Many people move into RV's as their primary residence and travel across the USA in them so yes it's possible to claim an RV as your primary residence if the RV is indeed your Primary residence where you reside.
When living full time in an RV you need to have some way to get an address so you could likely use the address of an RV park you're living or better yet just buy cheap piece of land somewhere where you can park your RV at times or all the time and use that address to get your mail and setup as a permanent address to claim your RV as your primary residence.