Internet PLC Forum
General => Technical support => Topic started by: k1w1 on August 22, 2008, 03:09:42 AM
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Hi
Starting a new project in which I need to use the PID function in the T100MD 888
What I would like to do is use the T100MD as an variable engine speed governor utilizing the 0-5vSetDAC o/p and monitoring drive shaft speed for feed back keeping within 120 (700rpm) to 230 (1250rpm) Hz limits The operator will vary speed with increase and decrease speed switches
I assume result of these custom functions ( Stored DM[11] ) will become the Set Point value.
What I'm not sure about is how to work out what values to use in the PID compute function.
Any help appreciated
Pete
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The basic PID computation is illustrated in the example in Appendix section in the TRiLOGI programmer's reference guide. You have a set point value and the measured value and the difference E is the "error" that is used to compute the necessary amount of action to be sent to DAC.
Since each system has different dynamic only you are able to really decide what are the PID parameters to be set. There are some books out there illustrating PID tuning concept. Usually a P or P+I system would suffice and it is rare to need to use the D function. Start with small value of P and I and conduct experiment to test the effect. Good luck.