Heave Compensating System with Electric Motor Hydraulic Control
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Solution Overview
Problem
Existing heave compensating systems for marine vessels are complex, expensive, and unable to effectively compensate for force variations due to pressure-dependency and friction damping, leading to unpredictable core compactions or drill bit wear during seabed operations.
Innovation Solution
A heave compensating system that combines two hydraulic machines and an electric motor, where the motor is connected between the machines' drive shafts, with a controller that adjusts hydraulic pressure and load position to maintain a constant support force, using a valve to bypass hydraulic machines when pressure falls below a threshold, and an electric motor to actively control energy balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a purely passive heave compensator arrangement is used, then the system is simple and cost-effective, but it exhibits substantial force variations due to pressure-dependency of the accumulator on its charge
Solution Approach 1:
The patent replaces the traditional mechanical position-dependant transmissions with an electric motor-driven active control system. The motor compensates for friction damping and inertia effects that cannot be addressed by passive mechanical arrangements, thereby reducing force variations while maintaining operational simplicity.
Solution Approach 2:
The system incorporates feedback control where the electric motor actively adjusts the hydraulic fluid flow based on detected force variations and position changes. This feedback mechanism compensates for the pressure-dependency of the accumulator, maintaining more consistent force application despite vessel heave motion.
2Force
If mechanical position-dependant transmissions are added to compensate for accumulator charge variations, then force variations are reduced, but the system becomes more complex and cannot compensate for friction damping and inertia effects
Solution Approach 1:
The patent substitutes complex mechanical position-dependant transmissions with an electric motor-driven hydraulic control system. The motor can actively compensate for friction damping and inertia effects through controlled fluid flow adjustment, achieving better force stability without the mechanical complexity of traditional transmissions.
Solution Approach 2:
The system changes the control parameter from mechanical position-dependent transmission ratios to electric motor-controlled hydraulic flow rates. This allows dynamic adjustment of the hydraulic system parameters to compensate for friction and inertia effects, providing superior force compensation while reducing mechanical complexity.
3Force
If an active heave compensator arrangement is added to compensate for force variations, then force control is improved, but the system becomes complicated, expensive, and bulky
Solution Approach 1:
The electric motor serves multiple functions: it compensates for friction damping, counteracts inertia effects, and actively controls hydraulic fluid flow to maintain force balance. This multi-functionality achieves improved force control without requiring separate dedicated components for each compensation function, thereby limiting the increase in system complexity.
Solution Approach 2:
The patent uses hydraulic fluid as the working medium to transmit force and control the compensating mechanism. The hydraulic system, combined with the electric motor, provides smooth and precise force control while avoiding the mechanical complexity and bulk of purely mechanical active compensation systems.
4Stress or pressure
If the accumulator charge pressure is adjusted to balance static load, then the nominal hydraulic pressure is determined, but the system cannot compensate for friction damping and inertia effects during dynamic heave motion
Solution Approach 1:
The electric motor is controlled based on feedback from position and force sensors, allowing it to dynamically adjust hydraulic fluid flow to compensate for friction damping and inertia effects during dynamic heave motion. This feedback control maintains reliable compensation across varying operating conditions beyond just static load balance.
Solution Approach 2:
The system transitions from static accumulator charge pressure adjustment to dynamic electric motor-controlled hydraulic flow regulation. The motor can adapt the hydraulic pressure and flow rate in real-time to compensate for dynamic effects such as friction damping and inertia during vessel heave motion, significantly improving compensation reliability.
Data Source
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AI summary
According to the present invention, there is provided a heave compensating system for a marine vessel, the system being configured to maintain a substantially constant support force on a load suspended from the vessel despite heaving movement of the vessel. The system comprises a hydraulic actuator arranged for connection between the vessel and a load to be suspended from the vessel, the actuator being hydraulically actuable to vary the distance between the load and the vessel in response to heaving motion of the vessel. The hydraulic actuator is fluidly connected to a first hydraulic machine for actuation by the first hydraulic machine. The system further comprises a second hydraulic machine in fluid connection with a hydraulic accumulator. The first and second hydraulic machines are mechanically connected to one another and also both mechanically connected to a shared electric motor. The system further comprises a controller arranged to control hydraulic movement of the first and second hydraulic machines and to control the supply of power to the electric motor in response to one or more signals representative of a wave-induced heave movement of the vessel and/or a wave induced force applied to the load.