Shaping Impedances to Comply With Constrained Task Dynamics

Johannes Lachner, Felix Allmendinger, Stefano Stramigioli, Neville Hogan

Research output: Contribution to journalArticleAcademicpeer-review

9 Citations (Scopus)
144 Downloads (Pure)


Humans are capable of managing multiple tasks simultaneously. It is widely assumed that human motor control can be emulated by impedance control. To achieve human-like behavior, however, the impedance parameters of multiple tasks may vary during task execution. We propose an algorithm that shapes task impedance as a function of the robot's time-varying inertial properties. These properties involve virtually constrained masses and virtually constrained inertias that counteract a task in order to comply with a given constraint. In this work, we not only detect task conflicts, but also show how to handle them. Our method is able to control kinematically redundant robots. We developed a damping-design method that does not interfere with our desired Cartesian task-space behavior. The control approach was verified in experiments on a real robot. We compared our impedance shaping method with two alternative control approaches: simple impedance superposition and nullspace projection. Our method preserved the passivity while improving the Cartesian task performance of an impedance controller. The method has computational advantages, beneficial to control robots with many degrees of freedom.

Original languageEnglish
Pages (from-to)2750-2767
Number of pages18
JournalIEEE transactions on robotics
Issue number5
Early online date6 Apr 2022
Publication statusPublished - 1 Oct 2022


  • Human-inspired robot control
  • Impedance
  • Impedance control
  • Jacobian matrices
  • nullspace projection
  • Operational space control
  • Potential energy
  • Robot kinematics
  • Robots
  • Springs
  • Task analysis
  • Task conflicts
  • 22/4 OA procedure


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