Coaxial Backdrivable Actuator Layout for High-Torque Exoskeletons
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Solution Overview
Problem
Existing wearable robots face challenges with low output torque from electric motors, which are typically paired with high-reduction gearboxes that compromise efficiency and backdrivability, affecting overall performance and user comfort.
Innovation Solution
A backdrivable actuator with a coaxial input-output layout and a two-stage timing belt transmission system, combining a high-torque motor with a low-ratio transmission, providing high torque, low weight, and efficient operation without compromising backdrivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high-reduction gearboxes are used to increase output torque, then torque capability is improved, but efficiency and backdrivability deteriorate
Solution Approach 1:
The patent implements a nested configuration where the input pulley is positioned inside the output pulley, creating a compact coaxial arrangement. This nesting allows the transmission system to achieve high torque multiplication through the timing belt mechanism while maintaining efficiency by minimizing the number of transmission stages and reducing mechanical losses associated with multi-stage gearboxes.
Solution Approach 2:
The patent replaces traditional mechanical gearbox systems (harmonic gears, planetary gearboxes) with a timing belt transmission system. This substitution eliminates the need for complex gear mechanisms, reducing mechanical losses and improving backdrivability while maintaining the ability to achieve high torque output through the belt-pulley mechanism.
2Force
If high-reduction gearboxes are used to increase output torque, then torque capability is improved, but backdrivability deteriorates
Solution Approach 1:
The patent replaces traditional mechanical gearbox systems with a timing belt transmission system that inherently provides better backdrivability. The belt mechanism allows for smoother bidirectional operation and easier manual override compared to gear-based systems, while still achieving the required torque multiplication for exoskeleton applications.
Solution Approach 2:
The patent extracts the essential function of torque multiplication from complex gearbox mechanisms and implements it through a simplified timing belt system. By removing the intermediate gear stages, the system maintains torque capability while significantly improving backdrivability and ease of operation.
3Loss of energy
If traditional gearbox systems are replaced, then efficiency and backdrivability are improved, but device complexity may increase
Solution Approach 1:
The nested coaxial arrangement of input and output pulleys creates a compact transmission system that integrates multiple functions within a small footprint. This configuration reduces the overall complexity by eliminating the need for separate housing, mounting brackets, and alignment mechanisms required by traditional gearbox systems.
Solution Approach 2:
The timing belt transmission system serves multiple functions simultaneously: it provides torque multiplication, maintains efficient energy transmission, enables backdrivability, and offers a compact form factor. This multi-functionality reduces the need for additional components and simplifies the overall transmission system design.
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 actuator achieves high torque, low weight, and improved human-machine interaction, enhancing user comfort and efficiency while maintaining high bandwidth and backdrivability, potentially reducing manufacturing costs and improving human-robot interaction.
Implementation Method 1
two-stage timing belt transmission system
Implementation Method 2
timing belt transmission system
Implementation Method 3
high-torque motor
Data Source
AI summary
The invention relates to an actuator, optionally for an exoskeleton, comprising a motor for providing speed and force to a reduction assembly; a two-stage reduction assembly comprising an input pulley and an output pulley; the two-stage reduction assembly configured to perform a speed reduction and a force increment; where the motor, the input pulley and the output pulley are coaxially located and/or in the same plane and/or inside each other within the actuator.