Oil-Filled Electric Subsea Manipulator for Precise Force Control
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Solution Overview
Problem
Current subsea manipulation systems, particularly for remotely operated underwater vehicles (ROVs), lack sophisticated control mechanisms and are limited by the use of hydraulic manipulators that are weak and lack positional or force feedback, making them unsuitable for advanced manipulation tasks.
Innovation Solution
The development of a subsea manipulator using oil-filled electric actuators with coordinated joint control, including linear actuators and an end effector with a rotational joint and tool motor, enabling precise motion control and tool changes without human intervention, utilizing a split spring engagement ring clamp for tool attachment and detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If hydraulic manipulators are used for subsea applications, then high force and power are achieved, but positional precision and force feedback are lost
Solution Approach 1:
The patent replaces hydraulic actuators with electric actuators that incorporate direct-drive motors and precision encoders. This substitution eliminates hydraulic fluid dynamics while providing both high torque output and precise positional feedback through electronic control systems and feedback sensors, resolving the contradiction between power delivery and measurement precision.
Solution Approach 2:
The patent implements comprehensive feedback systems including joint position encoders, force/torque sensors at the end effector, and pressure sensors for oil-filled actuators. These feedback mechanisms enable closed-loop control that maintains high force output while achieving precise positional and force control, directly addressing the lack of feedback in traditional hydraulic systems.
2Measurement precision
If electric actuators are used for subsea manipulation, then positional precision and control sophistication are improved, but force capacity is reduced
Solution Approach 1:
The patent employs nested actuation systems where electric motors provide primary motion control, while oil-filled chambers within the same actuator housing provide force amplification and compliance control. This nested architecture allows the system to achieve both precise positional control from the electric motor and high force capacity from the hydraulic-like oil pressure, simultaneously satisfying both requirements.
Solution Approach 2:
The patent uses composite actuation mechanisms combining electric motor components with oil-filled flexible chambers. The electric motor provides precision motion while the oil-filled elastomeric chambers provide force multiplication and compliance, creating a composite actuator that delivers both high precision and high force capacity.
3Force
If oil pressure is increased to maintain force capacity, then force output is maintained, but risk of leakage and failure increases
Solution Approach 1:
The patent changes the pressure parameter from high-pressure hydraulic operation to low-pressure oil-filled operation. The oil-filled actuators operate at pressures sufficient to provide compliance and force assistance but far below traditional hydraulic pressures, dramatically reducing leakage risks and component failure modes while maintaining force capacity through the compliance mechanism.
Solution Approach 2:
The patent employs sealed, maintenance-free electric actuators with integrated oil-filled chambers that eliminate the need for complex hydraulic sealing systems. The simplified architecture with fewer high-pressure interfaces reduces points of failure and improves reliability, even though individual components may be less robust than heavy-duty hydraulic systems.
4Adaptability or versatility
If tool changes are performed manually in subsea environment, then tool replacement is possible, but operation time and human intervention are increased
Solution Approach 1:
The patent implements an automated tool change system where the ROV manipulator autonomously performs tool attachment and detachment operations. The system uses sensor feedback to locate tools, align the end effector, execute the change sequence, and verify successful replacement without human intervention, eliminating manual tool change time while maintaining full tool interchangeability.
Solution Approach 2:
The patent employs pre-positioned tools in standardized holders and pre-configured end effectors with automated grippers. The tool change system is pre-programmed with tool locations and change sequences, allowing rapid automated replacement without manual positioning or complex alignment procedures, significantly reducing tool change time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for precise and efficient control of the manipulator, enabling advanced manipulation tasks with force and impedance control, and facilitates autonomous tool changes, improving reliability and accuracy in subsea operations.
Implementation Method 1
The pressure of the oil in the manipulator is at least 1 psi higher than the hydrostatic pressure outside the actuator
Data Source
AI summary
A subsea manipulator for a remotely operated underwater vehicle (ROV) that includes at least one linear, oil-filled electric actuator to control a motion of the manipulator in a subsea environment is disclosed. The remotely operated underwater manipulator includes an electric actuator for each axis of motion of the manipulator, and an end effector that includes a rotational joint and a tool motor for controlling a tool affixed to the end effector. A method for changing the tool of the manipulator in a subsea environment is disclosed.