Pendant control System has been designed as followed:
1. Functional Design Specification is made explaining in detail the process.
2. Work Progress report is made with the Bill of material specification.
3. Ladder Logic of the Process is also shown.
4. I/O mapping is done as well.
3. INTRODUCTION
Previously in industrial crane operations, all the control devices were
wired in the old-fashioned way which would operate a specific function
of a crane. All the system was controlled by human previously that had
long and complex wirings which led to big mechanical faults at that
time. The repair work also used to be difficult which caused a decrease
in industrial production.
We would be using PLC to control the crane movements.
Programmable Logic Controller (PLC) is a small computer used for
automation of real-world processes, such as control of machinery on
factory assembly lines. In other words, PLC is a digitally electronic
device which has a programmable memory that stores instructions and
implements functions such as Boolean logic, sequencing, timings,
counters, arithmetic operations etc.
The PLC usually uses a microprocessor. The program can often control
complex sequencing and is often written by engineers. The program is
stored in battery-backed memory and/or EEPROMs.
Unlike general-purpose computers, the PLC is packaged and designed
for extended temperature ranges, dirty or dusty conditions, immunity
to electrical noise, and is mechanically more rugged and resistant to
vibration and impact.
By implementing this project, we decrease the man power, thus
increase in production of the industry.
4. WORKING
Process:
Create a ladder logic to implement crane operation in two
different motions such as X, Y. (where X= up and down,
Y= forward and reverse).
Check the ladder logic via simulation in Delta software WPLSoft.
Selection of other components such as motors, drives,
switchgears, inputs, sensors, PLC
Design of the pendant control system and the crane.
Implementation of I/O mapping
PLC OPERATION:
A PLC works by continually scanning a program. We can think of
this scan cycle as consisting of 3 important steps. The steps are
reading the input, execution of logic, and giving the output. There
are typically more than 3 but we can focus on the important parts
and not worry about the others. Typically, the others are checking
the system and updating the current internal counter and timer
values.
5. Input Scan- The status of external inputs is written to the internal input
image table.
Execute program- Each ladder rung is scanned and solved using the
date in the input file. The resulting logic is written to the output image
table.
Output Scan- The output image data is transferred to the external
output circuits, turning the output device ON or OFF.
PLC SCAN CYCLE
6. Input/output Module Checks- Internal check on memory, speed and
operation.
Mechanical Parts Required:
6 pushbuttons
2 switches
Display Unit
Ideal Pendant Diagram
Start/Reset Button
Emergency Stop Button
Upward Motion
Downward Motion
Forward Motion
50Hz frequency speed
25 HZ frequency speed
Reverse Motion
7. Functional Block Diagram
Start
Initially upward button is pressed with 50HZ
frequency speed switch pressed
The PLC receives signal and gives command to hoist starts to
move in the upward motion at full speed as motor gives the
maximum output
Aftera certaintime 25HZ frequencyspeedswitch is pressed and
thus the speed of motor decreases by half.
When the hoist reaches the uppermost point the gravity limit
switch gets triggered which stops the motors upward motion.
Forwardpushbuttonispressed;loadstartstomove in horizontal
direction till it reaches the desired destination.
Then downward motion pushbutton is pressed with 50HZ
frequency speed switch.
Aftera certaintime,the 25Hz frequencyspeedswitchispressed
and the sped is decreased.
Hoist comes to halt after reaching the lowermost position.
The same process occurs to go back to the initial first position.
8. CONCLUSION
PLCs have the great advantage that it is possible to modify a control
system without having to rewrite the connections to the input and
output devices, the only requirement being that an operator has key in
a different set of instruction.
The soft wiring advantage provided by programmable controllers is in
fact really helpful. In fact, it is one of the most important features of
PLCs. Soft wiring enables us to do changes in the control system in an
easy and cheap way. If we require a device in a PLC system to behave
differently or to control a different process element, all have to do is
change the main program. In a traditional old system, implementing
such type of change would require us to physically change the wiring
between the devices, which is a lot costly and time-consuming process.
It is sure though that in the near future it is PLC that will be used by
everybody than other methods of controlling as the country as only
scratched the surface of it. Still a large percentage of industries in India
run on old tradition methods.
In India less than 1% of manufacturing GDP comes from automation
and instrumentation whereas in developed economies it is 5%. Only big
Multi-National Companies use industrial automation in full fledged
manner in India. India holds a very bright future in this field as there is a
lot of scope.
9. COMPONENTSUSED
1. Allen Bradley PLC
1762-L24BWA MicroLogix 1200
No. of I/O – 40.
2. RsLogix 500
Standard Edition from Rockwell.
3. RsLinx Classic
communication software from Rockwell.
4. Factory Talkview Studio- SCADA
5. Motor
Bharat Bijlee, 3.7KW 4 pole motor.
Model- MA11M433
5HP, 415V, 1500RPM, IP55, 50Hz
6. VFD
Delta 037/E series
7. Sensor
Diffuse Reflective Sensor
OMRON- E3FADN23
1m sensing distance