Department of Electrical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

Inverter dead-time, which is meant to prevent shoot-through fault, causes harmonic distortion and change in the fundamental voltage in the inverter output. Typical dead-time compensation schemes ensure that the amplitude of the fundamental output current is as desired, and also improve the current waveform quality significantly. However, even with compensation, the motor line current waveform is observed to be distorted close to the current zero-crossings. The IGBT switching transition times being significantly longer at low currents than at high currents is an important reason for this zero-crossover distortion. Hence, this paper proposes an improved dead-time compensation scheme, which makes use of the measured IGBT switching transition times at low currents. Measured line current waveforms in a 2.2 kW induction motor drive with the proposed compensation scheme are compared against those with the conventional dead-time compensation scheme and without dead-time compensation. The experimental results on the motor drive clearly demonstrate the improvement in the line current waveform quality with the proposed method. © 2014 IEEE.

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India International Conference on Power Electronics, IICPE

An improved dead-time compensation scheme for voltage source inverters considering the device switching transition times

This paper develops the equations of motion in the reduced space for the wheeled inverted pendulum, which is an underactuated mechanical system subject to nonholonomic constraints. The equations are derived from the Lagrange-d'Alembert principle using variations consistent with the constraints. The equations are first derived in the shape space, and then, a coordinate transformation is performed to get the equations of motion in more suitable coordinates for the purpose of control. © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

IFAC-PapersOnLine

Reduced equations of motion for a wheeled inverted pendulum

Geometric control of a spherical robot rolling on a horizontal plane with three independent inertia disc actuators is considered in this note. The dynamic model of the spherical robot in the geometric framework is used to establish the strong accessibility and small-time local controllability properties. Smooth stabilizability to an equilibrium fails for the nonholonomic spherical robot. A novel contribution of this note is a smooth, asymptotically stabilizing geometric control law for position and reduced attitude, which corresponds to an equilibrium submanifold of dimension one. From Brockett's condition, this is the best possible dimension of a smoothly stabilized equilibrium submanifold. We also present a novel smooth global tracking controller for tracking position trajectories. © 1963-2012 IEEE.

IEEE Transactions on Automatic Control

Geometric controllability and stabilization of spherical robot dynamics

In this paper, a new three-phase hybrid seven level inverter topology with a single DC supply is proposed for the first time. The proposed inverter is realized by cascading two three level flying capacitor inverters with a half bridge module. The inverter topology is having multiple switching state redundancies for each of the pole voltage levels. By using these switching state redundancies, capacitor charging can be controlled in every PWM switching cycle. This feature is advantageous for reducing the capacitor sizing. Another advantage of the proposed inverter is that the charge balancing of each capacitor can be controlled irrespective of modulation index and load power factor. A hysteresis controller based capacitor charge control algorithm is implemented for the proposed inverter. Furthermore, the proposed topology uses lesser number of semiconductor devices, capacitors and DC power supplies compared to conventional seven level inverter topologies. The proposed topology is tested with open loop V/f control scheme in an induction motor drive. Inverter is tested for entire modulation range and experimental results for steady-state operation are presented for various fundamental frequencies. Experimental results showing the effectiveness of capacitor charge control for both steady state and transient operating conditions are presented.

2015 17th European Conference on Power Electronics and Applications, EPE-ECCE Europe 2015

A hybrid seven level inverter topology with a single DC supply and reduced switch count

In Smart Grid there are abundant number of grid connected Voltage Source Converters (VSC) in the form of Electric Vehicle (EV) battery chargers, Renewable Energy Source (RES) fed grid connected inverters etc., that can be used for active and reactive power support to the grid. The VSCs remain idle when the load in case of EV charger or the energy source in case of RES fed grid connected inverters is not available. This work presents a single-phase PQ theory based control strategy to improve the utilization factor of such converters by using them to support the reactive power to the local loads when they are idle. The proposed control scheme is implementable with less computational effort. The system is further analyzed by calculating appropriate minimum DC bus voltage for a given amount of reactive power to be supported. The analysis for the designed system is validated using MATLAB-Simulink based simulation and a scaled down laboratory based experimental setup. The results are in good agreement with the analysis. © 2015 IEEE.

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

Improved utilization of grid connected voltage source converters in smart grid through local VAR compensation

This paper describes the design and implementation of a controller to track the desired heading angle for an unmanned ground vehicle (UGV) considering the limits on rotation of steering wheel and steering motor rate. The well-known “bicycle model” approximation, that considers the vehicle slip angle and ground-wheel interaction, has been used. In this work, combined closed loop control for steering motor and heading angle of the vehicle has been considered for better accuracy. The challenge in designing this control system is to include the actuator dynamics as the response time to steer the front wheel is in the same order as that of the heading angle dynamics of the vehicle. Experiments have been conducted, analysis of data collected is presented and the resulting mathematical representation is explained in detail. Results from both simulation and experimental implementation are also compared. It has been found that the vehicle controller can be tuned effectively to achieve the desired heading angle changes up to twenty degrees within three seconds when the vehicle is moving at a speed of 1.4 m/sec.

International Journal of Automotive Technology

Design and development of a heading angle controller for an unmanned ground vehicle

In this Letter, the authors present a unified framework for fall event detection and classification using the cumulants extracted from the acceleration (ACC) signals acquired using a single waist-mounted triaxial accelerometer. The main objective of this Letter is to find suitable representative cumulants and classifiers in effectively detecting and classifying different types of fall and non-fall events. It was discovered that the first level of the proposed hierarchical decision tree algorithm implements fall detection using fifth-order cumulants and support vector machine (SVM) classifier. In the second level, the fall event classification algorithm uses the fifth-order cumulants and SVM. Finally, human activity classification is performed using the second-order cumulants and SVM. The detection and classification results are compared with those of the decision tree, naive Bayes, multilayer perceptron and SVM classifiers with different types of timedomain features including the second-, third-, fourth- and fifth-order cumulants and the signal magnitude vector and signal magnitude area. The experimental results demonstrate that the second- and fifth-order cumulant features and SVM classifier can achieve optimal detection and classification rates of above 95%, as well as the lowest false alarm rate of 1.03%.

Healthcare Technology Letters

Unified framework for triaxial accelerometer-based fall event detection and classification using cumulants and hierarchical decision tree classifier

The glottal closure instant (GCI) detection is crucial in all kinds of speech processing applications. A variety of GCI detection methods were proposed but the performance of most existing methods was evaluated using only voiced parts of the speech signal. Under noisy conditions, the recorded speech consists of voiced, unvoiced and non-speech parts. Thus, most GCI detection methods demand an accurate voice activity detection (VAD) design. In this paper, we present post-processing techniques to improve the GCI detection accuracy and robustness in additive nonstationary noisy environments. We study the performance of the four methods: center of gravity (CoG), group delay function (GDF), zero frequency resonator (ZFR), and speech event detection using the residual excitation and a mean-based signal (SEDREAMS). The performance of each method with the proposed method-specific post-processing technique is tested and validated under both clean and noisy environments. Experimental results show that the method with post-processing technique outperforms the conventional GCI detection methods under noisy conditions. Results further show that the proposed technique can not only improve the overall detection accuracy but also reduce the complexity by avoiding VAD algorithm. © 2015 IEEE.

2nd International Conference on Signal Processing and Integrated Networks, SPIN 2015

Improving accuracy of glottal closure instant detection methods in nonstationary noise

We report on the fabrication and characterization of synthesized multiwall MoS2 nanotube (NT) and nanoribbon (NR) field-effect transistors (FETs). The MoS2 NTs and NRs were grown by chemical transport, using iodine as a transport agent. Raman spectroscopy confirms the material as unambiguously MoS2 in NT, NR, and flake forms. Transmission electron microscopy was used to observe cross sections of the devices after electrical measurements and these were used in the interpretation of the electrical measurements, allowing the estimation of the current density. The NT and NR FETs demonstrate n-type behavior, with ON/OFF current ratios exceeding 103, and with current densities of 1.02 μA/μm and 0.79 μA/μm at VDS = 0.3 V and VBG = 1 V, respectively. Photocurrent measurements conducted on a MoS2 NT FET revealed short-circuit photocurrent of tens of nanoamps under an excitation optical power of 78 μW and 488 nm wavelength, which corresponds to a responsivity of 460 μA/W. A long channel transistor model was used to model the common-source characteristics of MoS2 NT and NR FETs and was shown to be consistent with the measured data. © 2015 AIP Publishing LLC.

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Applied Physics Letters

Synthesized multiwall MoS2 nanotube and nanoribbon field-effect transistors

This work presents a Ku-band microelectromechanical systems (MEMS) based 5-bit phase shifter using dc contact single-pole-four-throw (SP4T) and single-pole-double-throw switches. The design is implemented using a coplanar waveguide transmission line. Two individual 2-bit phase shifters and one 1-bit phase shifter are cascaded to develop the complete 5-bit phase shifter. The phase shifters are fabricated on 635-μm alumina substrate using a surface micromachining process. The 5-bit phase shifter demonstrates an average insertion loss of 2.65 dB in the 13-18-GHz band with a return loss better than 22 dB and average phase error less than 0.68° at 17 GHz. Total area of the fabricated 5-bit phase shifter is 4.7× 2.8mm2. The reliability of the single-pole-single-throw and SP4T switches show more than 10 million cycles with an RF power of 0.1-2 W. Furthermore, reliability of the MEMS phase shifter is extensively investigated and presented with cold and hot switched conditions. To the best of our knowledge, this is the first reported MEMS 5-bit phase shifter in the literature that has undergone different reliability and qualification testing including 3-axis vibrations. © 2014 IEEE.