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Revision Notes for CIM360S: Automation Concepts & PLC
Programming
Industrial and Systems engineering (Cape Peninsula University of Technology)
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REVISION
QUESTION 1
a) Define the following terms as they are used in automation.
(i) Logic control.
(ii) NOT gate.
(iii) Robot program.
(iv) Linear joint.
(v) A wrist assembly.
b) Name and describe the following body-and-arm robot configurations including the
joints involved.
(ii)
(i)
(
c) The steps in the PLC control program are executed simultaneously and
continuously. Describe the PLC Operating Cycle.
d) An industrial furnace is to be controlled as follows: The contacts of a bimetallic
strip inside the furnace close if the temperature falls below the set point, and
open when the temperature is above the set point. The contacts regulate a
control relay which turns on and off the heating elements of the furnace. If the
door to the furnace is opened, the heating elements are temporarily turned off
until the door is closed. (a) Specify the input/output variables for this system
operation and define symbols for them (e.g., X1, X2, C1, Y1, etc.). (b) Construct
the ladder logic diagram for the system. (c) Write the low level language
statements for the system using the PLC instruction set in the annexure.
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REVISION
e) An NC worktable operates by closed loop positioning system. The system
consists of a servomotor, leadscrew and optical encoder. The leadscrew has a
pitch of 8.0mm and is coupled to the motor shaft with a gear ration of 5:1 (five
turns of the drive motor for each turn of the leadscrew). The optical encoder
generates 50pulses/rev of its output shaft. The table has been programmed to
move a distance of 200mm at a feed rate = 500mm/min. Determine:
(i)
How many pulses should be received by the control system to verify that
the table has moved exactly 200mm,
(ii)
The pulse rate of the encoder
(iii)
The drive motor speed that corresponds to the specified feed rate
ANNEXURE 1:
Typical low-level language instruction set for a PLC
STR
Store a new input and start a new rung
T
Logical AND referenced with the previously entered element. This is
interpreted as a series circuit relative to the previously entered element
OR
Logical OR referenced with the previously entered element. This is
interpreted as a parallel circuit relative to the previously entered element
NOT
Logical NOT or inverse of entered element
OUT
Output element for the rung of the ladder diagram
TMR
Timer element. Requires one input signal to initiate timing sequence.
Output is delayed relative to input by a duration specified by the
programmer in seconds. Resetting the timer is accomplished by
interrupting (stopping) the input signal
CTR
Counter element. Requires two inputs: one is the incoming pulse train that
is counted by the CTR element, the other is the reset signal indicating a
restart of the counting procedure
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REVISION
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