  This paper addresses the problem of end-effector formation control for a
mixed group of two-link manipulators moving in a horizontal plane that
comprises of fully-actuated manipulators and underactuated manipulators with
only the second joint being actuated (referred to as the passive-active (PA)
manipulators). The problem is solved by extending the distributed end-effector
formation controller for the fully-actuated manipulator to the PA manipulator
moving in a horizontal plane by using its integrability. This paper presents
stability analysis of the closed-loop systems under a given necessary
condition, and we prove that the manipulators' end-effector converge to the
desired formation shape. The proposed method is validated by simulations.
