The way robots sound is usually more in the voice rather than what they say. I agree with Robert Jordan about minor mistakes if your robot is supposed to learn. However, in a lot of popular movies with advanced robots the robots have perfect English they just don't use contractions (I'm, He's, can't, etc). Because contractions came about as a lazier way to say something robots don't tend to use them because it would make them "too human" plus not using contractions generally adds to clarity. Good luck on your script!