Faculty Publications

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Publications by NITK Faculty

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    Effect of Primary VSC-HVDC Controls on the Performance of Ancillary Frequency Control Strategies
    (Institute of Electrical and Electronics Engineers Inc., 2022) Rashmi, n.; Gaonkar, D.N.
    This paper analyses the impact of active and reactive power controls of VSC-HVDC on the behaviour of frequency controllers. The performance of droop and PI type frequency control strategies are investigated. The effect of feedforward and feedback active power loops are examined through bandwidth analysis. The influence of reactive power controllers on the performance is also studied. Inferences are drawn through MATLAB/SIMULINK based time domain simulations. © 2022 IEEE.
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    Analysis of FSO Systems with SISO and MIMO Techniques
    (Springer New York LLC barbara.b.bertram@gsk.com, 2019) Krishnan, P.
    Free space optics (FSO) is a form of line of sight communication technology that uses the help of LASERS and photodetectors to give optical connections from one place to another without the use of an optical fiber. The major hindrance to an FSO communication system comes in the form of atmospheric turbulences characterized by haze, rain, snow, storms among others. In this paper, the bit error rate performance of single input single output and multiple input multiple output based FSO system is analyzed and compared. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
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    Performance enhancement using multiple input multiple output in dual-hop convergent underwater wireless optical communication-free-space optical communication system under strong turbulence with pointing errors
    (SPIE, 2021) Bhargava Kumar, B.K.; Naik, R.P.; Krishnan, P.
    For the first time, we propose a dual-hop multiple input multiple output (MIMO)-based convergent underwater wireless optical communication (UWOC)-free-space optical (FSO) system. The UWOC and FSO links are Gamma-Gamma (GG) distributed. Closed-form expression for the average bit error rate (ABER) is derived for the proposed MIMO-based dual-hop UWOC-FSO convergent system using the GG cumulative distribution function. The end-to-end system performance analysis is carried out by considering the turbulence, attenuation, and pointing error effects for UWOC and FSO links. For the UWOC link, different oceanic conditions, such as the clear ocean, coastal ocean, and turbid harbor, are considered. Various atmospheric effects, such as clear air, fog, rain, drizzle, and haze, are considered for the FSO link. The analytical results of the proposed MIMO-based convergent system are compared with single-input single-output (SISO) system. As a result, it is observed that the proposed MIMO 2 × 3 scheme offers an improvement of 35 dB in the average signal-to-noise ratio compared with the SISO system at ABER of 10-5 in the case of weak pointing error. © 2021 Society of Photo-Optical Instrumentation Engineers (SPIE).
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    Performance analysis of radio-over-free-space optical communication system with spatial diversity over combined channel model
    (Springer, 2022) Kumar, A.; Krishnan, P.
    Radio over Free Space Optical (RoFSO) communication is accepted as one of the promising technologies in communication systems that can fulfill the demands of high bandwidth and high data rate because it has an inherent quality of transmission capacity significantly more than what is provided by radio transmission technologies. It is a low power, high data rate, unlicensed spectrum, and large bandwidth wireless technology. Nevertheless, the full potential of the RoFSO communication system can be utilized only by overcoming the adverse effects of the atmospheric channel, which are scattering, absorption, and turbulence. Pointing error is also another factor responsible for the deterioration of the performance of the RoFSO system. In this paper, spatial diversity at the transmitting and receiving ends is used to improve the performance of the RoFSO system in various turbulence and weather conditions. The Malaga distribution has been used to model atmospheric turbulence. For single input single output (SISO), single input Multiple output (SIMO), multiple input single output (MISO), multiple input multiple output (MIMO) configurations, closed form expressions for average bit error rate (BER) have been estimated. To improve the performance of the proposed system, the two combining techniques, Optimal Combining and Equal Gain Combining, are being considered. The results obtained are compared to various configurations such as SISO, SIMO, MISO, and MIMO cases. The result shows that MIMO offers better average BER performance compared with SISO, SIMO and MISO cases. The 4 × 4 MIMO case has an average BER of 10 - 9 at an average SNR of 25 dB, but the SISO case has an average BER of 10 - 1 at the same average SNR. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    Numerical and Experimental Investigations on Robust Output Feedback Control for Active Vibration Attenuation of Flexible Smart System
    (Institute of Electrical and Electronics Engineers Inc., 2023) Parameswaran, A.P.; Padmasali, A.N.; Gangadharan, K.V.
    This paper investigates the prototyping and implementation of an output feedback-based robust controller on a Field Programmable Gate Array (FPGA) platform. The Smart System under Test (SSuT) in this submission is a flexible cantilever beam bonded with Piezoelectric (PZT 5H) patches that act as a sensor as well as an actuator (perturbance creation as well as control actuation). For ease of modeling and subsequent controller design in the laboratory studies, the low-frequency dynamics of the smart system are approximated to only a Single Degree of Freedom (SDOF) in terms of flexural vibrations. The SSuT is modeled analytically through finite element modeling and experimentally through sub-space system identification process. The developed models' accuracy is compared with the experimental results of non - parametric modeling. The developed models are then used to conduct the simulation studies with the designed robust output feedback controller in the closed loop. Apart from the simulation studies, the designed controller was also prototyped on an FPGA platform using LabVIEW FPGA with the associated hardware in loop to carry out the experimental validation of its performance. The robustness and efficiency of the prototype controller to control the system vibrations in real-time were proved through extensive tests at single resonant frequencies and a range of frequencies encompassing the dominant resonant regions in the flexural mode. Findings from this study are further used to ensure satisfactory active vibration control of smart cantilever systems in various heavy/aerospace industries by approximating them to suitable benchmark systems in the laboratory. © 2013 IEEE.
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    Influence of hybrid smart damping system on bi-directionally tapered functionally graded plate using 1-3 PZC resting on winkler-pasternak flexible support
    (SAGE Publications Inc., 2025) Shada, S.K.; Kattimani, S.; Ramesh, M.R.
    This article presents a numerical investigation of free vibrational features of bi-directionally tapered functionally graded (BTFG) plate unified with active constrained layer damping (ACLD) on a two-parameter Winkler-Pasternak flexible support. In conjunction with the virtual work principle, the first-order shear theory for deformation is employed. The plate’s damping is actively controlled using a velocity feedback control system with 1-3 piezoelectric patches consisting of piezoelectric and viscoelastic layers. Effects of foundation/support parameters (Kw and Ks), taper ratios, ACLD patch placement, and boundary conditions are systematically analysed through frequency response studies. Results demonstrate that incorporating ACLD patches significantly enhances damping features. Revealing with edge patch placement yields superior vibration suppression on the substrate plate. The study highlights the synergistic impact of ACLD patches, flexible supports, and active control, presenting a robust solution for precision vibration control in advanced structural applications. © The Author(s) 2025