Position control of an underactuated manipulator using joint friction

The dynamic characteristics and position control of an underactuated two-link manipulator without any additional equipment such as brake at the unactuated joint are studied. Such underactuated manipulators are difficult to control because of lack of actuators. By investigating the dynamic characteristics of the manipulator in the view of global motion, we clarify that the manipulator can be controlled if the friction acts on the unactuated joint. The two position control algorithms of the manipulator using friction are presented with numerical simulations. One algorithm controls the joints sequentially and the other controls the joints simultaneously.