Search Results (307)

This paper proposes a novel hierarchical control architecture that combines Model Predictive Control (MPC) with Explicit Model-Following Control (EMFC) to enable accurate and efficient trajectory tracking for quadrotor electric Vertical Takeoff and Landing (eVTOL) aircraft operating in urban environments. The approach addresses the challenges of strong nonlinear dynamics, multi-axis coupling, and stringent safety constraints by separating the planning task from the fast-response control task. The MPC layer generates constrained velocity and yaw rate commands based on a simplified inertial prediction model, effectively reducing computational complexity while accounting for physical and operational limits. The EMFC layer then compensates for dynamic couplings and ensures the rapid execution of commands. A high-fidelity simulation model, incorporating rotor flapping dynamics, differential collective pitch control, and enhanced aerodynamic interference effects, is developed to validate the controller. Four representative ADS-33E-PRF tasks—Hover, Hovering Turn, Pirouette, and Vertical Maneuver—are simulated. Results demonstrate that the proposed controller achieves accurate trajectory tracking, stable flight performance, and full compliance with ADS-33E-PRF criteria, highlighting its potential for autonomous urban air mobility applications. Full article

This paper addresses the problem of loss of control during flight caused by failures of flight control surfaces. It presents a study of an emergency thrust control system based on linear-quadratic control with integral action. The research encompasses an analysis of thrust modulation control characteristics, a review of existing control systems, and a detailed description of the development process, including the research platform configuration, identification of the aircraft state-space model, control law design, integration of system components within the MATLAB and Simulink environment, and software-in-the-loop testing conducted in the X-Plane 11 flight simulator using a Boeing 757-200 model. The study also investigates the issue of control channel cross-coupling and its impact on simultaneous control of the aircraft’s longitudinal and lateral dynamics. The simulation results demonstrate that the proposed emergency system provides adequate controllability, with settling times of approximately 12 s for achieving a flight path angle setpoint of +5°, and 13 s for attaining a maximum (limited) roll angle of 20°, achieved in separate manoeuvres. Furthermore, simulated landing attempts suggest that the system could potentially enable successful landings at approach speeds significantly higher than standard recommendations. However, further investigation is required to address decoupling of control channels, ensure system stability, and evaluate control performance across a broader range of aircraft configurations. Full article

Modern aircraft increasingly utilizes highly integrated electronic equipment, driving continuously increasing heat dissipation demands. Vapor compression refrigeration systems demonstrate stronger alignment with future aircraft thermal management trends, leveraging their superior volumetric cooling capacity, high energy efficiency, and independence from engine bleed air. This paper reviews global research progress on aircraft vapor compression refrigeration systems, covering performance optimization, dynamic characteristics, control strategies, fault detection, and international development histories and typical applications. Analysis identifies emerging challenges under large-temperature-range cooling requirements, with comparative assessment establishing zeotropic mixture auto-cascade vapor compression refrigeration systems as the optimal forward-looking solution. Finally, recognizing current research gaps, we propose future research directions for onboard auto-cascade vapor compression refrigeration systems: optimizing refrigerant mixtures for flight conditions, achieving efficient gas-liquid separation during variable overloads and attitude conditions, and developing model predictive control with intelligent optimization to ensure reliability. Full article

The traditional approach that separates remaining useful life prediction from maintenance strategy design often fails to support efficient decision-making. Effective maintenance requires a comprehensive consideration of prediction accuracy, cost control, and equipment safety. To address this issue, this paper proposes a multi-objective maintenance optimization method based on stochastic modeling. First, a multi-sensor data fusion technique is developed, which maps multidimensional degradation signals into a composite degradation state indicator using evaluation metrics such as monotonicity, tendency, and robustness. Then, a linear Wiener process model is established to characterize the degradation trajectory of equipment, and a closed-form analytical solution of its reliability function is derived. On this basis, a multi-objective optimization model is constructed, aiming to maximize equipment safety and minimize maintenance cost. The proposed method is validated using the NASA aircraft engine degradation dataset. The experimental results demonstrate that, while ensuring system reliability, the proposed approach significantly reduces maintenance costs compared to traditional periodic maintenance strategies, confirming its effectiveness and practical value. Full article

The terminal maneuvering area (TMA) serves as a critical transition zone between upper enroute airways and airports, representing one of the most complex regions for managing high volumes of arrival and departure traffic. This paper presents the multi-route TMA scheduling problem as an optimization challenge aimed at optimizing TMA interventions, such as rerouting, speed control, time-based metering, dynamic minimum time separation, and holding procedures; the objective function minimizes schedule deviations and the accumulated holding time. Furthermore, the problem is formulated as a mixed-integer linear program (MILP) to facilitate finding solutions. A rolling horizon control (RHC) dynamic optimization framework is also introduced to decompose the large-scale problem into manageable subproblems for iterative resolution. To demonstrate the applicability and effectiveness of the proposed scheduling models, a hub airport—Chengdu Tianfu International Airport (ICAO code: ZUTF) in the Cheng-Yu Metroplex—is selected for validation. Numerical analyses confirm the superiority of the proposed models, which are expected to reduce aircraft delays, shorten airborne and holding times, and improve airspace resource utilization. This study provides intelligent decision support and engineering design ideas for the macroscopic-level collaborative optimization framework of the Integrated Arrival–Departure and Surface (IADS) system. Full article

To address the challenge of evaluating a radar cross-section (RCS) for a non-cooperative aircraft with limited aerodynamic shape information, this paper presents a multi-source, data-driven inverse reconstruction method. This approach integrates data fusion techniques to facilitate an initial shape reconstruction, followed by an iterative optimization process that utilizes computational fluid dynamics (CFD) to enhance the shape, accounting for the aerodynamic performance. Additionally, an inverse deduction analysis is effectively employed to ascertain the characteristics of the power system, leading to the design of a double S-curved tail nozzle layout with stealth capabilities. An aerodynamic analysis demonstrates that at Mach 0.6, the lift-to-drag ratio peaks at 27.3 for the attack angle of 4°, after which it declines as the angle increases. At higher angles of attack, complex flow separation occurs and expands with the increasing angle. The electromagnetic simulation results indicate that under vertical polarization, the omnidirectional RCS reaches its peak as the incident angle is deflected downward by 10° and reduces with the growth of the angle, demonstrating angular robustness. Conversely, under horizontal polarization, the RCS is more sensitive to edge-induced rounding. The findings illustrate that this methodology enables accurate shape modeling for non-cooperative targets, thereby providing a fairly solid basis for stealth performance evaluation and the assessment of surprise effectiveness. Full article

To commercialize supersonic and hypersonic passenger aircraft and reusable spaceplanes, we are developing a small-scale supersonic flight experiment vehicle as a flying testbed for technical demonstrations in high-speed flight environments. This experiment vehicle is equipped with a fuel tank and an oxidizer tank, and the propellants inside the tanks slosh due to changes in acceleration during flight. In this situation, there is a risk of gas entrainment during liquid discharge, which could potentially cause an engine malfunction. To avoid such a situation, we considered installing a propellant management device (PMD) inside the tank to suppress the gas entrainment. In this study, a capillary type PMD with a screen channel structure, commonly used in satellites featuring no moving parts, was adopted due to its applicability to a wide acceleration range. The PMD was designed with a structure featuring cylindrical mesh screen nozzles installed at the top and bottom of a cylindrical tank. A one-dimensional flow analysis model was developed taking into account factors such as the pressure loss across the mesh screens and the flow loss within the mesh screen nozzles, which enabled the identification of conditions under which gas entrainment occurred. In this analytical model, separate formulations were developed using Hartwig’s and Ingmanson’s formulas for evaluating the flow losses through the mesh screens. Furthermore, by applying the flow analysis model, the specifications of the mesh screens as key parameters of the PMD, together with the nozzle diameter and nozzle length, were selected. Moreover, we fabricated prototype PMDs with each nozzle and conducted visualization tests using a transparent tank. The tests were conducted under static conditions, where a gravitational acceleration acted downward, and the effects of the cylindrical mesh screen length and discharge flow rate on the free surface height at which gas entrainment occurred were investigated. This experiment demonstrated the effectiveness of the propellant acquisition mechanism of the present PMD. The height of the free surface was also compared with the experimental and analytical results, and it was shown that the results obtained by using Ingmanson’s formula for pressure loss through the screen mesh were closer to the experimental results. These findings demonstrated the validity of the one-dimensional flow analysis model. Full article

With the increasing demand for drag reduction, energy consumption reduction, and low weight in civil aircraft, high-precision microgroove preparation technology is being developed internationally to reduce wall friction resistance and save energy. Compared to mechanical processing, chemical etching, roll forming, and ultrafast laser processing, nanosecond lasers offer processing precision, high efficiency, and controllable thermal effects, enabling low-cost and high-quality preparation of microgrooves. However, the impact of nanosecond laser etching on the fatigue performance of substrate materials remains unclear, leading to controversy over whether high-precision shape control and fatigue performance enhancement in microgrooves can be achieved simultaneously. This has become a bottleneck issue that urgently needs to be addressed. This paper focuses on the current research status of nanosecond laser processing quality control for microgrooves and the research status of laser effects on enhancing the fatigue performance of substrate materials. It identifies the main existing issues: (1) how to induce surface residual compressive stress through the thermo-mechanical coupling effect of nanosecond lasers to suppress micro-defects while ensuring high-precision shape control of fixed microgrooves; and (2) how to quantify the regulation of nanosecond laser process parameters on residual stress distribution and fatigue performance in the microgroove area. To address these issues, this paper proposes a collaborative strategy for high-quality shape control and surface strengthening in fixed microgrooves, an analysis of multi-dimensional fatigue regulation mechanisms, and a new method for multi-objective process optimization. The aim is to control the geometric accuracy error of the prepared surface microgrooves within 5% and to enhance the fatigue life of the substrate by more than 20%, breaking through the technical bottleneck of separating “drag reduction design” from “fatigue resistance manufacturing”, and providing theoretical support for the integrated manufacturing of “drag reduction-fatigue resistance” in aircraft skins. Full article

In this paper, we propose and prove an innovative radar antenna concept suitable for collision avoidance (CA) systems installed onboard small, unmanned aircraft (UA). The proposed architecture provides 360° monopulse coverage around the host platform, enabling the detection and accurate position estimation of airborne, non-cooperative intruders using lightweight, low-profile antennas. These antennas can be manufactured using low-cost 3D printing techniques and are easily integrated into the UA airframe without compromising airworthiness. We present a Detect and Avoid (DAA) concept of operations (ConOps) aligned with the SESAR U-space ConOps, Edition 4. In this ConOps, the Remain Well Clear (RWC) and CA functions are treated separately: RWC is the responsibility of ground-based U-space services, while CA is implemented as an airborne safety net using onboard equipment. Based on this framework, we derive operation-centric design requirements and propose an antenna architecture based on a fixed circular array of sector waveguides. This solution overcomes key limitations of existing radar antennas for UAS CA systems by providing a wider field of view, higher power handling, and reduced mechanical complexity and cost. We prove the proposed concept through a combination of simulations and measurements conducted in an anechoic chamber using a 24 GHz prototype. Full article

The distributed electric tilt-rotor Unmanned Aerial Vehicle (UAV) combines the vertical take-off and landing (VTOL) capability of helicopters with the high-speed cruise performance of fixed-wing aircraft, offering a transformative solution for Urban Air Mobility (UAM). However, aerodynamic interference between rotors is a new challenge to improving their flight efficiency, especially the dynamic interactions during the transition phase of non-parallel tandem dual-rotor systems, which require in-depth investigation. This study focuses on the aerodynamic performance evolution of the tilt-rotor system during asynchronous transition processes, with an emphasis on quantifying the influence of rotor tilt angles. A customized experimental platform was developed to investigate a counter-rotating dual-rotor model with fixed axial separation. Key performance metrics, including thrust, torque, and power, were systematically measured at various tilt angles (0–90°) and rotational speeds (1500–3500 RPM). The aerodynamic coupling mechanisms between the front and rear rotor disks were analyzed. The experimental results indicate that the relative tilt angle of the dual rotors significantly affects aerodynamic interference between the rotors. In the forward tilt mode, the thrust of the aft rotor recovers when the tilt angle reaches 45°, while in the aft tilt mode, it requires a tilt angle of 75°. By optimizing the tilt configuration, the aerodynamic performance loss of the aft rotor due to rotor-to-rotor aerodynamic interference can be effectively mitigated. This study provides important insights for the aerodynamic performance optimization and transition control strategies of the distributed electric tilt-rotor UAV. Full article

To address the trade-off between safety levels and operational efficiency in the Bay Area, this study proposes a Multi-Stand Grouped Operations method based on deep reinforcement learning under the consideration of the safety domain. The full-process operation of aircraft within the Bay Area is analyzed to identify key operational spots. Safety domains are then established based on path conflicts arising from aircraft movements and safety conflicts caused by minimum separation distances and wake vortex effects. These domains are used to define corresponding safe operating spaces and construct an optimized operational model for the Bay Area. A multi-agent reinforcement learning algorithm is employed to solve the model, deriving an optimized stand allocation plan and Multi-Stand Grouped Operations strategy. To evaluate the effectiveness of the optimization, real flight data from the northwest Bay Area of Terminal 2 at Guangzhou Baiyun Airport are used for validation. Compared to the original stand allocation scheme, the optimized stand allocation and Multi-Stand Grouped Operations strategy reduce aircraft delay times by 62.45%, demonstrating that the proposed model effectively enhances operational efficiency in the Bay Area. Full article

Interference drag in wing–fuselage intersection regions is a complex aerodynamic phenomenon where secondary flows and separation conditions might occur if not properly addressed in the aircraft design. In this work, the optimal shape of the intersection region between the wing and fuselage of a MALE UAV is studied using gradient-based optimization and free-form deformation techniques. High-fidelity fluid computational dynamics solving the RANS equations are employed, together with the corresponding adjoint formulation to compute the gradients of the aerodynamic metrics. Different shape deformation techniques are explored for both the fuselage and wing, and several combinations of design variables are studied. Fuselage shape deformations were found to be more efficient in the removal of the secondary flow near the wing root trailing edge. Reducing the cross-sectional area of the fuselage near the wing leading edge and increasing it near the trailing edge was shown to reduce drag, demonstrating that secondary flow mitigation is more relevant than reduced frontal area. A $2\%$ total drag reduction was obtained by simultaneously shaping both the fuselage and the wing in the intersection region. The optimized wing–fuselage interface remained sharp, without fairings, due to the limitation of the deformation technique to modify the original topology. Full article

With increased electrification of new aircraft designs, cooling becomes more challenging. The most straightforward solution is to activate yet unused heat sinks available in the aircraft. The crown and cabin sidewall are such an unused area suitable for heat transfer. Here, only a thin plate separates the warm cabin from the cold exterior environment in cruise. Air used for the cooling of devices could be guided along the fuselage skin to benefit from the large heat exchanging surface. Scaling test results indicate that up to 24 kW of additional heat could be dissipated in the short term through this system in flight. Full article

The stability of thermal barrier coating (TBC) materials during service is a prerequisite for the normal operation of aircraft engines. The high-temperature corrosion of CaO–MgO–Al₂O₃–SiO₂ (CMAS) is an important factor that affects the stability of TBCs on turbine blades and causes premature engine failure. For traditional 6-8 YSZ, at temperatures of more than 1200 °C, the thermal insulation performance is significantly reduced, which makes it necessary to find new, alternative materials. La₂Zr₂O₇ has good thermal physical properties; the addition of Ce⁴⁺ improves its mechanical properties, while adding Gd₂O₃ affects its corrosion resistance. Herein, high-temperature corrosion studies of (La_1−xGd_x)₂(Zr_0.7Ce_0.3)₂O₇ (L-GZC) (x = 0, 0.3, 0.5, 0.7) ceramic TBC were conducted using CMAS glass at 1250 °C. The results indicate that CMAS rapidly dissolves L-GZC and separates the (La, Gd)₈Ca₂(SiO₄)₆O₂ apatite phase, ZrO₂, and other crystalline phases. These products form a crystalline layer at the contact boundary, which can inhibit further CMAS reactions. Among the coatings examined, the L-GZC ceramic (x = 0.7) exhibits better corrosion resistance, and the penetration depth is <200 μm after high-temperature corrosion at 1250 °C for 5, 10, and 20 h. The failure mechanism and potential risk of CMAS were also analyzed and discussed. The L-GZC ceramic material has good thermal corrosion resistance and is expected to replace the traditional YSZ to better meet the high-temperature working requirements of gas turbines and aircraft engines. Full article

Due to nonlinear aerodynamics, “non-traditional” flight modes may appear in longitudinal and lateral/directional dynamics once an aircraft experiences a high angle of attack and rapid maneuvers. Signal decomposition techniques are required to uncover these modes since they are hidden in flight characteristics. This study represents the Enhanced SynchroSqueezing Transform (ESST) for the extraction of “non-traditional” flight modes from flight data. Developed in the framework of the SynchroSqueezing Transform (SST), the ESST decomposes an Amplitude- and Frequency-Modulated (AMFM) signal into Intrinsic Mode Functions (IMFs). This process is optimized using the Genetic Algorithm (GA). Numerical investigations are performed to confirm the validity of the ESST. Both quantitative criteria for the fitness of the IMFs and qualitative study of the Time–Frequency Representations (TFRs) suggest that the ESST may perform better than the SST in decomposing nonlinear and non-stationary signals. Then, a method is proposed to find the instantaneous characteristics of the flight modes obtained by the ESST. The ESST analyzes an aircraft’s longitudinal and lateral flight data in post-stall maneuvers. The TFRs of flight parameters verify the existence of identical flight modes at different flight conditions. The IMFs are separated, and their instantaneous characteristics are computed. In addition, the ESST modes are compared to conventional modes. The results indicate that the ESST is capable of obtaining both classical oscillatory modes, such as Short Period (SP) and Dutch Roll (DR), and “non-traditional” modes. In the end, coupled modes are identified by comparing longitudinal and lateral IMFs. Full article