Simulink MPC Designer ZOH FOH Error

I am trying to design an MPC controller using the simulink controller toolbox. Whenever I try to make the MPC sample time less that 1, I get the following error: "The "zoh" and "foh" methods cannot be used for discrete models with poles near z=0" Could someone please explain what the error means and how I fit my controller? Thanks

[Steven]

Did you ever fix this?

[Jordan Olson]

I'm also having this issue, but changing the sample time in the MPC doesn't fix it.

Answer 1

[dekun wang]

poles in discrete domain near z=0 means poles in continuous domain tending to -infinite which means your system's natural frequency is infinitely large. It cannot be true for any systems. So my suggestion would be to double check your plant model.