Slow locomotion of a three-link system along a horizontal plane

We continue to investigate the possibility of slow (quasi-static) locomotion of multi-link systems along a horizontal plane owing to changing configurations. We have shown previously that the quasi-static motion of a two-link system, occurring when the angle between its links varies, is uncontrollable and that the trajectories of the system´s vertices are uniquely defined by the initial position of the system. We consider here a symmetrical three-link system such that all its links have a common point. The control torques act between the links of the system. We show that there exist enough possibilities for quasi-static motion of the system. One can arrange the motion with the central vertex of the system moving along a prescribed line on the plane. As an example, we consider here two gaits of the three-link system allowing it to move along a straight line and to rotate on a spot.