Adaptive Force Tracking Impedance Control for Aerial Interaction in Uncertain Contact Environment Using Barrier Function

In this article, an adaptive force tracking impedance control strategy is investigated for an aerial manipulator in physical interaction with uncertain contact environments. Based on the modified target impedance model, an adaptive impedance control method is proposed to accomplish aerial interaction in uncertain environments while maintaining a stable contact force, wherein the environment parameters of location and stiffness are estimated online to generate a reference position trajectory. Then, in order to ensure the tracking performance of the aerial manipulator, a robust pose tracking controller is designed, including a barrier function-based position controller and an adaptive attitude controller. Both proposed position and attitude controllers can ensure finite-time convergence of the state variable without the priori boundary information of disturbances. In particular, the position state variable can converge to a predefined neighborhood of zero from any initial state, and the control gain is not overestimated. The stability of the proposed strategy is analyzed via Lyapunov tools. Simulations and real-world experiments are conducted to illustrate the feasibility and performance of the proposed control strategy. Note to Practitioners —The motivation of this article is to investigate an adaptive force tracking impedance control strategy for aerial physical interaction with uncertain contact environments. In the existing impedance control schemes for aerial manipulators, the environment parameter of location or stiffness is often required to be utilized in controller design. However, in practical cases, the environmental parameters are not known precisely. Thus, this article presents an adaptive impedance method to automatically generate the reference position trajectory and achieve a stable contact force. Additionally, the tracking performance of the aerial manipulator is inevitably subject to uncertainties and disturbances. To ensure tracking convergence, traditional robust controllers generally involve high control gains than the known upper bounds of the disturbances. The main disadvantage of those controllers is that the control gain is often overestimated when the disturbance decreases. To address this issue, a barrier function-based position controller is proposed for the aerial manipulator, where the priori boundary information of disturbances is not needed and the control gain is adaptively adjusted according to the amplitude of disturbances. The stability and convergence of the proposed strategy are analyzed mathematically, and the experiments using an aerial manipulator provide promising results.