Vidmas30 Posted March 1, 2012 Report Share Posted March 1, 2012 Hi, again Here's new question: I have IO-AI4AO2 and using it's AO for valve control (PID). Is there a need to do some dead band or linearize PID CV straightly to AO (819..4095)? I'm afraid if there will be fast PID, valve can go a little bit crazy.. Quote Link to comment Share on other sites More sharing options...
HigHTech Posted March 1, 2012 Report Share Posted March 1, 2012 Are you using electric actuator or pneumatic? Quote Link to comment Share on other sites More sharing options...
Vidmas30 Posted March 1, 2012 Author Report Share Posted March 1, 2012 I'm using electric actuator (4-20mA) Quote Link to comment Share on other sites More sharing options...
Emil Posted March 2, 2012 Report Share Posted March 2, 2012 I'll set the output direct, but will set low derivative action. This in most of the cases prevents the valve to go "crazy". If this will not help, let me know and I'll give you advices how to set "dead band". Quote Link to comment Share on other sites More sharing options...
Vidmas30 Posted March 3, 2012 Author Report Share Posted March 3, 2012 Thank you, Emil ! I already done it: increased I time and decreased D so that PID was slower and worked without fluctuations. But I would apreciate advise about setting dead band for the future Quote Link to comment Share on other sites More sharing options...
Emil Posted March 4, 2012 Report Share Posted March 4, 2012 Just idea - in a moment, you can keep CV in another operand - "buffer". Then, you will calculate the difference Real CV minus buffer. If this difference is within predefined range, don't activate the valve. With this logic you wil lprevent very often, short valve movements. But this can affect the precision of your control. You need ot define the "redefined range" in a way to obtain the best compromise between movements and precision. I hope this idea can be useful for you. Quote Link to comment Share on other sites More sharing options...
Vidmas30 Posted March 5, 2012 Author Report Share Posted March 5, 2012 Thank you, Emil, it will ! Quote Link to comment Share on other sites More sharing options...
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