To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D lea...To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D leader-following cooperative interception guidance law.First,in the LOS direction of the leader,an impact time-controlled guidance law is derived based on the fixed-time stability theory,which enables the leader to complete the interception task at a prespecified impact time.Next,in the LOS direction of the followers,by introducing a time consensus tracking error function,a fixed-time consensus tracking guidance law is investigated to guarantee the consensus tracking convergence of the time-to-go.Then,in the direction normal to the LOS,by combining the designed global integral sliding mode surface and the second-order Sliding Mode Control(SMC)theory,an innovative 3D LOS-angle-constrained interception guidance law is developed,which eliminates the reaching phase in the traditional sliding mode guidance laws and effectively saves energy consumption.Moreover,it effectively suppresses the chattering phenomenon while avoiding the singularity issue,and compensates for unknown interference caused by target maneuvering online,making it convenient for practical engineering applications.Finally,theoretical proof analysis and multiple sets of numerical simulation results verify the effectiveness,superiority,and robustness of the investigated guidance law.展开更多
In consideration of the field-of-view(FOV)angle con-straint,this study focuses on the guidance problem with impact time control.A deep reinforcement learning guidance method is given for the missile to obtain the desi...In consideration of the field-of-view(FOV)angle con-straint,this study focuses on the guidance problem with impact time control.A deep reinforcement learning guidance method is given for the missile to obtain the desired impact time and meet the demand of FOV angle constraint.On basis of the framework of the proportional navigation guidance,an auxiliary control term is supplemented by the distributed deep deterministic policy gradient algorithm,in which the reward functions are developed to decrease the time-to-go error and improve the terminal guid-ance accuracy.The numerical simulation demonstrates that the missile governed by the presented deep reinforcement learning guidance law can hit the target successfully at appointed arrival time.展开更多
This study presents a novel impact time and angle constrained guidance law for homing missiles. The guidance law is first developed with the prior-assumption of a stationary target, which is followed by the practical ...This study presents a novel impact time and angle constrained guidance law for homing missiles. The guidance law is first developed with the prior-assumption of a stationary target, which is followed by the practical extension to a maneuvering target scenario. To derive the closed-form guidance law, the trajectory reshaping technique is utilized and it results in defining a specific polynomial function with two unknown coefficients. These coefficients are determined to satisfy the impact time and angle constraints as well as the zero miss distance. Furthermore, the proposed guidance law has three additional guidance gains as design parameters which make it possible to adjust the guided trajectory according to the operational conditions and missile's capability. Numerical simulations are presented to validate the effectiveness of the proposed guidance law. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.展开更多
A feasible guidance scheme with impact time constraint is proposed for attacking a stationary target by missiles with time-varying velocity.The main idea is to replace the constant velocity with the future mean veloci...A feasible guidance scheme with impact time constraint is proposed for attacking a stationary target by missiles with time-varying velocity.The main idea is to replace the constant velocity with the future mean velocity;therefore, the existing time-to-go estimation algorithm of the proportional navigation guidance law can be improved to adapt to varying conditions.In order to obtain the prediction of the velocity profile, the velocity differential equation to the downrange is derived, which can be numerically integrated between the current downrange and the target position by the on-board computer.Then, a third-order polynomial is introduced to fit the velocity profile in order to calculate the future mean velocity.At the beginning of each guidance loop, the future mean velocity is predicted and the time-to-go information is updated, based on which a novel biased proportional navigation guidance law is established to achieve the impact time constraint.Finally,numerical simulation results verified the effectiveness of the time-to-go estimation algorithm and the proposed law.展开更多
This paper proposes a new three-dimensional optimal guidance law for impact time control with seeker’s Field-of-View(FOV) constraint to intercept a stationary target. The proposed guidance law is devised in conjuncti...This paper proposes a new three-dimensional optimal guidance law for impact time control with seeker’s Field-of-View(FOV) constraint to intercept a stationary target. The proposed guidance law is devised in conjunction with the concept of biased Proportional Navigation Guidance(PNG). The guidance law developed leverages a nonlinear function to ensure the boundedness of velocity lead angle to cater to the seeker’s FOV limit. It is proven that the impact time error is nullified in a finite-time under the proposed method. Additionally, the optimality of the biased command is theoretically analyzed. Numerical simulations confirm the superiority of the proposed method and validate the analytic findings.展开更多
This paper analyses the issue of impact time control of super-cavitation weapons impact fixed targets which mainly refer to the ships or submarines who lost power, but still have combat capability. Control over impact...This paper analyses the issue of impact time control of super-cavitation weapons impact fixed targets which mainly refer to the ships or submarines who lost power, but still have combat capability. Control over impact time constraints of guidance law(ITCG) is derived by using sliding mode control(SMC) and Lyapunov stability theorem. The expected impact time is realized by using the notion of attack process and estimated time-to-go to design sliding mode surface(SMS). ITCG contains equivalent and discontinuous guidance laws, once state variables arrive at SMS,the equivalent guidance law keeps the state variables on SMS,then the discontinuous guidance law enforces state variables to move and reach SMS. The singularity problem of ITCG is also analyzed. Theoretical analysis and numerical simulation results are given to test the effectiveness of ITCG designed in this paper.展开更多
An impact-time-control guidance law is required for the simultaneous attack of suicide attack unmanned aerial vehicles.Based on the nonlinear model,a two-phase guidance strategy is proposed.The impact time is derived ...An impact-time-control guidance law is required for the simultaneous attack of suicide attack unmanned aerial vehicles.Based on the nonlinear model,a two-phase guidance strategy is proposed.The impact time is derived in a simple analytical form of initial states and switching states,and it can be controlled by switching at an appropriate range.Firstly,a two-phase guidance law is designed to make the magnitude of the heading error decrease monotonically from its initial value to zero.And then,the feasible interval of the switching ranges and of the impact times under the acceleration constraint are given analytically in sequence.Furthermore,a general form of twophase guidance law is proposed,which allows the magnitude of the heading error to increase in the first phase,to improve the applicability of the methodology.Having the same structure as proportional navigation guidance with a time-varying gain,the proposed algorithms are simple and easy to implement.The corresponding feedback form is presented for realistic implementation.When a predefined impact time is taken within its permissible set,the constraints on the acceleration and fieldof-view will not be violated during the interception.Finally,simulations validate the effectiveness of the methodology in impact time control and salvo attack.展开更多
A novel closed-form guidance law with impact time and impact angle constraints is pro- posed for salvo attack of anti-ship missiles, which employs missile＇s normal acceleration （not jerk） as the control command dir...A novel closed-form guidance law with impact time and impact angle constraints is pro- posed for salvo attack of anti-ship missiles, which employs missile＇s normal acceleration （not jerk） as the control command directly. Firstly, the impact time control problem is formulated as tracking the designated time-to-go （the difference between the designated impact time and the current flight time） for the actual time-to-go of missile, and the impact angle control problem is formulated as tracking the designated heading angle for the actual heading angle of missile. Secondly, a biased proportional navigation guidance （BPNG） law with designated heading angle constraint is constructed, and the actual time-to-go estimation for this BPNG is derived analytically by solving the system differential equations. Thirdly, by adding a feedback control to this constructed BPNG to eliminate the time-to-go errorthe difference between the standard time-to-go and the actual time-to-go, a guidance law with adjustable coefficients to control the impact time and impact angle simultaneously is developed. Finally, simulation results demonstrate the performance and feasibility of the proposed approach.展开更多
To improve applicability and adaptability of the impact time control guidance(ITCG) in practical engineering, a twostage ITCG law with simple but effective structure is proposed based on the hybrid proportional naviga...To improve applicability and adaptability of the impact time control guidance(ITCG) in practical engineering, a twostage ITCG law with simple but effective structure is proposed based on the hybrid proportional navigation, namely, the pureproportional-navigation and the retro-proportional-navigation.For the case with the impact time error less than zero, the first stage of the guided trajectory is driven by the retro-proportionalnavigation and the second one is driven by the pure-proportionalnavigation. When the impact time error is greater than zero, both of the stages are generated by the pure-proportional-navigation but using different navigation gains. It is demonstrated by twoand three-dimensional numerical simulations that the proposed guidance law at least has comparable results to existing proportional-navigation-based ITCG laws and is shown to be advantageous in certain circumstances in that the proposed guidance law alleviates its dependence on the time-to-go estimation, consumes less control energy, and adapts itself to more boundary conditions and constraints. The results of this research are expected to be supplementary to the current research literature.展开更多
Aiming at the problem of high-precision interception of air-maneuvering targets with impact time constraints,this paper proposes a novel guidance law based on a nonlinear virtual relative model in which the origin is ...Aiming at the problem of high-precision interception of air-maneuvering targets with impact time constraints,this paper proposes a novel guidance law based on a nonlinear virtual relative model in which the origin is attached to the target.In this way,the original maneuvering target is transformed into a stationary one.A polynomial function of the guidance command in the range domain with two unknown coefficients is introduced into the virtual model,one of the coefficients is determined to achieve the impact time constraint,and the other is determined to satisfy a newly defined virtual look angle constraint.For meeting the terminal constraints simultaneously,the guidance command can finally be obtained.The resulting solution is represented as a combination of proportional navigation guidance-like term which is aimed to meet the zero miss distance constraint,a bias term for impact time control by adjusting the length of the homing trajectory,and an additional term for target maneuvers.Numerous simulations demonstrate that the proposed law achieves an acceptable impact time error for various initial conditions against different types of maneuvering targets and shows more effective performance in comparison with those of other existing guidance laws.展开更多
The problem of guidance law is investigated for multiple interceptors to attack a target cooperatively.A leader-following cooperative guidance strategy is presented to render the leader and the followers reach the tar...The problem of guidance law is investigated for multiple interceptors to attack a target cooperatively.A leader-following cooperative guidance strategy is presented to render the leader and the followers reach the target at specified impact time.The guidance law of leader is given to meet the demand of specified impact time.The arrival time is synchronized by enforcing the ranges-to-go of followers keep consensus with that of leader.The convergence time bound is estimated without dependence on the initial states,since the proposed leader-following cooperative guidance law is fixed-time convergent.The simulation is developed to validate the availability of proposed cooperative guidance law.展开更多
This paper investigates the spatial-temporal cooperative guidance problem for multiple flight vehicles without relying on time-to-go information.First,a two-stage cooperative guidance strategy,namely the cooperative g...This paper investigates the spatial-temporal cooperative guidance problem for multiple flight vehicles without relying on time-to-go information.First,a two-stage cooperative guidance strategy,namely the cooperative guidance and the Proportional Navigation Guidance(PNG)stage strategy,is developed to realize the spatial-temporal constraints in two dimensions.At the former stage,two controllers are designed and superimposed to satisfy both impact time consensus and impact angle constraints.Once the convergent conditions are satisfied,the flight vehicles will switch to the PNG stage to ensure zero miss distance.To further extend the results to three dimensions,a planar pursuit guidance stage is additionally imposed at the beginning of guidance.Due to the inde-pendence of time-to-go estimation,the proposed guidance strategy possesses great performance in satisfying complex spatial-temporal constraints even under flight speed variation.Finally,several numerical simulations are implemented to verify the effectiveness and advantages of the proposed results under different scenarios.展开更多
Considering the problem that the optimal error dynamics can only converge at the terminal time,an impact angle/time constraint missile guidance law with finite-time convergence is designed in this paper,which is based...Considering the problem that the optimal error dynamics can only converge at the terminal time,an impact angle/time constraint missile guidance law with finite-time convergence is designed in this paper,which is based on the pure proportional navigation(PPN)guidance law and the fast terminal error dynamics(FTED)approach.The missile guidance model and FTED equation are given first,and the dynamic equation of impact angle/time error based on PPN is also derived.Then,the guidance law is designed based on FTED,and the guidance error can converge to 0 in a finite time.Furthermore,considering the field of view constraint,the guidance law is improved by using the saturation function mapping method.Finally,a numerical simulation example is given to verify the effectiveness of the guidance law,which shows that the guidance law proposed in this paper can make the missile quickly adjust to the desired states in advance,and effectively relieve the overload saturation pressure of the actuator.展开更多
To solve the finite-time error-tracking problem in mis-sile guidance,this paper presents a unified design approach through error dynamics and free-time convergence theory.The proposed approach is initiated by establis...To solve the finite-time error-tracking problem in mis-sile guidance,this paper presents a unified design approach through error dynamics and free-time convergence theory.The proposed approach is initiated by establishing a desired model for free-time convergent error dynamics,characterized by its independence from initial conditions and guidance parameters,and adjustable convergence time.This foundation facilitates the derivation of specific guidance laws that integrate constraints such as leading angle,impact angle,and impact time.The theoretical framework of this study elucidates the nuances and synergies between the proposed guidance laws and existing methodologies.Empirical evaluations through simulation comparisons underscore the enhanced accuracy and adaptability of the proposed laws.展开更多
Based on the factors impact strength model(FISM), we studied on calculation formulas of influence strength and key elements of FISM, and analyzed the turnover time of railway freight transportation of China. The resul...Based on the factors impact strength model(FISM), we studied on calculation formulas of influence strength and key elements of FISM, and analyzed the turnover time of railway freight transportation of China. The results show that wagon transfer time is the most critical factor among the three subjective factors of wagons turnover time. The FISM based analysis of wagon transfer time show that the wagon turnover time is significantly correlated with transit time with resorting. Among the seven factors of detention time of transit time with resorting, the time of waiting to departing, converging, and waiting to break-up are key factors, while the time of make-up, break-up, arrival and departure are general factors. We carried out one empirical research based on the data of Baoji East Railway Station in 2015. The results of empirical research and FISM are consistent completely.展开更多
Sliding mode guidance laws based on a conventional terminal sliding mode guarantees only finite-time convergence, which verifies that the settling time is required to be estimated by selecting appropriate initial laun...Sliding mode guidance laws based on a conventional terminal sliding mode guarantees only finite-time convergence, which verifies that the settling time is required to be estimated by selecting appropriate initial launched conditions. However, rapid convergence to a desired impact angle within a uniform bounded finite time is important in most practical guidance applications. A uniformly finite-time/fixed-time convergent guidance law means that the convergence（settling） time is predefined independently on initial conditions, that is, a closed-loop convergence time can be estimated a priori by guidance parameters. In this paper, a novel adaptive fast fixed-time sliding mode guidance law to intercept maneuver targets at a desired impact angle from any initial heading angle,with no problems of singularity and chattering, is designed. The proposed guidance law achieves system stabilization within bounded settling time independent on initial conditions and achieves more rapid convergence than those of fixed-time stable control methods by accelerating the convergence rate when the system is close to the origin. The achieved acceleration-magnitude constraints are rigorously enforced, and the chattering-free property is guaranteed by adaptive switching gains.Extensive numerical simulations are presented to validate the efficiency and superiority of the proposed guidance law for different initial engagement geometries and impact angles.展开更多
The impact angle control over guidance(IACG) law against stationary targets is proposed by using feedback linearization control(FLC) and finite time control(FTC). First, this paper transforms the kinematics equation o...The impact angle control over guidance(IACG) law against stationary targets is proposed by using feedback linearization control(FLC) and finite time control(FTC). First, this paper transforms the kinematics equation of guidance systems into the feedbackable linearization model, in which the guidance law is obtained without considering the impact angle via FLC. For the purpose of the line of sight(LOS) angle and its rate converging to the desired values, the second-order LOS angle is considered as a double-integral system. Then, this paper utilizes FTC to design a controller which can guarantee the states of the double-integral system converging to the desired values. Numerical simulation illustrates the performance of the IACG, in contrast to the existing guidance law.展开更多
In this editorial,we comment on the article by Lei et al,with a specific focus on the timing of the initiation of the antifibrotic agent pirfenidone(PFD)in the management of idiopathic pulmonary fibrosis(IPF)and its i...In this editorial,we comment on the article by Lei et al,with a specific focus on the timing of the initiation of the antifibrotic agent pirfenidone(PFD)in the management of idiopathic pulmonary fibrosis(IPF)and its impact on lung function of IPF patients.PFD is an antifibrotic agent that is widely used in the management of IPF in both early and advanced stages.It inhibits various pathways and has antifibrotic,anti-inflammatory,and antioxidant properties.Despite dosage lowering,PFD slowed IPF progression and maintained functional capacity.The 6-min walk distance test indicated that patients tolerated adverse events well,and PFD significantly reduced the incidence of progression episodes and death.Even when a single disease-progression event occurred,continuing PFD treatment had benefits.展开更多
文摘To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D leader-following cooperative interception guidance law.First,in the LOS direction of the leader,an impact time-controlled guidance law is derived based on the fixed-time stability theory,which enables the leader to complete the interception task at a prespecified impact time.Next,in the LOS direction of the followers,by introducing a time consensus tracking error function,a fixed-time consensus tracking guidance law is investigated to guarantee the consensus tracking convergence of the time-to-go.Then,in the direction normal to the LOS,by combining the designed global integral sliding mode surface and the second-order Sliding Mode Control(SMC)theory,an innovative 3D LOS-angle-constrained interception guidance law is developed,which eliminates the reaching phase in the traditional sliding mode guidance laws and effectively saves energy consumption.Moreover,it effectively suppresses the chattering phenomenon while avoiding the singularity issue,and compensates for unknown interference caused by target maneuvering online,making it convenient for practical engineering applications.Finally,theoretical proof analysis and multiple sets of numerical simulation results verify the effectiveness,superiority,and robustness of the investigated guidance law.
基金supported by the National Natural Science Foundation of China(62003021,62373304)Industry-University-Research Innovation Fund for Chinese Universities(2021ZYA02009)+2 种基金Shaanxi Qinchuangyuan High-level Innovation and Entrepreneurship Talent Project(OCYRCXM-2022-136)Shaanxi Association for Science and Technology Youth Talent Support Program(XXJS202218)the Fundamental Research Funds for the Central Universities(D5000210830).
文摘In consideration of the field-of-view(FOV)angle con-straint,this study focuses on the guidance problem with impact time control.A deep reinforcement learning guidance method is given for the missile to obtain the desired impact time and meet the demand of FOV angle constraint.On basis of the framework of the proportional navigation guidance,an auxiliary control term is supplemented by the distributed deep deterministic policy gradient algorithm,in which the reward functions are developed to decrease the time-to-go error and improve the terminal guid-ance accuracy.The numerical simulation demonstrates that the missile governed by the presented deep reinforcement learning guidance law can hit the target successfully at appointed arrival time.
基金supported by the National Natural Science Foundation of China (Nos. 11402020 and 51407011)
文摘This study presents a novel impact time and angle constrained guidance law for homing missiles. The guidance law is first developed with the prior-assumption of a stationary target, which is followed by the practical extension to a maneuvering target scenario. To derive the closed-form guidance law, the trajectory reshaping technique is utilized and it results in defining a specific polynomial function with two unknown coefficients. These coefficients are determined to satisfy the impact time and angle constraints as well as the zero miss distance. Furthermore, the proposed guidance law has three additional guidance gains as design parameters which make it possible to adjust the guided trajectory according to the operational conditions and missile's capability. Numerical simulations are presented to validate the effectiveness of the proposed guidance law. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.
文摘A feasible guidance scheme with impact time constraint is proposed for attacking a stationary target by missiles with time-varying velocity.The main idea is to replace the constant velocity with the future mean velocity;therefore, the existing time-to-go estimation algorithm of the proportional navigation guidance law can be improved to adapt to varying conditions.In order to obtain the prediction of the velocity profile, the velocity differential equation to the downrange is derived, which can be numerically integrated between the current downrange and the target position by the on-board computer.Then, a third-order polynomial is introduced to fit the velocity profile in order to calculate the future mean velocity.At the beginning of each guidance loop, the future mean velocity is predicted and the time-to-go information is updated, based on which a novel biased proportional navigation guidance law is established to achieve the impact time constraint.Finally,numerical simulation results verified the effectiveness of the time-to-go estimation algorithm and the proposed law.
文摘This paper proposes a new three-dimensional optimal guidance law for impact time control with seeker’s Field-of-View(FOV) constraint to intercept a stationary target. The proposed guidance law is devised in conjunction with the concept of biased Proportional Navigation Guidance(PNG). The guidance law developed leverages a nonlinear function to ensure the boundedness of velocity lead angle to cater to the seeker’s FOV limit. It is proven that the impact time error is nullified in a finite-time under the proposed method. Additionally, the optimality of the biased command is theoretically analyzed. Numerical simulations confirm the superiority of the proposed method and validate the analytic findings.
基金supported by the National Natural Science Foundation of China(5137917651679201)
文摘This paper analyses the issue of impact time control of super-cavitation weapons impact fixed targets which mainly refer to the ships or submarines who lost power, but still have combat capability. Control over impact time constraints of guidance law(ITCG) is derived by using sliding mode control(SMC) and Lyapunov stability theorem. The expected impact time is realized by using the notion of attack process and estimated time-to-go to design sliding mode surface(SMS). ITCG contains equivalent and discontinuous guidance laws, once state variables arrive at SMS,the equivalent guidance law keeps the state variables on SMS,then the discontinuous guidance law enforces state variables to move and reach SMS. The singularity problem of ITCG is also analyzed. Theoretical analysis and numerical simulation results are given to test the effectiveness of ITCG designed in this paper.
文摘An impact-time-control guidance law is required for the simultaneous attack of suicide attack unmanned aerial vehicles.Based on the nonlinear model,a two-phase guidance strategy is proposed.The impact time is derived in a simple analytical form of initial states and switching states,and it can be controlled by switching at an appropriate range.Firstly,a two-phase guidance law is designed to make the magnitude of the heading error decrease monotonically from its initial value to zero.And then,the feasible interval of the switching ranges and of the impact times under the acceleration constraint are given analytically in sequence.Furthermore,a general form of twophase guidance law is proposed,which allows the magnitude of the heading error to increase in the first phase,to improve the applicability of the methodology.Having the same structure as proportional navigation guidance with a time-varying gain,the proposed algorithms are simple and easy to implement.The corresponding feedback form is presented for realistic implementation.When a predefined impact time is taken within its permissible set,the constraints on the acceleration and fieldof-view will not be violated during the interception.Finally,simulations validate the effectiveness of the methodology in impact time control and salvo attack.
基金supported by National Natural Science Foundation of China(No.61273058)
文摘A novel closed-form guidance law with impact time and impact angle constraints is pro- posed for salvo attack of anti-ship missiles, which employs missile＇s normal acceleration （not jerk） as the control command directly. Firstly, the impact time control problem is formulated as tracking the designated time-to-go （the difference between the designated impact time and the current flight time） for the actual time-to-go of missile, and the impact angle control problem is formulated as tracking the designated heading angle for the actual heading angle of missile. Secondly, a biased proportional navigation guidance （BPNG） law with designated heading angle constraint is constructed, and the actual time-to-go estimation for this BPNG is derived analytically by solving the system differential equations. Thirdly, by adding a feedback control to this constructed BPNG to eliminate the time-to-go errorthe difference between the standard time-to-go and the actual time-to-go, a guidance law with adjustable coefficients to control the impact time and impact angle simultaneously is developed. Finally, simulation results demonstrate the performance and feasibility of the proposed approach.
基金supported by the Fundamental Research Fund for the Central Universities (30919011401)。
文摘To improve applicability and adaptability of the impact time control guidance(ITCG) in practical engineering, a twostage ITCG law with simple but effective structure is proposed based on the hybrid proportional navigation, namely, the pureproportional-navigation and the retro-proportional-navigation.For the case with the impact time error less than zero, the first stage of the guided trajectory is driven by the retro-proportionalnavigation and the second one is driven by the pure-proportionalnavigation. When the impact time error is greater than zero, both of the stages are generated by the pure-proportional-navigation but using different navigation gains. It is demonstrated by twoand three-dimensional numerical simulations that the proposed guidance law at least has comparable results to existing proportional-navigation-based ITCG laws and is shown to be advantageous in certain circumstances in that the proposed guidance law alleviates its dependence on the time-to-go estimation, consumes less control energy, and adapts itself to more boundary conditions and constraints. The results of this research are expected to be supplementary to the current research literature.
基金co-supported by the Beijing Key Laboratory of UAV Autonomous Control, China and the Key Project of Chinese Ministry of Education (No. 2022CX02702)
文摘Aiming at the problem of high-precision interception of air-maneuvering targets with impact time constraints,this paper proposes a novel guidance law based on a nonlinear virtual relative model in which the origin is attached to the target.In this way,the original maneuvering target is transformed into a stationary one.A polynomial function of the guidance command in the range domain with two unknown coefficients is introduced into the virtual model,one of the coefficients is determined to achieve the impact time constraint,and the other is determined to satisfy a newly defined virtual look angle constraint.For meeting the terminal constraints simultaneously,the guidance command can finally be obtained.The resulting solution is represented as a combination of proportional navigation guidance-like term which is aimed to meet the zero miss distance constraint,a bias term for impact time control by adjusting the length of the homing trajectory,and an additional term for target maneuvers.Numerous simulations demonstrate that the proposed law achieves an acceptable impact time error for various initial conditions against different types of maneuvering targets and shows more effective performance in comparison with those of other existing guidance laws.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2017YFB1400702)and the National Natural Science Foundation of China(Grant Nos.61932014,61972018 and 61803357).
文摘The problem of guidance law is investigated for multiple interceptors to attack a target cooperatively.A leader-following cooperative guidance strategy is presented to render the leader and the followers reach the target at specified impact time.The guidance law of leader is given to meet the demand of specified impact time.The arrival time is synchronized by enforcing the ranges-to-go of followers keep consensus with that of leader.The convergence time bound is estimated without dependence on the initial states,since the proposed leader-following cooperative guidance law is fixed-time convergent.The simulation is developed to validate the availability of proposed cooperative guidance law.
基金the National Science Fund for Distinguished Young Scholars of China (No.62025301)the National Natural Science Foundation of China (Nos.62273043 and 62373055)+1 种基金the China National Postdoctoral Program for Innovative Talents (No.BX20230461)the China Postdoctoral Science Foundation (No.2023M740249)。
文摘This paper investigates the spatial-temporal cooperative guidance problem for multiple flight vehicles without relying on time-to-go information.First,a two-stage cooperative guidance strategy,namely the cooperative guidance and the Proportional Navigation Guidance(PNG)stage strategy,is developed to realize the spatial-temporal constraints in two dimensions.At the former stage,two controllers are designed and superimposed to satisfy both impact time consensus and impact angle constraints.Once the convergent conditions are satisfied,the flight vehicles will switch to the PNG stage to ensure zero miss distance.To further extend the results to three dimensions,a planar pursuit guidance stage is additionally imposed at the beginning of guidance.Due to the inde-pendence of time-to-go estimation,the proposed guidance strategy possesses great performance in satisfying complex spatial-temporal constraints even under flight speed variation.Finally,several numerical simulations are implemented to verify the effectiveness and advantages of the proposed results under different scenarios.
基金the National Natural Science Foundation of China(No.12002370)。
文摘Considering the problem that the optimal error dynamics can only converge at the terminal time,an impact angle/time constraint missile guidance law with finite-time convergence is designed in this paper,which is based on the pure proportional navigation(PPN)guidance law and the fast terminal error dynamics(FTED)approach.The missile guidance model and FTED equation are given first,and the dynamic equation of impact angle/time error based on PPN is also derived.Then,the guidance law is designed based on FTED,and the guidance error can converge to 0 in a finite time.Furthermore,considering the field of view constraint,the guidance law is improved by using the saturation function mapping method.Finally,a numerical simulation example is given to verify the effectiveness of the guidance law,which shows that the guidance law proposed in this paper can make the missile quickly adjust to the desired states in advance,and effectively relieve the overload saturation pressure of the actuator.
基金supported by the National Natural Science Foundation of China(12002370).
文摘To solve the finite-time error-tracking problem in mis-sile guidance,this paper presents a unified design approach through error dynamics and free-time convergence theory.The proposed approach is initiated by establishing a desired model for free-time convergent error dynamics,characterized by its independence from initial conditions and guidance parameters,and adjustable convergence time.This foundation facilitates the derivation of specific guidance laws that integrate constraints such as leading angle,impact angle,and impact time.The theoretical framework of this study elucidates the nuances and synergies between the proposed guidance laws and existing methodologies.Empirical evaluations through simulation comparisons underscore the enhanced accuracy and adaptability of the proposed laws.
基金Funded by the Fundamental Research Funds for the Central Universities of China(No.26816WTD23)the National United Engineering Laboratory of Integrated and Intelligent Transportation of Southwest Jiaotong University,P.R.China(No.2682017ZT11)
文摘Based on the factors impact strength model(FISM), we studied on calculation formulas of influence strength and key elements of FISM, and analyzed the turnover time of railway freight transportation of China. The results show that wagon transfer time is the most critical factor among the three subjective factors of wagons turnover time. The FISM based analysis of wagon transfer time show that the wagon turnover time is significantly correlated with transit time with resorting. Among the seven factors of detention time of transit time with resorting, the time of waiting to departing, converging, and waiting to break-up are key factors, while the time of make-up, break-up, arrival and departure are general factors. We carried out one empirical research based on the data of Baoji East Railway Station in 2015. The results of empirical research and FISM are consistent completely.
基金supported in part by the National Natural Science Foundation of China (Nos.11202024,11572036)
文摘Sliding mode guidance laws based on a conventional terminal sliding mode guarantees only finite-time convergence, which verifies that the settling time is required to be estimated by selecting appropriate initial launched conditions. However, rapid convergence to a desired impact angle within a uniform bounded finite time is important in most practical guidance applications. A uniformly finite-time/fixed-time convergent guidance law means that the convergence（settling） time is predefined independently on initial conditions, that is, a closed-loop convergence time can be estimated a priori by guidance parameters. In this paper, a novel adaptive fast fixed-time sliding mode guidance law to intercept maneuver targets at a desired impact angle from any initial heading angle,with no problems of singularity and chattering, is designed. The proposed guidance law achieves system stabilization within bounded settling time independent on initial conditions and achieves more rapid convergence than those of fixed-time stable control methods by accelerating the convergence rate when the system is close to the origin. The achieved acceleration-magnitude constraints are rigorously enforced, and the chattering-free property is guaranteed by adaptive switching gains.Extensive numerical simulations are presented to validate the efficiency and superiority of the proposed guidance law for different initial engagement geometries and impact angles.
基金supported by the National Natural Science Foundation of China(51679201)
文摘The impact angle control over guidance(IACG) law against stationary targets is proposed by using feedback linearization control(FLC) and finite time control(FTC). First, this paper transforms the kinematics equation of guidance systems into the feedbackable linearization model, in which the guidance law is obtained without considering the impact angle via FLC. For the purpose of the line of sight(LOS) angle and its rate converging to the desired values, the second-order LOS angle is considered as a double-integral system. Then, this paper utilizes FTC to design a controller which can guarantee the states of the double-integral system converging to the desired values. Numerical simulation illustrates the performance of the IACG, in contrast to the existing guidance law.
文摘In this editorial,we comment on the article by Lei et al,with a specific focus on the timing of the initiation of the antifibrotic agent pirfenidone(PFD)in the management of idiopathic pulmonary fibrosis(IPF)and its impact on lung function of IPF patients.PFD is an antifibrotic agent that is widely used in the management of IPF in both early and advanced stages.It inhibits various pathways and has antifibrotic,anti-inflammatory,and antioxidant properties.Despite dosage lowering,PFD slowed IPF progression and maintained functional capacity.The 6-min walk distance test indicated that patients tolerated adverse events well,and PFD significantly reduced the incidence of progression episodes and death.Even when a single disease-progression event occurred,continuing PFD treatment had benefits.
