FEATHER project in JAXA
and
toward future electric aircraft
Akira Nishizawa
Section leader of emission free aircraft section
Innovative Aircraft Systems Research Aircraft Systems Research Team
Next Generation Aeronautical Innovation Hub Center
Japan Aerospace Exploration Agency(JAXA)
Hiroshi Kobayashi(JAXA) and Hiroshi Fujimoto(The Univ. of Tokyo)
2nd On-Demand Mobility and Emerging Aviation Technology Roadmapping Workshop, 8-9 March 2016 Lockheed Martin Global Vision CenterArlington VA1
Outline
1. Future Vision and Issues
2. FEATHER project
3. Toward future electric aircraft
2
1. Future Vision and Issues
1. 1 Future vision
A 19th-Century Vision of the Year 2000
http://publicdomainreview.org/collections/france-in-the-year-2000-1899-1910/
3
1. Future Vision and Issues
1. 2 Problems of Small Aircraft
fee[US$/ASK]]
Ticket fee[US$/ASK
Higher Cost
1.0
Lower Safety
Air Line
Air carrier
Regular fee
0.8
Air taxi & Commuter
Discount fee
General aviation
0.6
10.53
0.4
0.2
2.35
0.34
0.0
1
10
100
No. of seats
Unit ticket fees for domestic flights (in
JAPAN, 2014)
1000
16.57
The fatal accident rate of small aircraft is
about 10X higher than that of large aircraft
Number of fatal accidents per 1 million flight
time (average during 1982-1999 in USA)
Source: NTSB Aviation Accident Database
4
1. Future Vision and Issues
1.3 Major issues and solution
Goal Popularization of
General Aviation
PAV, AirTaxi, ODM
Issues
Reduction of operating cost
Current：3～5X higher than airliner
Reduction of fatal accidents
Current：10X higher than airliner
Solution
Electric
JAXA
aircraft
technologies
utilization
Potential strength of Japanese industries
(electric motor, battery, power device,...)
5
Outline
1. Future Vision and Issues
2. FEATHER project
3. Toward future electric aircraft
6
2. FEATHER Project
2.1 Outline of FEATHER project
Mission
Development of JAXA’s unique electric propulsion systems
FY2012
Design
1.
Multiplexed motor
FY2013
Fabrication
FY2014
Integration and flight test
2.
Regenerative air brake
7
2. FEATHER Project
2.2 Overview of the demonstrator
Original aircraft: Diamond aircraft type HK36TTC-ECO
Monitoring unit
Power lever
Reduction gear
Electric motor
①Multiplexed motor
Display
②Pilot interface
Battery pack
Under wing container
③LiLi-ion battery8
2. FEATHER Project
2.3 Electric propulsion system
Inverter
Reduction
Electric motor
gear
Radiator
Electric propulsion system
9
2. FEATHER Project
Specifications
2.4 Specifications
Wing span
16.33m
Take-off weight at the flight test
800kg
Crew member
1 person
Types of electric motor and inverter
Permanent magnet type synchronous motor
(three-phase) and IGBT inverter
Motor control method
FOC (Field-oriented control)
Maximum total shaft power (at RPM)
60kW (2.5min. at 6586RPM), 63kW(proven at
flight)
Type of power source
Lithium-ion battery (32 cells in series)
System voltage (open circuit at 100%SOC)
and Current
128V, 750A
10
2. FEATHER Project
2.5 Multiplexed electric motor system
e-Genius13)
FEATHER(JAXA)
Electric Waiex12)
Antares20E1)
Efficiency[%]
100
3
95
2.5
90
2
85
1.5
80
1
EV motor(LEAF)
＋：Efficiency
◆：Power density
75
0.5
Aircraft piston engine
70
0
30
4
220mm
3
2
3.75㎏
232mm
inverters
1
40
50
60
70
Maximum output[kW]
80
Characteristics
Compact
Light weight(2.17kW/kg)
High efficiency(95%)
High strength of structure
11
Power density[kW/kg]
Rapid200FC11)
2. FEATHER Project
2.6 Regenerative air brake system(1/4)
Characteristic
features
1. Augmentation of descent rate by only pulling the power lever w/o
conventional air brake
2. No weight penalty based on the field-oriented control method
3. Maximization of the regenerative electricity for variable air speeds
Motor
Inverter
Battery
Power lever
Generator
Rectifier
Capacitor
DC/DC
Conventional
Motor / Generator
Inverter
Battery
Field-oriented control
12
2. FEATHER Project
2.6 Regenerative air brake system(2/4)
Torque command value
T
Motor torque is used as a command value
in field-oriented control method
Constant
Variable
T = CPWRδPL
(0%≤δPL≤100%)
T = CRGNδPL
(-100%≤δPL≤0%)
Power lever
displacement
δPL
RGN
PWR
13
2. FEATHER Project
2.6 Regenerative air brake system(3/4)
Torque
（PWR）
Pitch angle of a blade = constant
The torque command value has to
intersect with counter torque curve
of propeller, otherwise the rotational
number becomes zero or negative.
Maximization of the
regenerative electricity
Counter torque of
Prop.
Rotational
speed
0
Free rotation(NTL)
（RGN）
Torque command value
（corresponding to power lever max）
14
2. FEATHER Project
2.6 Regenerative air brake system(4/4)
Motor/
Generator
Propeller
Pitot tube
Battery
Target Torque
Np
Specially designed power
lever to facilitate the control of
descent rate and regeneration
Inverter
System
control unit displacement
Vair
Regenerative power
Power
lever
Display
Vair is not necessary as the feedback parameter to
maximize the regenerative power in this system.
Block diagram of the regenerative air brake system
15
2. FEATHER Project
2.7 Flight demonstration
16
2. FEATHER Project
2.7 Flight demonstration
70
60
Battery SOC
Motor power,
Pm
Absolute altitude, H
Pm[kW]
Vair[m/s]
Np[rps]
SOC[%]
50
700
600
500
Rotational speed
of prop, Np
40
30
400
Airspeed,
Vair
20
10
300
200
100
0
-10
800
H[m]
Pm[kW], Vair[m/s], Np[rps], SOC[%]
80
0
Take-off
Touch-down
Sim. fail climb
Regenerative
soaring
-20
360
480
600
720
840
960
t[s]
Regenerative descend
w/o airbrake
-100
-200
1080 1200 1320 1440 1560
An example of flight test data
17
2.7 Flight demonstration
0
Airbrake
Descent by using the
conventional airbrake
Pm[kW], dH/dt[m/s]
0
-1
-20
-2
-40
-3
-60
-4
Pm[kW]
-5
Power lever [%]
-80
dH/dt[m/s]
-120
-6
490
Descent by using the
“regenerative airbrake system”
-100
495
500
505
t[s]
510
515
520
Correlation of the power lever
displacement, regenerative power and
consequent descent rate, dH/dt during
descent by using regenerative airbrake
system
18
Power lever[%]
2. FEATHER Project
Outline
1. Future Vision and Issues
2. FEATHER project
3. Toward future electric aircraft
19
3. Toward future electric aircraft
Range Extension
Fuel cell & H2
1000
TOYOTA ‘s ®MIRAI with
2.0kW/kg FC stack.
Range/km
800
High energy density Li-ion battery
600
®Taurus G4
400
High AR wing
Drag reduction (L/D>25)
Hitachi demonstrated
335Wh/kg and 30Ah on
Nov. 2014 and they have
developed by 2020 .
http://www.hitachi.com/New/cnews/month/2014/11/141114.html
200
®Skyhawk172
Simple conversion of petrol to battery(4PAX, L/D<10)
0
0
100
200
300
400
Energy density/Whkgdensity/Whkg-1
500
20
3. Toward future electric aircraft
Automatization
1. Electric propulsion system have a high affinity for automatization.
2. Electric motor have a high response performance.
3. Electric motor can be flexibly arranged on a wing or a fuselage.
Motor
Sensors
Inverter
Computer
Sensing Actuator
Power by wire
Key technology
Collaborative work
Control Algorithm
Alternative S&C
21
Thank you
http://www.aero.jaxa.jp/eng/research/frontier/feather/
http://hflab.k.u-tokyo.ac.jp/index.html
22
23
1. Backgrounds & Objectives
Aeronautical Technology Directorate
In JAXA
LongLong-term research toward
zerozero-emission aircraft
Electric and hybrid
propulsion system for
aircraft
1. FEATHER project
2. Concept study of fuel
cell–gas turbine hybrid
aircraft
collaborative work
24
1. Backgrounds & Objectives
Target and mission of FEATHER
Small airplane for
FEATHER
Mission of FEATHER project
To get flight permission from JCAB as the
first case of electric manned flight in Japan
Development of JAXA’s unique electric
propulsion system
Flight validation of the new functions and
system performance
http://www.aero.jaxa.jp/publication/pamphlets/pdf/apg2012‐kouen03.pdf
25
1. Backgrounds & Objectives
Mile stones
2012-2013
June
Start
2014
July
November
March
2015
February
Complete of electric Integration Approval for
flight test
propulsion system
Approval for
flight test
Final flight
Maiden flight
FY2012
Design
FY2013
Fabrication
FY2014 Integration and flight test
120～150km/h
～20min.
～5min.
～0.5min. ～
10m
600ｍ Runway
Jump test
～600m
～
80m
2000ｍ Runway
Jump test
2700ｍ Runway
Short traffic pattern flight test
26
2. Systems
A) Electric motor-glider system
A1)
Electric propulsion system
A1-1）Driving system
Multiplexed motor
Inverter
Radiator & Pump
Reduction gear
Propeller
A1-2）Power source
Li-ion battery
A1-3）Pilot interface
Power lever
Display
A1-4）Management system
A2) Measurement system
A3) Airframe system
A4) Charging system
System control unit
Electric motor-glider system
(Flight demonstrator)
System configuration
27
3. Concepts
1. Multiplexed motor
2. Regenerative air brake
28
3. Concepts
3.1 Multiplexed electric motor system(1/3)
Our
motivations
1. Avoidance of “loss of engine power” for single piston engine aircraft.
2. Redundancy of electric motors.
Other
researches
1. Distributed motors and fans for VTOL (Alex
M. Stoll et al.
of Joby Aviation,
AIAA Aviation Technology, Integration and
Operations Conference 2014, AIAA2014-2407)
14th
2. Electric Propulsion for Vertical Flight (Michael Ricci of
LaunchPoint Technologies; AHS Transformative Vertical Flight
Workshop 2014, Arlington, VA )
Our selection
of approach
Putting multiplexed motor on a propeller shaft
29
3. Concepts
3.1 Multiplexed electric motor system(2/3)
1. Reduction of the size and weight
2. Optimization of the number of motors
motor
axis
#1
3. Isolation of failures
1. Directly coupling with each motor (additional
joint parts are unnecessary)
2. Quadruplex motor based on the trade-off
analysis
3. Individual contactors
#3
#4
motor housing
100
Wth[kgf]
Our
solutions
#2
5
90
4.5
80
4
70
3.5
60
3
50
2.5
40
2
30
1.5
20
1
Wth[kgf]
nopt
10
Wth/Wthmin
0
0.5
0
0
5
10
15
Number of motors
n
20
30
Wth/Wthmin
Technical
issues for
us
3. Concepts
3.2 Regenerative air brake system(1/5)
Our
motivations
1. Elimination of conventional systems by multifunctionality of electric motor.
2. Regeneration of electricity by electric motor.
Regenerative air brake system
Other
researches
1. Feasibility study of regenerative soaring (J.Philip Barnes, Perican Aero Group,
Our selection
of approach
1. Utilization of aerodynamic drag on the prop. due to regeneration
2. Simultaneously harvesting a certain amount of energy
SAE Tech. Paper 2006-01-2422, 2006)
2. WATTsUP can recuperate 13% of energy on every approach and
reduce the field length of landing(Pipistrel, Aircraft News,31 Mar 2015)
31
2. FEATHER Project
2.6 Regenerative air brake system(1/4)
Technical
issues for us
1. Simplify the control of descent rate
2. Avoidance of weight penalty and hardware complexity
3. Maximization of the regenerative electricity
Our solutions
1. Augmentation of descent rate by pulling the power lever
2. The simplest system configuration based on the field-oriented control method
3. Formulation of control algorithm based on the aerodynamic features
Motor
Inverter
Battery
Power lever
Generator
Rectifier
Capacitor
DC/DC
Conventional
Motor / Generator
Inverter
Battery
Field-oriented control
32
3. Concepts
3.2 Regenerative air brake system(3/5)
Torque command value
Motor torque is used as a command value
in field-oriented control method
Power lever
displacement
RGN
PWR
33
3. Concepts
3.2 Regenerative air brake system(3/5)
Motor torque
Airspeed = constant
Pitch angle of a blade = constant
Aerodynamic
feature of Prop.
（PWR）
Rotational
speed
0
Reverse
Rotation
Free rotation(NTL)
（RGN）
Significant
Drag!!
Disadvantage of FOC
Torque command value（RGN maximum）
34
3.2 Regenerative air brake system(3/5)
3. Concepts
Motor torque
Airspeed = constant
Pitch angle of a blade = constant
Aerodynamic
feature of Prop.
（PWR）
Rotational
speed
0
Free rotation(NTL)
opportunity loss
（RGN）
Torque command value（RGN maximum）
35
3. Concepts
3.2 Regenerative air brake system(3/5)
Motor torque
Airspeed = constant
Pitch angle of a blade = constant
Aerodynamic
feature of Prop.
（PWR）
Rotational
speed
0
Free rotation(NTL)
Maximization of the
regenerative electricity
（RGN）
Torque command value（RGN maximum）
36
3. Concepts
3.2 Regenerative air brake system(4/5)
-50.0
Actual prop. test
Torque[Nm]
-30.0
SmallSmall-scaled
prop. test
τ P max = 2πCP max ρN p2 D 5p RGN
-40.0
-20.0
The maximum torque is
proportional to Np2 at a β
value independent of Vair.
-10.0
0.0
β=10deg(Vair=35m/s)
β=30deg(Vair=35m/s)
β=10deg(Vair=25m/s)
β=30deg(Vair=25m/s)
10.0
20.0
30.0
β=20deg(Vair=35m/s)
β=116deg(Vair=35m/s)
β=20deg(Vair=25m/s)
β=116deg(Vair=25m/s)
PWR
40.0
50.0
-10
Np,
0
10
20
30
40
Revolution speed of propeller [rps]
Wind tunnel tests results for the actual propeller in RGN mode
(The flight demonstration was mainly conducted at angle of propeller pitch, β=14deg)
37
4. Flight demonstration
35.4
Tower
35.398
35.396
Lat[deg]
35.394
35.392
Runway
35.39
35.388
35.386
35.384
35.382
35.38
136.845
136.85
136.855
1km
136.86
136.865
136.87
136.875
136.88
136.885
136.89
136.895
Long[deg]
Typical example of the short traffic path
38
2. FEATHER Project
2.7 Flight demonstration
70
60
Battery SOC
Motor power,
Pm
Absolute altitude, H
Pm[kW]
Vair[m/s]
Np[rps]
SOC[%]
50
700
600
500
Rotational speed
of prop, Np
40
30
400
Airspeed,
Vair
20
10
300
200
100
0
-10
800
H[m]
Pm[kW], Vair[m/s], Np[rps], SOC[%]
80
0
Take-off
Touch-down
Sim. fail climb
Regenerative
soaring
-20
360
480
600
720
840
960
t[s]
Regenerative descend
w/o airbrake
-100
-200
1080 1200 1320 1440 1560
An example of flight test data
39
5. Summary
We have succeeded in flight demonstration as follows:
1. Avoidance of complete power loss in engine failure
during climb by using the multiplexed electric motor
2. Regeneration of electricity about 8% of maximum motor
output during descent
3. Control of descent rate by the proposed regenerative
airbrake system without conventional airbrake
4. Continuous “regenerative
regenerative soaring”
soaring free from descent in
thermal condition
Acknowledgement: The wind tunnel test in this research was partly supported by the Ministry of
Education, Culture, Sports, Science, and Technology grant (Basic Research A, number: 26249061).
40
∆ Np
∆VS
∆L
Torque
Thrust
Airspeed
41