I'm trying to find a cartoon that begins with an empire in Coup d'état. The king ordered the princess to escape while he held back the attackers. He sent her to a lab or something where she found a yellow robot who was assigned to protect her and they escape at the end of the episode.
The enemies have their own robot who looks like the yellow one. It is implied that both robots were created for the same purpose (protecting the princess) but he was too violent and volatile, so, even though he was superior in combat (he is running a simulation where he fights and obliterates the other robot), the yellow one is the one chosen for the task. In the next episode (or the third one; I don't remember very well) the princess and the yellow robot go to a mine to recover an artifact, which is some kind of hammer. The miners were ordered to hide there in case the robot was ever needed.
That is what I can recall of the series: It was shown in South America; only 3-5 episodes, really early in the morning. The robot was a bright yellow like Bumblebee from Transformers, but the design was more like a more rounded iron giant. It was pretty big: enough for the prince to ride his shoulder. I don't recall much of the princess besides she was in a classic princess-like long dress and had pretty long hair.
I'm pretty sure it is not Asian made. And for what I recall it was 3D, not drawn. I'm not too sure how old it is, since cartoons often take years before they make it to free TV, but the 3D was pretty good, so I don't think it is older than 10 years.