OT positioning devices

[kiwi sparky]

We have used a Pepperl and Fuchs Gray code rail before on 100m + long travel.
Accuracy was +-5mm. Code reader was about $2,000NZD. Not sure on rail price
Try Custom Controls. They are the NZ agent we bought it through

 

[Lemming]

We have used a Pepperl and Fuchs Gray code rail before on 100m + long travel.
Accuracy was +-5mm. Code reader was about $2,000NZD. Not sure on rail price
Try Custom Controls. They are the NZ agent we bought it through

Not too bad value considering the cost of an absolute multi turn encoder and all the shagging around to get it rolling in a repeatable fashion... I'll chase up on Monday thanks

 

[rootboy]

I think that cwal61 has it right:

"My First Knee Jerk Reaction is To Run Away Dude. Run Fast and Run Far."

Sooner or later it will be added to this page:

http://en.wikipedia.org/wiki/Engineering_disasters

And at that point is where you will lose your license, and possibly your freedom.

 

[Lemming]

Yeah it's not the way I would go with the building design. Pretty sure the end result was exaggerated and it would be more if a long term metal fatigue thing. I am sure we would have a bucket full if disclaimers attached to any system installed..

If I end up on site, will take the hard hat signage a bit more seriously than usual thou

 

[ndzied1]

Let's look at some conflicting information in this problem:

which cost not a lot ??

Didn't read this properly first time, code rail seems an ideal option, but will have to see how much ideal costs....

They apparently pulled a million out of the building costs by adopting this methodology...

that all cranes will break the building irrespective of loading... The positions relative is the critical thing..

Did they think it would be free to keep the building from falling down? I would say if your come up with something around $500k they are well ahead!!!

 

[Lemming]

Let's look at some conflicting information in this problem:






Did they think it would be free to keep the building from falling down? I would say if your come up with something around $500k they are well ahead!!!

I'm guessing they want to keep as much of the savings as possible, but you are right its going to cost a bit... Fairly sure no thought went in to this prior, and plan A was to have the operators manage it without any controls...

 

[MichaelG]

Can we have a PLAN view and the desired Zone interlocks?


Easiest is for each Crane to have PX's reporting which zone it is in and only letting one Crane in each Zone lift
Grey Code the PX's and have redundancy to detect PX Failures.
Grey code to assist detecting alignment failures.

Another method is as the crane enters each Zone Trip/switches etc change the crane reported position. This is all assuming that there is a central controller looking after the lift permits

 

[Lemming]

Can we have a PLAN view and the desired Zone interlocks?


Easiest is for each Crane to have PX's reporting which zone it is in and only letting one Crane in each Zone lift
Grey Code the PX's and have redundancy to detect PX Failures.
Grey code to assist detecting alignment failures.

Another method is as the crane enters each Zone Trip/switches etc change the crane reported position. This is all assuming that there is a central controller looking after the lift permits

I pretty much have it sorted now, was only looking for a proven device for the long travel position.. The code rail system looks perfect... Hadn't ever come across it prior.

 

[ndzied1]

One other thing that comes to mind, although I have never used it, is the Sick/Stegmann POMUX system. Options to measure up to 1700m in length...

 

[Lemming]

One other thing that comes to mind, although I have never used it, is the Sick/Stegmann POMUX system. Options to measure up to 1700m in length...

Cheers, will look into it.. May be more robust magnetic over optical ?? Did consider making up a DYI solution with RFID reader / gantry and a bunch of tags at fixed intervals down the track.. could get 100 mm spacings / resolution.

 

[shooter]

gray code can be done with microswitches, 8 of them on each crane is enough.
another way is even cheaper, with a simple 20 turnpotmeter on each crane linked to a small gearbox so giving a analog signal (this can be with a cheap 555 to a digital input of the plc)

Still is a big prank, You will be held responsible if something breaks like the whole building, just because you will never be able to prove your system was working correct.
So please have your shoes and run.

 

[ndzied1]

One last thought / question. Is it a zone thing or just that the trolleys cannot be a certain distance from one another?

If it is strictly distance, hang bumpers with limit switches off each trolley 1/2 the minimum spacing required. If you hit a limit switch then turn off the drive motor starter for that direction. 2 bumpers per side (one over each support rail) gives you redundancy. Of course, if the required spacing between trolleys is large this could get wanky.

 

[shooter]

i have used a barcode reader to identify a modeltrain, you can use it to scan positions on a rail with same principle. rsolution of 1 meter is good enough. a scanner costs 25 euro, and the output is rs232.

i think of solution using arduino, as cheaper, and communication is easier.
http://playground.arduino.cc/ComponentLib/BarcodeScanner

 

[Lemming]

One last thought / question. Is it a zone thing or just that the trolleys cannot be a certain distance from one another?

If it is strictly distance, hang bumpers with limit switches off each trolley 1/2 the minimum spacing required. If you hit a limit switch then turn off the drive motor starter for that direction. 2 bumpers per side (one over each support rail) gives you redundancy. Of course, if the required spacing between trolleys is large this could get wanky.

Bit of both.. If 2 cranes are within the same bay, the ones either side / adjacent need to be a couple of bays away. Will end up needing to be dynamic logic...

 

[kellian]

Left field. Wifi triangulation. As in the Aeroscout system. They also have descrete position exiters. The crane position can then be tracked on a graphic display in the control room.
Issue would be interfaceing between the control system and the positioning engine.