Creating and Manipulating Models

Continuous/Discrete Conversions of LTI Models

The function c2d discretizes continuous-time TF, SS, or ZPK models. Conversely, d2c converts discrete-time TF, SS, or ZPK models to continuous time. Several discretization/interpolation methods are supported, including zero-order hold (ZOH), first-order hold (FOH), Tustin approximation with or without frequency prewarping, and matched poles and zeros.

The syntax

• sysd = c2d(sysc,Ts);     % Ts = sampling period in seconds
  sysc = d2c(sysd);
  

performs ZOH conversions by default. To use alternative conversion schemes, specify the desired method as an extra string input:

• sysd = c2d(sysc,Ts,'foh');% use first-order hold
  sysc = d2c(sysd,'tustin');% use Tustin approximation
  

The conversion methods and their limitations are discussed next.

Feedback and Other Interconnection Functions

Zero-Order Hold