Using Simulink

Purely Discrete Systems

Purely discrete systems can be simulated using any of the solvers; there is no difference in the solutions. To generate output points only at the sample hits, choose one of the discrete solvers.

Multirate Systems

Multirate systems contain blocks that are sampled at different rates. These systems can be modeled with discrete blocks or with both discrete and continuous blocks. For example, consider this simple multirate discrete model.

For this example the DTF1 Discrete Transfer Fcn block's Sample time is set to [1 0.1], which gives it an offset of 0.1. The DTF2 Discrete Transfer Fcn block's Sample time is set to 0.7, with no offset.

Starting the simulation (see Running a Simulation Programmatically) and plotting the outputs using the stairs function

• [t,x,y] = sim('multirate', 3);
  stairs(t,y)
  

produces this plot

For the DTF1 block, which has an offset of 0.1, there is no output until t = 0.1. Because the initial conditions of the transfer functions are zero, the output of DTF1, y(1), is zero before this time.

Modeling and Simulating Discrete Systems

Determining Step Size for Discrete Systems