NDLI: Design of a rotational hydro-elastic actuator for an active upper-extremity rehabilitation exoskeleton

Content Provider	IEEE Xplore Digital Library
Author	Stienen, A.H.A. Hekman, E.E.G. ter Braak, H. Aalsma, A.M.M. van der Helm, F.C.T. van der Kooij, H.
Copyright Year	2008
Description	Author affiliation: BAAT Med., Hengelo (ter Braak, H.; Aalsma, A.M.M.) \|\| Lab. for Biomech. Eng., Univ. of Twente, Enschede (Stienen, A.H.A.; Hekman, E.E.G.; van der Helm, F.C.T.; van der Kooij, H.)
Abstract	Our new Limpact exoskeleton is mechanically based on the design of the passive Dampace and will be powered by rotational hydro-elastic actuators (rHEAs), using impedance control. In this paper we describe the design of the rHEA, which is a novel, custom-designed combination of a rotational hydraulic actuator and a symmetric torsion spring. The rHEA can also be used as a springless hydraulic actuator for stiffer admittance control, or for isometric large-torque measurements of up to 100 Nm, by locking specific components in the design. Our implementation of HEA required alterations to the existing theoretical models to account for (1) our long flexible tubes between the valve and cylinder, and (2) the influence of the pressure feedback on the valve flow. These newly adapted models gave the best fits on the frequency response functions from our open- and closed-loop identification experiments, and might even provide a better fit for the data in the original publication of the theoretical models. Multi-sine identification showed the torque-tracking bandwidth restricted to 18 Hz for a constant spectral-density reference signal of 20 nm, mostly due the transport delays in the long flexible tubes. The measured torque resolution was better then 0.01 Nm. The delivered torque resolution was below 1 Nm, although at those small amplitudes, the output signal was accompanied by significant phase lead indicating some unaccounted for non-linearities in the actuator. When manipulated manually by forefinger and thumb, almost no distortion torques were felt during minimal-impedance and virtual-spring control. The symmetric torsion spring proved difficult to model correctly, and finding the best design became an iterative process. The spring in the prototype, used for the measurements as reported in this study, had a stiffness and maximum torque below those theoretically calculated, limiting the desired output to 22 Nm. With our latest spring design for the actuators in the Limpact, the maximum output torque is increased to 50 Nm.
Starting Page	881
Ending Page	888
File Size	909934
Page Count	8
File Format	PDF
ISBN	9781424428823
DOI	10.1109/BIOROB.2008.4762873
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2008-10-19
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Exoskeletons Feedback Hydraulic actuators Admittance measurement Valves Distortion measurement Torque measurement Impedance Springs Signal resolution
Content Type	Text
Resource Type	Article

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in