Control System Design for Cargo Transfer from Offshore Supply Vessels to Large Deck Vessels

Craft Engineering Associates

Introduction
There is a wide range of hydraulic extending-boom and knuckle-boom cranes in use on marine vessels. These cranes are often used in dynamic motion environments for cargo transfer and small boat handling. The ability to safely launch and recover small boats in elevated sea states for naval, Coast Guard and oceanographic purposes is currently a focus of investigation within these communities.

The purpose of this investigation is to extend the research begun under SBIR topic N06-
057, “Cargo Transfer from Offshore Supply Vessels to Large Deck Vessels” to improve the performance of hydraulic marine cranes in the dynamic offshore environment. In addition, the lessons learned during the development of the Integrated Rider Block Tagline System (IRBTS), the Platform Motion Compensation System (PMC) and the Pendulation Control System (PCS) for the rigid-boom, level-luffing marine cranes used for container handling on sealift ships will be incorporated into a final integrated, modular kit to improve cargo transfer with these extending-boom and knuckle-boom cranes.

Phase II Technical Objectives
The goal of Phase II is to develop and demonstrate a modular solution for crane pendulation and motion control suitable for a wide range of existing U.S. Navy ship cranes. Phase I clearly showed that pendulation control can be modularized by implementing ship motion cancellation using the crane’s existing drive system and active load damping using a retrofit damping device. In that work, a specific crane design was considered and the study was strictly proof-of-concept through simulation.

Phase II focuses on identifying the range of cranes for which the modular approach is feasible, developing the analysis and design work flow needed to design and deploy the modular solution, and demonstrating both the process and the performance on a particular crane. The incremental technical objectives of Phase II are listed below.

1. The analysis and design process for implementing modular pendulation and motion control on any crane,
2. The development of a modular crane control system (MCCS) “kit” including refinement of the key subsystems (sensors, actuation, algorithms),
3. A phased demonstration of MCCS using 1/12th and larger scale testbeds.

At the conclusion of Phase II, the objective is to have a fully functioning MCCS system demonstrating ship motion cancellation, active payload damping on an articulated crane similar to those currently deployed on numerous U.S. Navy and civilian ships. The Phase II Option will focus this development on a design that can be implemented on the hydraulic extending-boom crane, currently proposed for use on the JHSV.

Investigators: Gordon Parker