Summing Rotary Actuator Assembly Fault Tolerance
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Solution Overview
Problem
Existing redundant actuator systems lack effective redundancy mechanisms to ensure continuous operation in case of mechanical jams, electrical motor failures, or loss of power, particularly in applications requiring precise control like helicopter rotor blades and aircraft flight surfaces.
Innovation Solution
A rotary actuator assembly with multiple sub-actuators and linkages configured to sum torque and allow selective rotation of the output member, featuring electromagnetic reluctance hold devices to restrain and release rotors, ensuring continuous operation even if one actuator fails, with a linkage system that maintains motion and torque transfer across the range of rotary motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple actuators are arranged to sum torque, then reliability is improved, but device complexity increases
Solution Approach 1:
The actuator assembly is divided into multiple independent sub-actuators (first sub-actuator with first rotor, second sub-actuator with second rotor, third sub-actuator with third rotor), each capable of independently producing torque. This segmentation allows the system to maintain functionality even when one sub-actuator fails, as the remaining sub-actuators can continue to operate and sum their torque to drive the output member.
Solution Approach 2:
Multiple sub-actuators are merged into a single integrated assembly where their torque outputs are combined through a common linkage system. The linkages from each sub-actuator converge at the output member, allowing the individual torque contributions to be summed mechanically. This merging provides redundancy while maintaining a unified control structure.
2Reliability
If linkages are configured to maintain motion transfer across range of motion, then reliability is improved, but device complexity increases
Solution Approach 1:
The linkage system is designed with dynamic characteristics that allow it to adapt to different positions within the range of motion. The linkages are configured with specific geometric relationships (including non-intersecting and intersecting arrangements) that enable continuous torque transfer regardless of the output member's angular position. This dynamic adaptability ensures reliable operation throughout the entire motion range without requiring additional switching mechanisms.
Solution Approach 2:
The linkage system acts as an intermediary mechanism between the sub-actuators and the output member. It translates the rotational motion from each sub-actuator into coordinated motion at the output member, maintaining continuous torque transfer. The linkages serve as mechanical mediators that ensure smooth power transmission even when sub-actuators are at different positions in their rotation ranges.
3Reliability
If electromagnetic reluctance hold devices are added to restrain and release rotors, then reliability is improved, but device complexity increases
Solution Approach 1:
Electromagnetic reluctance hold devices are incorporated into each sub-actuator to preliminarily restrain the rotors in predetermined positions before failure occurs. These hold devices are pre-configured to engage automatically when a sub-actuator fails, preventing uncontrolled motion and maintaining system stability. The preliminary positioning capability allows the failed sub-actuator to be safely isolated while the remaining sub-actuators continue operation.
Solution Approach 2:
The electromagnetic reluctance hold devices provide self-service functionality by automatically engaging and disengaging based on the operational state of each sub-actuator. When a sub-actuator fails, the hold device automatically restrains the rotor without requiring external intervention. The devices self-regulate the positioning and locking of rotors, reducing the need for complex external control systems while maintaining reliability.
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 system provides triple redundancy and fault tolerance, ensuring continuous motion and control of driven objects like helicopter rotor blades and aircraft surfaces, even in failure scenarios, by allowing other actuators to take over and maintain operation within the defined range of motion.
Implementation Method 1
the first sub-actuator (102) comprising a first stator element (124) and a first rotor (104) configured to selectively rotate about the first sub-axis of rotation (103) relative to the first sub-actuator housing (170)
Implementation Method 2
wherein a torque produced by the first rotor (104) is transferred through the first linkage axis (109) and the second linkage axis (119) and thereby summed at the output axis (11)
Data Source
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AI summary
An actuator assembly comprising an output member rotatable about an output axis, first and second actuators each having an axis of rotation, a drive motor and a hold motor, first and second linkages between each of the first and second actuators and the output member, wherein a torque produced by a drive motor is summed through the linkages at the output member when the respective hold motor is restrained from rotating, and wherein the respective hold motor may be selectively released so that it rotates with a failure of the respective drive motor, and wherein one of the first or second actuators may be driven to selectively rotate the output member with a failure of the drive motor of the other of the first or second actuators. The assembly may comprise a third actuator linked to the output member in the same manner as the first and second actuators.