need some help on linearizing the plant model for an inverted pendulum in Simulink

I constructed a Simulink model for an inverted pendulum system according to this tutorial:https://ctms.engin.umich.edu/CTMS/index.php?example=InvertedPendulum&section=SimulinkModeling , and I have attached my simulink file here. I tried to linearize the plant using model linearizing in Simlunk, and specified the input force as the open-loop input, and the pendulum angle as the open-loop output. However, the step reponse of the linearized model looks like the following:

\

It seems like the angle deviation just blows up. Here are the parameters I'm using for my Simulink model:

M = 0.5;
m = 0.2;
b = 0.1;
I = 0.006;
g = 9.8;
l = 0.3;

Could someone please give me some hint?