Safety-Critical Disturbance Rejection Control of Overhead Crane Systems: Methods and Experimental Validation

Crane systems generally operate in challenging environments (e.g., harsh weather conditions and high-altitude work), which heightens the requirements of control systems for the safety and disturbances rejection. However, underactuated nature poses difficulties in achieving the efficient positioning and swing elimination under these factors. To this end, we propose a method using a quadratic program (QP) formulation that combines an enhanced-coupling control Lyapunov function (ECCLF) with a new composite state control barrier function (CSCBF). Additionally, disturbance observers (DOBs) are employed to handle matched and unmatched disturbances effectively. The ECCLF introduces a new coupled control variable, where its tracking error ultimately exhibits an exponential convergence, elegantly overcoming the inability of full-state feedback linearization in underactuated systems. The CSCBF imposes time-varying safety constraints on the unilateral swing distance (USD), ensuring swing safety and meeting industrial payload positioning accuracy requirements. Especially, the traditional control barrier function (CBF) approach is not applicable for the proposed problem due to the infeasibility when the control coefficient of the CBF tends to zero, which is addressed by the proposed CSCBF approach. The safety of the CSCBF and the effectiveness of the controller synthesis are rigorously proven. Experimental validation demonstrates the effectiveness, safety, and disturbance rejection performance under practical working conditions.