Position and torque tracking: Series elastic actuation versus model-based-controlled hydraulic actuation

Alexander Otten, Wieke van Vuuren, Arno Stienen, Edwin H.F. van Asseldonk, Alfred Schouten, Herman van der Kooij

    Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

    4 Citations (Scopus)
    4 Downloads (Pure)


    Robotics used for diagnostic measurements on, e.g. stroke survivors, require actuators that are both stiff and compliant. Stiffness is required for identification purposes, and compliance to compensate for the robots dynamics, so that the subject can move freely while using the robot. A hydraulic actuator can act as a position (stiff) or a torque (compliant) actuator. The drawback of a hydraulic actuator is that it behaves nonlinear. This article examines two methods for controlling a nonlinear hydraulic actuator. The first method that is often applied uses an elastic element (i.e. spring) connected in series with the hydraulic actuator so that the torque can be measured as the deflection of the spring. This torque measurement is used for proportional integral control. The second method of control uses the inverse of the model of the actuator as a linearizing controller. Both methods are compared using simulation results. The controller designed for the series elastic hydraulic actuator is faster to implement, but only shows good performance for the working range for which the controller is designed due to the systems nonlinear behavior. The elastic element is a limiting factor when designing a position controller due to its low torsional stiffness. The model-based controller linearizes the nonlinear system and shows good performance when used for torque and position control. Implementing the model-based controller does require building and validating of the detailed model.
    Original languageEnglish
    Title of host publicationIEEE International Conference on Rehabilitation Robotics, Zürich, Switzerland
    Place of PublicationZürich, Switzerland
    ISBN (Electronic)978-1-4244-9861-1, 978-1-4244-9862-8
    ISBN (Print)978-1-4244-9863-5
    Publication statusPublished - 29 Jun 2011
    EventIEEE 12th International Conference on Rehabilitation Robotics, ICORR 2011 - ETH Zurich , Zürich, Switzerland
    Duration: 29 Jun 20111 Jul 2011
    Conference number: 12

    Publication series

    NameIEEE International Conference on Rehabilitation Robotics
    ISSN (Print)1743-0003
    ISSN (Electronic)1945-7901


    ConferenceIEEE 12th International Conference on Rehabilitation Robotics, ICORR 2011
    Abbreviated titleICORR
    Internet address


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