Why must it be an ad-hoc network?
Have you considered making it an access point using Hostapd? Then you can connect your smartphone/tablet to it easily.
Just make sure your dongle supports AP mode. I think the 7811 does.
Plenty of tutorials around on this. I did it with an RT5370 wifi dongle.
If you must use ad-hoc mode, have a look at http://www.raspberrypi.org/phpBB3/viewt ... 29&t=39927
. Not sure what device you want to use to connect to your Pi robot, but if its a stock Android phone, it won't support ad-hoc mode, unlike a PC.