Axisymmetric Electropermanent Magnet Nested NdFeB Alnico Design
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Solution Overview
Problem
Existing electropermanent magnets (EPMs) face a limitation in miniaturization while maintaining strong magnetic fields, which restricts their application in smaller scales and more complex structures, such as in programmable matter and micro robotic systems, where both small size and strong magnetic field strength are required.
Innovation Solution
The development of an axisymmetric electropermanent magnet design that incorporates a cylindrical Neodymium-Iron-Boron (NdFeB) magnet embedded inside an Aluminum-Nickel-Cobalt (Alnico) magnet, with two steel plates, allows for a high latching force in the on position and a low holding force in the off position, enabling efficient switching and scalability to smaller sizes without compromising magnetic field strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional EPM designs are used, then magnetic field strength can be maintained, but device size cannot be reduced
Solution Approach 1:
The patent embeds the NdFeB permanent magnet inside a hollow cavity of the Alnico magnet, creating a nested configuration where one magnet is positioned within the structural framework of the other. This nesting arrangement maximizes magnetic field density within a compact volume, enabling miniaturization while preserving strong magnetic field strength for actuation forces exceeding 100 microNewtons.
Solution Approach 2:
The patent combines two different permanent magnet materials (NdFeB and Alnico) with complementary magnetic properties into a single composite magnet assembly. The NdFeB provides high coercivity and strong magnetization, while the Alnico contributes to flux guidance and structural integrity. This composite approach enables the magnet to achieve both small size and strong magnetic field output simultaneously.
2Volume of moving object
If magnet size is reduced for miniaturization, then device complexity increases
Solution Approach 1:
The patent merges the functions of two separate magnets into a single integrated axisymmetric assembly where the NdFeB magnet is positioned within the Alnico magnet's hollow cavity. This unified structure eliminates the need for separate mounting mechanisms and external flux shunting components, thereby reducing overall device complexity despite the sophisticated internal configuration.
Solution Approach 2:
The patent employs axisymmetric (cylindrically symmetric) geometry for both the Alnico magnet and the embedded NdFeB magnet. This curved, symmetric design simplifies manufacturing through rotational molding or machining, and naturally guides magnetic flux along symmetric paths, reducing the need for complex external flux management structures.
3Ease of operation
If switching magnetization direction is achieved, then energy consumption increases
Solution Approach 1:
The patent leverages the inherent magnetic properties of the two magnet materials to enable self-switching behavior. The Alnico magnet's lower coercivity allows it to be easily remagnetized by external fields, while the NdFeB magnet's high coercivity provides stable latching. This material contrast enables the magnet assembly to switch states with minimal external energy input, consuming power only during transitions rather than continuously.
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 achieves a significantly higher on/off force ratio compared to conventional EPMs, allowing for efficient operation in smaller form factors while maintaining strong magnetic fields, facilitating applications in micro robotic systems and programmable matter.
Implementation Method 1
a pulse of electric current passing through a coil in a first direction is used to create a magnetic field that flips the direction of magnetization of the switchable permanent magnet
Implementation Method 2
magnetic flux external to the EPM can latch the EPM to an object, such as an object having a ferromagnetic material
Implementation Method 3
The soft magnetic material, which is a magnetically permeable material such as a ferromagnetic material, is used to guide the magnetic flux from the ends of the two permanent magnetics
Data Source
AI summary
Embodiments of the present disclosure relate to methods and systems for switching a magnetic field external to a magnet assembly having two permanent magnets, including a fixed permanent magnet portion and a switching permanent magnet portion, where a switching magnetic field is used to switch the magnetization of the switching permanent magnet portion, but not switch the magnetization of the fixed permanent magnet portion. In this way, the fixed permanent magnet portion has a fixed magnetization, such that the direction of magnetization of the fixed permanent magnet portion remains the same during switching of the magnetization of the switching permanent magnet portion, and the switching permanent magnet portion has a switching magnetization, such that the direction of magnetization of the switching permanent magnet portion is switched during switching of the magnetization of the switching permanent magnet portion.