Process Control: Modeling, Design, and Simulation

14.2. Zeros and Performance Limitations

Recall that RHP zeros severely limit the performance of SISO processes. For example, a model inverse can not be implemented as the controller, because this would cause the controller to be unstable. A similar problem exists for multivariable processes; RHP transmission zeros limit MIMO performance.

SISO Zeros

For a SISO process transfer function with the form

Equation 14.1

the zeros are the roots of the numerator polynomial, N(s). The inverse of the process transfer function is

Equation 14.2

That is, the ...