well you could mimic the current techonology in modern avionics. http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gbng/ils/
thats a pretty good explanation of what it is. Although instead of trying to do this with expensive technology you could use two IR beacons on the station, and a simple IR camera on the robot. Almost exactly like the Wii's remote control and its sensor bar..
when it finds the proper two IR beacons(or 3,4 whatever) it simply sets up a course to them and scootches on in. Now one of the problems with IR is that its suspectible to background noise.. candles, sun, some flash lights, that kinda stuff can ruin IR.. or at least give you false positives. False positives are easy enough to counter with light patterns. Set the IR led's to flash in certain patterns. Like 1, 4, 2, 3, 1, 4, 2, 3, etc etc(assuming 4 led's are used) and set the robot up to recongnize this.