Hollow-Shaft Linear Motor With Halbach Array for High Power Density
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Solution Overview
Problem
Conventional linear motors have low power-to-weight and power-to-size ratios, are difficult to manufacture, and have complex electrical connections, making them unsuitable for applications requiring high reliability and efficiency, such as in aircraft components and industrial robot arms.
Innovation Solution
A linear motor design featuring a stator with a disc-shaped electromagnet array and a hollow actuation shaft with a permanent magnet arrangement, utilizing a Halbach magnet array and ferromagnetic coil supports for efficient magnetic coupling, along with dielectric potting to reduce power losses and simplify electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional linear motors use solid shafts with stacked magnetic segments and tubular coil supports, then the motor structure is compact and reliable, but the power to weight ratio is low
Solution Approach 1:
The patent inverts the conventional design by making the actuation shaft hollow instead of solid, and placing the permanent magnet arrangement inside the hollow shaft rather than on the outside. This inversion allows the magnetic field to be generated more efficiently within the shaft, increasing the power to weight ratio while maintaining structural reliability through the hollow tube design.
Solution Approach 2:
The patent transitions from a conventional radial magnetic field arrangement to an axial magnetic field arrangement by placing permanent magnets on the actuation shaft that interact with electromagnets in the stator. This dimensional change in magnetic field orientation improves the power density and power to weight ratio of the motor.
2Ease of operation
If stators are made of stacked ferromagnetic discs with coils mounted between them, then the motor can achieve linear actuation, but manufacturing and assembly are difficult
Solution Approach 1:
The stator is segmented into multiple disc-shaped electromagnet assemblies that can be manufactured independently and then stacked together. Each disc contains coils mounted on ferromagnetic supports, and these modular units are assembled by stacking them axially with spacing elements, significantly simplifying manufacturing and assembly compared to conventional integrated stator designs.
3Volume of moving object
If coils are mounted between stacked stator discs, then the motor structure is compact, but electrical connection to the drive is complex
Solution Approach 1:
The ferromagnetic coil supports serve multiple functions: they provide structural support for the coils, act as electrical connection carriers with integrated connection elements, and function as magnetic circuit components. This multi-functionality simplifies the electrical connection system while maintaining motor compactness, as the connection elements are built into the supports rather than being separate components.
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 design achieves a high power-to-weight and power-to-size ratio, is economical to produce, and provides accurate, easy-to-control actuation with a long travel range, suitable for dynamic components.
Implementation Method 1
The stator electromagnetic array comprises a plurality of electromagnets to generate a magnetic field that in conjunction with the magnetic field of the permanent magnet arrangement generates an electromotive force between the stator and actuation shaft having a component in the axial direction (A) to drive the actuation shaft relative to the stator
Implementation Method 2
The electromagnet array comprises a plurality of substantially disc shaped electromagnets stacked in said axial direction (A), each electromagnet comprising a coil support and at least one coil mounted within an axial recess of the coil support
Implementation Method 3
the permanent magnet arrangement comprises a plurality of magnetic pole segments forming a Halbach magnet array
Implementation Method 4
a dielectric material covers the coil within the axial recess, in the form of a dielectric potting material, a dielectric resin, or an injected or molded dielectric polymer
Data Source
Figure 1a
Figure 1b~1d
Figure 2~2b
AI summary
An electrical linear motor comprising a stator (4) and an actuation shaft (6) movable in a linear axial direction (A) with respect to the stator, the stator comprising a casing (8), an electromagnet array (10) mounted in the casing (8), the electromagnet array (10) comprising a central orifice extending in the linear axial direction (A) within which the actuation shaft extends, the actuation shaft comprising a permanent magnet arrangement (16) comprising a plurality of magnetic pole segments, the electromagnetic array (10) comprising a plurality of electromagnets (11) to generate a magnetic field that in conjunction with the magnetic field of the permanent magnet arrangement generates an electromotive force between the stator and actuation shaft having a component in the axial direction (A) to drive the actuation shaft relative to the stator).