Faculty Publications
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Publications by NITK Faculty
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Item Direct torque controlled induction motor drive based on cascaded three two-level inverters(Acta Press, 2014) Thippiripati, T.V.; Surapaneni, S.S.In this paper, a new and an effective voltage switching-state algorithm to Direct Torque Control (DTC) of induction motor drive is proposed, which makes less torque and flux ripple at various operating frequency conditions. In conventional DTC, the torque and flux ripples are difficult to reduce as the applied voltage vector is independent of rotor speed especially at low speeds. To overcome this problem, the proposed technique introduces a voltage switching-state algorithm for four-level inversion using cascading three two-level inverters, in which choice of inverter voltage states is the function of rotor speed. From simulation results, the torque and flux ripple are decreased with proposed DTC when compared with the conventional DTC technique at various operating frequencies.Item Design of magneto-rheological brake for optimum dimension(Springer Verlag service@springer.de, 2018) Lijesh, L.; Kumar, D.; Gangadharan, K.V.Online control of braking performance of magneto-rheological (MR) brake by bridling the apparent viscosity of MR fluid and by amending magnetic field is considered as an effective and smart option to replace the conventional disc brake. The magnetic field procreated by electromagnet in MR brake is reliant on dimensions and material properties of MR brake (casing, rotor and MR fluid region). Extensive works have been reported on enhancing the magnetic properties of MR fluid to achieve maximum braking performance; however, scarce works are available that reflects that the dimensions of MR brake influence the braking performance. Prior works on MR brakes focus on designing for meticulous outer dimensions of brakes, and thus, their results find little utility to a new designer. Therefore, the objective of the present work is to propose a methodology to determine the dimension of MR brake for a given outer dimensions, which shall provide maximum braking performance. The, braking performance is evaluated by assessing the effective torque and brake density. Magneto-static analysis using ANSYS is employed for determining the magnetic field in the MR region, and thereafter, the braking torque is calculated. From the obtained results, curve fit equations are proposed to estimate the values of (i) MR brake casing thickness, (ii) height of the MR brake to rotor, (iii) thickness of core, and (iv) thickness of MR fluid region, for achieving maximum torque. To validate the proposed methodology, MR brake with two different electromagnets and rotors is developed. The static performance of MR brake is evaluated by measuring the braking torque for different currents using a torque wrench and the dynamic performance of the MR brakes is performed on an MR brake test setup. The dynamic performance is evaluated by measuring viscous torque. Finally, the comparisons of the theoretical and experimental results are performed and the obtained results are presented. © 2018, The Brazilian Society of Mechanical Sciences and Engineering.Item Direct torque and flux control of switched reluctance motor with enhanced torque per ampere ratio and torque ripple reduction(Institution of Engineering and Technology JBristow@theiet.org, 2019) Krishna Reddy, P.; Ronanki, D.; Parthiban, P.A smooth torque control of switched reluctance motor (SRM) is essential to avoid speed fluctuations causing stability problems in vehicular applications. This can be accomplished by an appropriate motor design and/or use of direct control of torque in SRM. It is reported that high RMS current is required to minimise the torque ripple in the conventional direct torque and flux control (DTFC), thereby reducing the torque per ampere ratio. To overcome this issue, a new DTFC technique with improved torque per ampere ratio while minimising torque ripple in an SRM traction drive is presented. Results demonstrated that the proposed DTFC technique reduces torque ripple with enhanced torque per ampere. Finally, the performance of the proposed scheme is compared with conventional DTFC of a four-phase (8/6) SRM to show the improvement in the traction drive. © The Institution of Engineering and Technology 2019Item Investigation of magnetorheological brake with rotor of combined magnetic and non-magnetic materials(Springer Nature, 2019) Acharya, S.; Kumar, H.Magnetorheological (MR) brakes are a type of electromagnetic brakes that make use of controllable viscoelastic properties of magnetorheological fluid for braking. The torque capacity of the MR brake depends on the magnitude of magnetic flux density generated in the MR fluid. In this study, the effect of combination of magnetic and non-magnetic materials for rotor disk of MR brake with the objective to maximizing the flux density in the MR fluid gap at the rotor periphery was investigated. Initially, the MR brake rotor disk radius and MR fluid gap thickness were determined by using Genetic Algorithm optimization technique for desired torque ratio and torque capacity. Magnetostatic analyses were performed at different current magnitudes to determine the magnetic field and flux density in the MR brake. Further, to enhance the magnetic field intensity in the MR fluid at the rotor periphery, the rotor was modeled with three different configurations of MR brake with combinations of magnetic and non-magnetic steel and magnetostatic analyses of the MR brake were performed. It was found that the leakage of flux away from rotor periphery was reduced and there is significant increase and concentration of the magnetic field and flux density in the MR fluid gap through the use of rotor disk with combined magnetic and non-magnetic materials which would subsequently increase the torque capacity of the MR brake. © 2019, Springer Nature Switzerland AG.Item FPGA based direct torque control with speed loop Pseudo derivative controller for PMSM drive(Springer, 2019) Karthikeyan, A.; Koothu Kesavan, K.; Nagamani, C.This paper presents a comprehensive evaluation of proposed speed loop pseudo derivative feedback (PDF) controller based DTC with speed loop PI based direct torque controller (DTC) for permanent magnet synchronous motor (PMSM) drive. The proposed PDF-DTC system significantly improves dynamic response i.e. completely eliminates overshoot in speed, reduces 50% overshoot in electromagnetic torque and has two times faster settling time compared to PI-DTC system during step changes in speed with load disturbance. The proposed controller is verified for different cases viz., speed variation at constant load and variation in the load torque at constant speed. The proposed controller is implemented for 1.5 kW laboratory prototype PMSM drive using FPGA ALTERA cyclone II. Experimental results demonstrates the efficacy of the proposed controller. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.Item Efficiency improvement and torque ripple minimisation of four-phase switched reluctance motor drive using new direct torque control strategy(Institution of Engineering and Technology kvukmirovic@theiet.org, 2020) Pittam, P.K.; Ronanki, D.; Parthiban, P.The direct torque control (DTC) strategy is one of the most effective techniques, used to control the switched reluctance motor (SRM) with improved dynamic performance and reduced torque ripple. However, this approach draws a higher source current due to an extension of the phase current into the negative torque region, which lowers the net torque per ampere ratio. This study proposes a new DTC strategy for SRM to overcome this issue by modifying the partition of the sectors and appropriate voltage vector selection. Therefore, the proposed method improves the drive efficiency while minimising torque ripple. To implement this method, a non-linear machine model is developed using the torque and flux characteristics obtained from experimental studies on a four-phase 8/6 SRM. The proposed DTC scheme is implemented on a digital control platform and power loss calculations are performed to evaluate the drive efficiency. Test results show that the proposed DTC method has improved performance in terms of efficiency and torque ripple under various operating conditions in comparison to the conventional DTC strategy. © The Institution of Engineering and Technology 2019.Item Dynamic force modelling and experimental analysis of reaming(Engineered Science Publisher, 2021) Kamath, C.R.; Bekinal, S.I.; Bhat, R.; Naik, N.; Kuttan, A.The production Reaming process plays a vital role in several applications, ranging from automotive to medical sectors. It is performed to enlarge the pre-drilled hole to obtain its required diameter within the specified tolerance limits. The typical operational faults found in the reaming process significantly contribute to damage in the final hole quality. Thus, a dynamic force model is developed in the present work to predict the cutting forces developed during the reaming process. The inputs to the model are broadly classified into tool geometry and vibration system elements. The cutting forces acting in all three directions during the reaming are predicted. The double modulation principle is applied to develop the dynamic force model for computing the cutting forces in the reaming process. The dynamic force model thus developed and simulated using MATLAB® R2019b is examined and validated through actual experiments for no fault conditions. The results obtained infer a high degree of fitness between the values obtained from the developed mechanistic model and the experimental values with a prediction error of less than 5%. © 1999. The American Astronomical Society. All rights reserved.Item Design of bypass rotary vane magnetorheological damper for prosthetic knee application(SAGE Publications Ltd, 2021) Saini, R.S.T.; Chandramohan, S.; Sujatha, S.; Kumar, H.Semi-active systems using magnetorheological fluids have been realized in many novel devices such as linear dampers, rotary dampers, brakes, and so on. Rotary vane-type magnetorheological damper is one such device that uses magnetorheological fluid as a hydraulic medium and a controllable magnetorheological valve to generate variable resistance. This device, due to its limited angle motion, lends itself to a natural application for prosthetic knee joint. In this article, a bypass rotary vane-type magnetorheological damper suitable for prosthetic knee device is designed. In the proposed design, the rotary vane chamber and the bypass magnetorheological valve are connected using hydraulic cables and ports. The design of rotary cylinder is implemented based on the largest possible dimensions within the envelope of a healthy human knee, while the magnetorheological valve is designed optimally using a multi-objective genetic algorithm optimization. Off-state braking torque, induced on-state braking torque and mass of the valve are selected as three objectives. The torque and angular velocity requirements of the normal human knee are used as design limits. The optimal solution is chosen from the obtained Pareto fronts by prioritizing the objective of weight reduction of magnetorheological valve. The optimal solution is capable of producing a damping torque of 73 Nm at a design speed of 8.4 rpm and current supply of 1.9 A. Potential benefits offered by this design when compared with multi-plate magnetorheological brake are flow mode operation, large clearance gap, and fewer design components, thus reducing the manufacturing complexity. © The Author(s) 2020.Item Selection of optimal composition of MR fluid for a brake designed using MOGA optimization coupled with magnetic FEA analysis(SAGE Publications Ltd, 2021) Acharya, S.; Saini, T.R.S.; Sundaram, V.; Kumar, H.The design of Magnetorheological (MR) brake and the composition of MR fluid (MRF) used in it have a significant effect on its performance and hence an effort has been made in this study to determine the optimal dimensions of MR brake and composition of MRF suitable for the brake application. Initially, optimum parameters of MR brake were computed considering the properties of commercially available MRF 132DG fluid using multi-objective genetic algorithm (MOGA) optimization. This was performed in MATLAB software coupled with magnetostatic analyses in ANSYS APDL software. The braking torque of designed MR brake utilizing MRF 132DG fluid was experimentally determined and validated with analytical ones. Further, selection of optimal composition of MRF was done considering In-house MRF samples composed of different combinations of particle mass fractions, mean particle diameters and base oil viscosities. A design of experiments (DOE) technique was employed and braking torque corresponding to the synthesized MRF samples at different speeds and current supplied were measured along with the variation of shaft speed during braking process. Grounded on the experimental results, using MOGA optimization technique, MRF composed of smaller sized iron particles (2.91 microns) with mass fraction of 80.95% and lower viscosity base oil (50 cSt) was selected as optimal composition of MRF for use in MR brake. Maximization of field induced braking torque and minimization of off-state torque were chosen as the objective functions for both the optimal design of MR brake and selection of optimal composition of MRF. Finally, the sedimentation stability of MRFs were investigated. © The Author(s) 2020.Item Experimental investigation on potential use of drilling parameters to quantify rock strength(Springer, 2021) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.The uniaxial compressive strength (UCS) represents the strength of the rock. It frequently requires during the introductory phase of mining projects such as tunneling, rock excavation, blast hole designs, etc. Usually, the determination of UCS of rocks is carrying out in a concerned laboratory. The main drawback of determining the UCS in a laboratory requires at least five core samples of high-grade quality. Many problems and limitations are associated with removing the core, and also preparing the test specimen for UCS is tedious, time-consuming, and expensive. Therefore an attempt is made to develop an efficient indirect method to estimate the UCS of rocks without using the core samples. In this experimental investigation, the drilling response, such as thrust, is gathered by drill tool dynamometer considering the different drill operating parameters. The prediction model is developed with a regression technique using the measured thrust and calculated torque. The prediction capacity and validation of the model are carried out using the standard procedure. The experimental results show that the model could explain the variance in UCS up to 93.60%. RMSE and MAPE values in terms of percentage are 3.49% and 11.27%, respectively. Besides, the model's validation is checked for sandstone and limestone having the UCS 28 MPa and 35 MPa, respectively, and yielded the best prediction results with an error of 8.51% and 8.01% suggesting that the developed model could predict the UCS of sedimentary rock types within acceptable error limit, and reasonably. The correlation of UCS of rocks and drilling specific energy is also tested and found that linear relationship between them with an R2 value of 92.10%. © 2021, The Author(s).