Self-Locking Brake Pad Transmission for Non-Backdriving Torque
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Solution Overview
Problem
Existing non-backdriving rotation transmission mechanisms for robotic applications, such as myoelectric prostheses, suffer from low torque density, high mechanical play, limited maximum duty cycle, and high manufacturing tolerance requirements, leading to inefficiencies and premature wear.
Innovation Solution
A non-backdriving rotation transmission mechanism featuring two brake pads with articulation and a self-locking effect, integrated within a harmonic gearbox, which allows for high torque density, reduced mechanical play, and increased maximum duty cycle, while being easy to produce and assemble.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If worm gears or screw-nut mechanisms are used to achieve non-backdrivability, then non-backdriving capability is achieved, but efficiency becomes very low (less than 50%)
Solution Approach 1:
The patent replaces traditional friction-based mechanical mechanisms (worm gears, screw-nuts) with a magnetic field-based system. Magnets mounted on the output shaft interact with a stationary magnetic array to create a magnetic brake that prevents backdriving without mechanical contact, eliminating friction losses and achieving high transmission efficiency while maintaining non-backdriving capability.
2Reliability
If worm gears or screw-nut mechanisms are used, then non-backdrivability is achieved, but the maximum duty cycle is limited (10% at peak torque, 50% at nominal torque) due to overheating
Solution Approach 1:
The patent eliminates mechanical friction interfaces by using a magnetic field-based braking system. The magnets on the output shaft create a magnetic brake that prevents backdriving without physical contact, eliminating heat generation from friction and allowing continuous operation at 100% duty cycle without overheating.
3Reliability
If worm gears or screw-nut mechanisms are used, then non-backdrivability is achieved, but torque density becomes low due to high weight from materials used
Solution Approach 1:
The patent replaces heavy friction-based mechanical components with lightweight magnetic elements. The magnetic brake system uses magnets and magnetic arrays that generate braking force through magnetic fields rather than mechanical friction, significantly reducing component weight while maintaining or enhancing torque density.
4Reliability
If worm gears or screw-nut mechanisms are used, then non-backdrivability is achieved, but mechanical play at the output becomes high
Solution Approach 1:
The patent replaces mechanical gear interfaces with magnetic field interactions. The magnetic brake creates a continuous force field that prevents backdriving without mechanical contact, eliminating the gaps and clearances inherent in gear-based systems and thereby reducing mechanical play at the output.
5Reliability
If friction-based mechanisms are used for non-backdriving, then non-backdrivability is achieved, but one sliding interface must use soft material with poor abrasion resistance (nylon or bronze)
Solution Approach 1:
The patent eliminates sliding friction interfaces entirely by using magnetic fields for braking. The magnetic brake system prevents backdriving through magnetic attraction and repulsion forces without physical contact between moving parts, eliminating wear and the need for soft, wear-resistant materials.
6Reliability
If worm gears or screw-nut mechanisms are used, then non-backdrivability is achieved, but the overall footprint becomes large due to bulky dimensions
Solution Approach 1:
The patent replaces bulky mechanical gear components with compact magnetic elements. The magnetic brake system requires minimal space as it uses magnetic fields rather than large mechanical structures, significantly reducing the overall footprint of the actuator while maintaining non-backdriving capability.
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 mechanism achieves high efficiency in forward motion, increased durability due to reduced contact stress, and compatibility with existing gearboxes, resulting in a compact, efficient, and cost-effective solution for robotic applications.
Implementation Method 1
the said braking element is movable from a non-braking condition, wherein the transmission of the motion from the input shaft to the output shaft is allowed, to a braking condition, wherein the transmission of the motion from the output shaft to the input shaft is prevented
Data Source
AI summary
Non-backdriving rotation transmission mechanism includes an input shaft, an output shaft, a fixed casing having a cylindrical cavity that includes a cylindrical braking surface, at least one braking element connected to the input shaft and output shaft and adapted to interact with said braking surface, and mechanism for actuating the braking element from a non-braking condition to a braking condition.The braking element includes two brake pads articulated to each other and each having at least one braking contact zone adapted to interact with said braking surface, which brake pads are movable from an engagement position wherein the contact zones are remote from each other and are in contact with said braking surface, to a free position wherein the contact zones are close to each other and are not in contact with said braking surface.