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 Post subject: Measuring Tension in a ropePosted: Tue Jan 24, 2012 2:44 am

Joined: Wed Nov 16, 2011 4:09 am
Posts: 3
Hey All!
I'm working on simulating a robotic tensegrity structure in bullet, which means i'm controlling the lengths and forces in the ropes to change the shape of the structure. See image below.

I can now drive the ropes to various lengths/positions and am now trying to measure the forces being experienced by the ropes (to implement force controlled motion). I don't really want contact forces, rather I want the tension in the rope itself.

I tried looking at the force accumulators in the nodes of the rope (node.m_f) but they are always 0, so that was not helpful.
I thought to look at the impulse matrix in the anchors, but to be honest, I have no idea what to do with that data -- not really sure what it is representing.

The best idea I have so far is to look at the difference between the restlength of the rope and the actual length of the rope (i.e. calculated from node distances), use that as a measure of stretch and somehow combine that with the elasticity to calculate the tension in the rope. But, this approach seems odd, since it feels like I'm recreating information that must already exist, since the force in the rope must be calculated somewhere to generate that stretch in the first place.

does anyone have any good ideas about how to get the current tension in a rope?

thanks
vytas

hmm.. the attached image does not appear to show up. you can find it here:
http://www.sunspiral.org/vytas/random/t ... works.tiff

Attachment:
File comment: Tensegrity structure

tensegrity_simulation_works.tiff [ 86.14 KiB | Viewed 1489 times ]

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