can i assign an ir obstacle sensor to s remote control war-bot. will it help me to avoid obstacles
Yes, or, I'd rather say that, it can be done, but I don't know if you are able to (you sound fairly new to this).
To make it help you avoid obstacles, you will be best off using a microcontroller to go in between the R/C receiver and the and the motors/servos, as the sensor detecting an obstacle can then force an evasive maneuver, be it turning or stopping, regardless of you trying to deliberately drive your ROV into the obstacle.
But... before trying to make something like this, get the basics down first, as you'd need to make the program and hardware yourself.