Robust Variable Impedance Control for Aerial Compliant Interaction With Stability Guarantee

This article investigates a robust variable impedance control methodology for aerial manipulators to realize compliant and safe interaction tasks. Considering that the stability characteristics are generally overlooked in existing variable impedance controllers of the aerial manipulator, state-independent stability conditions are applied for time-varying impedance profiles to ensure the exponential stability of the desired variable impedance dynamics (DVID) as well as the boundedness of the state variables in the DVID. A command trajectory variable is introduced for converting the impedance control issue to a particular tracking issue, and then, a robust variable impedance controller based on the wrench estimator is designed to guarantee the exponential convergence of the translational states and impedance error of the aerial manipulator. The designed impedance controller is structurally simple and results in low implementation costs. Next, an improved attitude control approach with the command filter is developed for global flight attitude stability without any singularities or ambiguities, where the filter is introduced to avoid computing the derivative signals of the generalized force input. Finally, the effectiveness of the proposed control method is illustrated via numerical simulations and interaction experiments with different targets in real scenarios.