This study introduces a cost-effective solution and sensor arrays for the multipoint liquid-level measuring sensor based on an intensity modulation technique. The sensor structure is based on the twisting of two fibers and creates cascading to achieve a multipoint detection. Three sensors are fabricated on a single illuminated polymer optical fiber. The twisting creates side-coupling between two fibers, and the coupled power is attenuated when liquid emerges in the coupled region. Each sensor has its own output source, which is connected to the power meter. When the liquid-level increases, the coupled power is continuously decreased. The multipoint liquid-level sensor is theoretical and experimentally tested. The experimental results show that sensors have a good response and linearity. The sensors are able to measure the liquid-level up to 12 cm and have a sensitivity of about 0.2726 μW/cm, 0.1715 μW/cm, and 0.1281 μW/cm, respectively. The different flow rate (50 mL/min–300 mL/min) is also analyzed to validate the dynamic response of the sensor. The sensor demonstrates a high sensitivity and resolution in the liquid-level detection. Meanwhile, the liquid-level variation is individually and simultaneously measured. The system does not require any decoupling technique as the system relies on a single LED source, and the coupled power is individually measured from each power meter. The system represents a significant advancement in precise liquid-level sensing technology, as the system has advantages of a flexible, durable, cost-effective, and active response with respect to changes in the liquid-level.

The paper presents the research progress on the disturbance rejection of Micro Air Vehicle (MAV) in Atmospheric Boundary Layer (ABL) area. The reaction torque of a bio-inspired reaction wheel mechanism inspired by active flight stabilization of Manduca sexta is applied to attenuate the disturbance resulted from unsteady flow fields. The advantage of using this mechanism is to help to recover the MAV posture quickly by applying reaction torque to attenuate the perturbed angle of the coaxial helicopter MAV flying in unsteady wind environments. Another advantage of adopting reaction wheel in coaxial helicopter is that it will replace traditional stabilizer bar or flyer bar to greatly stabilize flying attitude as well as to reduce the structure complexity and volume size induced by stabilizer bars or flyer bars. In this paper, we start to study the dynamic model and disturbance reject performance of stabilizer bar on the micro helicopter. To compare with stabilizer bars, the wind resistance reaction wheels were designed and a novel bio-inspired coaxial helicopter structure with the reaction wheel stabilization mechanism is presented. In addition, its nonlinear and linear dynamic models are derived by Lagrange method. Based on the established models, the PID controller is designed for reaction wheel stabilization system and dynamic responses of the actively controlled system are then extensively studied through simulations. Preliminary results verify the disturbance rejection and control performance of the bio-inspired reaction wheel stabilization mechanism.

The aerodynamic efficiency of conventional lifting-wing quadrotors is severely constrained by the rigid coupling between fuselage pitch attitude and wing angle of attack (AoA), which prevents the vehicle from maintaining optimal lift-to-drag performance across varying flight speeds. This study presents a novel variable-incidence lifting-wing quadrotor that effectively decouples fuselage attitude from wing aerodynamics. The proposed mechanism incorporates a 143 g lightweight lifting wing and a dual-actuator drive system, with a total structural mass penalty of only 209 g. High-fidelity Computational Fluid Dynamics (CFD) simulations, reveal that the variable-incidence strategy alleviates detrimental rotor-wing interference. Specifically, a fuselage pitch of − 20° combined with a wing AoA of 10°–12° reestablishes a strong suction peak on the wing’s upper surface, maximizing passive lift. Systematic flight experiments validate the decoupling control strategy, demonstrating that the prototype achieves a maximum normalized power-saving ratio of 42.98% at 10 m/s relative to hover. Furthermore, even when accounting for the 209 g structural weight penalty, the design provides a net 13.22% efficiency improvement over the fixed-incidence concept of the original RflyLW. Leveraging these aerodynamic enhancements, predictive analyses indicate that the UAV can achieve an extended maximum flight endurance of 46.8 min and a practical range of 28.1 km. These results, showing high consistency between numerical predictions and experimental data, offer a robust and highly efficient solution for extending the endurance of UAVs in energy-constrained environments.