Spherical Motor Halbach Array Torque Control
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Solution Overview
Problem
Existing spherical motors exhibit non-uniform torque and difficulty in control due to non-sinusoidal air-gap flux and heavy rotating parts, limiting their effectiveness in multi-degree-of-freedom applications.
Innovation Solution
A multi-degree-of-freedom electromagnetic machine featuring a spherical structure with perpendicularly disposed axes of symmetry, coils wound around these axes, a non-magnetic structure, and a Halbach array mounted on the non-magnetic structure, allowing relative rotation and optimizing torque distribution and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a typical spherical motor with orthogonally placed coils and multi-pole magnets is used, then multi-degree-of-freedom motion is achieved in a single assembly, but the torque becomes non-uniform at different positions and the air-gap flux becomes non-sinusoidal
Solution Approach 1:
The patent applies Local Quality by using a Halbach array magnet configuration where the magnetic pole arrangement varies locally around the spherical stator. Specifically, the magnets are arranged with alternating polarities in a pattern that creates a sinusoidal air-gap flux distribution, with different regions of the sphere having different magnetic pole orientations to achieve uniform torque characteristics across all positions and orientations.
Solution Approach 2:
The patent applies Parameter Changes by modifying the magnetic field distribution parameters through the Halbach array configuration. The sinusoidal flux distribution is achieved by carefully controlling the magnetic pole angles and intensities at different locations on the spherical stator, transforming the non-sinusoidal flux characteristic of conventional designs into a sinusoidal one, which directly improves torque uniformity.
2Adaptability or versatility
If conventional spherical motors with multi-pole magnets and steel arrangements are used, then multi-DOF actuation is achieved, but the rotating part becomes relatively heavy
Solution Approach 1:
The patent applies Taking out by removing the heavy permanent magnets from the rotating spherical rotor and replacing them with electromagnetic coils. The magnetic field is now generated electromagnetically rather than through permanent magnets, significantly reducing the weight of the rotating part while maintaining the multi-degree-of-freedom actuation capability through controlled coil energization.
Solution Approach 2:
The patent applies Mechanics substitution by replacing the permanent magnet-based magnetic field generation system with an electromagnetic coil system. This substitution eliminates the need for heavy magnetic materials in the rotating assembly, reducing inertia and weight, while the electromagnetic fields generated by the coils provide the necessary torques for multi-DOF motion control.
3Adaptability or versatility
If existing spherical motors with non-linear torque profiles are used, then multi-degree-of-freedom motion is achieved, but the control becomes difficult and maximum torque is not provided at all positions
Solution Approach 1:
The patent applies Parameter changes by creating a sinusoidal air-gap flux distribution through the Halbach array configuration, which transforms the non-linear torque profile into a linear one. This parameter change in the magnetic field distribution ensures that maximum torque is available at all positions and orientations, and the linear torque characteristics simplify the control algorithms needed for multi-DOF motion.
Solution Approach 2:
The patent applies Homogeneity by achieving uniform torque characteristics across all positions and orientations of the spherical rotor through the Halbach array magnet arrangement. The sinusoidal flux distribution ensures that the torque output is consistent and predictable regardless of the rotor's angular position, making the system easier to control compared to conventional spherical motors with position-dependent torque variations.
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 machine achieves uniform torque and sinusoidal air-gap flux, enhancing control ease and torque output, with improved positional accuracy and reduced errors compared to existing technologies.
Implementation Method 1
The Halbach array is mounted on the non-magnetic structure and includes N-magnets, where N is a multiple of 4
Implementation Method 2
The spherical structure and non-magnetic structure are mounted to allow relative rotation between the non-magnetic structure and the spherical structure
Implementation Method 3
The first coil is wound on the spherical structure about the first axis of symmetry, and the second coil is wound on the spherical structure about the second axis of symmetry
Data Source
AI summary
A multi-degree-of-freedom electromagnetic machine includes a spherical structure, a first coil, a second coil, a non-magnetic structure, and a Halbach array. The spherical structure has a first axis of symmetry, a second axis of symmetry, and a third axis of symmetry, and the first, second, and third axes of symmetry are disposed perpendicular to each other. The first coil is wound on the spherical structure about the first axis of symmetry, and the second coil is wound on the spherical structure about the second axis of symmetry. The non-magnetic structure is spaced apart from, and at least partially surrounds, the spherical structure. The Halbach array is mounted on the non-magnetic structure and includes N-magnets, where N is a multiple of 4. The spherical structure and non-magnetic structure are mounted to allow relative rotation between the non-magnetic structure and the spherical structure.