Probabilistic Robust Linear Parameter-varying Control of a Small Helicopter Using Iterative Scenario Approach

In this paper, we present an iterative scenario approach (ISA) to design robust controllers for complex linear parameter-varying (LPV) systems with uncertainties. The robust controller synthesis problem is transformed to a scenario design problem, with the scenarios generated by identically extracting random samples on both uncertainty parameters and scheduling parameters. An iterative scheme based on the maximum volume ellipsoid cutting-plane method is used to solve the problem. Heuristic logic based on relevance ratio ranking is used to prune the redundant constraints, and thus, to improve the numerical stability of the algorithm. And further, a batching technique is presented to remarkably enhance the computational efficiency. The proposed method is applied to design an output-feedback controller for a small helicopter. Multiple uncertain physical parameters are considered, and simulation studies show that the closed-loop performance is quite good in both aspects of model tracking and dynamic decoupling. For robust LPV control problems, the proposed method is more computationally efficient than the popular stochastic ellipsoid methods.      

Wind turbine integrated structural and LPV control design for improved closed-loop performance

An iterative redesign algorithm is proposed to integrate the design of the structural parameters and a linear parameter-varying (LPV) controller for a three-bladed horizontal-axis wind turbine. The LPV controller is designed for an eighth-order lumped model of the wind turbine consisting of blades, drive-train and the tower. The lumped model response is matched with detailed open-loop numerical simulations using the Fatigue, Aerodynamics, Structures and Turbulence (FAST) code. The controller is scheduled in real-time based on the mean wind speed to account for the varying system dynamics. The objective is to track the operating trajectory meanwhile minimise the H _∞ performance index from the wind turbulence to the controlled output vector consisting of pitch angle, blade tip deflection, and the generator speed and torque. Sensitivity analysis of the closed-loop performance index with respect to the structural parameters of the system is examined. The integrated design problem is formulated as an iterative sequential controller/structure redesign to obtain the structural parameters and controller matrices corresponding to a local optimal performance index. Each step of the iterative procedure is formulated as a linear matrix inequality (LMI) optimisation problem that can be solved efficiently using available LMI solvers. The evolution of the structural parameters and performance index through the integrated design is illustrated. The FAST closed-loop simulations for two selected designs with the smallest values of the performance index demonstrate the improved performance of the overall system through the integrated structure/control redesign in both minimising the effect of the wind disturbance on the generator output power, and reducing the structural loads on the wind turbine.     

基于LPV 方法的Stewart 平台关节空间分散控制

为了提高Stewart 平台关节空间分散控制系统的性能,提出一种基于线性变参数(Linear Parameter Varying,LPV) 方法的控制策略．首先建立了平台关节空间动力学模型;通过分析平台惯性矩阵,指出单支路 子系统等效负载变化以及子系统间的耦合干扰是分散控制需要处理的主要问题．然后将平台惯性矩阵分解为 一个对角阵与一个耦合阵之和,子系统间耦合作用视为对单支路的干扰,从而得到每个子系统的动力学方程． 最后针对子系统等效负载随着上平台运动而在较大范围内变化的特点,引入LPV 控制方法,使控制器参数能 够适应子系统负载变化,减少了保守性．仿真结果表明了所提方法的有效性．     

Multiple Lyapunov Functions with Blending for Induced L2‐norm Control of Switched LPV Systems and its Application to an F‐16 Aircraft Model

This paper studies the induced L₂‐norm problem for switched linear parameter varying (LPV) systems using a blending method. For a switched LPV system where the parameters are grouped into slow‐varying and fast‐varying parameters, the blending method is used to construct blended Lyapunov functions based on the multiple Lyapunov functions conditions in terms of linear matrix inequalities (LMIs). The proposed method is applied to an F‐16 aircraft longitudinal model and the simulation results demonstrate the effectiveness of the approach.     

Stability analysis and control of a class of LPV systems with piecewise constant parameters

Stability criteria characterizing the asymptotic stability of a class of LPV systems with piecewise constant parameters under constant and minimum dwell-time are derived. It is shown that, for such systems, the conditions for the stability under minimum dwell-time can be seen as a unifying stability concept lying in between quadratic and robust stability, thereby including them as extremal cases. The results are then extended to address the stabilization problem using a particular class of time-dependent gain-scheduled state-feedback controllers. Several examples are given for illustration.     

LPV鲁棒故障观测器设计

针对线性参数变化（Linear Parameter Varying,LPV）系统的故障检测问题,采用H_- / H_∞混合优化方法,对基于LPV模型的鲁棒故障观测器（RFDO）进行设计,基于离散的参数依赖李亚普诺夫函数,得到了系统的LPV鲁棒故障观测器的综合条件,经过转化,观测器的设计问题被转化为一组线性矩阵不等式的求解问题;利用LMI工具求解线性矩阵不等式,得到了系统的LPV鲁棒故障观测器。最后,通过在一点上对故障输入的非线性仿真,验证了该方法的有效性。     

基于变增益控制理论的感应电机转子磁链观测

针对交流感应电动机转子磁链观测问题,提出一种新的方法,基于变增益控制理论设计感应电机转子磁链观测器。首先把感应电动机模型作为LPV线性变参数系统,将感应电动机的磁通观测器看作线性变参数系统的一个控制器,而把转速与转子电阻作为系统的变参数,然后利用变增益控制理论,通过解一组线性矩阵不等式,设计满足H∞鲁棒稳定性能和动态特性磁链观测器,跟踪实际的磁链。仿真验证了此观测器的有效性和先进性。     

基于LPV的变增益控制技术及其在航空航天领域的应用

基于LPV系统的变增益控制克服了传统变增益控制的缺点,不仅减少了繁杂的前期工作,而且也使得系统的稳定性和性能分析在理论上变得简单易用。文章分析了基于IJPV系统变增益控制的发展过程,给出了基于LPV变增益控制器的综合方法,总结了近年来航空航天领域应用该项技术的成果,并根据LPV变增益控制的发展趋势,提出了基于LPV变增益控制需要解决的四个问题,即非线性系统的LPV系统的建模、基于Lyapunov函数的线性矩阵不等式计算量、变参数变化速率和调度策略,同时提出了简单的解决思路。