I am trying to create a auto tuning PID function for a RH controller. Any ideas?
I have a RH controller. I am using a 100 ohm RTD sensor with a 300 pF humidity sensor. The sensor is compensated with temp.
Now I want to try and auto tune the output. I don't know the response time for the SES heater and cooler.
Thank You for replying to my email.
That was an excelent link. Thank you very much for showing me the link. I need to study the PDF file allot more.
Auto-tuning is difficult. Since we don't know how your control loop should look like, it is difficult to auto-tune the parameters (esp. when you don't know the parameters of the loop).
It might be better to measure the behavior of your control loop when it is oscillating, and then use the Ziegler-Nichols-method: http://en.wikipedia.org/wiki/Ziegler%E2%80%93Nichols_method .
@hli, interesting reference.
This seems to state in a degenerative way, if I can't get the loop to oscillate, eg. not
enough gain, just use, what is in effect a step response, to characterize the T(s). If
you take the response at two different time points, and you know the order of the PID,
then the rest falls out.
Or a test cycle, breaking the loop, to characterize the feed forward paths and feedback
Quite a few ways to at at this I suspect.
A fairly good overview -
Everyones input is correct. I have built analog PIDS a long time ago. But it may be simpler to buy an off the shelf PID controler.
I am looking at PID controlers on the Web. I have seen them form $80 to $300. The only problem that I face is the PSoC 3 has a DAC that is only 8 bits. I am looking at adding an external DAQ and control it with SPI. I would like at least a 12 bit DAC.
Thanks For the great feedback. I deal PIDS all the time at work. And they are very tricky to tune.
Expanding DAC resolution, but may be too slow for PID -
You could also use a PWM as a DAC. You would have to take into account
settling time of its mandatory LPF or Integrator on its output. Ap notes from
some other vendors -
There is a PSOC 1 project you could adopt / port to PSOC 3 -
This is not auto tune, but you could always modify.
What are the requirements for the autotune functionality ?
There has been quite a bit of re-organisation in the PSOC sites and the following link does not work anymore.
Can you provide a new working link or send me the PSOC Project? we are doing something similar and would like to save some time.
The app note