扰动抑制无模型自适应控制的鲁棒性分析

针对一类存在测量扰动的SISO非线性离散时间系统,研究无模型自适应控制算法的扰动作用问题.首先给出了系统输出误差与测量扰动的关系,分析了测量扰动对控制性能的影响.然后提出了一种带有滤波器的改进无模型自适应控制算法,该算法较常规无模型自适应控制算法可有效抑制测量扰动的作用.仿真结果验证了理论分析的正确性.     

基于扰动补偿的无微分模型参考自适应控制系统设计

针对一类含有参数不确定性和未知非线性扰动的系统,本文提出一种基于扰动补偿的无微分模型参考自适应控制方法,实现系统输出对参考模型输出信号的高精度跟踪.首先,利用被控对象模型信息设计扰动估计器,对系统非线性扰动进行在线估计;其次,基于非线性扰动估计值设计参考模型和无微分参数更新律,构建无微分模型参考自适应控制器,建立基于扰动补偿和状态反馈的自适应控制律,以消除参数不确定性和非线性扰动对系统输出的影响,保证系统输出对参考模型输出的准确跟踪;然后,给出闭环系统误差信号收敛条件和控制器参数整定方法;最后,通过数值仿真验证所提方法的有效性和优越性.     

基于时延估计的扰动卡尔曼滤波器外力估计

针对机械臂末端力估计存在模型误差及系统扰动等问题,提出了一种基于时延估计的扰动卡尔曼滤波器外力估计法。在不使用额外力传感器的情况下,通过电机驱动电流的测量,采用时间延时估计法设计出不需要精确动力学模型的估计器。将外力作为状态变量,对系统的不确定性和扰动进行观测,考虑机械臂动力学和扰动动力学,设计出扰动卡尔曼滤波器来估计末端所受外力。使用Matlab仿真软件验证了该方法的有效性,结果表明所提估计方法对具有测量噪声、模型误差及不确定性扰动的系统具有很好的鲁棒性。     

具有外部扰动的PMSM系统的无模型自适应预测控制

针对于一类具有强耦合、负载不确定性和外界干扰的永磁同步电机(PMSM)系统,本文研究了基于无模型自适应预测控制(MFAPC)问题,并提出了一种新颖的MFAPC方案来实现有外界扰动的PMSM系统的速度追踪任务.所提出控制方案的主要优势在于仅使用了被控系统的输入/输出数据,并且对外界干扰具有较强的鲁棒性.此外,还讨论了闭环系统跟踪误差的收敛性以及有界输入有界输出的稳定性.最后,通过与传统的PI控制方案、原型无模型自适应控制(MFAC)方案的仿真结果相比较,验证了所提出MFAPC方案的有效性和优越性.     

基于有界扰动分区的多模型自适应控制

对于含有界扰动的离散时间系统,将有界扰动变化范围分割成若干小区间,针对这些区间建立多个自适应模型,并针对每一个自适应模型建立相应的控制器.给定一个指标切换函数,基于多个自适应模型控制器和给定的指标切换函数构成多模型自适应控制器.可以证明多模型自适应控制器能够保证闭环系统是输入输出有界稳定的.仿真实例表明,当被控对象的有界扰动随时间变化的时候,采用单一模型自适应控制,系统输出很难跟踪设定值,而多模型自适应控制器却极大地改善了控制品质.     

基于多模型的非线性系统自适应最小方差控制

对于一类典型的离散时间非线性系统, 提出了一种基于多模型的自适应最小方差控制方法. 通过在平衡点附近建立线性模型, 用径向基函数神经元网络来补偿建模误差和未建模动态, 形成了非线性系统的多模型表示. 采用了具有积分性质的切换指标函数作为切换法则和最小方差的控制方法构成了多模型自适应控制器. 仿真实验的结果表明了这种方法的有效性.     

基于多模型混合最小方差控制的时变扰动控制系统性能评估

在实际工业过程中,控制系统经常会受到时变扰动的影响,致使针对单一扰动模型设计的最小方差控制准则不再适用于评估时变扰动控制系统的性能. 当多个扰动信号同时出现时,采用常规多模型切换方法会发生间歇切换进而产生较大的暂态误差,不能准确评估系统当前性能. 针对上述问题,本文提出了一种基于多模型混合最小方差控制准则的性能评估方法. 首先根据每个扰动模型分别制定最小方差控制器,组成多模型最小方差控制器,然后在每个时间点混合多模型最小方差控制器,并将在其作用下的输出方差作为最终的性能评估基准,该方法既 充分考虑到每个扰动的特性,又避免了常规多模型切换方法因间歇切换而产生的暂态误差对评估结果准确性带来的影响,实现了准确、可靠地评估时变扰动控制系统的性能. 通过仿真,验证了基于多模型混合最小方差控制准则的性能评估方法的有效性.     

含有界扰动系统的多模型自适应控制

对含有有界扰动和参数不确定性的离散时间被控对象建立多个辨识模型, 覆盖被控对象的参数不确定性. 给定指标切换函数, 构成多模型自适应控制器. 引入“局部化”技术, 在保持计算精度的同时, 提高了计算速度. 同时证明, 多模型自适应控制可以保证闭环系统输入输出稳定, 且保证对给定有界参考输入、被控对象输出可在一给定界范围内跟踪参考输入.     

具有未知负载扰动的水井钻机电液伺服系统无模型自适应控制

针对电液伺服系统在水井钻机推进工况下存在的参数不确定以及未知负载扰动突变等非线性因素,提出了基于径向基(RBF)神经网络扰动观测器的无模型自适应控制方法.首先,通过改进的无模型自适应控制动态线性化方法,将被控系统线性化为与输入输出相关的增量形式,并将未知负载扰动合并到一个非线性项中;然后,设计了径向基神经网络扰动观测器对含有未知负载扰动的非线性项进行估计,作为对未知扰动的补偿;最后,设计了时变参数估计律,通过在线调整伪偏导数,给出了电液伺服系统的控制更新律.仿真结果表明,所设计的控制器能够对未知负载扰动突变进行补偿,并能确保跟踪误差有界收敛.     

一类非仿射非线性离散系统的改进无模型自适应控制

针对一类更广泛的非仿射非线性离散系统,提出一种改进的无模型自适应控制算法。该算法基于非参数动态线性化方法,运用观测器的思想,实现带有扰动系统的实时动态线性化,进而将无模型自适应控制方法的应用推广到更广泛的非仿射非线性离散系统。同时,对推广后的改进无模型自适应控制方法进行理论上的证明,并通过仿真实例验证了所提出的改进无模型自适应控制方法的可行性和有效性。     

基于极大后验估计的自适应容积卡尔曼滤波器

针对标准的容积卡尔曼滤波器(CKF) 设计需要精确已知噪声先验统计知识的问题, 提出一种自适应CKF 算法. 该算法在滤波过程中, 利用Sage-Husa 极大后验估值器对噪声的统计特性进行在线估计和修正, 有效地提高了CKF 的估计精度和数值稳定性. 在某些情况下, 噪声协方差估计会出现异常现象使得滤波发散, 进而提出了相应的改进方法. 仿真结果表明了自适应CKF 算法的可行性和有效性, 且明显改善了标准CKF 算法的滤波效果.     

高阶不确定系统的线性串级自抗扰控制

自抗扰控制是我国著名学者韩京清原创的先进控制技术,本文针对自抗扰控制(ADRC)在高阶系统应用中控制器设计和参数整定问题,提出了串级自抗扰控制(CADRC). CADRC把高阶被控对象分解为含确定性部分和含总扰动的低阶部分的串联组合,采用由内环和外环组成的串级控制系统来完成控制.该CADRC方案的内环采用内模控制,外环采用经典ADRC.外环ADRC的被控对象是一个等效的低阶系统,可以采用带宽法进行整定,而内环的内模控制采用高阶低通滤波器进行回路成形设计和参数整定.仿真研究表明,所提出的方法是有效的,具有良好的工程应用前景.     

Position‐dependent disturbance rejection using spatial‐based adaptive feedback linearization repetitive control

In this paper, we propose a new design of spatial‐based repetitive control for a class of rotary motion systems operating at variable speeds. The open‐loop system in spatial domain is obtained by reformulating a nonlinear time‐invariant system with respect to angular displacement. A two‐degree‐of‐freedom control structure (comprising two control modules) is then proposed to robustly stabilize the open‐loop system and improve the tracking performance. The first control module applies adaptive feedback linearization with projected parametric update and concentrates on robust stabilization of the closed‐loop system. The second control module introduces a spatial‐based repetitive controller cascaded with a loop‐shaping filter, which not only further reduces the tracking error, but also improves parametric adaptation. The overall control system is robust to model uncertainties of the system and capable of rejecting position‐dependent disturbances under varying process speeds. Stability proof for the overall system is given. A design example with simulation is provided to demonstrate the applicability of the proposed design. Copyright © 2008 John Wiley & Sons, Ltd.     

Distributed adaptive Kalman filter based on variational Bayesian technique

In this paper, distributed Kalman filter design is studied for linear dynamics with unknown measurement noise variance, which modeled by Wishart distribution. To solve the problem in a multi-agent network, a distributed adaptive Kalman filter is proposed with the help of variational Bayesian, where the posterior distribution of joint state and noise variance is approximated by a free-form distribution. The convergence of the proposed algorithm is proved in two main steps: noise statistics is estimated, where each agent only use its local information in variational Bayesian expectation (VB-E) step, and state is estimated by a consensus algorithm in variational Bayesian maximum (VB-M) step. Finally, a distributed target tracking problem is investigated with simulations for illustration.     

基于反向预测卡尔曼滤波自适应算法研究

标准卡尔曼滤波算法对系统的数学模型和噪声统计特性进行了假设,当该假设与实际的模型不匹配时容易造成滤波误差较大甚至滤波发散。提出基于反向预测卡尔曼滤波自适应算法,通过比较原始预测状态归一化新息平方和反向预测状态归一化新息平方,当比值大于设定阈值时在线进行过程噪声调整,从而修正预测状态。雷达目标跟踪仿真研究结果表明,该算法对目标机动和过程噪声增大有较强的自适应性,能够提高滤波精度和鲁棒性。     

水下机器人自适应卡尔曼滤波技术研究

水下机器人的位置和速度传感器受环境影响较大,数据滤波问题是运动控制的核心问题之一.给出了离散型卡尔曼滤波的基本方程,描述了卡尔曼滤波所具有的两个计算回路:增益计算回路和滤波计算回路.建立了水下机器人状态方程和量测方程,并在此基础上采用了自适应卡尔曼滤波方法对水下机器人的传感器数据进行了滤波分析.引入了渐消记忆指数加权方法.对时变噪声统计中,强调了新近数据的作用.避免了系统误差和量测误差统计特性的不准确对系统滤波效果的影响.滤波效果分析表明此方法能达到很好的滤波效果.     

Superheated steam temperature control based on modified active disturbance rejection control

Control of superheated steam temperature (SST) is becoming more and more challenging because of unknown disturbances caused by the frequent and extensive load changes and strict control requirements for the efficiency and safety. This is becoming even severe while the intermittent renewables penetration is growing. To this end, the working principle of SST is depicted and the models of SST are identified from the open-loop step response data. Considering the sluggish responses to the disturbances caused by high order dynamics, a modified active disturbance rejection control (ADRC) is proposed to enhance the control performance. Stability analysis of modified ADRC is derived theoretically to perfect the theory of modified ADRC. Then a practical tuning procedure is summarized for modified ADRC that can be readily understood by field engineers even though it involves trial and error tests. A simulation example shows that modified ADRC can improve the performance of tracking and disturbance rejection simultaneously while maintain a good robustness. A modified ADRC based cascade control strategy is proposed for the SST control system and the control performance is initially confirmed by a simulation based on the identified models. A field application in a 300 MW circulating fluidized bed (CFB) power plant demonstrates the advantages of the proposed strategy, which shows the temperature deviation can be significantly reduced in both the small-scale load varying condition and the large-scale load varying condition. The successful application of the proposed SST control system indicates a promising future of modified ADRC in power industry with the increasing demand on integrating more renewables into the power grid.     

Active disturbance rejection control: Applications in aerospace

Control of uncertain dynamical systems has been an area of active research for the past several decades and to this end,various robust control approaches have been proposed in the literature. The active disturbance rejection control (ADRC) representsone prominent approach that has been widely studied and applied for designing robust controllers in diverse areas of engineeringapplications. In this work, a brief review of the approach and some of its applications in aerospace are discussed. The resultsshow that the approach possesses immense potential to offer viable solution to reallife aerospace problems.     

基于卡尔曼滤波的四旋翼飞行器姿态估计和控制算法研究

四旋翼飞行器作为无人机的一种,由于其简单气动布局和复杂的动力学模型,在控制领域获得了越来越多的学术关注;本文首先分析了微机电系统惯性测量单元(MEMS IMU)传感器的误差,给出了基于自回归(autoregressive,AR)噪声模型的卡尔曼滤波算法设计;然后根据加速度计和陀螺仪长短周期测量的不同特性,进一步对姿态数据做互补融合,实验表明此算法可以实现良好的滤波效果;基于上面的姿态估计,本文又提出了一种双增益的PD控制算法对飞行器进行姿态控制;最后将姿态估计算法和控制算法应用到实验平台中,可以实现四旋翼在支架上的自主悬停等功能.     

Nonlinear tracking and input disturbance rejection with application to pH control

This paper presents a nonlinear observer-based controller configuration for a class of nonlinear single-input single-output systems with certain observability and stability properties. Particular attention is paid to the effect of input disturbances typically present in chemical processes. It is pointed out that conventional feedback linearizing internal model controllers reject output disturbances linearly, but that they can experience significant performance degradation in the presence of input disturbances. This problem is shown to originate in the lack of the linear superposition property. It is proven that the proposed control architecture rejects constant input disturbances from the control signal and then recovers linear reference tracking. The convenient tuning and improved performance are illustrated for pH neutralization.