What do you call large? I mean : I don't think the size of the robot is a limiting factor to use arduino or not.
What is limiting is the number of pins and special function pins. But then there are plenty of ways around that like using multiple arduino's breakput boards I2C ....
Anyway my lawn mowing robot is completely autonomous (not yet auto recharge but that is comming) is about 130 cm long and 70 cm wide.
Which is in Arduino world a "large robot"
It also has some nice features: to name some
6 motors ( 4WD + 2 grass cutting motors)
Autonomous and RC controlled driving.
Full web interface and logging
GPS
direction sensor
heat sensor on each motor
Bumper sensors
Current usage sensors
Best regards
Jantje