kamenges
Member
Unless you are really strapped for processing power I would put all the PIDs into a single periodic task and run it at the fastest update time.
Keith
Keith
• Loop Sample Time, T
Process time constant, Tp, is the clock of a process. The size of Tp indicates the maximum desirable loop sample time. Best practice is to set loop sample time, T, at 10 times per time constant or faster (T ≤ 0.1Tp). Faster is equally good but not better. Slower than five times per time constant leads to significantly degraded performance.
Originally posted by plcnovel:
SO in my example the period task will run at a period of 3.4 sec (highest loop update time)
kamenges said:...I assumed you already performed the divied by 10. ...
kamenges said:As Alaric said, you want the FASTEST uldate time, not the longest. When you listed your PID loop updates I assumed you already performed the divied by 10. So when you listed the loop update rate for PID4 it is based on a controlled process time constant of 2.5 seconds. If this is true, use the update time for PID4 (0.25 sec) as the task period.
Keith
kamenges said:Did you go online and check for any major or minor faults? That would be my first action item. The processor should be able to tell you what made it mad.
Keith
kamenges said:This may seem like a silly question but did you check for faults BEFORE you cycled the keyswitch? I don't remember if the fault display screen hangs onto the last fault or not. It may clear when the processor restarts if the fault is not present.
Keith