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AAM Ecosystem Aircraft Working Group:Electric Propulsion for Urban Air Mobility

AgendaSeptember 30, 2021TopicSpeakerTime (EDT)Welcome and IntroductionsCarl Russell3:00 - 3:05PMRVLT eVTOL Propulsion overview Peggy Cornell3:05-3:15PMPower Quality research andexperimental capabilityPat Hanlon and Dave Sadey3:15-3:35PMMotor Reliability researchTom Tallerico3:35-3:50 PMWorking group open discussionWrap-up3:50-4:25PMCarl Russell4:25 – 4:30PM

Upcoming MeetingsThe Aircraft Working Group will hold their meeting on the last Thursday ofevery month from 3:00PM -4:30PM EDT (12:00PM -1:30PM PDT). October 28, 2021: November 2021:TBDTBD3

Platform and Discussion Active Participants– Platform: MS Teams– Discussion: MS Teams microphone and chat functions Leave your cameras/webcams off to preserve WiFi bandwidth Enter comments/questions in the chat function on the right side of the screen Use your mute/unmute button Use the “Raise Hand” function in MS Teams to let the emcee know you would like to make acomment or ask a question Say your name and affiliation before you begin speaking Speak loudly and clearly Listen Only Participants– Platform: YouTube Live Stream (go to https://nari.arc.nasa.gov/aam-portal/ for the link!) All Participants– Polling and anonymous questions: Conferences.io Enter https://arc.cnf.io/ into your browser Select the Aircraft Working Group: Electric Propulsion for Urban Air Mobility Questions will be addressed at the facilitator’s discretion4

Revolutionary Vertical Lift Technology (RVLT) OverviewAAM Ecosystem Aircraft Working Group MeetingElectric Propulsion for Urban Air MobilitySept 30, 2021Peggy Cornell, eVTOL Propulsion Subproject Managerwww.nasa.gov5

SummaryNASA RVLT is focused on Vertical lift supporting Urban Air Mobility Three On-going Tech Challengeso Electric propulsion reliability andperformanceo Tools to compute vehicle source noise andperformanceo Fleet noise Approving new Tech Challengeso Ride quality and passenger acceptanceo Crash safetyOur vision is to create a future whereVTOL configurations operate quietly,safely, efficiently, affordably and routinelyas an integral part of everyday life.6

AAM and UAMNASA Focus is on Advanced AirMobility (AAM) Missions– AAM missions characterized by 300nm range– Vehicles require increased automationand are likely electric or hybrid-electric– Rural and urban operations and cargodelivery are included– Urban Air Mobility (UAM) is a subset ofAAM and is the segment that isprojected to have the most economicbenefit and be the most difficult todevelopo UAM requires an advanced urbancapable vehicleo UAM requires an airspace systemto handle high-density /7

NASA Concept Vehicles – Generic Geometries that Capture Many UAM FeaturesNASA reference vehicles Widely shared Fully documentedcompromises No plans to build or fly these concepts Realistic set ofVehicles contain relevant UAM features andtechnologies––––– Realistic performanceBattery, hybrid, diesel propulsionDistributed electric propulsionHigh efficiency rotorsQuieter rotorsWake interactionsProvide configurations for–––––Communication of NASA’s Urban Air Mobility researchDesign and analysis tool developmentTechnology trade studies and sizing excursionsModeling operational scenariosCommon configurations for studies in acoustics, flightdynamics, propulsion reliability, etc.8

RVLT Near Term Focus for ResearchFY21-FY23VehiclePropulsionReliabilityTech Challenge: Reliable and Efficient Propulsion Components for UAM Re-configure laboratories for electricpropulsion testing Conduct initial single string tests Develop tools to assess motor reliability Develop high reliability conceptualmotor designTech Challenge: UAM Operational Fleet Noise AssessmentUAMFleetNoise Generate Noise Power Distance (NPD) database for several UAMreference configurations and trajectories Conduct fleet noise assessments Initiate psychoacoustic testing to assess human response to UAM vehiclesTech Challenge: Tools to Explore the Noise and Performance of Multi-Rotor UAM VehiclesNoise andPerformanceSafety andAcceptability Plan and conduct validation experiments Improve efficiency and accuracy of conceptual design tools Conduct high-fidelity configuration CFD for validation and reference Improve community transition and training for analysis toolsTargeted Research in These Areas for Future Tech Challenges UAM crashworthiness and occupant protectionAcceptable handling and ride qualities for UAM vehiclesIce accretion and shedding for UAM9

RVLT.TC.UAM.Electric.1Reliable and Efficient Propulsion Components for UAMObjective Develop design and test guidelines, acquire data, and explore newconcepts that improve propulsion system component reliability byseveral orders of magnitude over state-of the-art technology forUAM electric and hybrid-electric VTOL vehicles.E-Drives RigApproach Iterative design, model, test and analyze–––––Apply vehicle level analysisDevelop experimental / analysis capabilitiesConduct tests (reliability of components, tool validation)Provide validated modelsDevelop design guidelines & test proceduresApply Vehicle Level AnalysisDevelop Experimental/ AnalysisCapabilitiesConduct TestsProvide Validated ModelsBenefit/Pay-off Validated power/propulsion/thermal models High reliability motor design – feasibility of 2-4 orders of magnitudereliability improvement Design guidelines for eVTOL propulsion and thermal components Test guidelines for propulsion and thermal components Candidate HVDC Power Quality and Permanent Magnet MachineStandardsDesign Guidelines and TestProcedures10

eVTOL Power / Powertrain Testbeds Scaled Power Electrified Drivetrain (SPEED) -Low-PowerTestbed– Low power (up to 9 kW) motor & controls– Low voltage test platform for high power testbed hardware Advanced Reconfigurable Electrical Aircraft Lab (AREAL) High Power Testbed– Emulated, reconfigurable system (single-string, multi-string)– 1kVDC Peak, nominal 200kW source E-Drives Rig– Test motors, gearboxes & power electronics– Emulation of rotor loads– Mechanical, electrical, vibration, & thermalmeasurementsE-Drives Rig

RVLT Motor Design Efforts – Goal: Improved MotorReliability External Efforts1: 2 Contract Funded Design1)2) 1)2)University of Wisconsin via OSU ULI Integrated, fault-tolerant motor/drive design for RVLTquadcopterBalcones Technologies vis Phase III NASA STTR Developing Brushless Doubly-Fed Machine (BFDM)design for RVLT-class vehicle (100-200 kW)Internal Efforts2:Magnetically Geared Motors and Novel Designs Exploring trade space of reliable motor topologies forUAM applications using in-house codes.Example: Outer Stator Magnetically Geared MotorWinding Reliability Model Development Developing modeling and experimental capability toexplore/predict winding reliability1. J. Swanke, T. Jahns, “Reliability Analysis of a Fault-Tolerant Integrated Modular Motor Drive (IMMD) for an Urban Air Mobility (UAM)Aircraft Using Markov Chains.” 2021 AIAA/IEEE Electric Aircraft Technologies Symposium (EATS).2. T. F. Tallerico, Z. A. Cameron, J. J. Scheidler and H. Hasseeb, "Outer Stator Magnetically-Geared Motors for Electrified Urban Air MobilityVehicles," 2020 AIAA/IEEE Electric Aircraft Technologies Symposium (EATS), New Orleans, LA, USA, 2020, pp. 1-25.

Standards & Tools Leading two SAE standards– AS7499 - Aircraft High Voltage Power Quality Standard (D. Sadey)– AS8441 – Minimum Performance Standard for Permanent Magnet Propulsion Motors and Associated Drives(Pat Hanlon) Participate in AAM (UAM) Aircraft Design& Development Working Group Developing Analysis Tools:– NPSS Developed high level electrical power system models & electrical port for architecture trades Demonstrated electrified propulsion system models Accepted into next release of NPSS– EPS-SAT Electrical power system sizing Utilized for trade studies and sensitivity analyses– Toolset for Motor Reliability Reliability Modeling of Electric Motor

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RVLT Experimental Capabilities and PowerQuality InvestigationPat Hanlon & Dave SadeyNASA GRC

RVLT E-Drives Rig (POC: Justin Scheidler/GRC)ScopeMotor(input)Dynamometer(output) Test motors, gearboxes, & power electronics Mechanical, electrical, vibration, & thermal measurements After upgrades completed, capable up to 21,500 rpm input& 7,400 rpm outputKey capabilities for this tech challengeE-Drives Rig (pre-upgrades) Validation-quality data (very high precision – e.g., gearboxefficiency up to 0.2% with 95% confidence) Directly measure temperature of energized motor windings (up to 1000 V RMScontinuous) Emulate rotor loads with new generator dynamometer Year-round operation (no reliance on cooling tower water) Provides platform for magnetic gear and motor evaluationSpecific Experiments Motor efficiency, output torque, and temperatures under steady-stateand transient conditions Performance mapping of magnetic gears (& possibly magnetically-gearedmotors) for motor design code validation & TRL advancement of new conceptsNew Generator

RVLT E-Drives Rig CapabilitiesGenerator capability overlaid with eVTOLmotor operating points (known orapproximated)Generator capabilities: Controlled via 500 Hz control loop Continuous– 0-2400 rpm238 Nm– 2400-3840 rpm 60kW constant– 3840-7400 rpm decreasing power to31kWat 7400 rpm Short duration (60 seconds)– 160% overload

RVLT Scaled Power ElectrifiEd Drivetrain (SPEED) Capabilities– Low power (up to 9 kW) motor & controls– Low voltage test platform for high power testbedhardware– Allows team to investigate controls and startvalidation/refinement of tools (NPSS andMATLAB)– Single-string (source-load) analysis Status– Assembly complete– Initial integrated motor/inverter tests andcharacterization begun– Integration and EMI lessons learned will be ofbenefit to AREAL

RVLT Advanced Reconfigurable Electrified Aircraft Lab (AREAL) Overview Scope– Investigate Power Quality & Integration Issues– Feed Standards (AS7499, AS8441) Capabilities– Emulated, Reconfigurable System Single-string, Multi-String– 1kVdc Peak, 600-700Vdc Nominal– 200kW Nominal Source Capacity– Ability to test Faults Experiments– Nominal, Transient, Fault Operation– Characterization and Response

AREAL Hardware DC Emulators– Reconfigurable to emulate most DC sourcesfrom a small-signal and transient level Physical Motor Stand– State-of-the-Art Inverter/Motor, Back-to-Back– Can replace as needed Motor Emulator– Ability to Emulate Physical Motor– Ability to Introduce Faults Fault Protection– Initially Contactors/Fuses– In the process of procuring advanced fault protection devices

AREAL DC Emulator Capabilities High Bandwidth DC Power Supply– 20kHz Large Signal Bandwidth– 40kHz Small Signal Bandwidth 500V, 100kW Bidirectional (2Q) per unit Multiple Applications– Source Emulator– Power Sink– Limited Capability as Amplifier for ImpedanceSweeps– Constant Power Load with programmablebandwidth Currently Developing Modifications– Developed dynamic model of 650V Wound FieldGeneratorunder Phase III SBIR with PCKA for PQ Study– Generator Model meets Lift Cruise PowerSystem PQ Requirements in accordance withAS7499 HVDC Power Quality– Using DCE dynamic model from WPAFB to matchtransient and frequency response of generatorwith mods– Also investigating low cost/ quick turnaroundemulation strategy w/ Speedgoat

AREAL StatusAREAL Testbed Lab layout being finalized Facility 480V Power Complete Cooling System being upgraded Arc Flash Study Completed forSingle String Safety Permit being updated