Controlling hydraulic pressure feedback for chuck etc

did some google foo here in the forum and elsewhere, I didn't find anything, so here is the question, can linux CNC control a pid to control hydraulic pressures ? IE, I might need to add or subtract clamping force from my lathe chuck, and I would like to be able to set that as either a Mcode " specify the pressure of the chuck, tailstock etc"  or ladder control just generally on a per program basis to prevent operator crushing small delicate aluminum parts and housing bores. Generally it would also be nice to be able to keep pressures to a bare minimum to reduce motor loads and conserve electricity also. this unit has a single 7.5hp constant speed AC induction motor " I think I am going to control this with a VFD in the future" , so it will only consumer the current needed to maintain pressure and flow AFAICT

My machine has 3 main circuits and all of them are adjustable for pressure. would be nice to automate this, and if I did, I am thinking steppers and pressure transducers would obviously be optimal.

Thougths and feedback ? 

If you have a pressure sensor and a controllable regulator then yes, a PID should do the job.

No need for anything clever like Ladder, just use M68 to drive the PID command pin directly.

I'd have to either swap out the regulator for a pwm regulator or put a motor on it to control it by turning the regulator adjustment knob

It's a down the road thing, bit I'd like to be able to do it

smc.collins wrote:

I'd have to either swap out the regulator for a pwm regulator or put a motor on it to control it by turning the regulator adjustment knob

Yes, to control it electronically it needs to be electronically controllable
 

I kinda think turning the knob,while being slower offers redundancy and simplicity in the pressure loop. Needs to be a lazy numb pid too.

You need feedback of the actual pressure too. (Or, possibly a homing switch on the knob)

There is probably a Modbus / EtherCAT / serial regulator out there.

Yeah, I was looking into analog 0-70 bar sensor, 0-4.5v, Not sure how I would implement a home switch on the knob though, I will have to measure the turns gain ratio and report back.

If you see any of the other options, please share links !

Actually, with a velocity-mode stepper or a DC motor you don't need to know where the knob is, as long a the motor is strong enough to turn the knob but not to break it.

I would lean heavily towards a steep0er, maybe take a tq wrench once under power and measure turning tq and calculate servo/stepper demand. I don't need it to be super fast, just good enough