What is it about?
This research explores a new way to control a special type of drone called a coaxial monocopter, which flies by using a pair of coaxial propellers, unlike normal quadcopters. What makes this drone unique is that it does not have traditional control surfaces such as wings or tail fins. Instead, it balances and steers itself by moving small internal weights, also known as moving masses. The main challenge in controlling such a system is that it behaves very differently from regular drones, the motion of the internal weights has a complicated effect on how it moves through the air. Traditional control methods struggle with this kind of motion because it is highly nonlinear and difficult to model accurately. To solve this problem, our study uses reinforcement learning, a type of artificial intelligence where the controller learns by trial and error. Specifically, we employ the Soft Actor-Critic (SAC) algorithm, which helps the drone learn stable and efficient flight behaviors through continuous interaction with a simulated environment. Over many training steps, the model learns how to adjust the moving masses to maintain balance, move toward a target, and handle external disturbances. The results demonstrate the potential for lightweight, adaptive aerial robots capable of operating in challenging environments.
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Why is it important?
This research is important because it introduces a new, lightweight, and adaptable way to control flying robots without using traditional wings or multiple propellers. Most drones today rely on complex mechanical parts, heavy sensors, or precise aerodynamic models to stay stable. In contrast, the coaxial monocopter in this study controls itself only by shifting its internal moving masses, making it much simpler and potentially more reliable. The findings could help develop smaller, cheaper, and more energy-efficient flying vehicles that can be used in real-world missions such as environmental monitoring, search and rescue, or exploring tight and confined spaces where traditional drones cannot operate effectively.
Perspectives
In my view, the significance lies not only in achieving flight stability but in demonstrating that intelligence can substitute for mechanical complexity. This opens the door for a new class of aerial robots, which is minimal, efficient, and adaptive, capable of exploring environments where traditional drones struggle. The combination of simplicity in design and sophistication in learning makes this research both elegant and forward-looking.
Duc Thien An Nguyen
New Mexico Institute of Mining and Technology
Read the Original
This page is a summary of: Reinforcement Learning-Based Control of a Moving Mass Coaxial Monocopter Using Soft Actor-Critic (SAC) Algorithm, July 2025, American Institute of Aeronautics and Astronautics (AIAA),
DOI: 10.2514/6.2025-3338.
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