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In this paper, the tracking control of the air-breathing hypersonic vehicle with model parameter uncertainties and actuator faults is studied. Firstly, a high-order linearization model is used to build an adaptive terminal sliding mode that eliminates chattering and provides increased robustness for unknown disturbances in the system. Second, a fault-tolerant control method mixing the radial basis function neural network with adaptive sliding mode control is suggested, with the addition of a hyperbolic tangent function to avoid controller input saturation. Finally, the stability of the controller is proved strictly by the Lyapunov theory, and the robustness and effectiveness of the controller are further verified by numerical simulations of the longitudinal model of the hypersonic vehicle. [ABSTRACT FROM AUTHOR]

With the rapid development of screen content video applications, screen content coding (SCC) is urgently needed to be used in commercial codecs. However, the extra encoding complexity introduced by the new SCC tools has posed a great challenge for its practical deployment. In this paper, motivated by our observations that there should be a fine-grained mapping between image content and candidate modes, we propose a two-step fast mode decision method to reduce the encoding complexity. First, we propose to use a convolution neural network (CNN) to automatically extract useful features for fine-grained content classification. Second, we build a precise and concise mapping from CUs to candidate modes by simultaneously considering CU content type, CU size, and mode complexity. Note that the spatial correlations between neighboring CUs and current CU are also utilized in candidate modes derivation. In addition to the two-step fast mode decision method, a content-aware early termination algorithm is further proposed to reduce the encoding complexity. Extensive experiments demonstrate that our method achieves better performance compared with state-of-the-art ones, with 50.13% total encoding complexity reduction and only 0.92% BD-rate increase. [ABSTRACT FROM AUTHOR]

A moving mass–actuated unmanned aerial vehicle (MAUAV) is controlled by mass sliders installed inside the airframe and has the advantages of high aerodynamic efficiency and good stealth performance. However, designing a controller for it faces severe challenges due to the strong nonlinearity and coupling of its dynamics. To this end, we proposed an attitude controller based on deep reinforcement learning for the MAUAV. It directly maps the states to the needed deflection of the actuators and is an end-to-end controller. For the sparse reward problem, the reward function required for training is reasonably designed through reward shaping to hasten the algorithm's training speed. In training, random initialization and parameter perturbation are used to strengthen the final policy's robustness further. The simulation results tentatively demonstrate that the proposed controller is not only robust but suboptimal. Compared with an active disturbance rejection controller (ADRC) optimized by the particle swarm algorithm, our controller still guarantees a 100% success rate in multiple unlearned scenarios, meaning it has good generalization ability. [ABSTRACT FROM AUTHOR]

Abstract Moving mass control is a control mechanism dedicated to regulating attitude of airborne vehicles by using motion of internal moving masses. This paper surveys the contemporary progress and problems of moving mass control technology in various capacities including spacecraft, spinning projectiles, underwater vehicles, unmanned aerial vehicles, and re-entry vehicles, special attention is paid to the moving mass configurations and its corresponding layout design methods. In addition, technological difficulties and developmental perspectives in dynamic analysis and attitude control problems of the underlying subject are also analyzed, and suggestions for future augmentation are proposed in the named field. [ABSTRACT FROM AUTHOR]

This paper proposes a novel configuration of the moving mass trim control system with a single moving mass and jet thrusters, which increases the control authority of control system while decreasing its volume and weight requirement. As a stepping stone, dynamics model of a moving-mass flight vehicle and control problem of attitude are formulated. Then, an adaptive controller based on the immersion and invariance approach is designed to guarantee asymptotic stability of the closed-loop system, and a slight improvement is developed to simplify the process. Furthermore, the estimator, which estimates aerodynamic coefficients and unmeasurable terms, is designed without certainty equivalence or linear parameterization. Instead, a procedure is provided to add cross terms between the parameter estimates and the plant states. Also, the associated stability proof is constructive and accomplished by the development of a Lyapunov function. In addition to stability proofs, numerical simulation results in different case are presented to illustrate the performance of the proposed schemes. [ABSTRACT FROM AUTHOR]

Air-breathing hypersonic vehicles have capabilities of hypersonic speed and strong maneuvering, and thus pose a significant challenge to conventional tracking methodologies. To achieve desirable tracking performance for hypersonic targets, this paper investigates the problems related to measurement model design and tracking model mismatching. First, owing to the severe aerothermal effect of hypersonic motion, an infrared measurement model in near space is designed and analyzed based on target infrared radiation and an atmospheric model. Second, using information from infrared sensors, a composite tracking algorithm is proposed via a combination of the interactive multiple models (IMM) algorithm, fitting dynamics model, and strong tracking filter. During the procedure, the IMMs algorithm generates tracking data to establish a fitting dynamics model of the target. Then, the strong tracking unscented Kalman filter is employed to estimate the target states for suppressing the impact of target maneuvers. Simulations are performed to verify the feasibility of the presented composite tracking algorithm. The results demonstrate that the designed infrared measurement model effectively and continuously observes hypersonic vehicles, and the proposed composite tracking algorithm accurately and stably tracks these targets. ©2018 SPIE and IS&T [DOI: 10.1117/1.JEI.27.2.023023] [ABSTRACT FROM AUTHOR]

This paper studies a novel guidance framework of the vehicle against a high-speed and maneuvering target based on deep reinforcement learning (DRL) considering the energy consumption, autopilot lag dynamics, and input saturation, which can effectively cope with the high flight-path angle error flight phase and various uncertainties. The guidance framework proposes an end-to-end mapping transformation between the guidance command and observation states consisting of line-of-sight (LOS) angle, relative distance, and their rate measured by the seeker. At the same time, the observability of the LOS angle and relative distance is included in constructing the reward function. Besides, the relative engagement kinematic model of the interceptor-target is established and combined with the PPO guidance algorithm, jointly described as a Markov decision process (MDP). Notably, the guidance framework is optimized using the improved proximal policy optimization (PPO) algorithm and demonstrated in a simulated terminal phase in the near-space. Specifically, the PPO guidance algorithm is structured by the policy (actor) neural network and the critic neural network, and both are standard fully-connected neural networks. Subsequently, observation states and rewards are fully collected and applied by introducing the experience replay method. Also, the exponential decay learning rate method, mini-batch stochastic gradient ascent (SGA) method, zero-score standardization, and Adam optimizer are proposed to train the reinforcement learning algorithm more efficiently. Moreover, the proposed guidance framework has an excellent generalization capability and guarantees the implementation of fixed and stochastic engagement scenarios, which means that the interceptor can realize the unlearned practical combat scenarios. The robust capacity is indicated and validated using Monte Carlo simulation under various uncertainties. Moreover, the DRL guidance framework can satisfy the onboard application requirement. [ABSTRACT FROM AUTHOR]

In terms of the moving mass control technology, the configuration of internal moving masses is a key challenge. In order to reduce the complexity of configuring these moving masses in a flight vehicle, a combination bank-to-turn control mode with the single moving mass and reaction jet is proposed in this paper. To investigate the dynamics and the potential of the control mechanism, an attitude dynamic model with single moving mass is generated. The dynamic analysis indicates that the control stability, control authority and dynamic behavior of the pitch channel are determined by the mass ratio of the moving mass to the system and the difference between the mass center of the moving mass and the mass center of the vehicle body. Interestingly, control authority increases proportionally with increasing mass ratio and also with decreasing the magnitude of the static margin. To deal with the coupling caused by the additional inertia moment which is generated by the motion of the moving mass, an adaptive control law by using dynamic inversion theory and the extended state observer is designed. Also, a compensator is designed for eliminating the influence of the servo actuator's dynamics on attitude of the flight vehicle. Finally, the simulation results validate the quality of the proposed adaptive controller which ensures a good performance in the novel configuration with internal moving mass. [ABSTRACT FROM AUTHOR]

This study presents a novel integrated guidance and control method for near space interceptor, considering the coupling among different channels of the missile dynamics, which makes the most of the overall performance of guidance and control system. Initially, three-dimensional integrated guidance and control model is employed by combining the interceptor-target relative motion model with the nonlinear dynamics of the interceptor, which establishes a direct relationship between the interceptor-target relative motion and the deflections of aerodynamic fins. Subsequently, regarding the acceleration of the target as bounded uncertainty of the system, an integrated guidance and control algorithm is designed based on robust adaptive backstepping method, with the upper bound of the uncertainties unknown. Moreover, a nonlinear tracking differentiator is introduced to reduce the “compute explosion” caused by backstepping method. It is proved that tracking errors of the state and the upper bound of the uncertainties converge to the neighborhoods of the origin exponentially. Finally, simulations results show that, compared to the conventional guidance and control design, the algorithm proposed in this paper has greater advantages in miss distance, required normal overload, and flight stability, especially when attacking high-maneuvering targets. [ABSTRACT FROM AUTHOR]

A strapdown inertial navigation system and celestial navigation system integrated autonomous navigation scheme is proposed in this paper, using the navigation information obtained from Earth sensors and star sensors. To eliminate the adverse effect caused by the asymmetry of Earth infrared radiance, the relationship between Earth infrared radiance brightness and effective horizon height is found. According to the relationship as well as the measuring principle of the Earth sensor, this paper derives a function to correct the measurement of the Earth sensor. Then, the angle-distance of stars can be calculated, and using this information, we can estimate the navigation information of a ballistic missile by least square estimation. The simulation results show that the error of Earth infrared radiance has a great effect on the navigation precision, and by using the correction scheme, this adverse effect can be greatly mitigated. This correction scheme is available and effective. [ABSTRACT FROM AUTHOR]

Estrogen substances in the environment are increasing dramatically, which interfere with the normal hormone level of human body, lead to the disorder of endocrine system and even cancer. It is difficult to screen a large number of environmental estrogen substances by existing estrogen effect detection methods, and the results are often affected by many factors, thus the development of new method has become an urgent task. Electrochemical method is promising to reflect cell proliferation by tracking intracellular purine bases directly. In this study, the estrogen level in MCF-7 cells on multiwall carbon nanotubes modified glassy carbon electrode (MWCNTs/GCE) could be tracked simply and conveniently, and the estrogen effect of estradiol could be reflected by electrochemistry in time and dose-dependent manners. Electrochemical method displayed the best tolerance to culture factors, such as different cell densities, serum types, culture medium types and serum estrogen-free methods, which responsed to estrogen effect higher than MTT (about 40%) and cell counting methods (about 50%). Further Western blotting analysis showed that the estrogen effect of estradiol promoted purine catabolism and up-regulated guanine deaminase (GDA) and adenine deaminase (ADA) expression, the key enzymes of purine catabolism pathway, in a dose-dependent manner. The up-regulation of GDA and ADA led to the increase of intracellular guanine and xanthine, which enhanced the electrochemical signal derived from guanine and xanthine. [Display omitted] • Electrochemistry could track estrogen level in MCF-7 cells simply and conveniently. • Electrochemistry displayed excellent environment tolerance compared to other methods. • E2 estrogen effect up-regulated GDA and ADA expression in purine catabolism pathway. [ABSTRACT FROM AUTHOR]

Geopolymer is widely used as a supplement to cementitious composites because of its advantages of low carbon and environmental protection, and geopolymer concrete is also broadly used in practical engineering. In recent years, geopolymer concrete has attracted increasing interest owing to its superior mechanical properties, and a series of research results have been obtained. In this paper, from the preparation of geopolymer concrete, based on the characteristics that geopolymer concrete is brittle and easy to crack, the types and basic properties of fibers to enhance the toughness of concrete are analyzed, the advantages and disadvantages of different fibers used as a material to enhance the toughness of concrete are summarized, and we review the effects of type, shape, volume rate, aspect ratio, and hybrid fiber combinations on the static mechanical properties. The results indicate that fibers have significant potential to enhance the compressive strength, splitting tensile strength, flexural strength, and fracture toughness of geopolymer concrete, and the optimal fiber volume rate seems to be related to the fiber type. Whereas the effect of aspect ratio and hybrid fiber combinations on the properties of geopolymer concrete seems to be obvious. This paper reviews the influence of fiber on the basic mechanical properties of geopolymer concrete, which provides a solid foundation to promote the further development and application of the research on the toughness of fiber-reinforced geopolymer concrete and provides recommendations for future research. [ABSTRACT FROM AUTHOR]

Abstract: Moving mass is one of the control actuators, whose configuration in the warhead is the basis of application in engineering for moving mass control technology. The servo forces, which drive the moving mass to move, affect the translational and rotational motion of the missile. It not only could increase the moving range of the center of system mass, but also reduce the requirement for the roll channel. Firstly, a single moving mass control mode, which consists of the rotation of rail around the longitudinal body-axis and the translation of the moving mass along the rail, is presented. Then, the 8-DOF dynamic model is established and the coupling characteristics between the attitude control and the servo-loop control are analyzed in this paper. Based on the above analysis, the attitude tracking control law is designed by using sliding mode theory. Finally, the problem about the terminal guidance of reentry vehicle is studied by numerical simulation: the state of moving mass is controlled by the servo force, and the missile attitude is controlled by adjusting the position of moving mass so that the excepted overload designed by using the proportion guidance could be tracked exactly. The simulation results verify the validity of the proposed method. [Copyright &y& Elsevier]

The maneuver modes in the glide phase are explored from the perspective of hypersonic vehicle defense in this study, and a novel maneuver mode description approach is proposed. The longitudinal and lateral maneuver modes' mechanisms and evolution laws are explored. And, the focus of this research is on the evolution laws of complex lateral maneuver modes in real scenarios. To solve the maneuver mode description problems, a novel maneuver mode parametric analyzing and modeling method is proposed based on the Vector Auto-regressive model. Firstly, the Granger causality test is adopted to verify whether there are causal correlations between the maneuver characteristic parameter series, which have a high level of regularity and are taken as modeling variables. Then, the Vector Auto-regressive method is employed to model the coupling relationship between the maneuver characteristic parameters, as well as to provide a precise description method with simple structure and uniform form for various maneuver modes. Moreover, the model coefficients estimation and model order selection methods are presented. This study helps to deepen the understanding of the target's maneuver modes in hypersonic vehicle defense. Simulation results demonstrate that the proposed modeling method can greatly improve modeling accuracy. [ABSTRACT FROM AUTHOR]

Three-channel attitude motion of an underactuated flight vehicle with laterally configured single moving mass is investigated. Of particular interest are three interrelated issues, first, the discussion of longitudinal static stability and trim angle-of-attack considering the lack of active control input in the pitch channel, second, the problem of channel cross coupling and moving mass inertial coupling, third, the coupling control using the single moving mass offset to achieve command roll angle tracking and side slip angle stabilization for the underactuated system. Nonlinear dynamic analysis indicates that the longitudinal static stability and the trim angle-of-attack are determined by the installation position and the mass ratio of the moving mass, interestingly, installing the moving mass at the center-of-mass of the vehicle body not only makes the trim angle-of-attack insensitive to flight conditions and the mass ratio, but also can ensure the longitudinal static stability over a large range of the mass ratios. Moreover, analysis of three-channel coupling dynamics reveals that the entire system may experience oscillation even divergence when initial disturbance of side slip angle and frequent offset of the moving mass exist. Therefore, an improved underactuated active disturbance rejection controller is proposed to deal with the roll-yaw coupling control problem, and the stability of which is analyzed, additionally, the multiple controller parameters are optimized based on the particle swarm optimization algorithm. Closed-loop simulation results in different cases prove the effectiveness and robustness of the designed controller. The proposed control scheme sufficiently utilizes the control capability of the single moving mass to enhance the anti-disturbance ability of the flight vehicle system, which permits the economic benefits and application prospects. [ABSTRACT FROM AUTHOR]

• This paper explores a three-dimensional tracking guidance strategy against high-maneuvering hypersonic vehicles. • The proposed guidance method utilizes a velocity control channel to increase tracking precision. • The wind field is accurately modeled to simulate the actual environment in the near-space to prevent impractical scenarios. • The backpropagation neural network extended state observer is proposed to estimate the uncertainty disturbance and design an adaptive control law to compensate for the tracking errors. • The proposed strategy combines fast nonsingular terminal sliding mode control and adaptive techniques to improve non-singularity, tracking accuracy, and estimation precision. This paper presents a three-dimensional disturbance observer-based adaptive tracking guidance scheme for the trajectory tracking problem of a missile intercepting a hypersonic vehicle with the wind field, autopilot lag dynamics, and input saturation. Unlike most of the existing missile trajectory tracking guidance systems without velocity controllability and external wind field model, the wind field model is added to the dynamic model, and the velocity control channel is introduced into the three-dimensional trajectory tracking guidance problem to prevent impractical scenarios and increase tracking precision. The proposed tracking guidance methodology incorporates the sliding mode and adaptive control techniques, in which the sliding mode motion is finite time stable independently of the tracking guidance system's initial conditions. Also, the super twisting switch control law is added to cope with the chattering problem. In this context, external uncertainty disturbances and unmeasured states are lumped into lump disturbance and estimated using the backpropagation neural network extended state observer. To this end, numerical simulations demonstrate the tracking to reach zero between 3 s and 5 s against various uncertainties in engineering practical, and position tracking errors are within 0.15 m, superior to the existing tracking guidance methods. [ABSTRACT FROM AUTHOR]

In this paper, a variable-structure multimodel (VSMM) filtering algorithm based on the long short-term memory (LSTM) regression-deep Q network (L-DQN) is proposed to accurately track strong maneuvering targets. The algorithm can map the selection of the model set to the selection of the action label and realize the purpose of a deep reinforcement-learning agent to replace the model switching in the traditional VSMM algorithm by reasonably designing a reward function, state space, and network structure. At the same time, the algorithm introduces a LSTM algorithm, which can compensate the error of tracking results based on model history information. The simulation results show that compared with the traditional VSMM algorithm, the proposed algorithm can quickly capture the maneuvering of the target, the response time is short, the calculation accuracy is significantly improved, and the range of adaptation is wider. Precise tracking of maneuvering targets was achieved. [ABSTRACT FROM AUTHOR]

Nonlinear guidance law guaranteeing convergence before attainment of desired line-of-sight (LOS) range in the background of reentry vehicle attacking a moving target on the ground is studied in this paper. Initially, a novel guidance model is established in which LOS range is treated as an independent variable, describing the relative motion between the vehicle and the target. The guidance model includes two differential equations that describe LOS's pitch and yaw motions in which the pitch motion is separately decoupled. Subsequently, guidance laws with disturbance suppression of the pitch and yaw motion of LOS are designed separately, and presented in the form of normal overload. Compared with traditional guidance laws, the proposed one guarantees that LOS angular rate converges to zero before LOS range decreases to the desired value. Finally, the correctness and validity of the guidance model and guidance law are verified by numerical simulation. The guidance model and guidance law proposed in this paper provide a new way for the design of fast convergent guidance law. [ABSTRACT FROM AUTHOR]

Combustion of heavy oil fly ash (HOFA) blended with municipal sewage sludge (MSS) in existing infrastructures may be a sustainable waste management strategy. In this work, the co-combustion of HOFA and MSS with mass ratios from 80/20 to 60/40 is investigated by TGA-FTIR to identify the thermal behaviors (combustion process, ignition and burnout characteristics) and gaseous emissions. Results indicate that co-combustion of HOFA and MSS is better than mono-combustion. MSS induces lower ignition temperatures of the blends, while HOFA tends to decrease the burnout temperatures. The ignition and comprehensive combustibility indices reach the maximum (1.78 × 10 −5 % min −1 K −2 , 2.66 × 10 −8 % 2 min −2 K −3 ) in the mixture with HOFA/MSS ratio of 80/20. The co-combustion characteristics of blends are synergistically influenced by HOFA and MSS. Moreover, the CaO originated from MSS contributes to the desulfurization effect to retain the SO 2 emission. [ABSTRACT FROM AUTHOR]

The inertial navigation system is aligned and leveled before the launch of a long-range vehicle. However, the non-uniformity of the Earth can lead to initial state errors including initial positioning errors and initial orientation errors, causing navigation errors in flight dynamics and eventually impact-point deviations up to approximately 1 km. In order to analyze the propagation mechanisms of initial state errors and rapidly estimate their influence magnitudes, navigation perturbation equation subject to apparent acceleration coupling is established based on state space perturbation theory in the launch inertial coordinate system. Afterwards, a series of analytical form of deviations are derived including gravitational acceleration deviation, apparent acceleration projection deviation, apparent acceleration coupling deviation, initial velocity errors and initial position errors. Then, the analytical propagation model of engine-cutoff state deviations and impact-point deviations are acquired by solving the navigation perturbation equation. In the simulations, computer codes are programmed to calculate the propagation matrices of engine-cutoff state deviations and impact-point deviations in the case of fixed launch azimuth, followed by the propagation mechanism analyses of initial state errors. Next, two more scenarios of different launch azimuths and different launch points are simulated to further verify the reliability of the proposed analytical propagation model. The results show that analytical solutions of the propagation model proposed in this paper can well coincide with numerical solutions, with relative errors being all less than 1%, which is also suitable for multiple distinct simulation scenarios compared with previous methods. [ABSTRACT FROM AUTHOR]

Some heavy metals in the environment may have estrogen-like activity, which probably lead to major diseases such as breast cancer. It is of great importance to establish new methods to evaluate the estrogen effect of heavy metals from multiple angles due to the complex mechanism of estrogen effect. In this paper, using MCF-7 cells as model, the electrochemical detection mechanism of the estrogen effect of heavy metal cadmium (Cd) was studied. The two electrochemical signals of MCF-7 cells derived from uric acid (0.30 V) and the mixture of guanine and xanthine (0.68 V) increased in a time and dose-dependent manner when MCF-7 cells induced by Cd, reaching the maximum at 96 h and 10−9 mol L−1. Further studies found that three purine metabolism pathways about de novo synthesis, salvage synthesis and decomposition metabolism were activated by the estrogen effect of Cd. The expression of PRPP amidotransferase in purine de novo synthesis pathway and HPRT in purine salvage synthesis pathway up-regulated, especially HPRT, which promoted cell proliferation together. Nevertheless, the expression of GDA and ADA, the key enzymes in purine decomposition metabolism pathway, up-regulated in a time and dose-dependent manner, which had same tendency with that of ERα, thereby increased the content of intracellular hypoxanthine, guanine, xanthine and uric acid, and enhanced electrochemical signals. [Display omitted] • Cd induced purine de novo and salvage synthesis, especially salvage synthesis. • Both purine de novo and salvage synthesis provided energy for cell proliferation. • Purine catabolism was induced by Cd in a time-dependent manner. • Purine metabolism induced by Cd enhanced electrochemical signals. [ABSTRACT FROM AUTHOR]

This paper investigates the maneuvering target interception problem considering terminal angle constraint, the input saturation and the second-order autopilot lag with the unavailable missile's acceleration. The considering problem is formulated as an output feedback control problem of a four-order nonlinear uncertain weakly observable system, which is challenging to address by general composite methods directly. Hence, the liner normal equivalent control model of the original guidance system is firstly derived to facilitate the extended state observer (ESO) based method design. Then, a nonlinear ESO is introduced to estimate the unmeasured system states and modeled disturbances as well as compensate for control saturation. Thereafter, the ESO-based guidance scheme is developed by integrating a novel four-order integral sliding mode manifold and an adaptive improved super-twisting algorithm. The main novelty is that a novel integral sliding mode manifold is proposed to replace the linear sliding mode manifold of super-twisting sliding mode to further reduce the convergent time of closed-loop system states. Besides, the conventional super-twisting algorithm is improved by modifying the reaching law and designing the adaptive gains to guarantee the continuity of guidance command and suppress the large constant gains and parameter uncertainties. Notably, only the output relative information is utilized in its design process. Numerical simulations validate the previous analyses and show the superiorities in reducing the energy consumption in high maneuvering target interception and achieving robustness to a certain margin under various uncertainties. [ABSTRACT FROM AUTHOR]

This paper concerns the attitude dynamics and control synthesis of fixed-trim moving mass reentry vehicle (MMRV) suffering from stochastic uncertainties. In order to enhance the roll maneuverability, a new high-mass-ratio configuration is proposed and analyzed. The attitude dynamic analysis presents that the steady-state angle of attack and the interference on yaw channel increase with the mass ratio of moving mass to the whole aircraft as well as the distance between the moving mass mass centre and the vehicle body mass centre. Also, the roll control authority and roll maneuverability are proved to be enhanced when the mass ratio is higher. Considering the practical multi-source disturbances caused by aerodynamic parameter perturbation and stochastic disturbances, the parameter adaptive law and extended state observers (ESOs) are introduced into the control scheme and developed through backstepping design procedure. Meanwhile, an auxiliary system is introduced to compensate for the control saturation caused by the limitation on the moving mass deflection angle. With the aid of Lyapunov function and Ito differential rule, the adaptive backstepping ADRC controller is designed with a guarantee of uniformly ultimate boundness (UUB) of the closed-loop tracking error in mean square. Simulation results are presented to demonstrate the validity and superiority of the proposed configuration and controller. [ABSTRACT FROM AUTHOR]

This paper proposes an online midcourse guidance method for boost phase interception. Dynamic models are established and flight constraints are analyzed firstly. Handover constraints between midcourse and terminal guidance are transformed as an optimization problem by introducing additional optimization variables in this paper. Then midcourse guidance problem can be transformed as an optimization problem with constraints. It can be solved by convex programming through constraints relaxation and linearization. In order to overcome flight uncertainty and changes of target trajectory, an online guidance framework based on convex programming is presented. But it takes some calculation time to solve the convex programming problem, which causes the delay of guidance commands. Based on sensitivity analysis of nonlinear programming, a command correction method is designed to reduce the delay effect. Besides, an adaptive update strategy of trust region in convex programming is proposed to guarantee calculation accuracy and speed. And the discrete points are continuously updated with the flight time to improve calculation efficiency. Finally, numerical simulations for different cases have demonstrated the effectiveness of the online midcourse guidance method proposed. [ABSTRACT FROM AUTHOR]

Trajectory planning method for the entire recovery process of the reusable launch vehicle is studied. Firstly, a revised trajectory correction method (RTCM) is proposed to reduce the maximum normal aerodynamic load in the endo-atmosphere unpowered descent phase and improve the vehicle's landing accuracy on the influence of wind field. It consists of two parts, namely moving the ignition point of the vertical landing phase on the horizontal plane and introducing preset steady wind field into trajectory planning. Secondly, a compound trajectory planning method, which combines Particle Swarm Optimization algorithm (PSO) with Polynomial Guidance Law (PGL), is proposed to complete the optimization task of the entire recovery process. Employing PSO algorithm can avoid the complex calculation of additional angle of attack caused by the preset steady wind field in traditional trajectory correction. To overcome the premature convergence of basic PSO, the traditional re-initialization mechanism is improved. Finally, the guidance simulation of two phases greatly affected by wind is accomplished. The effectiveness of the proposed methods is demonstrated with some scenarios and Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

In recent years, the new type design of current transformer with bushing structure has been widely used in the distribution network system due to its advantages of miniaturization, high mechanical strength, maintenance-free, safety and environmental protection. The internal temperature field distribution is an important characteristic parameter to characterize the thermal insulation and aging performance of the transformer, and the internal temperature field distribution is mainly derived from the joule heat generated by the primary side guide rod after flowing through the current. Since the electric environment is a transient field and the thermal environment changes slowly with time as a steady field under the actual conditions, it is more complex and necessary to study the electrothermal coupling field of current transformer (CT). In this paper, a 3D simulation model of a new type design of current transformer for distribution network based on electric-thermal coupling is established by using finite element method (FEM) software. Considering that the actual thermal conduction process of CT is mainly by conduction, convection and radiation, three different kinds of boundary conditions such as solid heat transfer boundary condition, heat convection boundary condition and surface radiation boundary condition are applied to the CT. Through the model created above, the temperature rise process and the distribution characteristics of temperature gradient of the inner conductor under different current, different ambient temperatures and different core diameters conditions are studied. Meanwhile, the hottest temperature and the maximum temperature gradient difference are calculated. According to this, the position of weak insulation of the transformer is determined. The research results can provide a reference for the factory production of new type design of current transformer. [ABSTRACT FROM AUTHOR]

The configuration of internal moving masses is a significant research challenge in design and development of moving-mass actuated flight vehicle. Combining the advantages of rotating moving mass and translating moving mass, a novel configuration with a translating moving mass and rotating rail is proposed in this paper. This type of control mode can not only optimize the vehicle internal space, but also preclude the elevator and rudder ablation. In order to investigate the control authority and dynamics of the control mechanism, the exact dynamic model considering the mass and moment of inertia of rail is established. The influence of the rail rotation and moving mass translation on attitude and trajectory maneuvering authority of flight vehicle is investigated and evaluated. The simulation results demonstrate that moving mass control mechanism with a single moving mass and rotational rail is an effective control mechanism which produce significant control authority for the flight vehicle and can be controlled with a good tracking performance in the presence of uncertainties and inertial coupling. [ABSTRACT FROM AUTHOR]

This work presents a novel real integrated guidance and control (IGC) scheme that solves the issues of underactuation, fixed-trim angle-of-attack and three-dimensional motion together for moving mass flight vehicles (MMFVs). Firstly, an underactuated IGC model containing the information of flight vehicle dynamics and three-dimensional relative motion is formulated, and the command error angle is designed to improve the capability of maneuvering penetration. Secondly, the modeled disturbances and uncertainties are regarded as the lumped disturbances, the values and derivatives of which are estimated by four second-order disturbance observers (DOs). Thirdly, different from the traditional backstepping-based partial IGC scheme, a novel sliding mode based real IGC law is designed, which generates the command moving mass offset input by only a single controller, thereby essentially eliminating the cross time-scale problem between the guidance and control loops. Moreover, this IGC law simultaneously achieves the command error angle tracking and the side-slip-angle stabilization with only a control input. Finally, the Lyapunov function is used to illustrate the asymptotic stability of the entire system, and numerical simulations with multiple disturbances, varied flying circumstances, and a comparison with other control strategies are carried out to show the effectiveness and superiority of the proposed IGC strategy. [ABSTRACT FROM AUTHOR]

Abstract The configuration of internal moving masses is a key challenge for applying moving mass control technology to flight vehicle control. A novel configuration with a large mass ratio moving mass and reaction jets is proposed for bank-to-turn control. The control system of the proposed configuration consists of the attitude dynamics and the moving mass dynamics, which are coupled by the additional inertia moment of moving mass. To deal with the coupling, the integrated control of an attitude-servo system and a lateral underactuated control based on immersion and invariance theory is presented. To overcome the uncertainties in the flight vehicle model, immersion and invariance theory is employed to design an estimator for the unknown aerodynamic parameters. The estimator has an additional nonlinear term which adjusts the performance of the estimation error. The simulation results show that the proposed attitude-servo controller for the longitudinal subsystem can enhance the response of the system and the underactuated controller of the lateral subsystem can reduce fuel consumption. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a quasi-Euler-angle-based phase plane attitude switching control law (PPASCL) is introduced to control the Orbital Transfer Vehicle (OTV) during the separation process between the OTV and the released satellite/payload. In particular, three reverse-jet thrusters serve to separate the OTV from the unlatched satellite, and in the case that the center of mass of the OTV does not coincide with its body axis, the resulted reverse-jet force will impact the attitude of the OTV, it is thus necessary to employ the large-thrust attitude control nozzles in this scenario. Due to the fact that the opposite two large-thrust nozzles could not fire simultaneously, the adjacent nozzles have to be employed together to control either the pitch or the yaw channel as well as to reduce the disturbance imposing on the roll axis. Moreover, a time-shared attitude control scheme (TCS) is adopted in practical implementation. Simulation results show that the proposed PPASCL and TCS are feasible and effective. In addition, when the regulating coefficients are properly specified, a smooth and safety separation can be ensured. [Copyright &y& Elsevier]

The article presents a study to investigate the formation of an iron-copper-gold (uranium) (IOCG- U) metallogenic system located in the Luzong Volcanic Basin, Anhui Sheng, China. It mentions wall rock alterations in IOCG deposits including sodic alteration in depth, potassic alteration in shallow level and sericitization and silicide alteration at superficial level and formation of intrusions and volcanic rocks which indicates the subduction of oceanic crust to east China continent.