Adjustable robotic links
Adjustable robotic links
(OP)
Simple question guys.
Anyone come across legs or links that have an adjustable length?
For example, there exists synthesis methods for 4-bar linkages in which adjustability of a link provides several advantages.
Has anyone seen a practical version of an adjustable link? For mechanisms or robots.
Thanks and cheers!
Anyone come across legs or links that have an adjustable length?
For example, there exists synthesis methods for 4-bar linkages in which adjustability of a link provides several advantages.
Has anyone seen a practical version of an adjustable link? For mechanisms or robots.
Thanks and cheers!
![[peace] peace](https://www.tipmaster.com/images/peace.gif)
Fe





RE: Adjustable robotic links
Practical? No. They were always falling off, which is part of the reason there are now so few British motorcycles.
Mike Halloran
Pembroke Pines, FL, USA
RE: Adjustable robotic links
Is there another name for it? I can't get a decent description of one online it seems.
Fe
RE: Adjustable robotic links
I never knew about the Johnson rod, so that's a good start.
Basically, I want to know if something I can use exists or not. Otherwise I wil simply design a custom part. I may be forced to modify a linear actuator of some sort.
Fe
RE: Adjustable robotic links
Guessing you want displacement, I'd use a custom designed ballscrew setup.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Adjustable robotic links
Adjustable displacement. Basically, the robot I am working on right now needs one of its links to be adjustable in length. But not actively (as the robot is being used). It can be adjusted offline for different duties ect. It is a custom robot, but I thought I might be lucky to get some parts that might exist.
So it will have to be rigid and reliable.
Custom ballscrew setup is very feasible.
So I guess not much exists in this domain of mechanisms in practicality.
Fe
RE: Adjustable robotic links
The usual manual method I've seen is a locknutted turnbuckle with left and right hand threads, like a tie rod in a car.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Adjustable robotic links
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If it doesn't need to be power driven how about something like a camera tripod leg?
RE: Adjustable robotic links
I am leaning towards something like this in the preliminary design stage. Thanks Greg.
Mint,
Very interesting links you provided. I never knew those existed. I will look into their feasibility into my design. Thanks.
Fe
RE: Adjustable robotic links
FeX32, everything you've specified would seem to indicate that a turnbuckle or tie-rod type of device would be ideal for your application, yet you say you want something else. Why? Turnbuckles can use left-hand/right-hand threads for "coarse" adjustment, or differential thread pitches of the same handedness for very fine "micro" adjustments.
RE: Adjustable robotic links
RE: Adjustable robotic links
RE: Adjustable robotic links
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Adjustable robotic links
I was just wondering if there was some other sort of link or mechanism that could get the job done.
The tie-rod now mentioned by many of you suggests to me that this is likely the best way to go.
One of the reasons I was wondering if I could get something else is due to the large difference in link adjustability. For example, lets say I want the link to go from 500mm to 1200mm (or 100mm to 200mm). The male thread may end up protruding too far into the female part making the lesser length not practical. Maybe there is a way to work around this. I will do have some simple modeling to find out.
Interesting. I have never seen this used.
Thanks again guys for the responses!
Fe
RE: Adjustable robotic links
RE: Adjustable robotic links
RE: Adjustable robotic links
RE: Adjustable robotic links
The first is a Push Pull type screwdriver, Yankee, For light loads and somewhat limited reach.
Next is the Spieth locking bushing, etc where you can use a tube for almost unlimited adjustment. We use this arrangement for heavier loads and lengths.
The Serapid product is for very heavy loads.
Not referenced is the tube clamp nut as seen on the above mention crutches and on adjustable camera legs. This approach comes in many flavors. We use precision telescoping tubes with a lock nut similar to aforementioned products.
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RE: Adjustable robotic links
I think a trip to to the drugstore might be worth the effort.
This is the type I had in mind.
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RE: Adjustable robotic links
Thanks for those 3 first links. I think I'm going to get one of those yankee screw-drivers for my personal "screwing around"
I like the way an adjustable walking stick type mechanisms works with a locking collar. It seems stable enough for lighter applications. Easy to manufacture. The only drawback might be the precision of the adjustability. But I am sure there is a way to get around this.
Thanks for the ideas. Much appreciated!
Fe
RE: Adjustable robotic links
adding segments would be easier than nesting more than two tube together.
i've presumed these rods are compression loaded; any chance these things will be loaded in tension only ? that' d open up a whole different set of solutions.
RE: Adjustable robotic links
Aside from the walking stick approach here is osme additional
information that be of interest to you.
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RE: Adjustable robotic links
How does the robot controller 'know' the length of the arm after you've changed it?
Mike Halloran
Pembroke Pines, FL, USA
RE: Adjustable robotic links
The robot is to be potentially used for high speed applications. Thus, the loading will be tension and compression. From my modeling the closest loading condition is the "repeated-reversed" condition. Imagine something like a delta robot (not exactly, but it's the closest I could find): http://www.youtube.com/watch?v=foTE0Mau5a8
And add about 10kg to those ping pong balls.
I wish I could tell you guys more information about the robot, but I can't leak the designs for reasons I'm sure you guys understand.
I agree that this variation of a telescoping tube idea is indeed a potential solution, particularly because of the large difference in lengths I require for re-configurations.
So, I have decided to model at least 2 different solutions, one of which being this.
Then later I will conduct a feasibility study on each of the designs likely be experiment.
Thanks!
Fe
RE: Adjustable robotic links
Not a dumb question IMO, more like fundamental but important.
Initially, it will be changed manually in the control architecture. Potentially, the robot is to be re-configured for certain "blank" due to "blank" (sorry) and may be fitted with a simple sensing mechanism (maybe something like Hall sensors) to provide a signal of link length.
Fe
RE: Adjustable robotic links
RE: Adjustable robotic links
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RE: Adjustable robotic links
Fe