Development of Strain Wave Gearing* for Space Flight ApplicationDevelopment of Strain Wave Gearing* for Space Flight Application

Harmonic Drive Systems, Inc.Harmonic Drive Systems, Inc.HD Division / Research & DevelopmentHD Division / Research & Development

*Strain wave gearing is also known as “Harmonic Drive®”

“Harmonic Drive®” is a registered trademark that can be used only on products which are manufactured and sold by Harmonic Drive Systems, Inc.

Corporate ProfileCorporate Profile

Harmonic Drive Systems Inc.Harmonic Drive Systems Inc.Business LocationBusiness Location

Head Office: 6Head Office: 6--2525--3 Minami3 Minami--Oi, ShinagawaOi, Shinagawa--ku, Tokyo JAPANku, Tokyo JAPANHotaka Plant: 1856Hotaka Plant: 1856--1 Hotakamaki, Azumino1 Hotakamaki, Azumino--shi,Nagano JAPANshi,Nagano JAPANSales Office: 6 Business Offices in JapanSales Office: 6 Business Offices in Japan

FoundedFoundedOctober 1970October 1970

Business DomainBusiness DomainManufacturing and sales of precision speed reducersManufacturing and sales of precision speed reducers

CapitalCapital¥¥666.8 million666.8 million

Net SalesNet Sales¥¥13,937 million (FY2005 ended March 31, 2006)13,937 million (FY2005 ended March 31, 2006)

EmployeesEmployees207 (as of March 31, 2006)207 (as of March 31, 2006)

Domestic SubsidiariesDomestic SubsidiariesHD Logistics, Inc. HD Logistics, Inc. Harmonic Precision Inc. Harmonic Precision Inc. Harmonic AD, Inc. Harmonic AD, Inc.

Overseas Subsidiaries and AffiliatesOverseas Subsidiaries and AffiliatesHarmonic Drive L . L . C . (Peabody, Massachusetts U.S.A.)Harmonic Drive L . L . C . (Peabody, Massachusetts U.S.A.)Harmonic Drive AG (Limburg a.d. Lahn GERMANY)Harmonic Drive AG (Limburg a.d. Lahn GERMANY)

ProductProduct

Sensor SystemSensor System

AccuDriveAccuDrive®®

Harmonic DriveHarmonic Drive®®

MechatronicsMechatronicsRotaryRotary ActuatorActuatorLinear ActuatorLinear Actuator

Direct Drive MotorDirect Drive MotorBeam Servo ScannerBeam Servo Scanner

Key Word: Key Word: TotalTotal Motion ControlMotion Control

Harmonic Drive®Harmonic Drive®

Basic gear component of Basic gear component of Harmonic DriveHarmonic Drive®®

Circular SplineCircular Spline

FlexsplineFlexspline

Wave GeneratorWave GeneratorWave Generator PlugWave Generator Plug

Wave Generator bearingWave Generator bearingRetainerRetainer

（（Oldham Coupling)Oldham Coupling)

Principles of MotionPrinciples of Motion

• The flexspline is deflected by the wave generator into an elliptical shape causing the flexspline teeth to engage with those of the circular spline at the major axis of the wave generator ellipse, with the teeth completely disengaged across the minor axis of the ellipse.

• When the wave generator is rotated clockwise with the circular spline fixed, the flexspline is subjected to elastic deformation and its tooth engagement position moves by turns relative to the circular spline.

• When the wave generator rotates 180 degrees clockwise, the flexspline moves counterclockwise by one tooth relative to the circular spline.

• When the wave generator rotates one revolution clockwise (360 degrees), the flexspline moves counterclockwise by two teeth relative to the circular spline because the flexspline has two fewer teeth than the circular spline. In general terms, this movement is treated as output power.

Type of Harmonic Drive®Type of Harmonic Drive®

Cup TypeCup Type(Cup Style)(Cup Style)

Silk Hat TypeSilk Hat Type(Hollow Shaft(Hollow Shaft Style)Style)

Ring TypeRing Type(Pancake Style)(Pancake Style)

CS CSF CSDCS CSF CSD

SH SHF SHDSH SHF SHD

FR FBFR FB

Circumstance of Development StartCircumstance of Development Start

•• The NASDA authorized parts for space application which make the The NASDA authorized parts for space application which make the base base technology of space development decreases rapidly by authorizatitechnology of space development decreases rapidly by authorization on declining etc. ( declining etc. ( ～～2000 )2000 )

•• Task team for space application was organized, and the future paTask team for space application was organized, and the future parts for rts for space application program was studied. (2001)space application program was studied. (2001)

•• In order to deal with in the long run and systematically, techniIn order to deal with in the long run and systematically, technical committee cal committee of parts for space application was established in NASDA. (2002)of parts for space application was established in NASDA. (2002)

•• In the committee, HD was authorized as an important part, and thIn the committee, HD was authorized as an important part, and the e development support was decided. (2003)development support was decided. (2003)

Development of Harmonic DriveDevelopment of Harmonic Drive®® for Space Flight Applicationfor Space Flight Application

•• Concept: Concept: –– To develop strain wave gearing as a internationally competitive To develop strain wave gearing as a internationally competitive part for space part for space

flight applicationflight application

Specification (Type, Size, Gear Ratio)Specification (Type, Size, Gear Ratio)

•• Application: PDM, APMApplication: PDM, APMRequest: long life, high positioning accuracy, hollow shaft desRequest: long life, high positioning accuracy, hollow shaft designign

Long Use TypeLong Use Type

•• Application: one shot mechanismApplication: one shot mechanismRequest: Light weight, CompactRequest: Light weight, Compact

Light Weight TypeLight Weight Type

Type:Type: SHFSHF, Size:, Size: 2020, Gear ratio:, Gear ratio: 1/1601/160(SHF(SHF--2020--160160--2A2A--GRGR--SP)SP)

Type:Type: CSDCSD, Size:, Size: 2020, Gear ratio:, Gear ratio: 1/1601/160(CSD(CSD--2020--160160--2A2A--GRGR--SP)SP)

Type of Harmonic Drive®Type of Harmonic Drive®

Cup TypeCup Type(Cup Style)(Cup Style)

Silk Hat TypeSilk Hat Type(Hollow Shaft(Hollow Shaft Style)Style)

Ring TypeRing Type(Pancake Style)(Pancake Style)

CS CSF CSDCS CSF CSD

SH SHF SHDSH SHF SHD

FR FBFR FB

Light weightLight weight typetype

Long use typeLong use type

RequirementRequirement

•• RequirementRequirement

MAC Grease MAC Grease LubricationLubrication

Less than Less than 1010--44 PaPaVacuum Vacuum PressurePressure

100100 CyclesCycles11 cycle: Within cycle: Within 360360°°

Output Revolution:Output Revolution:　　11××101066 revrevLifeLife

Light Weight TypeLight Weight TypeLong Use TypeLong Use Type

Sign Wave VibrationSign Wave Vibration：：X, Y and Z axis X, Y and Z axis 1010～～100100 HzHz　　25G25GRandom VibrationRandom Vibration：：X, Y, and Z axis X, Y, and Z axis 55～～2020 kHzkHz　　21G21G RMSRMS　　180180 sec.sec.

OperatingOperating：　：　--1010℃～℃～+80+80℃℃UnUn--operatingoperating：　：　--4040℃～℃～+80+80℃℃

K1K1　　1.381.38××1010４４ Nm/Nm/radrad (minimum)(minimum)（（Load Torque: 7.0 NmLoad Torque: 7.0 Nm））

Less Less tthan han 3030 arcarc--secsec

VibrationVibration

OperatingOperating：　：　--3030℃～℃～+80+80℃℃UnUn--operatingoperating：　：　--6060℃～℃～+95+95℃℃

Temperature Temperature RangeRange

K1K1　　1.101.10××1010４４ Nm/Nm/radrad (min.)(min.)（（Load Torque: 7.0NmLoad Torque: 7.0Nm））

Spring RateSpring Rate

Less than Less than 6060 arcarc--secsecTransmission Transmission AccuracyAccuracy

RequirementRequirement

Development FlowDevelopment Flow

1.1. Basic test and trial productionBasic test and trial productionEffect of grease quantityEffect of grease quantityEffect of input speedEffect of input speedEvaluation of Evaluation of processabilityprocessability

2.2. Engineering model testEngineering model testVibration testVibration testThermal vacuum testThermal vacuum testLife testLife test

3.3. Qualification Model TestQualification Model TestVibration testVibration testThermal vacuum testThermal vacuum testLife testLife test

Result of Basic Test and Trial ProductionResult of Basic Test and Trial Production

•• Condition of Engineering Model testCondition of Engineering Model test–– Grease quantityGrease quantity

–– Input speedInput speed500 r/min500 r/min

•• Evaluation of Evaluation of processabilityprocessability–– Oil impregnation processOil impregnation process

It was established.It was established.–– Domestic Domestic phenolicphenolic material for retainermaterial for retainer

It was evaluated that domestic material is equivalent It was evaluated that domestic material is equivalent to imported material.

Circular Circular SplineSplineFlexsplineFlexspline

0.30.3gg0.30.3ggTeethTeeth0.40.4ggInside of Inside of FlexsplineFlexspline0.10.1ggWave Generator bearingWave Generator bearing

Grease quantityGrease quantityParts of grease applicationParts of grease application

to imported material.

Effect of Input SpeedEffect of Input Speed

総回転数：1.0E+6Grease: F/S:0.8

開口部側胴部側

負荷トルク：±92Nm

mm

µm

未使用Ref線はR1600mm

5rpm

369084-06

50rpm

100rpm

605970-07

369084-05

FS-New

500rpm

回転速度による影響

Ref線はR2000mm

Ref線はR10000mm

369084-04

Ref線はR2200mm

Ref線はR2800mm

0 2 4 6 8

0

10

20

30

40

50

60

70Loaded torque: ±92Nm, Total input revolution: 1X106 rev.

Inside surface of Flexspline Inside surface of Flexspline

New

Diaphragm Flexpline opening end

Contact area with Wave Generator bearing

•• Surface of the Surface of the FlexsplineFlexspline inside inside after endurance testafter endurance test

Wear is concentrate to the opening Wear is concentrate to the opening end side of Flexspline.end side of Flexspline.

High SpeedHigh Speed

Input speedInput speed

Low SpeedLow SpeedWear is generated on the average.Wear is generated on the average.

Engineering Model TestEngineering Model Test

•• Test flowTest flow

JAXA TSCJAXA TSC

JAXA TSCJAXA TSC

JAXA TSCJAXA TSC

HDS HDS HotakaHotakaFactoryFactory

PlacePlace

Load Torque: Load Torque: 40 Nm, 20Nm one direction, continuous40 Nm, 20Nm one direction, continuousInput speed: 500 rpmInput speed: 500 rpmVacuum pressure:Vacuum pressure: 11××1010--44Pa (Max.)Pa (Max.)

Life testLife test

--1010℃→℃→+95+95℃℃ 11H holdH hold　　44cyclecycle、、Vacuum pressure:Vacuum pressure: 11××1010--44Pa (Max.)Pa (Max.)Measurement of Efficiency & starting torque on each cycleMeasurement of Efficiency & starting torque on each cycle

Thermal vacuum testThermal vacuum test

Sign Wave: X, Y, Z axis 5Sign Wave: X, Y, Z axis 5～～100Hz, 0.6100Hz, 0.6～～25G, 2oct/min25G, 2oct/minRandom: X, Y, Z axis 5Random: X, Y, Z axis 5～～2,000Hz 21G RMS 180 sec.2,000Hz 21G RMS 180 sec.

Vibration testVibration test

Starting Torque, Efficiency, Spring Rate, Transmission Starting Torque, Efficiency, Spring Rate, Transmission AccuracyAccuracyUnder atmospheric pressureUnder atmospheric pressure

Initial performance Initial performance testtest

Test conditionTest conditionTestTest

EM Test (Life Test)EM Test (Life Test)

•• Test ConditionTest Condition

EfficiencyEfficiency、、Increase of Lost MotionIncrease of Lost MotionVerificationVerification11XX101066 revrev. (output total revolution). (output total revolution)Requested lifeRequested life

Less than 1XLess than 1X1010--44PaPaVacuum PressureVacuum PressureRoom temperatureRoom temperatureTemperatureTemperature

2020Nm continuousNm continuous4040Nm continuousNm continuousLoaded torqueLoaded torque500500 r/minr/min　　CWCW continuouscontinuousInput speedInput speed　　

MAC greaseMAC greaseLubricationLubricationLong Use TypeLong Use Type　　(SHF(SHF--2020--160160--2A2A--GRGR--SP)SP)Harmonic DriveHarmonic Drive®®

No.2No.2No.1No.1

EM Test (Life Test)EM Test (Life Test)

•• Efficiency under life test (No.1)Efficiency under life test (No.1)Lubricant: MAC grease, Loaded torque: 40 Nm, Input speed: 500 Lubricant: MAC grease, Loaded torque: 40 Nm, Input speed: 500 r/minr/min

0%

20%

40%

60%

80%

100%

0.0E+00 5.0E+03 1.0E+04 1.5E+04Output Total Revolution　[rev]

Effic

ienc

y

53465346 revrev. (output total revolution). (output total revolution)Test was stopped because of efficiency drop.Test was stopped because of efficiency drop.(Test jig input bearing was damaged.)(Test jig input bearing was damaged.)

Lost Motion was measured at these points.Lost Motion was measured at these points.

EM Test (Life Test)EM Test (Life Test)

•• Efficiency under life test (No.2)Efficiency under life test (No.2)Lubricant: MAC grease, Loaded torque: 20 Nm, Input speed: 500 Lubricant: MAC grease, Loaded torque: 20 Nm, Input speed: 500 r/minr/min

0%

20%

40%

60%

80%

100%

0.0E+00 5.0E+03 1.0E+04 1.5E+04Output total revolution [rev]

Effi

cien

cy

13513 13513 rev. (output total revolution)rev. (output total revolution)Test was stopped because of efficiency drop.Test was stopped because of efficiency drop.

Lost motion was measured at these point.Lost motion was measured at these point.

Test jig input bearing was replaced.Test jig input bearing was replaced.

EM Test (Life Test)EM Test (Life Test)

•• Flexspline after life test (No.2)Flexspline after life test (No.2)

FlexsplineFlexspline after life testafter life test

FlexsplineFlexspline iinner surfacenner surface

FlexsplineFlexspline toothtooth

EM Test (Life Test)EM Test (Life Test)

Outer surface of Wave Generator bearing outer raceOuter surface of Wave Generator bearing outer race

Wave Generator bearing ballsWave Generator bearing balls

Wave Generator after life testWave Generator after life test

Wave Generator after test (No.2)Wave Generator after test (No.2)

EM Test (Life Test)EM Test (Life Test)

•• Results of Life TestResults of Life Test

Output torque: Output torque: 220Nm0Nm

Input speed: Input speed: 500 r/min500 r/min

Output torque: Output torque: 40Nm40Nm

Input speed: Input speed: 500 r/min500 r/min

Test conditionTest condition

１３５１３１３５１３ rev.rev.

（５３４６（５３４６ rev.rev.））※※This test was stopped This test was stopped

because of efficiency drop, because of efficiency drop, but it found the cause was but it found the cause was damage of jig bearing by damage of jig bearing by investigation after test. investigation after test.

Output total revolutionOutput total revolution

••The test was stopped The test was stopped because the efficiency drop because the efficiency drop rapidly.rapidly.

••Remarkable wear can be Remarkable wear can be seen on the Circular seen on the Circular SplineSplineteeth, teeth, FlexsplineFlexspline teeth and teeth and inside and outside of Wave inside and outside of Wave Generator bearing outer Generator bearing outer race. race.

••The cause of efficiency drop The cause of efficiency drop was loss torque of input jig was loss torque of input jig bearing. bearing.

••Harmonic Drive can still on Harmonic Drive can still on operate though wear can be operate though wear can be seen on the inside of seen on the inside of Flexspline. Flexspline.

ResultsResults

No.2No.2

No.1No.1

No.No.

EM Test (Life Test)EM Test (Life Test)

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1 10 100 1000

Output torque (continuous)　[Nm]

W/G

tota

l rev

olut

ion 　

[rev]

20 40

•• Expected lifeExpected life

EM test resultEM test result

Expected lifeExpected life

Life requirementLife requirement

ConclusionConclusion

•• There is no damage of Harmonic DriveThere is no damage of Harmonic DriveRR under vibration test and under vibration test and thermal vacuum test.thermal vacuum test.

•• Lubrication under vacuum environment is a much tougher Lubrication under vacuum environment is a much tougher condition more than under atmosphere.condition more than under atmosphere.

•• To satisfy the life requirement, operating torque should be To satisfy the life requirement, operating torque should be lowered. lowered.

•• Process from wear start to the end of life should be investigateProcess from wear start to the end of life should be investigatein future development.in future development.