INDUSTRIAL AUTOMATION

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INDUSTRIAL AUTOMATION

• (Getting Started week -1)

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Contents

• PID Controller.
• Implementation of PID Controller.
• Response under actuator Saturation.
• PID with Anti Reset windup.
• Tuning methods of PID Controller.

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PID controller

• Consists of three
• modes
• Proportional.
• Intigral.
• Derivative.

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PID Contd.

• the output of the PID controller u(t) can be
  expressed in terms of the input e(t).

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Basic terms related to PID

• Kp Proportional gain. PB Proportional
  Band
• Ki Intigral gain Kp/Ti
• Kd Derivative gain Kp.Td
• where,
• TiIntigral Time Time taken to repeat the
  proportional control for a step
  signal(min/repeat).
• TdDerivative time Time taken for the
  proportional term to equal the derivative term
  for a ramp signal.

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Implementation of PID Controller

• Integrator Windup under Actuator Saturation

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Implementation Contd.

• PID Controller with anti reset Windup.

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Tuning of PID Controller

• Involves selection of the proper values of
  Kc,Tau_I and Tau_d.
• Best method, Ziegler-Nichols method of tuning.
• the values of controller parameters that bring
  the closed-loop system to the verge of
  instability by
• 1. Simulation.
• 2. Root Locus Technique.
• 3. Direct substitution.

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Contd.

• Using Proportional only control, determine Kc
  Ku (ultimate controller gain)
• the period of the sustained oscillations Pu
  (ultimate period of oscillations).
• Pu
  2p/?co
• If the Kc is increased the process dynamics
  goes through the following sequence of behaviour

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Tuning methods Contd.

• By using the values of Ku and Pu, determine the
  other parameters
• of PID Controller. summarized as below.

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Contd.

• Dynamic changes as Kc is increased for a FOPDT
  process.

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Controller Tuning In Time Domain

• This is done by approx. model based on the
  Process Reaction Curve(open -loop).

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Contd.

• The other parameters of controller can be
  caluclated as folows.

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Example

• The given transfer function is as follows. By
  using SIMULINK/MATLAB.
• we can get the parametes of PID controller.
• By the Zeigler-Nichols method, the tuning of PID
  is done.

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Example Contd

• The characteristic eqn of the system is given by
• By using the method of substitution , for P
  controller only calculate the Ultimate gain.

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Example Contd.
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Example Contd.
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Example contd.

• By the measuring ultimate gain and ultimate
  period we can get the other parameters by Z-N
  method.
• Z-N tuning will be
• P Kc 0.5Ku 0.83
• PI Kc 0.45Ku 0.75 Tau_I Pu /1.2
  10.5 min
• PID Kc 0.6Ku 1.0 Tau_I Pu /2 6.3
  min
• Tau_D Pu /8 1.6

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Example contd.

• Final Response for PID controller.

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Thank you