wholeBodyDynamics: Add a wrench summer to express/publish wrenches acting on different frames in a single frame

[prashanthr05]

@GiulioRomualdi wrote,

I'm currently changing the walking to take into account multiple wrenches acting on the foot.

Here I noticed that the for icub3 the wrenches are computed w.r.t to different poles (l_foot_front and l_foot_rear)

whole-body-estimators/devices/wholeBodyDynamics/app/wholebodydynamics-icub-external-eight-fts-sim.xml

Lines 30 to 33 in e5cab1a

	<param name="/wholeBodyDynamics/left_foot_front/cartesianEndEffectorWrench:o">(l_foot_front,l_foot_front,l_foot_front)</param>
	<param name="/wholeBodyDynamics/left_foot_rear/cartesianEndEffectorWrench:o">(l_foot_rear,l_foot_rear,l_foot_rear)</param>
	<param name="/wholeBodyDynamics/right_foot_front/cartesianEndEffectorWrench:o">(r_foot_front,r_foot_front,r_foot_front)</param>
	<param name="/wholeBodyDynamics/right_foot_rear/cartesianEndEffectorWrench:o">(r_foot_rear,r_foot_rear,r_foot_rear)</param>

Consequentially combining wrenches become more "complex" in the walking side. Indeed in the walking i'm assuming that the wrenches are expressed in the _sole frames. So in order to combine them I should add some new parameters in the configuration files. Do you think it's possible to express tehe frames directly in the _sole frames?

A feature in WBD to sum the wrenches acting on different frames to be expressed in a single frame would indeed be useful.

cc @traversaro @HosameldinMohamed