Support for spring elements

[touste]

Are spring connections supported? If not, that would be a nice addition. Their action would simply result in a force proportional to the relative displacement of two points. Thanks!

[tkoolen]

Yep, that'd be a nice addition. It's not that hard to implement currently, through the use of the external_wrenches argument of dynamics! in combination with the Wrench constructor that takes an application point and a force, though simulate currently doesn't expose the external_wrenches API to the controller. But it would be nice to just have a LinearSpring type or something like that.

Right now I'm almost exclusively focused on my thesis and thesis defense (until September 30 or so). After that I plan to give this package some more love for a bit.

[touste]

Good to know this is of interest! All the best for your thesis defense!

[touste]

Hi, I hope your PhD defense went smoothly! I'd like to try implementing the spring connectors in this package, however I find it difficult to understand the way I should do that. I'm more used to working with solid mechanics and not really familiar with rigid body dynamics, could you point me to how I could implement this? I expect a link type for which are given forces and positions as input, and it should output new positions and perhaps derivatives, but I cannot find it as such. Thanks!

[JurajLieskovsky]

Hi, late to the party here. I am implementing compliant joints for a project and as a proof of concept I defined a "spring" joint type which is practically a prismatic joint with added parameters free_length and stiffness. The main difference is that inside dynamics! it produces a state dependent joint torque that is added to torque provided as an argument.