Building an anthropomorphic robot

[Ataraxy]

Hi,

I faced a problem when trying to build an anthropomorphic robot on V-Rep. Basically to do so I follow the inverse kinematics tutorial's steps except I imported each part of the robot from a different STL file in order to avoid the dividing process. The problem occured when I tried to close the kinematic chain here :



As I already have each part of the kinematic chain attached (links parent-child), trying to join both parts here results in a break of the configuration. I don't know if there is a way to force this arm to be linked at both extremities or if I may have to proceed using the dividing process as described in the IK tutorial.

Thank you by advance :)

[coppelia]

Hello,

you have a loop in your mechanism. So you should first build a tree-like hierarchy for your robot, closing loops as close to the base as possible. In your example, instead of having a branching near the base, do the loop closing at that location, and have the branching where the loop is currently open.

To close the loop, use a tip-target link for an IK element:

Code: Select all

link1 --> joint1 --> link2 --> joint2 --> link3 --> joint3 --> link4 --> joint4 --> ... (rest of your robot chain)
                                                                     --> joint4b --> backLink --> tipDummy1
                           --> targetDummy1                  

Have tipDummy1 and targetDummy1 linked via a link type IK, tip-target. The IK element that relates to it should be solved in the same IK group as the rest of the mechanism. But you should indicate the base object for that IK element as link2. Be careful also when defining the constraints for the IK element (should only have 2 positional constraints activated, depending on the orientation of your base object for that IK element).

Cheers