Search Results (43)

In midcourse guidance, strong constraints and dual-channel control coupling pose major challenges for trajectory optimization. To address this, this paper proposes an optimal guidance method based on terminal relaxation and range convex programming. The study first derived a range-domain dynamics model with the angle of attack and bank angle as dual control inputs, augmented with path constraints including heat flux limitations, to formulate the midcourse guidance optimization problem. A terminal relaxation strategy was then proposed to mitigate numerical infeasibility induced by rigid terminal constraints, thereby guaranteeing the solvability of successive subproblems. Through the integration of affine variable transformations and successive linearization techniques, the original nonconvex problem was systematically converted into a second-order cone programming (SOCP) formulation, with theoretical equivalence between the relaxed and original problems established under well-justified assumptions. Furthermore, a heuristic initial trajectory generation scheme was devised, and the solution was obtained via a sequential convex programming (SCP) algorithm. Numerical simulation results demonstrated that the proposed method effectively satisfies strict path constraints, successfully generates feasible midcourse guidance trajectories, and exhibits strong computational efficiency and robustness. Additionally, a systematic comparison was conducted to evaluate the impact of different interpolation methods and discretization point quantities on algorithm performance. Full article

This paper proposes an integrated control framework for improving the trajectory tracking performance of autonomous ground electric vehicles (AGEVs) under complex disturbances, including parameter uncertainties, and environmental changes. The framework integrates active disturbance rejection control (ADRC) for real-time disturbance estimation and compensation with a deep deterministic policy gradient (DDPG)-based deep reinforcement learning (DRL) algorithm for dynamic optimization of controller parameters to improve tracking accuracy and robustness. More specifically, it combines the Line of Sight (LOS) guidance rate with ADRC, proves the stability of LOS through the Lyapunov law, and designs a yaw angle controller, using the extended state observer to reduce the impact of disturbances on tracking accuracy. And the approach also addresses the nonlinear vehicle dynamic characteristics of AGEVs while mitigating internal and external disturbances by leveraging the inherent decoupling capability of ADRC and the data-driven parameter adaptation capability of DDPG. Simulations via CarSim/Simulink are carried out to validate the controller performance in serpentine and double-lane-change maneuvers. The simulation results show that the proposed framework outperforms traditional control strategies with significant improvements in lateral tracking accuracy, yaw stability, and sideslip angle suppression. Full article

With the growing application demands for cooperative guidance systems, the ITAC guidance law has undergone rapid technological advancement in recent research developments. However, existing ITAC methods often overlook the critical issue of command discontinuity during the midcourse-to-terminal guidance handover stage. To address this gap, this study proposes a novel fifth-order polynomial guidance law that simultaneously incorporates initial conditions (flight path angle and acceleration) and ensures precise ITAC performance. The method analytically derives polynomial coefficients from boundary constraints and transforms them into a computationally efficient closed-loop guidance law. Additionally, a positional error compensation term is derived to enable the practical realization of the proposed guidance law. Numerical simulations demonstrate the advantages of the proposed guidance law compared to existing methods. The results confirm that the fifth-order polynomial guidance law effectively resolves midcourse-terminal handover challenges while maintaining computational efficiency, offering a viable solution for cooperative guidance systems that require ITAC capability. Full article

During the drainage process of coalbed methane (CBM) horizontal wells, wellbore fluctuations exert a significant influence on gas–liquid–solid three-phase flow behavior and coal particle migration. This study investigates the effects of wellbore inclination, gas–liquid flow rates, and coal particle sizes on migration characteristics through laboratory-scale experiments, based on an initial analysis of coal particle physical properties. A critical velocity model accounting for wellbore fluctuations is developed and refined. The migration states of coal particles under various operational conditions are examined, and the corresponding critical velocities and movement patterns are analyzed. The results show that coal particle migration is predominantly governed by the liquid phase, while the presence of particles has limited impact on the overall gas–liquid flow regime. Under different wellbore inclinations, the critical velocity increases with particle size; however, the influence of inclination is more pronounced than that of particle size. Coal particle entrainment follows three distinct stages: hopping, rolling, and suspension. The velocity during the rolling stage is identified as the critical velocity. At steeper inclination angles, particles are more easily entrained by the flow, and the associated critical velocity is higher. Based on the fitted experimental data, the model is revised to improve its predictive capability for coal particle transport in CBM wells. Finally, the model is validated using field data from a CBM well in the Ordos Basin. The results confirm the model’s ability to predict coal particle accumulation trends within the wellbore. This study provides new insights into coal particle migration mechanisms under fluctuating wellbore conditions, offering both experimental and theoretical support for understanding gas–liquid–solid flow behavior. It also presents technical guidance for optimizing drainage performance, controlling particle deposition, and formulating wellbore cleaning strategies. Full article

In this paper, an accurate error compensation method based on geometric parameter correction and process optimization is proposed for the problem of coupling error in a heavy-load longitudinal and transversal swing table (HLTST) under space constraints, which makes it difficult to control the position efficiently and accurately. The key geometric parameters of pitch and roll layers are determined according to the machining process and assembly relationship, and the kinematic model is modified to effectively reduce the impact of contour error on the system’s accuracy. A coupling error model is established and its transmission mechanism is analyzed to develop a positioning error compensation strategy. Numerical simulation is employed to examine the distribution law, sensitivity, and volatility of independent error and coupling error. This aids in optimizing the design of the table’s machining process by balancing machining accuracy and economy. After the identification of the error parameters, the error compensation model is verified using the uniform design experimentation. The experimental results demonstrate 96.94% and 65.63% reductions in absolute average errors for the pitch and roll angles, respectively, especially when the maximum positioning error under the maximum load condition is controlled within ±5%, which significantly enhances motion accuracy and robustness under complex working conditions. This provides theoretical support and practical guidance for real-world engineering applications. Full article

Mountain reservoirs are often exposed to geological hazards, particularly landslides, posing significant risks to dam stability. This study conducted scaled experiments to investigate the surge pressure loads induced by landslides entering reservoirs under controlled conditions. Landslide volumes ranging from 500 cm³ to 2000 cm³ and slope angles of 35° and 45° were tested under different scenarios. Key parameters, including landslide volume, slope angle, water depth, and the distance between the landslide impact point and the dam were systematically varied to evaluate their effects on the maximum impact pressure along the reservoir bank. Through a systematic analysis of landslide volume, slope angle, water depth, and impact distance, their effects on maximum impact pressure were evaluated. Dimensional analysis and regression modeling were then used to develop a predictive model for maximum impact pressure. The results indicate that larger landslide volumes and steeper slopes amplify impact pressure, whereas greater water depths and larger distances from the impact point reduce it. Empirical equations for predicting impact pressure on reservoir banks and dam faces demonstrated strong agreement with experimental data. These findings offer crucial insights into the mechanisms influencing impact pressures in reservoirs and provide practical guidance for dam stability assessments under landslide-induced surge conditions. Full article

This study presents an advanced second-order sliding-mode guidance law with a terminal impact angle constraint, which ingeniously combines reinforcement learning algorithms with the nonsingular terminal sliding-mode control (NTSM) theory. This hybrid approach effectively mitigates the inherent chattering issue commonly associated with sliding-mode control while maintaining high levels of control system precision. We introduce a parameter to the super-twisting algorithm and subsequently improve an intelligent parameter-adaptive algorithm grounded in the Twin-Delayed Deep Deterministic Policy Gradient (TD3) framework. During the guidance phase, a pre-trained reinforcement learning model is employed to directly map the missile’s state variables to the optimal adaptive parameters, thereby significantly enhancing the guidance performance. Additionally, a generalized super-twisting extended state observer (GSTESO) is introduced for estimating and compensating the lumped uncertainty within the missile guidance system. This method obviates the necessity for prior information about the target’s maneuvers, enabling the proposed guidance law to intercept maneuvering targets with unknown acceleration. The finite-time stability of the closed-loop guidance system is confirmed using the Lyapunov stability criterion. Simulations demonstrate that our proposed guidance law not only meets a wide range of impact angle constraints but also attains higher interception accuracy and faster convergence rate and better overall performance compared to traditional NTSM and the super-twisting NTSM (ST-NTSM) guidance laws, The interception accuracy is less than 0.1 m, and the impact angle error is less than 0.01°. Full article

Conventional numerical models frequently neglect the effects of strain softening and the spatial variability of surrounding rock when addressing the design and construction of deep tunnels in complex geological settings, which leads to a large deviation from the actual situation and potential security risks. In this case, symmetrical and asymmetric failure of surrounding rock usually occurs. In this paper, a numerical model considering strain softening and spatial variability is established for deep tunnel excavation based on the constitutive theory and probability distribution functions, and their effects on the mechanical behavior of tunnel excavation are systematically examined using FLAC3D software. The findings indicate that symmetrical failure will occur in strain-softening rock mass, and spatial variability will lead to asymmetric failure of surrounding rock. The strain-softening behavior of the internal friction angle has a pronounced impact on the plastic zone radius and post-excavation displacement. The distribution of stress and displacement in the surrounding rock is notably influenced by the spatial variability of the elastic modulus, while the variability in the internal friction angle can cause localized stress concentrations within the tunnel, potentially triggering partial collapse and instability. The coupling effect of strain softening and the spatial variability of surrounding rock properties will aggravate the mechanical response during tunnel excavation, resulting in greater displacement and more severe stress redistribution. Based on these findings, disaster prevention and control strategies are proposed for tunnels in complex geological regions, offering valuable guidance for engineering applications. Full article

In recent years, leading-edge tubercles have gained significant attention as an innovative biomimetic flow control technique. This paper explores their impact on the aerodynamic performance and flow patterns of an airfoil through wind tunnel experiments, utilizing force measurements and tuft visualization at Reynolds numbers between 2.7 × 10⁵ and 6.3 × 10⁵. The baseline airfoil exhibits a hysteresis loop near the stall angle, with sharp changes in lift coefficient during variations in the angle of attack (AOA). In contrast, the airfoil with leading-edge tubercles demonstrates a smoother stall process and enhanced post-stall performance, though its pre-stall performance is slightly reduced. The study identifies four distinct flow regimes on the modified airfoil, corresponding to different segments of the lift coefficient curve. As the AOA increases, the flow transitions through stages of full attachment, trailing-edge separation, and local leading-edge separation across some or all valley sections. Additionally, the study suggests that normalizing aerodynamic performance based on the valley section chord length is more effective, supporting the idea that leading-edge tubercles function like a series of delta wings in front of a straight-leading-edge wing. These insights provide valuable guidance for the design of blades with leading-edge tubercles in applications such as wind and tidal turbines. Full article

Novice drivers often face challenges such as misjudgment, inappropriate steering control, distraction, and insufficient speed control when making left turns at intersections, leading to safety hazards. Installing intersection guide lines offers a solution by providing clear path directions, mitigating safety concerns associated with novice drivers’ left-turn actions. This study explored the impact of intersection guide line configurations on the driving behavior of novice drivers during left turns, utilizing large, medium, and small typical intersections to create six categories of left-turn simulation scenarios in a driving simulator. Data on vehicle trajectory, steering angle, steering speed, and eye-tracking were collected and analyzed. The study revealed that guide line arrangement significantly influences novice drivers’ left-turning behavior, enhancing path guidance while reducing trajectory and steering angle fluctuations, speed variations, and driver attention dispersion. This improvement in stability is particularly notable as intersection size and the number of left-turn lanes increase. The study’s findings offer robust theoretical support and guidance for the development and widespread adoption of intersection guide lines. Full article

Aimed at addressing the strong nonlinearity and strong external disturbances that cause flight control issues in conventional guided projectiles, as well as the slow response and structural vibrations that often occur in sliding mode control systems, which have a detrimental impact on the control effect and ultimate hit precision, a new type of fast and robust control algorithm with a unidirectional mode has been designed. The objective is to design an optimized aerodynamic shape for the projectile and to establish a dynamic model of the roll channel and a motion model of the entire trajectory. The dynamics of a new global terminal sliding mode are proposed, and an adaptive parameter term is realized by calculating the state of the critical sliding mode surface, which ensures that the tracking error converges within a finite time. Its combination with an adaptive approaching law is used to further speed up convergence while damping the structural vibration of the system. The bias error of the roll angle is constructed as the controller and simulation calculations are conducted on the basis of the aforementioned framework. The stability and time convergence of the control system are demonstrated through Lyapunov theory. The results indicate that, in comparison to the conventional terminal sliding mode controller, the designed controller exhibits a markedly rapid convergence rate and stronger robustness in tracking the command signal. Moreover, it also maintains a stable motion attitude of the projectile throughout the entire process. The superior control effect under different guidance schemes and the strong external disturbances also further reflect the anti-jamming capability and tracking performance of the system. Full article

Good architectural space design can bring positive emotional stimulation and relaxation to users, but few studies have investigated the quantitative indicators in architectural space design and their impact on user emotions. This study takes the right-angle sandwich interface system in architecture as an example to guide the next vertical greening simulation experiment by comparing the spatial quantitative differences in connection value, integration degree, and population agglomeration. Eighty adolescent volunteers were recruited into a control (artificial decorative wall) and experimental (green wall) group based on wall type. We compared their physiological and psychological indicators, including blood pressure and blood oxygen, and psychological indicators, including POMS and SIAI-S scales. Then, we made predictive factor judgements on vertical green elements. The quantification of the interior space of the building showed consistency in parameter changes, with the central area being the area of connectivity, integration, and crowd aggregation values. After the experiment, the experimental group showed a significant decrease in diastolic blood pressure, systolic blood pressure, and heart rate (p = 0.00) and a significant decrease in tension, anger, fatigue, depression, and panic (p = 0.00). The quantitative relationship between vertical greening elements and emotional promotion using stepwise linear exploration shows that the “vine” element is a significant predictive factor for diastolic blood pressure, T-A emotion, and SIAI-S values. The results enrich the indoor optimization and creation expansion paths of interface systems for various spatial experiences and further provide guidance for urban indoor green construction plans and green landscape facility planning via the emotional influence of indoor vertical space greening on young people. Full article

To increase the hit efficiency and lethality of a flight vehicle, it is necessary to consider the vehicle’s guidance law concerning both impact time and angle constraints. In this study, a novel and straightforward impact time and angle control guidance law that is independent of time-to-go and small angle approximations is proposed with two stages using a data-driven method and proportional navigation guidance. First, a proportional navigation guidance-based impact angle control guidance law is designed for the second stage. Second, from various initial conditions on the impact angle control guidance simulation with various initial conditions, the input and output datasets are obtained to build a mapping network. Using the neural network technique, a mapping network model that can output the ideal flight path angle in flight is constructed for impact time control in the first stage. The proposed impact time and angle control guidance law reduces to the proportional navigation guidance law when the flight path angle error converges to zero. The simulation results show that the proposed guidance law delivers excellent performance under various conditions (including cooperative attack) and features better acceleration performance and less control energy than does the comparative impact time and angle control guidance law. The results of this research are expected to supplement those exploring various paradigms to solve the impact time and angle control guidance problem, as concluded in the current literature. Full article

Deep foundation pit excavation is an important way to develop underground space in congested urban areas. Rock bridges prevent the interconnection of joints and control the deformation and failure of the rock mass caused by excavation for foundation pits. However, few studies have considered the acoustic properties and strain field evolution of rock bridges. To investigate the control mechanisms of rock bridges in intermittent joints, jointed specimens with varying rock bridge length and angle were prepared and subjected to laboratory uniaxial compression tests, employing acoustic emission (AE) and digital image correlation (DIC) techniques. The results indicated a linear and positive correlation between uniaxial compressive strength and length, and a non-linear and negative correlation with angle. Moreover, AE counts and cumulative AE counts increased with loading, suggesting surges due to the propagation and coalescence of wing and macroscopic cracks. Analysis of RA-AF values revealed that shear microcracks dominated the failure, with the ratio of shear microcracks increasing as length decreased and angle increased. Notably, angle exerted a more significant impact on the damage form. As length diminished, the failure plane’s transition across the rock bridge shifted from a complex coalescence of shear cracks to a direct merger of only coplanar shear cracks, reducing the number of tensile cracks required for failure initiation. The larger the angle, the higher the degree of coalescence of the rock bridge and, consequently, the fewer tensile cracks required for failure. The decrease of length and the increase of angle make rock mass more fragile. The more inclined the failure mode is to shear failure, the smaller the damage required for failure, and the more prone the areas is to rock mass disaster. These findings can provide theoretical guidance for the deformation and control of deep foundation pits. Full article

In order to achieve the precise attack of multiple underwater intelligent vehicles (UIVs) on the same target ship at a fixed impact time, and to improve the penetration capability of the UIVs themselves, this study investigated the guidance law for the time-cooperative guidance of UIVs with maneuvering evasion. The evasive maneuver of the UIV increases the line-of-sight angle between the UIV and the target, which decreases the guidance precision of the UIV. A segmented control strategy is proposed to solve the problem of decreasing guidance precision caused by evading maneuvers, which is also the main contribution of this paper. This control strategy is dividing the guidance trajectory into two segments. The first segment allows for intelligent underwater vehicles to make evasion maneuvers and penetrate the defense, while the second segment controls the terminal time and achieves precision strike. Different desired target-vehicle distances are designed for each segment, unifying the impact time control issue and evasion maneuver problem into the pursuit of desired target-vehicle distances. Finally, based on feedback linearization control theory, a time-cooperative guidance law with evasion maneuver capability is proposed. Simulation results validate the effectiveness of the proposed method in attacking-moving targets. Full article