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Offline anandxxTopic starter

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extreme engineering
« on: November 30, 2013, 11:27:44 PM »
dear all,
Had futile attempts at finding a practical solution to manage the following.

Goal : Similar to a crane that can move on 3 controlled axis.

The requiremet is to move an object across 17 meters and 3 meters wide and 2 meters high area

The info fed to the mechanism is x,y,z axis data.

The challenge is to move it across 17m at upto 40m/s variable based on input data.

How can this be achieved?







Offline hobbes

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Re: extreme engineering
« Reply #1 on: December 01, 2013, 03:25:16 AM »
To get to 40m/s from zero and slow down to zero again before you get to 17meters you will need 9g acceleration. Perhaps you could use pneumatics to get that kind of power on your crane. Another extreme option is a collision to get your object to where it needs to be, kind of like when you play billiards. you would need to calculate where the object needs to go and punch it there.

Offline bdeuell

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Re: extreme engineering
« Reply #2 on: December 01, 2013, 12:18:00 PM »
Perhaps a delta robot or a system of cables and winches.

I think keeping the moving parts as light as possible will be your best bet.

There is no mention of what loads you need to handle

Offline jwatte

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Re: extreme engineering
« Reply #3 on: December 02, 2013, 12:03:08 PM »
A typical X/Y gantry could be built to perform like you want, although it has to be ridiculously specified for the kinds of speeds you're talking about.

How heavy is the object? Moving a half-pound object is different from moving a half-ton object is different from moving full-weight cargo containers.

Offline anandxxTopic starter

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Re: extreme engineering
« Reply #4 on: December 02, 2013, 10:57:21 PM »
Thankyou for your responses.

The object is only 400 GMS in weight. its basically a ball that needs to follow a predetermined trajectory
and is not propelled like a canon but moved with arm support in x,y,z axis.

Offline jwatte

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Re: extreme engineering
« Reply #5 on: December 03, 2013, 12:02:05 PM »
One problem you're going to face is that the system itself (17 meters long) will be heavier than the object you move. Thus, you have to specify the system for the weight/inertia of the gantry, rather than the object itself.

How much precision do you need? Decimeters? Centimeters? Millimeters? Microns?

Offline anandxxTopic starter

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Re: extreme engineering
« Reply #6 on: December 05, 2013, 08:56:26 AM »
about 1 cm accuracy will be great.

There will be on a mobile platform going across 17m carrying a motor/other drives for Z axis

Offline jwatte

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Re: extreme engineering
« Reply #7 on: December 05, 2013, 11:29:12 AM »
Sounds like you need an XY gantry and a Z pulley. I'm assuming it's OK to enclose the are with the gantry supports.
We're probably talking chains or heavy timing belts; kilowatts of electric motor power. Maybe linear drives instead, although that might cost a lot and be hard to get in sufficient speeds.
What's your budget?

Offline anandxxTopic starter

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Re: extreme engineering
« Reply #8 on: December 08, 2013, 06:49:48 AM »
budget is not a criteria,

The challenge i face is sizing the motor for such speeds and deceleration.

Yes The initial thought was an XY platform and a hoist. See attached image.

Not sure if this is practically feasible for such speeds.









Offline jwatte

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Re: extreme engineering
« Reply #9 on: December 08, 2013, 09:09:30 PM »
I, too, don't exactly know whether it will be "feasible" although it is not yet proven "impossible" -- sufficient money can solve many problems :-)

These direct drive linear motors claim "easily above 10 g acceleration," although I don't know how much weight they carry at that point:
http://www.kollmorgen.com/en-us/products/motors/direct-drive/direct-drive-linear/ic-series-ironcore/
With the rated 6900 N sustained force, I think you can get about 70 kg moving at 10g.

The hoist seems like a problem, though, because it will move like a pendulum when the gantry is moving. Maybe some advanced math will let you tune the deceleration of the gantry to the length of the pendulum and make it end up in the place you want it with zero movement. Maybe.



Offline hobbes

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Re: extreme engineering
« Reply #10 on: December 10, 2013, 02:28:16 AM »
Here is an idea: Instead of having one arm, use a two dimensional array of arms suspended from the ceiling. You could use pneumatic tubes to push the arms down. The arms could be spaced close together and can be lowered very quickly ( gravity assisted ). When a target and destination is selected have the arms that are in line with the path come down. The first arm will grab the target and pass it to the next arm, until it gets to the final arm. Once the first arm grabs the target object each arm can have a predetermined motion to pass the object to its neighbour very quickly.

If you want to get fancy you could even lower a container for you target object. The first arm would encase the object in the container and than it could use a magnetic force between the arms to slide the container to its destination. In effect each arm would act as a magnetic rail tile.

 


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