Eddy Current Clutch Actuator Arrangement for Aerospace
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Solution Overview
Problem
Existing actuator arrangements for variable area fan nozzle cowls and other aerospace components are heavy and large due to the use of variable speed motors and complex control circuits, which is undesirable for space-constrained aircraft applications, and replacing them with fixed speed motors requires robust stops to prevent overextension, leading to increased size and weight.
Innovation Solution
An actuator arrangement utilizing an epicyclic gear set with an eddy current clutch, comprising a permanent magnet and a conducting element, which provides resistance to rotation and allows for a fixed speed motor operation, reducing the need for large stops and simplifying the system by decoupling the motor from the actuator, thereby minimizing inertia and shock loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a variable speed motor and associated control circuits are used to drive the actuator, then reliable position control is achieved, but the actuator arrangement becomes relatively large and heavy
Solution Approach 1:
The patent extracts the speed control function from the motor itself and places it in the load side through the eddy current clutch. The motor runs at constant speed while the clutch controls the actual actuator speed, separating the control burden from the motor and reducing overall system complexity and weight.
Solution Approach 2:
The patent replaces complex electronic control circuits with a mechanical/electromagnetic solution using an eddy current clutch. The clutch uses electromagnetic fields to provide frictionless torque transmission and speed control, eliminating the need for complex electronic control systems while maintaining reliable position control.
2Weight of moving object
If a fixed speed motor operating in open loop fashion is used to reduce size and weight, then motor and control circuit weight is reduced, but larger and more robust stops are required to prevent over extension during every operating cycle
Solution Approach 1:
The eddy current clutch acts as an intermediary between the motor and actuator, providing a controlled coupling that limits torque transmission. This allows the system to use a fixed speed motor with open loop control while the clutch prevents excessive forces from reaching the stops, enabling smaller stop design.
Solution Approach 2:
The eddy current clutch provides beforehand cushioning by continuously damping torque fluctuations and preventing shock loads before they reach the stops. This protective function allows the stops to be designed for normal operation rather than worst-case scenarios, reducing their size and weight.
3Device complexity
If fixed speed motor with open loop control is used, then system complexity is reduced, but the stops must repeatedly arrest actuator movement at high speed
Solution Approach 1:
The patent replaces the mechanical shock absorption function of the stops with an electromagnetic damping system (eddy current clutch). The clutch continuously dissipates energy and dampens oscillations, preventing high-speed impacts that would require durable stops, while maintaining simple open loop control.
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 enables a compact, lightweight actuator system with reduced stop size and weight, reliable operation, and simplified control, while maintaining reliable position control and preventing overextension or retraction without the need for complex closed-loop control schemes.
Implementation Method 1
the eddy current clutch comprises a permanent magnet and a conducting element, one of which is carried by the ring gear and the other being fixed, with an air gap being provided between the magnet and conducting element
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An actuator arrangement comprises an epicyclic gear set 4a, 4b including a sun gear 7, at least one planet gear 9 in meshing engagement with the sun gear 7, and a ring gear 3 in meshing engagement with the planet gear 9, the planet gear 9 being carried by a rotatable support 5, wherein one of the sun gear 7 and the support 5 is arranged to be driven by a motor 2 and the other of the sun gear 7 and the support 5 is arranged to drive an actuator 18, and a clutch arrangement 6 operable to resist rotation of the ring gear 3.