Bob Rice
Member
I am working with a customer tune a couple of PID controllers on their DeltaV system. And we started talking about all the different PID Forms out there (don't get me started on that one). So, we got a little curious about the DeltaV forms. There are two forms listed in the DeltaV documentation, the Standard PID and the Series PID.. Here is a screen capture of the forms (see below, also attached if imageshack expires).
The standard PID form looks OK, but the series form seems to be a little screwy (that is the technical term I use). The series form seems to have an extra term that doesn't appear in any series form of the PID equation I have ever encountered.
If you look at the series form as written,
Out(s) = Gain *(1+Tds/(a*Tds+1))*((Trs+1)/(Trs))*E(s)+ F(s)
the (1+Tds/...) should be written as (Tds/a..) without the 1+. I figured the brilliant minds of this board would be able to tell if I am an idiot, or if it just a small error in the documentation.
I haven't brought it to the attention to Emerson/DeltaV people yet. Figured I wanted some proof first.
Btw: I have been reading this forum for the past two months, and have learned more about PLC systems then in my 10 years of college (which including using PLCs to build experiments).
Regards,
Bob
The standard PID form looks OK, but the series form seems to be a little screwy (that is the technical term I use). The series form seems to have an extra term that doesn't appear in any series form of the PID equation I have ever encountered.
If you look at the series form as written,
Out(s) = Gain *(1+Tds/(a*Tds+1))*((Trs+1)/(Trs))*E(s)+ F(s)
the (1+Tds/...) should be written as (Tds/a..) without the 1+. I figured the brilliant minds of this board would be able to tell if I am an idiot, or if it just a small error in the documentation.
I haven't brought it to the attention to Emerson/DeltaV people yet. Figured I wanted some proof first.
Btw: I have been reading this forum for the past two months, and have learned more about PLC systems then in my 10 years of college (which including using PLCs to build experiments).
Regards,
Bob