61 research outputs found
A nonlinear model-based control scheme for benchmark industrial processes
No full textOver the last two decades, model-based control schemes have been widely used for designing industrial control systems especially in process control industries. In this paper, a nonlinear model-based control scheme has been proposed for benchmark industrial processes. The scheme also uses adaptive control strategy for better tuning the controller gains. The proposed framework is applied to control the liquid level of a spherical tank, which is a benchmark nonlinear industrial process. Reference tracking and disturbance rejection performance have been tested via simulation results and the performance of the proposed scheme has been compared with the classical adaptive PI controller. Simulation results shows that the proposed scheme ensures closed-loop stability and maintains satisfactory performance in presence of parameter variation.</p
Parameter estimation and its application in tuning PI control scheme
No full textIn this paper, Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) based robust adaptive PI Control Scheme have been proposed and implemented on the simulated model of the non-linear benchmark processes. The servo and regulatory performance using proposed tuning methodologies were found satisfactory. The performances of the proposed control schemes have been compared with conventional adaptive PI (CA-PI) control scheme. From the extensive simulation studies, it was found that the proposed schemes implemented on non-linear processes are having better performance over CA-PI control scheme. It was also found that proposed control schemes are able to eliminate measurement noise and having good robustness features.</p
Model-based adaptive control scheme for benchmark pH-neutralisation process
No full textControl of pH has always been a critical task because of the highly complex nonlinear characteristic of the titration curve. This paper is concerned about the design of an adaptive nonlinear model-based tracking control scheme and its application in a benchmark pH-neutralisation process. The scheme exploits a deterministic process model to generate the model state which reflects the actual process dynamics, and utilises three different adaptive tuning methods to update the controller gain on real-time basis. Simulation results show that the proposed scheme ensures closed-loop stability and facilitates satisfactory set-point tracking (both time-varying and constant) performance despite parameter variation, exogenous disturbance and measurement noise. </p
A nonlinear model-based control scheme for pH-neutralisation process
No full textControl of pH has always been a critical task because of the highly complex nonlinear characteristic of the titration curve. This paper is concerned about the design of an adaptive nonlinear model-based tracking control scheme and its application in a benchmark pH-neutralisation process. The scheme exploits a deterministic process model to generate the model state which reflects the actual process dynamics, and utilises three different adaptive tuning methods to update the controller gain on real-Time basis. Simulation results show that the proposed scheme ensures closed-loop stability and facilitates satisfactory set-point tracking (both time-varying and constant) performance despite parameter variation, exogenous disturbance and measurement noise. </p
The optimal electrode pore size and channel width in electrochemical flow cells
No full textMicrofluidic fuel cells, electrolyzers, and redox flow batteries utilize laminar flow channels to provide reactants, remove products and avoid their crossover. These devices often also employ porous flow-through electrodes as they offer a high surface area for the reaction and excellent mass transfer. The geometrical features of these electrodes and flow channels strongly influence energy efficiency. We derive explicit analytical relations for the optimal flow channel width and porous electrode volumetric surface area from the perspective of energy efficiency. These expressions are verified using a two-dimensional tertiary current distribution and porous electrode flow model in COMSOL and are shown to be able to predict optimal parameters in commonly used flow-through and interdigitated flow fields. The obtained analytical models can dramatically shorten modelling time and expedite the industrial design process. The optimal channel width and pore sizes we obtain, in the order of 100 microns and 1 micron respectively, are much smaller than those often used. This shows that there is a significant room for improvement of energy efficiency in flow cells that can sustain the resulting pressure drop.</p
Pulsatile Flows: Experimental Investigation of fully turbulent pulsatile pipe flows
No full textTurbulence is a commonly encountered state of fluid dynamics. Unsteady turbulent flows in pipes are present in many engineering applications and also in biological flows. However, the various processes active in such flows are not well understood. The present work employs stereo-PIV to investigate the effects of a sinusoidal pressure gradient on the various turbulence parameters, including the terms of the turbulent kinetic energy budget equation. The bulk flow rate was oscillated with a frequency of 0.5 Hz with a mean Re 26,000 and an amplitude of modulation, 0.23 times the mean value. It is seen that there is a delay in the response of turbulence to the oscillations of the bulk flow and the delay increases with increasing distance from the wall. The axial and the in-plane turbulence parameters show a difference in the delay of their responses. This delay extends into the small scales responsible for the dissipation of turbulent kinetic energy. Changes are also observed in azimuthal length scales when the flow oscillates.The effects of oscillation on the streaks of low momentum are also discussed and the structural organization in unsteady pipe flows are found to be different from that in steady pipe flow
A model-based tracking control scheme for nonlinear industrial processes involving joint unscented Kalman filter.
No full textThis paper proposes a model-based reference tracking scheme for stable, MIMO, nonlinear processes. A Joint Unscented Kalman Filtering technique is exploited here to develop a stochastic model of the physical process via simultaneous estimation of the process states and the time-varying/uncertain parameters. Unlike the existing nonlinear model predictive controllers, the proposed scheme does not involve any dynamic optimisation process, which helps to reduce the overall complexity, computation overburden and execution time. Furthermore, the proposed methodology offers robustness to process model-mismatch and considers the effects of stochastic disturbances. A nonlinear two-tank liquid-level control problem and a nonlinear coupled level-temperature control process are studied to demonstrate the usefulness of the proposed scheme
Effects of CDS and drying temperature on the flowability behavior of DDGS
No full textDue to increasing demand for alternative fuels and theneed to reduce dependence on fossil fuels, the growth of bioethanol production has been rising. One of the problems facing this industry is transportation of the coproduct dried distillers grains with solubles (DDGS) over long distances, because caking and agglomeration between particles can lead to bulk flow problems. In this study, DDGS was prepared by combining condensed distillers solubles (CDS) and distillers wet grains (DWG) and then oven drying to achieve 8% (db) moisture content. The effects of drying temperature (100, 200, and 300°C) and CDS (10, 15, and 20%wb ) level on the resulting flowability behavior of the DDGS particles were investigated. Statistical analyses indicated significant differences (α = 0.05, 95% confidence level) due to drying temperature and CDS main effects and significant interaction effects between CDS level and drying temperature for many of the flow parameters. Surface regression analysis of the ratio of total flow index/Jenike flow function as a function of CDS and drying temperature resulted in an R 2 value of 0.94. Partial least squares (PLS) regression yielded an R 2 of 0.90 for the Jenike flow function index as a function of all flow and physical properties using only two multivariate components. Understanding the effects of varying drying temperatures and CDS levels can help guide efforts to overcome DDGS flowability problems
Design and application of nonlinear model‐based tracking control schemes employing DEKF estimation
No full textThis paper deals with the design and application of nonlinear model-based control schemes for stable and nonlinear benchmark industrial processes. The primary control objective is to facilitate set-point (constant/time-varying) tracking in the presence of external disturbances, process noise, measurement noise, parametric uncertainty, and model mismatch. We first propose a “noninferential-type” model-based control scheme which involves a finite-dimensional, nonlinear, and deterministic process model to generate the model states. Secondly, an “inferential-type” model-based control scheme has been introduced particularly to take into account the stochastic uncertainties such as process noise and measurement noise. The second scheme exploits the dual extended Kalman filter for estimating the immeasurable states and the process parameters through which disturbance is injected. Unlike fixed-parameter controllers, the proposed schemes update the controller gains at each step depending on the real-time process gains. In order to demonstrate the usefulness of the proposed closed-loop tracking control schemes, two exhaustive case studies have been carried out on the CSTR and Van de Vusse reactor processes, which are considered to be benchmark industrial processes due to highly nonlinear and unpredictable behaviour and due to nonminimum phase property. Finally, the performance of the proposed schemes are compared with an EKF-based adaptive PI control framework and the simulation results reveal that the transient performance of the proposed schemes are better than that of the aforementioned PI technique especially in perturbed condition (ie, in presence of model mismatch and measurement noise).</p
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