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This paper examines a Distributed Propulsion (DP) concept and involves CFD verification, optimisation and evaluation. The first part of the study validates the employed simulation methods using experimental data from the NASA Workshop for Integrated Propeller Prediction (WIPP) and the Folding Conformal High Lift Propeller (HLP) project, for isolated and installed cases under various conditions. Additionally, validation for rotor-rotor interactions was also conducted using the GARTEUR Action Group 26 measurements. The second part of the paper examines installed propeller configurations to identify performance differences based on their position relative to a lifting wing. The results indicate that distributed propellers with small radii interfere more with the wing, than tip-mounted, large propellers. Additionally, propeller and wing performance vary with respect to the propeller installation location. The propeller in tractor configuration showed higher efficiency than the over-the-wing (OTW) configuration by about 7%. However, results from this work showed a 2% improvement in the propeller efficiency when the OTW configuration had a pylon installed. This study also found that optimising the propeller from a tractor to OTW configuration, significantly improved the wing performance. At take-off and landing, the Lift-to-Drag (L/D) ratio of the OTW configuration almost quadrupled, and the overall propulsive efficiency increased by about 5%. The simulations showed that the OTW configuration with different numbers of propellers, outperformed the tractor configurations with the same number of propellers. Furthermore, up to 26% improvement in lift and overall propulsive efficiency was found by introducing the DP system in the OTW configuration. [ABSTRACT FROM AUTHOR]

For the integrated design of the forebody and hypersonic inlet, the non-uniform inflows generated by the forebody have significant impacts on the inlet performance. Traditional inlet designed by the Internal Conical Flow C (ICFC) flowfield or Method of Characteristics (MOC) flowfield, is difficult to match non-uniform inflows, which can easily lead to reduced captured flow and total pressure recovery. Hence, this paper proposes a novel design method for inward-turning inlets to overcome these problems. The key of this method is the parent flowfiled called the Internal Conical Flow N (ICFN). A multi-objective design optimization is integrated into the design of the two-dimensional ICFN flowfield, which enables the "design-optimization" to implement simultaneously. The new ICFN flowfield makes full use of the high compression effect and avoids the existence of Mach reflection at the focal point. Complete details of the design method of ICFN flowfield and inward-turning inlet are presented. The flowfield structure of ICFN flowfield and inlet are analyzed. Numerical simulation results indicate that the new inward-turning inlet can effectively increase captured flow and total pressure recovery. This reveals that the design method gained here can be usefully applied to the design of high-performance inward-turning inlets. [ABSTRACT FROM AUTHOR]

This paper investigates the stability control of the tethered multi-rotor unmanned aerial vehicles (T-MRUAVs) system in cargo delivery, where precise payload trajectory control is deemed unnecessary, with a focus on enhancing controller simplicity and robustness. To achieve this objective, it is imperative to employ an optimal formation tracking control, ensuring not only the symmetrical positioning of UAVs concerning the payload but also the achievement of distributed optimal solutions. Therefore, a formation tracking control strategy based on differential graphical games is designed to ensure optimized performance metrics and minimized suspended load swing. The designed control framework includes an outer loop and an inner loop control, which respectively achieve formation tracking and attitude stability. In addition to maintaining equilibrium states, each UAV is required to track the desired trajectory. Consequently, the formation tracking control consists of a gravity compensation term at the equilibrium point and a formation tracking control term based on differential graphical games. Then, a PID control strategy is displayed for the inner loop control, and the altitude control adopts feedback linearization. Finally, numerical simulations have validated the effectiveness of the designed algorithm. [ABSTRACT FROM AUTHOR]

Test duration in gun tunnels is on the order of several milliseconds, so its extension is crucial for easier and more accurate experimental measurement. However, there is a lack of reported work on the physical mechanisms governing the test time in gun tunnels. To address this issue, this paper explored the influence of the length of the driver section (L 4), the driven section (L 1), and the pressure ratio (P 4 /P 1) between the driver and the driven section on the test time of gun tunnels through numerical simulations. It is found that the starting point of test time is related to the moment of the 4th shock wave arrival, and the end point corresponds to the event of piston or expansion wave arrival, depending on which one happens first. Furthermore, in order to obtain the maximum test time for a gun tunnel, the ratios of the length and the pressure between the driver and the driven section need to be adjusted so that the piston and the expansion waves can arrive at the end of the driven tube simultaneously. When L 4 /L 1 and P 4 /P 1 is larger than the optimal value, the piston reaches the end of the driven tube faster than the expansion waves. This is because the velocity of the piston is higher while that of the expansion waves is basically unchanged at larger P 4 /P 1. In addition, the distance for the expansion waves to travel is longer at bigger L 4. On the contrary, when L 4 /L 1 and P 4 /P 1 is smaller than the optimum, the expansion waves hit the end of the driven section before the piston. [ABSTRACT FROM AUTHOR]

An integrated attitude and orbit finite-time control based on anti-unwinding twistor representation for flying-around with non-cooperative target is proposed in this paper. Firstly, an integrated attitude and orbit model based on traditional twistor representation is established for non-cooperative flying-around problem with complex initial situation. Secondly, an anti-unwinding representation is proposed to avoid the unwinding phenomenon. Thirdly, a finite-time controller in the framework of the anti-unwinding twistor representation is designed to guarantee the spacecraft to reach the desired state quickly. Finally, the effectiveness of the proposed method is verified by numerical simulations. [ABSTRACT FROM AUTHOR]

Bypass dual throat nozzle (BDTN) is a new kind of fluidic thrust vectoring nozzle that can provide thrust vectoring by controlling self-adaptive flow. In this paper, BDTN-tab is proposed to improve the mixing ability of the nozzle. It is defined as a new kind of BDTN with an outlet modified by a pair of tabs. Under the premise of ensuring the nozzle outlet projected area remains unchanged, the pair of tabs coplanar with the convergent section of the cavity is designed to be. This design takes aerodynamic performance, thrust vectoring performance and mixing ability into account. Conclusions can be drawn through theoretical analysis, design, numerical simulation and wind tunnel experiments: The BDTN-tab can produce a thrust vectoring angle by opening the bypass valve, which can reach an extreme angle of 32°. As the tab angle increases, the thrust coefficient and thrust vectoring angle of the nozzle decrease. However, the vortex intensity at the nozzle outlet increases and can enhance the mixing between primary flow and external flow. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of integrated guidance and control (IGC) law design with impact angle and general field-of-view (FOV) constraints. Firstly, the IGC model for intercepting non-maneuvering moving target is parameterized by state-dependent coefficient matrices. The nominal IGC law for intercepting the target with the desired impact angle is obtained by solving the state-dependent Riccati equation. Secondly, since the relative degrees of the general FOV constraints with respect to the IGC model exceed one, the high-order control barrier functions are constructed. The satisfaction of the FOV constraints is equivalent to ensuring that the superlevel sets defined by the barrier functions are forward invariant, which is converted into affine constraints on the control input. The nominal IGC law is modified in a minimally invasive way by quadratic programming. Then, the proposed method is extended to the case of intercepting maneuvering target by leveraging a relative coordinate frame. Finally, numerical simulations are conducted to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents an improved process for the modeling, model order reduction (MOR), and control design of a flexible flying wing unmanned aerial vehicle based on the linear parameter-varying (LPV) technology. By applying the Lagrangian formulation and doublet lattice method, the aeroservoelastic (ASE) model of the flexible aircraft is first derived and then rewritten as an airspeed-dependent LPV system, which consists of rigid-body states, structural modes, aerodynamic states, etc. This leads to a high-order LPV model, and the stability of the system varies from stable to unstable when the speed of the aircraft exceeds the critical flutter speed. To facilitate the control design, an oblique projection-based MOR method is then adopted to reduce the order of the plant. Different from previous studies, the MOR method is improved to systematically generate a reduced-order LPV model with consistent states for both the stable and unstable dynamics parts. Finally, an output-feedback LPV controller is designed to simultaneously achieve the body freedom flutter suppression and longitudinal attitude control. Numerical simulation results show the effectiveness of the improved LPV-based ASE modeling, order reduction, and control design process for the flexible aircraft. [ABSTRACT FROM AUTHOR]