Grooved Wave Generator Reduces Inertia in Harmonic Drive
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Solution Overview
Problem
High inertia of compound harmonic drive gears affects their responsiveness, particularly at high speeds, limiting their performance in applications requiring quick changes in direction and speed.
Innovation Solution
Incorporating a wave generator with radially extending grooves that reduce the weight and inertia of the gear system, combined with a flex spline and a rolling element, such as a roller bearing, to enhance responsiveness and cooling through increased lubricant contact volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the wave generator body is made solid without grooves, then the structural strength is improved, but the inertia increases and responsiveness deteriorates
Solution Approach 1:
The wave generator body is segmented by introducing radial grooves that divide the solid structure into separate sections. This segmentation reduces the overall mass and inertia of the wave generator while maintaining structural integrity through the grooved design, thereby improving responsiveness without completely compromising strength.
Solution Approach 2:
The grooves are strategically positioned in specific regions of the wave generator body where material can be removed to reduce inertia without critically affecting the overall structural strength. This local modification approach allows optimization of the inertia-to-strength ratio by concentrating material where it is most needed for structural support.
2Speed
If the wave generator body is made with grooves to reduce inertia, then the responsiveness is improved, but the structural strength may be compromised
Solution Approach 1:
The radial grooves segment the wave generator body into distinct sections, reducing mass and inertia to improve responsiveness. The segmentation is designed to maintain adequate structural strength by preserving material in critical load-bearing regions while removing material where it contributes least to structural integrity.
Solution Approach 2:
The grooves are placed in specific locations where material removal has minimal impact on overall structural strength. This localized modification allows the design to achieve reduced inertia for improved responsiveness while maintaining sufficient strength through strategic material distribution.
3Speed
If the wave generator body is made lighter with grooves, then the inertia is reduced and responsiveness is improved, but the manufacturing complexity increases
Solution Approach 1:
The radial grooves create a segmented structure that can be manufactured using standard machining operations. The grooves are designed to be accessible and machineable, allowing the complex-looking structure to be produced through sequential cutting operations rather than requiring advanced manufacturing processes.
Solution Approach 2:
The grooves are positioned and dimensioned to optimize the balance between inertia reduction and manufacturability. The design considers manufacturing constraints by ensuring grooves are accessible to cutting tools and can be produced with standard tolerances, avoiding overly complex geometries that would significantly increase manufacturing difficulty.
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 reduces the inertia of the gear system, enabling faster response times and improved motor performance by allowing quicker changes in direction and speed, thus enhancing the overall responsiveness of the compound harmonic drive assembly.
Implementation Method 1
The rolling element is disposed between the wave generator and the flex spline
Implementation Method 2
enabling faster response times and improved motor performance by allowing quicker changes in direction and speed, thus enhancing the overall responsiveness of the compound harmonic drive assembly
Data Source
Figure 1~2
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Figure 5~6
AI summary
A compound harmonic drive assembly includes a ring gear assembly (30), a wave generator (36), a flex spline (32), and a rolling element (34). The wave generator is received within the ring gear assembly along the rotational axis. The wave generator has a body (110) that extends radially between an exterior surface (112) and an interior surface (114). The body defines at least one groove (120) that extends radially from the exterior surface towards the interior surface. The flex spline (32) is disposed between the ring gear assembly and the wave generator. The rolling element is disposed between the wave generator and the flex spline.