Global Navigation Satellite System(GNSS)-based continuous and accurate train positioning is one of the key technologies for advanced train operations such as train virtual coupling.However,GNSS-based train positioning...Global Navigation Satellite System(GNSS)-based continuous and accurate train positioning is one of the key technologies for advanced train operations such as train virtual coupling.However,GNSS-based train positioning faces significant challenges in real-world scenarios due to environmental complexities and signal interferences.Considering this issue,this paper presents an approach for modeling and performance analysis of GNSS-based train positioning systems using Colored Petri Nets(CPNs).By systematically modeling the GNSS signal reception and processing process,the performance of the positioning system under various environment scenarios is evaluated.The system model integrates three types of interference signals(i.e.,Amplitude Modulation(AM)signals,Frequency Modulation(FM)signals,and pulse signals)while incorporating environmental factors such as terrain obstructions and tunnel shielding.Additionally,the Extended Kalman Filter(EKF)algorithm is employed to process GNSS observation data,providing accurate train position estimations.The simulation results demonstrate that signal interferences and complex environmental conditions significantly affect the GNSS-based positioning accuracy.This study offers a comprehensive framework for evaluating the performance of GNSS-based train positioning systems in different scenarios,highlighting critical factors that influence positioning accuracy and stability.展开更多
A novel siphon-based divide-and-conquer(SbDaC)policy is presented in this paper for the synthesis of Petri net(PN)based liveness-enforcing supervisors(LES)for flexible manufacturing systems(FMS)prone to deadlocks or l...A novel siphon-based divide-and-conquer(SbDaC)policy is presented in this paper for the synthesis of Petri net(PN)based liveness-enforcing supervisors(LES)for flexible manufacturing systems(FMS)prone to deadlocks or livelocks.The proposed method takes an uncontrolled and bounded PN model(UPNM)of the FMS.Firstly,the reduced PNM(RPNM)is obtained from the UPNM by using PN reduction rules to reduce the computation burden.Then,the set of strict minimal siphons(SMSs)of the RPNM is computed.Next,the complementary set of SMSs is computed from the set of SMSs.By the union of these two sets,the superset of SMSs is computed.Finally,the set of subnets of the RPNM is obtained by applying the PN reduction rules to the superset of SMSs.All these subnets suffer from deadlocks.These subnets are then ordered from the smallest one to the largest one based on a criterion.To enforce liveness on these subnets,a set of control places(CPs)is computed starting from the smallest subnet to the largest one.Once all subnets are live,this process provides the LES,consisting of a set of CPs to be used for the UPNM.The live controlled PN model(CPNM)is constructed by merging the LES with the UPNM.The SbDaC policy is applicable to all classes of PNs related to FMS prone to deadlocks or livelocks.Several FMS examples are considered from the literature to highlight the applicability of the SbDaC policy.In particular,three examples are utilized to emphasize the importance,applicability and effectiveness of the SbDaC policy to realistic FMS with very large state spaces.展开更多
Traditional models for project management have not adequately incorporated a number of factors that are important for resource allocation. This paper proposed a unified timed Petri net model in which scheduling and pl...Traditional models for project management have not adequately incorporated a number of factors that are important for resource allocation. This paper proposed a unified timed Petri net model in which scheduling and planning were collectively carried out to take full advantages of the flexibility of the FMS. Through the lens of system theory, two types of resources were distinguished: major role and auxiliary role, and the major role was used to construct the FMS' Petri net. The method simplified the Petri net's construction and gave a clear flow chart for scheduling. Hence, the auxiliary resource allocation could be easily carried out according to the schedule, which was proposed by heuristic search algorithm. At last, the efficacy of the Petri net model for online scheduling in a resource constrained environment was discussed.展开更多
Time Petri Nets在实时系统的建模和性能分析中得到广泛应用,而冲突是Petri网及其扩展模型的重要行为,解决冲突是正确分析模型动态行为的关键.目前随机Petri网、混合Petri网和区间速率连续Petri网的冲突检测方法由于没有考虑到时间约束...Time Petri Nets在实时系统的建模和性能分析中得到广泛应用,而冲突是Petri网及其扩展模型的重要行为,解决冲突是正确分析模型动态行为的关键.目前随机Petri网、混合Petri网和区间速率连续Petri网的冲突检测方法由于没有考虑到时间约束因此无法在TPN网中使用.时间约束的引入使得Time Petri Nets模型的使能和触发语义比Petri网模型的语义复杂,冲突检测变得更加困难.为了计算冲突发生的时间和概率,首先根据时间约束,给出了变迁持续使能时延迟区间的计算方法,并证明了该方法的合理性和完备性;然后在此基础上定义并证明了Time Petri Nets模型中不冲突的检测方法;并提出了Time Petri Nets模型的冲突检测方法,给出了冲突时间区间和变迁实施概率的计算方法;最后通过实例验证说明了该方法的正确性和有效性.展开更多
Aim To present a quantitative method for structural complexity analysis and evaluation of information systems. Methods Based on Petri net modeling and analysis techniques and with the aid of mathematical tools in ge...Aim To present a quantitative method for structural complexity analysis and evaluation of information systems. Methods Based on Petri net modeling and analysis techniques and with the aid of mathematical tools in general net theory(GNT), a quantitative method for structure description and analysis of information systems was introduced. Results The structural complexity index and two related factors, i.e. element complexity factor and connection complexity factor were defined, and the relations between them and the parameters of the Petri net based model of the system were derived. Application example was presented. Conclusion The proposed method provides a theoretical basis for quantitative analysis and evaluation of the structural complexity and can be applied in the general planning and design processes of the information systems.展开更多
In order to model effectively hybrid systems,a new modeling method of extended Petri nets,which is called extended object-orient hybrid Petri net （EOHPN）,is proposed.To deal with the complexity of hybrid systems, ob...In order to model effectively hybrid systems,a new modeling method of extended Petri nets,which is called extended object-orient hybrid Petri net （EOHPN）,is proposed.To deal with the complexity of hybrid systems, object-oriented abstraction mechanisms such as encapsulation and classifications are merged into EOHPN models.To combine the continuous part and discrete part of hybrid systems and to reduce the complexity of hybrid systems,a hybrid Petri net is introduced and extended with object-oriented modeling technology.Development of object models is suggested on the basis of the defined EOHPN.Finally, an application-oriented case is presented to illustrate that how the proposed EOHPN is used to model hybrid systems.The resulting model validates that the EOHPNs can deal with the modeling complexity of hybrid systems.展开更多
基金supported by the National Key Research and Development Program of China(2023YFB3907300)the Fundamental Research Funds for the Central Universities(2024JBMC002)the National Natural Science Foundation of China(T2222015,U2268206).
文摘Global Navigation Satellite System(GNSS)-based continuous and accurate train positioning is one of the key technologies for advanced train operations such as train virtual coupling.However,GNSS-based train positioning faces significant challenges in real-world scenarios due to environmental complexities and signal interferences.Considering this issue,this paper presents an approach for modeling and performance analysis of GNSS-based train positioning systems using Colored Petri Nets(CPNs).By systematically modeling the GNSS signal reception and processing process,the performance of the positioning system under various environment scenarios is evaluated.The system model integrates three types of interference signals(i.e.,Amplitude Modulation(AM)signals,Frequency Modulation(FM)signals,and pulse signals)while incorporating environmental factors such as terrain obstructions and tunnel shielding.Additionally,the Extended Kalman Filter(EKF)algorithm is employed to process GNSS observation data,providing accurate train position estimations.The simulation results demonstrate that signal interferences and complex environmental conditions significantly affect the GNSS-based positioning accuracy.This study offers a comprehensive framework for evaluating the performance of GNSS-based train positioning systems in different scenarios,highlighting critical factors that influence positioning accuracy and stability.
基金The authors extend their appreciation to King Saud University,Saudi Arabia for funding this work through the Ongoing Research Funding Program(ORF-2025-704),King Saud University,Riyadh,Saudi Arabia.
文摘A novel siphon-based divide-and-conquer(SbDaC)policy is presented in this paper for the synthesis of Petri net(PN)based liveness-enforcing supervisors(LES)for flexible manufacturing systems(FMS)prone to deadlocks or livelocks.The proposed method takes an uncontrolled and bounded PN model(UPNM)of the FMS.Firstly,the reduced PNM(RPNM)is obtained from the UPNM by using PN reduction rules to reduce the computation burden.Then,the set of strict minimal siphons(SMSs)of the RPNM is computed.Next,the complementary set of SMSs is computed from the set of SMSs.By the union of these two sets,the superset of SMSs is computed.Finally,the set of subnets of the RPNM is obtained by applying the PN reduction rules to the superset of SMSs.All these subnets suffer from deadlocks.These subnets are then ordered from the smallest one to the largest one based on a criterion.To enforce liveness on these subnets,a set of control places(CPs)is computed starting from the smallest subnet to the largest one.Once all subnets are live,this process provides the LES,consisting of a set of CPs to be used for the UPNM.The live controlled PN model(CPNM)is constructed by merging the LES with the UPNM.The SbDaC policy is applicable to all classes of PNs related to FMS prone to deadlocks or livelocks.Several FMS examples are considered from the literature to highlight the applicability of the SbDaC policy.In particular,three examples are utilized to emphasize the importance,applicability and effectiveness of the SbDaC policy to realistic FMS with very large state spaces.
文摘Traditional models for project management have not adequately incorporated a number of factors that are important for resource allocation. This paper proposed a unified timed Petri net model in which scheduling and planning were collectively carried out to take full advantages of the flexibility of the FMS. Through the lens of system theory, two types of resources were distinguished: major role and auxiliary role, and the major role was used to construct the FMS' Petri net. The method simplified the Petri net's construction and gave a clear flow chart for scheduling. Hence, the auxiliary resource allocation could be easily carried out according to the schedule, which was proposed by heuristic search algorithm. At last, the efficacy of the Petri net model for online scheduling in a resource constrained environment was discussed.
文摘Time Petri Nets在实时系统的建模和性能分析中得到广泛应用,而冲突是Petri网及其扩展模型的重要行为,解决冲突是正确分析模型动态行为的关键.目前随机Petri网、混合Petri网和区间速率连续Petri网的冲突检测方法由于没有考虑到时间约束因此无法在TPN网中使用.时间约束的引入使得Time Petri Nets模型的使能和触发语义比Petri网模型的语义复杂,冲突检测变得更加困难.为了计算冲突发生的时间和概率,首先根据时间约束,给出了变迁持续使能时延迟区间的计算方法,并证明了该方法的合理性和完备性;然后在此基础上定义并证明了Time Petri Nets模型中不冲突的检测方法;并提出了Time Petri Nets模型的冲突检测方法,给出了冲突时间区间和变迁实施概率的计算方法;最后通过实例验证说明了该方法的正确性和有效性.
文摘Aim To present a quantitative method for structural complexity analysis and evaluation of information systems. Methods Based on Petri net modeling and analysis techniques and with the aid of mathematical tools in general net theory(GNT), a quantitative method for structure description and analysis of information systems was introduced. Results The structural complexity index and two related factors, i.e. element complexity factor and connection complexity factor were defined, and the relations between them and the parameters of the Petri net based model of the system were derived. Application example was presented. Conclusion The proposed method provides a theoretical basis for quantitative analysis and evaluation of the structural complexity and can be applied in the general planning and design processes of the information systems.
基金The National Key Laboratory Program ( No.51458060104JW0316)the National High Technology Research and De-velopment Program of China (863 Program) (No.2003AA414120).
文摘In order to model effectively hybrid systems,a new modeling method of extended Petri nets,which is called extended object-orient hybrid Petri net （EOHPN）,is proposed.To deal with the complexity of hybrid systems, object-oriented abstraction mechanisms such as encapsulation and classifications are merged into EOHPN models.To combine the continuous part and discrete part of hybrid systems and to reduce the complexity of hybrid systems,a hybrid Petri net is introduced and extended with object-oriented modeling technology.Development of object models is suggested on the basis of the defined EOHPN.Finally, an application-oriented case is presented to illustrate that how the proposed EOHPN is used to model hybrid systems.The resulting model validates that the EOHPNs can deal with the modeling complexity of hybrid systems.
