A novel hybrid robust three-axis attitude control approach, namely HRTAC, is considered along with the well-known developments in the area of space systems, since there is a consensus among the related experts that th...A novel hybrid robust three-axis attitude control approach, namely HRTAC, is considered along with the well-known developments in the area of space systems, since there is a consensus among the related experts that the new insights may be taken into account as decision points to outperform the available materials. It is to note that the traditional control approaches may generally be upgraded, as long as a number of modifications are made with respect to state-of-the-art, in order to propose high-precision outcomes. Regarding the investigated issues, the robust sliding mode finite-time control approach is first designed to handle three-axis angular rates in the inner control loop, which consists of the pulse width pulse frequency modulations in line with the control allocation scheme and the system dynamics. The main subject to employ these modulations that is realizing in association with the control allocation scheme is to be able to handle a class of overactuated systems, in particular. The proportional derivative based linear quadratic regulator approach is then designed to handle three-axis rotational angles in the outer control loop, which consists of the system kinematics that is correspondingly concentrated to deal with the quaternion based model. The utilization of the linear and its nonlinear terms, simultaneously, are taken into real consideration as the research motivation, while the performance results are of the significance as the improved version in comparison with the recent investigated outcomes. Subsequently, there is a stability analysis to verify and guarantee the closed loop system performance in coping with the whole of nominal referenced commands. At the end, the effectiveness of the approach considered here is highlighted in line with a number of potential recent benchmarks.展开更多
针对Hilbert-Huang变换方法中由于信号经验模态分解(empirical mode decomposition,简称EMD)过程中所存在的端点效应问题,分析了现有数据延拓方式的利弊,并在基于斜率(slope based method,简称SBM)方法以及改进方法(improved slope base...针对Hilbert-Huang变换方法中由于信号经验模态分解(empirical mode decomposition,简称EMD)过程中所存在的端点效应问题,分析了现有数据延拓方式的利弊,并在基于斜率(slope based method,简称SBM)方法以及改进方法(improved slope based method,简称ISBM)的基础上提出了一种全新的基于斜率再优化(reoptimization slope based method,简称RO-SBM)方法用于信号序列的极值点延拓,然后对延拓后的数据进行EMD分解,得到相应的本征模函数(intrinsic mode function,简称IMF)分量。数值仿真结果表明,采用基于RO-SBM方法进行数据延拓,相比镜像延拓以及ISBM方法,可以更有效地抑制EMD中的端点效应问题,提升HHT方法的信号分析性能。通过基于RO-SBM方法进行数据延拓的HHT方法准确分离出了某转子系统的局部碰摩径向振动信号中所包含的故障特征分量,并将此方法成功应用于旋转机械故障诊断领域。展开更多
针对绕墙底转动模式(the mode of rotating about the base,RB)的挡土墙,通过同时考虑墙后滑裂部分土体所产生的土拱效应以及土层间的剪应力,假定墙后的小主应力拱迹线为圆弧形,拱轴线随土深的改变而改变,墙体位移量与土体内、外摩擦角...针对绕墙底转动模式(the mode of rotating about the base,RB)的挡土墙,通过同时考虑墙后滑裂部分土体所产生的土拱效应以及土层间的剪应力,假定墙后的小主应力拱迹线为圆弧形,拱轴线随土深的改变而改变,墙体位移量与土体内、外摩擦角呈非线性函数关系,利用水平层分析法,修正了非极限状态下的侧向主动土压力系数,建立平衡方程,推导了RB模式下挡土墙非极限主动土压力的计算公式。研究结果表明,相比其他方法,本文理论值与试验值吻合得更好,验证了公式的合理性;随着墙顶位移量的增大,土压力呈更加明显的凹曲线分布,在墙顶会小于库仑土压力,墙底始终大于静止土压力,土压力合力逐渐减小,作用点高度降低。展开更多
文摘A novel hybrid robust three-axis attitude control approach, namely HRTAC, is considered along with the well-known developments in the area of space systems, since there is a consensus among the related experts that the new insights may be taken into account as decision points to outperform the available materials. It is to note that the traditional control approaches may generally be upgraded, as long as a number of modifications are made with respect to state-of-the-art, in order to propose high-precision outcomes. Regarding the investigated issues, the robust sliding mode finite-time control approach is first designed to handle three-axis angular rates in the inner control loop, which consists of the pulse width pulse frequency modulations in line with the control allocation scheme and the system dynamics. The main subject to employ these modulations that is realizing in association with the control allocation scheme is to be able to handle a class of overactuated systems, in particular. The proportional derivative based linear quadratic regulator approach is then designed to handle three-axis rotational angles in the outer control loop, which consists of the system kinematics that is correspondingly concentrated to deal with the quaternion based model. The utilization of the linear and its nonlinear terms, simultaneously, are taken into real consideration as the research motivation, while the performance results are of the significance as the improved version in comparison with the recent investigated outcomes. Subsequently, there is a stability analysis to verify and guarantee the closed loop system performance in coping with the whole of nominal referenced commands. At the end, the effectiveness of the approach considered here is highlighted in line with a number of potential recent benchmarks.
文摘针对Hilbert-Huang变换方法中由于信号经验模态分解(empirical mode decomposition,简称EMD)过程中所存在的端点效应问题,分析了现有数据延拓方式的利弊,并在基于斜率(slope based method,简称SBM)方法以及改进方法(improved slope based method,简称ISBM)的基础上提出了一种全新的基于斜率再优化(reoptimization slope based method,简称RO-SBM)方法用于信号序列的极值点延拓,然后对延拓后的数据进行EMD分解,得到相应的本征模函数(intrinsic mode function,简称IMF)分量。数值仿真结果表明,采用基于RO-SBM方法进行数据延拓,相比镜像延拓以及ISBM方法,可以更有效地抑制EMD中的端点效应问题,提升HHT方法的信号分析性能。通过基于RO-SBM方法进行数据延拓的HHT方法准确分离出了某转子系统的局部碰摩径向振动信号中所包含的故障特征分量,并将此方法成功应用于旋转机械故障诊断领域。
文摘针对绕墙底转动模式(the mode of rotating about the base,RB)的挡土墙,通过同时考虑墙后滑裂部分土体所产生的土拱效应以及土层间的剪应力,假定墙后的小主应力拱迹线为圆弧形,拱轴线随土深的改变而改变,墙体位移量与土体内、外摩擦角呈非线性函数关系,利用水平层分析法,修正了非极限状态下的侧向主动土压力系数,建立平衡方程,推导了RB模式下挡土墙非极限主动土压力的计算公式。研究结果表明,相比其他方法,本文理论值与试验值吻合得更好,验证了公式的合理性;随着墙顶位移量的增大,土压力呈更加明显的凹曲线分布,在墙顶会小于库仑土压力,墙底始终大于静止土压力,土压力合力逐渐减小,作用点高度降低。
