Stability analysis and control law design for acrobots

This paper presents a novel control strategy based on a non-smooth Lyapunov function to guarantee the stability of the system in the whole motion space. Three control laws that are derived based on three Lyapunov functions are applied successively in three stages of motion control to achieve a suitable posture and increase the energy so as to make the acrobot move into the area around the unstable inverted equilibrium position, and to stabilize it at that position. These three Lyapunov functions are combined into one non-smooth function, which theoretically guarantees the stability of the acrobot in the whole motion space. Simulation results have demonstrated the validity of this strategy