In order to strike hard targets underground or warships and tanks with expected impact angle by missiles or guided bombs, trajectory shaping guidance law with terminal position and impact angle constraints is derived ...In order to strike hard targets underground or warships and tanks with expected impact angle by missiles or guided bombs, trajectory shaping guidance law with terminal position and impact angle constraints is derived based on linear quadratic optimal control theory. The required accelera- tion expressed by impact angle and heading error is obtained in lag-free guidance system in order to find the optimal relationship of those angles in terminal phase. The adjoint systems of miss distance and impact angle error of first-order guidance system are established based on statistical linearization adjoint method （SLAM） in order to study the impact performances of the guidance law. Simulation results show that the miss distance and impact angle error of trajectory shaping guidance law are both according with the impact position and angle constraint and the required acceleration at impact can be decreased by an optimal relationship of impact angle and heading error.展开更多
A trajectory shaping guidance law based on virtua angle （TSGLBVA） is proposed for a re-entry vehicle with the constraints of terminal impact angles and their time derivatives. In the view of differential properties ...A trajectory shaping guidance law based on virtua angle （TSGLBVA） is proposed for a re-entry vehicle with the constraints of terminal impact angles and their time derivatives. In the view of differential properties of the maneuvering trajectory, a virtual angle and a virtual radius are defined. Also, the shaping trajectory of the vehicle is established by the polynomials of the virtual angle. Then, four optimized parameters are selected according to the theorem of parameters transformation presented in this paper. Finally, a convergent variant of the Nelder-Mead algorithm is adopted to obtain the reference trajectory, and a trajectory feedback tracking guidance law is designed. The simulation results demonstrate that the TSGLBVA ensures the re-entry vehicle to impact a target precisely from a specified direction with smal terminal load factor command, as well as to obtain a maximum or constrained terminal velocity according to various requirements.展开更多
To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware modification.Specif...To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware modification.Specifically,in the proposed scanning method,the piezoelectric actuator tracks a well-designed smooth periodic signal in x-direction,and simultaneously tracks a step signal in y-direction.The advantage of the proposed method is that it does not require additional data reprocessing to construct the morphology of the sample surface,while significantly increasing the scanning bandwidth restricted by the raster scanning method.Particularly,to directly utilize the height data collected by scanning to produce the sample morphology,the forward process in the common raster scanning mode is retained in the proposed method,the tracking signal in the forward process is thus set to a ramp function in x-direction.In addition,to ensure the continuity and smoothness of the entire tracking signal in x-direction,a segment of a sine curve is uniquely determined as the backward tracking signal by position and acceleration constraints,so as to ensure that the forward and backward curves are continuous and acceleration-continuous at the intersection point.Moreover,the frequency spectrum analysis of the designed smooth signal is carried out to exhibit the depressed amplitudes of high-frequency components,which demonstrates that the proposed method is able to reduce the resonance in AFM high-speed scanning,so as to improve the capacity of rapidly generating high-quality images.Finally,convincing comparison experiments are implemented to verify the imaging performance of the designed scanning algorithm.展开更多
A new three-dimensional missile guidance law to control the impact vector against a stationary target is proposed.The composite guidance law has two well-known components:Apollo descent guidance and trajectory shaping...A new three-dimensional missile guidance law to control the impact vector against a stationary target is proposed.The composite guidance law has two well-known components:Apollo descent guidance and trajectory shaping guidance.These respectively linear and planar guidance laws are combined to achieve a specified impact direction.The main idea is to define an impact plane and to steer the missile onto this plane using Apollo descent guidance while concurrently performing trajectory shaping with reference to the impact plane.The resulting guidance law is expressed by a single equation in vector form,which is straightforward to implement.Because it originates from an optimal formulation,the performance of the proposed technique is expected to be satisfactory.This is confirmed by comparative simulation runs,which also involve the method known as generalized explicit guidance.展开更多
基金Supported by the Aeronautical Science Foundation of China(20060112123)
文摘In order to strike hard targets underground or warships and tanks with expected impact angle by missiles or guided bombs, trajectory shaping guidance law with terminal position and impact angle constraints is derived based on linear quadratic optimal control theory. The required accelera- tion expressed by impact angle and heading error is obtained in lag-free guidance system in order to find the optimal relationship of those angles in terminal phase. The adjoint systems of miss distance and impact angle error of first-order guidance system are established based on statistical linearization adjoint method （SLAM） in order to study the impact performances of the guidance law. Simulation results show that the miss distance and impact angle error of trajectory shaping guidance law are both according with the impact position and angle constraint and the required acceleration at impact can be decreased by an optimal relationship of impact angle and heading error.
文摘A trajectory shaping guidance law based on virtua angle （TSGLBVA） is proposed for a re-entry vehicle with the constraints of terminal impact angles and their time derivatives. In the view of differential properties of the maneuvering trajectory, a virtual angle and a virtual radius are defined. Also, the shaping trajectory of the vehicle is established by the polynomials of the virtual angle. Then, four optimized parameters are selected according to the theorem of parameters transformation presented in this paper. Finally, a convergent variant of the Nelder-Mead algorithm is adopted to obtain the reference trajectory, and a trajectory feedback tracking guidance law is designed. The simulation results demonstrate that the TSGLBVA ensures the re-entry vehicle to impact a target precisely from a specified direction with smal terminal load factor command, as well as to obtain a maximum or constrained terminal velocity according to various requirements.
基金supported by the National Natural Science Foundation of China(Nos.62003172,61633012,and 21933006).
文摘To improve the scanning speed of an atomic force microscopy(AFM),a smooth scanning pattern is elaborately devised via trajectory shaping in this paper,so as to achieve fast imaging without hardware modification.Specifically,in the proposed scanning method,the piezoelectric actuator tracks a well-designed smooth periodic signal in x-direction,and simultaneously tracks a step signal in y-direction.The advantage of the proposed method is that it does not require additional data reprocessing to construct the morphology of the sample surface,while significantly increasing the scanning bandwidth restricted by the raster scanning method.Particularly,to directly utilize the height data collected by scanning to produce the sample morphology,the forward process in the common raster scanning mode is retained in the proposed method,the tracking signal in the forward process is thus set to a ramp function in x-direction.In addition,to ensure the continuity and smoothness of the entire tracking signal in x-direction,a segment of a sine curve is uniquely determined as the backward tracking signal by position and acceleration constraints,so as to ensure that the forward and backward curves are continuous and acceleration-continuous at the intersection point.Moreover,the frequency spectrum analysis of the designed smooth signal is carried out to exhibit the depressed amplitudes of high-frequency components,which demonstrates that the proposed method is able to reduce the resonance in AFM high-speed scanning,so as to improve the capacity of rapidly generating high-quality images.Finally,convincing comparison experiments are implemented to verify the imaging performance of the designed scanning algorithm.
文摘A new three-dimensional missile guidance law to control the impact vector against a stationary target is proposed.The composite guidance law has two well-known components:Apollo descent guidance and trajectory shaping guidance.These respectively linear and planar guidance laws are combined to achieve a specified impact direction.The main idea is to define an impact plane and to steer the missile onto this plane using Apollo descent guidance while concurrently performing trajectory shaping with reference to the impact plane.The resulting guidance law is expressed by a single equation in vector form,which is straightforward to implement.Because it originates from an optimal formulation,the performance of the proposed technique is expected to be satisfactory.This is confirmed by comparative simulation runs,which also involve the method known as generalized explicit guidance.
