JAXA's electric propulsion systems
Akira Nishizawa
Emission free aircraft section
Innovative Aircraft Systems Research Aircraft Systems Research Team
Next Generation Aeronautical Innovation Hub Center
Japan Aerospace Exploration Agency(JAXA)
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Motivations of R&D
2. Study of FC–GT
hybrid aircraft
1. FEATHER project
Motivations
 Low operating cost
 Higher safety
 Simplified operation
Airliner
Commuter
Motivations
 Fuel saving
 CO2 reduction
Air‐Taxi
Electric propulsion system is a goal of MEA
2020
2030
2040+
Step by step development of electrc aircraft
2
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 3
Overview of the demonstrator
Original aircraft: Diamond aircraft type HK36TTC-ECO
MTOW=850kg
Monitoring unit
Power lever
Reduction gear
Electric motor
①Multiplexed motor
Display
②Pilot interface
Battery pack
Under wing container
③Li-ion battery4
Specification of power train
Specifications
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)
Maximum motor efficiency
95％(94% at cruise)
Maximum inverter efficiency
93％(90% at cruise)
Cooling
Water cooling (motors and inverters)
Types of propeller and reduction gear
MT propeller of type MTV-1 and HIRTH G50(1:3.16)
Motor and inverter weight (total)
Motor:29.0kg (=7.24kg*4), Inverter:14.3kg(=3.56kg*4)
Power weight ratio of electric motor
2.17kW/kg (w/o reduction gear)
Reduction gear and prop. weight
Reduction gear:8.5kg, Propeller:10.6kg
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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
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Multiplexed electric motor system(2/3)
Technical
issues for
us
1. Reduction of the size and weight
2. Optimization of the number of motors
3. Isolation of failures
Our
solutions
1. Directly coupling with each motor (additional
joint parts are unnecessary)
motor
axis
#1
#2
#3
#4
motor housing
2. Quadruplex motor based on the trade-off
analysis
3. Individual contactors
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Multiplexed electric motor system(3/3)
Characteristics




Compact
Light weight(2.17kW/kg)
High efficiency(95%)
High strength of structure
4
220mm
3
2
3.75㎏
1
232mm
inverters
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Technical challenges of multiplexed electric motor system
Avoidance of
complete loss of thrust at engine failure
1. Avoidance of
yaw moment imbalance
at one engine failure
2. Automatic detection of engine failure in the early stages
Safety improvement
FEATHER project
Single‐eingine pilot license
available for multi‐engine plane
Future potencial (Thechnical challenges)
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Regenerative air brake system(1/4)
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)
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Regenerative air brake system(2/4)
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
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Regenerative air brake system(3/4)
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
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Technical challenges of regenerative airbrake system
• Windmilling propeller
• Lower airspeed
• Lower altitude descent
Simplification of airbrake mechanism
FEATHER project
• Windmilling fan
• Higher airspeed
• Higher altitude descent
Efficiency improvement
Future potencial (Thechnical challenges)
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Other topics of JAXA oriented technologies for EPS
1. Development of Electric Aviation Motor Coil Using Thermal Conductive Heat‐
resistant Insulating Material
http://global.jaxa.jp/press/2013/05/20130
514_motor_coil_e.html
Collaboration with Nippon Kayaku Co., LTD
2. Estimate of Airspeed w/o Pitot tube
Collaboration with Tokyo University
The airspeed estimate system can approximately calcurate airspeed by using the motor current and rotational number only.
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Hybrid Propulsion System
Distributed electric fans
SOFC /GT core engine
High-efficiency, ultra low emission core engine
150pax electric hybrid aircraft
Electric fan
Hybrid propulsion system
Hybrid Propulsion System
Technological issues to be pursued
Light-weight and robust (distributed) electric fan
Electric generator system (FC-GT hybrid )
Fuel and power feed distribution control
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Thank you
http://www.aero.jaxa.jp/eng/research/frontier/feather/
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