Sorry, in this case it seems that words say more than a thousand pictures. So:
1. All cylinders receive the same pressure. But you choke the separate cylinders differently. The Master shall get 10% more flow (less choked) than the Slaves.
2. There are two small extra valves for each Slave and these valves open for one 10% flow each.
3. For each Slave, there is a simple mechanism that checks to see how the Slave is doing w/ regard to the Master. This could be a sophisticated linear transducer (Tempsonic, Balluff etc) or a photocell or a mechanical contraption that actuates two switches.
4. Start with one +10% valve activated. All cylinders will then receive 100% flow and should move synchronously. But we know that they won't.
5. Now, one cylinder moves faster than the Master. The secret sensor (see item 3) then switches the corresponding +10% valve off so that cylinder moves at a reduced speed until it is level again.
6. If one cylinder moves too slowly, same thing but different takes the cylinder home level (activates the other +10% valve, I didn't have to write that - agree?).
7. Don't forget to stop at end-of-travel (didn't have to write that either, but wanted to).
There are a few things to think about. First, is the somewhat jerky movement accepted - think about the violent oscillating movement that could be the alternative! Second, the contraption and the secret sensor may not have been invented yet. The 10% can probably be reduced to 5% or less. That will make the already small jerkiness even smaller.
Good luck! I think that I would like to build one myself. Sounds like an interesting thing to do. But, if I could have it my way, I would use ball screws and synchronized stepper motors. Much simpler and everything COTS.
Gunnar Englund
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Half full - Half empty? I don't mind. It's what in it that counts.
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