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

Conventional pulse width modulation (PWM) schemes for dual inverter fed drive synthesise the reference voltage as a switched average of minimum three voltage vectors from individual inverters. As a result, the number of transitions in the inverter increases. This paper introduces a family of PWM methods, where the reference voltage is synthesised as a switched average of only two voltage vectors from individual inverter. This leads to simultaneous clamping of two phases, thus reducing the number of switching transitions in the inverter. The concept and realisation of the proposed PWM are discussed and compared with conventional bus clamping PWM methods on the basis of inverter power loss and common mode voltage generation. The proposed PWM is experimentally validated on an open end winding induction motor drive operating with open loop control. Synchronised carrier modulation is considered for PWM generation. © 2020 IEEE.

World University root node

Department of Electrical Engineering

9th IEEE International Conference on Power Electronics, Drives and Energy Systems, PEDES 2020

Clamping modulation scheme for low speed operation of dual inverter fed drives

Micro grinding is an emerging technology for producing structured surfaces on hard and brittle materials. A micro pencil grinding tool (MPGT) consists of a layer of superabrasive grits, bonded to a solid cylindrical surface. Randomly distributed and geometrically undefined grits interact with the workpiece surface at random positions. These random grit positions and protrusions lead to a difference in the size of undeformed chips. This study presents an analytical method to understand the undeformed chip geometry, that considers grit kinematics. Kinematic simulation of grit trajectory paths in longitudinal direction showed a reduced number of active grits in micro grinding with an increase in speed ratio and with reduced tool dimensions. MPGTs with different diameters, grit sizes, and planar grit densities have been used to perform the experiments on a 16MnCr5 hardened steel material. The influence of maximum radial height grits on surface generation in micro grinding has been verified experimentally for up and down grinding modes. Microscopic observations of ground surfaces have shown the distinct differences between up and down grinding modes, which are similar to the surface generation in milling processes. Moreover, the formation of linear grooves with uniform depth and width unlike conventional surface grinding at lower speed ratios indicated the influence of individual grits on surface generation. Trajectory path simulation results have also shown the same observation. © 2019 Elsevier Ltd

Department of Mechanical Engineering

Fulltext

International Journal of Machine Tools and Manufacture

Analytical and experimental investigations on the mechanisms of surface generation in micro grinding

In this work, we consider a sequence of J matrix multiplication jobs which needs to be distributed by a master across multiple worker nodes. For i ? {1, 2, . . ., J}, job-i begins in round-i and has to be completed by round-(i + T). Previous works consider only the special case of T = 0 and focus on coding across workers. We propose here two schemes with T > 0, which feature coding across workers as well as the dimension of time. Our first scheme is a modification of the polynomial coding scheme introduced by Yu et al. and places no assumptions on the straggler model. Exploitation of the temporal dimension helps the scheme handle a larger set of straggler patterns than the polynomial coding scheme, for a given computational load per worker per round. The second scheme assumes a particular straggler model to further improve performance (in terms of encoding/decoding complexity). We develop theoretical results establishing (i) optimality of our proposed schemes for a certain class of straggler patterns and (ii) improved performance for the case of i.i.d. stragglers. These are further validated by experiments, where we implement our schemes to train neural networks. © 2020 Neural information processing systems foundation. All rights reserved.

Department of Data Science

Advances in Neural Information Processing Systems

Coded sequential matrix multiplication for straggler mitigation

The presence of regulated power converter in the three-phase microgrid system makes it vulnerable to interactions with the grid and causes instability. Because, the regulated converters exhibits negative impedance characteristics and acts like constant power loads (CPLs). To ensure the system stability, adaptive controller can be used in the system controller design. However, to design these adaptive controllers real-time grid impedance information is required and this is a challenging task. In this paper a Hall Binary Sequence (HBS) which is a class of pseudo random binary sequence (PRBS) is proposed for real-time impedance measurement. The HBS perturbation is computationally very effective compared to conventional multi-sine perturbation methods. Perturbation signals for impedance measurement should have low crest factor and less measurement time. The proposed HBS has low crest factor and the impedance can be measured within 3-5 perturbation cycles. To extract the impedance of the grid, the HBS is added to the inner loop currents (d-axis and q-axis) components of the energy storage system (ESS). Next, the Generalized Nyquist Stability Criteria (GNC) is applied to the return ratio matrix to check the system stability. The effectiveness of proposed impedance measurement algorithm using the HBS has been tested on three-phase microgrid system in MATLAB/Simulink environment. Simulations results are validated by conducting experiment on a 2kW laboratory test bed and results proved the robustness of the proposed impedance measurement algorithm. © 2020 IEEE.

Small signal stability analysis of three-phase microgrid in the presence of energy storage system

In this paper, a multi-port hybrid nine-arm modular multilevel converter is proposed for integration of an offshore wind farm into the HVDC subsea power transmission system feeding an offshore subsea oil and gas processing load. A detailed analysis of circulating current of the proposed converter is performed and accordingly, a control architecture based on a synchronous rotating reference frame is developed. The proposed control architecture regulates the circulating current at an optimal value in order to achieve a stable and efficient operation of the multi-port hybrid nine-arm modular multilevel converter. The proposed architecture incorporates control of phase angle difference between the source port and load port voltages, which is the key to regulate the circulating current magnitude. A system level simulation model has been developed on PLECS simulation software to demonstrate the performance of the proposed control architecture. © 2020 IEEE.

A new architecture for circulating current control in a multi-port hybrid nine-arm modular multilevel converter

2020 7th International Conference on Signal Processing and Integrated …

DSP Implementation of Hilbert Transform for Voltage Variation Tracking

In three-dimensional computer simulations of model non-Brownian jammed suspensions, we compute the time required to reach homogeneous flow upon yielding, by analyzing stresses and particle packing at different shear rates, with and without confinement. We show that the stress overshoot and persistent shear banding preceding the complete fluidization are controlled by the presence of overconstrained microscopic domains in the initial solids. Such domains, identifiable with icosahedrally packed regions in the model used, allow for stress accumulation during the shear startup. Their structural reorganization under deformation controls the emergence and the persistence of the shear banding. © 2020 American Physical Society.

Department of Physics

Physical Review E

Emergence and persistence of flow inhomogeneities in the yielding and fluidization of dense soft solids

Given a linear recurrence sequence (LRS), specified using the initial conditions and the recurrence relation, the Skolem problem asks if zero ever occurs in the infinite sequence generated by the LRS. Despite active research over last few decades, its decidability is known only for a few restricted subclasses, by either restricting the order of the LRS (upto 4) or by restricting the structure of the LRS (e.g., roots of its characteristic polynomial). In this paper, we identify a subclass of LRS of arbitrary order for which the Skolem problem is easy, namely LRS all of whose characteristic roots are (possibly complex) roots of real algebraic numbers, i.e., roots satisfying xd = r for r real algebraic. We show that for this subclass, the Skolem problem can be solved in NPRP. As a byproduct, we implicitly obtain effective bounds on the zero set of the LRS for this subclass. While prior works in this area often exploit deep results from algebraic and transcendental number theory to get such effective results, our techniques are primarily algorithmic and use linear algebra and Galois theory. We also complement our upper bounds with a NP lower bound for the Skolem problem via a new direct reduction from 3-CNF-SAT, matching the best known lower bounds. © S. Akshay, Nikhil Balaji, Aniket Murhekar, Rohith Varma, and Nikhil Vyas; licensed under Creative Commons License CC-BY

Department of Mathematics

Leibniz International Proceedings in Informatics, LIPIcs

Near-optimal complexity bounds for fragments of the skolem problem

Large bridge structures that are subject to Alkali Silica Reaction (ASR) and Delayed Ettringite Formation (DEF) are a major cause of concern; there is a need for understanding the internal deterioration mechanism and their prognosis. The Compatibility Strut-and-Tie Method (C-STM) is used to model the behaviour of experimentally tested C-beam specimens subject to varying degrees of ASR/DEF deterioration as well as varying degrees of associated corrosion of the rebars. The simulation accounts for age-modified cover and core concrete material properties, and the resulting passive prestress effects on the longitudinal and transverse reinforcement. An increase in strength and stiffness of the specimens with an increase in the passive prestress effect is observed. However, the energy absorption capacity of the heavily deteriorated specimen saw a 59% reduction. Post-peak stress softening of the diagonal arch-strut successfully simulates the embrittlement and decrease in deformation capacity of the most heavily deteriorated condition. Corrosion of the longitudinal and transverse reinforcement in the beam-column joint is found to decrease the load and deformation capacity by some 35%, and the energy absorption by 86% after 60 years of rebar corrosion. The mode of failure for all the specimens is the crushing of the diagonal concrete arch-strut in the beam-column joint. The progression of nonlinear events that lead to failure of large beam-column joints that are affected by varying levels of ASR/DEF deterioration are successfully tracked by the C-STM. © 2020 Elsevier Ltd

Department of Civil Engineering

Engineering Structures

Simulating behaviour of large reinforced concrete beam-column joints subject to ASR/DEF deterioration and influence of corrosion

B0 -VPG graphs are intersection graphs of vertical and horizontal line segments on a plane. Cohen, Golumbic, Trotter, and Wang [Order, 2016] pose the question of characterizing B0 -VPG permutation graphs. We respond here by characterizing B0 -VPG cocomparability graphs. This characterization also leads to a polynomial time recognition and B0 -VPG drawing algorithm for the class. Our B0 -VPG drawing algorithm starts by fixing any one of the many posets P whose cocomparability graph is the input graph G. The drawing we obtain not only visualizes G in that one can distinguish comparable pairs from incomparable ones, but one can also identify which among a comparable pair is larger in P from this visualization. © 2020, Springer Nature Switzerland AG.