National Institute of Technology, Meghalaya

About: National Institute of Technology, Meghalaya is a education organization based out in Shillong, India. It is known for research contribution in the topics: Control theory & Computer science. The organization has 503 authors who have published 1062 publications receiving 6818 citations. The organization is also known as: NIT Meghalaya & NITM.

Processing of hardened steel by MQL technique using nano cutting fluids

Abstract: This article discussed the impact of various nanofluids on the machinability aspects during hard turning of AISI 4340 alloy steel. The experiment was performed using minimum quantity lubrication (M...

Modelling and comparative dynamic analysis due to demagnetization of a torque controlled permanent magnet synchronous motor drive for energy-efficient electric vehicle.

Abstract: In this paper modelling and comparative dynamic analysis of a field oriented controlled permanent magnet synchronous motor (PMSM) torque drive employing a hysteresis current controller and a PWM (Pulse Width Modulation) operated current controller is presented. To illustrate the proposed concept in this torque controlled drive, torque and mutual flux linkages are applied as external inputs and speed of the machine is kept fixed. Moreover the magnitude of torque angle as well as stator current reference is controlled through the proposed machine dynamics. In fact a computation based on demagnetization of direct axis current to achieve the flux weakening in this proposed drive for current compensation is also introduced. To achieve the faster computation and accuracy Euler’s integration technique is used to solve the proposed complex dynamics of the permanent magnet synchronous machine. In a hysteresis current, controllers with a large hysteresis band current ripple and the torque pulsations are prominent at higher carrier frequency of the inverter. Additionally, a relationship with the magnitude of torque pulsations, PWM carrier frequency and the hysteresis window size is also achieved through various case-studies. Furthermore, the presence of current ripple and the pulsations generate some noise as well as vibration in a typical electric propulsion system. Afterwards a PWM current controller with identical operating conditions is proposed for such reduction of torque pulsation as well as ripples in the current waveform. Finally various feasible results are presented through MATLAB simulation and necessary hardware implementation to justify the comparative assessment of the proposed controllers for dynamic performance analysis in energy-efficient electric vehicles.

Comparison of Output Power Control Performance of Wind Turbine using PI, Fuzzy Logic and Model Predictive Controllers

Abstract: In the variable speed wind energy conversion system, one of the operational problems is to handle the speed uncertainty and discontinuity of wind, that influence the power generation from a wind energy conversion systems (WECS). In order achieve a stable power output from a WECS despite variations in the wind speed, a number of control algorithms were devised in the literature over the past few years. Pitch angle control is widely used for regulation of output power fluctuations in a WECS. The control objective is to maintain stable power generation against wind speed variation, which can be achieved by regulating the pitch angle and/or generator torque. In view of handling the uncertainties owing to wind speed variations, this paper pursued a comparative assessment of three controllers, namely Proportional-Integral control, Fuzzy logic control (FLC) and Model predictive control (MPC) schemes. To evaluate their performance a simulation setup for implementing these three controllers applied to a WECS is prepared in MATLAB/Simulink. From the obtained results, it is envisaged that the proposed MPC exhibits excellent response and robustness of the WECS in face of uncertainties owing to intermittency and discontinuity of the wind speed.

Coverage-Aware Recharging Scheduling Using Mobile Charger in Wireless Sensor Networks

Abstract: Energy recharging in wireless rechargeable sensor networks (WRSNs) has acquired much attention in recent years. In literature, many recharging path construction algorithms have been proposed. Most of them considered that all sensors are equally important and designed algorithms to increase the number of recharged sensors or decrease the path length of the mobile charger. However, different sensors have different coverage contributions. Recharging the sensors with larger coverage contribution can achieve better surveillance quality. The proposed recharging scheduling algorithm is divided into three phases, including the Initialization , Recharging Scheduling and Path Construction Phases . In the second phase, this paper proposed two recharging scheduling algorithms, namely the Cost-Effective ( CE ) algorithm and Cost-Effective with Considerations of Coverage and Fairness ( $C^{2}F$ ) algorithm . The proposed two algorithms construct paths for the mobile charger and select the recharging sensors based on the higher weight in terms of larger coverage contribution and smaller path cost. Performance results show that the CE and $C^{2}F$ algorithms yield better performance in terms of the fairness of recharging, recharging stability and coverage ratio, as compared with the existing studies.

Swarm Optimization-Based Modified Selective Harmonic Elimination PWM Technique Application in Symmetrical H-Bridge Type Multilevel Inverters

Abstract: The problem of elimination of harmonics and the need of a large number of switches in multilevel inverters (MLIs) have been a hot topic of research over the last decades. In this paper, a new variant swarm optimization (SO) based selective harmonic elimination (SHE) technique is described to minimize harmonics in MLIs, which is a complex optimization problem involving non-linear transcendental equation. Optimum switching angles are calculated by the proposed algorithms considering minimum total harmonic distortion (THD) and the best results are taken for controlling the operation of MLIs. The performance of the proposed algorithm is compared with the genetic algorithm (GA). Conventional MLIs have some disadvantages such as the requirement of a large number of circuit components, complex control, and voltage balancing problems. A novel seven-level reduced switch multilevel inverter (RS MLI) is proposed in this paper to recoup the need of a large number of switches. Matlab/Simulink software is used for the simulation of two symmetrical topologies, i.e., a seven-level cascaded H-bridge multilevel inverter (CHB MLI) and a seven-level (RS MLI). Simulation results are validated by developing a prototype of both MLIs. The enhancement of the output voltage waveform confirms the effectiveness of the proposed SO SHE approach.