ABB IRC5P, Product Manual, Page: 179 / 220

8 Trouble Shooting
Product Manual, Control Cabinet IRC5P 3HNA009834-001 en Rev.06 179
8.3 Fault Symptoms and Malfunctions
8.3.5 Controller Performance Slow
Description
The controller performance is slow, and seems to work irrationally.
The controller it not completely ‘dead’. If it is, please proceed as described in
section ’Controller Dead’ on page 178.
Consequences
These symptoms may be observed:
• Program execution is sluggish, seemingly irrational and sometimes stalls.
Possible Causes
The computer system is experiencing too high load, which may be due to one or
more of the following:
• Programs containing too many logical instructions without Wait or Move-
instructions, causing too fast program loops and in turn, overload the processor.
• The poll rate of the I/O units is set too low, overloading the I/O system.
• Internal system cross connections and logical functions are used too frequently.
• An external PLC, or other supervisory computer, is addressing the system too
frequently, overloading the system.
Recommended Actions
Step Action Comment
1 Check whether the program contains almost
only logical instructions (or other instructions
that take ‘no time’ to execute), since such
programs may cause the execution to loop if no
conditions are fulfilled. To avoid such loops, you
may test by adding one or more WAIT
instructions. Use only short WAIT times, to
avoid slowing the program down unnecessarily. Suitable places to add WAIT instructions
may be:
– In a WHILE/FOR/GOTO loop,
preferably at the end, close to the
ENDWHILE/ENDFOR etc. part of the
instruction.
– In an auto-looping background task,
ref. Rapid OverView/Multitasking
2 Make sure the poll rate value for each I/O board
is not too low. These values are changed using
RobotStudio. I/O units not requiring to be polled
regularly may be switched to ‘change of state’
operation as described in the RobotStudio
manual. ABB recommends these poll rates [ms]:
– DSQC 651: 1000
– DSQC 652: 1000
– DSQC 653: 1000
– DSQC 377: 20-40
– All others: >100
3 Check whether there is a large amount of cross
connections or I/O communication between
PLC and robot system. If required, try to reduce
the communication. Too much communication with PLCs or
other external computers will load the
robot system main computer.
4 Make sure there is little unnecessary
communication between any supervisory PLCs
or other computer. Make sure the PLC is
programmed in such a way that it does not, for
example, request robot system state changes
that are not allowable, by letting the PLC
monitor robot system state through a digital
input. Also make sure, that such state change
requests are not issued too often. The robot system have a number of
fixed system inputs and outputs that may
be used for this purpose. Too much
communication with PLCs or other
external computers will load the robot
system main computer.