Edm E Drive Orlando Conf Mar2009 V13

EDM Resources Inc.
Harmonic Drive Motor-Generator Technology

A New Approach To:
High Torque, Variable, Low Speed
Motor Generator Technology

E. Davison PhD. PEng.
Orlando March, 2009

EDM Resources Inc. ©
2009

Overview / Outline

1. Introduction Overview / Outline
2. Harmonic Motor Technology Primer
3. EDM Resources Harmonic Drive Motor
4. Applications & Benefits
5. Summary
6. Q&A

WARP, high torque, High Efficiency High Torque Motor, Navy, electrification, aircraft flap actuator, replace hydraulics, wheel motor, nose motor,
harmonic drive motor, harmonic motor, davison, patent

Harmonic Drive Motor-Generator Technology 2

2009

1. Introduction

• EDM Resources Inc. Background
 Based in Moffat Ontario Canada since June 1998
 Sole assignee of related patents
 Contact: edmresourcesca@aol.com

• E. Davison PhD, PEng
 President and founder of EDM Resources
 Sole inventor of related patents
 Developer of innovative high torque density motor-generator
technology since 1965



2009

• Harmonic Drive Motor-Generator Technology
 Combination of harmonic gear and reluctance motor technologies
 Major claimed benefits of HDMG technology:
 High torque & power density
 Lower cost - reduced parts count
 Rugged construction, high reliability (stationary rotor)
 Independent control of: torque, speed & position
 Tolerant of repeated impact torque
 High torque2 / low rotational inertia ratio
 Four quadrant operation, plus regenerative braking (without relays)



2009

• Harmonic Gears
 Developed by C.W. Musser in 1950’s
 Harmonic Gears provide unique advantages such as:
 Compact & light weight
 High Reduction Ratio in a Single Stage (30:1 to 300:1)
 High Torque Capability (up to 50% of teeth in mesh)
 High resistance to repeated impact torque
 Low tooth contact pressure & wear
 Tooth contact is surface as opposed to line contact (no Hertzian stress)
 Zero Backlash



EDM Resources Inc.
• Harmonic Gear vs Other Gear Types
Harmonic Epi- Herring Single Helical
Characteristic Gear cyclic bone Worm Worm
1 Speed Ratio 100 97 96 108 100
2 Efficiency (%) 82 85 85 40 78
3 # of Gears 2 13 4 2 4
4 # of Bearings 2 17 6 6 6
5 Pitch line velocity (ft/min) 18 1,500 1,500 1,500 1,500
6 Tooth sliding velocity (ft/min) 28 2,500 2,500 1,500 2,500
7 Tooth contact pressure (psi) 605 50,000 50,000 5,000 50,000
8 Teeth in contact (%) 50 7 5 2 3
9 Safety factor 36 3 2 2 2
10 Height (in) 6 13 14 23 16
11 Length (in) 6 15 20 19 17
12 Width (in) 6 13 10 14 10
3
13 Cubic volume (in ) 216 2,500 2,800 6,100 2,700
14 Weight (lb) 30 246 280 230 205
15 Tooth contact Surface Line Line Line Line
16 Quiet operation Yes No Yes Yes Yes
17 Balanced forces
harmonic drive motor, harmonic motor, davison, patent Yes Yes No No No
Ref “Gear Design and Application by N. Chironis, ISBN 0070107874 ”


EDM Resources Inc.
• Harmonic Gears Principle of Operation
 2 closely spaced concentric splined interfacing gears with the
number of teeth on the inner gear being fewer in number than
the outer gear
 An elliptical cam wave generator causes a fraction of the teeth
to mesh at 2 opposite poles with up to half of the teeth being in
contact
 Reduction ratio = (# flex spline teeth - # circular spline teeth)
# flex spline teeth
Reduction Ratio = (200 – 202) = 100:1 Circular Spline Gear
200 Flexispline Gear
(Variable Between 30:1 to 300:1) Elliptical Cam
Wave Generator

Motor Shaft
Input

Image courtesy of wikipedia.org Image courtesy of Harmonic Drive LLC


EDM Resources Inc.

• Switched Reluctance Motor Principle of Operation
 SRM invented by Davidson (Scotland, 1838)
 Rotation & torque achieved by energizing the stator coils sequentially
 Rotor position determines which coils are
energized (commutation is critical)
 Field & rotor rotate in opposite directions
 # of rotor poles must be different from
# of stator poles to avoid starting problems
 # of working strokes/rev = 24 Controller
&
(for 8 stator poles & 6 rotor poles) Commutator

8/6 4 phase SRM
Image courtesy of Switched Reluctance
Motor Drives By Ramu Krishnan



2009


• Switched Reluctance Motor Principle of Operation
 Benefits
 Good stall endurance
 Fault tolerant & reliable
 High torque to inertia ratio (acceleration)
 Lower cost due to robust construction
& ease of manufacture
 High torque density
 Ability to withstand higher Typical SRM Torque-Speed Curve
temperature environment (Harmonic Drive Motor-Generator Similar)

Torque

Speed


2009


• EDM Resources Harmonic Drive Motor
 Covered by US (7,453,176) and WPO (WO/2004/025815) patents
 Sometimes referred to as “High Efficiency High Torque WARP Motor”
 Fundamental difference between EDM HDMG and other
electrical motors:
 Only motor technology exploiting the large radial
force which is 20+ times that of the tangential torque force

“For example, an 8/6 SRM with a ratio of radius to
air gap equaling 100, the ratio between the radial and
tangential forces is found to be 26.19; therefore, the
radial force is always multiple times that of the
tangential force in the SRM and the same can be said
for other electrical machines.”
(ref Krishnan: Switched Reluctance Motor Drives: Modeling, Simulation, Analysis, Design, and
Applications ISBN 0-8493-0838-0, CRC Press 2001, p356actuator, replace hydraulics, wheel motor, nose motor,
WARP, high torque, High Efficiency High Torque Motor, Navy, electrification, aircraft flap section 7.2.1.1 )


2009


 Major differences between EDM HDMG and other electric motors
 Traditional rotor is replaced by a stationary (non rotating) element
 Stator windings occupy space normally occupied by traditional rotor
 No rotor = no rotor inertia or windage
 Unipolar DC pulse excitation – minimal flux reversal and iron losses
 Independent concurrent control of: torque, speed and position



2009


• Motor Construction (experimental prototype)

Flexispline (Rotatively Fixed
with internal teeth)

Stator Windings

Output spline gear/flange
Bearings (2)
(with external teeth)


2009


• Motor Construction – Single Output (two alternatives)
Flexispline- Teeth on inside
Output gear rotation direction - opposite to field rotation

Windings Bearings (2) Output gear
(rotates)

Flexispline- Teeth on outside
Output gear rotation direction - same as field rotation


2009


• Motor Construction - Continuous Through Shaft
 Applications: ship propulsion, aircraft wing flap actuators, electric
power assist steering
Output gear (rotates)

Continuous through shaft
construction or linear
screw
Motors coupled in series
for minimized packaging
with high torque density
or distributed high torque



2009

• Motor Forces
 Force is generated by rotating electromagnetic field
 Rotational sequence: A  B  C

Field Rotation

A C

Flexispline Gear Fixed (teeth on inside)
Circular Spline Gear Rotates (teeth on

B
outside)


2009


• Principle of Operation – Switched Reluctance
Version (4 phase – 2 pole) Flexispline
 Two energized coils in series
(but of opposite polarity)
 8 stator coils in total
 Flux flow does not rotate
but is switched to next coil
in sequence Stator
Core
 Flux return path through
flexispline
 # of equivalent rotor
poles = # of stator poles,
therefore # of working strokes
/ output rev = 16 x N
(N = harmonic gear ratio)


2009


• Principle of Operation
 Simulation of flux flow
distribution
 No outside back up iron
ring or laminations
 Thick flexispline cup
 Magnetic flux is confined
mainly to local flexispline
quadrant (lower iron losses)
 Excitation unipolar DC pulses
(no flux reversal – reduced iron
losses)



2009

• Harmonic Motor – Potential For Torque Production
A Bg2
½” ≈
Radial force Fr =
2 μo
A = Air Gap (4 x ½ = 2in2)
4”
Bg = Air Gap Flux Density
Fr
μo = 4 ∏ x10-7 (permeability)
Fr
4 Fr = 250 lbs/in2 x A (for Bg ≈ 2.1Tesla)
Fr
4

Total Radial Force Ftr = 3/2 Fr x 2 x A
= 3 Fr x A = 3 x 250 x 2 Ftr
≈ 1500 lbs Meshing
Gear
Torque Translation Model Teeth
α
Fr Ftr = Total Radial Force α To
Fr

4
4

To = Output Torque
Fr
R = Torque Radius (4”)
α = Gear Tooth Angle To = Ki x N x Ftr x R
8”
Example Core torque, High Efficiency High Torque Motor, Navy, electrification, aircraft flapGear Ratio 100:1wheel motor, nose x 100 x 1500 x 4
WARP, high Lamination Stack
N = Harmonic actuator, replace hydraulics, = Ki motor,
Ki = Mitigating Factors (K1...Kn) = 600,000 x Ki (lbs-in)


EDM Resources Inc.

• S.R. Motor Controls Adaptable To Harmonic
Motors



EDM Resources Inc.
• S.R. Motor Controls Adaptable To Harmonic
Motors



2009


• Experimental Prototype Motor
Output gear rotates
Windings stationary
Flexispline
(rotatively fixed &
electromagnetically
distorted to engage
rotor output gear)

Internal
gear teeth



2009


 Experimental Motor Stator Windings



2009


 Experimental Prototype Motor gear teeth

Rotor teeth not engaged – rotor free
(Can be clutched & de-clutched) wheeling

Rotor teeth engaged – rotor locked
(Very high locking torque)



2009


• EDM Resources Harmonic Drive Motor Video



2009

4. Applications

• EDM Resources Harmonic Drive Motor Applications
 Navy electrification – ship propulsion & electrical energy generation
system
 Multi-screw propulsion
(with continuous through shaft motors)
 Benefits:
– Load diversification
» Some units produce torque, some generate electrical energy,
or all units produce propulsion torque,
or all units generate electrical energy
» Avoids peak load design for separate generator and propulsion systems
» Redundant system with high reliability
– Ability to use super conducting stator windings for increased efficiency
– Reduces transmission gear requirements
– Reduced cost, simplified maintenance & reduction in highly trained personnel
 Replace hydraulic & pneumatic actuators


EDM Resources Inc.
4. Applications

 Military applications
 Actuators (turret, fire control)
 Traction (wheel motors)
 Winches
 Power Steering

 Benefits
 High controllability
 Replaces hydraulics
 High reliability (robust)
Traction System
 Lower weight Actuation
 Low maintenance
 Resistant to impact
 Facilitates liquid cooling


EDM Resources Inc.
4. Applications
 Aerospace applications
 Actuators
– Wing flaps, landing gear
 Aircraft
– In nose wheel tow motor (for reducing fuel consumption during taxiing)
 Robotics
 Satellites
Conceptual design for applying
 Benefits harmonic drive motors to aircraft
 High torque density leading flap actuator to replace
 High distributed torque hydraulic actuators
 Lower weight & inertia Single output HDMG
Multiple through-shaft
 High precision (30:1 to 300:1) HDMG motors in
series
 Replace hydraulics
 Redundant system
 High reliability
 Low maintenance
 Fail safe operation
 Resistant to impact
 Facilitates liquid cooling


EDM Resources Inc.
4. Applications

 Wind turbines
 Low weight integral gear generator
 Low speed propulsion drives
 Air ship propulsion
 Benefits
 High reliability
 High torque at low speeds
 Low weight / reduced mounting
column requirements
 Low maintenance
 Compact
 Reduces transmission
gear requirements
 Rotor can free-wheel
or be locked



EDM Resources Inc.
4. Applications

 Automotive Applications - Continuous through shaft HDMG motor
 Electric power assist steering (pinion, column, rack mounting)
 Sliding door & lift gate actuators

 Benefits
 High torque density – enabler for heavy truck EPAS
Column
 Programmable “feel”, speed sensitive variable assist
Mount
 High reliability & fail safe operation
 Low cost
 Minimal package space
 Replaces hydraulics
 Low weight Continuous through shaft HDMG motor
 Low maintenance
Integrated into steering system

Rack Mount



2009

5. Summary
• Summary
 EDM Resources harmonic drive motor generator:
 U.S. & WPO patents
 Only known motor technology that exploits the large radial force which is 20+ times
that of the tangential torque force and an integral harmonic gear
 Working prototype – proof of concept
 Benefits:
 Lower cost construction (SRM, fewer components count)
 Multi configuration (single output shaft or continuous through shaft)
 Integral harmonic gearing with high single stage reduction (30:1 to 300:1)
 Independent concurrent control of: torque, speed and position
 High reliability (fewer moving parts, up to 50% of gear teeth in mesh)
 Enabler for:
 Electrification for: military, aerospace, robotics, automotive, machine tools
 Replacing hydraulic or pneumatic actuators
 Cost & weight reduction vs hydraulics & other motor-gear systems


EDM Resources Inc.
6. Questions

Questions?



Edm E Drive Orlando Conf Mar2009 V13

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