Balanced Inverted Harmonic Drive to Prevent Torque Binding
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Solution Overview
Problem
Unbalanced inverted compound harmonic drives in aircraft flight control systems experience binding due to unbalanced reactionary forces, reducing efficiency in energy transmission.
Innovation Solution
A balanced inverted compound harmonic drive design is implemented, featuring a wave generator, flex spline, and ground gears with specific gear ratios and bearings, ensuring balanced torque distribution and preventing off-axis motion, which includes a pair of ground gears with respective shafts and bearings to support the output gear radially without binding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an unbalanced inverted compound harmonic drive is used, then the structure is simpler, but binding occurs due to unbalanced reactionary forces reducing energy transmission efficiency
Solution Approach 1:
The patent applies asymmetry by configuring the ground gears and shafts in a specific asymmetric arrangement where the first ground gear and first shaft are positioned differently from the second ground gear and second shaft. This asymmetric configuration allows the reactionary forces to be distributed in a way that balances the overall drive system, preventing binding while maintaining structural efficiency
Solution Approach 2:
The patent implements counterbalancing by introducing a second ground gear and second shaft that generate reactionary forces opposite to those of the first ground gear and first shaft. These counteracting forces neutralize each other, eliminating the unbalanced reactionary forces that cause binding in conventional designs
2Loss of energy
If ground gears and shafts are added to balance torque distribution, then energy transmission efficiency improves, but device complexity increases
Solution Approach 1:
The patent merges the ground gears and shafts directly into the existing drive structure, integrating them with the flex spline and wave generator. This integration allows the balancing components to be incorporated without adding separate, independent assemblies, thereby limiting the increase in device complexity
Solution Approach 2:
The ground gears and shafts serve multiple functions: they provide structural support, transmit torque, and generate counterbalancing reactionary forces. This multi-functionality allows a single component to address multiple requirements, reducing the need for additional specialized components
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 design effectively prevents binding, ensuring efficient energy transmission and maintaining system efficiency by distributing torque evenly and supporting radial output without off-axis motion.
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; and a first ground gear adjacent to and forward of the output gear that meshes with the first axial end spline
Implementation Method 3
the first axial end bearing and the second axial end bearing may be ball bearings
Implementation Method 4
the axial center bearing is a roller bearing, a ball bearing or a plain bearing
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An inverted compound harmonic drive (100) including: a wave generator (110) configured to receive rotational input; a flex spline (120) disposed radially within the wave generator (110) that receives energy due to the rotation of the wave generator (110), the flex spline (120) including a plurality of inner facing splines (130) that include an axial center spline (130a), a first axial end spline (130b) being adjacent to and forward of the axial center spline (130a), and a second axial end spline (130c) adjacent to and aft of the axial center spline (130a); an output gear (140) meshes with the axial center spline (130a); a first ground gear (150) adjacent to and forward of the output gear (140) that meshes with the first axial end spline (130b); and a second ground gear (160) adjacent to an aft of the output gear (140) that meshes with the second axial end spline (130c).