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???
11/27/04 14:36
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#82077 - Answering the question
Responding to: ???'s previous message
The problem with PID systems isn't necessarily the maths of implementation, its the tricks of tuning, handling saturation effects, like integrator windup and noise in numerical differentiation to end up with a stable, fast settling system.

It seems to me we are focussing on the wrong bits here. IF he sees problems with rounding, speed, or program size then worry about Floating point or fixed point. I have used both successfully, but my sampling periods are usually in the seconds area than the msec area.

And tuning is STILL an art.

One of my ex-employees, and whose help I miss used limit cycle oscillations to tune PID loops, he could find good parameters,but his implementations were poor, and suffered from windup etc etc.

I couldn't do the analysis, but could write robust algorithms.

Some proper guidance on TUNING would help everyone (especially me ! ) greatly.

Bruce, We are using a Peltier cooler on one of our instruments with an analogue loop and a digital loop - we didn't find any improvement from tweaking parameters. What kind of things are you doing with yours ? We have to operate at 7 fixed temperatures, -10.0, 15.0, -20.0, -25.0, -30.0, -35.0 +/- 0.05 C

Steve

List of 28 messages in thread
TopicAuthorDate
help about pid            01/01/70 00:00      
   Floating point?            01/01/70 00:00      
      Keil floating-point performance            01/01/70 00:00      
   Search the forum            01/01/70 00:00      
   Floating Point Vs Mixed point            01/01/70 00:00      
      You mean Fixed Point            01/01/70 00:00      
         Mixed not Fixed            01/01/70 00:00      
   Warnings about Floating Point            01/01/70 00:00      
      Shortcuts            01/01/70 00:00      
         Implied aka Fixed point            01/01/70 00:00      
      Another Shortcut            01/01/70 00:00      
         Answering the question            01/01/70 00:00      
            Autotunning?            01/01/70 00:00      
            PID Tricks and Tuning            01/01/70 00:00      
               Great Stuff !            01/01/70 00:00      
                  I followed your idea...            01/01/70 00:00      
                  Another couple tricks            01/01/70 00:00      
                     tests            01/01/70 00:00      
                        limit cycle tuning            01/01/70 00:00      
         PID to control a Peltier            01/01/70 00:00      
            An idea to try            01/01/70 00:00      
   very fast 20ms ???            01/01/70 00:00      
      20.000, not 2000.            01/01/70 00:00      
      very fast 20ms ???            01/01/70 00:00      
         in points...            01/01/70 00:00      

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