A tax on robots?

Ken makes a decent living operating a large harvester on behalf of farmer Luke. Ken's salary generates income tax and social security payments that help finance government programmes for less fortunate members of his community. Alas, Luke is about to replace Ken with Nexus, a robot that can operate the harvester longer, more safely, in any weather and without lunch breaks, holidays or sick pay. Bill Gates thinks that, to ease the inequality and offset the social costs implied by automation's displacement effects, either Nexus should pay income tax, or Luke should pay a hefty tax for replacing Ken with a robot. And this "robot tax" should be used to finance something like a universal basic income (UBI).