Heave Compensator Lift Control for Environmental Force Management
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Solution Overview
Problem
Existing lift compensation methods struggle to manage environmental forces during hoisting operations, particularly for large items, leading to potential overloading of lifting equipment and uncertainty in additional forces from waves and wind, making it difficult to maintain control and stability.
Innovation Solution
A method for lift compensation that introduces a correction term when environmental forces exceed a predetermined limit, adjusting the rope's feeding to keep forces within safe limits, while omitting or reducing the deviation term's influence during peak forces, and reinstating it when forces return within acceptable ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If heave compensation is applied to hold the item at rest relative to the seabed, then the item stability is improved, but the lifting equipment may be overloaded by environmental forces
Solution Approach 1:
The control method dynamically adjusts the heave compensation by introducing a correction term that activates only when environmental forces exceed predetermined limits. This dynamic adjustment allows the system to maintain item stability under normal conditions while preventing overloading during extreme environmental events, resolving the contradiction between stability and force management.
Solution Approach 2:
The system changes the control parameter by adding a correction term to the heave compensation calculation when the force on the rope exceeds a threshold. This parameter change allows the controller to reduce the compensating force during extreme conditions, preventing overloading while maintaining stability during normal operation.
2Reliability
If the correction term is introduced to prevent overloading, then the force control is improved, but the system complexity increases
Solution Approach 1:
The correction term is applied locally only when and where needed - specifically when the force on the rope exceeds a predetermined limit. This localized application of the correction term improves force control reliability without requiring the entire control system to be overly complex, as the additional logic is activated only under specific extreme conditions.
3Force
If the deviation term is omitted during peak forces, then the overloading prevention is improved, but the position control accuracy decreases
Solution Approach 1:
The deviation term is periodically activated and deactivated based on the environmental conditions. During peak forces, the deviation term is omitted to prevent overloading, and when forces return to normal levels, the deviation term is reinstated to restore position control accuracy. This periodic action resolves the contradiction by temporarily sacrificing precision to prevent damage.
Data Source
AI summary
A method for lift compensation of an item (12) which is connected to a vessel (1) by means of a rope (4) which is coiled around the rope drum (6) of a lifting device (2), the lifting device (2) being provided with a heave compensator (20), a controller (30) of the heave compensator (20) controlling the effect of the driving device (32, 34, 42) of the rope drum (6) on the basis of a heave term and a deviation term, the method comprising: —bringing a correction term into the heave compensation when, because of environmental forces, the force on the rope (4) falls outside a first limit (d, e); and—leaving the correction term out when the force on the rope (4) is within a second limit (c, f), the second limit (c, f) being equal to or different from the first limit (d, e).