Process Dynamics & Control Quiz
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What type of signal does the controller output to the control valve?

  • An electronic current signal ranging from 4 to 20 mA (correct)
  • A pneumatic signal of 3 to 15 psig
  • A digital signal of 0 to 5 V
  • An analog voltage signal of 1 to 10 V

    • Which of the following characteristics describes the control valve?

  • It has a first-order transfer function (correct)
  • It has a second-order transfer function
  • It exhibits large dynamics during operation
  • It requires a digital signal input

    • What is the primary purpose of the closed-loop transfer function in a control system?

  • To predict the system's response to inputs (correct)
  • To determine the maximum input limit of the system
  • To calculate the energy consumption of the system
  • To stabilize the system's linear response

    • What is the function of the I/P transducer in the control system?

    <p>To provide linear characteristics with negligible dynamics (B)</p> Signup and view all the answers

    What kind of variation does the control valve exhibit as the valve-top pressure changes?

    <p>Linear variation in flow from 0 to 2 cfm (C)</p> Signup and view all the answers

    What does Gc(s) represent in the context of proportional control?

    <p>The control system gain parameter (D)</p> Signup and view all the answers

    In a proportional control system, how does a unit step change in set point affect the system?

    <p>It initiates a change in output proportional to the change in set point (D)</p> Signup and view all the answers

    What is the key factor that makes the Gp(s) and Gd(s) transfer functions identical?

    <p>Both q1 and q2 represent inlet flow rates affecting h (C)</p> Signup and view all the answers

    What does the term 'open-loop gain KOL' refer to in control systems?

    <p>The gain where no feedback is applied to the system (D)</p> Signup and view all the answers

    Which element is likely to trigger a different response in a proportional control system?

    <p>A change in the set point (A)</p> Signup and view all the answers

    What is the primary function of gain G1 in the block diagram reduction?

    <p>To amplify the input signal (B)</p> Signup and view all the answers

    Which type of control response is characterized by changes in set-point only?

    <p>Proportional Control &amp; Set-Point Changes (C)</p> Signup and view all the answers

    What is the first step in developing a closed-loop block diagram?

    <p>Identify the control input (D)</p> Signup and view all the answers

    Which of the following inputs can be introduced to a control system for analysis?

    <p>Step input (A)</p> Signup and view all the answers

    What does the term 'Ysp' most likely refer to in a control system context?

    <p>Set-point value or desired output (B)</p> Signup and view all the answers

    What is the result of using a Proportional-Integral (PI) controller in an integrating process?

    <p>Improved steady-state error performance (B)</p> Signup and view all the answers

    To properly evaluate the responses of a control system, which domain should be used?

    <p>s-domain or t-domain (A)</p> Signup and view all the answers

    Which case mainly addresses disturbance changes in a control system?

    <p>Proportional Control &amp; Disturbance Changes (D)</p> Signup and view all the answers

    What role does the mass flow rate w2 play in the blending tank system?

    <p>It acts as the manipulated variable. (C)</p> Signup and view all the answers

    What is the function of the current-to-pressure transducer in the blending tank control system?

    <p>To adjust the pneumatic control valve based on electrical signals. (C)</p> Signup and view all the answers

    In the described control system, what is the primary disturbance variable?

    <p>The inlet composition x1. (D)</p> Signup and view all the answers

    What type of transfer function does the composition sensor-transmitter have?

    <p>First order transfer function. (B)</p> Signup and view all the answers

    When can the dynamics of the instrument in the measuring element be approximated as negligible?

    <p>When the time constant of the instrument is much greater than that of the system. (A)</p> Signup and view all the answers

    What defines the steady-state gain Km in the blending tank system?

    <p>The input &amp; output ranges of the sensor-transmitter. (B)</p> Signup and view all the answers

    Which element is primarily responsible for maintaining the desired tank composition?

    <p>The electronic controller. (A)</p> Signup and view all the answers

    Which statement correctly describes the blending process in the control system?

    <p>It regulates the tank's inlet flow based on its composition. (D)</p> Signup and view all the answers

    What is the formula to determine the response of a control system in the s-domain?

    <p>Response = Input x Overall transfer function (B)</p> Signup and view all the answers

    Which theorem can be used to determine the final value of a controlled variable (CV)?

    <p>Final Value Theorem (D)</p> Signup and view all the answers

    What does an overshoot generally indicate about a second-order control system response?

    <p>The system may be underdamped (B)</p> Signup and view all the answers

    In the given control system, which variable is considered a disturbance variable?

    <p>Inlet flow rate q1 (D)</p> Signup and view all the answers

    How can the system offset be calculated in control systems?

    <p>Offset = SP - SS value (B)</p> Signup and view all the answers

    Which of the following best describes a critically damped system?

    <p>It returns to equilibrium as quickly as possible without oscillating (C)</p> Signup and view all the answers

    What assumption is made regarding the dynamics of the level transmitter and control valve in this control system?

    <p>They have negligible dynamics (B)</p> Signup and view all the answers

    In the context of the liquid level control system, what does 'Kp' represent?

    <p>Proportional gain for hydraulic resistance (A)</p> Signup and view all the answers

    Flashcards

    Controller

    A device that compares the desired setpoint with the actual process measurement and generates a control signal to manipulate the process variable.

    Current-to-Pressure (I/P) Transducer

    A device that converts an electronic signal (current) to a pneumatic signal (pressure).

    Control Valve

    A device that manipulates the flow of a process fluid based on the control signal received.

    Closed Loop Transfer Function

    A mathematical representation of a system's response to different inputs. This helps predict how the system will behave under varied conditions.

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    Overall Transfer Function

    A mathematical model that combines the transfer functions of all components in a closed-loop system.

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    Block Diagram

    A visual representation of a system using blocks to represent different components and arrows to indicate the flow of signals.

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    Transfer Function

    A function that describes the relationship between the input and output of a system in the Laplace domain. It helps analyze the system's dynamic response.

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    Manipulated Variable (MV)

    The variable that is manipulated to control the system's output. In the blending tank example, it's the flow rate of pure component A (w2).

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    Controlled Variable (CV)

    The variable that is being controlled. In the blending tank example, it's the tank composition (x).

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    Disturbance Variable (DV)

    The variable that influences the controlled variable but is not directly manipulated. In the blending tank example, it's the inlet composition (x1).

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    Dynamic Model

    A model used to predict the behavior of dynamic systems over time. It allows for analyzing the system's response to various inputs and disturbances.

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    Measuring Element

    A device that measures a process variable and converts it into an electrical signal. In the blending tank example, it's the composition sensor-transmitter.

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    Negligible Dynamics

    The capacity of a measuring element to respond to changes in the measured variable without significant time lag. In the blending tank example, it's assumed to be negligible with a time constant (τm) much smaller than the process time constant (τ).

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    Block Diagram Reduction

    The process of simplifying a block diagram by combining blocks with common inputs and outputs.

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    Control Variable (CV)

    The controlled variable (CV) that is being regulated, often by manipulating the manipulated variable (MV).

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    Proportional Control

    A proportional controller measures the error between the setpoint and the process variable and outputs a control signal proportional to the error.

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    Proportional-Integral Control

    A proportional-integral (PI) controller combines proportional control with an integral term that eliminates steady-state error.

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    Setpoint Change vs. Disturbance

    A change in setpoint is a change in the desired value of the process, while a disturbance is an unplanned change in the process itself.

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    Closed-loop response

    The closed-loop response of a system describes how a system reacts to changes in setpoint or disturbances.

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    System response

    A system's response is how the system changes in value over time when faced with a change in setpoint or disturbance.

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    Proportional Control Gain (Kc)

    The gain of a proportional controller (Kc) determines the sensitivity of the controller to error. A higher Kc means a stronger reaction to error.

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    Transfer Function (s-domain)

    A mathematical representation of a system's response to different inputs, expressed in the Laplace domain using the variable 's'. It describes how the system reacts to changes in its input.

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    Inverse Laplace Transform

    The process of converting a signal from the Laplace domain (s-domain) to the time domain (t-domain), using the inverse Laplace transform.

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    Response in t-domain (y(t))

    The output of a system expressed as a function of time, typically denoted by 'y(t)'.

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    Initial Value (IVT)

    The initial value of a system's output when time is zero (t=0), often determined using the Initial Value Theorem.

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    Final Value (FVT)

    The steady-state value of the system's output after sufficient time has passed, often determined using the Final Value Theorem.

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    Offset

    The difference between the desired setpoint (SP) and the actual steady-state value (SS) of the system's output.

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    Disturbance (d(t))

    A disturbance that influences the system's output, often denoted by 'd(t)'.

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    Study Notes

    Process Dynamics & Control

    • The subject matter is process dynamics and control, particularly focusing on the dynamic behavior of closed-loop control systems.
    • Key aspects include block diagrams and transfer functions.
    • Various simple closed-loop systems are studied to understand their dynamics.

    Block Diagram

    • A standard block diagram for a feedback control system is presented.
    •  Variables include: controlled variable (Y), manipulated variable (U), disturbance variable (D), controller output (P), error signal (E), and measured value of Y (Ym).
    • Transfer functions for controller (Gc), process (Gp), disturbance (G₁), and sensor-transmitter (Gm) are shown.
    • Steady-state gain (Km) for Gm is also included.

    Blending Tank

    • A blending tank system and its block diagram are presented.
    • The flow rate of pure component A (w₂) is the manipulated variable (MV).
    • The control objective is to regulate the tank composition (x) by adjusting the flow rate w₂.
    • Inlet composition (X₁) is identified as the primary disturbance variable (DV).
    • A sensor/transmitter measures the tank composition, sending a signal (xm) to an electronic controller.
    • The controller output (ranging from 4 to 20 mA) is converted to a pneumatic signal (3 to 15 psig) by a current-to-pressure transducer.
    • The pneumatic signal adjusts a control valve.

    Dynamic Model of Stirred-Tank Blending System

    • A dynamic model of a stirred-tank blending system is presented in the s-domain.
    • The dynamic model equations relate the output (X') to the input (X₁) considering transfer functions (K₁, K₂, τs).
    • τ (time constant) is equivalent to system parameters, which allows prediction of X' based on X₁

    Measuring Element: Composition Sensor-Transmitter

    • The measuring element, a composition sensor-transmitter, is described as a first-order transfer function.
    • The time constant (τm) is assumed negligible for accurate measurements.
    • The steady-state gain (Km) is dependent on the input and output ranges of the sensor-transmitter combination.

    Controller (P, PI, PD, PID)

    • Several types of controllers (P, PI, PD, PID) are discussed.
    • A block diagram illustrates the controller's functionality, including a comparator to determine the error signal.
    • Key variables are set point (Xsp), controller output [mA], error signal (E), process variable (Xm)

    Current-to-Pressure (I/P) Transducer

    • The current-to-pressure (I/P) transducer converts an electronic current signal (ranging from 4 to 20 mA) to a pneumatic signal (3 to 15 psig).
    • This conversion is critical for actuating control valves.
    • The conversion is a linear mapping, with negligible dynamics.

    Control Valve

    • The control valve is a final control element.
    • It is a 1st order transfer function with a time constant (τv).
    • The flow rate (W₂) varies proportionally with the valve position.

    Closed Loop Transfer Function/Overall Transfer Function

    • Methods for determining the overall transfer function of closed-loop systems are explained.
    • Use of block diagram reduction methods is noted
    • The transfer function is critical in predicting system responses to various inputs (step inputs, sinusoidal inputs)

    Closed-loop Responses of Simple Control Systems

    • Various cases (e.g., Proportional Control, PI Control) are presented for evaluating closed-loop responses.
    • Step changes in set points and disturbances are used as input types for evaluating responses.

    Closed Loop Response Steps

    • The steps to analyze closed-loop responses are outlined, including identification of input types.
    • Generating the response in s-domain or t-domain is highlighted.
    • Using graphical methods (e.g., plotting behavior in time domain) to evaluate responses.

    Liquid Level Control System

    • A liquid level control system is described.
    • Variables include liquid level (h), inlet flow rate (q₁), and outlet flow rate (q₂).
    • First-order transfer functions describe the system components (process and input disturbance)
    • System response analysis uses step inputs and is based on proportionality.

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    Process Dynamics & Control KM32104/4 PDF 2024/2025

    Description

    Test your knowledge on process dynamics and control, focusing on closed-loop control systems. This quiz covers topics such as block diagrams, transfer functions, and the dynamics of simple closed-loop systems like blending tanks.

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