Actuation model inside the DifferentialActionModelContactFwdDynamics class

[lmontaut]

Hi, I am trying to manipulate a robotic arm with crocoddyl and also taking into account contacts. I am thus using the DifferentialActionModelContactFwdDynamics class, but the actuation model that this class requires is an ActuationModelFloatingBase (C++ code below) instance, which is not correct for a robotic arm as it doesn't have a free-floating joint. Is there a way to have the DifferentialActionModelContactFwdDynamics class use instances of the ActuationModelFull class?

Thanks!

 DifferentialActionModelContactFwdDynamicsTpl(boost::shared_ptr<StateMultibody> state,
                                               boost::shared_ptr<ActuationModelFloatingBase> actuation,
                                               boost::shared_ptr<ContactModelMultiple> contacts,
                                               boost::shared_ptr<CostModelSum> costs,
                                               const Scalar& JMinvJt_damping = Scalar(0.),
                                               const bool& enable_force = false);

[proyan]

You are right @Diiso . Thanks for raising this issue. The actuation should be abstract type here, and this is indeed a bug in the design.

I can try to fix this by next week. Would that be okay for you?

[lmontaut]

Thank you @proyan, yes next week is fine ! :)

[cmastalli]

It would be also useful to include an example

[nmansard]

I think it is mostly changing the type of the actuation model inside the contact differential dynamic model. That should be an agnostic actuation, while it is hard-coded as a FF dynamics. It might be that @gfadini already solved the issue on a private branch. If this is the case, could you raise it here so that we can evaluate possibility to merge it?

Alternatively, it is mostly changing types and checking the unittest. @Diiso, do you think that you would be in position to handle it? That might be more efficient than waiting for @proyan to have the availability for it.

[gfadini]

Hi @nmansard in my case, since I was dealing with an under-actuated robot, the solution was to just remove a check in the first link being of floating base type. That way I could simply use the ActuationModelFloatingBase in place of the custom one. So all the changes were mainly on that side #816 to solve of issue #807. For some tests I also used a fully actuated robot but that was without contact, so I guess that wouldn't work for this problem.

[lmontaut]

Hi @nmansard @proyan, ok I will do the type change and create a PR. Regarding unittests, there isn't one for DifferentialActionModelContactFwdDynamics with an actuation other than ActuationModelFloatingBase so I can add one with ActuationModelFull, using the TalosArm robot.

[proyan]

Fixed with #886