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Questions and Answers
What type of controller can be used for implementing PID control in a process control system?
What type of controller can be used for implementing PID control in a process control system?
P, PI, PD, and PID controllers can all be used.
What is the range of the electronic current signal produced by the controller?
What is the range of the electronic current signal produced by the controller?
The range is from 4 to 20 mA.
What is the significance of having negligible dynamics in a control valve?
What is the significance of having negligible dynamics in a control valve?
Negligible dynamics implies a faster response time in the valve, making control more efficient.
How does the flow of substance A through the valve relate to valve-top pressure?
How does the flow of substance A through the valve relate to valve-top pressure?
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What is the role of the closed loop transfer function in a process control system?
What is the role of the closed loop transfer function in a process control system?
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What role does the mass flow rate w2 play in regulating the tank composition x?
What role does the mass flow rate w2 play in regulating the tank composition x?
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How does the controller output signal transition from an electrical to a pneumatic signal?
How does the controller output signal transition from an electrical to a pneumatic signal?
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What assumption is made about the dynamics of the measuring element when τ ≫ τm?
What assumption is made about the dynamics of the measuring element when τ ≫ τm?
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Describe the significance of the steady-state gain Km in the context of the composition sensor-transmitter system.
Describe the significance of the steady-state gain Km in the context of the composition sensor-transmitter system.
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What is the primary disturbance variable (DV) in the blending tank process?
What is the primary disturbance variable (DV) in the blending tank process?
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What is the equation for $X_2$ in terms of $X_1$ and $G_2$?
What is the equation for $X_2$ in terms of $X_1$ and $G_2$?
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Define the closed loop transfer function in a control system.
Define the closed loop transfer function in a control system.
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What type of response is typically analyzed for proportional control in simple control systems?
What type of response is typically analyzed for proportional control in simple control systems?
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In the context of closed-loop control systems, what does the acronym CO, CV, MV, and DV stand for?
In the context of closed-loop control systems, what does the acronym CO, CV, MV, and DV stand for?
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What is the primary task when developing a closed-loop block diagram?
What is the primary task when developing a closed-loop block diagram?
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How do you determine the response in the s-domain or t-domain in control systems?
How do you determine the response in the s-domain or t-domain in control systems?
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What are the different types of inputs mentioned for closed-loop responses?
What are the different types of inputs mentioned for closed-loop responses?
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What is the action taken when there is a disturbance change in a PI control system?
What is the action taken when there is a disturbance change in a PI control system?
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In a control system, what is the significance of the overall transfer function?
In a control system, what is the significance of the overall transfer function?
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What happens during a closed-loop response when a step input is introduced?
What happens during a closed-loop response when a step input is introduced?
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Study Notes
Process Dynamics & Control
- Course code: KMJ32104/4
- Topics covered include block diagrams, transfer functions, and dynamic behavior of closed-loop control systems.
- Specific systems examined involve simple closed-loop systems
Dynamic Behaviour of Closed-Loop Control Systems
- Block diagrams and transfer functions are essential tools for understanding and analyzing these systems.
- Dynamic behavior of various simple closed-loop systems is studied.
Block Diagram
- A standard block diagram of a feedback control system is included.
- Key variables illustrated include controlled variable (Y), manipulated variable (U), disturbance variable (D), controller output (P), and error signal (E).
- Transfer functions for controller, final control element, process, disturbance, and sensor-transmitter are shown (Gc, G₁, Gp, G₁, Gm).
- Steady-state gain for Gm(Km) is also identified.
Composition Control System for a Stirred-Tank Blending Process
- Figure 11.1 depicts a blending tank with a specific flow rate of pure component A (w₂).
- The manipulated variable (MV) is the flow rate of pure component A.
- The controlled variable (CV) is the tank composition (x).
- The primary disturbance variable(DV) is the inlet composition (x₁).
- The composition is measured by a sensor/transmitter, sending a signal(xm) to an electronic controller for adjustments.
Dynamic Model of a Stirred-Tank Blending System
- A dynamic model of a stirred-tank blending system in the s-domain is presented.
- Key variables: X'(s), K₁, K₂, τs, W₁, W₂, X₁(s), X(s) with relevant descriptions.
Measuring Element: Composition Sensor-Transmitter
- A first-order transfer function describes the measuring element.
- The instrument has negligible dynamics when τm >> τ.
Controller: P, PI, PD, PID
- Block diagram for various controller types (P, PI, PD, PID) is provided.
- Key components: Comparator, input signal (Xsp(s)), error signal (E(s)), output signal (P'(s)).
Current-to-Pressure (I/P) Transducer
- Linear characteristics of the I/P transducer are highlighted.
- A specific example is provided, relating a current signal (4-20 mA) to pneumatic signal(3-15 psig).
Control Valve
- Transfer function representation for a control valve in the s-domain (W₂(s)).
- Linear relationship between valve pressure and flow.
Entire Process Control System
- Diagram depicts all elements and their interconnections for the complete blending process control system.
Closed-Loop Transfer Function
- The transfer function allows predicting system response to various inputs (step/sinusoidal).
- Block diagram reduction techniques are demonstrated.
- The transfer functions for the overall system are presented.
Closed-Loop Responses of Simple Control Systems
- Different cases of proportional control with set-point changes and disturbance changes, and PI control are discussed.
- Steps for analyzing closed-loop responses include identifying input types, constructing block diagrams, calculating transfer functions and evaluating system behaviour for different inputs.
- Illustrations of typical responses, including step responses of proportional control are included.
- Offset calculation methods are also involved.
Liquid Level Control System
- The liquid level control system is analyzed, detailing how the level transmitter sends output to control liquid level via adjustments to volumetric flow rate.
- Variables include density, cross-sectional area, flow-head relation, level transmitters, I/P transducers, pneumatic control valve, and controller inputs/outputs.
- Transfer functions relating output flow, input flow and level are presented.
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Description
Test your knowledge on process dynamics and control systems with this quiz focusing on block diagrams, transfer functions, and the dynamic behavior of closed-loop systems. Review key concepts related to systematic analysis of simple closed-loop control systems and their variables.
