The challenge and control problems of static unstable missiles are presented. The steady-state benefits of static instability are illustrated, while the corresponding control challenge is described both by the charact...The challenge and control problems of static unstable missiles are presented. The steady-state benefits of static instability are illustrated, while the corresponding control challenge is described both by the characteristic lag of airframe and the increment of necessary control usage. Control limitation led by unstable zero-pole pair is analyzed for preliminary design and evaluation. Linear control strategy is examined wherein two and three loop acceleration autopilots with different control usages are developed using an optimal control approach combined with frequency domain constraint. The weights selection and relation with system performance are detailed. Then the nonlinear backstepping recursive method is detailed to determine how well it is able to follow command and its engineering feasibility. The results show that a static unstable missile is controllable, while the actuator bandwidth is the crucial limited factor. There should be a compromise between overall performance and actuator payment.展开更多
对于多输入多输出系统,在控制系统设计时首先要对被控变量和操纵变量进行控制结构选择.Bristol提出的相关增益矩阵(Relative gain array,RGA)法,以及学者们后来提出的各种改进方法,都只适用于稳定系统.本文针对不稳定系统,基于多变量广...对于多输入多输出系统,在控制系统设计时首先要对被控变量和操纵变量进行控制结构选择.Bristol提出的相关增益矩阵(Relative gain array,RGA)法,以及学者们后来提出的各种改进方法,都只适用于稳定系统.本文针对不稳定系统,基于多变量广义预测控制(Generalized predictive control,GPC)的闭环控制律提出了一种控制结构的变量匹配准则.通过对预测时域、控制时域等各个参数的优化选择,使系统闭环稳定;由闭环控制律得到被控变量期望值与操纵变量的相关性矩阵,以此得出控制结构的变量配对方案.通过实例研究表明,对于开环不稳定系统,该方法可以得出正确的变量配对结果.展开更多
Mixing and coherence are fundamental issues at the heart of understanding fluid dynamics and other non-autonomous dynamical systems. Recently the notion of coherence has come to a more rigorous footing, in particular,...Mixing and coherence are fundamental issues at the heart of understanding fluid dynamics and other non-autonomous dynamical systems. Recently the notion of coherence has come to a more rigorous footing, in particular, within the studies of finite-time nonautonomous dynamical systems. Here we recall “shape coherent sets” which is proven to correspond to slowly evolving curvature, for which tangency of finite time stable foliations (related to a “forward time” perspective) and finite time unstable foliations (related to a “backwards time” perspective) serve a central role. We compare and contrast this perspective to both the variational method of geodesics [17], as well as the coherent pairs perspective [12] from transfer operators.展开更多
基金supported by the National Natural Science Foundation of China (60972118)the Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality (PHR200906131 PHR201006115)
文摘The challenge and control problems of static unstable missiles are presented. The steady-state benefits of static instability are illustrated, while the corresponding control challenge is described both by the characteristic lag of airframe and the increment of necessary control usage. Control limitation led by unstable zero-pole pair is analyzed for preliminary design and evaluation. Linear control strategy is examined wherein two and three loop acceleration autopilots with different control usages are developed using an optimal control approach combined with frequency domain constraint. The weights selection and relation with system performance are detailed. Then the nonlinear backstepping recursive method is detailed to determine how well it is able to follow command and its engineering feasibility. The results show that a static unstable missile is controllable, while the actuator bandwidth is the crucial limited factor. There should be a compromise between overall performance and actuator payment.
文摘对于多输入多输出系统,在控制系统设计时首先要对被控变量和操纵变量进行控制结构选择.Bristol提出的相关增益矩阵(Relative gain array,RGA)法,以及学者们后来提出的各种改进方法,都只适用于稳定系统.本文针对不稳定系统,基于多变量广义预测控制(Generalized predictive control,GPC)的闭环控制律提出了一种控制结构的变量匹配准则.通过对预测时域、控制时域等各个参数的优化选择,使系统闭环稳定;由闭环控制律得到被控变量期望值与操纵变量的相关性矩阵,以此得出控制结构的变量配对方案.通过实例研究表明,对于开环不稳定系统,该方法可以得出正确的变量配对结果.
文摘Mixing and coherence are fundamental issues at the heart of understanding fluid dynamics and other non-autonomous dynamical systems. Recently the notion of coherence has come to a more rigorous footing, in particular, within the studies of finite-time nonautonomous dynamical systems. Here we recall “shape coherent sets” which is proven to correspond to slowly evolving curvature, for which tangency of finite time stable foliations (related to a “forward time” perspective) and finite time unstable foliations (related to a “backwards time” perspective) serve a central role. We compare and contrast this perspective to both the variational method of geodesics [17], as well as the coherent pairs perspective [12] from transfer operators.
