An effective heave compensation and anti-sway control approach for offshore hydraulic crane operations

Offshore hydraulic cranes are difficult to operate safely, accurately and efficiently due to their heavy structure, large inertia, non-intuitive control interface and load sway issues that result from external disturbances. This paper presents an effective heave compensation and anti-sway control approach for offshore crane operations, which is based on robotic arm kinematics and energy dissipation principles. Unlike common operator-based joint-by-joint control procedures, this automated method is more flexible, allowing for more intuitive crane operations and more accurate positioning of the hoisted load. In particular, a unique feature of this approach is that the two control functions of heave compensation and anti-sway are transparently combined and simulated in an integrated modelling environment. The system architecture integrates the control model for crane operations, the hydraulic system model for hydraulics characteristic analysis, the 3D model of the crane to be controlled, the vessel and the environment for visualisation. The propos e d control algorithm and simulation model can be extended to any type of crane model regardless of its configuration or degree of freedom (DOF) without influencing the effectiveness of the method. The hydraulic model is built by using Bond Graph elements and integrated with the control model in the 20-sim simulation environment. The crane operation can be simulated and controlled by the operator using a 3-axis joystick, which provides a transparent user interface. Related simulations were carried out to validate the efficiency and flexibility of the system architecture. As a case study, a 3-joints knuckle boom crane was implemented and tested. The simulation results prove the presented control algorithm for heave compensation and anti-sway to be a valid and efficient solution.