Searching for a robot scifi book

[tamaho]

Hi im searching for the title of a book about a robot who wakes up from a deep sleep in a space ship that is orbiting the earth.I cant remeber if he was sent on a mission to the stars or how he came to be there.Anyway he returns to Earth to find it has been destroyed and lies in ruins.He then decides to revenge his fallen masters and find out who killed all the humans on the planet.He then starts production of a robot army and with them rebuilds the planet.I think the story covers a few hundred or a few thousand years,as this robot can never die.He ends up sending out hundreds of ships out into space to find the killers of the human race.I read the book back in the late seveties or early eighties and I dont think it was that old then.I remember the paperback cover had a picture of a naked chrome robot sitting upright in a small sort of rocet orbiting the Earth.Hope someone can help,Thanks.