Robots Driven by Compliant Actuators: Optimal Control Under Actuation Constraints

D.J. Braun, F. Petit, F. Huber, S. Haddadin, P. van der Smagt, A. Albu-Schaffer, S. Vijayakumar

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Anthropomorphic robots that aim to approach human performance agility and efficiency are typically highly redundant not only in their kinematics but also in actuation. Variable-impedance actuators, used to drive many of these devices, are capable of modulating torque and impedance (stiffness and/or damping) simultaneously, continuously, and independently. These actuators are, however, nonlinear and assert numerous constraints, e.g., range, rate, and effort limits on the dynamics. Finding a control strategy that makes use of the intrinsic dynamics and capacity of compliant actuators for such redundant, nonlinear, and constrained systems is nontrivial. In this study, we propose a framework for optimization of torque and impedance profiles in order to maximize task performance, which is tuned to the complex hardware and incorporating real-world actuation constraints. Simulation study and hardware experiments 1) demonstrate the effects of actuation constraints during impedance control, 2) show applicability of the present framework to simultaneous torque and temporal stiffness optimization under constraints that are imposed by real-world actuators, and 3) validate the benefits of the proposed approach under experimental conditions.
Original languageEnglish
Pages (from-to)1085-1101
Number of pages17
JournalIEEE Transactions on Robotics
Issue number5
Publication statusPublished - 1 Oct 2013

Keywords / Materials (for Non-textual outputs)

  • actuators
  • humanoid robots
  • optimal control
  • optimisation
  • actuation constraints
  • anthropomorphic robots
  • compliant actuators
  • impedance profiles
  • temporal stiffness optimization
  • torque optimization
  • torque profiles
  • variable-impedance actuators
  • Actuators
  • Dynamics
  • Impedance
  • Joints
  • Robot kinematics
  • Torque
  • optimal impedance control
  • redundant robots
  • variable impedance actuation


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