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 VA 1
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 Ticket fee[us$/ask] 1.0 0.8 0.6 0.4 0.2 0.0 Higher Cost 1 10 100 1000 No. of seats Regular fee Discount fee 2.35 0.34 Air Line Air carrier Lower Safety Air taxi & Commuter General aviation 10.53 16.57 The fatal accident rate of small aircraft is about 10X higher than that of large aircraft Unit ticket fees for domestic flights (in JAPAN, 2014) 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 Solution Electric aircraft technologies JAXA Current:10X higher than airliner 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 FY2013 Fabrication FY2014 Integration and flight test 1. Multiplexed motor 2. Regenerative air brake 7
2. FEATHER Project 2.2 Overview of the demonstrator Original aircraft: Diamond aircraft type HK36TTC-ECO Reduction gear Electric motor 1Multiplexed motor Power lever Display 2Pilot interface Monitoring unit Battery pack Under wing container 3Li Li-ion ion battery 8
2. FEATHER Project 2.3 Electric propulsion system Reduction gear Radiator Inverter Electric motor Electric propulsion system 9
2. FEATHER Project Specifications Wing span 16.33m Take-off weight at the flight test Crew member Types of electric motor and inverter Motor control method Maximum total shaft power (at RPM) Type of power source System voltage (open circuit at 100%SOC) and Current 2.4 Specifications 800kg 1 person Permanent magnet type synchronous motor (three-phase) and IGBT inverter FOC (Field-oriented control) 60kW (2.5min. at 6586RPM), 63kW(proven at flight) Lithium-ion battery (32 cells in series) 128V, 750A 10
2. FEATHER Project 220mm 232mm inverters 2.5 Multiplexed electric motor system e-genius 13) 3.75 kg 1 2 3 4 Characteristics Efficiency[%] Antares20E 1) Rapid200FC 11) 100 95 90 85 80 75 70 Electric Waiex 12) +:Efficiency :Power density EV motor(leaf) Aircraft piston engine FEATHER(JAXA) 30 40 50 60 70 80 Maximum output[kw] Compact Light weight(2.17kw/kg) High efficiency(95%) High strength of structure 11 3 2.5 2 1.5 1 0.5 0 Power density[kw/kg]
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 Power lever Motor Generator Inverter Rectifier Capacitor Battery 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 Variable T= C RGN δ PL (-100% δ PL 0%) Constant T=C PWR δ PL (0% δ PL 100%) δ PL Power lever displacement RGN PWR 13
2. FEATHER Project 2.6 Regenerative air brake system(3/4) 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 Torque 0 (PWR) (RGN) Counter torque of Prop. Rotational speed Free rotation(ntl) Torque command value (corresponding to power lever max) 14
2. FEATHER Project 2.6 Regenerative air brake system(4/4) Motor/ Generator Inverter Battery Specially designed power lever to facilitate the control of descent rate and regeneration Propeller Pitot tube N p V air System control unit Target Torque displacement Regenerative power Power lever Display V air 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 Pm[kW], Vair[m/s], Np[rps], SOC[%] 80 70 60 50 40 30 20 10 0-10 Motor power, Pm Take-off Sim. fail climb Battery SOC Rotational speed of prop, Np Regenerative soaring Absolute altitude, H -100-20 -200 360 480 600 720 840 960 1080 1200 1320 1440 1560 t[s] An example of flight test data Airspeed, Vair Pm[kW] Vair[m/s] Np[rps] SOC[%] Regenerative descend w/o airbrake 800 700 600 500 400 300 200 100 0 H[m] Touch-down 17
2. FEATHER Project 2.7 Flight demonstration 0 0-1 -20 Airbrake Descent by using the conventional airbrake Pm[kW], dh/dt[m/s] -2-3 -4-5 Pm[kW] dh/dt[m/s] Power lever [%] -40-60 -80-100 Power lever[%] -6-120 490 495 500 505 510 515 520 t[s] Descent by using the regenerative airbrake system Correlation of the power lever displacement, regenerative power and consequent descent rate, dh/dt during descent by using regenerative airbrake system 18
Outline 1. Future Vision and Issues 2. FEATHER project 3. Toward future electric aircraft 19
Range Extension 3. Toward future electric aircraft 1000 800 Fuel cell & H 2 TOYOTA s MIRAI with 2.0kW/kgFC stack. High energy density Li-ion battery Range/km 600 400 Taurus G4 High AR wing Drag reduction (L/D>25) Hitachi demonstrated 335Wh/kgand30Ahon Nov. 2014 and they have developed by 2020. http://www.hitachi.com/new/cnews/month/2014/11/141114.html 200 Skyhawk172 0 Simple conversion of petrol to battery(4pax, L/D<10) 0 100 200 300 400 500 Energy density/whkg-1 20
Automatization 3. Toward future electric aircraft 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 Inverter Sensors Computer Power by wire Key technology Collaborative work Sensing Actuator 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
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1. Backgrounds & Objectives Aeronautical Technology Directorate In JAXA Long-term research toward zero-emission 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 2014 2015 June March July November February Start Complete of electric propulsion system Integration Approval for flight test Approval for flight test Maiden flight Final flight FY2012 Design FY2013 Fabrication FY2014 Integration and flight test 120~150km/h ~0.5min. ~ 10m 600m Runway Jump test ~5min. 2000m Runway Jump test ~ 80m ~20min. ~600m 2700m Runway Short traffic pattern flight test 26
A) Electric motor-glider system 2. Systems A1) Electric propulsion system A1-1)Driving system Multiplexed motor Inverter Radiator & Pump Reduction gear Propeller A1-2)Power source Li-ion battery A2) Measurement system A3) Airframe system A4) Charging system A1-3)Pilot interface A1-4)Management system Power lever Display System control unit System configuration Electric motor-glider system (Flight demonstrator) 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, 14 th AIAA Aviation Technology, Integration and Operations Conference 2014, AIAA2014-2407) 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) Technical issues for us Our solutions 1. Reduction of the size and weight 2. Optimization of the number of motors 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 W th [kgf] 100 90 80 70 60 50 40 30 motor axis #1 #2 #3 #4 motor housing 20 1 10 Wth[kgf] n opt Wth/Wthmin 0.5 0 0 0 5 10 15 20 Number of motors n 30 5 4.5 4 3.5 3 2.5 2 1.5 W th /W thmin
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. Other researches Our selection of approach Regenerative air brake system 1. Feasibility study of regenerative soaring (J.Philip Barnes, Perican Aero Group, 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) 1. Utilization of aerodynamic drag on the prop. due to regeneration 2. Simultaneously harvesting a certain amount of energy 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 Power lever Motor Generator Inverter Rectifier Capacitor Battery 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 0 Airspeed = constant Pitch angle of a blade =constant (PWR) Aerodynamic feature of Prop. Rotational speed Reverse Rotation Significant Drag!! Disadvantage of FOC Free rotation(ntl) (RGN) Torque command value(rgn maximum) 34
3. Concepts 3.2 Regenerative air brake system(3/5) opportunity loss Motor torque 0 Airspeed = constant Pitch angle of a blade =constant (PWR) Aerodynamic feature of Prop. Rotational speed Free rotation(ntl) (RGN) Torque command value(rgn maximum) 35
3. Concepts 3.2 Regenerative air brake system(3/5) Maximization of the regenerative electricity Motor torque 0 Airspeed = constant Pitch angle of a blade =constant (PWR) Aerodynamic feature of Prop. Rotational speed Free rotation(ntl) (RGN) Torque command value(rgn maximum) 36
3. Concepts 3.2 Regenerative air brake system(4/5) -50.0-40.0-30.0 RGN τ = πc ρn D 2 5 P max 2 P max p p Small-scaled prop. test Actual prop. test Torque[Nm] -20.0-10.0 0.0 10.0 20.0 30.0 40.0 50.0 β=10deg(vair=35m/s) β=20deg(vair=35m/s) β=30deg(vair=35m/s) β=116deg(vair=35m/s) β=10deg(vair=25m/s) β=20deg(vair=25m/s) β=30deg(vair=25m/s) β=116deg(vair=25m/s) -10 0 10 20 30 40 N p, Revolution speed of propeller [rps] PWR The maximum torque is proportional to N p2 at a β value independent of V air. 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 35.398 Tower Lat[deg] 35.396 35.394 35.392 35.39 35.388 35.386 35.384 35.382 Runway 35.38 136.845 136.85 136.855 136.86 136.865 136.87 136.875 136.88 136.885 136.89 136.895 1km Long[deg] Typical example of the short traffic path 38
2. FEATHER Project 2.7 Flight demonstration Pm[kW], Vair[m/s], Np[rps], SOC[%] 80 70 60 50 40 30 20 10 0-10 Motor power, Pm Take-off Sim. fail climb Battery SOC Rotational speed of prop, Np Regenerative soaring Absolute altitude, H -100-20 -200 360 480 600 720 840 960 1080 1200 1320 1440 1560 t[s] An example of flight test data Airspeed, Vair Pm[kW] Vair[m/s] Np[rps] SOC[%] Regenerative descend w/o airbrake 800 700 600 500 400 300 200 100 0 H[m] Touch-down 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 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
N p V S L Torque Thrust Airspeed 41