by applying concept of auto switch PID in real time process.

Transcription

1 DESIGN OF AUTO SWITCH PID ON NEUTRALIZATION PROCESS (Syahrizal Ismail, Hendra Cordova) Department of Engineering Physics FTI ITS Surabaya ITS Keputih Sukolilo Surabaya Telp : +-9 Fax : syahrizal_ismail@yahoo.com Abstract This paper presents result of design auto switch PID on neutralization process. Nonlinear nature of neutralization become problem in designing control system. Thus, this research builds control system at neutralization based on auto switch PID. Auto switch PID is a PID controller that works based on range setpoint, and then tune in each setpoint region. setpoint region obtained from titration curve acid-base experiment. Acid solution used is a strong acid HCl,M, while base solution is strong base NaOH,M. Acid solution flow rate is maintained constant, while the base flow rate is controlled. Dc pump V used to drain solution. Sensor used meter and electrode. The software used LabVIEW 9 with DAQ as acquisition data. Systems analysis is based on three criteria, maximum overshoot, time settling, and error steady state. Result of distribution setpoint regions are,- for region, -9,9 for region, and 9,9-, for region. Tuning results for each region obtained Kp, Ti, Td. for region, Kp, Ti, Td. for region, Kp, Ti, Td. for region. The lowest maximum overshoot and the fastest settling time given by region which are,9% and 9 seconds. The smallest error steady state is region by,%. Beside that, system successfully handle load which is addition of acid solution flow rate, as long as lower than base solution flow rate. Key words : neutralization, auto switch PID, LabVIEW by applying concept of auto switch PID in real time process.. Introduction neutralization is a mixing process between the acid solution and base solution. The addition of one solution against values resulting in mixing process has nonlinear properties. It can be seen clearly on the titration curves of acid and bases established process. The addition of a little volume of one solution, value can change siginificantly especially on the way to neutral. Hendra Cordova (), has been done research on the design of auto switch PID in neutralization process in CSTR (Continuous Stirred Tank Reactor). In that concept, the nonlinear titration curves is divided into several linear regions. These regions are then performed controller parameter tuning. Fadloli Luthfi (), design an auto switch PID on CIPM (Continuous Injection Pipe Mixing). In that study has successfully demonstrated how auto switch PID able to handle the process PID control. However, these studies are still limited to simulation. Therefore, this research purposes to construct a system of control at neutralization process,. Theory The concept of hydrogen ion exponent () was introduced by Sorrensen (99) in order to avoid the hassle of writing the number of negative factor of []. The definition of the concept of as in the equation below : [ ] [ ] () Based on the equation above, value equal to negative logarithm of hydrogen ion or the logarithm of the reciprocal of the concentration of hydrogen ions. It is very easy to write the level of acidity or alkalinity of a solution with. value of -. A molar solution of strong acid changed a part, the of the solution is and mole of a strong base of monovalent has a of [].. Acid and Base Theory Inorganic substances can be classified into three main groups, namely: acids, alkalis and

2 salts. Arrhenius acid-base theory indicates that electrolyte molecules always produce negative and positive ions when dissolved in water. Acid, expressed as a compound to dissolve in water dissociates to produce hydrogen ion [H+] or hydronium ions [HO] as positive ions only[]. An example solution is the acid HCl. HCl is an acid, because the solution it can release hydrogen ions [H+] by reaction : Water (HO) is a neutral solution, which is located between the nature of acidic and alkaline properties. Equilibrium reactions of dissociation of water is as follows: () Water has a small constant value, approximately,x- at C. This suggests that the degree of dissociation of water to be ignored and in practice can be considered separate, so that the concentration of water can be considered constant. () Base is defined as a substance to dissolve in water will run into shape with the decoupling of the hydroxyl ions, such as the ions only negative. NaOH is an example of an alkaline solution. NaOH is a basis because the water that can release ion hydroxyl (OH)-according to the reaction : [ ] [ ] () Equation is the ion product of water (Kw) at room temperature. The importance of product ions of water lies in the fact that the value can be considered constant. This means that, if the acid is dissolved in water, hydrogen ion concentration can be increased only with accompanying reduction in the concentration of hydroxyl ions. Conversely, if the base is dissolved in water, the concentration of hydroxyl ions increases and decreases in the concentration of hydrogen ions. Acid and base theory also related to acids and bases titration. Titration means mixing between acid solution and base solution using. In laboratorium scale, usually using burette for titration process. There are several types of acids and bases titration, in this research using strong acid and strong base titration. Typical titration curve of strong acids and strong bases titration shown in figure. () Preparation of acidic or alkaline solution with the State of the Molarity (concentration) can be done by mixing an acid or base with aquades water distilled. He began to mix with knowing the Molarity of the acid or base value ( ) with specific concentration levels ( ) and relative mass ( ) by equation below : () After that, use the similarity between the volume of acid or base should be diluted (V) is multiplied by the molarity (M) by the volume of solution the desired acid or base (V) with molarity (M) as below: () Salt on the basis of the definition of substance is the result of the reaction between the acid and base neutralization reaction or the substance of a solution of acid and alkaline solutions are equivalent. The salt has no distinctive features of an acid or alkaline. vol basa (ml) Fig.. Titration curve of strong acids and strong bases titration[] ()

3 . pump, and plant is CSTR. Output process is measured in CSTR. Neutralization Process On CSTR Setpoint CSTR T DAQ e + u C Pump mv CSTR Output - PC T Motor Driver Fig.. Block diagram CSTR. Acid Tank Acid Pump Auto Switch PID The use of PID controllers are usually found in a linear process. The merger of the three types of control elements shows the advantages of each element and the deficit. The weakness of the P controller can be covered by combining with I. controller controller I aims to eliminate the offset. Weaknesses in control I is the delay that occurs in the system response. Merging with a D controller can speed up the response so that weaknesses can be covered in my control. Mathematical equations of the control signal given by PID controller can formulated below: Drain Base Pump Base Tank Fig.. neutralization on CSTR Figure is a process of neutralisation of in continuous stirred tank reactor used in this research. In the tank, there is an agitator for mixing a rapid process. Acid flow rate remains constant, while the basic rate of flow under control. PC receives data about measured in tank. Serial communication used to transfer data from sensor. DAQ LabVIEW used to send control signal from PC to drive dc pump. All process parameters in this research can be seen in table. Table Process Parameters No Parameters Main Tank Volume Acid TankVolume Base Tank Volume Acid Flow Rate Base Flow Rate Acid Concentration Base Concentration u(t ) K p.e(t ) Kp Ti t e(t )dt K T p d de(t ) (9) dt control which is a nonlinear process, using a technique called PID automatic switches. PID automatic switch is essentially a form of division of the PID parameters Kp, Ti, Td, in every region of the linear output. Furthermore, in every region of linear PID tuning parameters in accordance with design. Setpoint division shown in figure. Unit L, L, L, L/min -, L/min,M - Model, PID Model, PID -,M Model, PID - Figure is a block diagram of the process. Input process is setpoint, actuator is dc Flow rate Titration (ml/s) Fig.. Setpoint division[]

4 Figure is a configuration of an auto switch to the PID control block diagram. At the time of the switch PID automated process will work in accordance with the given input setpoint. Setpoint determination depends on the distribution of each linear region that has been done before. SETPOINT + - e SETPOINT RANGE SETPOINT RANGE SETPOINT RANGE PID PID PID Fig.. Auto switch PID. Implementation of Auto Switch PID Implementation of auto switch PID controllers based on data from the experimental titration curve in figure. Solution used strong acid,m HCL and strong base, NaOH. The experiments were performed using a titration burette. Experimental titration curves obtained through the process of adding 9. ml of. M NaOH in ml of. M HCL Altogether there are experimental data from titration with strong acids strong bases. Furthermore, the curve formed by the experimental results are divided into several linear regions. Based on the figure then get the pieces of the linear region,. <.,. <9.9, 9.9 <.. The division of this area will be a guide in applying the automatic switch controller PID, especially in the process of tuning the PID parameters. u. Sensor Reading Data retrieval for sensor readings performed at values, and. Solutions used to obtain a value of each using a buffer solution. Figure is a result of sensor readings at a of is displayed on the LabVIEW software. Errors resulting from a superficial reading of the of the solution is as follows: Error = solution output () = - = Figure and 9 are the readings for each and. Using the same way as in equation to determine the reading error in the reading of and. At the time of reading the value at increased the range to. This is caused bulb sensor still reading rest solution of. The overall results of sensor readings contained in table. Table Sensor reading results Solution Reading Error Reading Result PID PID PID Volume NaOH (ml) Fig.. Titration experiment curve

5 Fig.. reading Setpoint Output sustained oscillation response. K p value obtained when the system undergoes sustained oscillations is K p =. Oscillatory response is shown in Figure. Table Oscillation tuning table [9] Controller PB Reset Rate P PB u - - PI. PB u. T u - PID. PB u. T u. T u Fig.. reading Fig. 9. reading Setpoint Output Setpoint Output. Tuning PID Parameter PID parameter adjustment method performed using an oscillating tuning and trial and error. Oscillation Tuning early as the determination of the PID parameter, if it feels the results are still not meet the tuning is done by modifying the oscillation by trial and error. Oscillation tuning is done by inserting a value of as the setpoint. Oscillation adjustment done in the area because of area is the most sensitive area than other areas. Thus, by tuning in region in advance, will allow tuning to another area. After entering the setpoint value of and then raise the value of K p for a Then, find ultimate periode (T u ) which is the distance from peak to peak oscillations. T u is represented by time in seconds. T u value obtained by seconds, but due to scaling, it becomes, seconds in LabVIEW s graphic Fig.. Oscillatory response Setpoint Output K p, T i, T d are found by inserting parameters controller into tuning oscillation table in table. Thus, value K p =,9, T i =9, T d =,. After that, system response seen by inserting each parameter to PID controller. As for the system response as shown in Figure. Fig.. Ultimate periode (T u )

6 Based on the result, it appears that the system has been able to pursue the setpoint and steady. However, the resulting response is still not satisfactory, because the system oscillates at the beginning of the process. In addition, the time required to achieve stable is also very slow. Thus, each parameter is modified to get better results. For region and region tuned by trial and error. Performance criteria of system respone is describe below :. Maximum Overshoot %. Error Steady State -,%. Settling Time seconds 9 Waktu (s) Fig.. Response oscillatory tuning 9. Tuning Region (, <,) Tuning is done by inserting the value of as the setpoint. Parameter values have been obtained in tuning oscillation is converted to lower value. Thus, parameter values are K p =, T i =, T d =,. Performance criteria of the tuning response graphs are as follows :. Maximum Overshoot,%. Error Steady State,%. Settling Time seconds Setpoint Output Fig.. Tuning response region 9. Tuning Region (, <9,9) Tuning region of the setpoint range between. to 9.9 is done by entering a value of as a setpoint. Through trial and error method the values obtained for each of the control parameters K p =, T i =, T d =,. As for tuning the response graphs for area as shown in Figure the response tuning of area Fig.. Tuning response region Performance criteria of tuning response graphs are as follows :. Maximum Overshoot,%. Error Steady State,%. Settling Time seconds Setpoint Output 9. Tuning Region (9,9 <,) Tuning region that for the ranges from 9.9 to. is done by inserting a value of as a setpoint. The value of each parameter for

7 local control obtained K p =, T i =, T d =,. As for tuning the response graphs for area as shown in Figure tuning the response area. Fig.. Tuning response region Performance criteria of the tuning response region graphs are as follows :. Maximum Overshoot,9%. Error Steady State -.9%. Settling Time seconds Based on data from the previous explanation of the value of each parameter for each PID setpoint can be grouped in regions as in Table the value of the PID parameters. adding just a little can cause significant changes in. Reviewing the performance of the three tuning regions, obtained the lowest values obtained maximum overshoot and settling time of the fastest occurring during the tuning region, then the smallest steady state error is given when performing tuning region. 9. Setpoint Tracking Test Setpoint Tracking test done by raising and lowering setpoint from one region to the other region. Setpoint raising from to, and to. Meanwhile, lowering setpoint from to 9. Figure shown setpoint tracking test from to. Performance criteria of tuning response graph are as follows :., to,% % 9 seconds. to,% -,9% seconds Tabel PID parameters values [] No Setpoint PID Parameter Regions K p T i T d,-,,,-9,9, 9,9-,, Setpoint Output In tuning the first area, a very high spikes occur at the response graph. This is caused by a narrow distribution where the value of is used as a setpoint, while the area is the range of and values. Therefore, the actuator is still receiving a signal from the controller when Fig.. Setpoint tracking test to In figure the setpoint tracking test to, values from,. value raises, and until seconds system respond to

8 . Oscillation occurred until, and at seconds, steady state reached at, Waktu (s) Fig.. Setpoint tracking test to Setpoint Output Performance criteria of tuning response graph for setpoint tracking test to are as follows :., to,% -,% seconds. to,% -,9% seconds Waktu (s) Setpoint Output Fig.. Setpoint tracking test to 9 Figure is a setpoint tracking test of the value of 9. When starting the process, the at.. This system takes about 9 seconds to reach the setpoint value and steady state up to seconds. The highest peak value at.. After that lowered the setpoint value at 9. The system goes down slowly until it rests at. to second. Furthermore, the system starts in pursuit of the setpoint 9 where there is a small oscillation in progress.., to,9% % seconds. to 9,% -,% seconds At setpoint tracking test, can be seen that the dominant oscillations occur in region (. <9.9), both setpoint tracking up or down. This caused by characteristic in titration curve, that region is the most sensitive area. Thus, it needs an aggressive controller that marked by larger T d value.. Load Test Load test done by increasing acid flow rate when system has reached steady state. Flow rate increased to,9 L/min and, L/min. This caused due to reason response system when testing load for acid flow rate lower than base flow rate, and second time for acid flow rate higher than base flow rate. 9 Setpoint Output Fig. 9. Load test for acid flow rate,9 L/min

9 Figure 9 is a system response for load test with acid flow rate,9 L/min. Acid flow rate was increased at st seconds. The system began to respond due to the addition of acid flow rate after seconds. value down until,. However, system gives settling time by since addition of flow rate is 9 seconds, maximum overshoot by,9%, and error steady state by -,% Setpoint Output Fig.. Load test for acid flow rate, L/min Figure is a system response for load test with acid flow rate, L/min, which is larger x than base flow rate. Addition of acid flow rate was done when system reach steady state for 9 seconds. The system began to respond due to addition of acid flow rate after seconds. Yet, due to acid flow rate is larger than base flow rate, system can not bring back to previous condition. Even, value down until,. This caused by, the characteristic of titration process that need acid flow rate smaller than base flow rate. Thus, the problem in this research was limited that, acid flow rate must not exceed than base flow rate.. Conclusion After doing research on the implementation of auto switch PID in real time, it can be concluded that auto switch PID have been successfully implemented and integrated with NI LabVIEW software. The results of performance tests as a whole, the lowest maximum overshoot and the fastest settling time given by the tuning of the region, and the smallest steady state error is given by region. Beside that, the system is able to respond to the addition of a specific flow rate of acid during the acid level is lower than base flow rate.. Recommendation There are a few suggestions that can be given for subsequent control research are:. Titrate the solution can be varied in the titration of strong acid to weak base or strong acid titrated with a weak base.. Build level control system for each tank, thus mini plant robuster than previous. REFERENCES [] Cordova, H.. PID Self-Tuning Based On Auto Switch Algorithm To Control. Teknik Fisika, ITS : Surabaya [] Luthfi, Fadloli.. Perancangan Sistem Pengendalian pada Continuous Pipe Mixing (CIPM) dengan Metode Pengendalian PID-Selftuning Berbasis Auto Switch Algorithm. Teknik Fisika, ITS : Surabaya [] Zainuddin Hamidi, M. ; Perancangan Sistem Pengendalian dengan Metode Input-Output Linearization pada Plant Saturator di PT. Petrokimia Gresik. Teknik Fisika, ITS : Surabaya [] Fitra Wijaya, Andry.. Perancangan Kontroler Neuro PID Self Tuning Berbasis Jaringan Syaraf Tiruan Pada Proses Netralisasi di PT Petrokimia Gresik. Teknik Fisika, ITS : Surabaya. [] Chang, Raymond.. Kimia Dasar Edisi Ketiga Jilid. Jakarta : Erlangga. [] Chang, Raymond.. Kimia Dasar Edisi Ketiga Jilid. Jakarta : Erlangga. [] Ogata, Katsuhiko. 99. Teknik Kontrol Automatik. Jakarta : Erlangga. 9

10 [] Peter YIen, Jean.. Measuring, Modelling And Controlling The Value And The Dynamic Chemical State. Helsinsky University of Technology. [9] PID User manual control toolkit Syahrizal Ismail was born in Bekasi, -Nopember-99. Student majoring in Engineering Physics FTI-ITS class. Active as a board of HMTF period -9. Internship program conducted at PT Astra Daihatsu Motor to the theme of the analysis of materials at the electrode tip of welding robots. Areas of interest are tracked instrumentation and control. His carrer path continues in oil field services company Schlumberger, which placed in Duri, Riau.