Variable Resistor - Simscape

Hi everybody,

I'm trying to simulate buck converter in which the load is modeled as a variable resistor. However it doesn't work as expected. In particular I should obtain 0.5 Ohm - 5 V as mean value and 10 A.

The attached files represent the buck converter modeled and the respective waveform.

Is there anyone that can help me?

Thanks for ypur supporting