Teens in the Universe (1975)

Interstellar expedition manned by "pioneers" (Soviet Scouts) reach Alpha Kassiopea to find that smart robots have taken control of the whole planet. Their only goal: to make their masters happy, as they understand it. Happiness is, to them, satisfaction of primitive needs, and removal of "disturbing" emotions such as love and responsibility. Many years ago they reached this goal and thus wiped out the original inhabitants. A few people escaped from "total happiness", and their descendants orbited the planet in a big space station for many generations. Brave Soviet pioneers land on the planet, destroy the robots and return the planet to the descendants.