Joint which does not constrain the motion between frame_a and frame_b. Such a joint is meaningful if the relative distance and orientation between frame_a and frame_b, and their derivatives, shall be used as states or shall be used for non-standard initialization. This joint allows to initialize every scalar element of the relative quantities, as well as to define StateSelect attributes for every scalar element separately.
In the following figure the animation of a FreeMotionScalarInit joint is shown. The light blue coordinate system is frame_a and the dark blue coordinate system is frame_b of the joint. (here: r_rel_a_1(start = 0.5), r_rel_a_2(start = 0), r_rel_a_3(start = 0.5), angle_1(start = 45o), angle_2(start = 45o), angle_3(start = 45o)).
A example to use this joint for the initialization of a planar double pendulum by providing its tip position, is shown in Examples.Elementary.DoublePendulumInitTip.