The relative displacement of the two shafts connected by WSS retractable universal couplings is caused by various factors such as manufacturing errors, installation errors, deformation of the shafts due to loading, deformation of the bases, wear of the bearings, changes in temperature (thermal expansion and contraction), and the relative movement between the components.In general, the relative displacement of the two shafts is unavoidable, but the direction of the displacement generated by the shaft system transmission under different operating conditions, that is, axial (x), radial (y), angular (a), as well as the size of the displacement is different.