Split-Tooth Flux-Reversal Motor for Angle-Independent Radial Force

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Solution Overview

Problem

Existing bearingless motors for extracorporeal blood pumps face challenges such as rotor losses due to slip, high ohmic losses, and nonlinear radial electromagnetic forces, which can damage blood cells and complicate position control, especially in applications requiring precise torque and force control.

Innovation Solution

A bearingless split-tooth flux-reversal slice motor topology is introduced, featuring magnets attached to the stator teeth, allowing independent control of flux and torque generation, which simplifies suspension control and achieves force and torque specifications suitable for blood pumps by utilizing a magnet-biased reluctance actuator principle and flux-reversal operating principle.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If induction motors are used for bearingless blood pumps, then the motor can operate without permanent magnets, but rotor losses due to slip occur which can damage blood cells

Engineering Contradiction:

Improvemotor operation capabilityVSAvoidrotor losses due to slip

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the induction motor's slip-based torque generation with a synchronous reluctance motor mechanism that uses magnetic anisotropy and flux barriers to produce torque without slip, eliminating the harmful rotor losses while maintaining bearingless operation capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If switched/synchronous reluctance motors are used, then rotor losses due to slip are eliminated, but torque constant is reduced

Engineering Contradiction:

Improverotor lossesVSAvoidtorque constant

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The patent employs composite magnetic circuit structures combining high-permeability magnetic materials with flux barrier regions, creating a composite rotor design that enhances magnetic flux distribution and increases torque constant while maintaining the slip-free operation of synchronous reluctance motors

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes key parameters including flux barrier width, pole arc ratio, and magnetization current amplitude to maximize torque constant. By adjusting these parameters, the motor achieves higher torque density without reintroducing slip losses

Inventive Principle:

Principle #35Parameter changes

3Power

If magnets are added to the stator to provide bias flux, then force and torque constant are enhanced, but ohmic losses increase due to continuous current requirement

Engineering Contradiction:

Improveforce and torque constantVSAvoidohmic losses

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent uses periodic switching of stator windings to generate rotating magnetic fields that interact with rotor flux barriers. This periodic excitation replaces continuous DC bias currents, reducing ohmic losses while maintaining enhanced force and torque constants through controlled magnetic flux variation

Inventive Principle:

Principle #19Periodic action

4Reliability

If conventional flux-reversal motor topology is used, then robust rotor and sinusoidal back EMF are achieved, but radial force for bearingless operation is nonlinear with rotor angle

Engineering Contradiction:

Improve rotor robustnessVSAvoidposition control complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the stator into multiple independent phase windings with specific spatial distribution. Each phase generates controlled radial force components that combine to produce linear net radial force, decoupling position control from rotor angle nonlinearity while maintaining robust rotor structure

Inventive Principle:

Principle #1Segmentation

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 motor design provides independent radial force generation along two axes, reducing the complexity of position control and achieving the necessary torque and force specifications for extracorporeal blood pumps while minimizing cogging torque and ohmic losses.

Implementation Method 1

magnets attached to the stator teeth... provide bias flux, which enhances the force and torque constant

Methodology Applied

Scientific EffectMagnetic flux: Magnetic Field

Implementation Method 2

radial electromagnetic force required for position control... force generation is independent of the rotor angle

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 3

drive current through the first coil winding and the second coil winding to levitate the magnet-free rotor... and to rotate the magnet-free rotor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 4

magnet-biased reluctance actuator principle... provides passive magnetic stiffness

Methodology Applied

Scientific EffectMagnetic reluctance: Magnetic Reluctance

Data Source

PatentUS20240195276A1Bearingless Split Teeth Flux Reversal Motor

Publication Date: 2024.06.13 MASSACHUSETTS INST OF TECH

AI summary

A bearingless split tooth flux-reversal motor (FRM) for use with a pump, such as a centrifugal blood pump. In some embodiments, the motor has a magnet-free rotor and a magnetic configuration wherein the force generation is independent of the rotor angle, allowing for simple radial force generation using stator-fixed currents. The motor torque can be generated using commutated two-phase currents.