Manual control of the two-link arm with a free joint

The problem-solving ability of a human in manual control is considered. The purpose of the manual control is the positioning of the two-link arm with a free joint. This kind of manipulator receives attention because of its simplicity. The control of the manipulator, however, is difficult because the corresponding motion is governed by a set of nonlinear equations. The experiment of manual control is done by the use of a real-time simulator. A human can find some satisfactory control methods after enough training. These results are interesting from a theoretical point of view; they suggest a possible approach to this difficult control problem theoretically