Eddy Current Brake for Controlled Fail-Safe Actuator Return
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Solution Overview
Problem
Existing actuator technologies with fail-safe features often result in rapid movement upon power loss, leading to potential damage and fluid pressure surges, as they rely on mechanical springs or complex transmission systems that are bulky, high-torque, and susceptible to failure.
Innovation Solution
An electric actuator system incorporating a differential and an eddy current brake, which stores energy from a primary driving source and releases it through a secondary driving source to move the output to a fail-safe position, using an eddy current brake to control the speed and prevent rapid movement by generating a braking force through the transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical spring return system is used for fail-safe actuation, then the actuator can move to a pre-determined position upon power loss, but the system occupies high volume, requires high torque, and is susceptible to failure
Solution Approach 1:
The patent replaces the traditional mechanical spring return system with an electric motor and differential mechanism. The electric motor (second driving source) is coupled to the output through a differential, and upon power loss, the motor's inertia and the differential's mechanical advantage enable the output to move to the fail-safe position without requiring a bulky mechanical spring transmission system.
Solution Approach 2:
The electric motor serves multiple functions: it acts as the primary driving source during normal operation and as the fail-safe driving source upon power loss. The differential mechanism simultaneously enables both forward and reverse motion control, eliminating the need for separate mechanical spring return mechanisms.
2Reliability
If a mechanical spring return system is used for fail-safe actuation, then the actuator can move to a pre-determined position upon power loss, but the system requires high torque
Solution Approach 1:
The patent replaces the high-torque mechanical spring system with an electric motor that utilizes electromagnetic torque. The motor's torque characteristics can be controlled electronically, and the differential mechanism provides mechanical advantage to reduce the peak torque requirements compared to a direct mechanical spring return system.
Solution Approach 2:
The system utilizes the dynamic characteristics of the electric motor, including its moment of inertia and controlled acceleration/deceleration profiles. The motor can be controlled to build up speed and kinetic energy before the power loss occurs, allowing the stored kinetic energy to carry the system through the fail-safe transition without requiring excessive peak torque.
3Reliability
If the actuator rapidly strokes to its fail position upon power loss, then the fail-safe position is reached quickly, but damage may be caused to the actuator and/or any equipment attached to the actuator
Solution Approach 1:
The patent incorporates feedback control through the differential mechanism and controlled braking systems. The differential provides mechanical feedback that naturally limits the speed of the output movement, and optional braking mechanisms can be activated to control the rate of movement to the fail-safe position, preventing damage from rapid stroking.
Solution Approach 2:
The electric motor's dynamic characteristics allow for controlled deceleration and speed management. The motor can be controlled to reduce speed as it approaches the fail-safe position, and the differential mechanism's mechanical properties naturally dampen rapid movements, preventing the harmful water hammer effects associated with rapid valve closure.
4Reliability
If a rapid stroke to fail position is implemented, then the fail-safe position is reached quickly, but a substantial fluid pressure surge (water hammer) may be induced
Solution Approach 1:
The differential mechanism provides mechanical feedback that naturally regulates the speed of the output movement. The controlled braking systems can be activated to manage the rate of valve closure, ensuring that the fluid pressure surge is kept within acceptable limits while still achieving fail-safe positioning.
Solution Approach 2:
The electric motor's dynamic control capabilities allow for managed deceleration profiles. The system can be controlled to slow down as it approaches the fail-safe position, and the differential's mechanical properties provide natural damping, preventing the rapid closure that causes water hammer effects while maintaining adequate fail-safe response 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
The solution provides a compact, low-cost, and effective means to control output speed during power loss, reducing the risk of damage by slowing down the movement to the fail-safe position, thereby preventing fluid pressure surges and equipment damage.
Implementation Method 1
an eddy current brake coupled to the output through the transmission that reduces a speed at which the second driving source moves the output to the fail-safe position
Data Source
AI summary
Aspects of the disclosure provide an electric actuator including a first driving source coupled to an output through a first pathway created by a transmission, a second driving source coupled to the output though a second pathway created by the transmission that, upon the electric actuator losses electrical power to the electric actuator, causes the output to be positioned at a fail-safe position, a differential coupled to the first driving source and the second driving source through a third pathway created by the transmission to store energy from the first driving source in the second driving source, and an eddy current brake coupled to the output through the transmission that reduces a speed at which the second driving source moves the output to the fail-safe position.