Aerospace Systems最新文献

This paper proposes a finite-time stable chattering-free output feedback control method for rigid satellites equipped with single gimbal control moment gyro (SGCMG) actuators, considering dynamic uncertainties and external disturbances. The dynamics of a rigid satellite are first represented using the modified Rodrigues parameter (MRP) explanation, and then transformed into Lagrangian state space affine form. Because of cost or technical restrictions, angular velocity data are not always accessible for practical application. So angular velocity is considered to be unmeasurable. In order to avoid increasing mathematical calculations and designing separate observers to estimate external disturbances and system states with finite time convergence, a fast third-order sliding mode state observer has been used to simultaneously estimate disturbances and system states. The main part of the proposed controller is also composed of the fast non-singular terminal sliding mode method, which is a combination of linear sliding mode and terminal sliding mode and guarantees finite-time stability and elimination of chattering phenomenon. For the computation of inverse of Jacobian matrix, off-diagonal singularity robust steering algorithm has been used that capable of escaping any kind of singularities. The stability of the proposed method and the simulation results of the proposed method have been presented and compared with the results of the methods available in the literature, which shows the efficiency of the method proposed.

The electrical actuator is usually used in the navigation and control system of the hypersonic aircraft, and it can be described by a multi-body dynamical system, which contains brushless motor, gear pairs, ball screw, folk, rudder, etc. For such a complex multi-body system, it may contain clearance between the mating components, such as the gear pairs, the nut of the ball screw and the folk. Additionally, the discontinuous friction force is introduced due to the friction sheet between the folk and the rudder shaft. Since the working temperature of the electrical actuator for the hypersonic aircraft can be extremely high and time-varying, the stiffness, clearance and friction coefficient will also change during the maneuvering flight of the hypersonic aircraft. In this paper, the ordinary differential equations of each subsystem of the electrical actuation system for the hypersonic aircraft will be developed. The continuous and discontinuous interaction forces between the mating components will be derived. The temperature effects will be considered such that the stiffness, clearance and the friction coefficient of such an actuation system are in the function of the working temperature. The dynamic responses of such an electrical actuation system for different working temperatures will be compared based on the numerical simulations, which shows the evidence that the temperature can reduce the transmission ratio of such a system, as well as affecting the system flutter behavior, through changing the contact position of the adjacent meshing components.

This paper puts forth a new approach for reducing the weight of a fuel cell (FC) powered fixed-wing unmanned aerial vehicle (UAV). The key innovation combines concurrent optimization of the FC and battery sizes along with their power management strategy. A particle swarm optimization (PSO) algorithm is leveraged to perform this concurrent optimization. Through these optimizations, reductions in weight are achieved for both the power sources and fuel tank, while maintaining optimized power output profiles. The optimization results demonstrate significant system weight reductions of 66.87% and 47.72%, for two distinct power profiles that were analyzed. Profile I corresponds to a smooth, continuous power demand over time, while Profile II is a fluctuant profile. In addition to weight savings, the power management optimization reveals an important interplay between the power profile demanded, control strategy, and sizing of the power sources. It was found that the FC is best sized to match the longest duration high power segment of the mission. This power-matched sizing results in stable, efficient operation of the FC over time. Conversely, the battery is sized sufficiently large to meet peak instantaneous power demands that exceed the FC capability. These findings showcase the potential of the proposed optimization approach to facilitate improved performance for electric fixed-wing UAVs. Moving forward, a series of numerical simulations validate the proposed methodology and confirm the deduced results.

Motivated by the difficulty of accurately determining the inflow parameters in icing wind tunnels and flight tests, the Markov Chain Monte Carlo (MCMC) method, a commonly used Bayesian inference method, is explored to solve the inverse problem with the help of an icing software. The icing software, SJTUICE, is used to produce ice shapes for inversion and serves as the prediction tool in the iterations of the inversion problem. The influence of prior estimation of different icing parameters on the convergence and accuracy of the inversion problem is discussed. The feasibility of the MCMC method in inferring the inflow condition in terms of rime ice and glaze ice is assessed. Generally, fast convergence and good accuracy in terms of single inflow parameter inversion can be easily achieved. However, the number of iterations required increases rapidly with the number of inflow parameters in the MCMC method.

The development of flight software for Unmanned Aerial Systems (UAS) is challenging due to the absence of an established development process defined by aerospace certification authorities. This research paper outlines our methods and tools for analyzing flight-critical UAS control software on the target hardware. We present our toolchain and methodology for evaluating the flight control computer stack, runtime memory, and timing characteristics. Additionally, we compare the performance of the flight control computer under various hardware and cache settings to justify, which hardware features should be enabled. The tools and processes employed in this research are deployable to any other development environment and are not restricted to the specific target hardware used in this paper.

Hybrid rocket engines have gathered significant attention due to their ease of use, safety, and affordability associated with traditional chemical propulsion systems. They offer the advantage of on-demand throttle and thrust adjustments. The performance of hybrid rocket engines depends on the regression rate, which is the transition of the solid fuel grain to flammable gas. Unlike solid and liquid engines, hybrids experience varying oxidizer-to-fuel (O/F) ratios over time. Factors such as changes in oxidizer flow and fuel port diameter contribute to this fluctuation, leading to incomplete combustion and reduced efficiency. To enhance hybrid rocket engine performance, ongoing research explores various methods. One approach is increasing the oxidizer flow velocity over the burning fuel surface. This paper employs analytical and numerical techniques to determine the effective oxidizer/fuel ratio for a single-port fuel grain in a hybrid rocket engine. Ultimately, the research aims to optimize performance, allowing this secure and efficient propulsion technology to mature.

This article discusses the challenge of defining the geometry parameters for minimum mass stiffened aircraft panels made of composite materials. The thickness and size of the panel elements are unknown variables, and the optimal design is based on the condition of equal buckling. To solve this problem, the authors reduce the optimal design problem to the investigation of the weight function with multiple variables using analytical methods and refined buckling theory restrictions. The article introduces novel mathematical relationships for investigating the buckling of structurally anisotropic composite panels. The model couples bending with a plane stress state, resulting in a boundary value problem that involves solving an eighth-order partial differential equation within a rectangular field. To facilitate this, a software package was developed using the MATLAB operating environment. A set of computer programs was created to conduct multi-criteria optimization of the optimal design of structurally anisotropic aircraft composite panels. The study also examines the impact of design parameters on the critical buckling forces for both bending and torsion modes. The results of a new implementation of an optimal size-weight project for carbon-epoxy skin are given. A project with restrictions on the refined buckling theory for structurally anisotropic aircraft panels made of composite materials has been manipulated in terms of plies thicknesses. Optimal solutions are obtained.

The electrical power subsystem (EPS) is one of the most critical subsystems in a spacecraft (SC). It provides the power needed for SC loads. Any failure in the EPS leads to SC mission failure. However, power budget calculation is necessary for the analysis of the energy flow of the SC subsystems for in-orbit nominal operation and to ensure the adequacy of solar array (SA) power and storage battery capacity. The average power generated by SA of a SC should be carefully calculated to accurately estimate the energy budget process. Nevertheless, SC operational scenarios should be designed and then justified by the power budget calculation. The investigation of power capability is to satisfy the mission requirements for all nominal operating modes of the SC. The solar illumination and orbit shadow period, as well as EPS parameters including SA output power, bus voltage, load profile, and storage battery capacity graph during in-orbit nominal operation, are all taken into consideration. In this paper, a mission profile with the worst-case scenario (WCS) for EPS of a Low-earth orbit (LEO) Cube-Sat is demonstrated. Moreover, a novel energy management strategy is developed using artificial intelligence to justify the power budget calculation of SC EPS.

Nonlinear time-varying system, such as a spacecraft formation flying system with chief spacecraft in elliptical orbit and under the effect of perturbation forces, is difficult to analyze, design, and control based on the presence of time-varying parameters. The proper functioning of aerospace systems and their ability to be able to achieve the designed mission objectives depend largely on proper understanding of their nonlinear time-varying nature, dynamics, and ability to keep them in the required mission operation configurations through high-fidelity optimal control strategy. This paper presents nonlinear dynamics and optimal control of (J_2) perturbed spacecraft formation flying. Via Euler–Lagrange approach, the nonlinear (J_2) perturbed motion dynamics was approximated into a time-varying nonlinear form, having periodic coefficients and time-varying parameters, suitable for designing fuel efficient control strategies, spacecraft formation flying, relative motion, and rendezvous mission analysis. Through the application of State-Dependent Riccati Equation (SDRE) approach, the approximated model was converted into a non-unique, pseudo-linear state-dependent coefficient (SDC) form. The numerical simulations confirmed that the SDRE controllers, developed using SDC parameterized systems, are maximally robust and able to return the system to the desired radial, along-track, and cross-track positions.

Considering the complexities of the modern maritime operational environment and aiming for effective safe navigation and communication maintenance, research into the collaborative trajectory tracking problem of unmanned surface vehicles (USVs) and unmanned aerial vehicles (UAVs) clusters during patrol and target tracking missions holds paramount significance. This paper proposes a multi-agent deep reinforcement learning (MADRL) approach, specifically the action-constrained multi-agent deep deterministic policy gradient (MADDPG), to efficiently solve the collaborative maritime-aerial distributed information fusion-based trajectory tracking problem. The proposed approach incorporates a constraint model based on the characteristics of maritime-aerial distributed information fusion mode and two designed reward functions—one global for target tracking and one local for cross-domain collaborative unmanned clusters. Simulation experiments under three different mission scenarios have been conducted, and results demonstrate that the proposed approach possesses excellent applicability to trajectory tracking tasks in collaborative maritime-aerial settings, exhibiting strong convergence and robustness in mobile target tracking. In a complex three-dimensional simulation environment, the improved algorithm demonstrated an 11.04% reduction in training time for convergence and an 8.03% increase in reward values compared to the original algorithm. This indicates that the introduction of attention mechanisms and the design of reward functions enable the algorithm to learn optimal strategies more quickly and effectively.