Following the growing research interests in complex networks, in recent years many researchers treated static structures of software as complex networks and revealed that most of these networks demonstrate small-world...Following the growing research interests in complex networks, in recent years many researchers treated static structures of software as complex networks and revealed that most of these networks demonstrate small-world effect and follow scale-free degree distribution. Different from the perspectives adopted in these works, our previous work proposed software mirror graph to model the dynamic execution processes of software and revealed software mirror graph may also be small world and scale-free. To explain how the software mirror graph evolves into a small world and scale free structure, in this paper we further proposed a mathematical model based on the mechanisms of growth, preferential attachment, and walking. This model captures some of the features of the software mirror graph, and the simulation results show that it can generate a network having similar properties to the software mirror graph. The implications are also discussed in this paper.展开更多
Designing a controller for the docking maneuver in Probe-Drogue Refueling(PDR) is an important but challenging task, due to the complex system model and the high precision requirement.In order to overcome the disadvan...Designing a controller for the docking maneuver in Probe-Drogue Refueling(PDR) is an important but challenging task, due to the complex system model and the high precision requirement.In order to overcome the disadvantage of only feedback control, a feedforward control scheme known as Iterative Learning Control(ILC) is adopted in this paper.First, Additive State Decomposition(ASD) is used to address the tight coupling of input saturation, nonlinearity and the property of Non Minimum Phase(NMP) by separating these features into two subsystems(a primary system and a secondary system).After system decomposition, an adjoint-type ILC is applied to the Linear Time-Invariant(LTI) primary system with NMP to achieve entire output trajectory tracking, whereas state feedback is used to stabilize the secondary system with input saturation.The two controllers designed for the two subsystems can be combined to achieve the original control goal of the PDR system.Furthermore, to compensate for the receiverindependent uncertainties, a correction action is proposed by using the terminal docking error,which can lead to a smaller docking error at the docking moment.Simulation tests have been carried out to demonstrate the performance of the proposed control method, which has some advantages over the traditional derivative-type ILC and adjoint-type ILC in the docking control of PDR.展开更多
The repetitive control(RC) or repetitive controller problem for nonminimum phase nonlinear systems is both challenging and practical. In this paper, we consider an RC problem for the translational oscillator with a ro...The repetitive control(RC) or repetitive controller problem for nonminimum phase nonlinear systems is both challenging and practical. In this paper, we consider an RC problem for the translational oscillator with a rotational actuator(TORA), which is a nonminimum phase nonlinear system. The major difficulty is to handle both a nonminimum phase RC problem and a nonlinear problem simultaneously. For such purpose, a new RC design, namely the additive-state-decomposition-based approach, is proposed,by which the nonminimum phase RC problem and the nonlinear problem are separated. This makes RC for the TORA benchmark tractable. To demonstrate the effectiveness of the proposed approach, a numerical simulation is given.展开更多
In order to handle undesirable failures of a multicopter,which occurs in either the pre-flight process or the in-flight process,a failsafe mechanism design method based on supervisory control theory(SCT)is proposed fo...In order to handle undesirable failures of a multicopter,which occurs in either the pre-flight process or the in-flight process,a failsafe mechanism design method based on supervisory control theory(SCT)is proposed for the semi-autonomous control mode.The failsafe mechanism is a control logic that guides what subsequent actions the multicopter should take,by taking account of real-time information from guidance,attitude control,diagnosis and other low-level subsystems.In order to design a failsafe mechanism for the multicopters,safety issues of the multicopters are introduced.Then,user requirements including functional requirements and safety requirements are textually described,where functional requirements guide the modelling of a general multicopter plant,and safety requirements cover the failsafe measures dealing with the presented safety issues.Based on these requirements,several multicopter modes and events are defined.On this basis,the multicopter plant and control specifications are modelled by automata.Then,a supervisor is synthesized by using SCT.In addition,the authors present three examples to demonstrate the potential conflicting phenomena due to the inappropriate design of control specifications.Finally,based on the obtained supervisor,an implementation method suitable for multicopters is presented,in which the supervisor is transformed into decision-making codes.展开更多
In aerospace engineering and industry, control tasks are often of a periodic nature,while repetitive control is especially suitable for tracking and rejection of periodic exogenous signals.Because of limited research ...In aerospace engineering and industry, control tasks are often of a periodic nature,while repetitive control is especially suitable for tracking and rejection of periodic exogenous signals.Because of limited research effort on nonlinear systems, we give a survey of repetitive control for nonlinear systems in this paper.First,a brief introduction of repetitive control is presented.Then,after giving a brief overview of repetitive control for linear systems,this paper summarizes design methods and existing problems of repetitive control for nonlinear systems in detail.Lastly,relationships between repetitive control and other control schemes are analyzed to recognize repetitive control from different aspects more insightfully.展开更多
文摘Following the growing research interests in complex networks, in recent years many researchers treated static structures of software as complex networks and revealed that most of these networks demonstrate small-world effect and follow scale-free degree distribution. Different from the perspectives adopted in these works, our previous work proposed software mirror graph to model the dynamic execution processes of software and revealed software mirror graph may also be small world and scale-free. To explain how the software mirror graph evolves into a small world and scale free structure, in this paper we further proposed a mathematical model based on the mechanisms of growth, preferential attachment, and walking. This model captures some of the features of the software mirror graph, and the simulation results show that it can generate a network having similar properties to the software mirror graph. The implications are also discussed in this paper.
基金supported by the National Natural Science Foundation of China(No.61473012)。
文摘Designing a controller for the docking maneuver in Probe-Drogue Refueling(PDR) is an important but challenging task, due to the complex system model and the high precision requirement.In order to overcome the disadvantage of only feedback control, a feedforward control scheme known as Iterative Learning Control(ILC) is adopted in this paper.First, Additive State Decomposition(ASD) is used to address the tight coupling of input saturation, nonlinearity and the property of Non Minimum Phase(NMP) by separating these features into two subsystems(a primary system and a secondary system).After system decomposition, an adjoint-type ILC is applied to the Linear Time-Invariant(LTI) primary system with NMP to achieve entire output trajectory tracking, whereas state feedback is used to stabilize the secondary system with input saturation.The two controllers designed for the two subsystems can be combined to achieve the original control goal of the PDR system.Furthermore, to compensate for the receiverindependent uncertainties, a correction action is proposed by using the terminal docking error,which can lead to a smaller docking error at the docking moment.Simulation tests have been carried out to demonstrate the performance of the proposed control method, which has some advantages over the traditional derivative-type ILC and adjoint-type ILC in the docking control of PDR.
基金supported by National Natural Science Foundation of China(No.61473012)
文摘The repetitive control(RC) or repetitive controller problem for nonminimum phase nonlinear systems is both challenging and practical. In this paper, we consider an RC problem for the translational oscillator with a rotational actuator(TORA), which is a nonminimum phase nonlinear system. The major difficulty is to handle both a nonminimum phase RC problem and a nonlinear problem simultaneously. For such purpose, a new RC design, namely the additive-state-decomposition-based approach, is proposed,by which the nonminimum phase RC problem and the nonlinear problem are separated. This makes RC for the TORA benchmark tractable. To demonstrate the effectiveness of the proposed approach, a numerical simulation is given.
基金This work was partially supported by the National Natural Science Foundation of China(61973015,61903008)the Beijing Natural Science Foundation(4194074)the Natural Sciences and Engineering Research Council(NSERC)of Canada(Grant#DG_480599).
文摘In order to handle undesirable failures of a multicopter,which occurs in either the pre-flight process or the in-flight process,a failsafe mechanism design method based on supervisory control theory(SCT)is proposed for the semi-autonomous control mode.The failsafe mechanism is a control logic that guides what subsequent actions the multicopter should take,by taking account of real-time information from guidance,attitude control,diagnosis and other low-level subsystems.In order to design a failsafe mechanism for the multicopters,safety issues of the multicopters are introduced.Then,user requirements including functional requirements and safety requirements are textually described,where functional requirements guide the modelling of a general multicopter plant,and safety requirements cover the failsafe measures dealing with the presented safety issues.Based on these requirements,several multicopter modes and events are defined.On this basis,the multicopter plant and control specifications are modelled by automata.Then,a supervisor is synthesized by using SCT.In addition,the authors present three examples to demonstrate the potential conflicting phenomena due to the inappropriate design of control specifications.Finally,based on the obtained supervisor,an implementation method suitable for multicopters is presented,in which the supervisor is transformed into decision-making codes.
文摘In aerospace engineering and industry, control tasks are often of a periodic nature,while repetitive control is especially suitable for tracking and rejection of periodic exogenous signals.Because of limited research effort on nonlinear systems, we give a survey of repetitive control for nonlinear systems in this paper.First,a brief introduction of repetitive control is presented.Then,after giving a brief overview of repetitive control for linear systems,this paper summarizes design methods and existing problems of repetitive control for nonlinear systems in detail.Lastly,relationships between repetitive control and other control schemes are analyzed to recognize repetitive control from different aspects more insightfully.
