Adding a spline joint to the joint collection #2784
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👋 Hi,
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The Pinocchio development team.
MegMll
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jorisv
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| SE3 operator()(const JointSpline &) const | ||
| { | ||
| PINOCCHIO_THROW_PRETTY( | ||
| std::invalid_argument, | ||
| "Graph - Joint Spline cannot have a q_ref. Please use the joint offset directly."); | ||
| } |
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Why ? It's strange but I don't get why it's not possible.
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I looked into it, and for now the spline joint can not accept q_ref. if we put a q_ref, that means we need to redefine the spline joint, from this q_ref to the end, or make the q_ref the 0 of the joint, and compute position from both side of the q_ref (-0.5/0.5, for example).
So q_ref is for now, not possible, but could be integrated when the fit_spline algorithm is added or when the upper and lower bounds are implemented
| if (!edge.forward) | ||
| PINOCCHIO_THROW_PRETTY( | ||
| std::invalid_argument, "Graph - JointSpline cannot be reversed."); |
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We have to think about that.
Right now I'm not very confident about the reversal of this joint.
I don't think creating a ctrlFrames vector with inverse transformation inside will give us the inverse transformation.
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I looked into it as well. Indeed, reversing the ctrlFrames vector will only work when degree of the spline is 1.
So maybe it's better to leave it as it is, right now.
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Is there a way that neutral and randomConfiguration return us a valid spline configuration ?
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neutral is working, because it returns 0. However if we want random, we need to redefine a lieGroup...
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Do we want to manage spline with abritrary bounds ?
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in the future, it would be nice
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Description
In this PR, we introduce the new spline joint to pinocchio. This implementation is based on the paper of Lee et al. available here
It allows to define a number of SE3 frames, that will define the movement and dynamics of the joint. It's very useful for biomechanics, but can be used in other applications.
For now the joint configuration has to be bounded between 0 and 1, otherwise the transformation computation will fail.
To do
Future