Accurate Control under Voltage Drop for Rotor Drones

TL;DR

This work tackles voltage drop (VD) disturbances in rotor drones during long endurance or aggressive maneuvers by introducing a voltage drop observer (VDO) that decouples lift losses from drone states and estimates VD-induced effects in real time. The control framework uses a translational loop with VDO to compensate lift loss and a rotational loop with a fixed-time sliding-mode observer (SMO) to counter torque disturbances, supported by Lyapunov-based stability analysis. The approach delivers improved altitude/position accuracy and robustness under VD, as demonstrated by indoor flight experiments where the VDO outperforms a baseline and a neural-network–based or gray-box VD approach in maintaining height and reducing tracking errors. Overall, the paper provides a interpretable, provably stable method enabling long-duration and high-performance flight of coaxial rotor drones in the presence of battery VD, with practical impact for reliable endurance missions.

Abstract

This letter proposes an anti-disturbance control scheme for rotor drones to counteract voltage drop (VD) disturbance caused by voltage drop of the battery, which is a common case for long-time flight or aggressive maneuvers. Firstly, the refined dynamics of rotor drones considering VD disturbance are presented. Based on the dynamics, a voltage drop observer (VDO) is developed to accurately estimate the VD disturbance by decoupling the disturbance and state information of the drone, reducing the conservativeness of conventional disturbance observers. Subsequently, the control scheme integrates the VDO within the translational loop and a fixed-time sliding mode observer (SMO) within the rotational loop, enabling it to address force and torque disturbances caused by voltage drop of the battery. Sufficient real flight experiments are conducted to demonstrate the effectiveness of the proposed control scheme under VD disturbance.

Figures (6)

• Figure 1: Flight scenario and trajectory of a drone conducting long-time flight. It can be seen that the drone with baseline controller descends gradually as the flight time progresses.
• Figure 2: Schematic of a rotor drone. Two frames are defined: the earth-fixed frame (North-East-Down) $\mathcal{E}$ and the body-fixed frame $\mathcal{B}$. Disturbance caused by voltage drop in the battery is primarily considered in this letter.
• Figure 3: Control architecture of the anti-disturbance control strategy addressing VD disturbance. Two observers estimating the corresponding disturbance are designed (i.e., VDO and SMO) and embedded in the control architecture. The translational loop operates at a frequency of 100 Hz while the rotational loop operates at a frequency of 500 Hz.
• Figure 4: Hardware platform. The positioning is obtained from a motion capture system. The attitude information is obtained from the fusion of motion capture system data and the onboard IMU data, which can be regarded as having negligible noise.
• Figure 5: Trajectory of the drone with voltage drop of battery over 280 seconds duration (VDO based control scheme). As the flight time progresses, the drone holds its height successfully.

Theorems & Definitions (5)

• Remark 1
• Lemma 1
• proof
• Remark 2
• Remark 3