Prime Day deals and promotions change every year, and the availability of specific robot vacuum brands on sale during Prime Day would depend on the deals negotiated between Amazon and the respective brands.
To find out which robot vacuum brands are on sale during the current Prime Day or any other deals available, I recommend visiting the official Amazon website or checking their Prime Day promotions page. There, you can browse through the available deals and see which robot vacuum brands are currently discounted.
Keep in mind that Prime Day is a limited-time event, and deals are subject to change, so it's best to check directly on Amazon for the most up-to-date information on Prime Day deals.