I have a unique application and I am wondering if there is a good way of accomplishing this by programming a DMC4123 motion controller.

I have a system requiring precise zero-flow pressure control of an ultra-high purity high-pressure gas system. We would like to build a system with two servos or steppers controlling the position of two low-flow metering valves. One metering valve is controlling the inlet which opening will increase the pressure, and the other is exhaust which opening will allow the pressure to be reduced.

The system accomplishes two tasks: One is is filling and purging the system at a predefined rate (~1psi/sec) and the other is maintenance of a constant pressure due to small leaks in the system.

The primary feedback would be pressure feedback from an analog pressure transducer and then there would be secondary feedback from each servo via the encoder. its not obvious to me how I would program the Galil controller in order to accommodate this scenario. There doesn't seem to be any built-in provision for using one PID control loop to control to control two other devices in an asymmetric manner (one increases, the other decreases). I guess I could write code from scratch for an outer PID Loop for pressure control that command the positions of the two servomotors independently, is that the only way to do it?