Department of Electronics and Instrumentation Engineering
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Item Robust Decentralized Controller Design for Coupled Tank Systems(Department of Electronics and Instrumentation Engineering, NITS, 2022) M, PradeepThe majority of controllers in process industries is having either good set-point tracking or a good load disturbance rejection. While disturbance rejection is prioritized in pro cess industries, the controller’s dynamic performance is also important. The coupled tank system is one of the most common processes which is encountered in pharmaceutical, chemical, wastewater management, and petrochemical industries. The coupled tank system is a benchmark problem whose controller design is difficult since it is a non-linear, non-minimum phase TITO system. Moreover, the coupling effect of CTS will always offer several challenges for controller design. So the main goal of this work is to create a reliable decentralised controller for controlling the level of the liquid in coupled two-tank MIMO system that integrates both set-point tracking and the load disturbance rejection characteristics as well. For a simplified design and a simple analytical solution, the reduced-order model is obtained first by implementing model order reduction on the decoupled transfer function matrix. The decoupled matrix is of higher order and has a huge time delay. Hence, a FOPDT model of both decoupled tanks is obtained using the frequency curve fitting model order reduction technique. The decentralized PI controllers are designed using a variety of control strategies adopted from the literature. The Direct synthesis method in which the controller gain is analytically calculated by comparing the closed-loop transfer function of the plant and controller with the desired closed-loop transfer function. Next tuning of a decentralised PI controller gains based on desired Gain and Phase margin requirements is implemented for tank 1 and tank 2 respectively. A decentralized PI gain synthesis using a Genetic algorithm with maximum sensitivity as an objective function is implemented. The proposed work also includes the design of a decentralized controller that uses a linear quadratic regulator and Regional pole-placement using LMI (D-stability). Lastly, by altering the plant model’s gain and time constant, the robustness of the proposed controller is assessed in terms of model uncertainty.Item Modeling and Simulation Of Optimum Stored Charge In Sonos Flash Memory Using Silvaco Tcad(Department of Electronics and Instrumentation Engineering, NITS, 2022) Singh, SamdarThis paper presents the simulation of SONOS memory cells in SILVACO TCAD, varying the thicknesses of the nitride layer from 4 nm to 6 nm. The impact of the nitride layer and tunnel oxide layer thicknesses on the charge distribution in the floating nitride gate are explored, maintaining the gate voltage constant at 16 V. The spatial distribution of trapped electrons is estimated in the floating gate, which fluctuates when the thickness of the nitride layer is changed. For 'logic 0' states, with a 4th order transition time, a fluctuation of 17 % in net charge stored (4.4 10-15 C) is obtained in a 6 nm thick nitride layer. Moreover, a 1.5 nm thick tunnel layer allows 57 % net charge fluctuation in the 'logic 0' state with the 2nd order of transition time. A decrement in net stored charge is found by increasing the tunnel oxide layer thickness from 1.5 nm to 3 nm while keeping the nitride layer constant at 4 nm to 6 nm. The optimised thickness layer of both nitride and tunnel oxide model of SONOS is presented with electron concentration profiles at 'logic 1' and 'logic 0'. Furthermore, the optimised device was regressively studied to analyse threshold voltage and the thickness of the nitride layer varying from 4 nm to 6 nm. This analysis demonstrates the variation in threshold voltage from 3 V to 4.8 V, which is validated with an analytical model. This study evaluates the total net stored charge, the threshold voltage variation, and the data retention for ten years.Item Improved Coupled Electrothermal Model of Lithium-ion Battery(Department of Electronics and Instrumentation Engineering, NITS, 2022) Sinha, Shiv ShankarLithium-ion Batteries (LIBs) are popular and promising storage technology for auto mobile applications mainly due to their high energy density, low self-discharge property, and high cycle life compared to other rechargeable batteries. However, their performance is very susceptible to both low and high temperatures. In general, the range of temperature for its optimal performance is between 15-35°C. The temperature has ad verse effects on LIB whenever being operated beyond this range. High temperatures, in particular, have a more detrimental impact on LIBs. At times, when the internal temperature exceeds a certain threshold, the battery may experience unstoppable chain reactions called thermal runaway which leads to fire and explosion. Moreover, this process is accelerated at high charge/discharge currents. Therefore, in high current applications, monitoring the internal temperature of the battery becomes crucial for building an effective thermal management system to ensure safety while enhancing the performance of the battery. Hence, an Improved Coupled Electrothermal Model (ICETM) has been proposed with the primary aim of reducing the computational time and improving the accuracy of the internal temperature estimation of the battery at high currents. The proposed thermal model has two sub-models: a) heat generation model with an efficient methodology for the calculation of entropy change, and b) three-state heat dissipation model considering heat dissipation in radial and axial direction for better core temperature estimation at high charge/discharge current rate. The improved thermal model is coupled with the second order (2 R-C branches) electrical equivalent circuit model through temperature dependence of electrical parameters and heat generation. Furthermore, using the A123 ANR26650M1-B battery the parameterization process of the proposed ICETM is carried out through experimental and simulation studies. Finally, the model is validated using two different profiles: Urban Dynamometer Driving Schedule (UDDS) drive cycle profile; 6C Constant Current Constant Voltage (CCCV) charging followed by 6C Constant Current (CC) discharging profile. The proposed ICETM is well capable of identifying the entropy coefficient time efficiently and has the ability to accurately estimate the core temperature at a higher current rate as compared to the two-state thermal model.Item Internal Model Control Based Controller Synthesis for Two Tank System(National Institute of Technology, Silchar, 2026) Alam, SarfarazThis thesis presents the modeling and two control of a two-tank liquid level system using fractional order controller and gain scheduling techniques. In order to develop precise dynamic models that represent the nonlinear and dynamic behaviour of the process, system identification was carried out at several operational levels. Internal Model Control (IMC) principles were used to design a fractional-order PI (FOPI) controller based on these identified models, which offers more robustness and more tuning flexibility than the traditional integer-order PI controller. Faster settling, less overshoot, and a strong disturbance-rejection capability was shown by the fractional controller, indicating that it is suitable for processes with time delay and parameter fluctuations. A gain-scheduling framework was designed to handle performance fluctuations over the operating range. IMC-based tuning was used to generate different PID controllers once five operational points were chosen. In order to guarantee seamless transitions and reliable closed- loop behaviour, the scheduler adjusted the controller gains in real time based on the tank level. In comparison to a single fixed controller, simulation experiments showed that the gain- scheduled PID performed better tracking and disturbance rejection, especially when challenged to step disturbances at 100 seconds. Overall, reliable and flexible control framework for the two-tank system was produced using both fractional-order control and gain-scheduling techniques. These techniques allow the controller to manage changes in operational condition without changing performance. For nonlinear, time-varying, and operating-point-dependent industrial processes, the both methods provide a practical and affordable solution.Item Development of an Automated Electric Servo Press Machine(National Institute of Technology, Silchar, 2026) Das, Keshar Jyoti