I have a machine/robot that has a manual joystick to control forward and reverse. The joystick is connected to a mechanical linkage system that goes forward/backward, which than controls a hydraulic pump. I want to be able to "hack" the joystick to control the forward/backward motion through software. I have a few design criteria that I am trying to work around, hoping to get some input/help:
1) I need a failsafe. If I cut the power while the machine is moving and then turn it back on, I would like the machine to start in neutral, not where (forward/backward) it last was.
2) Its not a binary forward/backward so some voltage control would be nice to make it smoother.
3) Able to control manually and through software. I would like to send X voltage to it through software (arduino + hardware) but not lose functionality if someone wants to take physical control.
Any advice on what kind of set up I would need to do this?