This paper proposes a progressive dispersion-based salp swarm algorithm (DSSA) to improve convergence efficiency and solution accuracy in high-dimensional optimization. DSSA extends the multi-chain SSA through a dynamically expanding chain structure, where the number of subgroups increases linearly with iterations to progressively disperse the population. The leader salps' foraging behavior further incorporates the DE/best/1 mutation strategy within a hybrid selection framework, synergizing SSA's chain-driven exploitation with DE's directed global search. Consequently, DSSA exhibits a progressive behavioral transition---operating as multi-chain SSA in early iterations and gradually evolving into a DE-like algorithm upon full dispersion. The algorithm is validated on CEC-2017 benchmark functions against multiple DE variants, SSA variants, particle swarm optimization, and the grey wolf optimizer. Experimental results demonstrate that DSSA achieves superior performance across most test functions, particularly excelling in uni-modal and convex landscapes, while maintaining strong robustness and efficiency for problems with dimensionality exceeding 20.

In nature, the sailfish balances high-speed cruising and agile maneuvering by dynamically adjusting its dorsal fin, providing important biological inspiration for aircraft configuration design. Motivated by this mechanism, this study proposes a bio-inspired morphing-tail aircraft that dynamically switches between high maneuverability and a low-drag, stealth mode via flexible tail deformation. The stochastic scheduling parameter uncertainties inherent in such systems are addressed by rigorously quantifying them through Polynomial Chaos Expansion (PCE) combined with Galerkin projection. An average dwell time switching control strategy is further introduced to stabilize the PCE-based augmented system during multimodal configuration morphing. The augmented system incorporates the variance and higher-order moments of the original system state, guaranteeing the mean-square stability of the morphing-tail aircraft. Finally, numerical simulations show that the proposed framework can accurately quantify the impact of scheduling parameter uncertainty and effectively guarantee aircraft stability.

Visual odometry (VO) plays a crucial role in autonomous driving, robotic navigation, and other related tasks by estimating the position and orientation of a camera based on visual input. Significant progress has been made in data-driven VO methods, particularly those leveraging deep learning techniques to extract image features and estimate camera poses. However, these methods often struggle in low-light conditions because of the reduced visibility of features and the increased difficulty of matching keypoints. To address this limitation, we introduce BrightVO, a novel VO model based on Transformer architecture, which not only performs front-end visual feature extraction, but also incorporates a multi-modality refinement module in the back-end that integrates Inertial Measurement Unit (IMU) data. Using pose graph optimization, this module iteratively refines pose estimates to reduce errors and improve both accuracy and robustness. Furthermore, we create a synthetic low-light dataset, KiC4R, which includes a variety of lighting conditions to facilitate the training and evaluation of VO frameworks in challenging environments. Experimental results demonstrate that BrightVO achieves state-of-the-art performance on both the KiC4R dataset and the KITTI benchmarks. Specifically, it provides an average improvement of 20% in pose estimation accuracy in normal outdoor environments and 25% in low-light conditions, outperforming existing methods. This work is open-source at https://github.com/Anastasiawd/BrightVO.

This work investigates the two-scale design optimization of graded plates with variable-height parallelogram microstructures based on asymptotic homogenization. First, updated unit cell problems, with an emphasis on rotational degrees of freedom, are proposed to evaluate shell-structured microstructures, so that a pointwise effective stiffness calculation can be efficiently conducted with shell elements, which is otherwise computationally prohibitive with solid elements. Then, a two-scale optimization framework seeking minimum compliance is established, where the design variables controlling both in-plane parallelogram shape and out-of-plane stiffener height are introduced to enlarge the design space. In addition, mapping functions are integrated into the optimization formulation and concurrently optimized, enabling the production of well-defined dehomogenized plates. Finally, numerical examples are presented to validate the effectiveness and correctness of the proposed method by comparing the deflections of the graded plates with those of the homogenized plates.

This work investigates asymptotic homogenization method (AHM) for axially graded beams that are mapped from periodic ones. The unit cell problems, the homogenized constitutive and governing equations are first established theoretically. Then a novel FE formulation of unit cell problems and effective stiffness, distinct from that of the periodic beams, is derived and resolved for solid elements. Besides, to improve analysis efficiency, an updated concise formulation is acquired for shell elements with proper handle of in-plane rotational DOFs, and a MATLAB code is presented to show implementation details. At last, four numerical examples show the correctness of the proposed method.

In this paper, a trajectory inverse realization algorithm is proposed. The effect of trajectory is related not only to the controller design but also to the tracking command design. If the tracking command is not designed properly, tracking cannot occur within the control capability. Therefore, the feasibility of the design reference command must be verified before the controller design. To solve this problem, this paper proposes a trajectory inverse realization algorithm and applies this algorithm to hypersonic vehicle climbing trajectory analysis. By using this algorithm, the control quantity corresponding to the flight trajectory can be obtained, and the feasibility of the designed trajectory can be determined by combination with the corresponding control constraints. According to the trajectory characteristics of the hypersonic vehicle, the conventional state error is converted to the error of the differential state variable, and the control variable needed for the design of the climbing trajectory is obtained through an iterative solution of the Newton-Raphson method. Finally, the effectiveness of the trajectory inverse algorithm considering control constraints is verified by simulations.

To optimize graded lattice structures with spatially graded geometrical characteristics and promote the rational distribution of finite materials in macrostructure, a two-scale concurrent topology optimization method combining dynamic clustering is proposed. Dynamic clustering strategy is developed to group microstructures, which means that the clustering pattern will be updated according to the current strain energy during the whole iterations and obtains a more reasonable microstructures’ distribution than the static partition. Further, rotational degree of freedom is introduced to make sure that the microstructures are oriented along principal stress directions, so as to obtain a more reasonable load transfer path. Numerical examples show that, compared with the traditional static partition method, this method can more effectively distribute materials, make full use of the anisotropic of lattice structures, and improve structural performance.

Based on the discrete T-S fuzzy system, this paper deals with investigating the trajectory tracking control of high-altitude long-endurance aircraft (HALE) under gust disturbance. Suitable operating points within the envelope range are selected to establish the T-S fuzzy model of highly flexible aircraft (HFA). In order to reduce the conservativeness of the closed-loop system, the continuous T-S fuzzy system is discretized to establish a discrete T-S fuzzy system model. Moreover, considering the tracking target and the robust performance, a Discrete Fuzzy Robust H∞ Control (DFRHC) strategy is proposed, which mainly includes two parts: the fuzzy feedforward control part for reference tracking control and the fuzzy feedback control part to provide robustness. Setting the flight speed and altitude as the tracking target, numerical simulations are performed to verify the control performance of DFRHC strategy based on the T-S fuzzy model. In the tracking control process, discrete gust and the influence of the saturation constraint of control actuator are considered. Simulation results show that the DFRHC strategy based on the T-S fuzzy model can achieve effective tracking control of HFA within the envelope.

Helically wound structures are widely used in practical engineering due to its excellent mechanical property, such as the steel rope, the reinforced armor layer of the marine flexible pipe/cables. The shear stiffness plays an important role in exactly predicting the mechanical response of the helically wound structure, especially for the short structure. There has been no general methodology to directly calculate the shear effect of this type of structure because of the geometrical complexity. This paper introduces and modifies a novel implementation of asymptotic homogenization method so-called NIAH to effectively calculate the shear property of the helically wound structure. This modification of NIAH is derived based on the strain energy equivalence of the macroscopic structure and the microscopic structure so-called the microscopic unit cell, which can be used to quickly calculate the effective stiffness and effective stress. In this paper, the effective stiffness is only discussed. The mechanical mechanism of the shear effect of helically wound structures is firstly explained, and then taking into account the shear effect, a quickly effective analysis method of the mechanical response for the helically wound structure is proposed. The efficient and accurate finite-element model of the unit cell which is used in the numeric implementation of the effective analysis method, is determined through the sensitivity analysis of meshing methods and periodic boundary conditions. Considering the practical application, the implementation of this method is validated for helically wound structures with equal-scale subcomponents and non-equal-scale subcomponents. The influence of the slenderness ratio on the shear effect is also explored in this work. This study provides a meaningful reference for the loading analysis and structural design of helically wound structures.

Spatially graded heterogeneous plate structures that are mapped from periodic plates based on mapping functions are attracting increasing attention due to their excellent mechanical performances and high tailorability, and homogenization approaches are a powerful tool for their efficient numerical analysis. In this work, based on asymptotic homogenization, a unified framework of the effective properties prediction and the corresponding unit cell problems is first theoretically established for spatially-varying plates with arbitrarily-shaped microstructures, which are distinct from those of periodic plates due to the Jacobian of mapping functions. Moreover, the FE formulation for efficient numerical implementation are also proposed for not only solid elements, but also shell and beam elements, where numerical treatment details in stiffness matrix formulation and periodic boundary conditions are elaborated, so that highly efficient effective stiffness computation can be achieved for thin-walled heterogeneous plate structures. At last, unit cells under different Jacobian matrices, which are related to different kinds of geometric deformation patterns, and two spatially graded plates are analyzed to corroborate the correctness and efficiency of the proposed method.

Bi-layer lattice-filled sandwich structures have good application prospects for multi-physics problems; however, high-precision numerical analysis methods are lacking. Recently, the newly proposed asymptotic homogenization method called the novel numerical implementation of asymptotic homogenization (NIAH) was further developed based on the Mindlin plate theory, which is a potential method for overcoming the above limitation. This study investigates the feasibility of this method for Bi-layer lattice-filled sandwich structures. The obtained results are compared to those from homogenization methods developed based on the Kirchhoff theory, and accordingly, the influence of the shear effect on the accuracy of the structural responses of the considered structures is studied. Subsequently, the impacts of the size effect, macrostructure type, and lattice type are also considered. The analysis results showed that, for most cases, the NIAH method can yield high-precision results for Bi-layer lattice-filled sandwich structures. When the number of lattice cells is insufficient or different layers of the lattice have excessive differences in their stiffness, the accuracy of the results obtained using the NIAH method is degraded.

Surrogate-assisted evolutionary computation have received much more attention in the field of optimization because of its ability to reduce effectively the CPU cost. However, as the dimension of the search space increases, the number of samples required to construct the global accurate surrogate model will increase exponentially. In order to improve the computational efficiency for achieving high-precision optimization in high-dimensional search space, an adaptive dynamic surrogate-assisted evolutionary computation approach based on variable search region is presented in this paper. The basic idea of the present method is to abandon the high accurate approximation of surrogate model on the global search space which requires a large number of samples, but focus on the search of the smaller local region where the optimal solution is located. Then refine the samples to construct a higher-precision local surrogate model on the smaller local search region, which moves with the movement of the current optimal solution. Numerical experiments show that the highly accurate optimal solution can be obtained by less than five times of adaptation. It is also applied successfully to the aerodynamic shape design optimization of transonic airfoil and wing, and the results show that present adaptive approach greatly improves the computational efficiency by about ten times compared with the traditional static global approximation surrogate model. • A dynamic adaptive surrogate model based on variable search region is presented. • Computational efficiency is improved by about ten times. • It is also valid for optimization problems without knowing the search space. • It is successfully applied to aerodynamic shape optimization.

This paper presents a novel two-step homogenization-based topology optimization and de-homogenization method for the design of graded lattice structures. The lattice orientation and material layout are first optimized for square base cells in the macro scale. Then by introducing the lattice stretching design variables of micro base cells, which bridge the base cell distortion with lattice stretch, the error residual of mapping functions is integrated with compliance formulation to form a novel mixed optimization formulation, concurrently optimizing structural performance and mapping functions. The advantage of this formulation is two-fold. First, the micro design space is relaxed from square base cells to rectangular ones so that performance improvement is further expected. Second, an excellent agreement, in both shape and performance, between the projected singlescale lattice structures with the homogenization results is secured, as compared to the frequently adopted postprocess procedure of constructing single-scale lattices, where performance deviation could arise for specific microstructural patterns. With the optimized mapping functions, de-homogenization procedure is carried out to construct single-scale spatially graded lattice structures, where a simple filter-projection operation is proposed to obtain fine-scale smoothed boundaries from coarse-scale homogenization results with zig-zag boundaries. Several numerical examples are presented and compared with conventional post-process treatment results to show the validity of the proposed method, and different kinds of lattice patterns adopted in this work show its versatility for a broad range of lattice patterns.

This paper deals with investigating the closed-loop stability boundary of the highly flexible aircraft with structural flexibility and input saturation constraint. A method is presented to analyze the stable region based on the system features of the open-loop instability. In this paper, a dynamic model of highly flexible aircraft is made and the dynamic characteristics are analyzed and the long period mode and stability are investigated in terms of the trimmed model. Considering the saturation constraint of elevator deflection, the closed-loop stability boundary of the system under saturation constraint is discussed by combining the open-loop instability features of highly flexible aircraft. The analysis indicates that the boundary is related to the left eigenvector consistent with the amplitude constraint and the unstable poles of the control signals. Based on the long period instability of the aircraft, the formula of closed-loop stability boundary is analytically obtained. The convergence region of highly flexible aircraft is verified in terms of the LQR controller. The influence of structural flexibility and saturation constraint amplitude of elevator on the stability boundary of highly flexible aircraft is analyzed based on state constraints, which is also compared with the rigid aircraft. The simulation results show that the closed-loop stability of the system is restricted by the open-loop characteristic of the system and the control input saturation constraint.

In this work, a method has been presented to analyze the influence of control saturation and structural flexibility on the stable radius of highly flexible aircraft. A dynamic model of aircraft is constructed followed by the analysis of kinetic characteristics. In this paper, the closed-loop stability boundary of highly flexible aircraft with open-loop instability is studied. The amplitude limit and bandwidth limit of the control signal are considered in the closed-loop stability boundary calculation. Our analysis shows that the boundary is related to the left eigenvector corresponding to the unstable poles and the amplitude constraint of the control signals. Stability of the boundary of feedback control system further reduces the limitation of the bandwidth of actuators. Focused on the phugoid instability of highly flexible aircraft, computational formulation of the closed-loop stable boundary is achieved. The Monte Carlo analysis has been employed to validate the stable region, under the LQR controller. Both the theory and simulations have nice correlations with each other which verify the stability of the closed-loop system, restricted by the open-loop system, and the influence of control signal bandwidth constraints.

The hypersonic vehicle has problems with multiple systems coupling and multivariate design. Hence, it is difficult to determine the surrogate model structure of the hypersonic vehicle under larger samples. To solve this problem, this paper proposes a surrogate model structure optimization method based on the idea of PIO algorithm. The method can independently search for a polynomial surrogate model structure that satisfies the accuracy and prediction performance requirements. Through comparative analysis, utilizing this method outperforms Davidson’s genetic programming algorithm. Furthermore, it was applied to the global aerodynamic data fitting and control design of a hypersonic vehicle, and the simulation results reveal that the error of the prediction data obtained by this method was less than 5%, which has a good fitting effect and can meet the engineering application requirements.

基于滑模控制策略,研究了折叠翼飞行器辅助机动问题.分析了系统折叠角与气动参数的关系,把机翼折叠角看成额外的控制输入,构造了包含折叠辅助机动的飞行器动力学模型.针对非线性系统,加入混合干扰,设计了非奇异动态终端滑模控制(NDTSMC)器,能够较好地抑制折叠翼飞行器的不确定性,同时完成姿态跟踪控制.仿真结果表明,NDTSMC改善了折叠翼飞行器的控制精度和鲁棒性能,具有较好的抖振消除效果.与传统飞行器相比,加入折叠辅助机动的折叠翼飞行器拥有更高的机动性和抗干扰能力.

Structural topology optimization (Bendsøe and Kikuchi, 1988; Bendsøe and Sigmund, 2003; Deaton and Grandhi, 2014; Cheng and Olhoff, 1981; Xie and Steven, 1993) [1–5] provides a numerical tool for structural design with optimum performance. However, these structures could be too complex to be fabricated. Additive manufacturing (AM) enables the fabrication of these complex structures and is perfectly suitable for realizing the full potential of TO. However, AM has its manufacturing constraints too. The overhang constraint is one of these constraints. Components with small overhang angles or hanging features may deform, droop or warp, when fabricated using laser or electron beams in a layer-wise manner. This paper proposes a new approach to obtain optimum structural topology with consideration of the overhang constraint. We develop an effective method to estimate structural boundary normals of the optimum and intermediate designs with zigzag and blurry boundaries in SIMP by fitting local element density distribution with linear surfaces. By controlling the horizontal length of structural component, the hanging feature and too thin component are effectively suppressed. The element-wise overhang angle constraints and hanging feature constraints are aggregated as two single constraints on the volume fraction of the elements that violate these element-wise constraints. The structural topology optimization problem is solved by MMA. Numerical examples are given to demonstrate the effectiveness of the proposed algorithm.

Objectives: To evaluate the efficacy and safety of pre-operative Halo-gravity traction in the treatment of severe neurofibromatosis type 1 and congenital scoliosis patients with thoracic rotatory subluxation. Patients and methods: Patients with neurofibromatosis type 1 and congenital scoliosis undergoing Halo-gravity traction were reviewed. Radiographic parameters were measured at pre-, post-traction and post-operation. The forced vital capacity and forced expiratory volume in 1 s were recorded at pre- and post-traction. The neurologic function were assessed according to the Frankel score. The complications during Halo-gravity traction, operation and post-operative follow-up were recorded. Results: A total of 35 patients (21M and 14F) with rotatory subluxation including 18 neurofibromatosis type 1 and 17 congenital scoliosis patients were included, of whom the average age was 14.9 +/- 4.8 years. The average duration of Halo-gravity traction was 72.3 +/- 11.2 days, during which the average Cobb angle improved from 105.4 +/- 34.2 degrees to 81.7 +/- 32.6 degrees (P < 0.001), and the global kyphosis decreased from 79.2 +/- 22.5 degrees to 59.7 +/- 23.0 degrees (P = 0.003). At pre-traction, the values of coronal and sagittal rotatory subluxation were 9.3 +/- 5.2 mm and 7.5 +/- 3.5 mm, which significantly improved to 6.7 +/- 3.6 mm (P < 0.001) and 4.9 +/- 2.3 mm (P < 0.001), respectively. The average improvement in forced vital capacity and forced expiratory volume in 1 s were from 43.6% to 54.2% predicted and from 40.4% to 48.8% predicted, respectively. After Halo-gravity traction, the Frankel scores improved from C to D in 3 patients, from D to E in 2 patients. Conclusion: Halo-gravity traction can improve the coronal and sagittal curvature, and the rotatory subluxation in neurofibromatosis type 1 and congenital scoliosis patients. The pre-operative Halo-gravity traction is a safe option for severe neurofibromatosis type 1 and congenital scoliosis patients with rotatory subluxation.

For the control system of the hypersonic vehicle longitudinal dynamics model, an anti-saturation controller is implemented when the control input is over-saturated for a strong disturbance. To solve the tracking control problem of nonlinear systems with disturbance under control constraints, an anti-saturation robust controller based on feedback linearization is proposed. First, the nonlinear mathematic model is linearized via exact feedback linearization, and then the closed-loop gain designed by the robust control algorithm to tracking control with disturbance. According to the robust control theory, the better the anti-disturbance performance of the designed robust controller is, the easier the actuator will enter the over-saturation state when the aircraft is under strong disturbance. To solve this problem, an anti-saturation compensation element is designed by using the gain matrix feedback anti-saturation theory. When the actuator exceeds the saturation boundary, the compensator will modify the control output. Simulation analysis shows that the flight control system with the additional anti-saturation element can restrain the actuator over-saturation and improve the control capability under large disturbance.