non-'FRC legal' control systems?

[Otaku]

Before I get any flak for this -- no, 675 isn't planning on building our own control system.

My senior project involves motors and I'm already somewhat familiar with robot control systems, but if I can't get permission to use an old IFI FRC control system for my project, I'll need to figure out how to take the values from the two pots in a joystick and turn them into PWM signals. And as cheaply as possible.

Essentially, I need to build a system that will be light, cheap, effective and robust for use in a wheelchair I am designing and building that is based off of some of 675's previous chassis designs.

so... potentiometer value to PWM, so I can feed it into a vic or jag into a motor. Suggestions, other than FRC control systems?

I would just use the IFI Control System or the NI cRIO, but they're both quite expensive, so...