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
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
This paper gives a succinct review of dual-spinprojectile stability and some technologies relating to them.It describes how the traditional stability factors from linear projectile theory are modified to better descri...This paper gives a succinct review of dual-spinprojectile stability and some technologies relating to them.It describes how the traditional stability factors from linear projectile theory are modified to better describe a controlled dual-spin projectile.Finally,it reviews works which have investigated how different aspects of a controlled dual-spin design can affect flight stability,primarily airframe structure and canard properties.A conclusion is given,highlighting important guidelines from the enclosed discussions.展开更多
The attitude motion of a dual-spin spacecraft composed of two asymmetric bodies isdiscussed by using the method in Refs. [1-3] in combination with asymptotic expansionequations and averaging algorithm. The nutational ...The attitude motion of a dual-spin spacecraft composed of two asymmetric bodies isdiscussed by using the method in Refs. [1-3] in combination with asymptotic expansionequations and averaging algorithm. The nutational stability is calculated. The dynamic trapstate, i. e. a nonlinear resonance in the attitude motion, is investigated when the spin rateof the rotor comes near that of the relative rotation during the despun process. The presenceof trap state is shown to depend on double transverse inertia asymmetry between the rotorand platform.展开更多
Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in spintronics.Inspired by the progress on atomic-level molecular synthesis,...Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in spintronics.Inspired by the progress on atomic-level molecular synthesis,through firstprinciples calculations,we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups,contacted by atomic carbon chain electrodes.It is found that,by rotating the functional group,the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states.Moreover,the transition between spin-up and spin-down polarized states can also be achieved,operating as a dual-spin filter.Further analysis shows that,it is the spin-dependent shift of density of states,caused by the rotation,that triggers the shift of transmission peaks,and then results in the variation of spin polarization.Such a feature is found to be robust to the length of the nanoflake and the electrode material,showing great application potential.Those findings may throw light on the development of spintronic devices.展开更多
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.
基金sponsored by EPSRC ICASE Grant reference 1700064BAE Systems。
文摘This paper gives a succinct review of dual-spinprojectile stability and some technologies relating to them.It describes how the traditional stability factors from linear projectile theory are modified to better describe a controlled dual-spin projectile.Finally,it reviews works which have investigated how different aspects of a controlled dual-spin design can affect flight stability,primarily airframe structure and canard properties.A conclusion is given,highlighting important guidelines from the enclosed discussions.
基金Project supported by National Natural Science Foundation of China.
文摘The attitude motion of a dual-spin spacecraft composed of two asymmetric bodies isdiscussed by using the method in Refs. [1-3] in combination with asymptotic expansionequations and averaging algorithm. The nutational stability is calculated. The dynamic trapstate, i. e. a nonlinear resonance in the attitude motion, is investigated when the spin rateof the rotor comes near that of the relative rotation during the despun process. The presenceof trap state is shown to depend on double transverse inertia asymmetry between the rotorand platform.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11705097,11504178,and 11804158)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20170895)the Funding of Jiangsu Innovation Program for Graduate Education(Grant No.KYCX21_0709)
文摘Controlling the spin transport at the single-molecule level,especially without the use of ferromagnetic contacts,becomes a focus of research in spintronics.Inspired by the progress on atomic-level molecular synthesis,through firstprinciples calculations,we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups,contacted by atomic carbon chain electrodes.It is found that,by rotating the functional group,the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states.Moreover,the transition between spin-up and spin-down polarized states can also be achieved,operating as a dual-spin filter.Further analysis shows that,it is the spin-dependent shift of density of states,caused by the rotation,that triggers the shift of transmission peaks,and then results in the variation of spin polarization.Such a feature is found to be robust to the length of the nanoflake and the electrode material,showing great application potential.Those findings may throw light on the development of spintronic devices.
