OBoom: low cost deployable linear actuator

A resilient strip (of tape measure fame) triad fed through centrally driven rollers extends a structure constrained by self spacing ribs

Description

This project was originally conceived as part of research into alternative linear actuator designs for use with ultra high vacuum (UHV) equipment. The deployable booms and antenna designs seen in early satellites and probes, such as Voyager, were inspirations. The design requirements likewise sought were long travel range (> 1 m), lightweight (easily hand carried), and compact (fit without facility modification).

The first functional prototype of the mechanism was compelling but the budget for the UHV application was intolerant to further development. But I think an affordable version has potential in many more common applications and offers unique features not readily available elsewhere.

Applications would be anywhere that long travel range, lightweight, and compactness are paramount. While relatively modest load ratings, would be best in tension and can deliver added functionality to anywhere suspended cables have been conceived. Excels at cantilevered reach.

CC BY-SA

Details

Three of the linear actuators mounted to a ceiling with universal joints can come together at a common spherical joint suspending an actuating claw. Small items dropped can be aided in their retrieval. Trusting pets can be engaged remotely.

Files

deploy_boom_v3.stl

STL of all the 3d printed parts needed to produce the functional demo. CC BY-SA

Standard Tesselated Geometry - 35.61 MB - 09/27/2021 at 06:33

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Components

12 × M3 X 10 mm button head hex screw

6 × M3 X 20 mm button head hex screw

14 × M3 nut

3 × 5 mm OD X 30 mm dowel rod

1 × Nema 17 stepper

Discussions

Simon Merrett wrote 10/03/2021 at 20:39

Hi, really glad to see this. I had a play with these tape measures for a linear actuator too. I was using velcro/hook and loop to keep them together, as the roller action at the base was good at separating velcro and it was good in the straight sections at keeping the metal strips fairly rigid.

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James Newton wrote 09/29/2021 at 04:15

Very interesting idea... Is there a video of it moving? How much load can it lift?

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K.O. wrote 09/30/2021 at 18:31

Bi-directional force, last I measured it, is ~1.6 kg (as shown in test stand) with limit imposed by slipping friction drive (my guess is about 10% efficient, co-botingly soft). There is plenty of design overhead to push coupling efficiency. Speed is currently limited by stepper/driver (~500 rpm -> ~22 mm/s linear travel) chosen for ease of mounting and to assess slip. My design goals going forward will orient towards arbitrary motor input/mounting, parametric tape selection and associated spool management all while maintaining that low cost heading.

Will add video after DC motor integration to compel with speeeeeed!

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James Newton wrote 09/30/2021 at 18:45

That's surprisingly good. Cool!

If you are going to DC... are you including a position sensor? I did some interesting work with a "string" sensor where I used a string wrapped around a shaft with an AMS non-contact magnetic sensor facing. I could get sub micron measurement with the 4K CPR version. It strikes me that you could add one of those to one of the rollers.

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K.O. wrote 09/30/2021 at 19:09

My DC motor tests will be to look at wear and speed limits so I am not yet set on closing a position loop. Perhaps others (you? hint hint?) might have more to add on this front than I!

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OBoom: low cost deployable linear actuator

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Description

Details

Files

deploy_boom_v3.stl

Components

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