The purpose of this paper is to design control loop and guidance loop for the homing missile, to prove that the modified variable structure proportional navigation (VSPN) can be used in passive homing guidance system,...The purpose of this paper is to design control loop and guidance loop for the homing missile, to prove that the modified variable structure proportional navigation (VSPN) can be used in passive homing guidance system, and to compare the VSPN with the proportional navigation (PN). Angular rate and linear acceleration are fed back to improve the stability and robust of autopilot, VSPN and PN are compared in mathematics simulation of homing missile in attacking tanks and helicopters. The damp and the stability of the missile body are increased. The VSPN cuts down the overload of guidance phase dramatically, makes the ballistic trajectory straighter than PN and leads to smaller missdistance. The VSPN can be used for passive homing guidance system, and is especially suitable for attacking helicopter.展开更多
The objective is to design a variable structure proportional navigation law for the passive homingmissile so that the missile can hit the target with a minimum miss-distance and desired impact attitude anglewithin the...The objective is to design a variable structure proportional navigation law for the passive homingmissile so that the missile can hit the target with a minimum miss-distance and desired impact attitude anglewithin the required overlcad when it flies at a lower trajectory.This paper utilized the variable structure propor-tional navigation with terminal impact attitude angular constraint,and made estimation about the distance rateand distance between the missile and target,which broke the limitation of a passive homing seeker.Furthermore,the paper let the switch gain vary adaptively with time to avoid any larger initial overload.The mathematicalsimulation was completed by some studied passive homing missile's dynamic model,and the simulation resultsshowed that the navigation law of the passive homing missile can make the missile get the required miss-distance and desired impact attitude angle against tanks at lower trajectories and within the maximum overload;also this guidance law is much robust to the estimation eror of distance and distance rate.展开更多
The variation design of complex products has such features as multivariate association,weak theory coupling and implicit knowledge iteration.However,present CAD soft wares are still restricted to making decisions only...The variation design of complex products has such features as multivariate association,weak theory coupling and implicit knowledge iteration.However,present CAD soft wares are still restricted to making decisions only according to current design status in dynamic navigation which leads to the huge drain of the knowledge hidden in design process.In this paper,a method of acquisition and active navigation of knowledge particles throughout product variation design process is put forward.The multi-objective decision information model of the variation design is established via the definition of condition attribute set and decision attribute set in finite universe.The addition and retrieval of the variation semantics is achieved through bidirectional association between the transplantable structures and variation design semantics.The mapping relationships between the topology lapping geometry elements set and constraint relations set family is built by means of geometry feature analysis.The acquisition of knowledge particles is implemented by attribute reduction based on rough set theory to make multi-objective decision of variation design.The topology lapping status of transplantable substructures is known from DOF reduction.The active navigation of knowledge particles is realized through embedded event-condition-action(ECA)rules.The independent prototype system taking Alan,Charles,Ian's system(ACIS)as kernel has been developed to verify the proposed method by applying variation design of complex mechanical products.The test results demonstrate that the navigation decision basis can be successfully extended from static isolated design status to dynamic continuous design process so that it more flexibly adapts to the different designers and various variation design steps.It is of profound significance for enhancing system intelligence as well as improving design quality and efficiency.展开更多
A flight control system is designed for a reusable launch vehicle with aerodynamic control surfaces and reaction control system based on a variable-structure control and neural network theory.The control problems of c...A flight control system is designed for a reusable launch vehicle with aerodynamic control surfaces and reaction control system based on a variable-structure control and neural network theory.The control problems of coupling among the channels and the uncertainty of model parameters are solved by using the method.High precise and robust tracking of required attitude angles can be achieved in complicated air space.A mathematical model of reusable launch vehicle is presented first,and then a controller of flight system is presented.Base on the mathematical model,the controller is divided into two parts:variable-structure controller and neural network module which is used to modify the parameters of controller.This control system decouples the lateraldirectional tunnels well with a neural network sliding mode controller and provides a robust and de-coupled tracking for mission angle profiles.After this a control allocation algorithm is employed to allocate the torque moments to aerodynamic control surfaces and thrusters.The final simulation shows that the control system has a good accurate,robust and de-coupled tracking performance.The stable state error is less than 1°,and the overshoot is less than 5%.展开更多
Purpose： This study introduces an algorithm to construct tag trees that can be used as a userfriendly navigation tool for knowledge sharing and retrieval by solving two issues of previous studies, i.e. semantic drift...Purpose： This study introduces an algorithm to construct tag trees that can be used as a userfriendly navigation tool for knowledge sharing and retrieval by solving two issues of previous studies, i.e. semantic drift and structural skew.Design/methodology/approach： Inspired by the generality based methods, this study builds tag trees from a co-occurrence tag network and uses the h-degree as a node generality metric. The proposed algorithm is characterized by the following four features：（1） the ancestors should be more representative than the descendants,（2） the semantic meaning along the ancestor-descendant paths needs to be coherent,（3） the children of one parent are collectively exhaustive and mutually exclusive in describing their parent, and（4） tags are roughly evenly distributed to their upper-level parents to avoid structural skew. Findings： The proposed algorithm has been compared with a well-established solution Heymann Tag Tree（HTT）. The experimental results using a social tag dataset showed that the proposed algorithm with its default condition outperformed HTT in precision based on Open Directory Project（ODP） classification. It has been verified that h-degree can be applied as a better node generality metric compared with degree centrality.Research limitations： A thorough investigation into the evaluation methodology is needed, including user studies and a set of metrics for evaluating semantic coherence and navigation performance.Practical implications： The algorithm will benefit the use of digital resources by generating a flexible domain knowledge structure that is easy to navigate. It could be used to manage multiple resource collections even without social annotations since tags can be keywords created by authors or experts, as well as automatically extracted from text.Originality/value： Few previous studies paid attention to the issue of whether the tagging systems are easy to navigate for users. The contributions of this study are twofold：（1） an algorithm was developed to construct tag trees with consideration given to both semanticcoherence and structural balance and（2） the effectiveness of a node generality metric, h-degree, was investigated in a tag co-occurrence network.展开更多
The aerospace industry is a very unforgiving field, where even the smallest error could have catastrophic consequences.To reduce the risk of disaster, multiple systems are put into place to provide accurate informatio...The aerospace industry is a very unforgiving field, where even the smallest error could have catastrophic consequences.To reduce the risk of disaster, multiple systems are put into place to provide accurate information for informed decisionmaking. The field of optics has played a pivotal role in advancing space exploration and technology. From enabling preciseobservations of distant celestial objects to facilitating communication across vast interstellar distances, optics hasbecome an indispensable tool in space science and supported by significant advances in the last few years, new and improvedapplications continue to arise. This review aims to explore the diverse applications of optical systems and technologiesin the aerospace industry, highlighting recent developments regarding navigation, communications, process andstructural health monitoring, as well as the monitorization of astronauts' health.展开更多
文摘The purpose of this paper is to design control loop and guidance loop for the homing missile, to prove that the modified variable structure proportional navigation (VSPN) can be used in passive homing guidance system, and to compare the VSPN with the proportional navigation (PN). Angular rate and linear acceleration are fed back to improve the stability and robust of autopilot, VSPN and PN are compared in mathematics simulation of homing missile in attacking tanks and helicopters. The damp and the stability of the missile body are increased. The VSPN cuts down the overload of guidance phase dramatically, makes the ballistic trajectory straighter than PN and leads to smaller missdistance. The VSPN can be used for passive homing guidance system, and is especially suitable for attacking helicopter.
文摘The objective is to design a variable structure proportional navigation law for the passive homingmissile so that the missile can hit the target with a minimum miss-distance and desired impact attitude anglewithin the required overlcad when it flies at a lower trajectory.This paper utilized the variable structure propor-tional navigation with terminal impact attitude angular constraint,and made estimation about the distance rateand distance between the missile and target,which broke the limitation of a passive homing seeker.Furthermore,the paper let the switch gain vary adaptively with time to avoid any larger initial overload.The mathematicalsimulation was completed by some studied passive homing missile's dynamic model,and the simulation resultsshowed that the navigation law of the passive homing missile can make the missile get the required miss-distance and desired impact attitude angle against tanks at lower trajectories and within the maximum overload;also this guidance law is much robust to the estimation eror of distance and distance rate.
基金supported by National Natural Science Foundation of China(61125306,91016004)Foundation of Ministry of Education of China(20110092110020,20120092110026)the Post-Doctoral Research Funds(1108000137,3208004602)
基金supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2006AA04Z114)National Natural Science Foundation of China(Grant No.50775201)
文摘The variation design of complex products has such features as multivariate association,weak theory coupling and implicit knowledge iteration.However,present CAD soft wares are still restricted to making decisions only according to current design status in dynamic navigation which leads to the huge drain of the knowledge hidden in design process.In this paper,a method of acquisition and active navigation of knowledge particles throughout product variation design process is put forward.The multi-objective decision information model of the variation design is established via the definition of condition attribute set and decision attribute set in finite universe.The addition and retrieval of the variation semantics is achieved through bidirectional association between the transplantable structures and variation design semantics.The mapping relationships between the topology lapping geometry elements set and constraint relations set family is built by means of geometry feature analysis.The acquisition of knowledge particles is implemented by attribute reduction based on rough set theory to make multi-objective decision of variation design.The topology lapping status of transplantable substructures is known from DOF reduction.The active navigation of knowledge particles is realized through embedded event-condition-action(ECA)rules.The independent prototype system taking Alan,Charles,Ian's system(ACIS)as kernel has been developed to verify the proposed method by applying variation design of complex mechanical products.The test results demonstrate that the navigation decision basis can be successfully extended from static isolated design status to dynamic continuous design process so that it more flexibly adapts to the different designers and various variation design steps.It is of profound significance for enhancing system intelligence as well as improving design quality and efficiency.
文摘A flight control system is designed for a reusable launch vehicle with aerodynamic control surfaces and reaction control system based on a variable-structure control and neural network theory.The control problems of coupling among the channels and the uncertainty of model parameters are solved by using the method.High precise and robust tracking of required attitude angles can be achieved in complicated air space.A mathematical model of reusable launch vehicle is presented first,and then a controller of flight system is presented.Base on the mathematical model,the controller is divided into two parts:variable-structure controller and neural network module which is used to modify the parameters of controller.This control system decouples the lateraldirectional tunnels well with a neural network sliding mode controller and provides a robust and de-coupled tracking for mission angle profiles.After this a control allocation algorithm is employed to allocate the torque moments to aerodynamic control surfaces and thrusters.The final simulation shows that the control system has a good accurate,robust and de-coupled tracking performance.The stable state error is less than 1°,and the overshoot is less than 5%.
基金funded by the National Natural Science Foundation of China(Grand No.:70903008)supported by COGS Lab in School of Government,Beijing Normal University
文摘Purpose： This study introduces an algorithm to construct tag trees that can be used as a userfriendly navigation tool for knowledge sharing and retrieval by solving two issues of previous studies, i.e. semantic drift and structural skew.Design/methodology/approach： Inspired by the generality based methods, this study builds tag trees from a co-occurrence tag network and uses the h-degree as a node generality metric. The proposed algorithm is characterized by the following four features：（1） the ancestors should be more representative than the descendants,（2） the semantic meaning along the ancestor-descendant paths needs to be coherent,（3） the children of one parent are collectively exhaustive and mutually exclusive in describing their parent, and（4） tags are roughly evenly distributed to their upper-level parents to avoid structural skew. Findings： The proposed algorithm has been compared with a well-established solution Heymann Tag Tree（HTT）. The experimental results using a social tag dataset showed that the proposed algorithm with its default condition outperformed HTT in precision based on Open Directory Project（ODP） classification. It has been verified that h-degree can be applied as a better node generality metric compared with degree centrality.Research limitations： A thorough investigation into the evaluation methodology is needed, including user studies and a set of metrics for evaluating semantic coherence and navigation performance.Practical implications： The algorithm will benefit the use of digital resources by generating a flexible domain knowledge structure that is easy to navigate. It could be used to manage multiple resource collections even without social annotations since tags can be keywords created by authors or experts, as well as automatically extracted from text.Originality/value： Few previous studies paid attention to the issue of whether the tagging systems are easy to navigate for users. The contributions of this study are twofold：（1） an algorithm was developed to construct tag trees with consideration given to both semanticcoherence and structural balance and（2） the effectiveness of a node generality metric, h-degree, was investigated in a tag co-occurrence network.
基金funded by National Funds through the Portuguese Science and Technology Foundation(FCT I.P.)under the scope of the project CICECO(LA/P/0006/2020,UIDB/50011/2020,UIDP/50011/2020)The research was co-funded by the financial support of the European Union under the REFRESH–Research Excellence For Region Sustainability and High-tech Industries project number CZ.10.03.01/00/22_003/0000048 via the Operational Programme Just Transitionsupported by the Ministry of Education,Youth,and Sports of the Czech Republic conducted by the VSB-Technical University of Ostrava,under grants no.SP2025/039 and SP2025/021.
文摘The aerospace industry is a very unforgiving field, where even the smallest error could have catastrophic consequences.To reduce the risk of disaster, multiple systems are put into place to provide accurate information for informed decisionmaking. The field of optics has played a pivotal role in advancing space exploration and technology. From enabling preciseobservations of distant celestial objects to facilitating communication across vast interstellar distances, optics hasbecome an indispensable tool in space science and supported by significant advances in the last few years, new and improvedapplications continue to arise. This review aims to explore the diverse applications of optical systems and technologiesin the aerospace industry, highlighting recent developments regarding navigation, communications, process andstructural health monitoring, as well as the monitorization of astronauts' health.
