Anti-disturbance backstepping control for air-breathing hypersonic vehicles based on extended state observer

In this paper, we propose an anti-disturbance backstepping control approach with extended state observer (ESO) for tracking control of air-breathing hypersonic vehicles. Considering the large uncertainties, the external disturbances, and especially the lack of aerodynamic knowledge, several ESOs are introduced in the backstepping controller. With the total disturbance estimation ability of ESOs, almost no aerodynamic knowledge is needed for the controller design. Meanwhile, ESOs are also used to estimate the derivatives of the virtual control signals. The problem of “explosion of terms” is avoided. A key strategy of the controller is that each step of backstepping is activated successively. Consequently, the closed-loop system has time-scale structure. Rigorous stability proof can be obtained. At last, compared simulation results verify the superior tracking performance of the proposed controller.     

A new discrete-time robust adaptive time-delay control for a class of uncertain nonlinear strict-feedback systems using sliding mode

This paper presents a new discrete-time adaptive second-order sliding mode control with time delay estimation (TDE) for a class of uncertain nonlinear time-varying strict-feedback systems. The existing researches on time delay control (TDC) are conventionally established based on a stability criterion that is subject to the infinitesimal time delay assumption. Recently, this criterion was rejected and a new criterion was proposed for the development of a controller for systems with fully known dynamics. In this study, this approach is extended to uncertain systems. Specifically, a new criterion is developed for the stability of the TDE-error within an adaptive robust controller design without the infinitesimal time delay assumption. With the proposed adaptive robust control, there is no need for determination of uncertainties upper-bounds. Simulation results illustrate the efficacy of the proposed controller.     

Fixed-time output feedback trajectory tracking control of marine surface vessels subject to unknown external disturbances and uncertainties

This paper proposes a novel fixed-time output feedback control scheme for trajectory tracking of marine surface vessels (MSVs) subject to unknown external disturbances and uncertainties. A fixed-time extended state observer (FESO) is proposed to estimate unknown lumped disturbances and unmeasured velocities, and the observation errors will converge to zero in fixed time. Based on the estimated values, a novel fixed-time trajectory tracking controller is designed for an MSV to track a time-varying reference trajectory by the extension of an adding a power integrator (API), and the tracking errors can converge to zero in fixed time as well. Additionally, the convergence time of the controller and the FESO is independent of initial state values. Finally, simulation results and comparisons illustrate the superiority of the proposed control scheme.     

Design and performance analysis of an iterative flux sliding-mode observer for the sensorless control of PMSM drives

To improve the performance of permanent magnet synchronous motor (PMSM) drives, a sensorless control scheme based on a novel iterative flux sliding-mode observer (IFSMO) is proposed in this paper. Two major drawbacks of the conventional sliding-mode observer (SMO), namely, chattering phenomena and high-order harmonics, are discussed. These drawbacks affect the estimation accuracy of the SMO and reduce the control reliability of the system. To eliminate high-order harmonics, a flux SMO is designed by expanding the PMSM state equations with the PM flux. The flux SMO estimates the rotor speed and position using the flux linkage instead of back-EMF information. Moreover, to reduce the chattering in the estimation results, the proposed flux SMO is iteratively used in one current sampling period to adaptively adjust the observer gain. An overall PMSM sensorless control system based on the proposed IFSMO is designed, and an experimental platform using the TMS320F28335 digital signal processor (DSP) controller is built. The superior chattering reduction and harmonic suppression characteristics of the proposed IFSMO are experimentally validated, and the experimental results verify the feasibility of using the proposed IFSMO-based PMSM sensorless scheme in practical applications.     

基于蚂蚁算法和SVR的离散变量稳健设计优化

引入蚁群打散、离散搜索等策略对基本蚂蚁算法进行了改进,并采用MATLAB语言编制了离散变量优化设计的蚂蚁算法程序。采用支持向量回归机对模糊概率等非线性函数进行仿真计算．提高了模糊稳健优化设计的求解效率。给出了混合离散变量的稳健优化设计实例,表明了所提出方法的有效性和实用性。     

鲁棒性概率优化在乘员约束系统设计中的应用

利用MADYMO软件建立了国内某微型车正面碰撞数学模型,并在对模型进行试验验证的基础上结合试验设计、响应面方法和鲁棒性概率优化设计对乘员侧约束系统进行优化,优化的参数主要有安全带刚度、安全带上挂点位置、限力器撕裂力和撕裂增加长度等。采用该方法引入鲁棒性概率优化设计后能减少和控制目标函数响应的波动,降低在设计点上的敏感性,提高产品的质量。结果表明,所采用的方法既实现了对设计目标的优化,又提高了设计变量的可靠性和目标函数的鲁棒性,对工程应用具有较大指导意义。     

基于MSRE的机械产品质量特性稳健优化设计方法

为了解决产品质量特性优化设计过程中设计参数发生变差时,最优解变为违反约束条件的不可行解的问题,对产品质量特性的稳健性和稳健性度量进行了分析,建立了基于最小灵敏域估计的产品质量特性稳健优化数学模型,提出了多目标产品质量特性稳健优化设计流程。根据该模型,采用广义差分多目标进化算法求得多目标质量特性稳健优化问题的Pareto稳健优化解集,并使用基于模糊集合理论的方法选择出最优解。在满足产品质量特性设计要求的前提下,优化产品质量特性,提高产品质量特性性能对设计参数变差的稳健性。最后,应用该方法对高速工业平缝机挑线机构进行质量特性稳健优化设计,证明了该方法在工程应用中的正确性与高效性。     

转向工况下主动悬架H_2/H_∞鲁棒控制研究

以转向工况下整车主动悬架系统为研究对象,用线性分式变换理论对悬架参数进行不确定性分析,应用频率加权函数对不确定性系统进行频率加权增广描述,采用H2/H∞鲁棒控制方法,对系统进行仿真分析。仿真结果表明H/H鲁棒控制可以较好地提高悬架系统综合性能。     

无人旋翼机线性自抗扰航向控制

研究无人旋翼机器人在干扰情况下的航向控制问题.无人旋翼机航向动力学包含输入非线性、时变参数和主-尾旋翼之间的强耦合,难以建立精确的数学模型,并且易受外部扰动影响,很难达到良好的控制性能.针对这一问题提出基于线性自抗扰控制(linear adaptive disturbance rejection control,LADRC)的航向控制方法,通过设计扩张线性状态观测器对未知模型和外界干扰进行实时估计并进行在线补偿.以自主研制的无人旋翼机为例,建立其航向动力学方程,把通道间的交叉耦合影响视为不确定扰动,将其与外部干扰作为扩张状态,利用观测器带宽确定观测器增益,设计线性扩张状态观测器来跟踪各阶扩张状态变量,为说明LADRC的有效性,选用PD控制为非线性状态误差反馈控制律实现航向控制.仿真以及试验结果表明在外部扰动或模型结构参数发生变化时控制器仍可获得理想的动态性能,具有很好的适应性和鲁棒性.     

基于改进贝叶斯方法的稳健性设计建模技术

针对模型不确定性条件下的稳健参数设计问题,在贝叶斯模型平均方法的基础上,通过考虑因子效应原则,提出基于因子效应原则的贝叶斯模型平均(BMA-EP)稳健性设计建模技术.结合先验信息与贝叶斯法则,计算主效应的后验概率并构建传统的贝叶斯模型平均模型;根据各主效应的后验概率,逐步运用效应层次原则和效应遗传原则更新各主效应的先验,确定模型的后验概率,并以该后验概率作为权重,对各模型进行加权,得到预测性能较佳且符合试验设计原则的稳健性模型.结合实际工业案例和仿真试验验证了所提方法的有效性,结果表明,所提方法不但改善了模型的预测性能,而且提高了最佳参数设置的可靠性.