL effect of tightly regulated POLs and ensures stable operation of DC micro-grid under various disturbances. Proposed controller is implemented on a typical DC micro-grid feeding a CPL. The theoretical development is verified through simulations in MATLAB Simulink environment. © 2014 IEEE.

Proceedings of the IEEE International Conference on Industrial Technology

On design of a robust controller to mitigate CPL effect - A DC micro-grid application

All the methods available in literature for lossless coding comprises of two steps, one is the prediction scheme that results into prediction error and the second one consists of entropy coding of prediction error samples. In this work we introduce a scheme which adds a step prior to entropy coding technique due to which, the achieved gain in terms of compression is high. The additional step works on the predicted error frames obtained after applying any prediction scheme. The error frames so obtained are remapped into another domain of 8 bits per error sample. While remapping, two files are generated which needs to be compressed, One is the remapped error file itself while the second file consists of overhead information needed to get back the original error samples. The second file consists of binary numbers. The remapped file is compressed by CALIC encoder while the other is kept as it is, causing an addition of one bit per pixel overhead to the compressed file. Results show that instead of going in a traditional manner if we follow the proposed path, there will be a gain of about 0.21 bpp on an average. Additionally the comparison has also been made against other prominent codecs like JPEG and CALIC. © 2014 IEEE.

Data Compression Conference Proceedings

Residue coding technique for video compression

To diagnose health status of the heart, heart monitoring systems use heart signals produced during each cardiac cycle. Many types of signals are acquired to analyze heart functionality and hence several heart monitoring systems such as phonocardiography, electrocardiography, photoplethysmography and seismocardiography are used in practice. Recently, focus on the at-home monitoring of the heart is increasing for long term monitoring, which minimizes risks associated with the patients diagnosed with cardiovascular diseases. It leads to increasing research interest in portable systems having features such as signal transmission capability, unobtrusiveness, and low power consumption. In this paper we intend to provide a detailed review of recent advancements of such heart monitoring systems. We introduce the heart monitoring system in five modules: (1) body sensors, (2) signal conditioning, (3) analog to digital converter (ADC) and compression, (4) wireless transmission, and (5) analysis and classification. In each module, we provide a brief introduction about the function of the module, recent developments, and their limitation and challenges. © 2014 Elsevier Ltd.

Computers in Biology and Medicine

Heart monitoring systems-A review

This paper aims to propose a noble method to estimate the auto-regressive(AR) coefficients used by least-square(LS) based predictors. Estimation of this LS based predictors is computationally most complex process. This process requires a covariance matrix comprised of chosen causal pixels and also the inverse elements of the same matrix. Computational requirements of this process depends on the number of pixels for which the predictor is trained and also on the order of the predictor. Due to this high complexity, the predictor is not used practically although it provides a high compression ratio. Thus, an alternative algorithm, popularly known as LOPT-3D, was proposed in literature. However, the number of pixels required for the estimation of AR parameters are still large, and thereby, making it impracticable for real-time implementations. The proposed method overcomes this limitation by effectively making use of previously estimated AR parameters. Copyright 2014 ACM.

ACM International Conference Proceeding Series

Temporal stationarity based prediction method for lossless video coding

This paper presents a Wavelet based alienation technique to detect and classify various faults on transmission line. The proposed scheme analyses the absolute values of three phase current signals over a half cycle to obtain detail coefficients. These detail coefficients of half a cycle are compared with those of previous half cycleto compute alienation coefficients which are further utilized to detect and classify the faults. The proposed technique was able to discriminate non-fault transients such as capacitance, inductance and load switching, from fault transients. The increase in the sensitivity of protection scheme, due to utilization of wavelet based detail decomposition, has been established by case studies. The proposed algorithm is tested for different locations and various types of faults. The algorithm is proved to be successful in detecting and classifying various types of faults in a half cycle. © 2014 IEEE.