The Federal Reserve is trying to raise rates because they're looking for some wiggle room when the economy 'officially' slips into a recession. At that point they can try and drop the rates to get things moving again. If they keep them down near zero, then they have nowhere to go. They don't want to take the US economy into negative interest rates. It's bad enough for Japan to fall into that cycle. If the US ventures into that zone then it sends a dangerous signal to the rest of the world.
Regardless of what one thinks of the Federal Reserve and the fiat money system, Yellen's proclamations and the actions of the Federal Reserve indicate the ailing economy is becoming pronounced enough that even the pinnacle of Finance Capital is being forced to acknowledge it. The Real Economy of workers and most of the public is impacting the quasi-fantasy world of finance and its fictitious games and gambles. The relationship is complicated but the supposed 'boom' and recovery that Obama and others have tried to promote has not been based on actual economic production and genuine recovery. It's been mostly the result of speculation and finance sleight-of-hand.