Swing-free control of Mobile Harbor crane with accelerometer feedback

Recently, as the amount of trade among nations has increased, a greater amount of the transport by ship is required and container ships have been enlarged to satisfy this requirement. However, there are some nations or harbors that have the problem of lack of sufficient area for the anchoring of large ships. To solve this problem, the Mobile Harbor (MH) has been proposed conceptually at KAIST. Since the MH should work on the sea, there are more problems than those of a common fixed harbor. One of the main problems is the swing of the payload, such as container boxes, as a result of the continuous sea-induced moving of the floating base. In this paper, we focus on reducing the swing of the crane due to external disturbances that are caused by the continuously moving base. We use an accelerometer to measure the swing angle of the crane and an observer is designed to estimate both the angle and the angular velocity of the swing. A sliding mode controller is also designed to stabilize the swing robustly with continuous bounded disturbance; the system simulation and experimental results are discussed.