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operation of PID
- Thread starter edenuh
- Start date
Skogsgurra
Electrical
This is a very typical school question. Too general.
What exactly do you want to know?
Gunnar Englund
What exactly do you want to know?
Gunnar Englund
- Moderator
- #3
Start with the P in PID.
This is your proportional band, and is equivalent to the droop, The less proportional band, the less droop. This is the difference between no-load speed and full load speed. Droop is measured in RPM, proportional band is measured in percent. I'll leave integral and derivative for someone else to answer.
yours
This is your proportional band, and is equivalent to the droop, The less proportional band, the less droop. This is the difference between no-load speed and full load speed. Droop is measured in RPM, proportional band is measured in percent. I'll leave integral and derivative for someone else to answer.
yours
P = proportional band = sensivity of response. A wide band = slowly approach the correct process value.
I = integral time = offset correction timer. If everything is stable but set point and PV don't match, integral works on this.
D = derivative time. Anticipates future PV and overrides normal PI control if something is rapidly changing.
I = integral time = offset correction timer. If everything is stable but set point and PV don't match, integral works on this.
D = derivative time. Anticipates future PV and overrides normal PI control if something is rapidly changing.
Gesh Mike that was a simplified explanation if I ever heard one. But it works!![[lol]](/data/assets/smilies/lol.gif "[lol] [lol]")
edenuh; The short answer is the better the PID settings the "better" the governor will control. It also means that miss setting the PID will result in virtually no control or dangerous oscillations.
edenuh; The short answer is the better the PID settings the "better" the governor will control. It also means that miss setting the PID will result in virtually no control or dangerous oscillations.
The most basic basic idea behind a PID controller is how much, and how fast any correction is applied.
Not enough, or too slow gives poor and sluggish correction. Too much or too fast can over correct, causing stability problems and even continuous cycling.
PID tuning is selecting "how much" or gain, and "how fast" integral (and derivative if actually used).
Not enough, or too slow gives poor and sluggish correction. Too much or too fast can over correct, causing stability problems and even continuous cycling.
PID tuning is selecting "how much" or gain, and "how fast" integral (and derivative if actually used).
i.e. the PID is a device to establish a compromise
between the accuracy, speed of reaponse,stability
etc. within the physically possible limits to approximate
-- as well as possible -- the impossible requirements.
Engineering is the science of compromise.
<nbucska@pc33peripherals.com> omit 33 Use subj: ENG-TIPS
Plesae read FAQ240-1032
between the accuracy, speed of reaponse,stability
etc. within the physically possible limits to approximate
-- as well as possible -- the impossible requirements.
Engineering is the science of compromise.
<nbucska@pc33peripherals.com> omit 33 Use subj: ENG-TIPS
Plesae read FAQ240-1032
coconutalley
Electrical
Another stab at it:
The way I look at it:
Proportional gain is for controlling the amplitude or scaling.
The integrator fixes the steady error which is often
an offset from the setpoint.
The derivative sets the damping. It fixes how fast the
overshoot or ringing gets damped or aligned with the target
[setpoint].
The traditional way to tune PID is to start with just the proportional with everything else set to zero. Then adjust the integrator to eliminate the offset, then adjust the
derivative to get the damping. However, these are all interrelated and may have to tweaked each other 'til you
get. If you search google, I'm pretty sure you'd find several methods of doing this.
The way I look at it:
Proportional gain is for controlling the amplitude or scaling.
The integrator fixes the steady error which is often
an offset from the setpoint.
The derivative sets the damping. It fixes how fast the
overshoot or ringing gets damped or aligned with the target
[setpoint].
The traditional way to tune PID is to start with just the proportional with everything else set to zero. Then adjust the integrator to eliminate the offset, then adjust the
derivative to get the damping. However, these are all interrelated and may have to tweaked each other 'til you
get. If you search google, I'm pretty sure you'd find several methods of doing this.
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