england-and-wales
This is still assault
The exact type of assault would depend on the extent of the injury. For example, under s18 of the Offences Against Persons Act 1861 (see my added emphasis in bold):
Whosoever shall unlawfully and maliciously by any means whatsoever wound or cause any grievous bodily harm to any person, . . . with intent ... shall be guilty of felony ...
The actus reus of a s18 assault is the "wounding or grievous bodily harm". This must take place at the moment this is inflicted on each victim. It makes no difference that it was done by a robot. The only relevant consideration is whether Bob caused the assaults. Clearly, he did.
However, there is a subtlety
Criminal liability only arises where the actus reus and mens rea coincide in time. Bob may attempt to use this to his advantage and argue that he did not possess the necessary mens rea at the time of each assault. This argument will fail.
Under the “single transaction” principle, a continuing act (Fagan v MPC [1969]) or a series of acts (R v Thabo-Meli [1954]) can be treated as a whole to allow the actus reus and mens rea to coincide. Therefore, the programming of the robot and the assaults can be viewed as a "single transaction" to prevent Bob from employing this argument.