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(Code: 21EI52)
Semester: 05
Academic year: 2023-24
ASSIGNMENT-1
QUESTIONS & ANSWERS
1. Sensor: This block is responsible for measuring the liquid level in the tank and providing
an input signal to the controller.
2. Controller: This block receives the input signal from the sensor and compares it to a
setpoint value. It then generates an output signal to the actuator to adjust the liquid level in
the tank.
3. Actuator: This block receives the output signal from the controller and adjusts the liquid
level in the tank by opening or closing a valve.
4. Tank: This block represents the physical system being controlled, which is the liquid level
in the tank.
The input signal to the sensor is typically a voltage or current signal that corresponds to the
liquid level in the tank. The output signal from the sensor is also a voltage or current signal
that is proportional to the liquid level.
The input signal to the controller is the output signal from the sensor, and the setpoint value
for the liquid level is typically set by the operator. The output signal from the controller is a
voltage or current signal that corresponds to the required adjustment to the liquid level.
The input signal to the actuator is the output signal from the controller, and the output signal
from the actuator is typically a mechanical signal that adjusts the valve to control the liquid
level.
Overall, the block diagram for a control system for liquid level in a tank is a closed-loop system
that continuously monitors and adjusts the liquid level to maintain it at the desired setpoint
value.
OR
1a. “Flow Rate” in a pipe line needs to be controlled. By drawing the physical
diagram of a flow process control loop, develop its Block diagram giving
all the details of the standard pneumatic and electrical signal ranges
involved.
Here is a description of the physical diagram and block diagram for a flow process control
loop:
Physical Diagram:
The physical diagram for a flow process control loop typically consists of the following
components:
1. Flow Sensor: This component is responsible for measuring the flow rate in the pipeline and
providing an input signal to the controller.
2. Controller: This component receives the input signal from the flow sensor and compares it
to a setpoint value. It then generates an output signal to the control valve to adjust the flow
rate in the pipeline.
3. Control Valve: This component receives the output signal from the controller and adjusts
the flow rate in the pipeline by opening or closing the valve.
4. Pipeline: This component represents the physical system being controlled, which is the
flow rate in the pipeline.
Block Diagram:
The block diagram for a flow process control loop typically consists of the following blocks:
1. Sensor: This block is responsible for measuring the flow rate in the pipeline and providing
an input signal to the controller. The input signal is typically a voltage or current signal that
corresponds to the flow rate.
2. Transmitter: This block receives the input signal from the sensor and converts it into a
standardized electrical signal, such as a 4-20 mA signal.
3. Controller: This block receives the standardized electrical signal from the transmitter and
compares it to a setpoint value. It then generates an output signal to the control valve to adjust
the flow rate in the pipeline. The input signal to the controller is typically a 4-20 mA signal,
and the output signal is also a 4-20 mA signal.
4. Control Valve: This block receives the output signal from the controller and adjusts the
flow rate in the pipeline by opening or closing the valve. The input signal to the control valve
is typically a 4-20 mA signal, and the output signal is a pneumatic signal that adjusts the
valve position.
5. Pipeline: This block represents the physical system being controlled, which is the flow rate
in the pipeline.
The standard electrical signal range for the flow sensor and transmitter is typically 0-10 V or
4-20 mA. The standard pneumatic signal range for the control valve is typically 3-15 psi or
0.2-1.0 bar.
Overall, the block diagram for a flow process control loop is a closed-loop system that
continuously monitors and adjusts the flow rate in the pipeline to maintain it at the desired
setpoint value.
OR
1b. Draw the circuit schematic for controlling the ‘heating & cooling’
of a oven and explain its automatic control operation.
2. PID Controller: The controller receives the input signal from the temperature
sensor and compares it to the desired temperature setpoint. It then generates
output signals to control the relay switch for the heating and cooling elements.
3. Heating Element: This element is activated by the relay switch to increase the
temperature inside the oven when needed.
4. Cooling Element: This element is activated by the relay switch to decrease the
temperature inside the oven when needed.
5. Relay Switch: The relay switch is used to control the power supply to the
heating and cooling elements based on the signals from the PID controller.
6. Power Supply: Provides electrical power to the control system, relay switch,
and the heating/cooling elements.
3. If the measured temperature is below the setpoint, indicating that the oven
needs heating, the controller activates the relay switch to power the heating
element.
4. If the measured temperature is above the setpoint, indicating that the oven
needs cooling, the controller activates the relay switch to power the cooling
element.
5. Once the temperature reaches the setpoint, the controller deactivates the relay
switch, turning off the heating or cooling element until the temperature deviates
from the setpoint again.
6. The controller continuously monitors and adjusts the relay switch to maintain
the temperature inside the oven at the desired setpoint.
This automatic control operation ensures that the temperature inside the oven is
regulated according to the user-defined setpoint, providing a stable and controlled
environment for the manufacturing process.
If you need further assistance with the circuit schematic or have specific questions
about the components and their connections, please feel free to ask.
2a. Show in a block diagram how the control system in Figure below would be
modified to use:
(a) Supervisory computer control, and
(b) DDC control. (5)
2b. Suppose a liquid level ranging from 5.5 to 8.6 m is linearly converted to
pneumatic pressure ranging from 3 to 15 psi.
a. What pressure will result from a level of 7.2 m?
b. What level does a pressure of 4.7 psi represent? (05)
(Is this even correct?😶🌫️🫠)
a. To determine the pressure resulting from a level of 7.2 m, we need to use the
linear conversion formula:
where P is the resulting pressure, Pmax and Pmin are the maximum and minimum
pressures, Lmax and Lmin are the maximum and minimum levels, L is the level
we want to convert.
Given:
- Lmax = 8.6 m
- Lmin = 5.5 m
- Pmax = 15 psi
- Pmin = 3 psi
- L = 7.2 m
Note: It's important to ensure that the linear conversion formula is applicable for
the specific level-to-pressure conversion being used, as different conversions may
have different formulas.
a. Provide a description of each element in the diagram and the signals that
connect the element.
b. Describe the nature of the control loops shown and an overall view of how
the process operates.
Explain the purpose of the PLC units and the computer
2D of APCT CIE-1 PDF-1
3b. A controller outputs a 4-to-20 mA signal to control motor speed from 40 to
500 rpm with a linear dependence. Calculate:
(a) The current corresponding to 375 rpm, and
(b) the value of (a) expressed as the percent of control Output. (05)
(Not sure if the answer is correct, if it’s wrong then please tell me )
To solve this problem, we can use the linear relationship between the 4-20 mA
signal and the motor speed to calculate the current corresponding to 375 rpm and
then express it as a percentage of the control output.
Given:
- 4 mA corresponds to 40 rpm
- 20 mA corresponds to 500 rpm
- We are asked to find the current corresponding to 375 rpm and express it as a
percentage of the control output.
First, we need to find the slope of the linear relationship between the current and
the motor speed:
Therefore, the current corresponding to 375 rpm is 11.658 mA, and when
expressed as a percentage of the control output, it is approximately 58.29%.
4a. A control system for a process is evaluated in terms of the three criteria.
i. Which are they?
ii. Discuss them briefly with relevant plots. (05)
i. Stability: A stable control system is one in which the output does not oscillate
or diverge when the input is constant. It is essential for the system to return to its
equilibrium state after a disturbance. Stability is typically assessed using
techniques such as the root locus plot, Bode plot, or Nyquist plot. These plots
provide insights into the stability of the system by analyzing the behavior of the
system's transfer function in the frequency domain.
ii. Performance: Performance criteria evaluate how well the control system
performs in terms of speed of response, accuracy, and transient behavior. The key
performance metrics include rise time, settling time, overshoot, and steady-state
error. These metrics can be visualized using step response plots, which show the
system's output response to a step input. The step response plot provides
information about the system's dynamic behavior and how quickly it reaches a
steady-state condition.
iii. Robustness: Robustness refers to the ability of the control system to maintain
its performance in the presence of uncertainties, variations in system parameters,
and external disturbances. Robust control systems are designed to tolerate
variations in system dynamics and remain stable and performant under different
operating conditions. Robustness can be analyzed using sensitivity functions and
robust stability margins, which provide insights into how changes in system
parameters affect the system's stability and performance.
Stability: The stability of a control system can be assessed using various plots
such as the root locus plot, which illustrates how the system's poles change with
varying controller parameters. The Bode plot provides information about the
system's gain and phase margins, indicating the system's stability and robustness.
Additionally, the Nyquist plot can be used to analyze the system's stability by
mapping the system's frequency response.
By considering these criteria and utilizing relevant plots, engineers can assess and
optimize the performance of control systems to meet desired specifications and
operational requirements.
ANS-
To calculate the error as a percentage of span in a velocity control system, we can
use the following formula:
Where:
- Measured Value is the actual velocity measured by the system (294 mm/s)
- Setpoint is the desired or target velocity (27 mm/s)
- Span is the full range of the control system (460 mm/s - 220 mm/s)
Given:
- Measured Value = 294 mm/s
- Setpoint = 27 mm/s
- Span = 460 mm/s - 220 mm/s = 240 mm/s
5a. Figure shows the P&ID for a process wherein materials A and B react in a
chamber to create product C. The reaction generates heat and pressure
within the chamber.
```
+-------------------------+
| |
| Level Recording |
| Controller |
| |
+-----------+-------------+
|
v
+------------+ +--------+----------+
| | | |
| Level | | |
| Sensor | | Flow |
| | | Sensor |
+------------+ +-------------------+
| |
v v
+------+-------+ +-----+--------+
| | | |
| Electric | | Electric |
| Transmission | | Transmission |
| | | |
+--------------+ +--------------+
| |
v v
+------+-------+ +-----+--------+
| | | |
| Combined | | Combined |
| Receiver | | Receiver |
| Board | | Board |
+--------------+ +--------------+
```
both the pressure recording pen and the transmitters. The receivers would be mounted
behind the panel board.
```
+-------------------------+
| |
| Pressure |
| Recorder |
| |
+-----------+-------------+
|
v
+------------+ +--------+----------+
| | | |
| Pressure | | Pressure |
| Sensor | | Transmitter |
| | | (Local) |
+------------+ +-------------------+
| |
v v
+------+-------+ +-----+--------+
| | | |
| Pneumatic | | Pneumatic |
| Transmission | | Transmission |
| | | |
+--------------+ +--------------+
| |
v v
+------+-------+ +-----+--------+
| | | |
| Receiver | | Receiver |
| Board | | Board |
+--------------+ +--------------+
```
recording controller and the level recorder. The combined receiver board would be
mounted in the system.
```
+-------------------------+
| |
| Temperature |
| Recording |
| Controller |
+-----------+-------------+
|
v
+------------+ +--------+----------+
| | | |
| Temperature| | |
| Sensor | | Level |
| | | Sensor |
+------------+ +-------------------+
| |
v v
+------+-------+ +-----+--------+
| | | |
| Electric | | Electric |
| Transmission | | Transmission |
| | | |
+--------------+ +--------------+
| |
v v
+------+-------+ +-----+--------+
| | | |
| Combined | | Combined |
| Receiver | | Receiver |
| Board | | Board |
+--------------+ +--------------+
```
These textual representations (It’s weird ik but that’s the best I can do~ ChatGPT)
are simplified and may not capture all the details, but they provide a basic
structure for understanding the P&ID layouts for the given scenarios. Actual
P&ID diagrams would include additional details, instrument tags, piping, and
control loops.
- **Step Response:**
- The step response plot will show the system's behavior in terms of settling
time, overshoot, and stability under the tuned PID parameters.
These plots provide insights into the dynamic behavior of the system, helping to
fine-tune the PID controller for optimal performance. Adjustments can be made
based on the observed characteristics of the system's response, ensuring a well-
balanced and stable control loop.
OR
5b.
(a) The above figure is a P&ID of a process in a chemical Industry. What do you
mean by P&ID?
(b) What is your observation, in the above diagram, as to what processes are
taking place?
Page-39 CD Johnson