Screwjack synchronising

[tph216]

Hi,

I have a set up of a beam over a rolling drum 15m long. The beam needs to move up and down (approx 80mm), and fore-aft (+/- 50mm). The beam ends are mounted onto an end bracket with vertical guide rails allowing the vertical motion. The beam end brackets then rest on two moving end beds that provide the fore-aft motion.

My question is one regarding electronic synchronising between the two ends of the system, as they are separated by 15m, and there is no mechanical link. Is this sort of thing feasible or commonly undertaken?

I am using preloaded guide rails to guide the motions, and using the jacks only for actuation, but I imagine that the slightest misalignment between their travel at each end of the system might cause jamming or premature failure of the guide rails.

We do have positional measurements being taken of each degree of freedom at each end of the system, so we will know when / if they start to drift.

I am just wondering if it is realistic to assume that these can be kept within tolerance over a 15m length by electronic control, and whether there are any other considerations that I should be wary of also.

 

[desertfox]

Hi tph216

Firstly you are right to concern yourself with misalignment as undoubtedly will cause jamming if the misalignment gets to great.
You need to workout what angle of misalignment you can achieve before the frictional force exceeds the applied force and hence creates the jamming.
Once you have worked out your permissible misalignment I would talk to the actuator people for a solution such as
POWERJACKS

http://www.powerjacks.com/FAQ-Electric-Linear-Actuators.php#Answers

desertfox

 

[plasgears]

I used a feedback on an afterburner nozzle position sensor using an LVDT. This one was rather long, about 8 in. You can do something similar, but if the actual stroke is long, you may have to use a worm gearbox with flex drive to reduce the corresponding stroke of the LVDT. There are other ways, too.

 

[Occupant]

I have no idea about your accuracy and/or load requirements, but in my application ordinary screw jacks were just not accurate enough and I went with this here with build in encoders. Take a look - pretty expensive, though.