Faculty Publications

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Publications by NITK Faculty

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Subject: search.filters.subject.Frequency response

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    Dynamic and harmonic analysis of pillar drilling machine spindle supported by hybrid bearing set
    (American Institute of Physics Inc. subs@aip.org, 2020) Chalageri, G.R.; Bekinal, S.I.; Doddamani, M.
    The objective of this work is to study the dynamic and harmonic response behavior of drilling spindle supported by hybrid bearing set (HBS). HBS consists of an angular contact bearing (ACB) and radial permanent magnetic bearing. Dynamic and harmonic analysis was performed in order to investigate the effect of bearing stiffness and thrust force on the natural frequency, critical speed and vibration amplitude of a drilling spindle system. In the first step, analyses were carried out for the spindle system supported by conventional ACB's considering the effective bearing span length. In the second step, the dynamic and harmonic responses were analyzed for the drilling spindle system supported by HBS by replacing conventional ACB's. The dynamic performance of spindle under ACB's and HBS is investigated systematically using Ansys rotor dynamic and harmonic response tool. This research highlights the feasibility of effective usage of HBS in drilling machine spindles with higher critical speeds and maximum amplitudes generating due to cutting forces. © 2020 Author(s).
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    Evaluation of Dynamic Characteristics of a VMC Spindle System Through Modal and Harmonic Response—Part 2: Spindle Supported by Hybrid Bearing Set
    (Springer Science and Business Media Deutschland GmbH, 2021) Chalageri, G.R.; Bekinal, S.I.; Doddamani, M.
    This paper extends the proposed dynamic analysis of spindle with conventional bearings of Part 1 and demonstrates feasibility of hybrid bearing set (HBS) usage in machine tool spindles. HBS consists of permanent magnet bearing (PMB) and conventional angular contact bearing (ACB). The rotordynamic and unbalance response of vertical machining center (VMC) spindle supported by HBS is presented. Harmonic responses are also determined using Ansys Workbench finite element tool. Results show that the system is stable at obtained frequencies, critical speeds are higher than the spindle operating speed range, and the maximum unbalance response is within acceptable limit. The comparison between the results of ACB and HBS has verified that the HBS can effectively be used in machine tool spindles with higher critical speeds and maximum amplitudes generating due to cutting forces. © 2021, Springer Nature Singapore Pte Ltd.
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    Smart materials and structures are extensively used in various engineering fields including aerospace, heavy engineering, civil engineering and domestic appliances. Of the various smart materials piezo electrics are widely used for both sensing and actuation applications. Currently, only a few general-purpose softwares are available with built-in smart element (piezo) capability. It is possible to use other software as well, by using initial strain concepts. This paper brings out the simulation of the piezoelectric effect in ID and 2D NASTRAN elements. The concept of thermal strain (or equivalent force) is used to simulate the strain generated by the piezo element in NASTRAN elements. Using this principle, the dynamic response of a circular plate excited by a piezo crystal is obtained and the present solutions are compared with the experimental results.
    (Simulation of piezoelectric effect in Nastran: Experimental and analytical estimation of dynamic response of a circular plate) Kamat, S.M.; Narayana, K.B.; Kanade, V.S.
    2005
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    Widely programmable high-frequency active RC filters in CMOS technology
    (Institute of Electrical and Electronics Engineers Inc., 2009) Laxminidhi, T.; Prasadu, V.; Pavan, S.
    We propose a circuit technique that enables the realization of widely programmable high-frequency active RC filters in CMOS technology. A fifth-order Chebyshev ladder filter having a digitally programmable 3-dB bandwidth (from 44 to 300 MHz) is used as a vehicle to validate our ideas. The opamp uses feedforward compensation for achieving high dc gain and wide bandwidth. The integrating resistors are realized as a series combination of a triode-operated MOSFET and a fixed polysilicon resistor. A charge-pump-based servo loop servoes the integrating resistor to a stable off-chip resistor. The principle of "constant capacitance scaling"is applied to the opamp and the integrating resistors so that the shape of the frequency response is maintained when the bandwidth is scaled over a 7 7times; range. The filter core, designed in a 0.18-?m CMOS process, consumes 54 mW from 1.8-V supply and has a dynamic range of 56.6 dB. © 2009 IEEE.
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    A simulation-based analysis of subsynchronous resonance with TCSC
    (Universitatea Politehnica din Timisoara blucretiu@yahoo.com, 2013) Batchu, S.; Kotian, S.M.; Shubhanga, K.N.
    In this paper a time-domain simulation-based SSR analysis has been carried out in PSCAD/EMTDC employing the IEEE first-benchmark system with thyristor-controlled series capacitor (TCSC). Though torsionalmode detuning behavior of a TCSC is well known its tuning performance for certain firing angles is demonstrated employing modal-speed evaluations. An attempt has been made to understand this nature of TCSC by obtaining its frequency response characteristics using frequency scanning technique. From the results it is inferred that the equivalent impedance of TCSC offers fictitious resistive component leading to mode-detuning. However, it is observed that at higher values of firing angle the resistive behavior diminishes thus resulting in mode-tuning.
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    Steiglitz-McBride adaptive notch filter based on a variable-step-size LMS algorithm and its application to active noise control
    (John Wiley and Sons Ltd Southern Gate Chichester, West Sussex PO19 8SQ, 2016) Roopa, S.; Narasimhan, S.V.; Babloo, B.
    Summary This paper proposes a new Steiglitz-McBride (SM) adaptive notch filter (SM-ANF) based on a robust variable-step-size least-mean-square algorithm and its application to active noise control (ANC). The proposed SM-ANF not only has fast convergence but also has small misadjustment. The variable-step-size algorithm uses the sum of the squared cross correlation between the error signal and the delayed inputs corresponding to the adaptive weights. The cross correlation provides robustness to the broadband signal, which plays the role of noise. The proposed SM-ANF is computationally simpler than the existing Newton/recursive least-squares-type ANF. The frequency response of the new SM-ANF has a notch depth of about -25 dB (for each of the three frequencies considered) and has spectral flatness within 5 dB (peak to peak). This robust notch filter algorithm is used as an observation noise canceller for the secondary path estimation of an ANC system based on the SM method. The ANC with proposed SM-ANF provides not only faster convergence but also an 11-dB improvement in noise attenuation over the SM-based ANC without such a SM-ANF. © © 2015 John Wiley & Sons, Ltd.
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    A high efficiency on-chip reconfigurable Doherty power amplifier for LTE communication cells
    (John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2018) Kumar, R.; Kanuajia, B.K.; Dwari, S.; Kumar, S.; Song, H.
    In this paper, a high efficiency on-chip reconfigurable Doherty power amplifier (DPA) with proposed topology is proposed for LTE or 4G communication cells. The proposed DPA consists of input driver topology, hybrid coupler, asymmetric amplifiers, and 1:1 balun filtered network. The proposed input driver circuit provides wide amplified signal operation within range of 2.3GHz to 6GHz with flat gain of 33 dB. The amplified signal is unsteadily divided into two paths toward the carrier and the power amplifier by 900 hybrid couplers and demonstrates 27.6 dB and 28.3 dB of gain along with 83.2% and 84.5% of power added efficiency at average output power of 40 dBm. The high efficiency and almost flatness in gain stability of proposed DPA providing better solution in order to overcome the interference and the broadband issues for LTE communication cells. The balun-filtered network is employed for combined the two outputs of carrier and peak amplifiers that provides more uniform desired band of operation in the frequency responses. The proposed DPA circuit are implemented and optimized by using advanced design RF simulator platform. The fabricated chip is made by using 0.13 ?m GaN HEMT on Si-Nitride monolithic microwave integrated circuit die process. The fabricated chip of DPA provides 85% of PAE with 28 dB gain which are made close agreement with simulation results. The size of chip is 2.8*1.2mm2 which occupies less die area as compared to existing DPAs. © 2018 Wiley Periodicals, Inc.
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    Coupled evaluation of the free vibration characteristics of magneto-electro-elastic skew plates in hygrothermal environment
    (Techno-Press, 2019) Mahesh, V.; Kattimani, S.; Harursampath, D.; Nguyen, N.-T.
    The present article addresses the coupled free vibration problem of skew magneto-electro-elastic plates (SMEE) considering the temperature-moisture dependent material properties. The plate kinematics follows Reddy?s higher order shear deformation theory. With the aid of finite element methods, the governing equations of motion are derived considering the Hamilton?s principle and solved by adopting condensation technique. The influence of different temperature and moisture dependent empirical constants on the frequency response of SMEE plate has been assessed. In addition, the natural frequencies corresponding to various fields are evaluated and the effect of empirical constants on these coupled frequencies is determined. A detailed parametric study has been carried out to assess the individual effects of temperature and moisture dependent empirical constants along with their combined effect, aspect ratio, length-to-width ratio, stacking sequence and boundary conditions. The results reveal that the external environment as well as the geometrical skewness has a significant influence on the stiffness of the SMEE plates. © 2019 Techno-Press, Ltd.
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    Finite element simulation of controlled frequency response of skew multiphase magneto-electro-elastic plates
    (SAGE Publications Ltd info@sagepub.co.uk, 2019) Mahesh, M.; Kattimani, S.
    The linear frequency response of skew multiphase magneto-electro-elastic composite plate embedded with active constrained layer damping treatment has been studied. The volume fraction of piezoelectric fibres embedded in the piezomagnetic matrix significantly affects the coupling characteristic of this multiferroic material, and hence, the frequency of the skew multiphase magneto-electro-elastic plate is drastically altered. This study emphasizes on evaluating the influence of different volume fraction of barium titanate (BaTiO3) and cobalt ferrite (CoFe2O4) on the frequency characteristics of skew multiphase magneto-electro-elastic. In this regard, a finite element formulation has been proposed to assess the damped response of such skew multiphase magneto-electro-elastic plates. Incorporating the complex modulus approach, the constrained viscoelastic layer of the active constrained layer damping patch is modelled. In addition, the effect of geometrical skewness has also been investigated. Meanwhile, an exhaustive parametric study is carried out to analyse the influence of control gain, patch position and fibre orientation angle of piezoelectric composite. © The Author(s) 2019.
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    Performance of magnetorheological elastomer based torsional vibration isolation system for dynamic loading conditions; ??????????????????????????
    (Central South University of Technology f-ysxb@mail.csut.edu.cn, 2020) Shenoy, S.K.; Kuchibhatla, S.A.R.; Singh, A.K.; Gangadharan, K.V.
    Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attributes of semi-active as well as the active control system. In the present study, the non-homogenous field-dependent isolation capabilities of the magnetorheological elastomer are explored under torsional vibrations. Torsional natural frequency was measured using the serial arrangement of accelerometers. Novel methods are introduced to evaluate the torsional stiffness variations of the isolator for a semi-definite and a motor-coupled rotor system. For the semi-definite system, the isolation effect was studied using the frequency response functions from the modal analysis. The speed-dependent variations for motor-coupled rotor system were assessed using the shift in frequency amplitudes from torque transducers. Finite element method magnetics was used to study the variations in the non-homogenous magnetic field across the elastomer. The response functions for the semi-definite rotor system reveal a shift in the frequency in the effect of the magnetic field. Speed-dependent variations in the frequency domain indicate an increment of 9% in the resonant frequency of the system. © 2020, Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature.