Actuator Torsion Shaft Coupling for Side Loading Mitigation
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Solution Overview
Problem
Electrically driven linear actuators in aerospace applications, such as nose-wheel steering, face increased wear and damage due to significant side loadings, which can be mitigated by enhancing support structures but result in increased weight and the need for more powerful actuators.
Innovation Solution
Incorporating a torsion shaft coupling between the shaft and steering rack to accommodate limited relative lateral movement, with a spring-biased coupling and damper mechanisms to manage side loadings, and using a telescoping housing to reduce actuator size and prevent debris ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the support structure is enhanced to permit reaction of side loadings, then the reliability of the actuator is improved, but the weight of the actuator increases
Solution Approach 1:
A flexible coupling is introduced as an intermediary element between the shaft and the steering rack. This coupling accommodates lateral movements and misalignments without requiring rigid support structures, thereby avoiding the weight penalty while still protecting the actuator from damaging side loadings. The flexible coupling serves as a mediator that absorbs the shock and lateral forces that would otherwise be transmitted to the actuator components.
2Manufacturing precision
If a rigid coupling is used between the shaft and steering rack, then the manufacturing precision is improved, but the actuator becomes more susceptible to wear and damage from side loadings
Solution Approach 1:
The coupling between the shaft and steering rack is designed to be flexible rather than rigid, allowing it to dynamically adapt to lateral movements and misalignments that occur during operation. This dynamic coupling maintains adequate alignment for precise operation while simultaneously accommodating the lateral forces generated during steering, preventing the transmission of damaging side loadings to the actuator components.
3Ease of operation
If the actuator is designed to accommodate lateral movements, then the ease of operation is improved, but the device complexity increases
Solution Approach 1:
A flexible coupling serves as an intermediary mechanism that enables the actuator to accommodate lateral movements without requiring complex active control systems or multiple components. The coupling passively absorbs lateral displacements through its inherent flexibility, allowing the steering system to operate smoothly over uneven surfaces and during dynamic steering maneuvers while adding minimal complexity to the overall actuator design.
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 effectively reduces the transmission of side loadings to the shaft, minimizing wear and damage while maintaining actuator performance and reducing weight, and allows for efficient operation and reduced maintenance.
Implementation Method 1
the coupling comprises a torsion shaft interconnecting the rack and the shaft, wherein the torsion shaft interconnects the shaft with an end of the rack remote from the shaft
Implementation Method 2
with a spring-biased coupling and damper mechanisms to manage side loadings
Implementation Method 3
with a spring-biased coupling and damper mechanisms to manage side loadings
Data Source
Figure 1
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Figure 3
AI summary
An actuator comprises a rotatable nut (20, 68) arranged to be driven for rotation by a motor, an axially translatable shaft (24, 72) cooperable with the nut (20, 68) and arranged such that rotation of the nut (20, 68) drives the shaft (24, 72) for axial movement, and a steering rack (12, 54) coupled to the shaft (24, 72) by a coupling (26, 86) so as to be driven for axial movement by the shaft (24, 72), wherein the coupling (26, 86) accommodates limited relative lateral movement between the shaft (24, 72) and the steering rack (12, 52).