Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884
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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 Comprehensive Evaluation of Iron Ore Tailing and Cement Treated Lithomargic Soil for Pavement Application(Springer Science and Business Media Deutschland GmbH, 2025) Satheesh, A.; Sridhar, S.Lithomargic soil, extensively found along the coastal regions of Karnataka, India, is inherently weak with a low California Bearing Ratio (CBR) value and hence, unsuitable as a subgrade or sub-base material in a pavement. To utilize the lithomargic soil as a subgrade or sub-base material, the present study focuses on its stabilization using Iron Ore Tailing (IOT) and cement. IOT, collected from Kudremukh region, Karnataka, India, was assessed for its suitability in pavement stabilization, with proportions ranging from 10 to 50%. Lithomargic soil stabilized with optimum proportion of IOT was subsequently treated with cement, with proportions ranging from 2 to 12% and in increments of 2%. Compaction test, CBR test, Unconfined compression test and durability tests were carried out on lithomargic soil stabilized by IOT alone and both IOT and Cement. Furthermore, X-ray Diffraction, Field Emission Scanning Electron Microscope and Fourier Transform Infrared Spectroscopy analyses were carried out to understand the stabilization mechanisms. Optimal results were obtained for lithomargic soil treated with 20% IOT. The unconfined compression test revealed that the soil-IOT mix satisfied the strength requirements for a subbase material with 6% cement, whereas lithomargic soil alone required 8% cement content to meet the strength requirements. Incorporating 2% cement into the soil-IOT mix enhanced the CBR to 31%, up from 2% for lithomargic soil, satisfying subgrade requirement. All stabilized mix containing more than 2% cement met the durability requirements for 12 cycles of wet-dry and freeze-thaw. The microstructural analyses showed cementitious compounds within the soil structure, indicating the formation of hydration products along with additional hydroxyl compounds. The pavement design and analysis for high-volume roads was carried out as per IRC: 37-2018 and IITPAVE software and results indicate 28% reduction in design pavement thickness and a reduced maximum deflection value after stabilization. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.