Start the pid with initial value ? #1

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1. mkner commented on Jun 3, 2024

   

   mkner

   on Jun 3, 2024

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   it depends on which initial values you want to set: you can set the gains to initial values before beginning time-step iterations, or if you want to set an initial value for the control signal you are sending to some device or process plant then you can use BasicPid in iterative mode (instead of integrative mode) and handle the time-step integrations manually in a loop see some examples in RTD for BasicPid for more @ https://basic-pid.readthedocs.io/en/latest/examples.html
2. ewok2 commented on Jun 4, 2024

   

   ewok2

   on Jun 4, 2024

   Last edited by ewok2

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   I just had to change the pid.py file to achieve my goal :-)
   I just add the folowing function :

        def setInit(self,initial):
            # set initial value
            # keeps gains intact
            self._P = 0
            self._I = 0
            self._D = 0
            self._e_prev = 0 # previous error (t-1)
            self._e_prev_prev = 0 # prev-previous error (t-2)
            self._pid_out = initial
            self._pid_out_prev = initial
   

   just befor the reset function, and it works

   I just have to call "pid.setInit(initalvalue)" befor the loop
3. mkner commented on Jun 6, 2024

   

   mkner

   on Jun 6, 2024

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   yep, you got it! just jump start the 1st iteration with initial PID evaluation (output) values. Did you then just run PID in integrate mode? I designed & coded BasicPID to be clean & logical so can be relatively easy to modify & customize. I was going to put in an interface function for setting initial values but left it for the first stable release. I will put it in for the next. thanks for asking about this. any feedback is welcome.
4. ewok2 commented on Jun 7, 2024

   

   ewok2

   on Jun 7, 2024

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   The only feedback is : wonderful job
   The code is clear and it was easy to add a new input point.
   Wonderful if you add this functionality in next release. I will pug on it when avalaible

   Many Thanks