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Tuning Methods to process control training equipment RT-578

By Corey Simmons,2014-08-09 18:25
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Tuning Methods to process control training equipment RT-578

    Tuning Methods to process control training equipment RT-578.

    Cipriano Alejandro del Angel Vicente, Claudia Ariana Ramirez, Juan Angel Zamora

    Advisor: Miguel Angel Barron Castelan.

    Instituto Tecnológico Superior de Tantoyuca. Engennering Electronic.

     called controlled system. The variable ABSTRAC. out or real x value of this team, is a

     parameter that want to keep controlled There are several methods that through in a desired value w.

    the PID (Proportional Integral Derivative)

    can generate automatic control. In this When it is a difference between the real work are used particularly two methods, value x and the desired value w, the the Ziegler-Nichols and Cohen-Coon that driver will lead to the system toward the are applied to a team of control for desired value. The parameters are industrial processes. These two methods programmed with the methods of tuning are programmed to control the level, the Ziegler-Nichols and Cohen Coon. This flow, the pressure and temperature of a method will provide two forms of certain amount of fluid contained in a compare which of these is more warehouse transparent. convenient to use when you want to Since not all methods are efficient to control a parameter.

     control with accuracy certain parameters,

    To make the experiments use a training they are looking know which of these

    equipment composed of industrial two methods is more efficient to control

    equipment RT-578. these parameters, or for a given

    This team has a deposit transparent in parameter, which method is more

    which regulates the level and the appropriate.

    pressure, a piping system for regulating

    the flow, and a system of two circuits I. INTRODUCTION

    with heat exchanger plates for the

    temperature regulation. The timing by means of control PID is

     very important, is already in many of the

    different technologies of our II. METHOD OF ZIEGLER-NICHOLS environment. Since the cars we handle

    daily until the nuclear reactors electricity Ziegler and Nichols suggested two generators. In this case apply control to a methods of tuning to determine the team of industrial processes to which it is values of the gain proportional (Kp), the

time integral (Ti) and the time derivative

    (Td) on the basis of transient response

    from a specific methods so-called tuning

    of Ziegler-Nichols.

    FIRST METHOD (Curve of reaction)

    In the first method, the response of a

    plant before an entry step is obtained

     from an experimental basis.

    The driver PID tuned through the first The response curve step unit takes the

    method of the rules of ziegler-Nichols form of S if the plant does not contain

    produces: integrators nor poles dominant complex

    conjugates. This curve is characterized by

    two parameters: the delay time (L) and

     the time constant (T). If the answer is not

    a curve in the form of S is not advisable

    to use this method.

    Therefore, the driver PID has a pole in

    the origin and a double zero in S=-1/L.

    SECOND METHOD (Oscillation

    continuous)

    In this method, first outlined the values of Ti= and Td=0. Subsequently, using only In this case the role of transfer is the action proportional control increases approaching through a system of the first the value of Kp from zero to a critical order with a delay of transport as shown value where the exit show sustained below: oscillations. If such an exit shows no

    oscillations sustained for any value of Kp,

    this method cannot be applied.

    Therefore, the gain and the critical

    period are determined experimentally. In the first method, Ziegler and Nichols

    established the values of Kp, it, and Td in Ziegler and Nichols suggested that the accordance with the formula that values of the parameters Kp, Ti and Td in appears in the following table.

    METHOD OF COHEN-COON (Reaction) accordance with the formula the

    following table.

    Cohen and Coon were the first to

    observe that for most of the processes

    controlled, the curve of a reaction may

    be approximate to the response of a

    system of the first order with time died.

    This requires of the estimate of a gain

    stationary, a time constant effective and

    a time dead cash to characterize the

    process and get a response that comes The driver PID tuned through the second close very closely to the curve of reaction method of Ziegler-Nichols produces: of the current process.

    Cohen and Coon also developed rules of

    tuning with the aim of achieving replies

    with a reason decay of a fourth. However,

    as this criterion does not provide a single

    set of parameters of tuning, the rules of

    Cohen-Coon estimated values different Therefore, the driver PID has a pole in from those encountered by Ziegler and the origin and double zero in s=-4/Pcr. Nichols, as shown in the following table. The rules of tuning Ziegler-Nichols apply

    only to the plants whose dynamic is

    known.

    The rules developed by Ziegler and

    Nichols are the most used in the tuning

    drivers PID, when it is difficult to obtain

    the mathematical model of his plant to

    which he requires some kind of control.

    These rules of tuning require initially an

    experimental stage where the engineers

    in charge of the development of the Interestingly, more than half of the controller PID, must specify the response industrial controllers used today used that generates the plant and with it control schemes PID or PID amended. determine the driver appropriate, if that The drivers PID analog are mainly type can be applied the methods of Ziegler -

    Nichols.

hydraulic, pneumatic, electronic,

    electrical or its combinations.

    Desarrollo.

    Apply the second method of Ziegler-

    Nichols to our plant:

     0.8G(s) 3230s;43s;14s;1

    Which was obtained by mean training

    equipment RT-578, shown below, where

    it try to control the water level at set-

    point.

    From it figure; we can obtain the

    . parameter Pcr9.1666667

    On the other hand, we have at the next

    table; how we can compute Kp. Ti and Td

    to different controllers PID?s.

    Controller Kp Ti Td

    P 11.5 0 ?

    PI 10.35 7.638889 0

    PID 13.8 4.583334 1.14583

     We know the critical gain is . Kcr23

    Knowing this parameter, we can to Now, we have the simulations about it compute the critical period Pcr based in for the controllers P, PI and PID?s. It use the next table: Simulink of Matlab.

    Summary.

    We can see, only the P controller reach

    the stability . The controllers PI y PID

    don?t never reach the stability, because

    the output is mainted at oscilling , then

    we can to say the P controller is the best.

    This way, we can use the Ziegler-Nochols

    method first and we have a good stability.

    The stability time is about 70 seconds.

    References.

    [1] Modern Control Engineering.- Ogata

     Katsuhiko Ed. Prentice Hall.

    Then, its shown the results obtain for [2] Manual de Experimentos.- RT-578 each controller: Equipo de control de proceso industrial.

    [3] Advanced PID Controllers.- Astrom, K.

    J.

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