Hierarchical coupling control of cable-driven multi-loop crane for underactuated positioning

Abstract

For the low-cost anti-swing retrofit of existing offshore heavy cranes, a (2-UPPU/UPU)UP multi-loop configuration with six cable-driven prismatic pairs and a UP underactuated pendulum is introduced. Each UPPU branch contains a fast-moving prismatic pair and a slow-moving one. A configuration tracking method utilizing three slow cable motions in 2-UPPU/UPU is proposed by motion compensation technology. A multi-loop underactuated end positioning scheme is given to achieve the cargo's horizontal positioning in inertia frame, i.e., two fast cable motions in 2-UPPU are used to drive four states comprising their tracking trajectories and two cargo swings, which frees the wave compensation and swing suppression task from crane joints and retains the original crane system. A hierarchical coupling controller with a special coupling relation matrix is designed, where the matrix-based sub-controller fusion technique provides a standardized design approach with distinct physical meaning for the application of hierarchical methodology in underactuated multi-loop systems. The stability analysis by Lyapunov method reveals multiple coupling relation matrices matching stability conditions, giving birth to five attractive coupling control modes. Simulations and experiments are conducted to compare and verify performance.