Motion Compensation Device Decoupling Heave and Rotation
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Solution Overview
Problem
Existing motion compensation devices for vessels struggle to efficiently manage all six degrees of freedom of vessel movement, particularly heave, roll, and pitch, which can lead to unstable load transfer during calm weather conditions, requiring extensive waiting for still water conditions to ensure safe crane operations.
Innovation Solution
A motion compensation device comprising a z-translation unit and an xy-rotation unit, where the z-translation unit allows z-axis translational movement while preventing x-axis, y-axis, and z-axis rotational movements, and the xy-rotation unit enables x-axis and y-axis rotational movements while restraining z-axis translational and rotational movements, using separate actuators for independent control and a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a motion compensation device compensates for all six degrees of freedom of vessel movement, then the stability of load transfer is improved, but the device complexity and control difficulty increase significantly
Solution Approach 1:
The motion compensation device is segmented into two independent functional units: a z-translation unit that handles vertical motion (heave) and a xy-rotation unit that handles rotational motion (roll and pitch). This segmentation allows each unit to focus on specific degrees of freedom, reducing overall system complexity while maintaining effective load transfer stability.
Solution Approach 2:
The invention extracts and addresses only the three most critical degrees of freedom (z-axis translation, x-axis rotation, and y-axis rotation) that dominate vessel motion during load transfer operations. By taking out these specific motions from the complete six-degree-of-freedom system, the device achieves practical stability without the overwhelming complexity of compensating all possible movements.
2Stability of the object's composition
If a motion compensation device uses a single integrated system to handle all movements, then the compensation effectiveness is improved, but the device footprint and space requirements increase
Solution Approach 1:
The device is divided into spatially separated functional units: the z-translation unit positioned vertically to handle heave motion, and the xy-rotation unit positioned to handle roll and pitch motions. This segmentation allows compact arrangement of each unit independently, reducing the overall footprint compared to a single large integrated system that would need to accommodate all motion compensation functions in one structure.
Solution Approach 2:
The invention utilizes vertical dimension (z-axis) for translation motion while the xy-rotation unit handles rotational motions in the horizontal plane. This dimensional separation allows the device to achieve three-dimensional motion compensation effectiveness while maintaining a compact horizontal footprint, as the different types of motion are accommodated in different spatial dimensions.
3Stability of the object's composition
If a motion compensation device uses a single integrated control system, then the compensation performance is improved, but the control difficulty and complexity increase
Solution Approach 1:
The control system is segmented into two independent control loops: one controlling the z-translation unit for vertical motion compensation and another controlling the xy-rotation unit for rotational motion compensation. This segmentation simplifies control by allowing each unit to be controlled independently based on its specific motion characteristics, reducing the overall control complexity while maintaining effective compensation performance.
Solution Approach 2:
The invention extracts and controls only the three dominant motion modes (z-axis translation, x-axis rotation, and y-axis rotation) separately from the complete six-degree-of-freedom system. By taking out these specific motions for independent control, the device achieves practical compensation performance without the overwhelming control difficulty of managing all six degrees of freedom simultaneously.
Data Source
Figure 1
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Figure 3A
AI summary
Pedestal motion compensation device 1) for compensating heave, pitch and roll motion of a carrier frame on board of a vessel. The device comprises: a carrier frame (2); a base (3) for supporting the device on the vessel; a z-translation unit (4); and a xy-rotation unit (5). The z-translation unit allows a z-axis translational movement. The xy-rotation unit allows x-axis rotational movement as well as y-axis rotational movement. A z-axis rotational movement is prevented by a linear guide system (12), and a main universal joint (14) including a blocking element (58), so that the carrier frame and the base are moveable with respect to each other in a translational direction along the z-axis, in a rotational direction around the x-axis and in a rotational direction around the y-axis but restrained from mutual movement in a translational direction along the x-axis, in a translational direction along the y-axis and in a rotational direction around the z-axis.