Control of Manipulators Subject to Unknown Friction

The paper deals with a regulation control problem for a n-dof manipulator, subject to significant friction torques acting on the joints. While the values of the robot inertial parameters are assumed to be available, the friction parameters are supposed to be unknown: the compensation of the friction effects is then achieved by the proposed control approach on the basis of the estimate provided by a reduced-order observer. The effectiveness of the proposed approach is confirmed by the simulation results, obtained for a two-dof planar manipulator