Synchronization of a large-scale lifting system with hydraulic actuator failures is investigated in this article. The lifting system is composed of multiple intelligent lifting subsystems with hydraulic actuators, wireless data transfer unit, and distributed controller. During the lifting process, the hydraulic actuators are possible to be malfunctioned. Once actuator failure occurs, the number of lifting points and the communication topology would change over different time intervals. This article proposes a distributed synchronization control method and adopts switching technique in analyzing the lifting synchronization. The distributed controller is designed with information received from around subsystems through wireless data transfer unit rather than with direct reference signal from the control station. On the basis of Lyapunov stability theory and switched technique, sufficient conditions that guarantee the synchronization of the lifting system with actuator failures are achieved, and synchronization errors can be reduced as small as desired. Finally, the effectiveness of proposed distributed synchronization controller is verified by numerical simulations conducted on AMESim platform. From the simulation results, it can be seen that when actuator failures occur, the synchronization error of the remaining lifting subsystems is less than 5%. The lifting synchronization error shrinks to 5% in 5.87 s when a broke-down subsystem returns to normal.
Cooperative synchronization control of intelligent lifting systems with actuator failures
