Robust Translational Force Control of Multi-Rotor UAV for Precise Acceleration Tracking

Abstract

In this paper, we introduce a translational force control method with disturbance observer (DOB)-based force disturbance cancellation for precise three-dimensional acceleration control of a multi-rotor UAV. The acceleration control of the multi-rotor requires conversion of the desired acceleration signal to the desired roll, pitch, and total thrust. But because the attitude dynamics and the thrust dynamics are different, simple kinematic signal conversion without consideration of those difference can cause serious performance degradation in acceleration tracking. Unlike most existing translational force control techniques that are based on such simple inversion, our new method allows controlling the acceleration of the multi-rotor more precisely by considering the dynamics of the multi-rotor during the kinematic inversion. By combining the DOB with the translational force system that includes the improved conversion technique, we achieve robustness with respect to the external force disturbances that hinders the accurate acceleration control. µ-analysis is performed to ensure the robust stability of the overall closed-loop system, considering the combined effect of various possible model uncertainties. Both simulation and experiment are conducted to validate the proposed technique, which confirms the satisfactory performance to track the desired acceleration of the multi-rotor.Note to Practitioners: Abstract-This paper presents a method for controlling the acceleration of a multi-rotor accurately under the presence of translational force disturbance. Unlike the existing methods, the new signal conversion technique that considers the dynamics of the multi-rotor in the process of converting the target translational acceleration signal to the target roll, pitch and thrust signal enables a more accurate translational force control. The disturbance observer (DOB) structure applied to the translational force control system overcomes the acceleration control performance deterioration caused by external translational force disturbance. Through the combination of the two techniques, the acceleration of the multi-rotor can be accurately controlled not only in the nominal environment but also in the presence of translational force disturbance.

Hitchhiker: A Quadrotor Aggressively Perching on a Moving Inclined Surface Using Compliant Suction Cup Gripper

“…12 (a)) could also be a reference in the future. An elaborated controller considering disturbance rejection and asynchronization between thrust and attitude [40] might be necessary to reduce the relative angle and velocity errors at the time of perching.…”

Dynamic observer‐basedH∞ robust control for a ducted coaxial‐rotor UAV

“…Usually, the system uncertainty is defined as unknown disturbance or as unknown input. In the existing work [15,16,17,31,32], system uncertainties and external disturbances are bounded by some scalars, without more detailed expressions. In order to better enhance the robustness of the proposed control method to system uncertainties, crosswind disturbances and other non-linear disturbances, the research should be basically developed on a control-oriented model.…”

“…In order to design controllers that are based on measured outputs and limited model, different kinds of observer-based controllers have been investigated. In [15][16][17], disturbance observer-based control was applied to design hierarchical controllers for a multi-rotor UAV and a coaxial-rotor UAV, respectively. The observer was used for estimating the state and the unknown aerodynamic disturbances.…”

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