Robot Romance Trilogy
The  were three Super Robot anime series created by "Saburo Yatsude" (a collective name for the staff at Toei, similar to Hajime Yatate), directed by Tadao Nagahama, and aired on TV Asahi and its affiliates from late 1976 through early 1979. 

The trilogy is known for telling complex human stories instead of merely being having a monster of the week format.

Shows
The trilogy, consisting of Chōdenji Robo Combattler V, Chōdenji Machine Voltes V, and Tōshō Daimos, was a co-production between Tohokushinsha Film, Nippon Sunrise (formerly Soeisha) and Toei Company with Nippon Sunrise providing the animation work on Toei's behalf. 

The series are notable for developing ideas from Brave Raideen.

Design
Yuki Hijiri (of Locke the Superman fame) was character designer for Voltes V and Daimos.

References

Super robot anime and manga
Bandai Namco franchises
Trilogies