How can I include a time delay in Simulink of the type exp(-Ts) ?

I am trying to design a PID controller for a first oder plus time delay plant transfer function. I can't find a block from the Simulink library that models a time delay exp(-Ts) where T is the time delay in seconds. The only thing I could find is a discrete time delay z^-1 but surely a continuous delay should exist too ? Thank you !

Answer 1

[Gautam]

Hi Francois,

Instead of using Continuous 'Transfer fcn' block, use the 'LTI System' block present in Control System toolbox to simulate LTI systems with delays. In the LTI system variable, specify your system description. For example, if you have a LTI system with unit gain and pole at -1, the LTI system variable will be tf([1],[1 1],'ioDelay',5). Note that you can also use state space description of your system here i.e ss(A,B,C,D,'ioDelay',5) - with A,B,C,D matrices defined appropriately.

You will require the Control System Toolbox to use 'LTI System' block.

[Gautam]

Alternately, you can place a transport delay block before/after your Continuous transfer function block in series, depending on whether you are trying to include Input/Output delay in your model.