Dynamic Center-of-Mass Reconfiguration for Enhanced UAV Free-Fall Stability, Structural Protection, and Energy Efficiency

The stability of unmanned aerial vehicles (UAVs) during the propulsion failure remains a critical safety challenge. This study presents a center-of-mass (CoM) correction device, a compact, under-slung, and dual-axis prismatic stage, which can reposition a dedicated shifting mass within the UAV frame to generate stabilizing gravitational torques by the closed-loop feedback from the inertial measurement unit (IMU). Two major experiments were conducted to evaluate the feasibility of the system. In a controlled roll test with varying payloads, the device produced a corrective torque up to 0.039 N·m, reducing maximum roll deviations from nearly 90° without the device to less than 5° with it. In a dynamic free-fall simulation, the baseline UAV exhibited rapid tumbling and inverted impacts, whereas with the CoM system activated, the UAV maintained a near-level attitude to achieve the upright recovery and greatly reduced structural stress prior to ground contact. The CoG device as a fail-safe stabilizer can also enhance maneuverability by increasing control authority, and enable the faster speed response, and the more efficient in-air braking without reliance on the rotor thrust, and meanwhile it can achieve comprehensive energy saving about 7% of the total power budget. In summary, the roll-stabilization and free-fall results show that the CoM device can work as a practical pathway toward the safer, more agile, and energy-efficient UAV platforms for the civil, industrial, and defense applications.