Objective To explore three-dimensional relations of pedicle screw channel (PSC) ,screw entry point and lateral surface of cervical vertebral body by digital techniques. Methods CT scan images of cervical
Uncertain factors such as atmospheric density,aerodynamic coefficients,and aircraft mass can have a catastrophic impact on the flight safety of entry vehicles(EVs).It is crucial for EVs to quickly generate safe entry ...Uncertain factors such as atmospheric density,aerodynamic coefficients,and aircraft mass can have a catastrophic impact on the flight safety of entry vehicles(EVs).It is crucial for EVs to quickly generate safe entry trajectories that consider the impact of uncertainties to execute complex flight tasks such as online target changing.Given this challenge,a rapid generation method of safe entry trajectories is proposed,which is based on the drag-acceleration-profile method employed during space shuttle entry flights.This method can efficiently generate a safe,feasible trajectory while accounting for the influence of uncertain factors.Compared to traditional drag-acceleration-profile methods,the proposed method incorporates the influence of uncertain factors on the boundaries of the flight corridor.It establishes an uncertain flight corridor model,thereby ensuring the safety of the reference flight profile designed within this corridor under actual uncertain flight conditions.Additionally,a simplified design approach for the reference flight profile enables the rapid generation of satisfactory profiles through straightforward parameter iteration or optimization.Simulations demonstrate that this method can efficiently plan gliding flight trajectories that meet safety requirements,exhibiting potential for online trajectory generation and maneuverability assessment.展开更多
针对升力式再入飞行任务设计对地理信息的需求,提出了以"来路走廊"和"去路走廊"为代表的"三维再入走廊"概念,重新定义了"再入界面窗口"概念。其中,"再入界面窗口"解决了"已知...针对升力式再入飞行任务设计对地理信息的需求,提出了以"来路走廊"和"去路走廊"为代表的"三维再入走廊"概念,重新定义了"再入界面窗口"概念。其中,"再入界面窗口"解决了"已知着陆点,估计初始再入点的可行地理区间"问题;"三维再入走廊"则系统、直观地揭示了升力式再入飞行器对"临近空间"多重大气层的覆盖能力及其整体变化趋势。求解算法使用高精度积分律的直接配置非线性规划法,配合无奇异的数学模型,可满足全球到达任务的设计需求。基于美国X-33和Advanced Guidance and Control(AGC)项目的测试任务数据,一系列算例检验了"三维再入走廊"与"再入界面窗口"概念的合理性。"三维再入走廊"有助于工程总体设计、军事指挥和商业空天交通指挥人员对类型化的升力式再入任务进行设计和分析;有助于高层决策人士对升力式再入的机动能力进行系统理解和直观把握。展开更多
文摘Objective To explore three-dimensional relations of pedicle screw channel (PSC) ,screw entry point and lateral surface of cervical vertebral body by digital techniques. Methods CT scan images of cervical
基金supported by the National Nature Science Foundation of China(92271108,62173336)
文摘Uncertain factors such as atmospheric density,aerodynamic coefficients,and aircraft mass can have a catastrophic impact on the flight safety of entry vehicles(EVs).It is crucial for EVs to quickly generate safe entry trajectories that consider the impact of uncertainties to execute complex flight tasks such as online target changing.Given this challenge,a rapid generation method of safe entry trajectories is proposed,which is based on the drag-acceleration-profile method employed during space shuttle entry flights.This method can efficiently generate a safe,feasible trajectory while accounting for the influence of uncertain factors.Compared to traditional drag-acceleration-profile methods,the proposed method incorporates the influence of uncertain factors on the boundaries of the flight corridor.It establishes an uncertain flight corridor model,thereby ensuring the safety of the reference flight profile designed within this corridor under actual uncertain flight conditions.Additionally,a simplified design approach for the reference flight profile enables the rapid generation of satisfactory profiles through straightforward parameter iteration or optimization.Simulations demonstrate that this method can efficiently plan gliding flight trajectories that meet safety requirements,exhibiting potential for online trajectory generation and maneuverability assessment.
文摘针对升力式再入飞行任务设计对地理信息的需求,提出了以"来路走廊"和"去路走廊"为代表的"三维再入走廊"概念,重新定义了"再入界面窗口"概念。其中,"再入界面窗口"解决了"已知着陆点,估计初始再入点的可行地理区间"问题;"三维再入走廊"则系统、直观地揭示了升力式再入飞行器对"临近空间"多重大气层的覆盖能力及其整体变化趋势。求解算法使用高精度积分律的直接配置非线性规划法,配合无奇异的数学模型,可满足全球到达任务的设计需求。基于美国X-33和Advanced Guidance and Control(AGC)项目的测试任务数据,一系列算例检验了"三维再入走廊"与"再入界面窗口"概念的合理性。"三维再入走廊"有助于工程总体设计、军事指挥和商业空天交通指挥人员对类型化的升力式再入任务进行设计和分析;有助于高层决策人士对升力式再入的机动能力进行系统理解和直观把握。
