Since87
I looked through the book and the flowcharts seem to explain things the best so here they are.
The pic shows all three modes P, I and D. The charts work on the basis that all three are working in parallel off the same process variable. I don't know how much you know about control theory so I ll explain the charts just a bit.
P mode -
DE = error, DV = process variable, DSP = setpoint, CORR = proportional correction, KP = proportional gain, P = proportional output, P0 = output bias
I mode -
DE, DV and DSP are the same as from P mode, sum = sum of errors, PI = integral output, KI = integral gain, DT = change in time between error samples.
D mode -
DE, DV and DSP are the same as before, DDE = the difference between current error sample and previous error sample, DEO = previous error sample, PD = derivative output, KD = derivative gain.
So If you want PI control all you do is implement the P and I flowcharts add the results together (controller output = P + PI) and there you go. For PID add all three. Theres two problems that I see might occur with this, too big of a DT and the rectangular integral method gets inaccurate. Too small of a DT and your program won't crunch the numbers out fast enough.
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