OK. I got the piston fluid flow requirements for each piston of each leg for each one of the Robot stances of one cycle of walking. Then I looked at an Army doing real walking over real terrain, and it looks like this rate is about 2.5 mph. So we want our Robot to walk along with the Army people, meaning the Robot will cycle it's stances at a rate that moves it along at 2.5 mph. Once you have flow requirements, flow pressures, and flow rate specifications, you can (FINALLY) get to what kind of a pump is needed.
I did the power requirements. Next is to show the pump, and its designed so it can create this flow rate of pressurized fluid without making any noise at all..... cool
I'll get some of this to the website soon
And, of course, again, I really suggest that you download this drawing and use Sketchup to explore it. There are details that you will never see just looking at this picture.