Nested Harmonic Gear Redundancy for Continuous Torque Transfer
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Solution Overview
Problem
Existing harmonic gear systems lack redundancy in load paths between input and output shafts, which is required for safety in actuation systems like those in aircraft to prevent disconnect after failure.
Innovation Solution
A harmonic gear system with redundant load paths is designed, featuring nested cup-shaped flex splines and circular splined shafts connected to a radial flange, driven by a wave generator bearing, ensuring continuous operation even if one path fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single load path is used in harmonic gear systems, then the device complexity is reduced, but the reliability is insufficient to meet safety codes and standards for actuation systems
Solution Approach 1:
The patent implements nested flex splines where a first flex spline and a second flex spline are positioned concentrically, with the second flex spline nested within the first flex spline. Both flex splines share a common wave generator and are driven simultaneously, creating redundant load paths from the input shaft to the output shaft while maintaining a compact structure. This nesting approach provides reliability through redundancy without proportionally increasing device complexity.
2Reliability
If nested flex splines are used to provide redundant load paths, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The wave generator serves multiple functions simultaneously: it drives both the first flex spline and the second flex spline, and both flex splines independently transmit torque to the output shaft through separate circular splined shafts. This multi-functionality allows the system to maintain reliability through redundant load paths while avoiding proportional increases in complexity, as a single input motion produces multiple output paths.
Solution Approach 2:
The patent merges the driving function into a single wave generator that simultaneously engages both nested flex splines. Both flex splines are driven by the same wave generator motion and both transmit power to the same output shaft, combining multiple load paths into a unified structure that provides redundancy without requiring separate drive mechanisms for each path.
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 continuous operation by eliminating the possibility of disconnect between input and output shafts, enhancing safety and reliability in actuation systems.
Implementation Method 1
a wave generator bearing surrounding the wave generator; first and second cup-shaped flex splines, wherein the second flex spline is nested within the first flex spline, and the first and second flex splines are grounded to the forward end of the housing, and the first and second flex splines are simultaneously biased by the wave generator via the wave generator bearing
Data Source
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AI summary
A harmonic gear system, having: a housing (110); an input shaft (120) having an aft end within the housing (110) that defines a wave generator (130); a wave generator bearing (140); first and second nested cup-shaped flex splines (150A, 150B) that are grounded to the housing (110), the first and second flex splines (150A, 150B) are biased by the wave generator (130) via the wave generator bearing (140); an output shaft (160) having a forward end that is within the housing (110), and a radial flange at the forward end; first and second nested circular splined shafts (180A, 180B) within the housing (110), the first and second circular splined shafts (180A, 180B) are connected to the radial flange of the output shaft (160) and are driven by ones of the first and second flex splines (150A, 150B), to thereby drive the output shaft (160); and a bearing between the first and second circular splined shafts (180A, 180B).