Variable Stiffness Actuators: Review on Design and Components

Sebastian Wolf, Giorgio Grioli, Oliver Eiberger, Werner Friedl, Markus Grebenstein, Hannes Hoppner, Etienne Burdet, Darwin G. Caldwell, Raffaella Carloni, Manuel G. Catalano, Dirk Lefeber, Stefano Stramigioli, Nikos Tsagarakis, Michael Van Damme, Ronald Van Ham, Bram Vanderborght, Ludo C. Visser, Antonio Bicchi, Alin Albu-Schaffer

Research output: Contribution to journalReview articleAcademicpeer-review

229 Citations (Scopus)


Variable stiffness actuators (VSAs) are complex mechatronic devices that are developed to build passively compliant, robust, and dexterous robots. Numerous different hardware designs have been developed in the past two decades to address various demands on their functionality. This review paper gives a guide to the design process from the analysis of the desired tasks identifying the relevant attributes and their influence on the selection of different components such as motors, sensors, and springs. The influence on the performance of different principles to generate the passive compliance and the variation of the stiffness are investigated. Furthermore, the design contradictions during the engineering process are explained in order to find the best suiting solution for the given purpose. With this in mind, the topics of output power, potential energy capacity, stiffness range, efficiency, and accuracy are discussed. Finally, the dependencies of control, models, sensor setup, and sensor quality are addressed.

Original languageEnglish
Article number7330025
Pages (from-to)2418-2430
Number of pages13
JournalIEEE/ASME Transactions on Mechatronics
Issue number5
Publication statusPublished - 1-Oct-2016
Externally publishedYes


  • Physical human-robot interaction
  • soft robotics
  • variable impedance actuators (VIAs)
  • variable stiffness actuators (VSAs)

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