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This paper investigates the fixed-time tracking control problem for agile missiles with multiple heterogeneous actuators in the presence of saturation constraints and external disturbances. To reduce the turning radius and promote maneuvering envelope, a novel combination scheme for blended actuators is introduced in this paper, consisting of a flexible mechanism control system (FCS), reaction-jet control system (RCS), and aerodynamic control. Based on the proposed nonsingular terminal sliding mode surface, a fixed-time anti-saturation controller with an auxiliary system is presented first to ensure global fixed-time stability and to compensate for the adverse effects of input saturation. Subsequently, a fixed-time disturbance observer is constructed to estimate uncertainties and lumped disturbances, and to address the chattering problem. To assign the total virtual control command to different actuators, a control allocation based on dynamic programming considering actuator dynamics is established. Finally, detailed numerical simulations and comparisons are provided to verify the effectiveness and superiority of the proposed control scheme. [ABSTRACT FROM AUTHOR]

The rudder surfaces and lifting surfaces of a missile are utilized to acquire aerodynamic forces and moments, adjust the missile's attitude, and achieve precise strike missions. However, the harsh flying conditions of missiles make the rudder surfaces and lifting surfaces susceptible to faults. In practical scenarios, there is often a scarcity of fault data, and sometimes, it is even difficult to obtain such data. Currently, data-driven fault detection and localization methods heavily rely on fault data, posing challenges for their applicability. To address this issue, this paper proposes an HBOS (Histogram-Based Outlier Score) online fault-detection method based on statistical distribution. This method generates a fault-detection model by fitting the probability distribution of normal data and incorporates an adaptive threshold to achieve real-time fault detection. Furthermore, this paper abstracts the interrelationships between the missile's flight states and the propagation mechanism of faults into a hierarchical directed graph model. By utilizing bilateral adaptive thresholds, it captures the first fault features of each sub-node and determines the fault propagation effectiveness of each layer node based on the compatibility path principle, thus establishing a fault inference and localization model. The results of semi-physical simulation experiments demonstrate that the proposed algorithm is independent of fault data and exhibits high real-time performance. In multiple sets of simulated tests with randomly parameterized deviations, the fault-detection accuracy exceeds 98% with a false-alarm rate of no more than 0.31%. The fault-localization algorithm achieves an accuracy rate of no less than 97.91%. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate a novel impact time control guidance (ITCG) law based on the sliding mode control (SMC) for a nonmaneuvering target using the predicted interception point (PIP). Design/methodology/approach: To intercept the target with the minimal miss distance and desired impact time, an estimation of time-to-go is introduced. This estimation results in a precise impact time for multimissiles salvo attack the target at the same time. Even for a large lead angle, the desired impact time is achieved by using the sliding mode and Lyapunov stability theory. The singularity issue of the proposed impact time guidance laws is also analyzed to achieve an arbitrary lead angle with the desired impact time. Findings: Numerical scenarios with desired impact time are presented to illustrate the performance of the proposed ITCG law. Comparison with the state-of-art impact time guidance laws proves that the guidance law in this paper can enable the missile to intercept the target with minimal miss distance and final impact time error. This method enables multiple missiles to attack the target simultaneously with different distances and arbitrary lead angles. Originality/value: An ITCG law based on sliding mode and Lyapunov stability theory is proposed, and the switching surface is designed based on a novel estimation time-to-go for the missile to intercept the target with minimal miss distance. To intercept the target with initial arbitrary lead angles and desired impact time, the authors analysis the singular issue in SMC to ensure that the missile can intercept the target with arbitrary lead angle. The proposed approach for a nonmaneuvering target using the PIP has simple forms, and therefore, they have the superiority of being implemented easily. [ABSTRACT FROM AUTHOR]

In this paper, an intelligent control method applying on numerical virtual flight is proposed. The proposed algorithm is verified and evaluated by combining with the case of the basic finner projectile model and shows a good application prospect. Firstly, a numerical virtual flight simulation model based on overlapping dynamic mesh technology is constructed. In order to verify the accuracy of the dynamic grid technology and the calculation of unsteady flow, a numerical simulation of the basic finner projectile without control is carried out. The simulation results are in good agreement with the experiment data which shows that the algorithm used in this paper can also be used in the design and evaluation of the intelligent controller in the numerical virtual flight simulation. Secondly, combined with the real-time control requirements of aerodynamic, attitude and displacement parameters of the projectile during the flight process, the numerical simulations of the basic finner projectile’s pitch channel are carried out under the traditional PID(Proportional-Integral-Derivative) control strategy and the intelligent PID control strategy respectively. The intelligent PID controller based on BP(Back Propagation) neural network can realize online learning and self-optimization of control parameters according to the acquired real-time flight parameters. Compared with the traditional PID controller, the concerned control variable overshoot, rise time, transition time and steady state error and other performance indicators have been greatly improved, and the higher the learning efficiency or the inertia coefficient, the faster the system, the larger the overshoot, and the smaller the stability error. The intelligent control method applying on numerical virtual flight is capable of solving the complicated unsteady motion and flow with the intelligent PID control strategy and has a strong promotion to engineering application. [ABSTRACT FROM AUTHOR]

In this paper an airframe stabilization system with state observer and correction part for a canard-controlled anti-aircraft missile is presented. The state observer based system is designed to be easy to implement and undemanding of significant onboard data processing and CPU resources. In addition, the correction part to improve the system's capabilities is described and an analytical method for determining its settings is proposed. The paper considers the terminal phase of guiding an anti-aircraft missile against an aerial target. This is of particular interest when considering the issues of combating the current means of air attack, characterized by high maneuverability, effectively. Robustness to disturbances in the signal processing paths and the ability to effectively stabilize the airframe is presented with extensive simulations of the proposed system using the Monte Carlo method. [ABSTRACT FROM AUTHOR]

A structured dynamic overlapping grid and a user-defined function are used to study the projectile launching process, and the hybrid Roe scheme is used to solve the flow field with strong shock wave. The launching process of a projectile with a muzzle decompression device is numerically simulated by using a three-dimensional transient model, and the flow field inside the muzzle decompression device and the development process of the muzzle flow field in the projectile launching process are discussed in detail. Compared with no device, the muzzle decompression device can effectively reduce the peak pressure around the muzzle; the numerical results are in agreement with the corresponding experimental values. The numerical investigation in this paper is helpful to understand the mechanism of pressure reduction of the device. It also provides a new way to reduce the muzzle pressure of aircraft gun. [ABSTRACT FROM AUTHOR]

This paper proposed an efficient research method for high-dimensional uncertainty quantification of projectile motion in the barrel of a truck-mounted howitzer. Firstly, the dynamic model of projectile motion is established considering the flexible deformation of the barrel and the interaction between the projectile and the barrel. Subsequently, the accuracy of the dynamic model is verified based on the external ballistic projectile attitude test platform. Furthermore, the probability density evolution method (PDEM) is developed to high-dimensional uncertainty quantification of projectile motion. The engineering example highlights the results of the proposed method are consistent with the results obtained by the Monte Carlo Simulation (MCS). Finally, the influence of parameter uncertainty on the projectile disturbance at muzzle under different working conditions is analyzed. The results show that the disturbance of the pitch angular, pitch angular velocity and pitch angular of velocity decreases with the increase of launching angle, and the random parameter ranges of both the projectile and coupling model have similar influence on the disturbance of projectile angular motion at muzzle. [ABSTRACT FROM AUTHOR]

To solve the problem of the low interference success rate of air defense missile radio fuzes due to the unified interference form of the traditional fuze interference system, an interference decision method based Q-learning algorithm is proposed. First, dividing the distance between the missile and the target into multiple states to increase the quantity of state spaces. Second, a multidimensional motion space is utilized, and the search range of which changes with the distance of the projectile, to select parameters and minimize the amount of ineffective interference parameters. The interference effect is determined by detecting whether the fuze signal disappears. Finally, a weighted reward function is used to determine the reward value based on the range state, output power, and parameter quantity information of the interference form. The effectiveness of the proposed method in selecting the range of motion space parameters and designing the discrimination degree of the reward function has been verified through offline experiments involving full-range missile rendezvous. The optimal interference form for each distance state has been obtained. Compared with the single-interference decision method, the proposed decision method can effectively improve the success rate of interference. [ABSTRACT FROM AUTHOR]

To address the difficulty in evaluating the damage effect of missile target attacked by fragmented warheads, this paper proposes a new damage assessment method. In this paper, the damage to the missile target is regarded as the result of the continuous action of multiple layers of warhead fragments at multiple times. Based on this damage mechanism, sample data is formed using the characteristic parameters of warhead fragments, by introducing intuitionistic fuzzy neural network (IFNN), a new missile target damage effect evaluation model based on IFNN is established. Finally, training and testing are conducted on the data of actual missile target intersection damage tests, and the results are compared with other target damage evaluation methods. The results show that this evaluation method can effectively obtain the damage value of the missile target, and the evaluation model has good generalization ability. This provides ideas for developing a new method to evaluate the static or dynamic damage effectiveness of intelligent ammunition. [ABSTRACT FROM AUTHOR]

Study of the engraving process is significant for interior ballistics. Due to the high transient and strong nonlinear characteristics of the engraving, research on the engraving mechanism is challenging. In this paper, based on the one-dimensional two-phase flow model of interior ballistics coupled with explicit dynamics software, finite element simulation of the engraving is carried out to obtain the changes of parameters during the engraving process, and the dynamic characteristics of the projectile engraving are discussed. By comparing the simulation results with the experimental data, the accuracy of the coupling method in this paper is verified. The relationship between the structural parameters of the sealing band and the extrusion resistance is revealed, and the influence of the extrusion resistance on the dynamic characteristics of the projectile is demonstrated. The simulation results can provide an essential reference for selecting a reasonable sealing band structure. [ABSTRACT FROM AUTHOR]

This paper aims to analyze the stability of a special class of single-channel slow-rotating homing missiles using the Frank–Wall stability criterion. To achieve this, starting from the model of a slow-rolling missile with six degrees of freedom (6 DOFs) in the body frame, a 6-DOFs model in the Resal frame is obtained, which is used to linearize the coupled commanded motion. Based on the linearized model, we obtain the structural scheme of the commanded object and define the flight quality parameters. The obtained linear model has a complex representation (with real and imaginary parts) due to the coupling between longitudinal channels for the rolling missile. Then, the kinematic guidance equations, the seeker equations and the actuator relations using a switching function, specific to the slow-rolling single-channel missile, are defined. The guidance kinematic equations, the seeker equations and the actuator model are linearized in the Resal frame, and the structural diagram of the homing missile is constructed. Starting from this, the characteristic polynomial having complex coefficients is determined and then analyzed with the Frank–Wall stability criterion. Based on the analysis, a stability range is determined for the navigation constant (k) , and a minimum and possibly a maximum limit for the time to hit the target t g o is obtained. The stability range defined for the navigation constant in the linear model is finally validated in the nonlinear model in the body frame. [ABSTRACT FROM AUTHOR]

Purpose: Before designing a navigation system, it is necessary to analyse possible approaches in terms of expected accuracy, existing limitations and economic justification to select the most advantageous solution. This paper aims to collect possible navigation methods that can provide correction for inertial navigation and to evaluate their suitability for use on a manoeuvring tactical missile. Design/methodology/approach: The review of existing munitions was based on data collected from the literature and online databases. The data collected included dimensions, performance, applied navigation and guidance methods and their achievable accuracy. The requirements and limitations identified were confronted with the range of sensor parameters available on the market. Based on recent literature, navigation methods were reviewed and evaluated for applicability to inertial navigation system (INS) correction in global navigation satellite system-denied space. Findings: The performance analysis of existing munition shows that small and relatively inexpensive micro-electro-mechanical system-type inertial sensors are required. A review of the parameters of existing devices of this type has shown that they are subject to measurement errors that do not allow them to achieve the delivery accuracy expected of precision missiles. The most promising navigation correction methods for manoeuvring flying objects have been identified. Originality/value: The information presented in this paper is the result of the first phase of a project and presents the results of the requirements selection, initial sizing and preliminary design of the navigation system. This paper combines a review of the current state of the art in missile systems and an analysis of INS accuracy including the selection of sensor parameters. [ABSTRACT FROM AUTHOR]

The reliability and availability of a Jet Unmanned Aerial Vehicle (JUAV) for balloon downing are evaluated in this third part of the paper. The paper delves into the challenges faced by traditional air defence systems in countering high-altitude balloons, leading to the proposal of substituting missiles with Unmanned Aerial Vehicles (UAVs), specifically the Jet Unmanned Aerial Vehicle (JUAV). The best solution found in the previous section is a derivation of the 1:6 scale RC model of the Lockheed F104C. This is designed for balloon downing, and the essay meticulously analyses its reliability, failure probabilities, and maintenance strategies for various subsystems. The engine is replaced with a more powerful micro-jet, and an 84 mm recoilless cannon is added at the base of the tail. The scaled-down model can use most data derived from the full-scale airplane flight manual, corrected for larger thrust-to-weight and lower wing-loading. Several adjustments and additions are made on sensors, autopilot, On-Line Diagnostic System, communication system, and firing system to increase the reliability of the system. Due to the relatively short design life of the RC model, the Time Between Overhaul (TBO) of the UAV is reduced to 25 h. Consequently, the study emphasizes the importance of simplicity, operational reliability, and adaptability in the development and assessment of modern missile defence systems. The reliability of the JUAVI is presented as 98.14% for 50 consecutive fully automatic missions, highlighting its potential significance in bolstering national security. [ABSTRACT FROM AUTHOR]

The chassis based on the VPX bus standard structure has been widely applied to the fields of vehicle, missile, radar, etc. In this paper, we analyze the electromagnetic environment effect on VPX chassis via the CST software, and investigate the electromagnetic coupling characteristics of VPX chassis under 20 v/m plane wave radiation according to the RS103 test defined in the MIL-STD-461G standard. By simulation, we analyze the electromagnetic coupling paths of the VPX chassis, find the key positions of the electromagnetic protection such as the air intake, air outlet, trapdoor, and panel gaps, and we propose the electromagnetic protective measures for the weak parts of the VPX chassis. The electromagnetic shielding effectiveness before and after protection design is evaluated. Finally, the simulation results are verified by the experiments. It has guiding significance for the electromagnetic protection design of VPX chassis. [ABSTRACT FROM AUTHOR]

In the weapon test range, the space projectile explosion position parameter at the terminal trajectory is an important index to evaluate the damage performance of the projectile fuze. Due to the random distribution of the falling dispersion of the projectile, it is difficult to test the projectile explosion position in the long‐range terminal trajectory falling area. To solve this problem, this paper proposes a method for measuring the projectile explosion position based on ultra‐wide imaging with a multi‐lens array. A curved multi‐lens array optical imaging system is designed and the parameter calculation method of the optical system is presented. The relationship between the space projectile explosion position and the center of the sub‐eye lens and the relationship between the center of the sub‐eye lens and the imaging point of the image sensor is established according to the imaging principle of the optical system. The object image relations of any seven adjacent sub‐eye lenses of the curved multi‐lens array optical imaging system are combined and the calculation model of the space projectile explosion position is deduced. The experimental results verify that the designed curved multi‐lens array optical imaging system and the calculation model of the projectile explosion position proposed in this paper are reasonable. [ABSTRACT FROM AUTHOR]

This paper deals with the design of a deformable nose for the non-penetrating projectile in order to protect its body against deformation. Numerical, analytical, and experimental studies have been carried out to analyze the effect of different nose shapes on the projectile deformation when it hits the brick wall. The projectile consists of an aluminum nose, a thin-walled steel cylinder body, and an end connector. This nonpenetrating projectile can be used to carry a cargo that must reach its destination safely, e.g., firefighting applications. To meet this goal, the criterion utilized for the best design in this paper is stress and strain analysis. The geometric shape of the noses includes three types: type (a), type (b), and type (c). The first type of nose is at shape. This nose was detached from the projectile by impact and did not prevent the projectile deformation. The second type of nose was a combination of at and conical shapes. The projectile was also deformed by this nose. The third type of nose was a combination of at, conical, and spherical shapes. Due to the maximum absorption of the impact energy, this type of nose prevented the deformation of the cargo and projectile. [ABSTRACT FROM AUTHOR]

It is of great significance to explore the ocean environment and strategic deployment under the polar ice layer. In this paper, the evolution laws of the water entry cavity of projectiles passing through ice holes with different shapes and sizes are studied, and the motion states of projectiles passing through holes are described. The case of zero-gap contact motion between a projectile and a hole is considered. The results show that the initial resistance drag of the projectile passing through the circular ice hole is the largest in the case of zero-gap contact, and the cavity collapse is serious, while almost no cavity appears at the shoulder of the projectile when passing through the square hole. The intersection of splash crowns is formed at the square and triangular ice holes as the hole size increases, a diffused cavity is formed at the bottom of the hole edge, and the formation of the jet appears multiple times at each stage. Some unique vortices appear near the hole when the projectile passes through the hole. The variations of force and velocity of the projectile passing through the triangular hole are stable, but the velocity drop is the largest. [ABSTRACT FROM AUTHOR]

In order to scientifically evaluate the target damage effect of uncertain intersection between projectile and target confrontation game, this paper establishes a basic model of target damage in the intersection between projectile and target game, which is through the spatial relationship between the explosive position of the projectile and the target position and gives a calculation method of target damage evaluation. The study applies Nash equilibrium theory to analyze income-loss functions in an adversarial game model. According to the definition of the possibility degree of interval number in uncertain multi-attribute decision-making, we proposed a method of solving the Nash equilibrium value of the income matrix of both sides of the game, which is using the interval possibility degree. We used quantitative calculations to analyze game strategies and changes in target damage under different states, such as fragment numbers, velocities, and angles of hit in the confrontation game between projectile and target. Based on the Nash equilibrium value solution method of the particle swarm optimization algorithm, we quantitatively calculated the fitness change relationship between the projectile and the target under different strategy sets. Based on the actual projectile confrontation game test, we analyze the damage probability effects of two projectiles at different explosion positions and different rendezvous angle angles on the three cabins. The results show that in the same area, the intersection angle is smaller, the probability of target damage is greater, and the intersection distance is farther, the damage probability is smaller. [ABSTRACT FROM AUTHOR]

Concrete structures are commonly used as secure settlements and strategic shelters due to their inherent strength, durability, and wide availability. Examining the robustness and integrity of strategic concrete structures in the face of superenergy projectiles is of utmost significance in safeguarding vital infrastructure sectors, ensuring the well-being of individuals, and advancing the course of worldwide sustainable progress. This research focuses on forecasting the penetration depth (BPD) through the application of robust models, such as Multilayer Perceptron (MLP), Support Vector Machine (SVM), Light Gradient Boosting Machine (LightGBM), and K-Nearest Neighbors (KNN) as ML models. The dataset used consists of 1,020 data points sourced from the National Institute of Standards and Technology (NIST), encompassing various parameters such as cement content (Cp), ground granulated blast-furnace slag (GGBFS), fly ash content (FA), water portion (Wp), superplasticizer content (Sp), coarse aggregate content (CA), fine aggregate content (FAA), concrete sample age (t), concrete compressive strength (CCS), gun type (G-type), bullet caliber (BCali), bullet weight (Wb), and bullet velocity (Vb). Feature selection techniques revealed that the MLP model, incorporating eight input variables (FA, CA, Sp, GGBFS, Cp, t, FAA, and CCS), provides the most accurate predictions for BPD across the entire dataset. Comparing the four models used in this study, KNN demonstrates distinct superiority over the other methods. KNN, a non-parametric ML model used for classification and regression, possesses several advantages, including simplicity, non-parametric nature, no training requirements, robustness to noisy data, suitability for large datasets, and interpretability. The results reveal that KNN outperforms the other models presented in this paper, exhibiting an R² value of 0.9905 and an RMSE value of 0.1811 cm, signifying higher accuracy in its predictions compared to the other models. Finally, based on the error analysis across iterations, it is evident that the final accuracy error of the KNN model surpasses that of the SVM, MLP, and LightGBM models, respectively. [ABSTRACT FROM AUTHOR]

Due to the complexity of the missile air data system (ADS) and the harshness of the environment in which its sensors operate, the effectiveness of traditional fault diagnosis methods is significantly reduced. To this end, this paper proposes a method fusing the model and neural network based on unscented Kalman filter (UKF) and Inception V3 to enhance fault diagnosis performance. Initially, the unscented Kalman filter model is established based on an atmospheric system model to accurately estimate normal states. Subsequently, in order to solve the difficulties such as threshold setting in existing fault diagnosis methods based on residual observers, the UKF model is combined with a neural network, where innovation and residual sequences of the UKF model are extracted as inputs for the neural network model to amplify fault characteristics. Then, multi-scale features are extracted by the Inception V3 network, combined with the efficient channel attention (ECA) mechanism to improve diagnostic results. Finally, the proposed algorithm is validated on a missile simulation platform. The results show that, compared to traditional methods, the proposed method achieves higher accuracy and maintains its lightweight nature simultaneously, which demonstrates its efficiency and potential of fault diagnosis in missile air data systems. [ABSTRACT FROM AUTHOR]

The direct/aerodynamic force compound control can enhance the maneuverability and response characteristics of missiles, and the dynamic stabilization is the precondition of normal operation for rolling missiles. Aiming at the stability problem caused by the cross-coupling effect of rolling missiles employing direct/aerodynamic force compound control, proposing a typical topological control system structure described by the complex coefficient theory, and deducing the dynamic stability conditions. Firstly, the mathematic model is established based on the kinematics and dynamics theories of rotating airframes and the direct/aerodynamic force compound control mechanism. Then, a three-loop autopilot and the direct/aerodynamic force ratio distribution method are designed to establish the complex summation model of the compound control system by selecting suitable complex variables. Furthermore, deducing the dynamic stability conditions and verifying them by numerical simulations. Finally, the stable regions of the rolling missile in different cases are obtained and found to be influenced by many factors, such as parameters of the autopilot, hybrid force distribution proportion and rolling rate. The derived dynamic stability criterion is effective for evaluating the stability of rolling missiles employing direct/aerodynamic force compound control and the research method used in this paper can provide reference for the stability study of strongly coupled nonlinear systems. [ABSTRACT FROM AUTHOR]

This paper proposes a method for calculating the received power by modeling the environment in which a target and guided weapon encounter each other and analyzing the RCS and gains in the near field. The target encounter environment was modeled by fixing the position of the simple missile shape target and moving the horn antenna. The near-field RCS was analyzed based on the magnitude of the Poynting vector obtained using the HFSS SBR+ simulation. The received power was calculated by substituting the antenna gain, which varies based on the distance from the target, and the previously analyzed near-field RCS into the radar equation. The received power calculated using the proposed method is compared and verified with the received power obtained using the far-field RCS, gain, and the received power obtained through simulation. [ABSTRACT FROM AUTHOR]

This article concentrates on the problem of fixed-time tracking control for a certain class of nonlinear systems with unmodeled dynamics. Unmodeled dynamics are prevalent in practical engineering systems, such as axially symmetric systems like robotic arms, spacecraft, and missiles. In this paper, the fuzzy-logic systems (FLSs) are implemented to address the challenge of accurately approximating the unknown nonlinear terms that arise during the derived control algorithm process. By employing fixed-time command filters (FTCF), the "explosion of complexity" issues encountered in traditional backstepping methods will be effectively resolved. Moreover, error compensation mechanisms are derived to effectively mitigate the filtering errors that may arise from the FTCFs. The computational burden associated with FLSs is reduced through the utilization of the weight vector estimation method based on the maximal norm and an adaptive approach. A fixed-time adaptive fuzzy tracking controller is developed within the backstepping control framework to ensure the boundedness of all signals and achieve fixed-time convergence of the tracking error for the controlled system. Illustrative examples are conducted to illustrate the viability of the derived controller. [ABSTRACT FROM AUTHOR]

Supercavitation technology has important application value in military and national defence fields because of its huge potential in drag reduction, while the cavitation around underwater moving objects may be affected by the surface properties of objects. In this paper, the supercavitation characteristics and hydrodynamics of a projectile with hydrophobic and hydrophilic surface coatings were experimentally studied using a high-speed camera. The supercavitation evolution, cavitation size, velocity change, drag force coefficient, and ballistic deflection of projectiles in different water depths are compared and analyzed. The results show that the length and diameter of the supercavity increase with the decrease in water depth. At the same water depth and cavitation number, the length and diameter of the supercavitation of the projectile with hydrophobic coating were greater than those of the projectile with hydrophilic coating, and the drag force coefficient of the hydrophobic projectile was obviously smaller than that of the hydrophilic projectile. Under the working conditions of 6.67D, 16.7D, and 33.3D, the drag force coefficient of the hydrophobic projectile could be reduced by about 20–40% compared with that of the hydrophilic projectile. The maximal reduction in drag force coefficient was up to 40% at σ = 0.34 under a water depth of 33.3D. The velocity attenuation of hydrophobic projectile was about 20% slower than that of hydrophilic projectile. In addition, the ballistic stability of hydrophobic coated projectiles was better than that of hydrophilic coated projectiles in the different water depths observed in the paper. [ABSTRACT FROM AUTHOR]

This paper presents the results of the building of a parameter recognition algorithm and state evaluation for separate targets, to improve the effectiveness of target tracking for interceptor missiles. The assessment maneuver of the separating target is of great significance for the interceptor missile to recognize the maneuverability and assess the danger level of targets of the target in the group. With applied to the optimal Kalman filter algorithm, the structure of the filter is simple, and the evaluation error is small therefore the state evaluation accuracy of the algorithm is advanced, and the results of evaluating the system are verified through simulation on Matlab. After evaluation, the maneuvering parameters of the separating target will be included in the algorithm to evaluate the target's maneuvering direction later to the decision to track (or not to track) the initially selected target and destroy (or not destroy) the new separating target that appeared because of its danger. [ABSTRACT FROM AUTHOR]

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Aiming at the problem of cooperative target estimation for multiple strap-down missiles, this paper is concerned with developing a distributed cooperative estimation fusion algorithm considering the random transmission delay of observation data. As a stepping stone, the random measurement delay system with multiple strap-down missiles is transformed into a delay-free system with correlation noise in finite time intervals using the random observation delay model for strap-down missiles. Then, the distributed fusion technique without feedback is proposed based on the design of the best local filter for each strap-down sampling subsystem; To further enhance the robustness and stability of the cooperative target estimation system, the distributed fusion algorithm with feedback is suggested. Simulation in various cases and comparison studies are conducted to verify the effectiveness and robustness of the proposed scheme. [ABSTRACT FROM AUTHOR]

In this paper, an optimal sliding mode guidance law with impact angle constraint is proposed against maneuvering targets. Firstly, the impact angle frame for a static target is extended to a maneuvering target. Then, in this impact angle frame, the optimal reaching law of sliding mode is proposed to design an optimal sliding mode guidance law which is robust to target maneuvers and satisfies an impact angle constraint. The optimal sliding mode guidance law with impact angle constraint is also extended to the three-dimensional case. Numerical simulations in different scenarios with a realistic missile model show that the guidance law can intercept a maneuvering target with a desired impact angle, and the control effort is close to the optimal value, which verifies that the proposed optimal sliding mode guidance law has both robustness and optimality. [ABSTRACT FROM AUTHOR]

This paper discusses using ground-based imagery to determine the attitude of a flying projectile assuming prior knowledge of its external geometry. It presents a segmentation-based approach to follow the object and evaluates it quantitatively with simulated data and qualitatively with both simulated and real data. Two experimental cases are considered: One assumes reliable target distance measurement from an auxiliary range sensor, while the other assumes no range information. The results show that in the case of an unknown projectile–camera distance, with projectile dimensions of 1.378 m and 0.08 m in length and diameter, the estimated distance, in-plane location, and pitch angle accuracies are about 50 m, 0.15 m, and 6 degrees, respectively. Yaw angle estimation is ambiguous. In the second case, assuming that the projectile–camera distance is known resolves the ambiguity of yaw estimation, resulting in accuracies of about 0.15 m, 3 degrees, and 20 degrees for in-plane location, pitch, and yaw angles, respectively. These accuracies were normalized to a 1-km projectile–camera distance. [ABSTRACT FROM AUTHOR]

The folding wing mechanism is a system developed for the miniaturization of missile wings to facilitate box (cylinder) storage, transportation, and launching, saving the storage and transportation space of the missile and improving the combat capability of the weapon system. In order to solve the stability problem of the dynamic opening process of wings during missile flight, a theoretical model of a double joint folding wing is proposed. Based on dynamic theory, this paper studies the dynamic process of the folding wing system undergoing rotational opening motion under different initial forces. The influence of the initial angular velocity required for folding wing deployment on the deployment process is analyzed through structural model simulation. Finally, the effect of the folding wing opening action on the flight motion of the full missile is studied, and the dynamic opening process of the folding wing system is simulated by physical experiments. The research results show that the opening motion of the folding wing is sensitive to the initial conditions; during the deformation process, a change in motion type was observed, and the aeroelastic response at certain folding angles may exhibit different motion types. The main impact on the flight motion of the full missile is the change in the aerodynamic force of the missile. [ABSTRACT FROM AUTHOR]

Reducing recoil as well as reducing muzzle hazards are important issues in artillery design. This paper presents a barrel gas reflection method for the artillery aiming for efficient recoil reduction while reducing muzzle hazards. The launching process is modeled by coupling the interior ballistic equations and the flow equations of the barrel gas reflection device. The fourth-order Runge–Kutta method was used to solve the model, and the LHS method as well as the Kriging model was used to establish a mapping relationship between the parameters and the effect. To validate the proposed model, shooting experiments are carried out on a 30 mm caliber artillery. The maximum error between the experiment and simulation results was 5.32%. The experiment has demonstrated that the barrel gas reflection method increases the recoil reduction efficiency of artillery by 44.54% and reduces the muzzle hazard by 52.18%. Finally, the barrel gas reflection method can produce effects with the muzzle device at the same time, and it has little effect on the velocity of the projectile muzzle velocity, and it provides a new way of thinking for the development of future artillery recoil reduction technology. [ABSTRACT FROM AUTHOR]

This paper presents an integrated guidance and control design for the homing missiles with the radome error compensation to address the guidance problems caused by radome. Firstly, a mathematics model of the integrated guidance and control system with the compensation for the radome error is built by integrating the missile dynamics and the engagement kinematics between the missile and ground target on the longitudinal motion. Secondly, the model is transformed into a normal form by nonlinear coordinate transformation because the system is a time-varying system with mismatched uncertainties. Thirdly, an adaptive control law of the system is designed by adopting the sliding mode control theory, and the stability of the closed-loop system is also conducted. Finally, the simulation proves that the proposed integrated guidance and control scheme can effectively compensate for the radome error and ensure the hit-to-kill attack to the target. [ABSTRACT FROM AUTHOR]

Purpose: One of the challenges encountered in the design of guided projectiles is their prohibitive cost. To diminish it, an appropriate avenue many researchers have explored is the use of the non-actuator method for guiding the projectile to the target. In this method, biologically inspired by the flying concept of the single-winged seed, for instance, that of maple and ash trees, the projectile undergoes a helical motion to scan the region and meet the target in the descent phase. Indeed, the projectile is a decelerator device based on the autorotation flight while it attempts to resemble the seed's motion using two wings of different spans. There exists a wealth of studies on the stability of the decelerators (e.g. the mono-wing, samara and pararotor), but all of them have assumed the body (exclusive of the wing) to be symmetric and paid no particular attention to the scanning quality of the region. In practice, however, the non-actuator-guided projectiles are asymmetric owing to the presence of detection sensors. This paper aims to present an analytical solution for stability analysis of asymmetric decelerators and apprise the effects of design parameters to improve the scanning quality. Design/methodology/approach: The approach of this study is to develop a theoretical model consisting of Euler equations and apply a set of non-dimensionalized equations to reduce the number of involved parameters. The obtained governing equations are readily applicable to other decelerator devices, such as the mono-wing, samara and pararotor. Findings: The results show that the stability of the body can be preserved under certain conditions. Moreover, pertinent conclusions are outlined on the sensitivity of flight behavior to the variation of design parameters. Originality/value: The analytical solution and sensitivity analysis presented here can efficiently reduce the design cost of the asymmetric decelerator. [ABSTRACT FROM AUTHOR]

In this paper, an integrated guidance and control method based on an adaptive path-following controller is proposed to control a spin-stabilized projectile with only translational motion information under the constraint of an actuator, uncertainties in aerodynamic parameters and measurements, and control system complexity. Owing to the fairly high rotation speed, the dynamic model of this missile is strongly nonlinear, uncertain and coupled in pitch, yaw and roll channels. A theoretical equivalent resultant force and uncertainty compensation method are comprehensively used to realize decoupling of pitch and yaw. In response to the strong nonlinear and time-varying characteristics of the dynamic system, the quasi-linear model whose parameters are obtained by interpolation of points selected as the segmentation points in the trajectory envelope, is used for calculation in each step. To cope with the system uncertainty caused by model approximation, parameter uncertainty and ballistic interference, an extended state estimator is used to compensate the output feedback according to the test ballistic angle. In order to improve the tracking efficiency and ensure the tracking error convergence with only translational motion information, the virtual guide point, whose derivative is deduced according to the Lyapunov principle, is calculated in real time according to the projection relationship between the real-time position and the reference trajectory, and a virtual line-ofsight angle and the backstepping method are used for the design of the guidance and control system. In order to avoid the influence of control input saturation on the guidance and control performance due to the actuator limitation and improve the robustness of the system, an anti-saturation compensator is designed according to the two-step method. The feasibility and effectiveness of the path-following controller is verified through closed-loop flight simulations with measurement, control, and condition uncertainties. The results indicate that the designed controller can converge to the reference path and evidently decrease the distance between the impact point and target under different uncertainties. [ABSTRACT FROM AUTHOR]

Sounding rockets constitute a class of rocket with a generally simple layout, being composed of a cylindrical center-body, a nosecone, a number of fins placed symmetrically around the longitudinal axis (usually three or four), and possibly a boat-tail. This type of flying craft is typically not actively controlled; instead, a passive stabilization effect is obtained through suitable positioning and sizing of the fins. Therefore, in the context of dynamic performance analysis, the margin of static stability is an index of primary interest. However, the classical approach to static stability analysis, which consists in splitting computations in two decoupled domains, namely, around the pitch and yaw axis, provides a very limited insight to the missile performance for this type of vehicle due to the violation of the classical assumptions of planar symmetry and symmetric flight conditions commonly adopted for winged aircraft. To tackle this issue, this paper introduces a method for analyzing static stability through a novel index, capable of more generally assessing the level of static stability for sounding rockets, exploiting the same information on aerodynamic coefficients typically required for more usual (i.e., decoupled) static stability analyses, and suggests a way to assess the validity and shortcoming of the method in each case at hand. [ABSTRACT FROM AUTHOR]

The structural impact similarity laws have corrected the distortion caused by the strain-rate effect and the material property differences mostly by changing the impact velocity. However, in many practical environments, the velocity of the projectile cannot be used as an initial condition for modification. This paper develops a new similarity framework that takes into account the material property differences in the penetration problem and corrects the similarity distortion between scaled models and prototypes by changing the plate thickness. The method is preliminarily proved feasible by an analytical model of dimensionless critical impact energy under penetration. In addition, a series of numerical simulations of blunt projectiles striking steel plates are carried out. The results show that differences in similar distortions between different scaled models with different materials can all be compensated by a dimensionless number based on the thickness of the target plate. [ABSTRACT FROM AUTHOR]

As one of the most widely used personal protective equipment (PPE), body armors play an important role in protecting the human body from the high-velocity impact of bullets or projectiles. The body torso and critical organs of the wear may suffer severe behind-armor blunt trauma (BABT) even though the impactor is stopped by the body armor. A type of novel composite material through incorporating shear stiffening gel (STG) into ethylene-vinyl acetate (EVA) foam is developed and used as buffer layers to reduce BABT. In this paper, the protective performance of body armors composed of fabric bulletproof layers and a buffer layer made of foam material is investigated both experimentally and numerically. The effectiveness of STG-modified EVA in damage relief is verified by ballistic tests. In parallel with the experimental study, numerical simulations are conducted by LS-DYNA® to investigate the dynamic response of each component and capture the key mechanical parameters, which are hardly obtained from field tests. To fully describe the material behavior under the transient impact, the selected constitutive models take the failure and strain rate effect into consideration. A good agreement between the experimental observations and numerical results is achieved to prove the validity of the modelling method. The tests and simulations show that the impact-induced deformation on the human body is significantly reduced by using STG-modified EVA as the buffering material. The improvement of protective performance is attributed to better dynamic properties and more outstanding energy absorption capability of the composite foam. [ABSTRACT FROM AUTHOR]

In this paper, to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process, specifically designed projectile flight tests with an onboard measurement system were performed. Two projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 g. The onboard-measured time-resolved axial displacement, contact stress and overload values were successfully obtained and analysed. Uniaxial compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties. A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching process. During the launch process, the dummy propellant grain exhibited large deformation due to the high acceleration overload, possibly leading to friction between the motor case and propellant grain. The calculated contact stress showed good agreement with the experimental results, though discrepancies in the overall displacement of the dummy propellant grain were observed. The dynamic mechanical response process of the dummy propellant grain was analysed in detail. The results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study and theoretical analysis on the penetration behavior of a tungsten-alloy long-rod projectile into a concrete target with an impact velocity ranging from 900 to 1,700 m/s. Different penetration regimes are investigated in the experiment in order to have a better understanding of the penetration mechanism of tungsten-alloy projectiles with different impact velocities. The state of the projectiles during penetration and damage parameters of residual projectile and targets are analyzed. Penetration models during abrasion and deforming stages are modified by taking into account of the coupling effects of abrasion, deforming, and shape evolution. Furthermore, the model during the eroding penetration stage is improved to describe the penetration process by considering shape evolution and deforming characteristics of the projectiles. Finally, the improved models are validated against the corresponding experimental results. The results indicate that the crater depth, diameter, and volume of a target are proportional to the impact velocity and impact kinetic energy, separately. The abrasion and deformation of the projectile have a great influence on its penetration process, which cannot be ignored. The calculated depth of penetration (DOP) with different velocities is well-correlated with the experimental results. Residual projectile after erosion penetration still has a greater penetration ability to the concrete target and contributes a larger proportion in the penetration depth. [ABSTRACT FROM AUTHOR]

This paper aims to study the dynamic response and damage of airtight protective doors of nuclear power plants subjected to tornado and wind-borne missile impact. Firstly, a safety performance evaluation method is proposed, considering the structural characteristics of the airtight protective door and relying on support rotation and airtightness. Then, the commercial finite element (FE) program LS-DYNA is utilized to perform the numerical simulations of airtight protective doors in nuclear power plants exposed to tornadoes and wind-borne missile impacts. Subsequently, the parameter analysis method is employed to investigate the impact of keel quantity, size and arrangement, door panel thickness, door core material, and boundary conditions on the dynamic response, airtightness, and failure mode of the airtight protective door. The results show that tornado wind pressure has little effect on the resistance of airtight protective doors and that the impact load of wind-borne missiles plays a leading role. The number and thickness of the keel have significant effects on the force transfer mode and failure mode of airtight protective doors. The thickness of the door panel has a great influence on the damage mode and airtightness of airtight protective doors. The door core improves the local resistance of the airtight protective door to a certain extent, and foam aluminum material has a better energy absorption effect. The change in boundary conditions has little influence on the resistance of airtight protective doors. [ABSTRACT FROM AUTHOR]

During high-speed water-exit of the supercavitating projectile, the cavity interacts with the free surface and collapses, with instantaneous high collapse pressure impacting on the projectile. In order to study the cavity collapse characteristics during high-speed water-exit of the supercavitating projectile, the numerical study based on the Reynolds-averaged equation and the volume of fluid multiphase flow model is conducted in this paper. The results show that the cavity near the free surface will gradually become larger with the movement of the projectile during water-exit of the supercavitating projectile. The existence of attitude angles will cause the asymmetry of cavity to collapse. The cavity on the upstream side will first collapse and generate collapse pressure, while the cavity on the downstream side will collapse later but generate higher collapse pressure. The asymmetry of the cavity collapse becomes stronger with the increasing attitude angles. The time interval of the collapse pressure on the downstream and upstream sides of the projectile becomes shorter close to the projectile tail. [ABSTRACT FROM AUTHOR]

The mass erosion of the kinetic energy of projectiles penetrating concrete targets at high speed is an important reason for the reduction in penetration efficiency. The heat generation and heat conduction in the projectile are important parts of the theoretical calculation of mass loss. In this paper, theoretical models are established to calculate the mass erosion and heat conduction of projectile noses, including models of cutting, melting, the heat conduction of flash temperature, and the conversion of plastic work into heat. The friction cutting model is modified considering the heat softening of metal, and a model of non-adiabatic processes for the nose was established based on the heat conduction theory to calculate the surface temperature. The coupling numerical calculation of the erosion and heat conduction of the projectile nose shows that melting erosion is the main factor of mass loss at high-speed penetration, and the mass erosion ratio of melting and cutting is related to the initial velocity. Critical velocity without melting erosion and a constant ratio of melting and cutting erosion exists, and the critical velocities are closely related to the melting temperature. In the process of penetration, the thickness of the heat affected zone (HAZ) gradually increases, and the entire heat conduction zone (EHZ) is about 5~6 times the thickness of the HAZ. [ABSTRACT FROM AUTHOR]

Aiming at the controllability of spin-stabilized projectile trajectory correction, a new two-dimensional trajectory correction projectile model with a controllable air-ducts structure suitable for the spin-stabilized projectile is proposed in this paper. Furthermore, control strategies of the projectile in the corrected configuration are studied to ensure a stable flight. The correction scheme of the projectile is innovated on the basis of the ram air control mechanism. The air-ducts structure is designed inside the projectile body, and the internal air valve is used to control the lateral air-jet to achieve trajectory correction of the projectile. This is a new two-dimensional trajectory correction scheme with a relatively simple control method. Firstly, the correction mechanism of the new air-ducts structure projectile is analyzed. Secondly, based on the dynamic equation of the projectile, the key parameters of the impulse air valve control, including the safe range of the working pulse width and frequency, are calculated, and the corresponding control strategies are proposed. Finally, the flow field of the projectile in the corrected configuration of the terminal trajectory is numerically simulated, and aerodynamic parameters of the projectile are obtained. Through stability conditions established in this paper and combined with aerodynamic parameters, the validity of the proposed projectile stable flight control strategies is confirmed. The innovations of this paper include: (1) a proposed new aerodynamic configuration model with the air-ducts structure for the spin-stabilized projectile and (2) proposed innovative stable flight control strategies of the corrected configuration projectile. The numerical simulation results show that, compared with the reference projectile without air-ducts structure, the lateral force of the air-ducts structure projectile can produce a radial correction effect on the moving projectile. The simulation results of control strategies indicate that the control strategies can ensure stable flight of the corrected configuration projectile under different conditions. [ABSTRACT FROM AUTHOR]

In order to make the new air duct structure trajectory correction projectile have good dynamic correction control effect, the control strategy of the projectile's correction mechanism is studied in this paper. A design method of trajectory correction control strategy based on particle swarm optimization-cuckoo search (PSO-CS) hybrid algorithm is proposed to obtain the optimal control parameters that can make the projectile flight stable and correct accurately. Firstly, the mathematical model of the air duct structure projectile is established. Secondly, the multiobjective optimization problem is analyzed. The projectile's correction control strategy optimization model is established by taking the start control time, the number of corrections, the correction working time, and the interval time as the control variables. The optimization model innovatively considers the influence of the correction action on the flight stability of the projectile and the influence of the start control time on the correction range. Finally, the PSO-CS hybrid algorithm is used to design the calculation method of the optimization model and solve the optimal correction working parameters. The simulation results indicate that the control strategy optimization model can be solved by the proposed calculation method. Moreover, optimal correction working parameters of the correction mechanism in the current state can be obtained. Compared with the results of using single PSO algorithm and CS algorithm, the correction scheme calculated by PSO-CS hybrid optimization algorithm is better. This correction control scheme can effectively reduce the impact point deviation and make the projectile flight stable. At the same time, the circular error probable (CEP) of the projectile after correction is reduced from 42.3 m to 4.6 m while the impact point dispersion is lowered. The research results show that the design method of correction control strategy proposed in this paper is effective for trajectory correction of the new air duct structure projectile. [ABSTRACT FROM AUTHOR]

The paper presents mathematical modeling of the projectile-induced magnetic field distortion of the speed sensing frame affecting its signal waveform and strength. The electrically conductive projectile is assumed to be nonmagnetic and accelerated in the bore either by a free throwing or in a non-conductive sabot. The paper also presents results of three-dimensional modeling of the magnetic field distribution in the speed sensing frame at different projectile positions. The gap reluctance and the frame signal waveform and strength are calculated herein. It is shown how the projectile shape and size affect the signal waveform and strength. [ABSTRACT FROM AUTHOR]

This paper presents a deep learning approach to estimate a projectile trajectory in a GNSS-denied environment. For this purpose, Long-Short-Term-Memories (LSTMs) are trained on projectile fire simulations. The network inputs are the embedded Inertial Measurement Unit (IMU) data, the magnetic field reference, flight parameters specific to the projectile and a time vector. This paper focuses on the influence of LSTM input data pre-processing, i.e., normalization and navigation frame rotation, leading to rescale 3D projectile data over similar variation ranges. In addition, the effect of the sensor error model on the estimation accuracy is analyzed. LSTM estimates are compared to a classical Dead-Reckoning algorithm, and the estimation accuracy is evaluated via multiple error criteria and the position errors at the impact point. Results, presented for a finned projectile, clearly show the Artificial Intelligence (AI) contribution, especially for the projectile position and velocity estimations. Indeed, the LSTM estimation errors are reduced compared to a classical navigation algorithm as well as to GNSS-guided finned projectiles. [ABSTRACT FROM AUTHOR]

The study of the water entry of successively fired projectiles under a wave environment is of great significance for the development and application of supercavitation weapons. In this paper, the supercavitating flow field of two successively fired projectiles entering water under different wave conditions is numerically simulated by the volume of the fraction model considering the cavitation of water. The motion of projectiles is handled by the overlapping grid technology and the simulated projectiles have six degrees of freedom. The effects of different wave phases and wave heights on the supercavitating flow field and the dynamic loads of the projectiles are studied. The research results show that the wave phase has an effect on the evolution and size of the supercavitation and the effect of the wave phase on the water splash above the free surface is more obvious. The peak of the drag force of the first projectile under conditions of different wave phases with 0.12 m wave height can be reduced by about 50% compared with that under the no-wave condition. The wave phases have an effect on the peak of the drag coefficient, and for the first projectile the peak under the condition of the 180° phase is about 40% lower than that of the 0° phase. The peak of the drag coefficient of the first projectile decreases with the increase in wave height. When the wave height increases from 0.0 m to 0.05 m, the peak value decreases by about 45%. For all conditions, regardless of wave phases or wave heights, the peak of the drag coefficient of the second projectile is obviously much lower than that of the first projectile. Accordingly, the decrease in the velocity of the second projectile is far slower than that of the first one. Negative values of the drag coefficient on the second projectile are observed when the second projectile enters the cavity of the first one. [ABSTRACT FROM AUTHOR]