magnetic gears and their structural limitations · national aeronautics and space administration...
TRANSCRIPT
![Page 1: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/1.jpg)
Magnetic Gears and Their
Structural Limitations
Thomas
Tallerico
Justin
Scheidler
Zachary
Cameron
National Aeronautics and Space Administration
www.nasa.gov
SLAMS 2019
September 9-13, 2019
Armstrong Flight Center
NASA Glenn Research Center
Materials and Structures Division
Rotating and Drive Systems Branch
Design of a Magnetic Gear for NASA's Vertical Lift Quadrotor Concept Vehicle 1
https://ntrs.nasa.gov/search.jsp?R=20190032274 2020-08-03T23:08:19+00:00Z
![Page 2: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/2.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 2
• Background and Motivation
• Concentric Magnetic Gears
• Enabling Design Principles
• Efficiency
• Lightweight
• Modulator Structure
• Conclusions
Outline
![Page 3: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/3.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3
Background & Motivation
• NASA set goals for aircraft efficiency,
emissions, reliability, and noise
• Parallel large & small aircraft development
• Economic benefit of alternative propulsion
• Electrified aircraft propulsion is a key enabler
• Most concepts use direct drive
• Geared drives are almost always mass
optimal
Direct drive
motorfan
+ Simpler
− Non-optimal
motor and/or fan
Geared drive
motor
fangearbox
+ Optimized motor & fan
+ Enables cross shafting
− More complex
− Potentially less reliable
![Page 4: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/4.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 4
Background & Motivation
Pros
+ High / very high
torque/mass
(specific torque)
+ High / very high
efficiency
+ Mature technology
Mechanical gearing Magnetic gearing
Pros
+ Non-contact
+ No lubrication
+ Low maintenance
+ Easily integrated in
electric machines
+ Potentially low vibration
Cons
− Unknown limits on specific
torque & efficiency
− Magnet temperature limit
− Individual magnet interaction
weaker than 1 gear tooth pair− Routine & costly maintenance
− Strong tonal vibration & cabin noise
Cons
− Contact-related wear &
failure
− Requires lubrication
system(s)
![Page 5: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/5.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 5
Background & Motivation
Phase I2017
• How do they work? (PT-1)
• Can they be lightweight? (PT-2)
Phase II2018-2019
• Can they be efficient? (PT-3)
• Can they be efficient and light weight? (PT-4)
Phase III2019-2020
• How to pair them with motors?
• Can they be reliable?
PT-1
20 Nm/kg
PT-2
45 Nm/kg
PT-3 >98%
Efficient
PT-4
>98.5%
>55 Nm/kg
![Page 6: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/6.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 6
• Rule of thumb:
Magnetic fields with matching spatial
harmonic order can couple to transmit
torque
• Ring and Sun gear have different pole
counts
• Produce different spatial harmonic
• Modulator “modulates” the flux of each
rotor so that that have matching spatial
harmonic order in the airgaps
Concentric Magnetic Gears
![Page 7: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/7.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 7
cos 𝜃 ∗ cos 𝛼 =1
2(cos 𝜃 + 𝛼 + cos 𝜃 − 𝛼 )
𝐵𝑟𝑠 ∗ 𝑢𝑚 = 𝑢𝑎𝑣𝑔 ∗ 𝐹 ∗ cos(𝑃𝑆 ∗ 𝜃 + 𝛼 )+𝐹 ∗ 𝑢
2cos 𝑸 + 𝑷𝑺 𝜃 + 𝑃𝑆 ∗ 𝛼 + 𝑄 ∗ 𝛽 +
𝐹 ∗ 𝑢
2cos 𝑸 − 𝑷𝑺 𝜃 − 𝑃𝑆 ∗ 𝛼 + 𝑄 ∗ 𝛽 )
Concentric Magnetic Gears
𝐵𝑟𝑠 = 𝐹 ∗ cos(𝑷𝑺 ∗ 𝜃 + 𝛼 )
Number of Sun Gear Pole Pairs
𝑢 = 𝑢𝑎𝑣𝑔 + 𝑢𝑚 ∗ cos(𝑸 ∗ 𝜃 + 𝛽 )
Number of Pole Pieces
𝑷𝑹 = 𝑸 ± 𝑷𝑺 𝑜𝑟 𝑸 = 𝑷𝑹 ± 𝑷𝑺
Number of Ring Gear Pole Pairs
![Page 8: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/8.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 8
Mechanical
planetary
gear
Analogous concentric
magnetic gear
Concentric Magnetic Gears
Output Q Selection Gear Ratio
Ring Gear
PR-PS𝑃𝑅
𝑃𝑆PR+PS
Modulator
PR-PS𝑄
𝑃𝑆=𝑃𝑅
𝑃𝑆− 1
PR+PS𝑸
𝑷𝑺=𝑷𝑹
𝑷𝑺+ 𝟏
Gear Ratio
![Page 9: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/9.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 9
Efficient Magnetic Gears
• Main loss source = eddy currents
• Time varying magnetic fields produce electrical fields:
𝛻 × 𝐸 = −𝜕𝐵
𝜕𝑡
• Electrical fields drive currents:
𝐼 =𝑉
𝑅
• Currents produce heat:
𝑄 = 𝑅𝐼2 =𝑉2
𝑅
Enabling Design Principles
![Page 10: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/10.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 10
1. Use non-conductive (non-
metallic) Structures
• Plastics
• Composites
• Ceramics ($$)
2. Laminate Electrical
Components
• Laminated Electrical Steel
• Laminated Magnets
• Increases effective (Bulk)
resistivity
Minimizing Eddy Currents
Enabling Design Principles
52 mm
1 mm
![Page 11: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/11.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 11
1. Use non-conductive (non-
metallic) Structures
• Plastics
• Composites
• Ceramics ($$)
2. Laminate Electrical
Components
• Laminated Electrical Steel
• Laminated Magnets
• Increases effective (Bulk)
resistivity
Minimizing Eddy Currents
Enabling Design Principles
![Page 12: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/12.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 12
Light Weight Magnetic Gear
Enabling Design Principles
• Small Modulator Thicknesses
• There is an optimum Modulator
Thickness Electromagnetically
• Typically ~1.5 mm
• Small Airgaps
• ~100 Nm/Kg improvement per
1 mm airgap reduction
• Outer Airgap more important
Limit on both = Modulator Structure
![Page 13: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/13.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 13
Modulator Structural Problem
• Modulator sees high
electromagnetic forces
• Carries output torque of the gear
• Radial forces from Magnets
• Modulator “nested” between
airgaps
• Limits Structure
• Limits Allowable Deformation
• Pole Pieces cannot transmit
shear load
Modulator Structure
![Page 14: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/14.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 14
Traditional Solution
• Modulator Bridges
• Gives modulator hoop strength
• Results in torque reduction
• Creates Flux Leakage Path
• Reduces Modulation
Modulator Structure
![Page 15: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/15.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 15
PT-2 and PT-3 Structures
• Laminated Electrical Steel Pole
Pieces
• Unidirectional Carbon Fiber
Support Posts
• 3D Printed End Caps
• Nylon + Carbon Fiber Chop
• Reinforced with continuous fiber
Modulator Structure
Modulator Cap
Steel Pole Pieces
Support Posts
![Page 16: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/16.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 16
Issue With Our Pole Pieces
• Epoxy bond between layers
very weak
• Resultant from small area
• Defects that are small in a motor
lamstack are large
• Softens at 60C
Modulator Structure
![Page 17: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/17.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 17
PT-2 and PT-3 Failure
• Both failed at ~ 4000 rpm input
• Both not designed for thermal failure
at 60 C
• Theory:
• Thermal failure of pole piece glue
bond
• Single pole piece cuts into
modulator support structure
• Makes space allows failure to
propagate
Modulator Structure
![Page 18: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/18.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 18
Current Fixes
1. Add Carbon Fiber Hoop
• Plan for PT-4
• Used in PT-3 Rebuild
2. Stack and Bond Internally
3. Caged Modulator Structure
4. Modulator Bridges
• If Enables Smaller Airgaps
Modulator Structure
![Page 19: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/19.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 19
• Magnetic Gears are a potential alternative to mechanical
gears for aerospace applications
• Reliability benefits over mechanical gears
• Able to achieve 99% efficiency
• Need to be light weighted further
• Modulator structural improvements are the obvious path
to improve magnetic gear specific torque
Conclusions
![Page 20: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/20.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 20
• Build and Test PT-4
• Magnetically geared motors
• How best to share magnetic and structural components
between a motor and a magnetic gear?
• Space Applications
• Low lubrication requirements
• Bearings still need lubrication
• Over load protection
• Robotic arms
Future Work
![Page 21: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/21.jpg)
National Aeronautics and Space Administration Magnetic Gearing Research at NASA 21
Acknowledgements
• NASA Revolutionary Vertical Lift Technology (RVLT) Project
• NASA Internal Research & Development (IRAD) Project
![Page 22: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/22.jpg)
National Aeronautics and Space Administration Magnetic Gearing Research at NASA 22Your Title Here 22
QUESTIONS ?
![Page 23: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/23.jpg)
National Aeronautics and Space Administration Magnetic Gearing Research at NASA 23Your Title Here 23
![Page 24: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/24.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 24
Flux Modulation Example:
10 Pole Pair Ring Gear Only
Concentric Magnetic Gears
![Page 25: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/25.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 25
Flux Modulation Example:
Add 11 Pole Piece Modulator
𝑃𝑆 = 𝑄 − 𝑃𝑅 = 11 − 10 = 1
Concentric Magnetic Gears
![Page 26: Magnetic Gears and Their Structural Limitations · National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 3 Background & Motivation • NASA](https://reader033.vdocuments.net/reader033/viewer/2022053019/5f28992696eec837ce69e424/html5/thumbnails/26.jpg)
National Aeronautics and Space Administration Magnetic Gears and Their Structural Limitations 26
Efficient Magnetic Gears
• PT-3 >98% Efficient
• Plastic Structure
• 1 mm Magnet Laminations
• 0.15 mm Laminated Iron Cobalt
electrical steel Pole Pieces
Enabling Design Principles