LIMPACT:A Hydraulically Powered Self-Aligning Upper Limb Exoskeleton

Alexander Otten, Hendrik Carsten Voort, Arno Stienen, Ronald G.K.M. Aarts, Edwin H.F. van Asseldonk, Herman van der Kooij

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The LIMPACT is an exoskeleton developed to be used in identifying the reflex properties of the arm in stroke survivors. Information on joint reflexes helps in designing optimal patient specific therapy programs. The LIMPACT is dynamically transparent by combining a lightweight skeleton with high power to weight ratio actuators. The LIMPACT is supported by a passive weight balancing mechanism to compensate for the weight of the exoskeleton and the human arm. Various self-aligning mechanisms allow the human joint axes to align with the axes of the exoskeleton which ensure safety and short don/doff times. The torque-controlled motors have a maximum torque bandwidth of 97 Hz which is required for fast torque perturbations and smooth zero impedance control. The LIMPACT's weight is reduced five times as gravitational forces are lowered using a model-based gravity compensation algorithm. The impedance controller ensures tracking of a cycloidal joint angle reference. A cycloid with an amplitude of 1.3 rd and a maximum velocity of 6.5 rd/s has a maximum tracking error of only 7%. The LIMPACT fulfills the requirements to be used in future diagnostics measurements for stroke patients.
Original languageEnglish
Article number7044558
Pages (from-to)2285-2298
Number of pages13
JournalIEEE/ASME transactions on mechatronics
Issue number5
Publication statusPublished - 2015


  • IR-98213
  • METIS-311455


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