Stabilization for a class of underactuated mechanical systems

We study the control problem for a special class of underactuated mechanical systems addressed as nontriangular form underactuated mechanical systems. Specific changes of coordinates are introduced to define this class, which includes many important models of mechanical systems examples. The main result of the paper is the construction of a nonlinear feedback controller for a class of underactuated mechanical systems for which the loop equilibrium at the origin is made semiglobally stable. Our study is based on the control of a whirling 2 DOF underactuated pendulum.