Use of Globally Linearizing Control with Extended Kalman Filter for pH Control of a Wastewater Treatment Process (original) (raw)
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Comparison between backstepping and input–output linearization techniques for pH process control
Journal of Process Control, 2012
In this work performances of adaptive backstepping controller (BSC) and globally linearizing controller (GLC) are compared for pH control. First, based on the system full order model a GLC has been designed and it has been shown that this controller is identical to BSC proposed in the literature. Next in order to avoid state estimator design, BSC and GLC are designed based on pH reduced order model and their identities have been established. Through computer simulations, it has been shown that the performance of nonadaptive GLC designed based on reduced order model is better than that of adaptive BSC designed based on pH full order model which requires state measurement for implementation. Finally, the effectiveness of GLC designed based on the reduced order model in load rejection and set-point tracking has been demonstrated through simulation and experimental studies.
IPTEK The Journal for Technology and Science, 2007
The conventional PID control (linear) is popular control scheme that is used in almost pH control at waste water treatment process. pH model with respect to titration liquid flow rate has been known to be intrinsically difficult and nonlinear, especially when the process is conducted to non-linear range pH reference (pH 4-8), the settling time reach a long time. Therefore in this paper the nonlinear controller with self-tuning PID scheme is performed handle pH by training a neural-network based on backpropagation error signals. The pH process model is combination between CSTR (Continuous Stirred Tank Reactor) linear dynamic with H 3 PO 4 , HF, HCl, H 2 S flow rate and nonlinear static electro neutrality (wiener process model). The simulation result has a good and suitable performance under several tests (set-point and load change). The simulation result show the pH control system can follow the change of pH set-point and load with the average steady state error 0.00034. The settling time achieved at 50 second faster than conventional PID controller scheme.
Adaptive Nonlinear Control of a pH Neutralization Process
An adaptive nonlinear control strategy for a bench-scale pH neutralization system is developed and experimentally evaluated. The pH process exhibits severe nonlinear and time-varying behavior and therefore cannot be adequately controlled with a conventional PI controller. The nonlinear controller design is based on a modified input-output linearization approach which accounts for the implicit output equation in the reaction invariant model. Because the reaction invariants cannot be measured on-line and the linearized system is unobservable, a nonlinear output feedback controller is developed by combining the input-output linearizing controller with a reduced-order, open-loop observer. The adaptive nonlinear control strategy is obtained by augmenting the non-adaptive controller with an indirect parameter estimation scheme which accounts for unmeasured buffering changes. Experimental tests demonstrate the superior performance of the adaptive nonlinear controller as compared to a non-adaptive nonlinear controller and conventional PI controller.
Nonlinear model feedback linearization control strategy of a pH neutralization process
2014
In this work an approach based on nonlinear dynamics is used for the integrated design and controller tuning of a CSTR. The approach enables integrated design optimization and robust tuning of a linearizing feedback controller. The controller setting found by the approach guarantees robust stability of the process over a large range of set point variations even in the presence of parameter uncertainty. The method enforces robust stability by introducing lower bounds on the parametric distance of the operating point to critical boundaries in the space of process and controller parameters. For stabilization of a large range of operations, a lower bound on the distance to a nontransversal Hopf bifurcation has to be considered in this particular case.
Control of pH process using double-control scheme
Nonlinear Dynamics, 2011
Control of pH is mostly needed in continuous process industries and is difficult and challenging due to its time-varying and nonlinear nature of the chemical or biological process. Conventional controllers do not incorporate nonlinear dynamics of the entire pH range (both acid and alkali) and do not show good performance. Dynamics based on specific process nonlinearity of two different ranges is used to design double-control scheme in a feedback structure to enhance the performance of pH process. The mathematical model of pH for a weak acid-strong base is used to design IMC based PID double-controller scheme which provides outstanding set-point tracking and disturbances rejection simultaneously to control pH processes.
Experimental demonstration of non-linear model-based in-line control of pH
Journal of Process Control, 1992
A non-linear model-based control technique is developed and laboratory demonstrated for in-line acid neutralization using a multiple base injection approach. The controller chooses one of two simple, steadystate, three-parameter, non-linear phenomenological models which together mimic a wide range of titration curves from strong acid to highly buffered systems. The models are parameterized from on-line process data whenever nearly steady-state conditions are statistically identified. Results show excellent control performance in the presence of both ramp and step changes in acid type, acid concentration and flow rate upsets. Both industrial wastewater and mixtures prepared with acetic, phosphoric and sulphuric acids with and without common ion buffering and sodium carbonate were neutralized with sodium hydroxide in this study.
Engineering Journal, 2019
A model-based application for pH regulation in a pilot unit of wastewater treatment by carbon dioxide gas is presented. A reactor pH is an important factor to enhance the gas absorption of carbon dioxide bubbles in an alkaline wastewater, and it needs to operate within a tight pH range. Under a fed-batch operation mode, the reactor behavior has unstable dynamics resulting in a difficulty to achieve the pH target by manipulating the basic influent feed rate. To solve the problem, an input/output (I/O) linearization is applied because it provides excellent the setpoint trackability with a few numbers of tuning parameters required. The first principles approach is employed for reactor modeling. The model is then used in the I/O feedback formulation. Control performance is evaluated through a real-time implementation to track the desired pH target in comparison with a two-degree-of-freedom control scheme used as a compared case. The developed control system proficiently forces the output to the pH target and also improves the control performances.
Optimized PID Controller For pH Neutralisation Process
The common problem in pH reactors to determination and control and concerning chemical-based industrial processes by virtue of the non-linearity observed in the titration curve. The pH control had always drawn attention of chemical engineers because of its connotation in various fields as medicine, where the effect of pH on the enzymes and blood is acutely investigated, and the industry which is perturbed with manufacturing of textile dyes, and bleach products. The high non-linearity in pH is an immeasurable challenge in process control and it cannot be effective controlled by the linear PID controller. Hence advanced tuned PID controllers are best suited which are designed and developed for a pH control process in order to control the plant to the desired set point with high quality performance over the entire operating range. The mathematical model of pH process is obtained to ensure the dynamic modifications and stability enhancement. The ZN tuned PID, automatic tuned PID and PSO PID controller is implemented in simulation. The simulation is done using MATLAB software and the results are compared.
IInvention of a suitable controller for a non linear Chemical process
The nonlinearities form the obstacles to control the dynamic behavior of the neutralization process. In this paper fuzzy logic controller is designed. Th e fuzzy control is developed for a pH neutralization. The controller was set up for a plant. The fuzzy controller can avoid linearity problems that occur in the neutralization process. Thus the efficiency is improved using this technique. This technique forms the optimized technique for overcoming all non-linearities that occur in PH neutralization. The proposed fuzzy logic controller outperforms the usual PID controllers
Improvement of Activated Sludge Process Using Enhanced Nonlinear PI Controller
Arabian Journal for Science and Engineering, 2014
Wastewater treatment plant is a large-scale system and highly known with the nonlinearity of the parameters, making them a challenge to be controlled. In this paper, enhanced nonlinear PI (EN-PI) controller is developed for activated sludge process where a sector-bounded nonlinear gain with automatic gain adjustment is cascaded to conventional static-gain PI. The importance in controlling the dissolved oxygen concentration and the improvement of nitrogen removal process are discussed. The effectiveness of the proposed EN-PI controller is validated by comparing the performance of local control loops and the activated sludge process to the benchmark PI under three different weathers. The EN-PI controller is effectively applied in improving the performances of the static-gain PI, hence controlling the dynamic natures of the plant. It was proved by significant improvement in effluent violations, effluent quality index and energy saving of the Benchmark Simulation Model No.1.