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A method that
is closely related to the Dahlin controller
design is called pole-placement design. It is based on the general
feedback system,
The objective
here is to choose R(z), G(z) and F(z) such
that the closed loop has user specified pole locations. These
3 transfer functions together make up the controller, and defines
the control law which is,
Using the general
process representation
the closed loop
transfer function for this system is
All desired pole
positions are contained in the form of a pole polynomial,
T(z), and given knowledge of the process, G(z) and F(z)
are solved from
Note that in
this case, there is no time-delay compensation as can be discerned
by the presence of the time delay term in the characteristic
polynomial. Time delay compensation can however be provided
if the design problem is posed within a predictive control framework.
But that is outside the scope of this current set of notes.
Next we will
summarise what have we learnt from this set of notes on Digital
Controller Design.
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