Chief Delphi - PID In-Range Ideas

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baronep

26-02-2012 19:56

PID In-Range Ideas

Does anyone have any ideas about how to determine if a PID loop has settled out yet? We have our PID loop running relatively well, but I am trying to find a way to sense if the loop has settled out in order to trigger our intake system to shoot the ball. I tried if ERROR < 5 then RUN INTAKE. But it runs momentarily on the overshoot and undershoot. I was able to partially fix this by only allowing it to shoot after 3 seconds, but I feel that there is a better way to do this?

Patrick

~Cory~

26-02-2012 19:59

Re: PID In-Range Ideas

We accomplished by averaging. If the average was in range, then fire.

baronep

26-02-2012 20:41

Re: PID In-Range Ideas

Is there a VI that will do averaging for you? If not, how do you do it?

apalrd

26-02-2012 23:50

Re: PID In-Range Ideas

You combine a check of error with a timer.

The psudocode would be:

Code:



int timer = 0; //Make sure you use a signed type to prevent underflow





int delta_t = time_now - time_last; //delta_t is millisecond loop time - in LabVIEW it would be a Tick Count block and a shift register/feedback node to store the last time



if(abs(error) < threshold) timer += delta_t;

else timer -= delta_t;



if(timer <= 0) timer = 0;



if(timer >= threshold) fire();

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