The configuration space remapped using the tangents of quarter angles. $ρT$ is the actual target that we desire, from which off-configuration target $ρT′$ is derived. A rotational spring potential energy toward $ρT′$ (Eq. (17)), illustrated by gray area, will uniquely drive from any point on the configuration space to $ρT$ along the configuration space. Note that there is no bifurcation at (0, 0) because energy increases in both modes 2+ and 2−.