Energy coupling output feedback control of 4-DOF underactuated cranes with saturated inputs

We propose in the present paper an energy coupling-based output feedback (OFB) control scheme for 4 degrees-of-freedom (4-DOF) overhead cranes under control input constraints. Unlike existing crane control methods, the proposed approach can achieve superior control performance using only trolley-position/payload-swing feedback with saturated control inputs. In particular, a new concept regarding virtual payloads is introduced, together with a novel energy storage function, to successfully explore the characteristics of the crane dynamics. Based on that, an energy coupling OFB control law is proposed by taking the practical input constraints into account, which achieves both precise trolley positioning and efficient payload swing elimination. The corresponding stability analysis is guaranteed by Lyapunov techniques and LaSalle's invariance theorem. Experimental results are presented to illustrate the superior control performance of the proposed scheme. (C) 2013 Elsevier Ltd. All rights reserved.