Passivation of Projection-Based Null Space Compliance Control Via Energy Tanks

Alexander Dietrich, Christian Ott, Stefano Stramigioli

    Research output: Contribution to journalArticleAcademicpeer-review

    26 Citations (Scopus)


    A manipulator with kinematic redundancy w.r.t. a main task enables to perform an additional, subordinate task in its null space. The classical hierarchy-based approach is to apply dynamically consistent null space projections such that this lower-priority task does not disturb the main task. The major problem is that the control task hierarchy is established at the expense of the passivity of the system, which causes problems in terms of stability, robustness, and safety. Here, we extend this classical approach and passivate the closed-loop system by means of an energy tank, which is filled by the dissipated power of the active damping on both hierarchy levels. We validate the method in simulations and experiments on a torque-controlled manipulator. The concept is predestined for physical human-robot interaction and safety-relevant applications, where passivity must be guaranteed.

    Original languageEnglish
    Article number7368097
    Pages (from-to)184-191
    Number of pages8
    JournalIEEE Robotics and automation letters
    Issue number1
    Publication statusPublished - 1 Jan 2016


    • Compliance and impedance control
    • redundant robots


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