In short i run a greenhouse and we use watering booms in them, three of them are called Grower Jr's and the company that made them is no more.... and 2 years ago no one would repair them. So i need to find a way to connect a Arduino to the regenitive drive that drives a Baldor 90v 2.4amp gear motor (cat. no. gp7406) . The way the boom works is pretty simple, it uses 2 magnets that tell it where to open the selenoids and they also tell it where to start and reverse. I really just need to know the best way to interface with the drive. Here is an album on imgur to help.
You haven't asked a question. What is wrong with it now? What troubleshooting have you done to isolate the problem? What would you like it to do different?
to connect a Arduino to the regenitive drive
To do that, you will need to know exactly how the regenerative driver works.
Do you have a detailed manual for the driver and/or a schematic diagram of the internal circuitry?
Its a fair amount of effort to work out the schematic from the board, it might be easier to try and measure the operating voltages with a multimeter from any that are still functioning, and try and characterize the signals between logic controller and the H-bridges (that's basically what a regenerative drive means!)
What control voltages are used?
What wire does what?
Is PWM used from the logic board to the H-bridges (probably).
Careful with high voltages around, always take safety seriously, even 90VDC is able to kill.
The first picture in your group is a pretty typical 90VDC speed control for 110VAC input. L1/L2 (L = Line) are for 110V AC power and A1/A2 (A = Armature) go to the motor leads.
The part that I can't answer is the connection for S0, S1, S2, S3. When there are three pins it's easy; they're the connections for a (typically) 10K potentiometer where the middle pin is the wiper. The fourth pin comes into play when the motor direction is set to reverse but how that's implemented is hard to say. You will be safe to probe those pins with a multimeter (set to DC, ~10V range) to figure out how they work; three of the pins will have voltages either ~10V or 0V and the last may be somewhere in between depending on how your controller handles acceleration of the boom.
Here's a few wiring diagrams of motor controllers used with lathes. Obviously nothing to do with a greenhouse but the principles are the same. :)