Nested Harmonic Drive Actuator for High Ratio in Compact Space
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Solution Overview
Problem
Existing actuator systems face challenges in achieving a high drive ratio without increasing their size, as larger actuators are required to provide higher drive ratios, conflicting with the need for a compact design.
Innovation Solution
The actuator assembly incorporates a motor, harmonic drive, and a dual gear set mechanism with planetary gears and sun/ring gears to achieve a high drive ratio of at least 600:1 while maintaining a compact axial footprint, utilizing a collar and bearing elements for rotational support and axial nesting of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of the actuator is increased to provide higher drive ratios, then the drive ratio is improved, but the overall size of the system increases
Solution Approach 1:
The patent applies nesting by placing the second gear set inside the first gear set, with the second sun gear positioned within the first planetary gear arrangement. This nested configuration allows multiple gear stages to occupy overlapping spatial volumes, achieving a drive ratio of at least 600:1 without proportionally increasing the actuator's external dimensions.
Solution Approach 2:
The patent utilizes axial nesting to arrange gear components along the axial dimension. The second gear set is positioned axially between the first gear set and the motor shaft, effectively using the axial direction to pack additional reduction stages without significantly increasing the radial or lateral footprint of the actuator.
2Volume of moving object
If the axial footprint is reduced to make the actuator more compact, then the overall size is improved, but the drive ratio may be compromised
Solution Approach 1:
The second gear set is nested within the spatial envelope of the first gear set, allowing the patent to maintain a compact axial footprint while accumulating substantial gear reduction. The nested arrangement enables the drive mechanism to achieve at least 600:1 reduction without requiring extended axial length.
Solution Approach 2:
The drive mechanism is segmented into two distinct gear sets, each providing partial reduction. The first gear set and second gear set are arranged in series with the second nested within the first, allowing the total drive ratio to be distributed across multiple stages rather than requiring a single large-stage reduction that would increase axial footprint.
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 enables a high drive ratio of at least 600:1 in a compact actuator system, reducing the overall size while maintaining efficiency and structural integrity.
Implementation Method 1
harmonic drive connected to the motor shaft
Implementation Method 2
The first gear set has a first carrier including a second sun gear. The first carrier supports a first plurality of planetary gears that engage both the first sun gear and a first ring gear
Implementation Method 3
The collar is rotatably supported via a plurality of bearing elements arranged between the collar and the at least one support
Data Source
AI summary
An actuator assembly is disclosed herein. The assembly includes a motor shaft; support; harmonic drive connected to the motor shaft that includes an output connected to a drive shaft defining a first sun gear; drive mechanism; and actuator arm. The drive mechanism includes a first gear set and a second gear set. The first gear set has a first carrier including a second sun gear. The first carrier supports a first plurality of planetary gears that engage both the first sun gear and a first ring gear rotationally fixed to the support. The second gear set has a second carrier fixed to the support. The second carrier supports a second plurality of planetary gears that engage both the second sun gear and a second ring gear. The actuator arm is connected to the second ring gear such that the actuator arm is rotationally driven by the motor shaft.