Jump to content

PID "Portability" problem


Recommended Posts

I'm currently doing some driver creation in advance of getting actual hardware hooked up.

One of the things I have to do is use a TEC temperature controller.  This will be used on multiple stations with identical functionality, but we sort of "scrounged" for instruments, so we couldn't get the same model of TEC controller everywhere.  We have 3 different ones (Newport 3700, Keithley 2510, ILX LDT-5980 if it matters).

What I'm trying to figure out is if the PID constants that can be set on these devices are universal or not.  They'll all be using the same sensor (10K thermistor) and the same TEC (with adapters for the different plugs), and theoretically they'll all be using voltage set points to drive the TECs.

Basically, I would like to tune the PID for one setup, and then just be able to copy those values over to setups using the other two TEC controller models.  But right now I can't tell if those PID constants are equivalent across all of the devices or not.

Link to post
Share on other sites

I took a look at the manual for two of the three - the Newport and the Keithley - and from the (lack of detailed) information there, the best I can say is that there's no way to tell from the documentation whether the gain values have the same meaning for those two. It's possible but I'd say unlikely that you can copy the gains from one controller to the other and get the same results, unless it turns out that they all use the same OEM controller component internally, which wouldn't be unheard of. To determine compatibility, at a minimum you'd need know the units of the controller gains - for example, is Ki relative to minutes, seconds, ticks of the controller's internal clock, or something else entirely? I don't see that information in the manuals.

Link to post
Share on other sites
  • 2 months later...

If response time isn't important, you can probably use non-aggressive settings on all that will get to the right temp eventually, but the design of the controllers and their implementation of PID can be very different.

Or, you could do the PID in Labview and just use a power driver driver module for each loop. I did a test stand several years ago running 14 TEC temp control loops using homebuilt current driver amplifiers and an MCC USB-3105. I discovered later that Velleman makes a nice little DC input to PWM power driver kit for about $20:

http://www.jameco.com/z/K8004-Velleman-DC-to-Pulse-Width-Modulator-Kit-Control-DC-Motors_120539.html

Or you could use a DIO output driving MOSFETs or solid state relays for slow PWM (aka time proportioning). I wrote a LAbview time proportioning vi that will do a nice job with cycle times of 1 sec or greater, especially with the 1mS resolution offered by the Wait mS Multiple function since Windows 7. I can send or post if you like.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Similar Content

    • By Georgesun
      I think you can try this example. Changing K does not change his rise time. And by decreasing the value of K, he becomes more unstable.
      I Hope someone can answer my doubts.
    • By Morbo
      Hello,
       
      why does aurotune not work in the attached vi? Plus if I change the setpoint, shouldnt the PID output change as well? I.e., if say the pump needs to pump more, has to spin faster? or at least, have to ramp up once to fill to a new level and then oscillate again, since the amplitude is the same.
       
      Its a squarewave on the input, the help says, when the process is oscillating, outotune should come up with something. The squarewave kind of oscillates just around 2 levels?
       
      Thanks,
       
      MorboPID 01 autotune.vi
    • By Alessandro Pezzano
      Hello,
      I found an example of an On-Off controller on Labview that I am attaching. I wanted to see how it would work the same VI replacing the thermostat a PID block and using the simplified model of a room in the form of the transfer function (R / (RCS +1)) but I'm not sure the right way to proceed. the integrator is to stay?  I have to connect directly with the pid of the entrance to the furnace? I have to modify the VI?  I hope in your kind suggestion 
       
      thanks
      Alessandro
      On-Off Controller modificato.vi
      On-Off Controller.vi
    • By Stobber
      Even after thre semesters of controls study in my BSEE program and multiple projects with manually tuned PID systems, I still feel like it's something of a black art. I've met oldschool engineers at my clients' offices with a preternatural talent for tuning PIDs, but when I asked them what their approach was, they couldn't really describe it. Just "intuition".
       
      What's your favorite book, tutorial, or other resource on tuning PIDs by hand? I've read all the Wikipedia articles and free online tutorials presented by college undrgrads or companies with a product to sell. I'm looking for the real deal here, the authentic guide to tuning mastery!
    • By Bruno Costa
      The control group are displayed when the user clicks on sinoptic area. Initialy displayed in float mode, but the user can dock this window in a fixed position of the groups panel.
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.