Development of Vertical Power-Assisted Crane System Considering Absolute Stability

In this paper, a vertical power-assisted crane system is proposed. The purpose of this research is to develop a crane system which reduces the operator\´s burden by power-assisted functions and facilitates the intuitive operation of a heavy object by direct manual manipulation. First, the structure of this system is described, and an analytical optimal controller is designed to stabilize the system under the model uncertainty and to optimize response. Second, "the limit-cycle problem" when an object contacts the ground is pointed out, and the condition for the attenuation of the limit-cycle is discussed. Finally, the usefulness of the proposed controller is demonstrated by an actual power-assisted crane system