Guardian robots is a mod for Fallout 4, allowing you to use different combat robots to protect your settlements. After installing the mod you should see a new tab under "Defense" in the workbrench, where you can create robots to guard your settlements. With such protection your city will not fear any raiders and super mutants.
Once you've added all the mod files into the game folder, follow the following address:
There you will find the file plugins.txt. Open it with any text editor and add to the end of the line Robot Home Defence.esm. After that, go to file properties and tick "read Only"
Download the Guardian robots mod for Fallout 4 is totally free from this page.