Inverted Compound Harmonic Drive for Binding-Free Torque Balance
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Solution Overview
Problem
Unbalanced electro-mechanical actuators in flight control systems induce binding due to unbalanced reactionary forces, reducing efficiency in aircraft flight control systems.
Innovation Solution
An inverted compound harmonic drive is designed with a wave generator, flex spline, and ground gears with specific gear ratios and bearing configurations to balance torque distribution and prevent off-axis motion, ensuring efficient energy transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional harmonic drive is used in an electro-mechanical actuator, then the gear reduction ratio is achieved, but unbalanced reactionary forces cause binding and reduce efficiency
Solution Approach 1:
The patent inverts the conventional harmonic drive configuration by placing the wave generator on the output side rather than the input side. This inversion redistributes the reactionary forces throughout the gear train, balancing the loads on bearings and eliminating the binding that occurs in conventional designs while maintaining the required gear reduction ratio
Solution Approach 2:
The patent modifies the structural parameters of the harmonic drive by changing the configuration of splines and gear meshing points. Specifically, it uses multiple axial splines (first axial end spline, second axial end spline, and axial center spline) with different gear ratios to distribute forces more evenly, preventing binding and improving reliability
2Ease of operation
If the wave generator is positioned on the input side, then rotational input is easily received, but off-axis motion occurs reducing efficiency
Solution Approach 1:
The patent inverts the conventional arrangement by positioning the wave generator on the output side rather than the input side. This inversion allows the input shaft to remain simple while the wave generator's motion is constrained by the bearing configuration, preventing off-axis motion and improving operational reliability
Solution Approach 2:
The patent introduces axial bearings as intermediary elements between the wave generator and the housing. These bearings (first axial end bearing, second axial end bearing, and axial center bearing) act as mediators to constrain the wave generator's motion, preventing off-axis movement while allowing the necessary rotational input to be transmitted efficiently
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 balanced gear configuration prevents binding, allowing for efficient energy transmission and maintaining radial output without off-axis motion, enhancing the performance of electro-mechanical actuators in aircraft flight control systems.
Implementation Method 1
a wave generator configured to receive rotational input; a flex spline disposed radially within the wave generator that receives energy due to the rotation of the wave generator
Implementation Method 2
an output gear meshes with the axial center spline; a first ground gear adjacent to and forward of the output gear that meshes with the first axial end spline; and a second ground gear adjacent to and aft of the output gear that meshes with the second axial end spline
Implementation Method 3
a first axial end bearing disposed between the first ground shaft and the wave generator; second axial end bearing disposed between the second ground shaft and the wave generator; and an axial center bearing disposed between the flex spline and the wave generator
Implementation Method 4
The first axial end bearing and the second axial end bearing are ball bearings; and the axial center bearing is a roller bearing, a ball bearing or a plain bearing
Data Source
AI summary
An inverted compound harmonic drive including: a wave generator configured to receive rotational input; a flex spline disposed radially within the wave generator that receives energy due to the rotation of the wave generator, the flex spline including a plurality of inner facing splines that include an axial center spline, a first axial end spline being adjacent to and forward of the axial center spline, and a second axial end spline adjacent to and aft of the axial center spline; an output gear meshes with the axial center spline; a first ground gear adjacent to and forward of the output gear that meshes with the first axial end spline; and a second ground gear adjacent to an aft of the output gear that meshes with the second axial end spline.