BMT Designers & Planners Inc, a subsidiary of BMT Ltd, has been awarded a three-year contract by the Naval Surface Warfare Center (NSWC), Caderock Division to develop its existing Pendulation Control System (PCS). This advanced control technique, developed under contract to NSWC Carderock Division, enables cargo transfer in a seaway. The US Navy’s Sea Basing Program and, more specifically, the Maritime Prepositioning Force (MPF) Program has been a leading sponsor in the development of technology applications to this problem.

BMT will be responsible for developing customisation to the PCS technology, including control algorithm. Software and hardware will be advanced to satisfy the specific requirements of crane lift on/lift-off (LO/LO) operations aboard ships using the MacGregor-designed Hagglunds pedestal crane. Further enhancements to the winch machinery and human-machine interfaces will be developed to improve LO/LO operations while underway in a seaway.

There has been growing interest in recent years in the ability to conduct cargo transfer operations between vessels in higher sea states. The design of the cargo transfer system, whether it employs cranes, ramps, or other methodologies, requires accurate knowledge of the absolute and relative motions, velocities and accelerations of the vessels involved in the transfer.

To predict accurately the wave-induced motions of multiple interacting vessels during such cargo transfer operations and to incorporate correctly non-linear effects of mooring lines and fenders, it is essential to carry out computations in the time domain. The present work focuses on modifying the algorithms and software to accommodate forward speed effects. This involves accounting for the speed dependency of the wave-induced forces, as well as including steady flow effects such as lift and drag (manoeuvring forces) and inter-vessel ‘Bernoulli forces’.

Joseph Salsich, President of BMT Designers & Planners, comments: “BMT has the industry’s leading knowledge and expertise within this field. The award of the three-year contract means that BMT can continue its pioneering work in this realm and further enhance existing solutions to the safe and efficient transfer of cargo through seaways.”