Dynamic servo control for underactuated mechanical systems

Due to the lack of control inputs, the motion range and ap- plication areas of underactuated mechanical system are greatly limited. To overcome such difficulties, the arbitrary state point dynamic tracking problem named dynamical servo control is dis- cussed in this paper. Considering simplicity and repeatability, periodic trajectory is the best way leading to the desired point. Virtual constraints concept is employed and a target oriented trajectory planning procedure is proposed, which can generate periodic dynamic compatible and desired point crossing trajec- Tory. A Lyapunov based tracking controller is proposed to avoid the strict conditions for using a traditional LQR based method. Experiments are performed on an Acrobot prototype and veri- fy the correctness of the proposed periodic trajectory generating method and the effectiveness of the tracking controller.