Prop Flow & Press Pump mit Poppit valve Directional valve

A long time customer brought me a hydraulic system with multiple pumps with variable volume heads with proportional flow and pressure. The idea is to totem pole the pumps to deliver the requested volume/press.

Each pump has a directional poppet valve, Two pumps on 1 motor, 3 on the other. The poppets are manifolded and the A & B ports drive a single 8" cylinder with differential press sense & position feedback. The pilot is a separate discrete system. The pumps and poppets are individually controlled.

The goal is bidirectional closed loop motion control with force limiting AND minimum power draw for life cycle testing.

I am worried the individual pump response time is 100 ms zero to full stroke will get progressively worse if used in a pure serial totem fashion. The poppets run about 20 ms on/ 28 ms off.

I am thinking if I used a modified parallel flow request I will average the stroke tolerance among the pumps that share a shaft. The modification would be make 1 pump the master and gear the other and alternate the master between strokes so we get equal wear for each pump.

I’m wondering if you guys have done something like this before and could give some tips or tricks?



We haven’t done anything like this before. It sounds like a servo controller’s nightmare.
We have controlled small c-clamp presses using a servo motor and a fixed displacement pump without valves. That worked well and was easy to setup.
I would look at using a fixed displacement pump and servo motor if the positioning doesn’t need to be perfect.

It looks like you got this idea from some German source.

Thanks Peter,

Designed by Deutshe Ausschuss! Well its built already, so we will make the best we can out of it. :confused:

I’m thinking the best way to think about order of operations is in discrete blocks like [direction],[close loop stroke motion with force limit],[direction] etc, etc. Velocity and force limit will be preset prior. My theoretical fundamental frequency of the system is about 5 hz.(I am hopeful) I will post progress notes as I go along to share with others if they are interested.