Search Results (5)

Foldable wing designs are becoming increasingly popular due to their advantages in the rapid deployment and compact packaging of fixed-wing UAVs, particularly when compared to horizontal take-off and VTOL counterparts. However, selecting an appropriate wing design requires the careful consideration of aerodynamic performance and volume storage constraints. As a result, a trade-off between performance and practicality must be addressed during the conceptual design phase. The primary objective of this study is to identify the optimal wing configuration for a tube-launched foldable wing design. To achieve this, the analysis combine an in-house design tool developed in Excel and XFLR5 v7.01 software. Full article

Foldable wings are designed for tube-launched unmanned aerial vehicles (UAVs), aiming to improve portability and meet launch platform requirements. However, conventional tube-launched UAVs cannot operate across the wide speed ranges required for the performance of multiple missions, due to the fixed configuration of their wings after launch. This study therefore proposes a tube-launched UAV which can change wing-sweep angle to expand the flight speed range and enhance the UAV’s agility. A computational aerodynamics method is employed to assess the transient aerodynamic performance of the UAV during the sweep morphing process. The simulation results indicate that the transient aerodynamic forces generate a dynamic hysteresis loop around the quasi-steady data. The lift and drag coefficients exhibit maximum relative deviations of 18.5% and 12.7% from the quasi-steady data for the sweep morphing period of 0.5 s. The hysteresis effect of the flow structure, rather than the additional velocity resulting from wing-sweep morphing, is the major contributor to the aerodynamic hysteresis loop. Compared to the conventional tube-launched UAVs, the proposed tube-launched UAV with a variable-sweep wing shows a wider flight speed range, from 22.59 to 90.12 m/s, and achieves an 82.84% increase in loitering speed. To verify the effectiveness of the wing-sweeping concept, a prototype was developed, and a flight test was carried out. The test data obtained from flight control system agree well with the simulation data, which demonstrates the feasibility and effectiveness of the variable-sweep wing in widening the speed range for tube-launched UAVs. This work can provide a reference for the design of tube-launched UAVs for wide speed range flight. Full article

This paper describes the design and implementation of a novel three-axis attitude control autopilot scheme for tube-launched, air-deployed UAVs. In early flight tests, various factors, such as model uncertainties during launch, aerodynamic uncertainties, geometric parameter changes during deployment, and significant uncertainties in booster rocket installation, exceeded the control capabilities of the attitude autopilot, causing flight instability. In order to address these issues, a numerical simulation model of the full launch process considering deviations was established based on early flight tests. A cascade attitude controller was then designed using an extended state observer (ESO), and the boundedness of control errors under unknown bounded disturbances was theoretically proven, providing requirements for the parameter tuning of the cascade controller. Comparative experiments and a second flight test both demonstrate that the ESO-based cascade attitude controller exhibits strong feedforward disturbance compensation under high-uncertainty conditions, effectively achieving stable control within the flight envelope. Full article

Unmanned aerial vehicles (UAVs) have already proven valuable for intelligence, search, and reconnaissance missions; however, their integration into manned aircraft to augment existing capabilities is still an emerging field. This paper describes the design of an aircraft that fits inside a G-sized sonobuoy canister, deploys from a manned aircraft in-flight, and flies for up to 111 km and 83 min while providing telemetry to a remote operator. While UAVs with similar performance requirements exist, most were designed to fit in larger canisters. Multiple UAVs can be deployed in the air to expand the search capabilities of manned aircraft, ultimately allowing a larger search area per cost compared to manned aircraft alone. Individual performance characteristics of the aircraft such as aerodynamics, weight, propulsion, and stability were developed in the preliminary design phase based on given performance requirements. The performance of the aircraft was assessed using analytical and empirical methods. Wing folding mechanisms were prototyped for use on the production aircraft for flight testing. Propulsion, aerodynamic, and structural capabilities were validated separately using experimental methods. The folding mechanisms used in this UAV allow it to achieve the benefits of a longer wingspan while remaining compact and easy to deploy. Full article

The motivation behind solving the issue of estimating the flow parameters of the pneumatic system of a launcher was the need to obtain the take-off energy with a value exceeding 80 kJ. The take-off energy and the initial speed of the unmanned aerial vehicle (UAV) depends on the pressure drop time in the launcher’s pneumatic system. The aim of the research was to estimate the flow parameters of the trigger system of the UAV launchers in order to achieve the shortest time of its operation. Due to the lack of a description of the selection of pneumatic elements and their flow characteristics in the available literature, the article attempts to analytically describe the air flow through pneumatic units. The trigger system is described using the sonic conductivity and the critical pressure ratio. Due to the lack of numerical data on the flow parameters of pneumatic units, a test stand was designed and constructed to determine these parameters. The values of the sound conductivity and the critical pressure ratio were determined for each of the pneumatic units and for the entire system. The proposed method makes it possible to determine the relationship between the operating time and the values of the flow parameters of the pneumatic launch tube release system. It also provides guidelines for design and technological solutions for the trigger system of any pneumatic launcher. Full article