Dual Flexspline Strain Wave Actuator for Balanced Torque Load
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Solution Overview
Problem
Existing actuators incorporating strain wave gears face challenges in achieving balanced load distribution, minimizing twisting forces, and providing high efficiency tooth mesh, while also being compact, lightweight, and cost-effective with similar performance characteristics.
Innovation Solution
The actuator design includes a pair of flex splines oriented to face in opposite directions, earthed to annuli for fixed positioning, and a wave generator that elastically deforms the flex splines to engage with a circular spline, ensuring balanced load distribution and efficient tooth mesh without rotating the flex splines, along with pre-stage gearing and epicyclic gear trains for high gear ratios and torque capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single flex spline is used in the actuator, then the structure is simpler, but the load distribution becomes unbalanced and twisting forces increase
Solution Approach 1:
The single flex spline is segmented into two separate flex splines that face opposite directions. Each flex spline engages with the circular spline independently, dividing the load path and eliminating the twisting forces that occur with a single flex spline. This segmentation resolves the contradiction by maintaining structural simplicity while achieving balanced load distribution.
Solution Approach 2:
The two flex splines are oriented asymmetrically in opposite directions, with their splines engaging the circular spline at different angular positions. This asymmetric arrangement ensures that loads are distributed evenly around the circular spline, preventing the development of twisting moments while preserving overall structural efficiency.
2Strength
If the flex spline is made more rigid to withstand higher loads, then the load capacity increases, but the elastic deformation capability decreases
Solution Approach 1:
The flex spline is designed with non-uniform wall thickness, featuring thicker sections at the crown and root areas to provide higher strength and load capacity, while maintaining thinner sections in the spline teeth regions to preserve elastic deformation capability. This local quality variation resolves the contradiction by optimizing both strength and flexibility in different locations of the same component.
3Weight of moving object
If the actuator size is reduced for compactness, then the weight and volume decrease, but the torque capability is compromised
Solution Approach 1:
Two flex splines are merged into a single integrated actuator assembly that shares common mounting structures, bearings, and housing. This merging allows the actuator to achieve high torque capability through the combined effect of both flex splines while maintaining a compact overall size, as the components are space-efficiently arranged rather than simply doubling a single-spline design.
Solution Approach 2:
The two flex splines are arranged in an axial configuration rather than radial, utilizing the axial dimension to stack the spline pairs. This dimensional arrangement allows the actuator to generate high torque through multiple spline engagements while maintaining a compact radial footprint, effectively resolving the contradiction between size and torque capability.
4Power
If more flex splines are added to increase torque capability, then the power output increases, but the device complexity and cost increase
Solution Approach 1:
The wave generator is designed as a universal component that can simultaneously engage with multiple flex splines arranged around it. This multi-functional wave generator design allows the actuator to achieve high torque capability through multiple spline pairs without requiring separate drive mechanisms for each flex spline, thereby avoiding excessive complexity while maintaining enhanced power output.
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
This design results in an actuator with balanced load distribution, reduced twisting forces, higher efficiency, lower weight, smaller size, improved reliability, and lower costs, suitable for applications requiring high gear ratios and precise inertial load repositioning.
Implementation Method 1
The wave generator is configured to elastically deform both of the pair of flex splines when the input shaft activates the wave generator
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
An actuator (12) is disclosed. The actuator (12) comprises an input shaft (18), a wave generator (56), a pair of flex splines (66,68), a pair of earth annuli (14,16), and an output annulus (20). Each of the pair of flex splines (66,68) are earthed to an earth annulus (14,16). The output annulus (20) comprises a circular spline (92). The wave generator (56) is configured to be activated by rotation of the input shaft (18), and the wave generator (56) is configured to elastically deform both of the pair of flex splines (66,68) when the input shaft (18) activates the wave generator (56).