Pew Matics - High Drawl Icks and synchronized lifting.
Pew Matics - High Drawl Icks and synchronized lifting.
(OP)
So, I'm faced with lifting an object(lid) using either air or water-based hydraulics.
Do you guys have any ideas how you'd lift this thing -evenly- with 3 to 5 gas/water cylinders? (Approximately 2" per sec.)
Are there any companies that have O.T.Shelf servo controllers for this type thing or should I gab a PLC and try to roll my own? I'm sure Gunnar will suggest an "Arduno". LOL
Do you guys have any ideas how you'd lift this thing -evenly- with 3 to 5 gas/water cylinders? (Approximately 2" per sec.)
Are there any companies that have O.T.Shelf servo controllers for this type thing or should I gab a PLC and try to roll my own? I'm sure Gunnar will suggest an "Arduno". LOL
Keith Cress
kcress - http://www.flaminsystems.com





RE: Pew Matics - High Drawl Icks and synchronized lifting.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
I could use servos but, if a slight on/off effect is tolerable, I would have a set of small valves that add 10% each to the flow and then set the slave cylinders at 90% of the master. That way, you will have 90, 100 and 110% speed on the slaves and it is then an easy (and cheap) matter to make the slaves follow the master.
To control four or five cylinders that are connected to the same load (perhaps also rigidly connected) will give you endless problems with interaction between them if you use servos. The simple master/slave configuration with compensation is much easier and safer in the long run. Cheaper also.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
I'm not sure I'm following what you mean with 'slave' and 'master' in this context. Let's say four cylinders. I'd use 4 'big' valves and 4 smaller parallel valves? I'm not seeing how I get 90% 100% and 110% with just two valves.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
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RE: Pew Matics - High Drawl Icks and synchronized lifting.
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
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Second choice, one gear pump per cylinder (they can be purchased 'ganged'), all driven by one electric motor.
Mike Halloran
Pembroke Pines, FL, USA
RE: Pew Matics - High Drawl Icks and synchronized lifting.
IR; I'm not actually sure yet whether this is a single research job or expected to be a product. But I don't see any alternative to 'rolling my own' because I'm working with an enormous pneumatics/hydraulics company and they're asking me to help them provide the controls. i.e. they don't know of anyone that does this.
I sure wish this was four stepper run screws!! Unfortunately the environment demands pure water or inert gas. I think any screws would need some sort of verboten grease.
Mike; I will look into your 'ganged gear pumps'. That sounds almost control-free.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Why not one stepper motor per pump, Mike? How would you compensate for one motor having a bit more volume per revolution than the others?
RE: Pew Matics - High Drawl Icks and synchronized lifting.
There are some smart guys in forum1083: Fluid Power engineering: some are old-school and some are knowledgable about high-performance servos. Even moderate performance servo systems turn complex and expensive pretty quickly, so unless you have a lot of money to throw at this I think I'd stick with pure hydraulic. If you want performance then Moog are probably the market leaders with a price to match, and yes, it was the same guy who made the synthesiser.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
OK. If the cylinders had the same volume on the rod and rod-less end, you could simply put them all in series. But they have not. So they will not move synchronously if you do that.
But there's a trick. (You need to think out of the box to follow this).
Connect the first cylinder as usual. Then connect outlet from cylinder A to outlet of cylinder B. The water volume trapped in rod end of A then acts on rod end on B. The result is that they both move practically the same way. Continue connecting the "wrong" way and you will have a number of cylinders that move in synch. Water doesn't compress, so it works quite well. With a gas, it wouldn't work at all.
You will have to turn half of them upside down or use a rod to transmit the movement from the downwards pointing cylinders to the lid.
You should also make sure that you can open a small by-pass when the lid is closed. Doing that will synchronize them in their home position.
Not much programming. And not many valves. Sorry.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
A hydraulic flow divider is just a bunch of gear motor/pumps coupled by one shaft. I think it's simpler to just power the shaft directly, rather than adding one big pump to drive the divider. The same motor is required.
Not known at this time, and probably significant to choosing a solution, is the allowed phasing error.
Initial phasing error can be dealt with by dump valves at the cylinders, to bleed the system just before lifting. That assumes mechanical stops top and bottom.
Differences in pump displacement and internal leakage can be dealt with by means of giant anti-roll bars. Same problem exists with flow dividers. If the bars are big enough and stiff enough, the flow dividers are not required anyway.
Also not known is the budget. Keith's involvement suggests that it's not large, and that they don't want any sort of mechanical solution, is as in flow dividers or giant torque bars.
Which leaves some sort of linear transducer and control valve per cylinder, with a microcontroller or similar watching the transducers and twiddling the control valves to keep the transducers in phase.
Mike Halloran
Pembroke Pines, FL, USA
RE: Pew Matics - High Drawl Icks and synchronized lifting.
How enormous is this thing, Keith? Is it the lid of a nuclear reactor?
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
It's not toooOOOOo big. It's a lid to a reaction chamber. It weighs many hundreds of pounds. Couple of feet across (meter). With regards to your fingers, it would be enormous, but otherwise it's not really enormous, it's the atmosphere or rather lack of allowable contaminants in the atmosphere that dictates the likelihood of water.
Speed; 2" (50mm) per second. Aiming for 1/8" (3~5mm)level maintenance during motion.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
If you do have to control the trajectory, then Gunnar's idea of series connected cylinders should work nicely. ... provided that you add enough little valves in the right places to fill and bleed them.
Mike Halloran
Pembroke Pines, FL, USA
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Does anything bad happen if it's out of level; other than sliding off whatever's holding it up?
TTFN

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RE: Pew Matics - High Drawl Icks and synchronized lifting.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
seems weird your customer is being cheap on this; most government jobs we've done had more than enough money to do it right.
sure seems 4pc moog servo valves (internal spool moved by internal ballscrew) run by stepper with nice dithering servo valve driver cards in your plc is right answer, since they don't want really proper solution (4 brushless ac servo driven electronically geared food duty (no contaminating grease) linear actuators)
www.KilroyWasHere<dot>com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Got a link to said linears? Maybe I can sway them to the right solution.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Start with 3 hydraulic cylinders that simply lift. They have no control or feedback or anything. Arranged at 120 degrees around the perimeter of the lid (I'm imagining a big round pot lid for this example)
Then add 1 hydraulic cylinder remote from the container, that is fixed to the floor and holds 3 steel cables. Each of these cables are routed along the floor and then up to the lid. They hold the lid DOWN.
Slowly advance the cylinder that holds the cables, allowing movement of the lid as the 3 cylinders lift it.
The 3 lifting cylinders are sized that they cannot lift the lid until the cables move. The cables move in unison because they are all controlled by the same cylinder. The lid lifts straight up because the lifting cylinders are always in equilibrium. They can even slant in at an angle if it will help.
I think there is work to be done sizing and selecting the cylinders, valves, cables, etc., but I don't think it will need a "brain". As for lowering the lid back down, the same 3 cylinders can "pull" it down, but you will need 3 cables from above to hold it up. Could be a separate cylinder above that lowers it down, or route the cables to the reverse stroke of the control cylinder on the floor.
Also: can the lid be centered with vertical linear guides? The guides would center it vertically on the pot, though it wouldn't help keep it horizontal, I admit.
STF
RE: Pew Matics - High Drawl Icks and synchronized lifting.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Pew Matics - High Drawl Icks and synchronized lifting.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
And Sparweb, it is exactly a large "pot lid".
Alas, I doubt they'll consider cables of any type. I'll see.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
They might be amenable to the plastic- coated wire rope that's used for boat steering. Unlubricated Delrin pulleys would be my first choice, atmosphere allowing.
For the lifting cylinders, you might be able to use gas struts, if you can find them with a long enough stroke. They typically have ball joints on both ends, so you may need to clamp the body or provide other guide means, e.g. a linear slide on one edge to provide trajectory control.
Mike Halloran
Pembroke Pines, FL, USA
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Pew Matics - High Drawl Icks and synchronized lifting.
If the stretch and sheave size requirements can be tolerated, Dyneema/Technora are synthetic rope materials to consider.
I have been told that plastic coated wire is useless for many tasks, including cases where the cable flexes under load.
I realized after posting my original idea that reversing the cable-driving cylinder is all that's required to close the lid again.
Instead of cables, you could have rods and bell-cranks. That would allow the one driving cylinder to be located "anywhere" and still apply 3 equal forces and displacements (with proper design) combined at 3 points on the rim of the lid. Bell-cranks don't allow a long displacement, though. How far does the lid have to move?
Is chain out of the picture? Even if grease-flinging bicycle chain won't do, aren't there 1001 other types of chain out there in the wide world of technology?
STF
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Spar: This is a production semiconductor machine that probably costs between 3~5 million bucks. It will operate in a low number clean room. (as in class 100 or 100 particles per cubic foot.) No deodorants, no hair sprays, and no Axe(crap). Nothing that can cause dust, fumes, stray hydrocarbon molecules, etc., etc., all are strictly verboten. Hence their request for pure water or purified specific gas operated cylinders.
The machine has lots and lots of stuff happening on it and in the room around it, above it, and under it. It has dozens of gas lines, power lines, sensor cables, and RF signals, routed to it and across it. This is probably why they don't want to complicate the area around it with overhead cables or underneath cylinders that all carve out "exclusionary spaces" around the vessel.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Lot of choices. The IE intelligent actuator models have very simple controls available too and have been around for a long time (we reped them back 25 years ago): http://www.intelligentactuator.com/robo-cylinder-c...
www.KilroyWasHere<dot>com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Pew Matics - High Drawl Icks and synchronized lifting.
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
RE: Pew Matics - High Drawl Icks and synchronized lifting.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
RE: Pew Matics - High Drawl Icks and synchronized lifting.
Link <-- Ways to synchronize hydraulic cylinders