The hyd schematic would look the same as any other valve running a double acting cylinder (assuming single cylinder variant), except that the valve would need to be an electrically operated proportional valve that the PLC controls. Will need some kind of amplifier between plc and valve too. If going that far than put a linear encoder on the ram and have the PLC watch that too and be able to set the lower limit and upper return point via touchscreen or some other means directly tot he PLC, that way it can be more precise and actually slow the cylinder speed down when getting near the desired position. Once you have it that far its basically cnc controlled, could put a control on like I did my 88 ton press brake and actual servo valves that have better control yet and viola a cnc brake. If the PLC or cnc control can monitor 2 encoders at once and control 2 valves at once than a double cylinder brake is easily doable as well.
If you get an actual cnc control like the one I did (Icon press brake controller) then you have added benefit of being able to tell it what punch and die you have in, what thickness metal and what angle you want and it calculates the bottom position for you.