Robust Control of An Aerial Manipulator Based on A Variable Inertia Parameters Model

TL;DR

The paper addresses dynamic coupling in aerial manipulators by modeling the coupling with variable inertia parameters that depend on the manipulator configuration. It introduces a disturbance-estimation scheme and a robust $H_{\infty}$ controller with translational-rotational decoupling via a virtual input, enabling stable flight while manipulating. The approach combines online computation of variable inertia terms, a Kalman-based disturbance estimator, and an LMI-based $H_{\infty}$ controller to achieve finite-gain $L_2$ stability under disturbances. Experimental results on a hex-rotor with a 2-DoF manipulator show accurate disturbance estimation (MAPD around 6–12%) and substantial hover-accuracy improvements in the horizontal plane when disturbance compensation is active.

Abstract

Aerial manipulator, which is composed of an UAV (Unmanned Aerial Vehicle) and a multi-link manipulator and can perform aerial manipulation, has shown great potential of applications. However, dynamic coupling between the UAV and the manipulator makes it difficult to control the aerial manipulator with high performance. In this paper, system modeling and control problem of the aerial manipulator are studied. Firstly, an UAV dynamic model is proposed with consideration of the dynamic coupling from an attached manipulator, which is treated as disturbance for the UAV. In the dynamic model, the disturbance is affected by the variable inertia parameters of the aerial manipulator system. Then, based on the proposed dynamic model, a disturbance compensation robust $H_{\infty}$ controller is designed to stabilize flight of the UAV while the manipulator is in operation. Finally, experiments are conducted and the experimental results demonstrate the feasibility and validity of the proposed control scheme.

Figures (12)

• Figure 1: Rigid body frame of the aerial manipulator.
• Figure 2: The control structure of the hex-rotor manipulator.
• Figure 3: Composition of the hex-rotor manipulator.
• Figure 4: The joints trajectory of the manipulator in the first experiment.
• Figure 5: The measured and estimated torque disturbance.