Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 AENSI Journals Australian Journal of Basic and Applied Sciences ISSN:1991-8178 Journal home page: www.ajbasweb.com Performance Testing of Non-Linear pH Neutralization Using Bacterial Foraging Algorithm 1 M.Kandasamy and 2Dr.S.Vijayachitra 1 Department of Electronics and Instrumentation Engineering, Erode Sengunthar Engineering College, Erode -638057, India. Department of Electronics and Instrumentation Engineering, Kongu Engineering College, Erode -638052, India 2 ARTICLE INFO Article history: Received 25 April 2014 Received in revised form 8 May 2014 Accepted 20 May 2014 Available online 17 June 2014 Keywords: Bacterial Foraging Algorithm, pH neutralization, performance indices, first order plus time delayed (FOPTD) system, Textile waste water Treatment. ABSTRACT Background: PID controllers are widely used in process industries to control linear, non linear, stable and unstable systems. Selection of proper PID controller tuning method and controller structure helps to improve the performance of the system. Textile industry waste water process is highly non linear and complicated due to more number of parameter variations. Objective: In this paper, Bacterial Foraging optimization (BFO) Algorithm based PID controller design procedure is proposed for a pH neutralization process widely employed in Textile waste water Treatment units. Results: The efficiency of the proposed method is validated through a comparative study with Ziegler-Nichols Method and Relay feedback Method. Also, the BFO Algorithm is implemented on parallel PID controller, I-PD controller and set point filter type PID controller in order to identify the best suitable controller structure for the pH neutralization process. Conclusion: The BFO based set point filter type PID controller shows an improved system performance compared with the parallel type PID controller and I-PD controller considered in this study. The BFO based set point filter type PID controller offers better set point tracking, load disturbance rejection, improved time domain specifications, and minimal error compared to the alternatives considered in this paper. © 2014 AENSI Publisher All rights reserved. To Cite This Article: M.Kandasamy, Dr.S.Vijayachitra., Performance Testing of Non-Linear pH Neutralization Using Bacterial Foraging Algorithm. Aust. J. Basic & Appl. Sci., 8(10): 62-71, 2014 INTRODUCTION Textile industry process is more complicated due to the presence of variety of raw materials, products, processes and instruments. After the array of sub-processes like bleaching, dyeing, printing and stiffening, the raw material (fibre) will reach the desired finishing product. In this, many of the sub-processes are wet processing and the use of huge volume of water has become the reason for discharging high volume of effluent. This effluent possesses broadly fluctuating pH, high range of Bio Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Suspended Solids (SS) and rich in Color. The presence of toxic and non-biodegradable organic pollutants in the waste water is the biggest challenge for sustaining the environmental safety. Also due to water scarcity, the high volume of waste water is treated effectively for re-usage to reduce the operational cost of the textile industries. Most pollutants in textile wastewater are weak organics acid or base, so the pH value of wastewater can influence the property of pollutants. The pH in the range of 4 to 11 for treatment of textile industrial wastewater is neutralized by using either H2SO4 or NaOH to adjust the pH of the solution (Nordin et al., 2013). Studies on pH-neutralization dynamics and control are started in the year 1970 (McAvoy et al., 1972; Buchholt et al., 1979). Since the process is highly nonlinear characteristics and uncertainty, research is still reported by many scholars but using recent emerging control strategies (Chen et al., 2011). The waste water treatment is existed in many chemical process industries and perfect practical control is yet been identified including for pH neutralization. In spite of some successful practical applications, there still is no all-inclusive procedure or method to design such intelligent controllers by far because of its semi-empirical nature. (Wan et al., 2010) More research is carried out for modeling the Non Linear system by variety of methods including firstprinciple approach (Patwardhan and Madhavan, 1998). Many efforts have been attempted to design a nonlinear black-box model with a merit of simple procedure, however selection of an exact model structure to capture nonlinear dynamics over a wide operating range is difficult in the nonlinear black-box model. Proportional, Integral, Derivative (PID) controllers are widely used in process control applications for the kind of stable, unstable and nonlinear processes due its simplicity and performance characteristics Corresponding Author: M. Kandasamy, Department of Electronics and Instrumentation Engineering, Erode Sengunthar Engineering College, Erode -638057, Tamil Nadu, E-mail: [email protected] 63 M. Kandasamy and Dr. S. Vijayachitra, 2014 Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 (Rajinikanth and Latha, 2011; 2012; 2012a). The I term ensures robust steady-state tracking of step input and P & D terms provide stability and desirable transient behavior of the system. In control literature, many efforts have been attempted to design optimal controllers for non linear process control systems. Nuella et al., (2009) have proposed a method of an adaptive Proportional+Integral +Derivative (PID) controller design for nonlinear process control and in this, the PID parameters are obtained from controller database according to the current process dynamics characterized by the information vector at each sampling instance. Kim and Oh (2000) have suggested a nonlinear fuzzy PID control method, which can stably improve the transient responses of systems disturbed by nonlinearities or unknown mathematical characteristics. Also, Christoph Hametnera et al., 2013 have proposed discrete-time local model networks for PID controller design for nonlinear systems. Most preferred and widely accepted PID Controller tuning methods such as Ziegler -Nichols (Z-N) Method (Ziegler and Nichols, 1942), Relay feedback Method (Astrom and Hagglund, 1984) are extensively addressed by the researchers to solve complex process control engineering problems. Passino (2002) has proposed the BFO algorithm based adaptive controller for a liquid level control problem. The perception of foraging activities of Escherichia coli (E. coli) bacteria is used for the optimization technique to find out the best fitted PID controller parameters by a set of artificial bacteria in the “D” dimensional search space. Many attempts by researchers have been carried out to find the optimal controller parameters using Bacterial Foraging Algorithm for different categories of engineering optimization problems ( Biswas et al., 2010;Chen et al., 2011). In the proposed work, the performance of pH neutralization process is tested by using PID controller and the PID parameters are tuned by various methods such as Ziegler -Nichols (Z-N) Method, Relay feedback Method and Bacterial Foraging Algorithm (BFO) method. This work indicated that performance of the BFO algorithm based PID controller is better than Z-N method and relay feedback method. Later, the BFO algorithm is implemented on parallel PID controller, I-PD controller and Set point filter PID controller to find out best controller structure for the pH neutralization process. Finally a comparative study on optimal performance indices such as Integral of Squared Error (ISE), Integral of Absolute Error (IAE), Integral of Time-weighted Squared Error (ITSE), Integral of Time weighted Absolute Error (ITAE), Rise Time (tr), Peak Time (tp), Percentage of Peak Overshoot (Mp) have been carried out. The paper is organized as follows: Section 2 provides the design structure of parallel PID, I-PD and Set point Filter PID controllers. The section 3 presents the PID controller tuning by Z-N method, Relay feedback method and BFO algorithm method. Section 4 presents an overview of BFO algorithm. The simulated results of process model of the pH neutralization process is discussed in the section 5 followed by the conclusion of the research work in Section 6. PID Controller Structures: In process industries, PID controllers are implemented to obtain better steady state and transient response as well as to maintain stability, smooth reference tracking and load disturbance rejection of the process. In a closed loop control system, the controller continuously adjusts the final control element until the difference between reference input and the process output is zero irrespective of the internal and/or external disturbance signal (Panda, 2009). Mathematical Model of an ideal PID controller is presented below: Gc(s) = k 1 1 s p d is and it can be modified as K K p i Kd s s Where, Integral Time K p and Derivative Time K d i d Ki Kp (i) Parallel PID Controller Tuning: Fig. 1: Block diagram of closed loop control systems. (1) (2) 64 M. Kandasamy and Dr. S. Vijayachitra, 2014 Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 Fig. 2: Block diagram of Parallel PID control systems. The Fig. 1 shows the basic block diagram of closed loop control systems. In this, G c(s) is the PID controller and Gp(s) is the process to be controlled. Also the R(s) is reference signal; Y(s) is controlled (output) signal; E(s) is error signal; Uc(s) is controller output; A simple PID controller is act as controller „G c(s)‟ to control the process. The Fig. 2 shows the structure of basic parallel PID controller. The following mathematical models of parallel PID controller structure described in the equations (3) and (4) are used in most of the process and considered for this study. K G C (s) K p i K d s s (3) The controller output is given as T U C (t) K p e(t) K i e(t) dt K d 0 de(t) dt (4) (ii) I-PD Controller Tuning: I-PD controller is customized version of PID Controller. The demerit of the parallel PID structure is, when a step signal is given as reference signal „R(s)‟ to the controller, it will produce immediate spike as output. This abrupt change in the controller behavior is called as proportional and Derivative kick. These unwanted kick effects suddenly cause the entire process „Gp(s)‟ into more critical. This drawback is eliminated by the implementation of I-PD controller which is shown in Fig. 3. In this structure, the integral term alone acting on the error signal „E(s)‟ and the abrupt change in the reference signal „R(s)‟ will not affect the proportional and derivative terms since these two terms are acting on output of the system „Y(s)‟. This I-PD controller is widely preferred in the industries to get smooth set point tracking due to the absence of the „kick effect‟. The output of the I-PD controller is given in the equation (5) U C (t) K i T 0 d y(t) e (t) dt - K p y(t) K d dt (5) Fig. 3: Block diagram of I-PD control systems. (iii) Set point Filter PID Controller Tuning: Peak Over shoot is one of the most important specifications in all the process plants. The system that produces high overshoot is not preferred because; large overshoot brings the process into worst scenario. Set point filter PID controllers are widely used in the industries to limit the value of overshoot (Vijayan and Panda, 2012; 2012a). A set point filter is added with the parallel PID to obtain the filter PID controller. 65 M. Kandasamy and Dr. S. Vijayachitra, 2014 Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 Fig.4: Block diagram of filter PID control systems. The Fig. 4 shows the basic structure of the set point filter PID and the equation (6) provides the mathematical model, 1 d s 1 (6) K p 1 is d s 1 f s 1 Where, α is derivative filter Constant and it is assigned as 10 in this study. f is set point filter parameter and its value obtained as f = Kp/Ki (Jung et al., 1999). Where KP and Ki are proportional gain and Integral gain of the controller respectively . Tuning of PID Controllers: The following controller tuning process is used to find the best optimum values of K p, Ki, Kd to confirm the minimum time domain specifications and error values in this study. (i) Ziegler and Nichols Method: In 1942, Ziegler and Nichols have proposed simple mathematical procedures for tuning PID controllers. These procedures are widely accepted and treated as standard in control systems practice. In this method, Integral gain Ki and derivative gain Kd are set with zero and proportional gain Kp is increased to specific critical value to make sustained oscillation output. From the procedure, the optimum controller parameters for the PID controller is obtained (ii) Relay feedback Method: Astrom and Hagglund (1984) suggested the relay feedback test to generate sustained oscillations as an alternative to the conventional continuous cycling technique. Since it is the closed loop test, the process will not drift away from the nominal points as well as it identifies process information around the important frequency to obtain the controller parameters. (iii) Bacterial Foraging optimization (BFO) Method: Initially, the boundary values of PID is to be assigned to guide the optimization algorithm and to attain the good accuracy. Many researchers have proposed the Multiple Objective Performance Index (MOPI) such as overshoot (Mp), settling time (ts), steady state error (ess), rise time (tr), gain margin (GM) and phase margin (PM) for PID controller optimization (Rajinikanth and Latha, 2012b; Zamani et al., 2009). The following equation describes the parameters selected for MOPI to find the controller Parameter K p, Ki and Kd by BFO algorithm. Jmin(Kp,Ki,Kd) = (w1 · ISE) + (w2 · IAE) + (w3 ·Mp) + (w4 · ts) + (w5 · tr ) (7) Where Jmin (Kp,Ki,Kd) - Performance criterion ISE - Integral Square Error IAE - Integral absolute Error Mp = Peak Overshoot is the difference between maximum peak value of the response curve c(tp) and final value of c(t) ts = Settling time is time required for the response curve to reach and stay within 2% of the final value. tr = Rise time is time required for the response to rise from 0% to 100% of its final value. w1, w2, w3, w4 and w5 are weighting functions of the MOPI parameters and the value of “w” varies from 0 to 10. Fig. 5: BFO algorithm-based PID controllers tuning. 66 M. Kandasamy and Dr. S. Vijayachitra, 2014 Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 The Fig. 5 shows the basic structure of BFO algorithm based PID controller tuning controllers tuning. The similar modified structure can be obtained to incorporate BFO based I-PD controllers tuning and set point Filter PID. The following parameters are assigned to BFO and MOPI as the preliminary process for optimization search. Dimension of the search is assigned as three ( K p, Ki, Kd); number of E. coli bacteria as is ten; number of reproduction steps is assigned as four; length of a swim considered as four ; number of chemo tactic steps is selected as five; number of elimination-dispersal events are considered as two; number of bacterial reproduction is set as five, probability for bacteria eliminated /dispersed is considered as „0.25‟; d att is assigned as zero ; Watt is set as „0.5‟ hrep is considered as „0.6‟ and Wrep is assigned as „0.6‟. • The limits of the three dimensional search space is as Kp = 0% < Kp < +50% Ki = 0% < Ki < +25% Kd = 0% < kd < +50% • The weighting function values are assigned as w1 =w2 = w3 = 10, w4 = w5 = 6. • The reference input signal „R(s)‟ is unity. • The “tr” is chosen as <25% of the maximum simulation time. The settling time „t s‟ is selected as <50% of the maximum simulation time. • The overshoot in the process output „Mp‟ is considered as <10% of the reference signal. • The steady state error (ess) of process output is assigned as zero. • Maximum simulation time is 100 sec. The simulation time is selected based on the process time delay. • Ten trials are carried out for each algorithm and among them best value is considered as suitable optimized controller value. Bacterial Foraging Optimization Algorithm: Bacterial Foraging Optimization (BFO) algorithm is a new division of biologically inspired computing technique introduced by Passino in 2000. It is based on mimicking the foraging methods for positioning, handling and ingesting food behaviour of Escherichia coli (E. coli) bacteria living in human intestine. The algorithm has an advantage of high computational efficiency, simple design procedure, and stable convergence. The flow chart shown in Fig. 6 is brief about the BFO algorithm and its basic operations with key process. Fig. 6: Flow chart for bacterial foraging algorithm. Chemo-taxis: This process simulates the movement of an E.coli cell towards the food source with swimming and tumbling action via flagella. The bacteria can move in a particular path by swimming and can modify the 67 M. Kandasamy and Dr. S. Vijayachitra, 2014 Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 direction of search during tumbling action. These two modes of operations are endlessly executed by a bacteria its whole lifetime to reach the sufficient amount of positive nutrient gradient. Swarming: This process is carried out by the bacteria to acknowledge the information about optimum path of the food source with other bacteria. An attraction signal is produced for this communication between the cells in the Ecoli bacteria. Another repellent signal is also produced for noxious reserve. This process helps them to increase the bacterial density at the identified food position in the chemotaxis. The attraction signal is represented by the below equation (8). s J cc ( (i, j , k , l )) J cc ( , i ( j , k , l )) X Y i 1 Where s n X d att exp watt ( m mi ) 2 and i 1 m1 (8) s n Y hrep exp wrep ( m mi ) 2 i 1 m 1 Where “s” = Total number of bacterium, “n”= Total parameters to be optimized, datt = Depth of attractant signal released by a bacteria, “Watt” = Width of attractant signal, “hrep” = height of repellent signals between bacterium, “Wrep” = weight of repellent signals between bacterium and J cc(θ,(i,j,k,l)) is the objective function value. “θ” is the point in the n dimensional search domain till the jth chemotactic, kth reproduction and lth elimination. Also “θm” is the mth parameter of global optimum bacteria Reproduction: In swarming process, the bacteria gathered as groups in the positive nutrient gradient and which may increase the bacterial density. Later, the bacteria are arranged in descending order based on its health values. The least healthy bacteria eventually expire while healthier bacteria asexually split into two bacteria and maintain the predefined population. Elimination-Dispersal: This is the closing phase in the bacterial search. The bacterium population may decrease either gradually or suddenly depend on the environmental criteria such as change in temperature, and availability of food etc. Significant local rise of temperature may kill a group of bacteria that are currently in a region with a high concentration of nutrient gradients. Actions may take place in such a way that all the bacteria in a location are killed and eliminated (local optima) or a group is relocated (dispersed) into a new food source. The dispersal possibly compresses the chemo-taxis advancement. After dispersal, some bacteria may be located near the superior nutrient and this process is called “Migration”. The above events are continued until the entire dimensional search converges to optimal solutions or total number of iterations is reached RESULTS AND DISCUSSIONS The closed loop performance of the pH neutralization is analysed with BFO based controllers by using mathematical model of the process from literature (Meenakshipriya et al., 2012). The pH neutralization process considered for the proposed analysis is shown in Fig. 7. In this, pH is controlled by controlling the flow rate of acid due to alkalinity nature of textile waste water. The mathematical model obtained for the process is given in the equation (9) G (s) 7.0921 e 1.71s 8.54 s 1 Fig. 7: pH neutralization system. (9) 68 M. Kandasamy and Dr. S. Vijayachitra, 2014 Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 For analysing the performance of pH neutralization process, the PID controller parameters (Kp, Ki, Kd) are obtained by Z-N method, Relay Feedback method and BFO algorithm and their performance are taken into consideration. The table 1 shows the performance indices of Z-N method, Relay Feedback method and BFO algorithm method. Table1: Performance indices of different PID controller tuning. % of Mp tr (sec.) ts (sec.) Z-N 93.2 4.2 45.0 Relay 81.0 4.5 35.0 feedback BFO 34.0 5.05 12.0 Algorithm IAE 10.57 8.03 ISE 6.02 4.67 ITAE 112.30 63.20 ITSE 35.65 20.44 4.397 2.91 15.56 5.38 2 1.8 Reference Tracking 1.6 1.4 1.2 1 0.8 0.6 Set Point 0.4 BFO-PID ZN-PID Relay-PID 0.2 0 0 10 20 30 40 50 60 Time (sec) Fig. 8: Comparison of Servo Response of different PID Controllers Tuning. 1 Controller Output 0.5 0 BFO-PID -0.5 0 10 20 30 Time (Sec) ZN-PID 40 Relay-PID 50 60 Fig. 9: Comparison of Controller response for different PID Controllers Tuning. 2.5 Reference Tracking 2 1.5 1 0.5 Set Point 0 -0.5 0 20 40 60 80 BFO-PID 100 ZN-PID 120 Relay-PID 140 160 Time (sec) Fig. 10: Regulatory Response for different PID Controllers Tuning. 1 0.8 Controller Output 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 BFO-PID ZN-PID Relay-PID -0.8 -1 0 20 40 60 80 100 120 140 160 Time (sec) Fig. 11: Controller output for Regulatory Response of different PID Controllers Tuning The performance of a controller can be tested by mode of servo control and regulatory control. In the servo control mode, the objective of controller is to provide accurate tracking of reference signal. The Fig. 8 and Fig. 9 show the servo response of the different PID controllers and corresponding controller output respectively. The 69 M. Kandasamy and Dr. S. Vijayachitra, 2014 Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 set point tracking (Servo Response) is the most important requirement for a controller. The controller having faster set point tracking is always preferred in the process industries. Simultaneous Set point tracking is carried out for the considered three controllers and its result is shown in the Fig. 8. It is clearly observed that BFO based PID controller provides better set point tracking compared with the ZN method and Relay feedback method. Frequently varying pH values due to different parameter variation is a major problem in the waste water treatment process. The fitness of the controller can be judged by testing the performance of the controller under the load change condition. The performance of the controller is studied by applying load disturbance to the process model, which is shown in the Fig. 10 and Fig. 11. Simultaneously all the three controllers are applied with a disturbance and it can be noted that the BFO algorithm based controller eliminates the effect of disturbance much faster than Z-N method and Relay feedback method. The BFO based controller exhibits an IAE value of 4.397 against 8.03 for relay feedback method. The IAE value of Z-N method is 10.57. Also the table 1indicates that BFO Algorithm based PID controller has overall better performance Indices than the other two controller tuning methods. Table 2: Performance indices of different controller structures. Structure % of Mp tr (sec) ts (sec) PID 34.0 5.05 12.0 I-PD 5.42 15.0 25.0 FPID 00.0 22.0 24.0 IAE 4.39 7.72 6.76 ISE 2.91 5.08 4.93 1.4 1.2 Reference tracking 1 0.8 0.6 0.4 Setpoint PID I-PD FPID 0.2 0 0 10 20 30 40 50 Time (sec) Fig. 12: Comparison of Servo Response of different PID structures. 0.6 Controller output 0.5 0.4 0.3 PID I-PD FPID 0.2 0.1 0 -0.1 0 10 20 30 40 50 Time (sec) Fig. 13: Comparison of Controller response for different PID structures. 1.4 1.2 Response 1 0.8 0.6 0.4 Setpoint 0.2 0 0 20 PID I-PD 40 60 FPID 80 100 Time (sec) Fig. 14: Regulatory Response for different structures. 0.6 Controller output 0.5 0.4 0.3 0.2 0.1 0 -0.1 0 PID 20 I-PD FPID 40 60 Time (sec) Fig. 15: Controller output for Regulatory Response. 80 100 ITAE 15.56 41.72 30.01 ITSE 5.38 17.93 13.92 70 M. Kandasamy and Dr. S. Vijayachitra, 2014 Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 In continuation of the first study, second analysis is carried out to evaluate the best PID controller structure for the pH Neutralization process. The parallel PID controller, I-PD controller and Set point filter PID controller are considered for this analysis. Multiple Objective Performance Index (MOPI) based BFO algorithm is used to find out the optimum controller parameters to study the performance of different PID controller structures. A simulation study is carried out to evaluate the set point tracking (servo response) performance of the three different controllers simultaneously. The Fig. 12 and Fig. 13 show the servo response of the different PID structures and corresponding controller output respectively. The Table 2 shows the performance indices of different PID structures. It is noted that the parallel PID controller may not be preferred for practical implementations due to its large peak overshoot value. It is interpreted that the I-PD controller has better peak overshoot compared to the parallel PID controller. However, the most importantly, the filter PID has zero overshoot. Load disturbance is applied to the process model to study the regulatory response of different PID controller tuning. The Fig. 14 and Fig. 15 show regulatory response and corresponding controller output of the controllers. It can be observed that filter PID controller eliminates the effect of disturbance much faster than other two controllers. The filter PID controller provides the minimum value of IAE such as 6.76 against 7.72 of I-PD controller. Also, the filter PID controller show Better performance in error minimizing indices such as ISE, ITAE, ITSE and settling time. In overall, the Set point filter PID controller has performed well compared with parallel PID and I-PD controller for the pH Neutralization plant. Conclusion: A Bacterial Foraging optimization (BFO) Algorithm based PID controller tuning is proposed for process of Non-Linear pH Neutralization. The proposed method produced better result compared to Ziegler-Nichols and Relay feedback controller tuning methods in obtaining performance indices of IAE, ISE, ITAE, ITSE and closed loop performance of peak overshoot, rise time and settling time. The BFO algorithm PID controller result is again tested on two different controller structures i.e, I-PD Controller and Filter PID controller for further study. In this, Filter PID controller exhibits better closed loop performance and better performance indices. The controllers are also tested for set point tracking and disturbance rejection. In this, the BFO based Filter PID controller has efficiently tracks set point and provides desired load disturbance properties compared with parallel PID and I-PD controller. REFERENCES Astrom, K.J. and T. Hagglund, 1984. Automatic tuning of simple regulators with specifications on phase and gain margins. Automatica,. 20(5): 645-651. Biswas, A., S. Das, A. Abraham, and S. Dasgupta, 2010. Stability analysis of the reproduction operator in bacterial foraging optimization. Theoretical Computer Science, 411(2): 2127-2139. Buchholt, F. and M. Kummel, 1979. Self-tuning Control of pH-Neutralization Process, Automatica, 15: 665-671. Chen, H., Y. Zhu, and Hu, K. 2011. Adaptive bacterial foraging optimization. Abstract and Applied Analysis, vol. 2011, Article ID 108269, 27. Christoph Hametner, Christian H. Mayr, Martin Kozek and Stefan Jakubek, 2013. PID controller design for nonlinear systems represented by discrete-time local model networks. International Journal of Control, 86: 1453-1466. ImmaNuella, Cheng Cheng and Min-Sen Chiu, 2009. Adaptive PID Controller Design for Nonlinear Systems. Industrial Engineering Chemistry Research, 48: 4877-488. Jung, C.S, H.K. Song and J.C. Hyun, 1999. A direct synthesis tuning method of unstable first-order-plustime-delay processes. J. Process Control, 9: 265-269. Kim, J.H. and S.J. Oh, 2000. A fuzzy PID controller for nonlinear and uncertain systems. Soft Computing Springer Link, 4: 123-129. Meenakshipriya, B., K. Saravanan, K. Krishnamurthy and P.K. Bhaba, 2012. Design and implementation of CDM-PI control strategy in pH neutralization system. Asian Journal of Scientific Research, 5(3): 72-92. McAvoy, T.J., E. Hsu, and S. Lowenthal, 1972. Dynamics of pH in Controlled Stirred Tank Reactor. Ind.Engrg. Chem. Process Des. Develop., 11: 68-70. Norazzizi Nordin, SitiFathritaMohd Amir, Riyanto, and Mohamed Rozali Othman, 2013. Textile Industries Wastewater Treatment by Electrochemical Oxidation Technique Using Metal Plate. International Journal of Electrochemical Science, Vol. 8:11403 – 11415. Panda, R.C., 2009. Synthesis of PID controller for unstable and integrating process. Chem. Eng. Sci., 6: 2807-2816. Passino, K.M., 2002. Biomimicry of bacterial foraging for distributed optimization and control. IEEE Control Systems Magazine, 22(3): 52–67. 71 M. Kandasamy and Dr. S. Vijayachitra, 2014 Australian Journal of Basic and Applied Sciences, 8(10) July 2014, Pages: 62-71 Patwardhan, S.C. and K.P. Madhavan, 1998. Nonlinear internal model control using quadratic prediction models. Computers and Chemical Engineering, 22: 587-601. Rajinikanth, V. and K. Latha, 2011. Bacterial foraging optimization algorithm based PID controller tuning for time delayed unstable system. The Mediterranean Journal of Measurement and Control, 7(1): 197-203. Rajinikanth, V. and K. Latha, 2012. I-PD Controller Tuning for Unstable System Using Bacterial Foraging Algorithm: A Study Based on Various Error Criterion, Applied Computational Intelligence and Soft Computing, Volume 2012, Article ID 329389, 10. Rajinikanth, V. and K. Latha, 2012a. Controller Parameter Optimization for Nonlinear Systems Using Enhanced Bacteria Foraging Algorithm, Applied Computational Intelligence and Soft Computing, Volume 2012, Article ID 214264, 12. Rajinikanth, V. and K. Latha, 2012b. Setpoint weighted PID controller tuning for unstable system using heuristic algorithm, Archives of Control Science, 22(4): 481-505. Vijayan, V. and Rames C. Panda, 2012. Design of PID controllers in double feedback loops for SISO systems with set-point filters. ISA Transactions, 5: 514-521. Vijayan, V. and Rames C. Panda, 2012a. Design of setpoint filter for minimizing overshoot for low order process. ISA Transactions, 51: 271-276. Wan, J.Q., M.Z.Y.W. Huang, W.J. Ma and Guo, Y. Wang, and H.P. Zhang, 2010. Control of the Coagulation Process in a Paper-mill Wastewater Treatment Process Using a Fuzzy Neural Network. Journal of Bio chem., 425-435. Xiaohui Chen, Jinpeng Chen and Bangjun Lei, 2011. Identification of pH Neutralization Process Based on the T-S Fuzzy Model. Advances in Computer Science, Environment, Eco informatics, and Education Communications in Computer and Information Science, 215: 579-58. Zamani, M., N. Sadati and M.K. Ghartemani, 2009. Design of an H∞, PID controller using particle swarm optimization. International Journal of Control, Automation and Systems, 7(2): 273–280. Ziegler, J.G. and N.B. Nichols, 1942. Optimum settings for automatic controllers. Trans. ASME, 64759768.
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