Afschrift, Maarten

De Bruyne, Sander

De Clercq, Dirk

Derave, Wim

Galle, Samuel

Malcolm, Philippe

English

Ghent University Academic Bibliography

FEASIBILITY OF AN EXOSKELETON POWERED BY ECCENTRIC JOINT WORK  FOR REDUCING WALKING METABOLIC COST.                            Philippe Malcolm ., Afschrift M., De Bruyne S., Galle S., Derave W., De Clercq D.                        Department of movement and sports sciences, Ghent University; Email: philippe.malcolm@ugent.be  INTRODUCTION Walking is a self-resistive movement that requires substantial metabolic energy. Different groups are developing walking exoskeletons in attempt to increase the metabolic economy. The main practical problem is limited power source autonomy. The proposed ideal solution would be to power the exoskeleton by recycling eccentric joint work that naturally occurs during walking (1). In previous experiments our group developed a pneumatically powered ankle foot exoskeleton that could reduce metabolic cost (2). =>Current goal: Measure inverse dynamics with the exoskeleton in order to find out if sufficient eccentric joint power is available to power the exoskeleton with, instead of powering the exoskeleton with compressed air.   METHODS 9 subjects  (height: 1m68 +/- 0.055, mass= 59.88kg +/- 3.87) walked over an instrumented walkway wearing a plantarflexion assisting exoskeleton that was tethered to an air compressor and a steering unit on a trolley (figure 1). Measurements:  - Ground reaction forces (Kistler& AMTI, 1000hz) - Full body kinematics (Qualisys, 200hz)  - Joint kinetics (Visual3D)    RESULTS AND DISCUSSION Results of one subject show clear eccentric power phases in the knee and hip joint (figure 2). The summation of te eccentric power phases indicates that sufficient eccentric joint power is available to reproduce the concentric power of the pneumatic exoskeleton.  One concern is that the eccentric joint power will have to be transferred over different joints and/or stored and released at a later time which will cause some energy loss.  Another concern is that a recycling exoskeleton will probably affect the gait pattern and consequently eccentric joint power. On the other hand humans could adapt their gait to optimally exploit a recycling exoskeleton just like they adapted to use anatomical features such as bi-articular muscles.      ACKNOWLEDGEMENTS  The authors wish to thank Ing. Davy Spiessens and Technische Orthopedie Belgiënv for their support.    REFERENCES: 1.Kuo AD. Human Movement Science 26 (2007) 617–656. 2. Galle S., et al. ISB XIIIth congress, 2011.  3. Stansfield BW, et al. GaitPosture, 23:288-94, 2006.     CONCLUSION Preliminary results show that a plantarflexion assisting exoskeleton that was previously shown to reduce metabolic cost could in theory be powered by recycling eccentric joint power during walking. If practical obstacles can be overcome such a recycling exoskeleton can benefit to clinical populations as well as able bodied (e.g. rescue workers).    -3-2-10123450 0.5 1Power (W/kg)Right Leg Stand Phase Percentage'Required' exoskeleton powerAnkle powerKnee powerHip power'Available' total eccentric joint powerFigure 2: Exoskeleton, ankle, knee, hip and total eccentric joint power during stance phase. The ‘available’ total eccentric joint work is 6.33 higher than the ‘required’ exoskeleton work.  Figure 1: Experimental  setup    

Feasibility of an exoskeleton powered by eccentric joint work for reducing walking metabolic cost

https://biblio.ugent.be/publication/3157921/file/3157927.pdf

Feasibility of an exoskeleton powered by eccentric joint work for reducing walking metabolic cost

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