Vessel Motion Compensation Device for Crane Load Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motion compensation devices for cranes on vessels fail to effectively manage all six degrees of freedom of vessel movement, leading to relative motion between the crane and the vessel during load transfer, causing unsafe dynamic and snatch loads, especially when picking up or placing loads on the vessel.
Innovation Solution
A motion compensation device with a carrier frame, actuator system, sensor system, and control system that compensates for x-axis rotational, y-axis rotational, and z-axis translational movements of the vessel, allowing for precise control of the crane's position relative to the vessel, including an outboard control mode for load manipulation and an on-board control mode for maintaining the crane's stability during load transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the carrier frame is maintained motionless with respect to the fixed world to compensate for vessel movement, then the crane position stability with respect to external targets is improved, but relative motion between the crane and the vessel occurs during load transfer operations
Solution Approach 1:
The system dynamically switches between two control modes: world-fixed mode for external target operations and vessel-following mode for onboard load transfer. This dynamic adaptation allows the system to optimize performance for different operational contexts, resolving the contradiction between stability and ease of operation.
Solution Approach 2:
The control system changes the reference frame parameter based on operational needs. In world-fixed mode, the carrier frame reference is the fixed world coordinate system. In vessel-following mode, the reference shifts to the moving vessel coordinate system. This parameter change enables the system to eliminate relative motion during load transfer while maintaining position stability during external operations.
2Manufacturing precision
If motion compensation is applied to maintain crane stability relative to the fixed world, then positioning accuracy for external targets is improved, but dynamic and snatch loads occur during vessel-based load transfer
Solution Approach 1:
The system dynamically adjusts its control strategy based on the operational context. For external target operations, world-fixed compensation provides high positioning accuracy. For onboard load transfer, the system switches to vessel-following mode, dynamically adapting to vessel motion to prevent dangerous dynamic and snatch loads, thus ensuring operational reliability.
Solution Approach 2:
The reference frame parameter is changed from world-fixed to vessel-following coordinate system during load transfer operations. This parameter change aligns the carrier frame motion with vessel motion, eliminating relative acceleration and preventing unsafe dynamic and snatch loads while maintaining positioning accuracy relative to the vessel.
3Stability of the object's composition
If all six degrees of freedom of vessel movement are compensated, then complete motion stabilization is achieved, but device complexity increases significantly
Solution Approach 1:
Instead of uniformly compensating all six degrees of freedom in all operational modes, the system applies compensation selectively based on local operational requirements. In vessel-following mode, only three degrees of freedom (x-axis rotation, y-axis rotation, z-axis translation) are compensated to match vessel motion. This localized approach to compensation reduces system complexity while maintaining adequate stabilization for the specific operational context.
Data Source
AI summary
The invention concerns a method for transferring a load between a target position on board a vessel (40) and an outboard position outboard said vessel. The invention further concerns a motion compensation device (1) applying the method. In the method the load is being transferred by a crane (30) carried by a motion compensation device arranged on board the vessel. The motion compensation device comprises a carrier frame (2), a base (3) and an actuator system (8, 9) for moving the carrier frame with respect to the base; the base being fixed to the vessel and the crane being carried by the carrier frame. During picking up a load from the vessel or placing a load on the vessel, the actuator system is being driven in an on board mode such that the carrier frame is being compensated for x-axis rotational movement and y-axis rotational movement of the vessel, and follows, viewed in the vertical direction, the vertical movement of the target location. During picking up a load from the outboard position or placing a load on the outboard position, the actuator system is being driven in an outboard mode such that the carrier frame is being compensated for x-axis rotational movement, y-axis rotational movement and z-axis translational movement of the vessel.