Manufacturing Automation for Assembly and Inspection MM453
Manufacturing Automation for Assembly and
Inspection
MM453
Dr. Nigel Kent
Rm S366
nigel.kent@dcu.ie
Dublin City University
Sem 1 2022
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Lecture 5
Dr. Nigel Kent Manufacturing Automation for Assembly and Inspection, MM453 2/25
Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagrams
In response diagrams the states of the inputs and outputs are
plotted against time and synchronised.
• In the conveyor example a
1
heavy item is detected at 2 A
seconds and 9 seconds 0
which causes the output to 1
Y
go on for 4 seconds
0
afterwards in each case.
• The inputs are assigned by 0 5 10 15 Time (seconds)
the system designer and are
arbitrary but should cover all
possible situations.
• The outputs then follow
from the logic of the system.
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagrams
AND Gate Response Diagram
1
A
0
A
Y = A.B
B
1
B
0
1
Y
0
0 5 10 15 Time (seconds)
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagrams
1
A
0
A
Memory
Y
B
1
B
0
1
Y
0
0 5 10 15 Time (seconds)
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagrams
Off Dominant Memory
1
A
0
A
Memory
Y
B
1
B
0
1
Y
0
0 5 10 15 Time (seconds)
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagrams
1
A
0
A
Memory
Y
B
1
B
0
1
Y
0
0 5 10 15 Time (seconds)
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagrams
On Dominant Memory
1
A
0
A
Memory
Y
B
1
B
0
1
Y
0
0 5 10 15 Time (seconds)
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagrams
1
A
0
A
Memory
Y
B
1
B
0
1
Y
0
0 5 10 15 Time (seconds)
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagrams
Static Dominant Memory
1
A
0
A
Memory
Y
B
1
B
0
1
Y
0
0 5 10 15 Time (seconds)
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example
Example - Cooling System Requirements
• Machine Y is turned on/off with a toggle switch A.
• The machine needs cooling Z which runs for 3 minutes after
the machine is switched off.
Task: Design the control logic for the machine and the cooling.
Use a timer where appropriate.
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example
Inputs Outputs
A = 0 machine is switched off Y = 0 machine is switched off
A = 1 machine is switched on Y = 1 machine is switched on
Z = 0 fan is off
Z = 1 fan is on
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example
1
A
0
1
Y
0
1
Z
0
0 5 10 15 20 25 Time (mins)
Points to note:
• Y follows A exactly.
• Z remains on 3 minutes after A is turned off.
• The sequences after 20 minutes illustrates that Z is timed after the
final switching of A.
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example
Logic Networks
Y =A
A Y
Z = A or 3 mins after A
A
Z
?
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example
Logic Networks
Y =A
A Y
Z = A or 3 mins after A
A
TON Z
?
Time 3min
When the simple delay is running its output will be low. To keep Z
on during this time we need to negate the output from the timer.
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example
Logic Diagram
A Y
TON Z
Time 3min
The timer is initiated when A is switched off, therefore use NOT A
(A) to start the timer.
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example
Ladder Logic Diagram One may start from scratch or encode
from the logic network diagram.
A Y
A Z
From observing the logic network. The OR inputs are A and an
input from a NOT function. Given the function is a NOT function,
use a closed contactor.
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example
This NOT function is the output from a timer triggered with NOT
A
A D
TON
Time 3min
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example
A complete ladder logic diagram solution therefore looks like:
A Y
A Z
A D
TON
Time 3min
Exercise: Investigate the functionality of the TOF timer and
implement the same logic using this timer type.
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
A gas fueled furnace is used to heat blanks prior to forging.
There is a flame detection system F to detect that the furnace is
firing.
The power command P to the system is switched manually.
During start up or in the event that the flame goes out, the ignition
system I is switched until the flame appears or 5 seconds elapse.
If no flame appears after 5 seconds the gas G is turned off and an
alarm A is switched on.
Design the logic to control the system.
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
G
F
V
P I A
Inputs Outputs
PLC
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
Inputs Outputs
P = 0 Power is off G = 0 Gas valve is closed
P = 1 Power is on G = 1 Gas valve is open
F = 0 Flame is off I = 0 Ignition is off
F = 1 Flame is on I = 1 Ignition is on
A = 0 Alarm is off
A = 1 Alarm is on
Remember that the inputs are with reference to the control system.
So even though the fuel may be an input to the furnace, the signal
to the control gas valve is an output from the controller
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
Response Diagram Scenarios
• Consider turning the power on with no flame until 3 seconds
later.
• Then consider a momentary loss of flame which reappears
when the appropriate action occurs.
• Then consider an extended period of flame loss after which
the power is turned off manually.
• Then consider a spurious short flame signal while the power is
off.
• Finally consider switching the system on but no flame appears
even after 5 seconds.
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
P
0
F
0
G
0
I
0
A
0
0 5 10 15 20 25 30 35
Time (mins)
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
Logic Network Development
Working back from the outputs it can be determined that the gas
G is on when:
1 Both the power and the flame are on
or
2 Both power and the ignition is attempting to fire
P
F G
? I
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
The ignition I is switched on if
1 Power P is on
and
2 There is no flame detected
and
3 The time limit is not exceeded
P
F G
TON I
Time 5s
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
The timer is initiated when The alarm is switched on when:
1 Power P is on 1 Power P is on
and and
2 There is no flame F 2 There is no flame F
and
3 5 Seconds have elapsed
P
F G
TON I
Time 5s
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
Ladder Logic
This diagram is a literal translation of the previous logic diagrams.
There are sometimes a few more simplifications we can mke using
ladder logic. Care should be taken not to oversimplify and leave the
original design intent unclear to someone reading your code later.
P F G
P I
P F A I
P F A
TON
Time 5s
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Manufacturing Automation for Assembly and Inspection MM453
Lecture 5
Response Diagram Example 2
Ladder Logic
We can simplify the previous diagram by recognising that for I to
be high P needs to already be high. This negates the need for the
explicit programming of the P contact being ”OR’ed” with I on
the G rung.
P F G
P F A I
P F A
TON
Time 5s
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