Large Vessel Interface Lift-On/Lift-Off Crane

What Is It?


The Large Vessel Interface Lift-on/Lift-off (LVI Lo/Lo) Crane is an advanced motion-compensated at-sea cargo transfer system that will be able to transfer fully loaded cargo containers between ships at sea in Sea State 4 and below by providing six degrees-of-freedom control of the payload without taglines.

How Does It Work?


The system enables the rapid and safe at-sea transfer of standard ISO containers and other heavy loads from military and commercially available ships onto the Sea Base. Capability details include:

  • Ability to maintain optimal cargo throughput rates through Sea State 4
  • Ability to transfer cargo between two ships directly alongside each other at zero forward speed or underway at slow speed in the open ocean
  • Motion sensing and compensation for the ships and/or the cranes will allow safe and efficient transfer of cargobility to transfer cargo

What Will It Accomplish?


The LVI Lo/Lo crane is a key technology for enabling the flow of joint logistics through the Sea Base. Currently, to off-load a container ship, it must have a safe deep-water port. By adding the LVI Lo/Lo crane to the Sea Base, the container ship can be off-loaded at sea, with the containers transferred to other modes of transportation for the final leg to the shore. This eliminates the need for a secure deep-water port and enables the flow of containerized logistics through the Sea Base to the shore.

The LVI Lo/Lo crane system and the supporting technologies being developed under this program combine to provide an advanced cargo at-sea transfer capability that will allow vastly improved cargo throughput within the Sea Base. The LVI Lo/Lo crane capability is being developed as a "system-of-systems" and provides advanced technologies that surpass existing technologies currently being used in the modern marine and material handling industries.

The system is comprised of a crane architecture supported by a sensor suite to detect crane, payload and ship positions/motions, and a control system to automate motion compensation and optimize operator demands. The crane architecture has two main subsystems. The “macro crane” consists of an eccentric arm that attaches to the ship and has the main crane housing at the end of the arm. A boom extends outward from this crane housing. The gross relative motions are removed by controlling the movements of the eccentric arm and the boom. The “micro crane” is an eight-wire “inverted stewart platform” hanging from a wrist at the end of the boom. Each pair of wires is attached to one corner of a spreader bar that has twist-locks to attach to the top of a standard 20-foot ISO shipping container. The micro crane removes the remainder of the relative motion and matches the motion of the spreader bar to the top of the container and locks the container to the spreader bar for transfer.

When the container is attached to the spreader bar, it can be controlled in all six degrees of freedom and does not pendulate due to the natural anti-pendulation properties of the inverted stewart platform combined with the system’s active motion control. At a minimum, when the LVI Lo/Lo crane system is delivered, it will contain these subsystems: an advanced crane system (electromechanical actuators, machinery control software, energy storage, machinery sensors); and wave/ship motion sensing and control. When delivered, the LVI Lo/Lo crane will give the warfighter the ability to move containerized logistics through the Sea Base without having a secure deep water port for off-loading container ships. This greatly increases the throughput of the Sea Base and provides a key part of the logistics enabler for the initial flow and ongoing support of a Joint Task Force to the shore through the Sea Base.

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