High strain/extension mechanism actuators

[amrbekhit]

Hello all,

I was wondering what mechanisms/actuators are out there that can generate strains of higher than 1 (i.e. the actuator can extend to at least twice its original size). I can only think of two mechanism for doing so: either a telescopic system, or the use of the scissor mechanism, like this.

Any extra ones?

Thanks

--Amr

 

[jstewart]

Does it have to be purely linear? A rotary actuator with a lever arm can achieve an extension approaching 2x the initial size.

Can it be a tension-only actuator? A winch system can easily achieve very high extensions for the initial size.

What's the application?

 

[TheTick]

Look for "lifting columns".

 

[amrbekhit]

Thanks for the replies.

I would say that the actuation does have to be purely linear. I lever arm and a rotary actuator would take up a lot of space I think.

The application is a mobile robot inside a pipe, with the robot pressing its "limbs" against the pipe wall by using linear actuators. I'd like the robot to be able to accommodate a wide range of pipe diameters (70-300mm). I can see how a winch system would work, but would you not still need some mechanical structure that will be moved by the cable which needs to have a high strain?

I've had a search for these "lifting columns". They do look interesting, but they are unfortunately very large for my application.

 

[jstewart]

So here's a question: Does the robot have a length limitation? If not, rotary actuation may work very well.

For example, if the 50mm diameter "body" of the robot is in the middle, and there are relatively long "arms" (say 250mm long) in front and behind, a simple pivot joint could move each arm from a small angle (for 70mm pipe) to a larger angle (for 300mm pipe).

I'd think that this would be a very simple (and hence, robust) way to achieve the displacement, unless there's some special need for linear approach/departure from the pipe walls.

The actuator itself need not be rotary, as a linear actuator (like a pneumatic or hydraulic cylinder or leadscrew) could easily be employed to drive the arm.

 

[amrbekhit]

Unfortunately, the robot does have a length limitation - its needs to be able to turn 90 degree bends, which restricts the maximum length that the robot can take. One of my initial designs faced this problem: with the legs folded back, the robot was too long to navigate the bends.