Department of Electrical and Electronics Engineering
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Item Stiction combating intelligent controller tuning: A comparative study(IEEE, 2015) Mishra, PuneetThis paper investigates the effects of different controller tuning approaches on an intelligent controller, namely Stiction Combating Intelligent Controller (SCIC) earlier developed by the authors. The SCIC controller is inherently a variable gain fuzzy Proportional-Integral (PI) controller based on Takagi-Sugeno model and was specifically designed to handle the stiction nonlinearity in a control loop in presence of a sticky pneumatic control valve. Three different tuning methods, viz. Ziegler-Nichols, Tyreus-Luyben and Direct synthesis (DS) tuning approach, which are extensively employed in process industries to tune Proportional-Integral-Derivative controllers, are tested in this work to find the gains of SCIC and PI controller. The performance of both, SCIC and PI controllers, are rigorously evaluated experimentally on a laboratory scale nonlinear flow process for setpoint tracking, disturbance rejection, and robustness testing. Based on extensive experimental analysis it can be concluded that the SCIC controller tuned using DS approach performed best for almost all cases.Item A comparative study for flow control using SCIC and NPIC controllers(IEEE, 2017) Mishra, PuneetFlow control is essentially a very important part of the process control industries. The flow control loops often employ pneumatic control valves as the final control element. These control valves suffer from various nonlinearities and stiction is most common of these. Due to stiction effect in the pneumatic control valves, the commonly used proportional-integral-derivative (PID) controller introduces limit cycles in the flow control loops, which essentially deteriorates the productivity of the industrial environment. To curb such non sinusoidal oscillations in these control loops, recently two novel controllers have been proposed namely, Stiction Combating Intelligent Controller (SCIC) and Nonlinear Proportional Integral Controller (NPIC). These two controllers have been earlier thoroughly evaluated for flow control studies and are claimed to be very efficient for curbing the limit cycle behavior in the control loops. However, a comparative study between them is missing for the same, which would fill the void existing at present. This paper addresses the same issue and a comparative study between the two controllers is performed and presented in this paper for the setpoint tracking, disturbance rejection and parametric uncertainty problems.Item A novel intelligent controller for combating stiction in pneumatic control valves(Elsevier, 2014-12) Mishra, PuneetPneumatic control valve introduces limit cycles in process variables due to stiction nonlinearity. In this paper a novel stiction combating intelligent controller (SCIC) based on fuzzy logic has been proposed. The proposed technique reduces the complexity of the overall control scheme as it does not require any additional compensator. The SCIC controller is a variable gain fuzzy Proportional Integral (PI) controller making use of Takagi-Sugeno (TS) scheme. The performance of the SCIC controller has been investigated and compared with conventional PI controller on a laboratory scale flow process. SCIC controller outperformed PI controller and provided promising performance with lesser aggressive stem movement.Item An online tuned novel nonlinear PI controller for stiction compensation in pneumatic control valves(Elsevier, 2015-09) Mishra, PuneetA novel Nonlinear PI Controller (NPIC) has been proposed for effective control of flow process employing a sticky pneumatic control valve. The proposed control scheme has been inherited from a classical PI control structure with a difference that the integral gain has been varied in accordance with the instantaneous error and the rate of change of error. The tuning of controller has been carried out online using Differential Evolution algorithm. To evaluate the effectiveness of the proposed controller, a comparative study with the conventional PI controller has also been carried out for the setpoint tracking, disturbance rejection and robustness to parameter uncertainties on account of operating point change on a laboratory scale nonlinear flow process. Based on these intensive experimental evidences, it has been concluded that the NPIC performed far better than the conventional PI controller for all the case studies and suppressed effectively any stiction induced oscillations.Item A Robust Fractional Order Parallel Control Structure for Flow Control using a Pneumatic Control Valve with Nonlinear and Uncertain Dynamics(Springer, 2018-06) Mishra, PuneetControl of flow rate in industrial plants is an essential and crucial task, which is usually achieved by pneumatic control valves in industries. Use of these valves often incorporates nonlinear and uncertain dynamics in the control loop on account of its input-output characteristics, which may result in degradation of control loop performance. To address this concern, a robust and improved fractional order parallel control structure (FOPCS) for flow control is proposed in this paper. The proposed FOPCS is an extension of parallel control structure (PCS) with the help of fractional order calculus, to enhance the robustness in the control loop without compromising with control performance. Also, a global optimization technique, backtracking search algorithm was further employed to critically tune the parameters of control structures. This was done in order to obtain an optimized and enhanced performance from the control loop. Extensive runtime studies on a laboratory scale plant, using advanced data acquisition facilities, were carried out to showcase the effectiveness of developed FOPCS. Proposed FOPCS is thoroughly assessed in terms of servo, regulatory and robustness performance. A quantitative comparison of FOPCS with PCS is also made on the basis of integral of absolute error, integral of absolute rate of controller output and their algebraic summation. All the conducted experimental studies suggested that proposed FOPCS was able to address the issues pertaining to uncertain and nonlinear behaviour of pneumatic control valve in the flow control loop.