Motor control architecture including a travel, a hoist, and a controller is disclosed. The travel disposed on a main rail having an auxiliary-encoder includes a master-driver and a slave-driver for driving two motors. Each motor has a main-encoder. The hoist drives a rope and calculates a rope length continuously. The controller calculates an anti-sway position command based on the rope-length and a position command. The two drivers perform a full closed-loop computation based on a feedback of one main-encoder, a feedback of the auxiliary-encoder, and the anti-sway position command. Wherein, the master-driver controls one motor based on a speed command generated by the full closed-loop computation and the slave-driver follows the speed command and a torque command of the master-driver to drive another motor; or the two drivers compensate the torque command based on an error value between the feedback of one main-encoder and the feedback of the auxiliary-encoder.

Motor control architecture including a travel, a hoist, and a controller is disclosed. The travel disposed on a main rail having an auxiliary-encoder includes a master-driver and a slave-driver for driving two motors. Each motor has a main-encoder. The hoist drives a rope and calculates a rope length continuously. The controller calculates an anti-sway position command based on the rope-length and a position command. The two drivers perform a full closed-loop computation based on a feedback of one main-encoder, a feedback of the auxiliary-encoder, and the anti-sway position command. Wherein, the master-driver controls one motor based on a speed command generated by the full closed-loop computation and the slave-driver follows the speed command and a torque command of the master-driver to drive another motor; or the two drivers compensate the torque command based on an error value between the feedback of one main-encoder and the feedback of the auxiliary-encoder.

Provided is an offshore crane heave compensation control system and method using video rangefinding to achieve heave compensation in a directly driven pump-controlled electro-hydraulic heave compensator. The heave compensation and the heave compensator are applicable for special operation and control requirements on a fixed offshore platform and allow the crane to achieve steady lifting of a load away from or lowering of a load on to a supply vessel without being influenced by the motion of the supply vessel caused by ocean currents, ocean winds, or ocean waves. Also provided is a test platform for the offshore crane heave compensation control system using video rangefinding. The test platform provides a realistic simulation for all lifting and lowering processes of an offshore platform crane in offshore environments to study the motion control of the provided system.

Described herein are systems, methods, and structures for transferring an object between a ship and an offshore structure, comprising a hoisting mechanism arranged on the offshore structure and adapted to attach to the object, at least one range sensing device adapted to provide data relating to a detected distance from a reference point on the offshore structure to the ship, where the system is adapted to receive the data from the at least one range sensing device and to move the hoisting cable in response to the detected distance, and a motion reference unit adapted to provide data relating to a detected motion of the ship independently of the at least one range sensing device, and wherein the system is adapted to move the hoisting cable in response to the detected motion of the ship.