What is the name of the anime!?

Umm.. When I was small I used to see an anime.Ill give a description about as much i can remember!In this one.... There were robots and thier masters.Theyll be placed in a ring and would fight each other while the master would shout orders.The robots in the ring would have hitpoints on a screen.There would be other robots which would fuse and some would become weapons to be used by other robots.I uses to see thid in animax-Probably when hungry heart was coming.Can anyone please tell me what is the name of this anime please?Thank You!!!!!!!!!!!