How is it going?
It is already 3 months late, but will try giving some vague hints.
First, you can find plenty of similar works by googling 'electromagnetic pendulum'. If you have signal generator you can amplify it with bridge or if heating might be a problem switching type amplifier.
Second, you must make sure you produce correct signal you amplify. It either have match resonant pendulum freaquency or detect pendulum position with sensor.
Also, starting might be problematic, since for good initial motion it requeres aligment missmatch.
Here is one of the weboage which might turn usefull
http://www.instructables.com/id/Magnetic-Pendulum/