tuning formula for PT1 control path

I have a control path with PT1 behavior. However all the formulas for controller tuning (Ziegler-Nichols, Chien-Hrones-Reswick) assume the
approximation for a deadtime of the system. When setting Tu:=0 some constants become infinite with the existing rules.
Can anybody guide me to some tuning formulas that work for a PT1 path (given K and T)?
pb
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Peter Bencsik wrote:

PT1?
You left out Astrom-Hagglund tuning, which is a variant of Ziegler-Nichols that's supposed to give better damping.
--

Tim Wescott
Wescott Design Services
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Tim Wescott schrieb:

I mean a first-order-no-delay model.
In all reports and books I have found first-order-plus-delay models but no clues how to handle the case with zero delay.
pb
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Peter Bencsik wrote:

So what it Tu? That can't be right. Something is wrong.

That confused me too. I wish people would define their symbols and not assume we all use the same ones.

That is strange normally it is the other way around. You need better books.
Look at www.controlguru.com. There are FOPDT gain calculation formulas there that will work when the dead time is 0.
BTW, it is easy to derive Kc and Ti in terms of Kp, Tp and Tc using direct synthesis or pole placement. If that isn't in your books then you do need new books.
Peter Nachtwey
Almost forgot Kp = plant gain Tp = plant time constant Tc = closed loop time constant Kc = controller gain Ti = integrator time constant
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