Precise End-Effector Control for an Aerial Manipulator Under Composite Disturbances: Theory and Experiments

Meng Wang

Abstract:

One of inescapable challenges in facilitating the
application of aerial manipulators is to achieve the high precision
control performance of the end-effector. The manipulator motions
beneath the UAV platform constantly contend with composite
disturbances, such as floating base, strong inner coupling effects,
and model uncertainties. These factors collectively contribute to
an inadequate control performance. In this paper, a composite
control scheme is presented to tackle this issue. Specifically,
a joint velocity planner is proposed to handle the base-floating
disturbance in kinematic loop. By virtue of the generated joint
reference signal, the base-floating disturbance can be effectively
alleviated. The tracking error of the end-effector can be ensured
within a small set. Moreover, in a complementary manner, neural
network (NN) approximation and nonlinear disturbance observer
(NDO) compensation are combined to track the joint references.
The NN is adopted to estimate composite dynamic model including
inner coupling effects and model uncertainties, while the
NDO is designed to handle the remaining uncompensated part.
The stability of the closed-loop system including the manipulator
kinematics and dynamics is guaranteed using the Lyapunovlike
method. Experimental results are reported to manifest the
effectiveness of the proposed composite control scheme.