iCub finger adduction/abduction coupling handlers

[xEnVrE]

Similarly to #473, I am trying to understand the code of the coupling handlers for the finger adduction/abduction.

From physical joints space to controlled DoFs space

decouplePos should move from the physical joint space (i.e. the four joints associated to index, middle, ring and little) to the controlled DoFs space (i.e. the iCub {l, r}_hand_finger, i.e. joint no. 7).

gazebo-yarp-plugins/plugins/controlboard/src/ControlBoardDriverCoupling.cpp

Lines 427 to 432 in 8c056e2

	bool FingersAbductionCouplingHandler::decouplePos (yarp::sig::Vector& current_pos)
	{
	if (m_coupledJoints.size()!=m_couplingSize) return false;
	current_pos[m_coupledJoints[0]] = current_pos[m_coupledJoints[3]];
	return true;
	}

Then, shouldn't it be something like this? This because the range spanned by the unique DoF {l,r}_hand_finger is three times the range spanned by the link associated to the little finger (or, alternatively, that of the index or that of the little).

current_pos[m_coupledJoints[0]] = current_pos[m_coupledJoints[3]] * 3;

From controlled DoFs space to physical joints space

decoupleRefPos should move from the controlled DoFs space (i.e. the unique DoF {l,r}_hand_finger) to the physical joint space (the four joints associated to index, middle, ring and little)

gazebo-yarp-plugins/plugins/controlboard/src/ControlBoardDriverCoupling.cpp

Lines 455 to 464 in 8c056e2

	yarp::sig::Vector FingersAbductionCouplingHandler::decoupleRefPos (yarp::sig::Vector& pos_ref)
	{
	yarp::sig::Vector out = pos_ref;
	if (m_coupledJoints.size()!=m_couplingSize) {yError() << "FingersAbductionCouplingHandler: Invalid coupling vector"; return out;}
	out[m_coupledJoints[0]] = -pos_ref[m_coupledJoints[0]]/2;
	out[m_coupledJoints[1]] = 0.0;
	out[m_coupledJoints[2]] = pos_ref[m_coupledJoints[0]]/2;
	out[m_coupledJoints[3]] = pos_ref[m_coupledJoints[0]];
	return out;
	}

Then, shouldn't it be something like this? This because the best we can do is to associate one third of the range spanned by {l,r}_hand_finger to each joint (out[m_coupledJoints[1]] is set to the 0.0 as the link associated to the middle finger does not move on the real robot).

out[m_coupledJoints[0]] = -pos_ref[m_coupledJoints[0]]/3; 
out[m_coupledJoints[1]] = 0.0; 
out[m_coupledJoints[2]] = pos_ref[m_coupledJoints[0]]/3; 
out[m_coupledJoints[3]] = pos_ref[m_coupledJoints[0]]/3; 

[traversaro]

The situation is not really clear to me here. Probably as a start it would be useful to have a clear definition/agreement with names of the physical and controlled joints, see robotology/icub-models#30 . cc @kouroshD

[xEnVrE]

Can this be closed?

[traversaro]

If it works fine, ok for me!