how to change the length of a cable automatically

[aicha]

Hello!
i'm new in vrep and i'm going to realize a 'simulation of a parallel robot with large cables' here's an example
https://www.youtube.com/watch?v=52pOPf_lVDU
to move the platform i shell change the length of each cable every instant but how to do it that's the problem i tried to do it with matlab+vrep but it's a little bit complicated so i decided to do it only with vrep
please if you have an idea that can help me don't hesitate
i'll be waiting for your suggestion ,thanks

[fferri]

I think you can model each cable with a prismatic joint, and use it like an ordinary joint (e.g. via its motor or its controller).

Prismatic joints: prismatic joints have one DoF and are used to describe translational movements between objects. Their configuration is defined by one value that represents the amount of translation along their first reference frame's z-axis. They can be used as passive joints, or as active joints (motors).

On each end of the prismatic joint you would have a spherical joint to allow rotation in any axis.

http://www.coppeliarobotics.com/helpFil ... iption.htm

[coppelia]

Have also a look at this topic, since you will also need loop closure dummy-dummy connections. I would do:

6 individual branches, like:

Code: Select all

staticFloor --> sphericalJoint --> auxMass --> prismaticJoint --> auxMass --> sphericalJoint --> dummy1a 
            --> sphericalJoint --> auxMass --> prismaticJoint --> auxMass --> sphericalJoint --> dummy2a 
            --> sphericalJoint --> auxMass --> prismaticJoint --> auxMass --> sphericalJoint --> dummy3a 
            --> sphericalJoint --> auxMass --> prismaticJoint --> auxMass --> sphericalJoint --> dummy4a 
            --> sphericalJoint --> auxMass --> prismaticJoint --> auxMass --> sphericalJoint --> dummy5a 
            --> sphericalJoint --> auxMass --> prismaticJoint --> auxMass --> sphericalJoint --> dummy6a 

MobileBox --> dummy1b
          --> dummy2b
          --> dummy3b
          --> dummy4b
          --> dummy5b
          --> dummy6b

Where you have 6 dummy-dummy pairs (i.e. dummy1a-dummy1b, dummy2a-dummy2b, etc.)

You will have to very carefully set the mass and inertia of the cable elements, and use the Vortex engine.

Cheers

[aicha]

thank u that really helped me