I am new to arduino. I am working on a project to make a smart driving robot. I would like to use geofencing on a small scale (15-20 sqft area) so that my robot will have a reasonable area to navigate. However I am not sure what hardware I would be looking for
is there anything I can use to create geofence on a small scale that my robot can use to locate itself?
You can put overhead light over the area, then use a few suitable photo-sensors on top of the robot to detect that light, so if it goes in the dark it takes a few steps back.
Use specific light wavelength or modulate it to avoid interferences.
It would have been helpful for you to mention in the OP that this is an indoor project. Geofencing is outdoors.
"Indoor localization" is a useful search term, and the process is much more difficult than using GPS outdoors. The best and simplest options are overhead cameras with image processing on a PC, or commercial, broadband beacon positioning networks like Pozyx: https://pozyx.io/
It is easy to say "beacons that the Arduino can ping off from" but very difficult to realize in practice.
Photodiodes and phototransistors have unlimited detection range, for a sufficiently powerful light source.
From a point light source, the intensity of the light, and the received signal at the detector, drops off as the square of the distance between them.
If you are thinking of using light sources as beacons, the most challenging problem is to distinguish the beacon from the background illumination. IR or colored LEDs as emitters and appropriate filters on the detector will help.