Process Control: Modeling, Design, and Simulation

M4.3. Converting Continuous Models to Discrete

The Control Toolbox can also easily convert continuous models to discrete, using the c2d command.

sysd =  c2d(sysc,Ts,method)  % continuous to discrete

where sysc is the LTI object for a continuous model, sysd is the discrete object to be created, Ts is the sample time, and method is the type of hold placed on the input variable. We always assume a zero-order hold ('zoh'); this is also the default if no entry is made for method.

Consider the continuous state space model for the van de Vusse reactor, vdv_ss. It can be converted to the discrete-time model using the following MATLAB commands:

 » vdv_ssd = c2d(vdv_ss,0.1,'zoh') a = x1 x2 x1 0.78625 0 x2 0.066067 0.79947 b = u1 x1 0.62219 x2 -0.075061 ...