When discovering the potential of canards flying in 4-dimensional slow-fast system with a bifurcation parameter, the key notion “symmetry” plays an important role. It is of one parameter on slow vector field. Then, ...When discovering the potential of canards flying in 4-dimensional slow-fast system with a bifurcation parameter, the key notion “symmetry” plays an important role. It is of one parameter on slow vector field. Then, it should be determined to introduce parameters to all slow/fast vectors. It is, however, there might be no way to explore for another potential in this system, because the geometrical structure is quite different from the system with one parameter. Even in this system, the “symmetry” is also useful to obtain the potentials classified by R. Thom. In this paper, via the coordinates changing, the possible way to explore for the potential will be shown. As it is analyzed on “hyper finite time line”, or done by using “non-standard analysis”, it is called “Hyper Catastrophe”. In the slow-fast system which includes a very small parameter , it is difficult to do precise analysis. Thus, it is useful to get the orbits as a singular limit. When trying to do simulations, it is also faced with difficulty due to singularity. Using very small time intervals corresponding small , we shall overcome the difficulty, because the difference equation on the small time interval adopts the standard differential equation. These small intervals are defined on hyper finite number N, which is nonstandard. As and the intervals are linked to use 1/N, the simulation should be done exactly.展开更多
There exists a property “structural stability” for “4-dimensional canards” which is a singular-limit solution in a slow-fast system with a bifurcation parameter. It means that the system includes the possibility t...There exists a property “structural stability” for “4-dimensional canards” which is a singular-limit solution in a slow-fast system with a bifurcation parameter. It means that the system includes the possibility to have some critical values on the bifurcation parameter. Corresponding to these values, the pseudo-singular point, which is a singular point in the time-scaled-reduced system should be changed to another one. Then, the canards may fly to another pseudo-singular point, if possible. Can the canards fly? The structural stability gives the possibility for the canards flying. The precise reasons why happen are described in this paper.展开更多
Existing literature has shown that the control force at the nose could cause dynamic instability for controlled projectiles. To lower the adverse impact on the dual-spin projectile with fixed canards under the premise...Existing literature has shown that the control force at the nose could cause dynamic instability for controlled projectiles. To lower the adverse impact on the dual-spin projectile with fixed canards under the premise of meeting guidance system requirements, the influence of control moment provided by a motor on the flight stability is analyzed in this paper. Firstly, the effect of the rolling movement on stability is analyzed based on the stability criterion derived using the Hurwitz stability theory. Secondly, the evaluation parameters combining the features of different control periods that could assess the variation of stability features after the motor torque are obtained. These effective formulas are used to indicate that, to reduce the flight instability risks, the stabilized rolling speed of roll speed keeping period should be as small as possible; the variation trend of motor torque during the rolling speed controlling period and the roll angle of the forward body during roll angle switching period are recommended corresponding to the projectile and trajectory characteristics. Moreover,detailed numerical simulations of 155 mm dual-spin projectile are satisfactory agreement with the theoretical results.展开更多
To study the rolling control characteristics of a canard-controlled missile, a series of wind tunnel experiment is conducted. The experimental method, the structure features of wind tunnel model and the experimental r...To study the rolling control characteristics of a canard-controlled missile, a series of wind tunnel experiment is conducted. The experimental method, the structure features of wind tunnel model and the experimental results are introduced in this paper. The experimental data show that the canard is an inefficient rolling control device for canard-controlled missile with fixed tail fins; but for the free-spinning tail fin configuration, the canard can conduct rolling control of the missile, and even have higher controlling efficiency under larger canard deflection angle.展开更多
The steady flow field of a canard missile on different angles of attack and Mach numbers were studied. Based on analysis, a method was proposed to reduce the calculation for the rolling characteristics of the canard m...The steady flow field of a canard missile on different angles of attack and Mach numbers were studied. Based on analysis, a method was proposed to reduce the calculation for the rolling characteristics of the canard missile with free-spinning tails, and was tested to obtain the relations between rolling moment coefficient, Mach number, and angle of attack. All the computed rolling moment coefficients obtained from the proposed method greatly agreed with the experimental results of FD-06 wind tunnel in CAAA, which proved that the method can not only reduce the calculation cost but also keep precision in calculating the rolling characteristics of canard missiles.展开更多
The classification on the orbits of some Liénard perturbation system with several parameters, which is relation to the example in [1] or [2], is discussed. The conditions for the parameters in order that the syst...The classification on the orbits of some Liénard perturbation system with several parameters, which is relation to the example in [1] or [2], is discussed. The conditions for the parameters in order that the system has a unique limit cycle, homoclinic orbits, canards or the unique equilibrium point is globally asymptotic stable are given. The methods in our previous papers are used for the proofs.展开更多
Let us consider higher dimensional canards in a sow-fast system R<sup>2+2</sup> with a bifurcation parameter. Then, the slow manifold sometimes shows various aspects due to the bifurcation. Introducing a k...Let us consider higher dimensional canards in a sow-fast system R<sup>2+2</sup> with a bifurcation parameter. Then, the slow manifold sometimes shows various aspects due to the bifurcation. Introducing a key notion “symmetry” to the slow-fast system, it becomes clear when the pseudo singular point obtains the structural stability or not. It should be treated with a general case. Then, it will also be given about the sufficient conditions for the existence of the center manifold under being “symmetry”. The higher dimensional canards in the sow-fast system are deeply related to Hilbert’s 16th problem. Furthermore, computer simulations are done for the systems having Brownian motions. As a result, the rigidity for the system is confirmed.展开更多
The canard explosion phenomenon in a predator-prey model with Michaelis-Menten functional response is analyzed in this paper by employing the geometric singular perturbation theory. First, some turning points, such as...The canard explosion phenomenon in a predator-prey model with Michaelis-Menten functional response is analyzed in this paper by employing the geometric singular perturbation theory. First, some turning points, such as, fold point, transcritical point, pitchfork point, canard point, are identified;then Hopf bifurcation, relaxation oscillation, together with the canard transition from Hopf bifurcation to relaxation oscillation are discussed.展开更多
The fixed canards configuration of a dual-spin projectile makes it difficult to apply the traditional guidance law. In this study, a modified impact point prediction guidance strategy based on an iterative process was...The fixed canards configuration of a dual-spin projectile makes it difficult to apply the traditional guidance law. In this study, a modified impact point prediction guidance strategy based on an iterative process was developed for a class of dual-spin projectiles with fixed canards, to reduce the impact point dispersion. The guidance strategy is dependent on the modified projectile linear theory to rapidly predict the flight states and the impact point. For projectiles with control applied to the trajectory, the modified projectile linear theory method is known to achieve poor impact point prediction. To improve the prediction accuracy, improvements were made to the modified projectile linear theory by considering the products of the yaw rate and other small quantities.The guidance strategy is based on the iterative process for the continuous adjustment of the expected output of the roll angle of the course correction fuze, to minimize the direction error between the predicted impact point and target location. Studies were conducted on a model dual-spin projectile configuration to demonstrate the guidance details. The numerical simulations indicate that the proposed guidance strategy can effectively reduce the projectile impact point dispersion.展开更多
The aerodynamic layout of the Canard Rotor/Wing(CRW) aircraft in helicopter flight mode differs significantly from that of conventional helicopters. In order to study the flight dynamics characteristics of CRW aircraf...The aerodynamic layout of the Canard Rotor/Wing(CRW) aircraft in helicopter flight mode differs significantly from that of conventional helicopters. In order to study the flight dynamics characteristics of CRW aircraft in helicopter mode, first, the aerodynamic model of the main rotor system is established based on the blade element theory and wind tunnel test results. The aerodynamic forces and moments of the canard wing, horizontal tail, vertical tail and fuselage are obtained via theoretical analysis and empirical formula. The flight dynamics model of the CRW aircraft in helicopter mode is developed and validated by flight test data. Next, a method of model trimming using an optimization algorithm is proposed. The flight dynamics characteristics of the CRW are investigated by the method of linearized small perturbations via Simulink. The trim results are consistent with the conventional helicopter characteristics, and the results show that with increasing forward flight speed, the canard wing and horizontal tail can provide considerable lift,which reflects the unique characteristics of the CRW aircraft. Finally, mode analysis is implemented for the linearized CRW in helicopter mode. The results demonstrate that the stability of majority modes increases with increasing flight speed. However, one mode that diverges monotonously,and the reason is that the CRW helicopter mode has a large vertical tail compared to the conventional helicopter. The results of the dynamic analysis provide optimization guidance and reference for the overall design of the CRW aircraft in helicopter mode, and the model developed can be used for control system design.展开更多
In the nonlinear dynamic system the chaotic phenomenon can only appear in the autonomous system whose order is higher than three (included), which impels the research work in the nonlinear field to focus on the above-...In the nonlinear dynamic system the chaotic phenomenon can only appear in the autonomous system whose order is higher than three (included), which impels the research work in the nonlinear field to focus on the above-mentioned system. However,very complex dynamic phenomenon may also occur in the second-order autonomous sys-展开更多
针对可旋转翼式弹道修正组件滚转通道控制中存在的未建模摩擦干扰、参数不确定性和外部随机干扰造成的复合扰动问题,提出一种基于扩张状态观测器(extended state observer, ESO)的滑模控制方法。首先建立弹道修正组件滚转通道模型,将动...针对可旋转翼式弹道修正组件滚转通道控制中存在的未建模摩擦干扰、参数不确定性和外部随机干扰造成的复合扰动问题,提出一种基于扩张状态观测器(extended state observer, ESO)的滑模控制方法。首先建立弹道修正组件滚转通道模型,将动力学模型中存在的外部干扰、未建模摩擦干扰和参数摄动整合为复合干扰,然后设计ESO对修正组件滚转通道模型中难以直接测定的状态变量以及复合干扰进行估计,并基于估计值结合滑模控制理论设计滚转通道控制器,实现对滚转角指令的精确跟踪。综合考虑ESO和滑模控制器构成的闭环控制系统,利用Lyaponov稳定性理论证明了所设计的闭环控制系统的稳定性。最后,通过仿真实验分析,证明所设计的修正组件滚转通道控制器,对滚转角指令的瞬态响应和稳态性能优异,同时可以有效抑制系统复合扰动,具备较强的鲁棒性。展开更多
Canard explosion is a kind of complex temporal behavior and is ubiquitous in excitable systems. It is associated with an abrupt change of amplitude and period of an oscillatory trajectory in a very narrow interval of ...Canard explosion is a kind of complex temporal behavior and is ubiquitous in excitable systems. It is associated with an abrupt change of amplitude and period of an oscillatory trajectory in a very narrow interval of a control parameter. We have analyzed in the present paper the behavior of canard explosion that is near a supercritical Hopf bifurcation and its response to white noise in a temporal model of CO oxidation on platinum surface. We have found that the presence of canard explosion gives rise to internal signal stochastic bi-resonance, thus demonstrating a novel functional feature of noise: selective amplifying signals with different periods.展开更多
We consider the dynamics of planar fast-slow systems near generic transcritical type canard point.By using geometric singular perturbation theory combined with the recently developed blow-up technique, the existence o...We consider the dynamics of planar fast-slow systems near generic transcritical type canard point.By using geometric singular perturbation theory combined with the recently developed blow-up technique, the existence of canard cycles, relaxation oscillations and solutions near the attracting branch of the critical manifold is established. The asymptotic expansion of the parameter for which canard exists is obtained by a version of the Melnikov method.展开更多
文摘When discovering the potential of canards flying in 4-dimensional slow-fast system with a bifurcation parameter, the key notion “symmetry” plays an important role. It is of one parameter on slow vector field. Then, it should be determined to introduce parameters to all slow/fast vectors. It is, however, there might be no way to explore for another potential in this system, because the geometrical structure is quite different from the system with one parameter. Even in this system, the “symmetry” is also useful to obtain the potentials classified by R. Thom. In this paper, via the coordinates changing, the possible way to explore for the potential will be shown. As it is analyzed on “hyper finite time line”, or done by using “non-standard analysis”, it is called “Hyper Catastrophe”. In the slow-fast system which includes a very small parameter , it is difficult to do precise analysis. Thus, it is useful to get the orbits as a singular limit. When trying to do simulations, it is also faced with difficulty due to singularity. Using very small time intervals corresponding small , we shall overcome the difficulty, because the difference equation on the small time interval adopts the standard differential equation. These small intervals are defined on hyper finite number N, which is nonstandard. As and the intervals are linked to use 1/N, the simulation should be done exactly.
文摘There exists a property “structural stability” for “4-dimensional canards” which is a singular-limit solution in a slow-fast system with a bifurcation parameter. It means that the system includes the possibility to have some critical values on the bifurcation parameter. Corresponding to these values, the pseudo-singular point, which is a singular point in the time-scaled-reduced system should be changed to another one. Then, the canards may fly to another pseudo-singular point, if possible. Can the canards fly? The structural stability gives the possibility for the canards flying. The precise reasons why happen are described in this paper.
文摘Existing literature has shown that the control force at the nose could cause dynamic instability for controlled projectiles. To lower the adverse impact on the dual-spin projectile with fixed canards under the premise of meeting guidance system requirements, the influence of control moment provided by a motor on the flight stability is analyzed in this paper. Firstly, the effect of the rolling movement on stability is analyzed based on the stability criterion derived using the Hurwitz stability theory. Secondly, the evaluation parameters combining the features of different control periods that could assess the variation of stability features after the motor torque are obtained. These effective formulas are used to indicate that, to reduce the flight instability risks, the stabilized rolling speed of roll speed keeping period should be as small as possible; the variation trend of motor torque during the rolling speed controlling period and the roll angle of the forward body during roll angle switching period are recommended corresponding to the projectile and trajectory characteristics. Moreover,detailed numerical simulations of 155 mm dual-spin projectile are satisfactory agreement with the theoretical results.
文摘To study the rolling control characteristics of a canard-controlled missile, a series of wind tunnel experiment is conducted. The experimental method, the structure features of wind tunnel model and the experimental results are introduced in this paper. The experimental data show that the canard is an inefficient rolling control device for canard-controlled missile with fixed tail fins; but for the free-spinning tail fin configuration, the canard can conduct rolling control of the missile, and even have higher controlling efficiency under larger canard deflection angle.
基金Sponsored by the Fundamental Research Funds for the Central Universities(Grant No.HEUCFG201815)
文摘The steady flow field of a canard missile on different angles of attack and Mach numbers were studied. Based on analysis, a method was proposed to reduce the calculation for the rolling characteristics of the canard missile with free-spinning tails, and was tested to obtain the relations between rolling moment coefficient, Mach number, and angle of attack. All the computed rolling moment coefficients obtained from the proposed method greatly agreed with the experimental results of FD-06 wind tunnel in CAAA, which proved that the method can not only reduce the calculation cost but also keep precision in calculating the rolling characteristics of canard missiles.
文摘The classification on the orbits of some Liénard perturbation system with several parameters, which is relation to the example in [1] or [2], is discussed. The conditions for the parameters in order that the system has a unique limit cycle, homoclinic orbits, canards or the unique equilibrium point is globally asymptotic stable are given. The methods in our previous papers are used for the proofs.
文摘Let us consider higher dimensional canards in a sow-fast system R<sup>2+2</sup> with a bifurcation parameter. Then, the slow manifold sometimes shows various aspects due to the bifurcation. Introducing a key notion “symmetry” to the slow-fast system, it becomes clear when the pseudo singular point obtains the structural stability or not. It should be treated with a general case. Then, it will also be given about the sufficient conditions for the existence of the center manifold under being “symmetry”. The higher dimensional canards in the sow-fast system are deeply related to Hilbert’s 16th problem. Furthermore, computer simulations are done for the systems having Brownian motions. As a result, the rigidity for the system is confirmed.
文摘The canard explosion phenomenon in a predator-prey model with Michaelis-Menten functional response is analyzed in this paper by employing the geometric singular perturbation theory. First, some turning points, such as, fold point, transcritical point, pitchfork point, canard point, are identified;then Hopf bifurcation, relaxation oscillation, together with the canard transition from Hopf bifurcation to relaxation oscillation are discussed.
文摘The fixed canards configuration of a dual-spin projectile makes it difficult to apply the traditional guidance law. In this study, a modified impact point prediction guidance strategy based on an iterative process was developed for a class of dual-spin projectiles with fixed canards, to reduce the impact point dispersion. The guidance strategy is dependent on the modified projectile linear theory to rapidly predict the flight states and the impact point. For projectiles with control applied to the trajectory, the modified projectile linear theory method is known to achieve poor impact point prediction. To improve the prediction accuracy, improvements were made to the modified projectile linear theory by considering the products of the yaw rate and other small quantities.The guidance strategy is based on the iterative process for the continuous adjustment of the expected output of the roll angle of the course correction fuze, to minimize the direction error between the predicted impact point and target location. Studies were conducted on a model dual-spin projectile configuration to demonstrate the guidance details. The numerical simulations indicate that the proposed guidance strategy can effectively reduce the projectile impact point dispersion.
文摘The aerodynamic layout of the Canard Rotor/Wing(CRW) aircraft in helicopter flight mode differs significantly from that of conventional helicopters. In order to study the flight dynamics characteristics of CRW aircraft in helicopter mode, first, the aerodynamic model of the main rotor system is established based on the blade element theory and wind tunnel test results. The aerodynamic forces and moments of the canard wing, horizontal tail, vertical tail and fuselage are obtained via theoretical analysis and empirical formula. The flight dynamics model of the CRW aircraft in helicopter mode is developed and validated by flight test data. Next, a method of model trimming using an optimization algorithm is proposed. The flight dynamics characteristics of the CRW are investigated by the method of linearized small perturbations via Simulink. The trim results are consistent with the conventional helicopter characteristics, and the results show that with increasing forward flight speed, the canard wing and horizontal tail can provide considerable lift,which reflects the unique characteristics of the CRW aircraft. Finally, mode analysis is implemented for the linearized CRW in helicopter mode. The results demonstrate that the stability of majority modes increases with increasing flight speed. However, one mode that diverges monotonously,and the reason is that the CRW helicopter mode has a large vertical tail compared to the conventional helicopter. The results of the dynamic analysis provide optimization guidance and reference for the overall design of the CRW aircraft in helicopter mode, and the model developed can be used for control system design.
文摘In the nonlinear dynamic system the chaotic phenomenon can only appear in the autonomous system whose order is higher than three (included), which impels the research work in the nonlinear field to focus on the above-mentioned system. However,very complex dynamic phenomenon may also occur in the second-order autonomous sys-
文摘针对可旋转翼式弹道修正组件滚转通道控制中存在的未建模摩擦干扰、参数不确定性和外部随机干扰造成的复合扰动问题,提出一种基于扩张状态观测器(extended state observer, ESO)的滑模控制方法。首先建立弹道修正组件滚转通道模型,将动力学模型中存在的外部干扰、未建模摩擦干扰和参数摄动整合为复合干扰,然后设计ESO对修正组件滚转通道模型中难以直接测定的状态变量以及复合干扰进行估计,并基于估计值结合滑模控制理论设计滚转通道控制器,实现对滚转角指令的精确跟踪。综合考虑ESO和滑模控制器构成的闭环控制系统,利用Lyaponov稳定性理论证明了所设计的闭环控制系统的稳定性。最后,通过仿真实验分析,证明所设计的修正组件滚转通道控制器,对滚转角指令的瞬态响应和稳态性能优异,同时可以有效抑制系统复合扰动,具备较强的鲁棒性。
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 20203017 & 20433050)the Foundation for the Author of National Excellent Doctorial Dissertation of China (FANEDD).
文摘Canard explosion is a kind of complex temporal behavior and is ubiquitous in excitable systems. It is associated with an abrupt change of amplitude and period of an oscillatory trajectory in a very narrow interval of a control parameter. We have analyzed in the present paper the behavior of canard explosion that is near a supercritical Hopf bifurcation and its response to white noise in a temporal model of CO oxidation on platinum surface. We have found that the presence of canard explosion gives rise to internal signal stochastic bi-resonance, thus demonstrating a novel functional feature of noise: selective amplifying signals with different periods.
基金Supported by the National Natural Science Foundation of China(No.71501130)Natural Science Foundation of Hebei Province(A2015407063)
文摘We consider the dynamics of planar fast-slow systems near generic transcritical type canard point.By using geometric singular perturbation theory combined with the recently developed blow-up technique, the existence of canard cycles, relaxation oscillations and solutions near the attracting branch of the critical manifold is established. The asymptotic expansion of the parameter for which canard exists is obtained by a version of the Melnikov method.