WRITTEN EXAM
Course: Industrial Automation
Course code: R7008E
Number of examination hours:
Date of examination:
5
2023-08-25
Allowed aids: No aids
On duty teacher (complete telephone number):
On duty teacher (complete telephone number):
Achilleas Seisa 0730926670
On duty teacher (complete telephone number):
On duty teacher (complete telephone number):
Grade scale:
Number of questions and total score:
3 (10 Points), 4 (16 Points), 5 (20 Points)
4 Problems, 20 Points
Other information:
Complete solutions are required for full credit. You can use the existing drawings for placing sensors and
actuators (where this is being asked) but do not forget to attach the current document with your solutions.
General instructions
Check that you have received all the exams/questions.
All new answers begin on a separate page. Do not write on the back page.
Print, write clearly, and do not use red pen.
After examination
Examination results will be announced within three weeks from the examination date and no later than two weeks before next
re-examination. The exam result can be seen at My LTU – Ladok for students. Your corrected exam is scanned and visible on
My LTU – Graded exams.
Information to the printer
Project number:
341980
Number of copies: 2
Other information:
Klicka eller tryck här för att ange text.
Number of pages: 4
Problem 1 [5 Points]
In the following figure the shorting process of incoming parts is taking place, based on their
height. From the three types of the incoming parts, the two of them will be forwarded to the
conveyor belts M1 and M2 through the pistons E1 and E2, while the third one will continue in
the main conveyor belt M3. Each piston should forward every time only one kind of parts, while
the number and the sequence of arrival for the parts is random.
Desired Operation of the automation
-
The automation is ready to start through a general switch D (0-1).
After this start the conveyor belts M1 and M2 start and continuously remain in operation.
The conveyor belt M3 is also set in operation but it should stop whenever a piston is
forwarding a part, as well as during the return of the piston to its initial position.
The placement of the photo switches is vertical and already defined as indicated in the
figure. However, you have to select the heights of placement for the photo switches and
correspondingly select the pistons for detecting the different boxes.
Define the position and the type of all additional sensors that might be utilized to perform
the desired automation
The motors M1, M2 and M3 are all of a direct start.
Define based on your judgment and experience, any other kind definition of equipment,
sensors, etc. that have not already specified and might be needed (not necessary is missing
something).
Questions
-
[1 Points] Design the pressurized air circuits (valves, cylinders, etc.)
[5 Points] Design the overall low power circuit
2
Problem 2 [5 Points]
We would like to design an industrial automation that will be able to select two liquids from two
different silos and forward them to the mixing chamber by the utilization of two corresponding
linear pneumatic pistons, with the following functionalities:
1.
The selection of the flow for each liquid is happening with a selective switch S2 (one
liquid can and should flow each time).
In case that the selective switch S2 is placed at the ‘A’ position and at the same time
the push button “S1” is pressed, then we have a flow of the liquid form the A silo to
the mixing chamber.
In case that the selective switch S2 is placed at the ‘B’ position and at the same time
the push button “S1” is pressed, then we have a flow of the other liquid form the B
silo to the mixing chamber.
The flow of the liquid from silo A is happening with the help of a hydraulic cylinder,
commanded by an electrovalve SV1, that pushes the liquid out.
The flow of the liquid form silo B is happening with the help of a hydraulic cylinder,
commanded by an electrovalve SV2, that pushes the liquid out.
Both cylinders when not in operation are self-returning to their initial state without
any direct command.
When one of the cylinders is executing the returning operation, the other one cannot
be energized until the return is finished.
2.
3.
4.
5.
6.
7.
Questions
-
[1 Point] Draw the overall automation, including the sensors, the valves, the silos, the
mixing chamber, and the pneumatic actuators.
[4 Points] Design the overall low power automation.
3
Problem 3 [5 Points]
Consider the chemical reactor shown in the following Figure where two different liquids are
mixed in order a new product to be produced under concrete stirring and temperature conditions.
The mixing process starts only if the “Operation Cycle On” condition is true and is realized by a
simple On-Off switch. If during a mixing process the condition is confuted, the mixing process
continues until the end of operation cycle and then the reactor stops to operate. The mixing
process must follow the next seven steps.
1. The valve V1 closes.
2. With precondition that the valve V1 has been started to close, the refrigerator (RFG) starts
to operate and simultaneously the valve V2 opens. The valve V2 remains open until the
liquid A level inside the reactor reaches the height L2 detected by a corresponding sensor.
3. With step 2 completed, the stirring impeller (STR) starts to operate. The stirring impeller
and the refrigerator stop to operate at the end of mixing cycle.
4. With precondition that the stirring impeller operates, the valve V3 opens and remains open
until the liquid B level reaches the height L3 detected by a second corresponding sensor.
5. With step 4 completed, a time interval of 40 min follows for mixing and chemical reaction
of the two liquids.
6. At the end of this reaction period the valve V1 opens and the reactor starts to empty.
7. When the level of the produced liquid drops in height L1, then the valve V1 closes and a
new operation cycle begins if the corresponding condition exists.
Questions
[5 Points] Solve the problem with the utilization of state diagrams and provide a full solution for
the final automation circuit.
4
Problem 4 [5 Points]
In a process station, a cylinder pushes objects – one object at a time – from position ‘1’ to the
positions ‘2’, ‘3’ and ‘4’, in order to undergo the corresponding treatment. After the end
treatment, the cylinder returns to its initial position. You are prompted to resolve just only this
part of automation relating to the movement of the cylinder according to the following
specifications:
1. The piston rod slides one place at each press of the button ‘b’.
2. The sliding is sequential, cyclic and non-reversible and therefore from the rest position ‘1’,
with the 1st pressing of the button ‘b’ the piston rod slides to position ‘2’
-//- 2nd
-//‘3’
rd
-//- 3
-//‘4’
-//- 4th
-//returns back to
‘1’
-//- 5th
-//‘2’ and so on.
3. The position sensing of the piston rod is achieved via the magnet ‘M’ situated inside the
cylinder and the reed switches mounted outside of the cylinder. When the magnet is in front of
a reed switch, its NO contact closes.
Reed Switch
Magnet
b
M
1
2
3
4
Questions
[5 Points] Select a suitable pneumatic directional valve and design the overall required
automation circuit.
5