Synchronous lifting electrohydraulic circuit

[flow720]

Hello,

I'm currently designing a set of synchronous lifting hydraulic jacks - 4pcs. I decided to go for 4 servovalves with 4 linear encoders in each cylinder, which will provide good synchronization level. The problem is, that nowhere i can find an example of how should the encoders be connected with each other, so there is a "reaction" between different cylinder pressures/loads.
What is the best way to show it on the hydraulic circuit? Should 1st encoder be connected to valves 2,3,4, etc?
Thank you in advance

 

[PNachtwey]

First, how synchronized do your cylinders need to be? You can get 1 to 4 gear flow dividers that may do the trick if you don't need precision.
If you need precision, or need to keep the lift level even with uneven loads, then you should use Temposonic or Balluff SSI rods for position feedback. You mention encoders but it is important to know hat type. Are they incremental or absolute? You should use absolute when using encoders but mounting them can be difficult. The Balluff or Temposonic rods are inserted in the back of the cylinder so they are kept dave from damage. The SSI rods should be connected to a motion controller that can synchronize the four actuators. You need to have closed loop control.

We, our customers, have done this many times before. If the hydraulic design is good, this is easy.







Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

http://forum.deltamotion.com/

 

[flow720]

Yes, I have been considering the 4-section motor flow divider, but i wanna get like max 2% synchronization error (total lift height 1,5-2m) and i think I might not get that with the divider, also the loads on particular columns may vary, highly.

About encoders, I meant exactly the ones as You mentioned - absolute, mounted in the back in every rod. So having used these, i would need to insert the motion controller, that would collect all 4 position feedbacks from columns in order to control the servovalves in the correct way, right?

Thank You so much

 

[PNachtwey]

i would need to insert the motion controller, that would collect all 4 position feedbacks from columns in order to control the servovalves in the correct way, right?

That is correct.
I have a solution for you.
RMC150E-S2

http://deltamotion.com/products/motion/rmc150/

Normally people doing private projects balk at the price but these controllers are used when companies are serious about control. Here is an example of a system that was installed in Macau. It is called the "house of dancing water". You can look it up on YouTube. The center platform is moved by 4 9mx200mm cylinders. It weighs 400tons.
This is probably over kill but the spans to the New Bay Bridge were lifted using our controller.



Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

http://forum.deltamotion.com/