A new way of myoelectric A new way of myoelectric controlcontrol

MyoPro project

Daphne van BaalHans Rietman, Laura Kallenberg

25 september 2009

Roessingh Research and Development, Enschede, the Netherlands2

IntroductionIntroduction

Low usage myoelectric prosthesis

Advantages DisadvantagesNon-invasiveNo straps or harnessesUse of remaining muscles

Limited selectivityLack of intuitive controlLack of sensory feedback

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GoalGoal

Improve the control ofa myoelectric forearm prosthesis

by increasing the number of degrees of freedom

using multi-channel surface electrodes

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Experimental protocolExperimental protocol

• Ten healthy male subjects• One forearm amputee• Forty small electrodes in grid• Eight isometric contractions

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Isometric contractionsIsometric contractions

Flexion of wrist Extension of wrist Flexion of fingers Extension of fingers

Abduction of wrist Adduction of wrist Supination of forearm

Pronation of forearm

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Data analysisData analysis

• Data selection of active contractions• Time periods of 200 milliseconds• Root mean squared (RMS) value• Subject specific classification• Simple robust classifier (kNN)

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RMS-level imagesRMS-level images

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Robust classifierRobust classifier

Training set Test set

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ResultsResults

OutputInput FF FE P S AB AD WE WF

Finger flexion99.9

40.03 0.01 0.02

Finger extension

0.0199.8

90.01 0.01 0.08

Pronation99.9

60.04

Supination 0.01 0.0199.8

50.03 0.02 0.08 0.01

Wrist abduction

0.02 0.0199.9

40.02 0.01

Wrist adduction

0.0199.9

70.01

Wrist extension

0.02 0.03 0.02 0.10 0.0199.8

30.01

Wrist flexion 0.02 0.05 0.0199.9

3

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Continuous resultsContinuous results

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RMS-level images RMS-level images amputeeamputee

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Results amputeeResults amputee

OutputInput

FF FE P S AB AD WE WF ABP ADS

Finger flexion 100.0

Finger extension

99.28

0.48 0.25

Pronation 99.62

0.02 0.13 0.23

Supination 99.64

0.13 0.06 0.17

Wrist abduction

99.73

0.06 0.21

Wrist adduction

0.08 0.25 0.0499.5

60.02 0.06

Wrist extension

0.02 0.17 0.1199.6

40.06

Wrist flexion 0.10 0.0299.8

9

Wrist ab & pro 0.19 0.34 0.0699.4

1

Wrist ad & sup 0.6199.3

9

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ConclusionConclusion

• Offline classification – normally limbed: 99.9%– amputee patient: 99.6%

• Online classification– normally limbed: 93.4%

• Up to ten movements can be distinguished (five degrees of freedom)

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FutureFuture

• Validation: more measurements with amputees

• Additional patient specific contractions• Random-ordered contractions• Simultaneous control of different

contractions• Force level analysis for proportional control

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Questions?Questions?

For more information: www.myopro.nlFor more information: www.myopro.nl