  The research on aerial manipulation systems has been increased rapidly in
recent years. These systems are very attractive for a wide range of
applications due to their unique features. However, dynamics, control and
manipulation tasks of such systems are quite challenging because they are
naturally unstable, have very fast dynamics, have strong nonlinearities, are
very susceptible to parameters variations due to carrying a payload besides the
external disturbances, and have complex inverse kinematics. In addition, the
manipulation tasks require estimating (applying) a certain force of (at) the
end-effector as well as the accurate positioning of it. Thus, in this article,
a robust force estimation and impedance control scheme is proposed to address
these issues. The robustness is achieved based on the Disturbance Observer
(DOb) technique. Then, a tracking and performance low computational linear
controller is used. For teleoperation purpose, the contact force needs to be
identified. However, the current developed techniques for force estimation have
limitations because they are based on ignoring some dynamics and/or requiring
of an indicator of the environment contact. Unlike these techniques, we propose
a technique based on linearization capabilities of DOb and a Fast Tracking
Recursive Least Squares (FTRLS) algorithm. The complex inverse kinematics
problem of such a system is solved by a Jacobin based algorithm. The stability
analysis of the proposed scheme is presented. The algorithm is tested to
achieve tracking of task space reference trajectories besides the impedance
control. The efficiency of the proposed technique is enlightened via numerical
simulation.
