Reference governor in control of a tower crane based on control invariant sets

The constrained control of a crane system is often based on control algorithms that utilize control invariant sets to guarantee the stability and constraint satisfaction. This paper presents a reference governor as a way of enlarging the region of attraction for such algorithms under the assumption that the crane is modeled as a series of dynamically coupled subsystems which are controlled separately. The proposed reference governor is based on the fact that dynamics of each subsystem is invariant subject to change in position. Therefore the idea is to enlarge the region of attraction by calculating the sequence of piece-wise constant reference signals. The proposed approach is verified through simulation and experimental test on the laboratory model using controllers based on control invariant sets.