Tank Knight Fortress (2003)

This show revolves around the three Fortress Knights and a human boy named Jung who are about to shape the Fortress Planet, known as the home where robots live in peace. But the harmony was disrupted because of the sudden presence of a dictator Dark Fortress along with his evil schemes. Now it's up to the Fortriss Knights and Jung, who accidentally got into the Fortriss Planet, to battle the evil forces maintain peace throughout the Fortress Planet.